G2Cdb::Gene report

Gene id
G00002108
Gene symbol
APP (HGNC)
Species
Homo sapiens
Description
amyloid beta (A4) precursor protein
Orthologue
G00000859 (Mus musculus)

Databases (8)

Gene
ENSG00000142192 (Ensembl human gene)
351 (Entrez Gene)
195 (G2Cdb plasticity & disease)
APP (GeneCards)
Literature
104760 (OMIM)
Marker Symbol
HGNC:620 (HGNC)
Protein Expression
157 (human protein atlas)
Protein Sequence
P05067 (UniProt)

Literature (938)

Pubmed - other

  • Genetic screening of Alzheimer's disease genes in Iberian and African samples yields novel mutations in presenilins and APP.

    Guerreiro RJ, Baquero M, Blesa R, Boada M, Brás JM, Bullido MJ, Calado A, Crook R, Ferreira C, Frank A, Gómez-Isla T, Hernández I, Lleó A, Machado A, Martínez-Lage P, Masdeu J, Molina-Porcel L, Molinuevo JL, Pastor P, Pérez-Tur J, Relvas R, Oliveira CR, Ribeiro MH, Rogaeva E, Sa A, Samaranch L, Sánchez-Valle R, Santana I, Tàrraga L, Valdivieso F, Singleton A, Hardy J and Clarimón J

    Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA.

    Mutations in three genes (PSEN1, PSEN2, and APP) have been identified in patients with early-onset (<65 years) Alzheimer's disease (AD). We performed a screening for mutations in the coding regions of presenilins, as well as exons 16 and 17 of the APP gene in a total of 231 patients from the Iberian peninsular with a clinical diagnosis of early-onset AD (mean age at onset of 52.9 years; range 31-64). We found three novel mutations in PSEN1, one novel mutation in PSEN2, and a novel mutation in the APP gene. Four previously described mutations in PSEN1 were also found. The same analysis was carried in 121 elderly healthy controls from the Iberian peninsular, and a set of 130 individuals from seven African populations belonging to the Centre d'Etude du Polymorphisme Humain-Human Genome Diversity Panel (CEPH-HGDP), in order to determine the extent of normal variability in these genes. Interestingly, in the latter series, we found five new non-synonymous changes in all three genes and a presenilin 2 variant (R62H) that has been previously related to AD. In some of these mutations, the pathologic consequence is uncertain and needs further investigation. To address this question we propose and use a systematic algorithm to classify the putative pathology of AD mutations.

    Funded by: Canadian Institutes of Health Research; NIA NIH HHS: Z01 AG000951-06

    Neurobiology of aging 2010;31;5;725-31

  • An APP inhibitory domain containing the Flemish mutation residue modulates gamma-secretase activity for Abeta production.

    Tian Y, Bassit B, Chau D and Li YM

    Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, New York, USA.

    Gamma-secretase is an aspartyl protease that cleaves multiple substrates within their transmembrane domains. Gamma-secretase processes the amyloid precursor protein (APP) to generate gamma-amyloid (Agamma) peptides associated with Alzheimer's disease. Here, we show that APP possesses a substrate inhibitory domain (ASID) that negatively modulates gamma-secretase activity for Agamma production by binding to an allosteric site within the gamma-secretase complex. Alteration of this ASID by deletion or mutation, as is seen with the Flemish mutation (A21G), reduces its inhibitory potency and promotes Agamma production. Notably, peptides derived from ASID show selective inhibition of gamma-secretase activity for Agamma production over Notch1 processing. Therefore, this mode of regulation represents an unprecedented mechanism for modulating gamma-secretase, providing insight into the molecular basis of Alzheimer's disease pathogenesis and a potential strategy for the development of therapeutics.

    Funded by: NIA NIH HHS: AG026660

    Nature structural & molecular biology 2010;17;2;151-8

  • Slowing of EEG correlates with CSF biomarkers and reduced cognitive speed in elderly with normal cognition over 4 years.

    Stomrud E, Hansson O, Minthon L, Blennow K, Rosén I and Londos E

    Clinical Memory Research Unit, Department of Clinical Sciences Malmö, Lund University, S-205 02 Malmö, Sweden. erik.stomrud@med.lu.se

    Background: Cerebrospinal fluid (CSF) biomarkers and quantitative EEG show particular patterns of change in Alzheimer's disease (AD) and reflect neuropathologic processes and cerebral function, respectively. The changes precede cognitive decline and should be visible already in preclinical stages. We therefore aimed to investigate their relationship in cognitively healthy individuals.

    Method: Thirty-three (33) elderly individuals with repeated normal scores on cognitive tests over 4.5 years underwent EEG recording with quantitative frequency analysis and analysis of CSF total tau (T-tau), phosphorylated tau (P-tau) and beta-amyloid(1-42) (Abeta42).

    Results: CSF T-tau and P-tau correlated with relative EEG theta power (r(s)>0.545; p<0.01), but not with relative alpha, beta or delta power. The combined P-tau/Abeta42 ratio exhibited an even stronger correlation with relative theta power (r(s)=0.622; p<0.001), especially in the right posterior quadrant of the head (r(s)=0.643; p<10(-4)). Slowing of cognitive speed correlated with increased relative theta power, foremost in the posterior quadrants (r(s)>0.503; p<0.01), and high P-tau/Abeta42 ratio (r(s)>0.462; p<0.01).

    Conclusions: Our results suggest that already in cognitively healthy elderly subjects, biochemical changes in CSF, and the possible underlying neuropathologic processes it reflects, have an effect on cerebral function as visualized by the EEG rhythm and cognitive speed. It hereby suggests that CSF biomarkers and EEG theta activity might indicate early abnormal degenerative changes in the brain.

    Neurobiology of aging 2010;31;2;215-23

  • The common architecture of cross-beta amyloid.

    Jahn TR, Makin OS, Morris KL, Marshall KE, Tian P, Sikorski P and Serpell LC

    Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

    Amyloid fibril deposition is central to the pathology of more than 30 unrelated diseases including Alzheimer's disease and Type 2 diabetes. It is generally accepted that amyloid fibrils share common structural features despite each disease being characterised by the deposition of an unrelated protein or peptide. The structure of amyloid fibrils has been studied using X-ray fibre diffraction and crystallography, solid-state NMR and electron paramagnetic resonance, and many different, sometimes opposing, models have been suggested. Many of these models are based on the original interpretation of the cross-beta diffraction pattern for cross-beta silk in which beta-strands run perpendicular to the fibre axis, although alternative models include beta-helices and natively structured proteins. Here, we have analysed opposing model structures and examined the necessary structural elements within the amyloid core structure, as well as producing idealised models to test the limits of the core conformation. Our work supports the view that amyloid fibrils share a number of common structural features, resulting in characteristic diffraction patterns. This pattern may be satisfied by structures in which the strands align close to perpendicular to the fibre axis and are regularly arranged to form beta-sheet ribbons. Furthermore, the fibril structure contains several beta-sheets that associate via side-chain packing to form the final protofilament structure.

    Funded by: Biotechnology and Biological Sciences Research Council; Medical Research Council; Wellcome Trust

    Journal of molecular biology 2010;395;4;717-27

  • Interaction between oligomers of stefin B and amyloid-beta in vitro and in cells.

    Skerget K, Taler-Vercic A, Bavdek A, Hodnik V, Ceru S, Tusek-Znidaric M, Kumm T, Pitsi D, Pompe-Novak M, Palumaa P, Soriano S, Kopitar-Jerala N, Turk V, Anderluh G and Zerovnik E

    Department of Biochemistry, Molecular and Structural Biology, JoZef Stefan Institute, Jamova 39, Slovenia.

    To contribute to the question of the putative role of cystatins in Alzheimer disease and in neuroprotection in general, we studied the interaction between human stefin B (cystatin B) and amyloid-beta-(1-40) peptide (Abeta). Using surface plasmon resonance and electrospray mass spectrometry we were able to show a direct interaction between the two proteins. As an interesting new fact, we show that stefin B binding to Abeta is oligomer specific. The dimers and tetramers of stefin B, which bind Abeta, are domain-swapped as judged from structural studies. Consistent with the binding results, the same oligomers of stefin B inhibit Abeta fibril formation. When expressed in cultured cells, stefin B co-localizes with Abeta intracellular inclusions. It also co-immunoprecipitates with the APP fragment containing the Abeta epitope. Thus, stefin B is another APP/Abeta-binding protein in vitro and likely in cells.

    The Journal of biological chemistry 2010;285;5;3201-10

  • Alzheimer's-related endosome dysfunction in Down syndrome is Abeta-independent but requires APP and is reversed by BACE-1 inhibition.

    Jiang Y, Mullaney KA, Peterhoff CM, Che S, Schmidt SD, Boyer-Boiteau A, Ginsberg SD, Cataldo AM, Mathews PM and Nixon RA

    Center for Dementia Research, Nathan Kline Institute, Orangeburg, NY 10962, USA.

    An additional copy of the beta-amyloid precursor protein (APP) gene causes early-onset Alzheimer's disease (AD) in trisomy 21 (DS). Endosome dysfunction develops very early in DS and AD and has been implicated in the mechanism of neurodegeneration. Here, we show that morphological and functional endocytic abnormalities in fibroblasts from individuals with DS are reversed by lowering the expression of APP or beta-APP-cleaving enzyme 1 (BACE-1) using short hairpin RNA constructs. By contrast, endosomal pathology can be induced in normal disomic (2N) fibroblasts by overexpressing APP or the C-terminal APP fragment generated by BACE-1 (betaCTF), all of which elevate the levels of betaCTFs. Expression of a mutant form of APP that cannot undergo beta-cleavage had no effect on endosomes. Pharmacological inhibition of APP gamma-secretase, which markedly reduced Abeta production but raised betaCTF levels, also induced AD-like endosome dysfunction in 2N fibroblasts and worsened this pathology in DS fibroblasts. These findings strongly implicate APP and the betaCTF of APP, and exclude Abeta and the alphaCTF, as the cause of endocytic pathway dysfunction in DS and AD, underscoring the potential multifaceted value of BACE-1 inhibition in AD therapeutics.

    Funded by: NIA NIH HHS: AG017617

    Proceedings of the National Academy of Sciences of the United States of America 2010;107;4;1630-5

  • Beta-amyloid causes depletion of synaptic vesicles leading to neurotransmission failure.

    Parodi J, Sepúlveda FJ, Roa J, Opazo C, Inestrosa NC and Aguayo LG

    Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Edmundo Larenas S/N, P.O. Box 160-C, Concepción, Chile.

    Alzheimer disease is a progressive neurodegenerative brain disorder that leads to major debilitating cognitive deficits. It is believed that the alterations capable of causing brain circuitry dysfunctions have a slow onset and that the full blown disease may take several years to develop. Therefore, it is important to understand the early, asymptomatic, and possible reversible states of the disease with the aim of proposing preventive and disease-modifying therapeutic strategies. It is largely unknown how amyloid beta-peptide (A beta), a principal agent in Alzheimer disease, affects synapses in brain neurons. In this study, we found that similar to other pore-forming neurotoxins, A beta induced a rapid increase in intracellular calcium and miniature currents, indicating an enhancement in vesicular transmitter release. Significantly, blockade of these effects by low extracellular calcium and a peptide known to act as an inhibitor of the A beta-induced pore prevented the delayed failure, indicating that A beta blocks neurotransmission by causing vesicular depletion. This new mechanism for A beta synaptic toxicity should provide an alternative pathway to search for small molecules that can antagonize these effects of A beta.

    The Journal of biological chemistry 2010;285;4;2506-14

  • The amyloid precursor protein/protease nexin 2 Kunitz inhibitor domain is a highly specific substrate of mesotrypsin.

    Salameh MA, Robinson JL, Navaneetham D, Sinha D, Madden BJ, Walsh PN and Radisky ES

    Department of Cancer Biology, Mayo Clinic Cancer Center, Jacksonville, Florida 32224, USA.

    The amyloid precursor protein (APP) is a ubiquitously expressed transmembrane adhesion protein and the progenitor of amyloid-beta peptides. The major splice isoforms of APP expressed by most tissues contain a Kunitz protease inhibitor domain; secreted APP containing this domain is also known as protease nexin 2 and potently inhibits serine proteases, including trypsin and coagulation factors. The atypical human trypsin isoform mesotrypsin is resistant to inhibition by most protein protease inhibitors and cleaves some inhibitors at a substantially accelerated rate. Here, in a proteomic screen to identify potential physiological substrates of mesotrypsin, we find that APP/protease nexin 2 is selectively cleaved by mesotrypsin within the Kunitz protease inhibitor domain. In studies employing the recombinant Kunitz domain of APP (APPI), we show that mesotrypsin cleaves selectively at the Arg(15)-Ala(16) reactive site bond, with kinetic constants approaching those of other proteases toward highly specific protein substrates. Finally, we show that cleavage of APPI compromises its inhibition of other serine proteases, including cationic trypsin and factor XIa, by 2 orders of magnitude. Because APP/protease nexin 2 and mesotrypsin are coexpressed in a number of tissues, we suggest that processing by mesotrypsin may ablate the protease inhibitory function of APP/protease nexin 2 in vivo and may also modulate other activities of APP/protease nexin 2 that involve the Kunitz domain.

    Funded by: NCI NIH HHS: P50 CA091956-08; NHLBI NIH HHS: HL46213, HL74124

    The Journal of biological chemistry 2010;285;3;1939-49

  • Estrogen stimulates degradation of beta-amyloid peptide by up-regulating neprilysin.

    Liang K, Yang L, Yin C, Xiao Z, Zhang J, Liu Y and Huang J

    State Key Lab of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China.

    Postmenopausal estrogen depletion is a characterized risk factor for Alzheimer disease (AD), a human disorder linked to high levels of beta-amyloid peptide (Abeta) in brain tissue. Previous studies suggest that estrogen negatively regulates the level of Abeta in the brain, but the molecular mechanism is unknown. Here, we provide evidence that estrogen promotes Abeta degradation mainly through a principal Abeta degrading enzyme, neprilysin, in neuroblastoma SH-SY5Y cells. We also demonstrate that up-regulation of neprilysin by estrogen is dependent on both estrogen receptor alpha and beta (ERalpha and ERbeta), and ligand-activated ER regulates expression of neprilysin through physical interactions between ER and estrogen response elements (EREs) identified in the neprilysin gene. These results were confirmed by in vitro gel shift and in vivo chromatin immunoprecipitation analyses, which demonstrate specific binding of ERalpha and ERbeta to two putative EREs in the neprilysin gene. The EREs also enhance ERalpha- and ERbeta-dependent reporter gene expression in a yeast model system. Therefore, the study described here provides a putative mechanism by which estrogen positively regulates expression of neprilysin to promote degradation of Abeta, reducing risk for AD. These results may lead to novel approaches to prevent or treat AD.

    The Journal of biological chemistry 2010;285;2;935-42

  • The effects of parkin suppression on the behaviour, amyloid processing, and cell survival in APP mutant transgenic mice.

    Perucho J, Casarejos MJ, Rubio I, Rodriguez-Navarro JA, Gómez A, Ampuero I, Rodal I, Solano RM, Carro E, García de Yébenes J and Mena MA

    Department of Neurobiology, Hospital Ramón y Cajal, Madrid, Spain.

    Parkin suppression induces accumulation of beta-amyloid in mutant tau mice. We studied the effect of parkin suppression on behaviour and brain pathology in APP(swe) mutant mice. We produced double mutant mice with human mutated APP(swe)+partial (hemizygote) or total (homozygote) deletion of Park-2 gene. We studied the development, behaviour, brain histology, and biochemistry of 12- and 16-month-old animals in 6 groups of mice, with identical genetic background: wild-type (WT), APP(swe) overexpressing (APP), hemizygote and homozygote deletion of Park-2 (PK(+/-) and PK(-/-), respectively), and double mutants (APP/PK(+/-) and APP/PK(-/-)). APP mice have reduced weight gain, decreased motor activity, and reduced number of entrances and of arm alternation in the Y-maze, abnormalities which were partially or completely normalized in APP/PK(+/-) and APP/PK(-/-) mice. The double mutants had similar number of mutant human APP transgene copies than the APP and levels of 40 and 80 kDa proteins; but both of them, APP/PK(+/-) and APP/PK(-/-) mice, had less plaques in cortex and hippocampus than the APP mice. APP mutant mice had increased apoptosis, proapoptotic Bax/Bcl2 ratios, and gliosis, but these death-promoting factors were normalized in APP/PK(+/-) and APP/PK(-/-) mice. APP mutant mice had an increased number of tau immunoreactive neuritic plaques in the cerebral cortex as well as increased levels of total and phosphorylated tau protein, and these changes were partially normalized in APP/PK(+/-) heterozygotic and homozygotic APP/PK(-/-) mice. Compensatory protein-degrading systems such as HSP70, CHIP, and macroautophagy were increased in APP/PK(+/-) and APP/PK(-/-). Furthermore, the chymotrypsin- and trypsin-like proteasome activities, decreased in APP mice in comparison with WT, were normalized in the APP/PK(-/-) mice. We proposed that partial and total suppression of parkin triggers compensatory mechanisms, such as chaperone overexpression and increased autophagy, which improved the behavioural and cellular phenotype of APP(swe) mice.

    Experimental neurology 2010;221;1;54-67

  • A fragment of the scaffolding protein RanBP9 is increased in Alzheimer's disease brains and strongly potentiates amyloid-beta peptide generation.

    Lakshmana MK, Chung JY, Wickramarachchi S, Tak E, Bianchi E, Koo EH and Kang DE

    Department of Neurosciences, University of California-San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA.

    Increasing biochemical and genetic evidence indicates that the amyloid-beta (Abeta) peptide derived from amyloid precursor protein (APP) plays a central role in Alzheimer's disease (AD) pathogenesis. We previously reported that RanBP9 promotes Abeta generation by scaffolding APP/BACE1/LRP complexes together. Interestingly, the RanBP9-Delta1/N60 (residues 1-392) deletion mutant interacted much more strongly with APP/BACE1/LRP than full-length RanBP9. In this study, we found that RanBP9-N60, a processed form of RanBP9 virtually identical to the RanBP9-Delta1/N60 mutant, was strongly increased in AD brains compared with controls. To evaluate the potential pathogenic consequences of this phenotype, we studied the differential biological properties of full-length RanBP9 vs. RanBP9-Delta1/N60 in HEK293T and Neuro-2A cells. The RanBP9-Delta1/N60 fragment, which lacks a nuclear localization signal, displayed enhanced cytoplasmic vs. nuclear localization and >3-fold enhanced stability than full-length RanBP9. Importantly, RanBP9-Delta1/N60, which contains the LisH dimerization domain, retained the capacity to form self-interacting multimeric complexes and increased Abeta generation by approximately 5-fold over vector controls, more potent than the approximately 3-fold increase seen by full-length RanBP9. Taken together, these data indicate that RanBP9-N60 may further drive the amyloid cascade in AD and that the proteolytic processing of RanBP9 may be an attractive therapeutic target.

    Funded by: NIA NIH HHS: AG 005131-24S1, P50 AG005131

    FASEB journal : official publication of the Federation of American Societies for Experimental Biology 2010;24;1;119-27

  • Alzheimer's beta-amyloid peptide blocks vascular endothelial growth factor mediated signaling via direct interaction with VEGFR-2.

    Patel NS, Mathura VS, Bachmeier C, Beaulieu-Abdelahad D, Laporte V, Weeks O, Mullan M and Paris D

    Roskamp Institute, Sarasota, Florida, USA. npatel@scripps.edu

    Beta-amyloid peptides (Abeta) are the major constituents of senile plaques and cerebrovascular deposits in the brains of Alzheimer's disease patients. We have shown previously that soluble forms of Abeta are anti-angiogenic both in vitro and in vivo. However, the mechanism of the anti-angiogenic activity of Abeta peptides is unclear. In this study, we examined the effects of Abeta1-42 on vascular endothelial growth factor receptor 2 (VEGFR-2) signaling, which plays a key role in angiogenesis. Abeta inhibited VEGF-induced migration of endothelial cells, as well as VEGF-induced permeability of an in vitro model of the blood brain barrier. Consistently, exogenous VEGF dose-dependently antagonized the anti-angiogenic activity of Abeta in a capillary network assay. Abeta1-42 also blocked VEGF-induced tyrosine phosphorylation of VEGFR-2 in two types of primary endothelial cells, suggesting an antagonistic action of Abeta toward VEGFR-2 signaling in cells. Moreover, Abeta was able to directly interact with the extracellular domain of VEGFR-2 and to compete with the binding of VEGF to its receptor in a cell-free assay. Co-immunoprecipitation experiments confirmed that Abeta can bind VEGFR-2 both in vitro and in vivo. Altogether, our data suggest that Abeta acts as an antagonist of VEGFR-2 and provide a mechanism explaining the anti-angiogenic activity of Abeta peptides.

    Funded by: PHS HHS: R01A619250

    Journal of neurochemistry 2010;112;1;66-76

  • Clinical, neuropathologic, and biochemical profile of the amyloid precursor protein I716F mutation.

    Guardia-Laguarta C, Pera M, Clarimón J, Molinuevo JL, Sánchez-Valle R, Lladó A, Coma M, Gómez-Isla T, Blesa R, Ferrer I and Lleó A

    Neurology Department, Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona, Spain.

    We report the clinical, pathologic, and biochemical characteristics of the recently described amyloid precursor protein (APP) I716F mutation. We present the clinical findings of individuals carrying the APP I716F mutation and the neuropathologic examination of the proband. The mutation was found in a patient with Alzheimer disease with onset at the age of 31 years and death at age 36 years and who had a positive family history of early-onset Alzheimer disease. Neuropathologic examination showed abundant diffuse amyloid plaques mainly composed of amyloid-beta42 and widespread neurofibrillary pathology. Lewy bodies were found in the amygdala. Chinese hamster ovary cells transfected with this mutation showed a marked increase in the amyloid-beta42/40 ratio and APP C-terminal fragments and a decrease in APP intracellular domain production, suggesting reduced APP proteolysis by gamma-secretase. Taken together, these findings indicate that the APP I716F mutation is associated with the youngest age of onset for this locus and strengthen the inverse association between amyloid-beta42/40 ratio and age of onset. The mutation leads to a protein that is poorly processed by gamma-secretase. This loss of function may be an additional mechanism by which some mutations around the gamma-secretase cleavage site lead to familial Alzheimer disease.

    Journal of neuropathology and experimental neurology 2010;69;1;53-9

  • Differential activation of mitochondrial apoptotic pathways by vasculotropic amyloid-beta variants in cells composing the cerebral vessel walls.

    Fossati S, Cam J, Meyerson J, Mezhericher E, Romero IA, Couraud PO, Weksler BB, Ghiso J and Rostagno A

    Department of Pathology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA.

    Cerebral amyloid angiopathy (CAA) is an age-associated condition and a common finding in Alzheimer's disease in which amyloid-beta (Abeta) vascular deposits are featured in >80% of the cases. Familial Abeta variants bearing substitutions at positions 21-23 are primarily associated with CAA, although they manifest with strikingly different clinical phenotypes: cerebral hemorrhage or dementia. The recently reported Piedmont L34V Abeta mutant, located outside the hot spot 21-23, shows a similar hemorrhagic phenotype, albeit less aggressive than the widely studied Dutch E22Q variant. We monitored the apoptotic events occurring after stimulation of human brain microvascular endothelial and smooth muscle cells with nonfibrillar structures of both variants and wild-type Abeta40. Induction of analogous caspase-mediated mitochondrial pathways was elicited by all peptides, although within different time frames and intensity. Activated pathways were susceptible to pharmacological modulation either through direct inhibition of mitochondrial cytochrome c release or by the action of pan- and pathway-specific caspase inhibitors, giving a clear indication of the independent or synergistic engagement of both extrinsic and intrinsic mechanisms. Structural analyses of the Abeta peptides showed that apoptosis preceded fibril formation, correlating with the presence of oligomers and/or protofibrils. The data support the notion that rare genetic mutations constitute unique paradigms to understand the molecular pathogenesis of CAA.

    Funded by: NIA NIH HHS: AG-30539; NINDS NIH HHS: NS-051715

    FASEB journal : official publication of the Federation of American Societies for Experimental Biology 2010;24;1;229-41

  • Protective effect of N-glycan bisecting GlcNAc residues on beta-amyloid production in Alzheimer's disease.

    Akasaka-Manya K, Manya H, Sakurai Y, Wojczyk BS, Kozutsumi Y, Saito Y, Taniguchi N, Murayama S, Spitalnik SL and Endo T

    Department of Glycobiology, Tokyo Metropolitan Institute of Gerontology, Foundation for Research on Aging and Promotion of Human Welfare, Itabashi-ku, Tokyo 173-0015, Japan.

    Alteration of glycoprotein glycans often changes various properties of the target glycoprotein and contributes to a wide variety of diseases. Here, we focused on the N-glycans of amyloid precursor protein whose cleaved fragment, beta-amyloid, is thought to cause much of the pathology of Alzheimer's disease (AD). We previously determined the N-glycan structures of normal and mutant amyloid precursor proteins (the Swedish type and the London type). In comparison with normal amyloid precursor protein, mutant amyloid precursor proteins had higher contents of bisecting GlcNAc residues. Because N-acetylglucosaminyltransferase III (GnT-III) is the glycosyltransferase responsible for synthesizing a bisecting GlcNAc residue, the current report measured GnT-III mRNA expression levels in the brains of AD patients. Interestingly, GnT-III mRNA expression was increased in AD brains. Furthermore, beta-amyloid treatment increased GnT-III mRNA expression in Neuro2a mouse neuroblastoma cells. We then examined the influence of bisecting GlcNAc on the production of beta-amyloid. Both beta-amyloid 40 and beta-amyloid 42 were significantly decreased in GnT-III-transfected cells. When secretase activities were analyzed in GnT-III transfectant cells, alpha-secretase activity was increased. Taken together, these results suggest that upregulation of GnT-III in AD brains may represent an adaptive response to protect them from additional beta-amyloid production.

    Glycobiology 2010;20;1;99-106

  • Novel mediators of amyloid precursor protein signaling.

    Swistowski A, Zhang Q, Orcholski ME, Crippen D, Vitelli C, Kurakin A and Bredesen DE

    Buck Institute for Age Research, Novato, California 94945, USA.

    Multiple recent reports implicate amyloid precursor protein (APP) signaling in the pathogenesis of Alzheimer's disease, but the APP-dependent signaling network involved has not been defined. Here, we report a novel consensus sequence for interaction with the PDZ-1 and PDZ-2 domains of the APP-interacting proteins Mint1, Mint2, and Mint3 (X11alpha, X11beta, and X11gamma), and multiple novel interactors for these proteins, with the finding that transcriptional coactivators are highly represented among these interactors. Furthermore, we show that Mint3 interaction with a set of the transcriptional coactivators leads to nuclear localization and transactivation, whereas interaction of the same set with Mint1 or Mint2 prevents nuclear localization and transactivation. These results define new mediators of the signal transduction network mediated by APP.

    Funded by: NIA NIH HHS: AG031380, R21 AG031380, R21 AG031380-01, R21 AG031380-02; NINDS NIH HHS: NS45093, R01 NS045093, R01 NS045093-01, R01 NS045093-02, R01 NS045093-03, R01 NS045093-04, R01 NS045093-05

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;50;15703-12

  • Biophysical analyses of synthetic amyloid-beta(1-42) aggregates before and after covalent cross-linking. Implications for deducing the structure of endogenous amyloid-beta oligomers.

    Moore BD, Rangachari V, Tay WM, Milkovic NM and Rosenberry TL

    Department of Neuroscience, Mayo Clinic College of Medicine, 4500 San Pablo Road, Jacksonville, Florida 32224, USA.

    A neuropathological hallmark of Alzheimer's disease (AD) is the presence of large numbers of senile plaques in the brain. These deposits are rich in fibrils that are composed of 40- and 42-residue amyloid-beta (Abeta) peptides. Several lines of evidence indicate that soluble Abeta aggregates as well as fibrils are important in the etiology of AD. Low levels of endogenous soluble Abeta aggregates make them difficult to characterize, but several species in extracts of AD brains have been detected by gel electrophoresis in sodium dodecyl sulfate (SDS) and immunoblotting. Individual Abeta oligomers ranging in size from dimers through dodecamers of 4 kDa monomeric Abeta have been resolved in other laboratories as discrete species by size exclusion chromatography (SEC). In an effort to reconstitute soluble Abeta aggregates in vitro that resemble the endogenous soluble Abeta aggregates, we previously found that monomeric Abeta(1-42) rapidly forms soluble oligomers in the presence of dilute SDS micelles. Here we extend this work in two directions. First, we contrast the size and secondary structure of these oligomers with those of synthetic Abeta(1-42) fibrils. SEC and multiangle light scattering were used to obtain a molecular mass of 150 kDa for the isolated oligomers. The oligomers partially dissociated to monomers through nonamers when incubated with SDS, but in contrast to endogenous oligomers, we saw no evidence of these discrete species prior to SDS treatment. One hypothesis to explain this difference is that endogenous oligomers are stabilized by covalent cross-linking induced by unknown cellular agents. To explore this hypothesis, optimal mass spectrometry (MS) analysis procedures need to be developed for Abeta cross-linked in vitro. In our second series of studies, we began this process by treating monomeric and aggregated Abeta(1-42) with three cross-linking agents: transglutaminase, glutaraldehyde, and Cu(II) with peroxide. We compared the efficiency of covalent cross-linking with these agents, the effect of cross-linking on peptide secondary structure, the stability of the cross-linked structures to thermal unfolding, and the sites of peptide cross-linking obtained from proteolysis and MS.

    Biochemistry 2009;48;49;11796-806

  • Fibril fragmentation enhances amyloid cytotoxicity.

    Xue WF, Hellewell AL, Gosal WS, Homans SW, Hewitt EW and Radford SE

    Astbury Centre for Structural Molecular Biology, Institute of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.

    Fibrils associated with amyloid disease are molecular assemblies of key biological importance, yet how cells respond to the presence of amyloid remains unclear. Cellular responses may not only depend on the chemical composition or molecular properties of the amyloid fibrils, but their physical attributes such as length, width, or surface area may also play important roles. Here, we report a systematic investigation of the effect of fragmentation on the structural and biological properties of amyloid fibrils. In addition to the expected relationship between fragmentation and the ability to seed, we show a striking finding that fibril length correlates with the ability to disrupt membranes and to reduce cell viability. Thus, despite otherwise unchanged molecular architecture, shorter fibrillar samples show enhanced cytotoxic potential than their longer counterparts. The results highlight the importance of fibril length in amyloid disease, with fragmentation not only providing a mechanism by which fibril load can be rapidly increased but also creating fibrillar species of different dimensions that can endow new or enhanced biological properties such as amyloid cytotoxicity.

    Funded by: Biotechnology and Biological Sciences Research Council: BB/526502/1; Wellcome Trust: 075675

    The Journal of biological chemistry 2009;284;49;34272-82

  • [Genetics of dementias, Part 4: a spectrum of mutations responsible for the familial autosomal dominant form of Alzheimer's disease].

    Kowalska A

    Instytut Genetyki Człowieka PAN w Poznaniu.

    Fifty years ago it was demonstrated that some patients with Alzheimer's disease (AD) had an autosomal dominant Mendelian pattern of disease inheritance. Familial and early-onset cases (familial Alzheimer's disease, FAD) are rather rare and account for only a few percent of the total population of patients. Mutations of the genes for amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) are responsible for development of the disease in 50 percent of patients with FAD. The identification of mutations in FAD genes leads to a better understand of the molecular basis of the cellular pathways leading to neurodegeneration. With the detection of genetic defects responsible for FAD, there is considerable interest in the application of this genetic information in medical practice through genetic testing and counseling for families with Alzheimer's disease.

    Postepy higieny i medycyny doswiadczalnej (Online) 2009;63;583-91

  • X11beta rescues memory and long-term potentiation deficits in Alzheimer's disease APPswe Tg2576 mice.

    Mitchell JC, Ariff BB, Yates DM, Lau KF, Perkinton MS, Rogelj B, Stephenson JD, Miller CC and McLoughlin DM

    MRC Centre for Neurodegeneration Research, King's College London, Institute of Psychiatry, London SE5 8AF, UK.

    Increased production and deposition of amyloid beta-protein (Abeta) are believed to be key pathogenic events in Alzheimer's disease. As such, routes for lowering cerebral Abeta levels represent potential therapeutic targets for Alzheimer's disease. X11beta is a neuronal adaptor protein that binds to the intracellular domain of the amyloid precursor protein (APP). Overexpression of X11beta inhibits Abeta production in a number of experimental systems. However, whether these changes to APP processing and Abeta production induced by X11beta overexpression also induce beneficial effects to memory and synaptic plasticity are not known. We report here that X11beta-mediated reduction in cerebral Abeta is associated with normalization of both cognition and in vivo long-term potentiation in aged APPswe Tg2576 transgenic mice that model the amyloid pathology of Alzheimer's disease. Overexpression of X11beta itself has no detectable adverse effects upon mouse behaviour. These findings support the notion that modulation of X11beta function represents a therapeutic target for Abeta-mediated neuronal dysfunction in Alzheimer's disease.

    Funded by: Medical Research Council; Wellcome Trust

    Human molecular genetics 2009;18;23;4492-500

  • Beta-amyloid deposition and the aging brain.

    Rodrigue KM, Kennedy KM and Park DC

    Center for BrainHealth, School of Behavioral and Brain Sciences, The University of Texas at Dallas, 2200 W. Mockingbird Ln, Dallas, TX 75235, USA.

    A central issue in cognitive neuroscience of aging research is pinpointing precise neural mechanisms that determine cognitive outcome in late adulthood as well as identifying early markers of less successful cognitive aging. One promising biomarker is beta amyloid (Abeta) deposition. Several new radiotracers have been developed that bind to fibrillar Abeta providing sensitive estimates of amyloid deposition in various brain regions. Abeta imaging has been primarily used to study patients with Alzheimer's Disease (AD) and individuals with Mild Cognitive Impairment (MCI); however, there is now building data on Abeta deposition in healthy controls that suggest at least 20% and perhaps as much as a third of healthy older adults show significant deposition. Considerable evidence suggests amyloid deposition precedes declines in cognition and may be the initiator in a cascade of events that indirectly leads to age-related cognitive decline. We review studies of Abeta deposition imaging in AD, MCI, and normal adults, its cognitive consequences, and the role of genetic risk and cognitive reserve.

    Funded by: NIA NIH HHS: AG-006265-23, R37 AG006265, R37 AG006265-25

    Neuropsychology review 2009;19;4;436-50

  • Cognitive decline and brain volume loss as signatures of cerebral amyloid-beta peptide deposition identified with Pittsburgh compound B: cognitive decline associated with Abeta deposition.

    Storandt M, Mintun MA, Head D and Morris JC

    Department of Psychology, School of Arts and Sciences, Washington University, St Louis, Missouri 63108, USA.

    Objective: To examine the relation of amyloid-beta peptide (Abeta) levels in the cerebral cortex with structural brain integrity and cognitive performance in cognitively healthy older people.

    Design: Longitudinal study from May 22, 1985, through October 15, 2008.

    Setting: Washington University Alzheimer Disease Research Center.

    Participants: A total of 135 individuals aged 65 to 88 years with a Clinical Dementia Rating of 0.

    The relations between mean cortical carbon 11 ((11)C)-labeled Pittsburgh compound B (PiB) binding potential values, proportional to the density of fibrillar Abeta binding sites in the brain, concurrent regional brain volumes as assessed by magnetic resonance imaging, and both concurrent and longitudinal cognitive performance in multiple domains.

    Results: Elevated cerebral Abeta levels, in some cases comparable to those seen in individuals with Alzheimer disease, were observed in 29 participants, who also had smaller regional volumes in the hippocampus, temporal neocortex, anterior cingulate, and posterior cingulate. Concurrent cognitive performance was unrelated to Abeta levels but was related to regional brain volumes with the exception of the caudate. Longitudinal cognitive decline in episodic and working memory and visuospatial ability was associated with elevated Abeta levels and decreased hippocampal volume.

    Conclusion: The in vivo measure of cerebral amyloidosis known as [(11)C]PiB is associated with cross-sectional regionally specific brain atrophy and longitudinal cognitive decline in multiple cognitive domains that occur before the clinical diagnosis of Alzheimer disease. These findings contribute to the understanding of the cognitive and structural consequences of Abeta levels in cognitively healthy older adults.

    Funded by: NIA NIH HHS: F32 AG005861, P01 AG003991, P01 AG003991-26, P01 AG026276, P01 AG026276-05, P01 AG03991, P50 AG005681, P50 AG005681-26, P50 AG05861; NINDS NIH HHS: P30 NS048056, P30 NS048056-05

    Archives of neurology 2009;66;12;1476-81

  • CSF biomarker levels in early and late onset Alzheimer's disease.

    Bouwman FH, Schoonenboom NS, Verwey NA, van Elk EJ, Kok A, Blankenstein MA, Scheltens P and van der Flier WM

    Alzheimer Center and Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands. femke.bouwman@vumc.nl

    Objective: To compare CSF levels of beta-amyloid 1-42 (Abeta(1-42)), total tau (tau) and tau phosphorylated at threonine 181 (ptau-181) between AD patients and controls according to age.

    Methods: 248 AD patients (48% men) and 127 controls (51% men, 22 volunteers and 105 subjective complainers) underwent lumbar puncture. Both patients and controls were divided into a young (<65 years) and old (>or=65 years) group.

    Results: All three biomarkers showed main effects of diagnosis (p<0.001). There was an interaction between diagnosis and age for all three biomarkers (p<0.05), as old controls had lower Abeta(1-42) and higher (p)tau than young controls (Abeta(1-42) 699+/-250 versus 866+/-191pg/ml, tau 408+/-245 versus 243+/-102pg/ml, ptau-181 60+/-28 versus 42+/-15pg/ml), but there was no difference according to age among AD patients (Abeta(1-42) 451+/-178 versus 425+/-146pg/ml, tau 741+/-460 versus 798+/-467pg/ml, ptau-181 91+/-42 versus 91+/-41pg/ml).

    Conclusion: We found that the older control group had lower Abeta(1-42) and higher (p)tau compared to the younger control group. This suggests that older individuals may have AD pathology, even in the absence of objective cognitive impairment.

    Neurobiology of aging 2009;30;12;1895-901

  • Divalent metal transporter 1 is involved in amyloid precursor protein processing and Abeta generation.

    Zheng W, Xin N, Chi ZH, Zhao BL, Zhang J, Li JY and Wang ZY

    Key Laboratory of Cell Biology, Ministry of Public Health of China, Laboratory of Cell Engineering and Cell Therapy, China Medical University, Shenyang 110001, PR China.

    The amyloid-beta precursor protein (APP) and its pathogenic byproduct beta-amyloid peptide (Abeta) play central roles in the pathogenesis of Alzheimer's disease (AD). Reduction in levels of the potentially toxic Abeta is one of the most important therapeutic goals in AD. Recent studies have shown that bivalent metals such as iron, copper, and zinc are involved in APP expression, Abeta deposition, and senile plaque formation in the AD brain. However, the underlying mechanisms involved in abnormal homeostasis of bivalent metals in AD brain remain unclear. In the present study, we found that two isoforms of the divalent metal transporter 1 (DMT1), DMT1-IRE, and DMT1-nonIRE, were colocalized with Abeta in the plaques of postmortem AD brain. Using the APP/PS1 transgenic mouse model, we found that the levels of both DMT1-IRE and DMT1-nonIRE were significantly increased in the cortex and hippocampus compared with wild type-control. We further verified the proposed mechanisms by which DMT1 might be involved in APP processing and Abeta secretion by using the SH-SY5Y cell line stably overexpressing human APP Swedish mutation (APPsw) as a cell model. We found that overexpression of APPsw resulted in increased expression levels of both DMT1-IRE and DMT1-nonIRE in SH-SY5Y cells. Interestingly, silencing of endogenous DMT1 by RNA interference, which reduced bivalent ion influx, led to reductions of APP expression and Abeta secretion. These findings suggest both that DMT1 plays a critical role in ion-mediated neuropathogenesis in AD and that pharmacological blockage of DMT1 may provide novel therapeutic strategies against AD.

    FASEB journal : official publication of the Federation of American Societies for Experimental Biology 2009;23;12;4207-17

  • Ectodomain shedding of the receptor for advanced glycation end products: a novel therapeutic target for Alzheimer's disease.

    Zhang L, Postina R and Wang Y

    Department of Neurology, Zhongda Hospital Affiliated to Southeast University, 210009 Nanjing, China. zhangling9@hotmail.com

    Receptor for advanced glycation end products (RAGE) mediates diverse physiological and pathological effects and is involved in the pathogenesis of Alzheimer's disease (AD). RAGE is a receptor for amyloid beta peptides (Ab), mediates Abeta neurotoxicity and also promotes Abeta influx into the brain and contributes to Abeta aggregation. Soluble RAGE (sRAGE), a secreted RAGE isoform, acts as a decoy receptor to antagonize RAGE-mediated damages. Accumulating evidence has suggested that sRAGE represents a promising pharmaceutic against RAGE-mediated disorders. Recent studies revealed proteolysis of RAGE as a previously unappreciated means of sRAGE production. In this review we summarize these findings on the proteolytic cleavage of RAGE and discuss the underlying regulatory mechanisms of RAGE shedding. Furthermore, we propose a model in which proteolysis of RAGE could restrain AD development by reducing Abeta transport intothe brain and Abeta production via BACE. Thus, the modulation of RAGE proteolysis provides a novel intervention strategy for AD.

    Cellular and molecular life sciences : CMLS 2009;66;24;3923-35

  • High striatal amyloid beta-peptide deposition across different autosomal Alzheimer disease mutation types.

    Villemagne VL, Ataka S, Mizuno T, Brooks WS, Wada Y, Kondo M, Jones G, Watanabe Y, Mulligan R, Nakagawa M, Miki T, Shimada H, O'Keefe GJ, Masters CL, Mori H and Rowe CC

    Department of Nuclear Medicine, Centre for Positron Emission Tomography, Austin Health, Heidelberg, Australia. villemagne@petnm.unimelb.edu.au

    Background: Supported by compelling genetic data regarding early-onset familial Alzheimer disease (AD), the amyloid beta-peptide (Abeta)-centric theory holds that Abeta is involved in the pathogenesis of sporadic AD. Mutations in the amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) genes lead to increased Abeta levels before symptoms arise.

    Objectives: To evaluate the pattern of Pittsburgh Compound B (PiB) retention in subjects with different autosomal dominant mutations associated with familial AD vs that in healthy age-matched control subjects and subjects with probable sporadic AD, to correlate Abeta burden as measured by PiB with available clinical and cognitive data, and to compare the regional brain patterns of PiB retention and fluorodeoxyglucose F 18 (FDG) uptake.

    Design: Correlation analysis of positron emission tomography (PET) imaging studies.

    Setting: Academic research.

    Participants: Seven PSEN1 mutation carriers and 1 APP mutation carrier underwent PiB and FDG PET imaging. Amyloid beta-peptide burden and FDG uptake were established using standardized uptake values normalized to pons.

    Primary outcomes were PET results, which were compared with those of a well-characterized cohort of 30 healthy control subjects and 30 subjects with probable sporadic AD.

    Results: All mutation carriers had high PiB retention in the striatum, with some also having cortical PiB retention in ventrofrontal and posterior cingulate/precuneus areas. The striatal pattern of PiB retention was similar in the PSEN1 and APP mutation carriers. Neither striatal nor cortical Abeta burden was related to cognitive status.

    Conclusions: Consistent with previous studies, the pattern of Abeta deposition in familial AD differs from that in sporadic AD, with higher striatal and somewhat lower cortical PiB retention in familial AD. The pattern and degree of Abeta deposition were not associated with mutation type nor cognitive status.

    Archives of neurology 2009;66;12;1537-44

  • Pathology associated memory deficits in Swedish mutant genome-based amyloid precursor protein transgenic mice.

    Hock BJ, Lattal KM, Kulnane LS, Abel T and Lamb BT

    Department of Psychology, Austin Peay State University, Clarksville, TN, 37044 USA.

    To gain insight into the relationship between pathological alterations and memory deficits observed in Alzheimer's disease (AD), a number of amyloid precursor protein (APP) transgenic animal models have been generated containing familial AD mutations. The most commonly utilized method involves a cDNA-based approach, utilizing heterologous promoters to drive expression of specific APP isoforms. As a result of the assumptions inherent in the design of each model, the different cDNA-based transgenic mouse models have revealed different relationships between the biochemical, pathological and behavioral alterations observed in these models. Here we provide further characterization of a genomic-based, amyloid precursor protein yeast artificial chromosome transgenic mouse model of AD, R1.40, that makes few assumptions regarding disease pathogenesis to study the relationship between brain pathology and altered behavior. Aged R1.40 transgenic and control mice were tested for learning and memory in the Morris water maze and for working memory in the Y maze. Results from the water maze demonstrated intact learning in the both control and R1.40 mice, but impairments in the long-term retention of this information in the transgenic mice, but not controls. Interestingly, however, long-term memory deficits did not correlate with the presence of Abeta deposits within the group of animals examined. By contrast, age-related working memory impairments were also observed in the Y maze in the R1.40 mice, and these deficits correlated with the presence of Abeta deposits. Our results demonstrate unique behavioral alterations in the R1.40 mouse model of AD that are likely both dependent and independent of Abeta deposition.

    Funded by: NCI NIH HHS: CA 43703; NIA NIH HHS: AG05875, P50 AG08012, R01 AG023012; NIMH NIH HHS: MH 012441, MH 60244

    Current aging science 2009;2;3;205-13

  • PSEN1 polymorphisms alter the rate of cognitive decline in sporadic Alzheimer's disease patients.

    Belbin O, Beaumont H, Warden D, Smith AD, Kalsheker N and Morgan K

    Division of Clinical Chemistry, Institute of Genetics, Queen's Medical Centre, University of Nottingham, NG7 2UH, UK.

    Mutations in amyloid precursor protein (APP) and presenilin (PSEN) genes are known to cause familial early-onset Alzheimer's disease (AD), which account for around 5% of AD cases. Genetic associations for the remaining "sporadic" cases, other than the risks associated with the apolipoprotein (APOE) epsilon4 allele are currently not fully established. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) in PSEN1 are associated with a modified risk for sporadic AD or a modified disease phenotype. Eight tag SNPs were identified using linkage disequilibrium (LD) data from the International HapMap project providing coverage of the entire PSEN1 gene. These SNPs were investigated for AD susceptibility in a case-control haplotype association study (N=714) and for genotype-specific effects on cognitive performance in AD patients (N=169) using non-linear mixed effects modelling. Replication of a mild associated-risk of an intronic PSEN1 polymorphism with AD was achieved (P=0.03). No other single SNPs or haplotypes were associated with AD risk. However, 3 SNPs were associated with an altered rate of cognitive decline underlining their role as genetic modifiers of disease.

    Neurobiology of aging 2009;30;12;1992-9

  • Rck/p54 interacts with APP mRNA as part of a multi-protein complex and enhances APP mRNA and protein expression in neuronal cell lines.

    Broytman O, Westmark PR, Gurel Z and Malter JS

    Department of Pathology and Laboratory Medicine, Neuroscience Training Program, Waisman Center for Developmental Disabilities and Institute on Aging, University of Wisconsin, Madison, 1500 Highland Avenue, Madison, WI 53705, USA.

    Overproduction of amyloid precursor protein (APP) and beta-amyloid likely contribute to neurodegeneration seen in Alzheimer's disease (AD). APP mRNA contains several, 3'-untranslated region (UTR), cis-acting regulatory elements. A 52 base element (52sce), immediately downstream from the stop codon, has been previously shown to complex with uncharacterized cytoplasmic proteins. In this study, we purify and identify six proteins that specifically bind to the 52sce, and show that these proteins interact with each other and with APP mRNA in intact human neuroblastoma cells. We also present evidence that at least one of these proteins, the DEAD-box helicase rck/p54, is involved in post-transcriptional regulation, as its overexpression in cultured cells results in elevated levels of APP mRNA and protein. These findings suggest a novel mechanism for post-transcriptional regulation of APP mRNA.

    Funded by: NIA NIH HHS: R01 AG010675, R01 AG010675-15, R01 AG10675; NICHD NIH HHS: P30 HD03352

    Neurobiology of aging 2009;30;12;1962-74

  • Residues at P2-P1 positions of epsilon- and zeta-cleavage sites are important in formation of beta-amyloid peptide.

    Tan J, Mao G, Cui MZ, Lamb B, Sy MS and Xu X

    Department of Pathobiology, College of Veterinary Medicine, The University of Tennessee, 2407 River Drive, Knoxville, TN 37996, USA.

    Most of the Alzheimer's disease (AD)-linked mutations in amyloid precursor protein (APP), which cause abnormal production of beta-amyloid (Abeta), are localized at the major beta-secretase-and gamma-secretase cleavage sites. In this study, using an APP-knockout mouse neuronal cell line, our data demonstrated that at the P2-P1 positions of the epsilon-cleavage site at Abeta49 and the zeta-cleavage site at Abeta46, aromatic amino acids caused a strong reduction in total Abeta. On the other hand, residues with a long side chain caused a decrease in Abeta(40) and a concomitant increase in Abeta(42) and Abeta(38). These findings indicate that the structures of the substituting residues at these key positions strongly determine the efficiency and preference of gamma-secretase-mediated APP processing, which determines the ratio of different secreted Abeta species, a crucial factor in the disease development. Our findings provide new insight into the mechanisms of gamma-secretase-mediated APP processing and, specifically, into why most AD-linked APP mutations are localized at major gamma-secretase cleavage sites. This information may contribute to the development of methods of prevention and treatment of Alzheimer's disease aimed at modulating gamma-secretase activity.

    Funded by: NIA NIH HHS: R01 AG026640, R01AG26640, R21 AG039596; NINDS NIH HHS: R01 NS042314

    Neurobiology of disease 2009;36;3;453-60

  • Receptor-associated protein interacts with amyloid-beta peptide and promotes its cellular uptake.

    Kanekiyo T and Bu G

    Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

    Brain amyloid-beta (Abeta) peptide accumulation and aggregation are critical events in the pathogenesis of Alzheimer disease. Increasing evidence has demonstrated that LRP1 is involved in Alzheimer disease pathogenesis. The physiological ligands of LRP1, including apoE, play significant roles in the cellular clearance of Abeta. The receptor-associated protein (RAP) is a specialized chaperone for members of the low density lipoprotein receptor family. RAP shares structural and receptor-binding properties with apoE. Here, we show that RAP binds to both Abeta40 and Abeta42 in a concentration-dependent manner and forms complexes with them. Fluorescence-activated cell sorter analysis showed that RAP significantly enhances the cellular internalization of Abeta in different cell types, including brain vascular smooth muscle, neuroblastoma, glioblastoma, and Chinese hamster ovary cells. This effect of RAP was confirmed by fluorescence microscopy and enzyme-linked immunosorbent assay. RAP binds to both LRP1 and heparin; however, the ability of RAP to enhance Abeta cellular uptake was blocked by heparin and heparinase treatment but not by LRP1 deficiency. Furthermore, the effects of RAP were significantly decreased in heparan sulfate proteoglycan-deficient Chinese hamster ovary cells. Our findings reveal that RAP is a novel Abeta-binding protein that promotes cellular internalization of Abeta.

    Funded by: NIA NIH HHS: AG027924, AG031784, P01 AG030128, R01 AG027924, R01 AG031784

    The Journal of biological chemistry 2009;284;48;33352-9

  • Basal cerebral metabolism may modulate the cognitive effects of Abeta in mild cognitive impairment: an example of brain reserve.

    Cohen AD, Price JC, Weissfeld LA, James J, Rosario BL, Bi W, Nebes RD, Saxton JA, Snitz BE, Aizenstein HA, Wolk DA, Dekosky ST, Mathis CA and Klunk WE

    Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.

    Inverse correlations between amyloid-beta (Abeta) load measured by Pittsburgh Compound-B (PiB) positron emission tomography (PET) and cerebral metabolism using [(18)F]fluoro-2-deoxy-d-glucose (FDG) in Alzheimer's disease (AD) patients, suggest local Abeta-induced metabolic insults. However, this relationship has not been well studied in mild cognitive impairment (MCI) or amyloid-positive controls. Here, we explored associations of Abeta deposition with metabolism via both region-of-interest-based and voxel-based analyses in amyloid-positive control subjects and patients with MCI or AD. Metabolism in parietal and precuneus cortices of AD patients was negatively correlated with PiB retention locally, and more distantly with PiB retention in frontal cortex. In amyloid-positive controls, no clear patterns in correlations were observed. In MCI patients, there were essentially no significant, negative correlations, but there were frequent significant positive correlations between metabolism and PiB retention. Metabolism in anterior cingulate showed positive correlations with PiB in most brain areas in MCI, and metabolism and PiB retention were positively correlated locally in precuneus/parietal cortex. However, there was no significant increase in metabolism in MCI compared to age-matched controls, negating the possibility that Abeta deposition directly caused reactive hypermetabolism. This suggests that, in MCI, higher basal metabolism could either be exacerbating Abeta deposition or increasing the level of Abeta necessary for cognitive impairment sufficient for the clinical diagnosis of AD. Only after extensive Abeta deposition has been present for longer periods of time does Abeta become the driving force for decreased metabolism in clinical AD and, only in more vulnerable brain regions such as parietal and precuneus cortices.

    Funded by: NIA NIH HHS: K02 AG001039, K02 AG001039-01A1, K02 AG001039-02, K02 AG001039-03, K02 AG001039-04, K02 AG001039-05, K02 AG027998, P01 AG025204, P01 AG025204-010001, P01 AG025204-020001, P01 AG025204-030001, P01 AG025204-04, P01 AG025204-040001, P01 AG025204-04S1, P01 AG025204-05, P01 AG025204-050001, P50 AG005133, P50 AG005133-220021, P50 AG005133-230021, P50 AG005133-240021, P50 AG005133-250021, P50 AG005133-260021, R01 AG018402, R37 AG025516, R37 AG025516-01, R37 AG025516-02, R37 AG025516-03, R37 AG025516-04, R37 AG025516-05, R37 AG025516-05S1, R37 AG025516-07; NIMH NIH HHS: K01 MH001976, R01 MH070729

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;47;14770-8

  • RAGE-mediated signaling contributes to intraneuronal transport of amyloid-beta and neuronal dysfunction.

    Takuma K, Fang F, Zhang W, Yan S, Fukuzaki E, Du H, Sosunov A, McKhann G, Funatsu Y, Nakamichi N, Nagai T, Mizoguchi H, Ibi D, Hori O, Ogawa S, Stern DM, Yamada K and Yan SS

    Laboratory of Medicinal Pharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka 565-0871, Japan.

    Intracellular amyloid-beta peptide (Abeta) has been implicated in neuronal death associated with Alzheimer's disease. Although Abeta is predominantly secreted into the extracellular space, mechanisms of Abeta transport at the level of the neuronal cell membrane remain to be fully elucidated. We demonstrate that receptor for advanced glycation end products (RAGE) contributes to transport of Abeta from the cell surface to the intracellular space. Mouse cortical neurons exposed to extracellular human Abeta subsequently showed detectable peptide intracellularly in the cytosol and mitochondria by confocal microscope and immunogold electron microscopy. Pretreatment of cultured neurons from wild-type mice with neutralizing antibody to RAGE, and neurons from RAGE knockout mice displayed decreased uptake of Abeta and protection from Abeta-mediated mitochondrial dysfunction. Abeta activated p38 MAPK, but not SAPK/JNK, and then stimulated intracellular uptake of Abeta-RAGE complex. Similar intraneuronal co-localization of Abeta and RAGE was observed in the hippocampus of transgenic mice overexpressing mutant amyloid precursor protein. These findings indicate that RAGE contributes to mechanisms involved in the translocation of Abeta from the extracellular to the intracellular space, thereby enhancing Abeta cytotoxicity.

    Funded by: NIA NIH HHS: P01 AG017490, P01AG17490

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;47;20021-6

  • Isolation and characterization of patient-derived, toxic, high mass amyloid beta-protein (Abeta) assembly from Alzheimer disease brains.

    Noguchi A, Matsumura S, Dezawa M, Tada M, Yanazawa M, Ito A, Akioka M, Kikuchi S, Sato M, Ideno S, Noda M, Fukunari A, Muramatsu S, Itokazu Y, Sato K, Takahashi H, Teplow DB, Nabeshima Y, Kakita A, Imahori K and Hoshi M

    Mitsubishi Kagaku Institute of Life Sciences, Tokyo 194-8511, Japan.

    Amyloid beta-protein (Abeta) assemblies are thought to play primary roles in Alzheimer disease (AD). They are considered to acquire surface tertiary structures, not present in physiologic monomers, that are responsible for exerting toxicity, probably through abnormal interactions with their target(s). Therefore, Abeta assemblies having distinct surface tertiary structures should cause neurotoxicity through distinct mechanisms. Aiming to clarify the molecular basis of neuronal loss, which is a central phenotype in neurodegenerative diseases such as AD, we report here the selective immunoisolation of neurotoxic 10-15-nm spherical Abeta assemblies termed native amylospheroids (native ASPDs) from AD and dementia with Lewy bodies brains, using ASPD tertiary structure-dependent antibodies. In AD patients, the amount of native ASPDs was correlated with the pathologic severity of disease. Native ASPDs are anti-pan oligomer A11 antibody-negative, high mass (>100 kDa) assemblies that induce degeneration particularly of mature neurons, including those of human origin, in vitro. Importantly, their immunospecificity strongly suggests that native ASPDs have a distinct surface tertiary structure from other reported assemblies such as dimers, Abeta-derived diffusible ligands, and A11-positive assemblies. Only ASPD tertiary structure-dependent antibodies could block ASPD-induced neurodegeneration. ASPDs bind presynaptic target(s) on mature neurons and have a mode of toxicity different from those of other assemblies, which have been reported to exert their toxicity through binding postsynaptic targets and probably perturbing glutamatergic synaptic transmission. Thus, our findings indicate that native ASPDs with a distinct toxic surface induce neuronal loss through a different mechanism from other Abeta assemblies.

    Funded by: NINDS NIH HHS: NS038328, R01 NS038328

    The Journal of biological chemistry 2009;284;47;32895-905

  • Amyloid precursor protein mediates a tyrosine kinase-dependent activation response in endothelial cells.

    Austin SA, Sens MA and Combs CK

    Departments of Pharmacology, Physiology, and Therapeutics and Pathology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202, USA.

    Amyloid precursor protein (APP) is a ubiquitously expressed type 1 integral membrane protein. It has the ability to bind numerous extracellular matrix components and propagate signaling responses via its cytoplasmic phospho-tyrosine, (682)YENPTY(687), binding motif. We recently demonstrated increased protein levels of APP, phosphorylated APP (Tyr682), and beta-amyloid (Abeta) in brain vasculature of atherosclerotic and Alzheimer's disease (AD) tissue colocalizing primarily within the endothelial layer. This study demonstrates similar APP changes in peripheral vasculature from human and mouse apoE(-/-) aorta, suggesting that APP-related changes are not restricted to brain vasculature. Therefore, primary mouse aortic endothelial cells and human umbilical vein endothelial cells were used as a model system to examine the function of APP in endothelial cells. APP multimerization with an anti-N-terminal APP antibody, 22C11, to simulate ligand binding stimulated an Src kinase family-dependent increase in protein phospho-tyrosine levels, APP phosphorylation, and Abeta secretion. Furthermore, APP multimerization stimulated increased protein levels of the proinflammatory proteins, cyclooxygenase-2 and vascular cell adhesion molecule-1 also in an Src kinase family-dependent manner. Endothelial APP was also involved in mediating monocytic cell adhesion. Collectively, these data demonstrate that endothelial APP regulates immune cell adhesion and stimulates a tyrosine kinase-dependent response driving acquisition of a reactive endothelial phenotype. These APP-mediated events may serve as therapeutic targets for intervention in progressive vascular changes common to cerebrovascular disease and AD.

    Funded by: NCRR NIH HHS: 2P20RR017600, P20 RR017699, P20 RR017699-08; NIA NIH HHS: 1R01AG026330, R01 AG026330-03

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;46;14451-62

  • Divergent pathways mediate spine alterations and cell death induced by amyloid-beta, wild-type tau, and R406W tau.

    Tackenberg C and Brandt R

    Department of Neurobiology, University of Osnabrück, D-49076 Osnabrück, Germany.

    Alzheimer's disease is characterized by synaptic alterations and neurodegeneration. Histopathological hallmarks represent amyloid plaques composed of amyloid-beta (Abeta) and neurofibrillary tangles containing hyperphosphorylated tau. To determine whether synaptic changes and neurodegeneration share common pathways, we established an ex vivo model using organotypic hippocampal slice cultures from amyloid precursor protein transgenic mice combined with virus-mediated expression of EGFP-tagged tau constructs. Confocal high-resolution imaging, algorithm-based evaluation of spines, and live imaging were used to determine spine changes and neurodegeneration. We report that Abeta but not tau induces spine loss and shifts spine shape from mushroom to stubby through a mechanism involving NMDA receptor (NMDAR), calcineurin, and GSK-3beta activation. In contrast, Abeta alone does not cause neurodegeneration but induces toxicity through phosphorylation of wild-type (wt) tau in an NMDAR-dependent pathway. We show that GSK-3beta levels are elevated in APP transgenic cultures and that inhibiting GSK-3beta activity or use of phosphorylation-blocking tau mutations prevented Abeta-induced toxicity of tau. FTDP-17 tau mutants are differentially affected by Abeta. While R406W tau shows increased toxicity in the presence of Abeta, no change is observed with P301L tau. While blocking NMDAR activity abolishes toxicity of both wt and R406W tau, the inhibition of GSK-3beta only protects against toxicity of wt tau but not of R406W tau induced by Abeta. Tau aggregation does not correlate with toxicity. We propose that Abeta-induced spine pathology and tau-dependent neurodegeneration are mediated by divergent pathways downstream of NMDAR activation and suggest that Abeta affects wt and R406W tau toxicity by different pathways downstream of NMDAR activity.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;46;14439-50

  • Expression of complement system components during aging and amyloid deposition in APP transgenic mice.

    Reichwald J, Danner S, Wiederhold KH and Staufenbiel M

    Novartis Institutes for BioMedical Research, Forum1, Novartis Campus, CH-4056 Basel, Switzerland. julia.reichwald@novartis.com

    Background: A causal role of the complement system in Alzheimer's disease pathogenesis has been postulated based on the identification of different activated components up to the membrane attack complex at amyloid plaques in brain. However, histological studies of amyloid plaque bearing APP transgenic mice provided only evidence for an activation of the early parts of the complement cascade. To better understand the contribution of normal aging and amyloid deposition to the increase in complement activation we performed a detailed characterization of the expression of the major mouse complement components.

    Methods: APP23 mice expressing human APP751 with the Swedish double mutation as well as C57BL/6 mice were used at different ages. mRNA was quantified by Realtime PCR and the age- as well as amyloid induced changes determined. The protein levels of complement C1q and C3 were analysed by Western blotting. Histology was done to test for amyloid plaque association and activation of the complement cascade.

    Results: High mRNA levels were detected for C1q and some inhibitory complement components. The expression of most activating components starting at C3 was low. Expression of C1q, C3, C4, C5 and factor B mRNA increased with age in control C57BL/6 mice. C1q and C3 mRNA showed a substantial additional elevation during amyloid formation in APP23 mice. This increase was confirmed on the protein level using Western blotting, whereas immunohistology indicated a recruitment of complement to amyloid plaques up to the C3 convertase.

    Conclusion: Early but not late components of the mouse complement system show an age-dependent increase in expression. The response to amyloid deposition is comparatively smaller. The low expression of C3 and C5 and failure to upregulate C5 and downstream components differs from human AD brain and likely contributes to the lack of full complement activation in APP transgenic mice.

    Journal of neuroinflammation 2009;6;35

  • Amyloid-beta dynamics are regulated by orexin and the sleep-wake cycle.

    Kang JE, Lim MM, Bateman RJ, Lee JJ, Smyth LP, Cirrito JR, Fujiki N, Nishino S and Holtzman DM

    Department of Neurology, Washington University, St. Louis, MO 63110, USA.

    Amyloid-beta (Abeta) accumulation in the brain extracellular space is a hallmark of Alzheimer's disease. The factors regulating this process are only partly understood. Abeta aggregation is a concentration-dependent process that is likely responsive to changes in brain interstitial fluid (ISF) levels of Abeta. Using in vivo microdialysis in mice, we found that the amount of ISF Abeta correlated with wakefulness. The amount of ISF Abeta also significantly increased during acute sleep deprivation and during orexin infusion, but decreased with infusion of a dual orexin receptor antagonist. Chronic sleep restriction significantly increased, and a dual orexin receptor antagonist decreased, Abeta plaque formation in amyloid precursor protein transgenic mice. Thus, the sleep-wake cycle and orexin may play a role in the pathogenesis of Alzheimer's disease.

    Funded by: NIA NIH HHS: AG025824, AG029524, AG030946, K01 AG029524, K01 AG029524-03, K23 AG030946, K23 AG030946-03, P50 AG005681, R01 AG025824, R01 AG025824-03; NIDDK NIH HHS: P30 DK056341, P30 DK056341-09; NIMH NIH HHS: MH072525, R01 MH072525, R01 MH072525-04; NINDS NIH HHS: NS065667, P30 NS057105, P30 NS057105-04, R01 NS065667, R01 NS065667-02

    Science (New York, N.Y.) 2009;326;5955;1005-7

  • The molecular chaperone Hsp90 modulates intermediate steps of amyloid assembly of the Parkinson-related protein alpha-synuclein.

    Falsone SF, Kungl AJ, Rek A, Cappai R and Zangger K

    Institute of Chemistry, University of Graz, Heinrichstrasse 28, A-8010 Graz, Austria. fabio.falsone@uni-graz.at

    Alpha-synuclein is an intrinsically unstructured protein that binds to membranes, forms fibrils, and is involved in neurodegeneration. We used a reconstituted in vitro system to show that the molecular chaperone Hsp90 influenced alpha-synuclein vesicle binding and amyloid fibril formation, two processes that are tightly coupled to alpha-synuclein folding. Binding of Hsp90 to monomeric alpha-synuclein occurred in the low micromolar range, involving regions of alpha-synuclein that are critical for vesicle binding and amyloidogenesis. As a consequence, both processes were affected. In the absence of ATP, the accumulation of non-amyloid alpha-synuclein oligomers prevailed over fibril formation, whereas ATP favored fibril growth. This suggests that Hsp90 modulates the assembly of alpha-synuclein in an ATP-dependent manner. We propose that Hsp90 affects these folding processes by restricting conformational fluctuations of alpha-synuclein.

    The Journal of biological chemistry 2009;284;45;31190-9

  • Human serum albumin inhibits Abeta fibrillization through a "monomer-competitor" mechanism.

    Milojevic J, Raditsis A and Melacini G

    Department of Chemistry and Chemical Biology, and Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.

    Human serum albumin (HSA) is not only a fatty acid and drug carrier protein, it is also a potent inhibitor of Abeta self-association in plasma. However, the mechanism underlying the inhibition of Abeta fibrillization by HSA is still not fully understood. We therefore investigated the Abeta-HSA system using a combined experimental strategy based on saturation transfer difference (STD) NMR and intrinsic albumin fluorescence experiments on three Abeta peptides with different aggregation propensities (i.e., Abeta(12-28), Abeta(1-40), and Abeta(1-42)). Our data consistently show that albumin selectively binds to cross-beta-structured Abeta oligomers as opposed to Abeta monomers. The HSA/Abeta oligomer complexes have K(D) values in the micromolar to submicromolar range and compete with the further addition of Abeta monomers to the Abeta assemblies, thus inhibiting fibril growth ("monomer competitor" model). Other putative mechanisms, according to which albumin acts as a "monomer stabilizer" or a "dissociation catalyst", are not supported by our data, thus resolving previous discrepancies in the literature regarding Abeta-HSA interactions. In addition, the model and the experimental approaches proposed here are anticipated to have broad relevance for the characterization of other systems that involve amyloidogenic peptides and oligomerization inhibitors.

    Biophysical journal 2009;97;9;2585-94

  • Amyloid precursor protein is required for convergent-extension movements during Zebrafish development.

    Joshi P, Liang JO, DiMonte K, Sullivan J and Pimplikar SW

    Department of Neurosciences, Lerner Research Institute, Cleveland Clinic NC-30, Cleveland, OH 44195, USA.

    Amyloid precursor protein (APP) has been a focus of intense investigation because of its role in Alzheimer's disease (AD), however, its biological function remains uncertain. Loss of APP and APP-like proteins results in postnatal lethality in mice, suggesting a role during embryogenesis. Here we show that in a zebrafish model system, knock down of APP results in the generation of fish with dramatically reduced body length and a short, curly tail. In situ examination of gene expression suggests that the APP morphant embryos have defective convergent-extension movements. We also show that wild-type human APP rescues the morphant phenotype, but the Swedish mutant APP, which causes familial AD (fAD), does not rescue the developmental defects. Collectively, this work demonstrates that the zebrafish model is a powerful system to define the role of APP during embryonic development and to evaluate the functional activity of fAD mutant APP.

    Developmental biology 2009;335;1;1-11

  • Proteomics-derived cerebrospinal fluid markers of autopsy-confirmed Alzheimer's disease.

    Roher AE, Maarouf CL, Sue LI, Hu Y, Wilson J and Beach TG

    The Longtine Center for Molecular Biology and Genetics, Sun Health Research Institute, 10515 West Santa Fe Drive, Sun City, AZ 85351, USA. alex.roher@bannerhealth.com

    The diagnostic performance of several candidate cerebrospinal fluid (CSF) protein biomarkers in neuropathologically confirmed Alzheimer's disease (AD), non-demented (ND) elderly controls and non-AD dementias (NADD) was assessed. Candidate markers were selected on the basis of initial two-dimensional gel electrophoresis studies or by literature review. Markers selected by the former method included apolipoprotein A-1 (ApoA1), haemopexin (HPX), transthyretin (TTR) and pigment epithelium-derived factor (PEDF), while markers identified from the literature included Abeta1-40, Abeta1-42, total tau, phosphorylated tau, alpha-1 acid glycoprotein (A1GP), haptoglobin, zinc alpha-2 glycoprotein (Z2GP) and apolipoprotein E (ApoE). Ventricular CSF concentrations of the markers were measured by enzyme-linked immunosorbent assay (ELISA). The concentrations of Abeta1-42, ApoA1, A1GP, ApoE, HPX and Z2GP differed significantly among AD, ND and NADD subjects. Logistic regression analysis for the diagnostic discrimination of AD from ND found that Abeta1-42, ApoA1 and HPX each had significant and independent associations with diagnosis. The CSF concentrations of these three markers distinguished AD from ND subjects with 84% sensitivity and 72% specificity, with 78% of subjects correctly classified. By comparison, using Abeta1-42 alone gave 79% sensitivity and 61% specificity, with 68% of subjects correctly classified. For the diagnostic discrimination of AD from NADD, only the concentration of Abeta1-42 was significantly related to diagnosis, with a sensitivity of 58%, specificity of 86% and 86% correctly classified. The results indicate that for the discrimination of AD from ND control subjects, measurement of a set of markers including Abeta1-42, ApoA1 and HPX improved diagnostic performance over that obtained by measurement of Abeta1-42 alone. For the discrimination of AD from NADD subjects, measurement of Abeta1-42 alone was superior.

    Funded by: NIA NIH HHS: P30 AG019610, P30 AG019610-04, P30 AG19610, U01 AG016976

    Biomarkers : biochemical indicators of exposure, response, and susceptibility to chemicals 2009;14;7;493-501

  • Alzheimer's disease-like pathological features in transgenic mice expressing the APP intracellular domain.

    Ghosal K, Vogt DL, Liang M, Shen Y, Lamb BT and Pimplikar SW

    Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.

    The hypothesis that amyloid-beta (Abeta) peptides are the primary cause of Alzheimer's disease (AD) remains the best supported theory of AD pathogenesis. Yet, many observations are inconsistent with the hypothesis. Abeta peptides are generated when amyloid precursor protein (APP) is cleaved by presenilins, a process that also produces APP intracellular domain (AICD). We previously generated AICD-overexpressing transgenic mice that showed abnormal activation of GSK-3beta, a pathological feature of AD. We now report that these mice exhibit additional AD-like characteristics, including hyperphosphorylation and aggregation of tau, neurodegeneration and working memory deficits that are prevented by treatment with lithium, a GSK-3beta inhibitor. Consistent with its potential role in AD pathogenesis, we find AICD levels to be elevated in brains from AD patients. The in vivo findings that AICD can contribute to AD pathology independently of Abeta have important therapeutic implications and may explain some observations that are discordant with the amyloid hypothesis.

    Funded by: NIA NIH HHS: R01 AG026146, R01AG026146; NICHD NIH HHS: T32 HD007104

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;43;18367-72

  • Degradation of amyloid beta protein by purified myelin basic protein.

    Liao MC, Ahmed M, Smith SO and Van Nostrand WE

    Department of Neurosurgery, Stony Brook University, Stony Brook, New York 11794-8122, USA.

    The progressive accumulation of beta-amyloid (Abeta) in senile plaques and in the cerebral vasculature is the hallmark of Alzheimer disease and related disorders. Impaired clearance of Abeta from the brain likely contributes to the prevalent sporadic form of Alzheimer disease. Several major pathways for Abeta clearance include receptor-mediated cellular uptake, blood-brain barrier transport, and direct proteolytic degradation. Myelin basic protein (MBP) is the major structural protein component of myelin and plays a functional role in the formation and maintenance of the myelin sheath. MBP possesses endogenous serine proteinase activity and can undergo autocatalytic cleavage liberating distinct fragments. Recently, we showed that MBP binds Abeta and inhibits Abeta fibril formation (Hoos, M. D., Ahmed, M., Smith, S. O., and Van Nostrand, W. E. (2007) J. Biol. Chem. 282, 9952-9961; Hoos, M. D., Ahmed, M., Smith, S. O., and Van Nostrand, W. E. (2009) Biochemistry 48, 4720-4727). Here we show that Abeta40 and Abeta42 peptides are degraded by purified human brain MBP and recombinant human MBP, but not an MBP fragment that lacks autolytic activity. MBP-mediated Abeta degradation is inhibited by serine proteinase inhibitors. Similarly, Cos-1 cells expressing MBP degrade exogenous Abeta40 and Abeta42. In addition, we demonstrate that purified MBP also degrades assembled fibrillar Abeta in vitro. Mass spectrometry analysis identified distinct degradation products generated from Abeta digestion by MBP. Lastly, we demonstrate in situ that purified MBP can degrade parenchymal amyloid plaques as well as cerebral vascular amyloid that form in brain tissue of Abeta precursor protein transgenic mice. Together, these findings indicate that purified MBP possesses Abeta degrading activity in vitro.

    Funded by: NIA NIH HHS: R01 AG027317, R01-AG027317; NIGMS NIH HHS: T32 GM008444; NINDS NIH HHS: R01 NS035781, R01-NS035781

    The Journal of biological chemistry 2009;284;42;28917-25

  • Induced dimerization of the amyloid precursor protein leads to decreased amyloid-beta protein production.

    Eggert S, Midthune B, Cottrell B and Koo EH

    Department of Neurosciences, University of California, San Diego, La Jolla, California 92093, USA.

    The amyloid precursor protein (APP) plays a central role in Alzheimer disease (AD) pathogenesis because sequential cleavages by beta- and gamma-secretase lead to the generation of the amyloid-beta (Abeta) peptide, a key constituent in the amyloid plaques present in brains of AD individuals. In several studies APP has recently been shown to form homodimers, and this event appears to influence Abeta generation. However, these studies have relied on APP mutations within the Abeta sequence itself that may affect APP processing by interfering with secretase cleavages independent of dimerization. Therefore, the impact of APP dimerization on Abeta production remains unclear. To address this question, we compared the approach of constitutive cysteine-induced APP dimerization with a regulatable dimerization system that does not require the introduction of mutations within the Abeta sequence. To this end we generated an APP chimeric molecule by fusing a domain of the FK506-binding protein (FKBP) to the C terminus of APP. The addition of the synthetic membrane-permeant drug AP20187 induces rapid dimerization of the APP-FKBP chimera. Using this system we were able to induce up to 70% APP dimers. Our results showed that controlled homodimerization of APP-FKBP leads to a 50% reduction in total Abeta levels in transfected N2a cells. Similar results were obtained with the direct precursor of beta-secretase cleavage, C99/SPA4CT-FKBP. Furthermore, there was no modulation of different Abeta peptide species after APP dimerization in this system. Taken together, our results suggest that APP dimerization can directly affect gamma-secretase processing and that dimerization is not required for Abeta production.

    Funded by: NIA NIH HHS: AG 12376, R01 AG012376

    The Journal of biological chemistry 2009;284;42;28943-52

  • TMP21 transmembrane domain regulates gamma-secretase cleavage.

    Pardossi-Piquard R, Böhm C, Chen F, Kanemoto S, Checler F, Schmitt-Ulms G, St George-Hyslop P and Fraser PE

    Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario M5S 3H2, Canada.

    TMP21 has been shown to be associated with the gamma-secretase complex and can specifically regulate gamma-cleavage without affecting epsilon-mediated proteolysis. To explore the basis of this activity, TMP21 modulation of gamma-secretase activity was investigated independent of epsilon-cleavage using an amyloid-beta precursor proteinepsilon (APPepsilon) construct which lacks the amyloid intracellular domain domain. The APPepsilon construct behaves similarly to the full-length precursor protein with respect to alpha- and beta-cleavages and is able to undergo normal gamma-processing. Co-expression of APPepsilon and TMP21 resulted in the accumulation of membrane-embedded higher molecular weight Abeta-positive fragments, consistent with an inhibition of gamma-secretase cleavage. The APPepsilon system was used to examine the functional domains of TMP21 through the investigation of a series of TMP21-p24a chimera proteins. It was found that chimeras containing the transmembrane domain bound to the gamma-secretase complex and could decrease gamma-secretase proteolytic processing. This was confirmed though investigation of a synthetic peptide corresponding to the TMP21 transmembrane helix. The isolated TMP21 TM peptide but not the homologous p24a domain was able to reduce Abeta production in a dose-dependent fashion. These observations suggest that the TMP21 transmembrane domain promotes its association with the presenilin complex that results in decreased gamma-cleavage activity.

    Funded by: Wellcome Trust: 081864

    The Journal of biological chemistry 2009;284;42;28634-41

  • Nuclear signaling by the APP intracellular domain occurs predominantly through the amyloidogenic processing pathway.

    Goodger ZV, Rajendran L, Trutzel A, Kohli BM, Nitsch RM and Konietzko U

    Psychiatry Research, University of Zurich, August-Forel Strasse 1, 8008 Zurich, Switzerland.

    Proteolytic processing of the amyloid precursor protein (APP) occurs via two alternative pathways, localized to different subcellular compartments, which result in functionally distinct outcomes. Cleavage by a beta-gamma sequence generates the Abeta peptide that plays a central role in Alzheimer's disease. In the case of alpha-gamma cleavage, a secreted neurotrophic molecule is generated and the Abeta peptide cleaved and destroyed. In both cases, a cytosolic APP intracellular domain (AICD) is generated. We have previously shown that coexpression of APP with the APP-binding protein Fe65 and the histone acetyltransferase Tip60 results in the formation of nuclear complexes (termed AFT complexes), which localize to transcription sites. We now show that blocking endocytosis or the pharmacological or genetic inhibition of the endosomal beta-cleavage pathway reduces translocation of AICD to these nuclear AFT complexes. AICD signaling further depends on active transport along microtubules and can be modulated by interference with both anterograde and retrograde transport systems. Nuclear signaling by endogenous AICD in primary neurons could similarly be blocked by inhibiting beta-cleavage but not by alpha-cleavage inhibition. This suggests that amyloidogenic cleavage, despite representing the minor cleavage pathway of APP, is predominantly responsible for AICD-mediated nuclear signaling.

    Journal of cell science 2009;122;Pt 20;3703-14

  • Identification and characterisation of the novel amyloid-beta peptide-induced protein p17.

    Nehar S, Mishra M and Heese K

    Department of Molecular and Cell Biology, School of Biological Sciences, College of Science, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.

    Amyloid-beta peptide (Abeta) achieves neurodegeneration through unknown mechanisms. To elucidate some of these mechanisms, we conducted a cDNA subtraction analysis of Abeta-mediated neurotoxicity in neuronal cells and observed an up-regulation of the novel gene p17. The p17 protein was also found elevated in Alzheimer's disease (AD) mouse model. Here, we characterised p17 primarily in cell lines with respect to its localisation, function and physiological expression. We discovered that p17 acts downstream of protein kinase C and inhibits the tyrosine receptor kinase B-brain-derived neurotrophic factor (TrkB-BDNF) pathway. It impedes survival factors and enhances amyloid precursor protein expression thus suggesting its involvement in the Abeta-mediated pro-apoptotic pathways in AD.

    FEBS letters 2009;583;19;3247-53

  • AAV-tau mediates pyramidal neurodegeneration by cell-cycle re-entry without neurofibrillary tangle formation in wild-type mice.

    Jaworski T, Dewachter I, Lechat B, Croes S, Termont A, Demedts D, Borghgraef P, Devijver H, Filipkowski RK, Kaczmarek L, Kügler S and Van Leuven F

    Experimental Genetics Group, Department of Human Genetics, KULeuven-Campus, Leuven, Belgium.

    In Alzheimer's disease tauopathy is considered secondary to amyloid, and the duality obscures their relation and the definition of their respective contributions.Transgenic mouse models do not resolve this problem conclusively, i.e. the relative hierarchy of amyloid and tau pathology depends on the actual model and the genes expressed or inactivated. Here, we approached the problem in non-transgenic models by intracerebral injection of adeno-associated viral vectors to express protein tau or amyloid precursor protein in the hippocampus in vivo. AAV-APP mutant caused neuronal accumulation of amyloid peptides, and eventually amyloid plaques at 6 months post-injection, but with only marginal hippocampal cell-death. In contrast, AAV-Tau, either wild-type or mutant P301L, provoked dramatic degeneration of pyramidal neurons in CA1/2 and cortex within weeks. Tau-mediated neurodegeneration proceeded without formation of large fibrillar tau-aggregates or tangles, but with increased expression of cell-cycle markers.We present novel AAV-based models, which demonstrate that protein tau mediates pyramidal neurodegeneration in vivo. The data firmly support the unifying hypothesis that post-mitotic neurons are forced to re-enter the cell-cycle in primary and secondary tauopathies, including Alzheimer's disease.

    PloS one 2009;4;10;e7280

  • Plasma beta-amyloid 1-40 is associated with the diffuse small vessel disease subtype.

    Gomis M, Sobrino T, Ois A, Millán M, Rodríguez-Campello A, Pérez de la Ossa N, Rodríguez-González R, Jiménez-Conde J, Cuadrado-Godia E, Roquer J and Dávalos A

    Stroke Unit, Department of Neurociences, Hospital Universitari Germans Trias i Pujol (Badalona), Universitat Autònoma de Barcelona, Barcelona, Spain. mgomis.germanstrias@gencat.cat

    The underlying mechanisms of small vessel disease (SVD) subtypes are diffuse arteriopathy (diffuse-SVD) or microatheroma (focal-SVD). Endothelial dysfunction by beta-amyloid peptide (Abeta) deposition has been associated with lacunar infarcts and leukoaraiosis, but its specific relationship with SVD subtypes is unknown. We hypothesized that plasma Abeta levels can play a different role in SVD subtypes in patients with acute lacunar stroke.

    Methods: We studied 149 patients with acute ischemic stroke of SVD etiology according to Trial Of Org 10172 In Acute Stroke Treatment criteria and 25 age-matched control subjects. Patients were classified into focal-SVD: 39 patients with isolated lacunar infarct without leukoaraiosis and diffuse-SVD: 110 patients with an isolated lacunar infarct with leukoaraiosis or with multiple lacunar infarcts with or without leukoaraiosis. Baseline data included vascular risk factors and extensive laboratory tests, including plasma Abeta levels.

    Results: Median [quartiles] Abeta(1-40) levels (40.4 [35.1, 50.5] versus 55.1 [42.3, 69.6] pg/mL), but not Abeta(1-42) levels, were significantly higher in the diffuse-SVD group than in focal-SVD group (P<0.001) and control subjects (P<0.001). No differences in Abeta(1-40) levels were found between focal-SVD and control subjects. Logistic regression analysis showed that age (OR, 1.06; 95% CI, 1.01 to 1.12), history of hypertension (OR, 3.5; 95% CI, 1.3 to 9.2), and plasma beta-amyloid(1-40) levels over the median value (OR, 17.3; 95% CI, 3.0 to 99 for the third quartile and OR, 6.0; 95% CI, 1.6 to 23 for the fourth quartile) were independently associated with the diffuse-SVD subtype.

    Conclusions: Plasma beta-amyloid(1-40) levels are independently associated with the diffuse-SVD subtype. These results are consistent with the pathophysiological role of fraction Abeta(1-40) in disrupting endothelial vascular function.

    Stroke 2009;40;10;3197-201

  • Vascular endothelial growth factor (VEGF) affects processing of amyloid precursor protein and beta-amyloidogenesis in brain slice cultures derived from transgenic Tg2576 mouse brain.

    Bürger S, Noack M, Kirazov LP, Kirazov EP, Naydenov CL, Kouznetsova E, Yafai Y and Schliebs R

    Paul Flechsig Institute for Brain Research, University of Leipzig, Germany.

    The up-regulation of the angiogenic vascular endothelial growth factor (VEGF) in brains of Alzheimer patients in close relationship to beta-amyloid (Abeta) plaques, suggests a link of VEGF action and processing of the amyloid precursor protein (APP). To reveal whether VEGF may affect APP processing, brain slices derived from 17-month-old transgenic Tg2576 mice were exposed with 1ng/ml VEGF for 6, 24, and 72h, followed by assessing cytosolic and membrane-bound APP expression, level of both soluble and fibrillar Abeta-peptides, as well as activities of alpha- and beta-secretases in brain slice tissue preparations. Treatment of brain slices with VEGF did not significantly affect the expression level of APP, regardless of the exposure time studied. In contrast, VEGF exposure of brain slices for 6h reduced the formation of soluble, SDS extractable Abeta(1-40) and Abeta(1-42) as compared to brain slice cultures incubated in the absence of any drug, while the fibrillar Abeta peptides did not change significantly. This effect was less pronounced 24h after VEGF exposure, but was no longer detectable when brain slices were exposed by VEGF for 72h, which indicates an adaptive response to chronic VEGF exposure. The VEGF-mediated reduction in Abeta formation was accompanied by a transient decrease in beta-secretase activity peaking 6h after VEGF exposure. To reveal whether the VEGF-induced changes in soluble Abeta-level may be due to actions of VEGF on Abeta fibrillogenesis, the fibrillar status of Abeta was examined using the thioflavin-T binding assay. Incubation of Abeta preparations obtained from Tg2576 mouse brain cortex, in the presence of VEGF slightly decreased the fibrillar content with increasing incubation time up to 72h. The data demonstrate that VEGF may affect APP processing, at least in vitro, suggesting a role of VEGF in the pathogenesis of Alzheimer's disease.

    International journal of developmental neuroscience : the official journal of the International Society for Developmental Neuroscience 2009;27;6;517-23

  • Intracellular amyloid beta interacts with SOD1 and impairs the enzymatic activity of SOD1: implications for the pathogenesis of amyotrophic lateral sclerosis.

    Yoon EJ, Park HJ, Kim GY, Cho HM, Choi JH, Park HY, Jang JY, Rhim HS and Kang SM

    School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.

    Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease caused by the degeneration of motor neurons. Mutations in Cu/Zn superoxide dismutase (SOD1), including G93A, were reportedly linked to familial ALS. SOD1 is a key antioxidant enzyme, and is also one of the major targets for oxidative damage in the brains of patients suffering from Alzheimers disease (AD). Several lines of evidence suggest that intracellular amyloid beta (Abeta) is associated with the pathogenesis of AD. In this report we demonstrate that intracellular Abeta directly interacts with SOD1, and that this interaction decreases the enzymatic activity of the enzyme. We observed Abeta-SOD1 aggregates in the perinuclear region of H4 cells, and mapped the SOD1 binding region to Abeta amino acids 26-42. Interestingly, intracellular Ab binds to the SOD1 G93A mutant with greater affinity than to wild-type SOD1. This resulted in considerably less mutant enzymatic activity. Our study implicates a potential role for Abeta in the development of ALS by interacting with the SOD1 G93A mutant.

    Experimental & molecular medicine 2009;41;9;611-7

  • Presynaptic and postsynaptic interaction of the amyloid precursor protein promotes peripheral and central synaptogenesis.

    Wang Z, Wang B, Yang L, Guo Q, Aithmitti N, Songyang Z and Zheng H

    Huffington Center on Aging, Baylor College of Medicine, Houston, Texas 77030, USA.

    A critical role of the amyloid precursor protein (APP) in Alzheimer's disease (AD) pathogenesis has been well established. However, the physiological function of APP remains elusive and much debated. We reported previously that the APP family of proteins is essential in mediating the developing neuromuscular synapse. In the current study, we created a conditional allele of APP and deleted APP in presynaptic motor neuron or postsynaptic muscle. Crossing these alleles onto the APP-like protein 2-null background reveals that, unexpectedly, inactivating APP in either compartment results in neuromuscular synapse defects similar to the germline deletion and that postsynaptic APP is obligatory for presynaptic targeting of the high-affinity choline transporter and synaptic transmission. Using a HEK293 and primary hippocampus mixed-culture assay, we report that expression of APP in HEK293 cells potently promotes synaptogenesis in contacting axons. This activity is dependent on neuronal APP and requires both the extracellular and intracellular domains; the latter forms a complex with Mint1 and Cask and is replaceable by the corresponding SynCAM (synaptic cell adhesion molecule) sequences. These in vitro and in vivo studies identify APP as a novel synaptic adhesion molecule. We postulate that transsynaptic APP interaction modulates its synaptic function and that perturbed APP synaptic adhesion activity may contribute to synaptic dysfunction and AD pathogenesis.

    Funded by: NIA NIH HHS: AG032051, AG033467, R01 AG032051, R01 AG032051-01, R01 AG032051-02, R01 AG033467, R01 AG033467-01; NICHD NIH HHS: HD024064, P30 HD024064

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;35;10788-801

  • Parkin promotes intracellular Abeta1-42 clearance.

    Burns MP, Zhang L, Rebeck GW, Querfurth HW and Moussa CE

    Department of Neuroscience, Georgetown University School of Medicine, Washington, DC 20057, USA.

    Alzheimer's disease and Parkinson's disease are common neurodegenerative diseases that may share some underlying mechanisms of pathogenesis. Abeta(1-42) fragments are found intracellularly, and extracellularly as amyloid plaques, in Alzheimer's disease and in dementia with Lewy Bodies. Parkin is an E3-ubiquitin ligase involved in proteasomal degradation of intracellular proteins. Mutations in parkin, which result in loss of parkin function, lead to early onset Parkinsonism. Here we tested whether the ubiquitin ligase activity of parkin could lead to reduction in intracellular human Abeta(1-42). Lentiviral constructs encoding either human parkin or human Abeta(1-42) were used to infect M17 neuroblastoma cells. Parkin expression resulted in reduction of intracellular human Abeta(1-42) levels and protected against its toxicity in M17 cells. Co-injection of lentiviral constructs into control rat primary motor cortex demonstrated that parkin co-expression reduced human Abeta(1-42) levels and Abeta(1-42)-induced neuronal degeneration in vivo. Parkin increased proteasomal activity, and proteasomal inhibition blocked the effects of parkin on reducing Abeta(1-42) levels. Incubation of Abeta(1-42) cell lysates with ubiquitin, in the presence of parkin, demonstrated the generation of Abeta-ubiquitin complexes. These data indicate that parkin promotes ubiquitination and proteasomal degradation of intracellular Abeta(1-42) and demonstrate a protective effect in neurodegenerative diseases with Abeta deposits.

    Funded by: NIA NIH HHS: NIA-KO1 AG30378

    Human molecular genetics 2009;18;17;3206-16

  • A highly insoluble state of Abeta similar to that of Alzheimer's disease brain is found in Arctic APP transgenic mice.

    Philipson O, Hammarström P, Nilsson KP, Portelius E, Olofsson T, Ingelsson M, Hyman BT, Blennow K, Lannfelt L, Kalimo H and Nilsson LN

    Department of Public Health and Caring Science, Uppsala University, Sweden.

    Amyloid-beta (Abeta) is a major drug target in Alzheimer's disease. Here, we demonstrate that deposited Abeta is SDS insoluble in tgAPP-ArcSwe, a transgenic mouse model harboring the Arctic (E693G) and Swedish (KM670/671NL) APP mutations. Formic acid was needed to extract the majority of deposited Abeta in both tgAPP-ArcSwe and Alzheimer's disease brain, but not in a commonly used type of mouse model with the Swedish mutation alone. Interestingly, the insoluble state of Arctic Abeta was determined early on and did not gradually evolve with time. In tgAPP-ArcSwe, Abeta plaques displayed a patchy morphology with bundles of Abeta fibrils, whereas amyloid cores in tgAPP-Swe were circular with radiating fibrils. Amyloid was more densely stacked in tgAPP-ArcSwe, as demonstrated with a conformation sensitive probe. A reduced increase in plasma Abeta was observed following acute administration of an Abeta antibody in tgAPP-ArcSwe, results that might imply reduced brain to plasma Abeta efflux. TgAPP-ArcSwe, with its insoluble state of deposited Abeta, could serve as a complementary model to better predict the outcome of clinical trials.

    Neurobiology of aging 2009;30;9;1393-405

  • Amyloid-beta precursor protein mediates neuronal toxicity of amyloid beta through Go protein activation.

    Sola Vigo F, Kedikian G, Heredia L, Heredia F, Añel AD, Rosa AL and Lorenzo A

    Instituto de Investigación Médica- CONICET, Córdoba, Argentina.

    Amyloid beta (Abeta) is a metabolic product of amyloid-beta precursor protein (APP). Deposition of Abeta in the brain and neuronal degeneration are characteristic hallmarks of Alzheimer's disease (AD). Abeta induces neuronal degeneration, but the mechanism of neurotoxicity remains elusive. Here we show that overexpression of APP renders hippocampal neurons vulnerable to Abeta toxicity. Deletion of the extracellular Abeta sequence of APP prevents binding of APP to Abeta, and abolishes toxicity. Abeta toxicity is also abrogated by deletion of the cytoplasmic domain of APP, or by deletions comprising the Go protein-binding sequence of APP. Treatment with Pertussis toxin (PTX) abrogates APP-dependent toxicity of Abeta. Overexpression of PTX-insensitive Galpha-o subunit, but not Galpha-i subunit, of G protein restores Abeta toxicity in the presence of PTX, and this requires the integrity of APP-binding site for Go protein. Altogether, these experiments indicate that interaction of APP with toxic Abeta-species promotes toxicity in hippocampal neurons by a mechanism that involves APP-mediated Go protein activation, revealing an Abeta-receptor-like function of APP directly implicated in neuronal degeneration in AD.

    Neurobiology of aging 2009;30;9;1379-92

  • Gamma-secretase-dependent cleavage of amyloid precursor protein regulates osteoblast behavior.

    McLeod J, Curtis N, Lewis HD, Good MA, Fagan MJ and Genever PG

    Department of Biology, University of York, York, UK.

    gamma-Secretase cleaves amyloid precursor protein (APP) to generate amyloid-beta (Abeta) peptides, which aggregate in the brain in Alzheimer's disease (AD). gamma-Secretase also cleaves molecules that regulate osteoblast activity, such as Notch and ephrinB2. However, the role of APP in bone is unknown. In this study, the expression, cleavage, and function of APP were investigated during osteogenesis in vitro and in vivo. Expression of all gamma-secretase subunits was confirmed in human primary osteoprogenitors cells, and a significant increase in enzyme activity was observed during osteogenic differentiation using a specific fluorimetric assay. Application of selective inhibitors confirmed gamma-secretase-dependent cleavage of APP within osteogenic cells, and secretion of Abeta by mature osteoblasts was demonstrated with the use of a chemiluminescent immunoassay. Osteoprogenitors showed a selective and significant increase in adhesion to extracellular matrices containing aged Abeta plaques compared with nonaged Abeta peptide controls. Abeta on the endosteal and periosteal surfaces of adult rat ulnae were identified by immunohistochemistry. MicroCT analysis of vertebrae from an AD mouse model, Tg2576, identified a decrease in bone volume, surface area, and thickness compared with wild-type controls. These findings indicate that APP functions as a novel regulator of osteoblast activity and suggest that the mechanisms underlying the pathogenesis of AD may also influence bone.

    Funded by: Medical Research Council: G9724886

    FASEB journal : official publication of the Federation of American Societies for Experimental Biology 2009;23;9;2942-55

  • Amino acid position-specific contributions to amyloid beta-protein oligomerization.

    Maji SK, Ogorzalek Loo RR, Inayathullah M, Spring SM, Vollers SS, Condron MM, Bitan G, Loo JA and Teplow DB

    Department of Neurology, UCLA, Los Angeles, California 90095, USA.

    Understanding the structural and assembly dynamics of the amyloid beta-protein (Abeta) has direct relevance to the development of therapeutic agents for Alzheimer disease. To elucidate these dynamics, we combined scanning amino acid substitution with a method for quantitative determination of the Abeta oligomer frequency distribution, photo-induced cross-linking of unmodified proteins (PICUP), to perform "scanning PICUP." Tyr, a reactive group in PICUP, was substituted at position 1, 10, 20, 30, or 40 (for Abeta40) or 42 (for Abeta42). The effects of these substitutions were probed using circular dichroism spectroscopy, thioflavin T binding, electron microscopy, PICUP, and mass spectrometry. All peptides displayed a random coil --> alpha/beta --> beta transition, but substitution-dependent alterations in assembly kinetics and conformer complexity were observed. Tyr(1)-substituted homologues of Abeta40 and Abeta42 assembled the slowest and yielded unusual patterns of oligomer bands in gel electrophoresis experiments, suggesting oligomer compaction had occurred. Consistent with this suggestion was the observation of relatively narrow [Tyr(1)]Abeta40 fibrils. Substitution of Abeta40 at the C terminus decreased the population conformational complexity and substantially extended the highest order of oligomers observed. This latter effect was observed in both Abeta40 and Abeta42 as the Tyr substitution position number increased. The ability of a single substitution (Tyr(1)) to alter Abeta assembly kinetics and the oligomer frequency distribution suggests that the N terminus is not a benign peptide segment, but rather that Abeta conformational dynamics and assembly are affected significantly by the competition between the N and C termini to form a stable complex with the central hydrophobic cluster.

    Funded by: NCRR NIH HHS: RR020004; NIA NIH HHS: AG018921, AG027818

    The Journal of biological chemistry 2009;284;35;23580-91

  • Measurement of amyloid fibril mass-per-length by tilted-beam transmission electron microscopy.

    Chen B, Thurber KR, Shewmaker F, Wickner RB and Tycko R

    Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.

    We demonstrate that accurate values of mass-per-length (MPL), which serve as strong constraints on molecular structure, can be determined for amyloid fibrils by quantification of intensities in dark-field electron microscope images obtained in the tilted-beam mode of a transmission electron microscope. MPL values for fibrils formed by residues 218-289 of the HET-s fungal prion protein, for 2-fold- and 3-fold-symmetric fibrils formed by the 40-residue beta-amyloid peptide, and for fibrils formed by the yeast prion protein Sup35NM are in good agreement with previous results from scanning transmission electron microscopy. Results for fibrils formed by the yeast prion protein Rnq1, for which the MPL value has not been previously reported, support an in-register parallel beta-sheet structure, with one Rnq1 molecule per 0.47-nm beta-sheet repeat spacing. Since tilted-beam dark-field images can be obtained on many transmission electron microscopes, this work should facilitate MPL determination by a large number of research groups engaged in studies of amyloid fibrils and similar supramolecular assemblies.

    Funded by: Intramural NIH HHS

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;34;14339-44

  • Ternary complexes of iron, amyloid-beta, and nitrilotriacetic acid: binding affinities, redox properties, and relevance to iron-induced oxidative stress in Alzheimer's disease.

    Jiang D, Li X, Williams R, Patel S, Men L, Wang Y and Zhou F

    Department of Chemistry and Biochemistry, California State University, Los Angeles, California 90032, USA.

    The interaction of amyloid-beta (Abeta) and redox-active metals, two important biomarkers present in the senile plaques of Alzheimer's disease (AD) brain, has been suggested to enhance the Abeta aggregation or facilitate the generation of reactive oxygen species (ROS). This study investigates the nature of the interaction between the metal-binding domain of Abeta, viz., Abeta(1-16), and the Fe(III) or Fe(II) complex with nitrilotriacetic acid (NTA). Using electrospray ionization mass spectrometry (ESI-MS), the formation of a ternary complex of Abeta(1-16), Fe(III), and NTA with a stoichiometry of 1:1:1 was identified. MS also revealed that the NTA moiety can be detached via collision-induced dissociation. The cumulative dissociation constants of both Abeta-Fe(III)-NTA and Abeta-Fe(II)-NTA complexes were deduced to be 6.3 x 10(-21) and 5.0 x 10(-12) M(2), respectively, via measurement of the fluorescence quenching of the sole tyrosine residue on Abeta upon formation of the complex. The redox properties of these two complexes were investigated by cyclic voltammetry. The redox potential of the Abeta-Fe(III)-NTA complex was found to be 0.03 V versus Ag/AgCl, which is negatively shifted by 0.54 V when compared to the redox potential of free Fe(III)/Fe(II). Despite such a large potential modulation, the redox potential of the Abeta-Fe(III)-NTA complex is still sufficiently high for a range of redox reactions with cellular species to occur. The Abeta-Fe(II)-NTA complex electrogenerated from the Abeta-Fe(III)-NTA complex was also found to catalyze the reduction of oxygen to produce H(2)O(2). These findings provide significant insight into the role of iron and Abeta in the development of AD. The binding of iron by Abeta modulates the redox potential to a level at which its redox cycling occurs. In the presence of a biological reductant (antioxidant), redox cycling of iron could disrupt the redox balance within the cellular milieu. As a consequence, not only is ROS continuously produced, but oxygen and biological reductants can also be depleted. A cascade of biological processes can therefore be affected. In addition, the strong binding affinity of Abeta toward Fe(III) and Fe(II) indicates Abeta could compete for iron against other iron-containing proteins. In particular, its strong affinity for Fe(II), which is 8 orders of magnitude stronger than that of transferrin, would greatly interfere with iron homeostasis.

    Funded by: NCI NIH HHS: R01 CA 101864, R01 CA 116522, R01 CA101864; NIGMS NIH HHS: GM 08101, S06 GM008101, S06 GM008101-360068; NIMHD NIH HHS: P20 MD001824, P20 MD001824-01

    Biochemistry 2009;48;33;7939-47

  • The repeat domain of the melanosome fibril protein Pmel17 forms the amyloid core promoting melanin synthesis.

    McGlinchey RP, Shewmaker F, McPhie P, Monterroso B, Thurber K and Wickner RB

    Laboratorie of Biochemistry, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0830, USA.

    Pmel17 is a melanocyte protein necessary for eumelanin deposition 1 in mammals and found in melanosomes in a filamentous form. The luminal part of human Pmel17 includes a region (RPT) with 10 copies of a partial repeat sequence, pt.e.gttp.qv., known to be essential in vivo for filament formation. We show that this RPT region readily forms amyloid in vitro, but only under the mildly acidic conditions typical of the lysosome-like melanosome lumen, and the filaments quickly become soluble at neutral pH. Under the same mildly acidic conditions, the Pmel filaments promote eumelanin formation. Electron diffraction, circular dichroism, and solid-state NMR studies of Pmel17 filaments show that the structure is rich in beta sheet. We suggest that RPT is the amyloid core domain of the Pmel17 filaments so critical for melanin formation.

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;33;13731-6

  • Paradoxical condensation of copper with elevated beta-amyloid in lipid rafts under cellular copper deficiency conditions: implications for Alzheimer disease.

    Hung YH, Robb EL, Volitakis I, Ho M, Evin G, Li QX, Culvenor JG, Masters CL, Cherny RA and Bush AI

    Oxidation Biology Laboratory, The Mental Health Research Institute of Victoria, Parkville, Victoria, Australia.

    Redox-active copper is implicated in the pathogenesis of Alzheimer disease (AD), beta-amyloid peptide (Abeta) aggregation, and amyloid formation. Abeta.copper complexes have been identified in AD and catalytically oxidize cholesterol and lipid to generate H2O2 and lipid peroxides. The site and mechanism of this abnormality is not known. Growing evidence suggests that amyloidogenic processing of the beta-amyloid precursor protein (APP) occurs in lipid rafts, membrane microdomains enriched in cholesterol. beta- and gamma-secretases, and Abeta have been identified in lipid rafts in cultured cells, human and rodent brains, but the role of copper in lipid raft amyloidogenic processing is presently unknown. In this study, we found that copper modulates flotillin-2 association with cholesterol-rich lipid raft domains, and consequently Abeta synthesis is attenuated via copper-mediated inhibition of APP endocytosis. We also found that total cellular copper is associated inversely with lipid raft copper levels, so that under intracellular copper deficiency conditions, Abeta.copper complexes are more likely to form. This explains the paradoxical hypermetallation of Abeta with copper under tissue copper deficiency conditions in AD.

    The Journal of biological chemistry 2009;284;33;21899-907

  • Synaptic activity reduces intraneuronal Abeta, promotes APP transport to synapses, and protects against Abeta-related synaptic alterations.

    Tampellini D, Rahman N, Gallo EF, Huang Z, Dumont M, Capetillo-Zarate E, Ma T, Zheng R, Lu B, Nanus DM, Lin MT and Gouras GK

    Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, New York 10065, USA.

    A central question in Alzheimer's disease research is what role synaptic activity plays in the disease process. Synaptic activity has been shown to induce beta-amyloid peptide release into the extracellular space, and extracellular beta-amyloid has been shown to be toxic to synapses. We now provide evidence that the well established synaptotoxicity of extracellular beta-amyloid requires gamma-secretase processing of amyloid precursor protein. Recent evidence supports an important role for intraneuronal beta-amyloid in the pathogenesis of Alzheimer's disease. We show that synaptic activity reduces intraneuronal beta-amyloid and protects against beta-amyloid-related synaptic alterations. We demonstrate that synaptic activity promotes the transport of the amyloid precursor protein to synapses using live cell imaging, and that the protease neprilysin is involved in reduction of intraneuronal beta-amyloid with synaptic activity.

    Funded by: NIA NIH HHS: AG027140, AG028174, AG09464, AG20729, K02 AG028174-01A2, K02 AG028174-02, K02 AG028174-03, R01 AG027140-01A2, R01 AG027140-02; NINDS NIH HHS: R01 NS045677-04, R01 NS045677-05

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;31;9704-13

  • AIP-1 ameliorates beta-amyloid peptide toxicity in a Caenorhabditis elegans Alzheimer's disease model.

    Hassan WM, Merin DA, Fonte V and Link CD

    Institute for Behavioral Genetics, University of Colorado at Boulder, Boulder, CO 80303, USA. whassan@unmc.edu

    Multiple neurodegenerative diseases are causally linked to aggregation-prone proteins. Cellular mechanisms involving protein turnover may be key defense mechanisms against aggregating protein disorders. We have used a transgenic Caenorhabditis elegans Alzheimer's disease model to identify cellular responses to proteotoxicity resulting from expression of the human beta amyloid peptide (Abeta). We show up-regulation of aip-1 in Abeta-expressing animals. Mammalian homologues of AIP-1 have been shown to associate with, and regulate the function of, the 26S proteasome, leading us to hypothesize that induction of AIP-1 may be a protective cellular response directed toward modulating proteasomal function in response to toxic protein aggregation. Using our transgenic model, we show that overexpression of AIP-1 protected against, while RNAi knockdown of AIP-1 exacerbated, Abeta toxicity. AIP-1 overexpression also reduced accumulation of Abeta in this model, which is consistent with AIP-1 enhancing protein degradation. Transgenic expression of one of the two human aip-1 homologues (AIRAPL), but not the other (AIRAP), suppressed Abeta toxicity in C. elegans, which advocates the biological relevance of the data to human biology. Interestingly, AIRAPL and AIP-1 contain a predicted farnesylation site, which is absent from AIRAP. This farnesylation site was shown by others to be essential for an AIP-1 prolongevity function. Consistent with this, we show that an AIP-1 mutant lacking the predicted farnesylation site failed to protect against Abeta toxicity. Our results implicate AIP-1 in the regulation of protein turnover and protection against Abeta toxicity and point at AIRAPL as the functional mammalian homologue of AIP-1.

    Funded by: NIA NIH HHS: AG12423, R01 AG012423, R01 AG012423-04, R01 AG012423-05, R01 AG012423-06, R01 AG012423-06S1

    Human molecular genetics 2009;18;15;2739-47

  • CD40/CD40L interaction induces Abeta production and increases gamma-secretase activity independently of tumor necrosis factor receptor associated factor (TRAF) signaling.

    Volmar CH, Ait-Ghezala G, Frieling J, Weeks OI and Mullan MJ

    Roskamp Institute, Division of Genomics and Molecular Biology, Sarasota, Fl 34243, USA.

    CD40, a member of tumor necrosis factor receptor superfamily, and its cognate ligand CD40L are both elevated in the brain of Alzheimer's disease (AD) patients compared to controls. We have shown that pharmacological or genetic interruption of CD40/CD40L interaction results in mitigation of AD-like pathology in vivo in transgenic AD mouse models, and in vitro. Recently, we showed that CD40L stimulation could increase Abeta levels via NFkappaB signaling, presumably through TRAFs. In the present work, using CD40 mutants, we show that CD40L can increase levels of Abeta(1-40), Abeta(1-42), sAPPbeta, sAPPalpha and CTFbeta independently of TRAF signaling. We report an increase in mature/immature APP ratio after CD40L treatment of CD40wt and CD40-mutant cells, reflecting alterations in APP trafficking. In addition, results from CD40L treatment of a neuroblastoma cell line over-expressing the C-99 APP fragment suggest that CD40L has an effect on gamma-secretase. Furthermore, inhibition of gamma-secretase activity significantly reduces sAPPbeta levels in the CD40L treated HEK/APPsw CD40wt and the CD40-mutant cells. The latter suggests CD40/CD40L interaction primarily acts on gamma-secretase and affects beta-secretase via a positive feedback mechanism. Taken together, our data suggest that CD40/CD40L interaction modulates APP processing independently of TRAF signaling.

    Experimental cell research 2009;315;13;2265-74

  • Amyloid precursor protein increases cortical neuron size in transgenic mice.

    Oh ES, Savonenko AV, King JF, Fangmark Tucker SM, Rudow GL, Xu G, Borchelt DR and Troncoso JC

    Department of Medicine, The Johns Hopkins University School of Medicine, 558 Ross Research Building, Baltimore, MD 21205, USA.

    The amyloid precursor protein (APP) is the source of beta-amyloid, a pivotal peptide in the pathogenesis of Alzheimer's disease (AD). This study examines the possible effect of APP transgene expression on neuronal size by measuring the volumes of cortical neurons (microm(3)) in transgenic mouse models with familial AD Swedish mutation (APPswe), with or without mutated presenilin1 (PS1dE9), as well as in mice carrying wild-type APP (APPwt). Overexpression of APPswe and APPwt protein, but not of PS1dE9 alone, resulted in a greater percentage of medium-sized neurons and a proportionate decrease in the percentage of small-sized neurons. Our observations indicate that the overexpression of mutant (APPswe) or wild-type APP in transgenic mice is necessary and sufficient for hypertrophy of cortical neurons. This is highly suggestive of a neurotrophic effect and also raises the possibility that the lack of neuronal loss in transgenic mouse models of AD may be attributed to overexpression of APP.

    Funded by: NIA NIH HHS: P01 AG005146, P50 AG005146-25

    Neurobiology of aging 2009;30;8;1238-44

  • APP and BACE1 miRNA genetic variability has no major role in risk for Alzheimer disease.

    Bettens K, Brouwers N, Engelborghs S, Van Miegroet H, De Deyn PP, Theuns J, Sleegers K and Van Broeckhoven C

    Neurodegenerative Brain Diseases Group, Department of Molecular Genetics, VIB, Antwerp, Belgium.

    Expression levels of the amyloid precursor protein (APP) and beta-site amyloid (Abeta) cleaving enzyme 1 (BACE1) have been implicated in Alzheimer disease (AD) progression. In a well-characterized Belgian group of 358 AD patients and 462 controls, we examined whether genetic variability in microRNA (miRNA) binding sites of APP and BACE1 or in associated miRNAs influenced risk for AD. Direct sequencing identified six variants in the 3' untranslated region (UTR) of APP and 29 variants in the 3' UTR of BACE1, of which few variants were restricted to patients: in APP; 4 variants in 6 patients ( approximately 2%) and in BACE1; 7 variants in 11 patients ( approximately 3.5%). Further genetic screening of the miR-29 cluster encoding the miR-29a/b-1 genes showed 10 variants in close proximity of this cluster. Association studies using all common variants detected in the 3' UTR of BACE1 and the miR-29 gene cluster did not identify an association with AD risk. However, we did observe statistical interaction between rs535860 (BACE1 3' UTR) and rs34772568 (near miR29a; odds ratio [OR](interaction), 0.4; 95% confidence interval [CI], 0.17-0.96; P=0.033). While the exact role of the patient-specific miRNA variants within the 3' UTR region of APP and BACE1 demands further analyses, this study does not support a major contribution of miRNA genetic variability to AD pathogenesis.

    Human mutation 2009;30;8;1207-13

  • Coeliac disease-associated risk variants in TNFAIP3 and REL implicate altered NF-kappaB signalling.

    Trynka G, Zhernakova A, Romanos J, Franke L, Hunt KA, Turner G, Bruinenberg M, Heap GA, Platteel M, Ryan AW, de Kovel C, Holmes GK, Howdle PD, Walters JR, Sanders DS, Mulder CJ, Mearin ML, Verbeek WH, Trimble V, Stevens FM, Kelleher D, Barisani D, Bardella MT, McManus R, van Heel DA and Wijmenga C

    Genetics Department, University Medical Centre, University of Groningen, Groningen, The Netherlands.

    Objective: Our previous coeliac disease genome-wide association study (GWAS) implicated risk variants in the human leucocyte antigen (HLA) region and eight novel risk regions. To identify more coeliac disease loci, we selected 458 single nucleotide polymorphisms (SNPs) that showed more modest association in the GWAS for genotyping and analysis in four independent cohorts.

    Design: 458 SNPs were assayed in 1682 cases and 3258 controls from three populations (UK, Irish and Dutch). We combined the results with the original GWAS cohort (767 UK cases and 1422 controls); six SNPs showed association with p<1 x 10(-04) and were then genotyped in an independent Italian coeliac cohort (538 cases and 593 controls).

    Results: We identified two novel coeliac disease risk regions: 6q23.3 (OLIG3-TNFAIP3) and 2p16.1 (REL), both of which reached genome-wide significance in the combined analysis of all 2987 cases and 5273 controls (rs2327832 p = 1.3 x 10(-08), and rs842647 p = 5.2 x 10(-07)). We investigated the expression of these genes in the RNA isolated from biopsies and from whole blood RNA. We did not observe any changes in gene expression, nor in the correlation of genotype with gene expression.

    Conclusions: Both TNFAIP3 (A20, at the protein level) and REL are key mediators in the nuclear factor kappa B (NF-kappaB) inflammatory signalling pathway. For the first time, a role for primary heritable variation in this important biological pathway predisposing to coeliac disease has been identified. Currently, the HLA risk factors and the 10 established non-HLA risk factors explain approximately 40% of the heritability of coeliac disease.

    Funded by: British Heart Foundation: G0000934; Medical Research Council: G0000934; Wellcome Trust: 068545/Z/02, GR068094MA

    Gut 2009;58;8;1078-83

  • FAD-mutation of APP is associated with a loss of its synaptotrophic activity.

    Seeger G, Gärtner U, Ueberham U, Rohn S and Arendt T

    Department for Molecular and Cellular Mechanisms of Neurodegeneration, Paul Flechsig Institute of Brain Research, University of Leipzig, Jahnallee 59, Leipzig D-04109, Germany.

    Alzheimer's disease (AD) is a chronic neurodegenerative disorder associated with extracellular accumulation of Abeta peptide that derives from the amyloid precursor protein (APP). While amyloidogenic processing of APP has received most attention, the physiological function of APP and the sequelae of potentially impaired APP function are less understood. APP is a transmembrane glycoprotein being widely expressed in neurons in both central and peripheral nervous system. Its physiological function has been associated with neuronal survival, neurite outgrowth and neuronal plasticity. The aim of the present study was to determine whether FAD-linked mutations of APP, known to be associated with early onset of the disease, might impair its synaptotrophic function, potentially contributing to synaptic deficiencies seen in AD. We performed a quantitative electron microscopy study on synapses in well characterized expression-matched transgenic mice lines expressing either wildtype or FAD-mutated hAPP. Using serial electron microscopic sections, we comparatively analyzed by stereological methods the number and sizes of synaptic contacts and the number of synaptic vesicles in the neocortex. We could clearly show a synaptotrophic effect in mice overexpressing wildtype hAPP evidenced by a significant increase in the number of synapses and the number of vesicles per synapse. This effect was abolished when FAD-mutated APP(Sw,Ind) was expressed instead of wildtype APP. The present study demonstrates a synaptotrophic effect of APP which is lost in the presence of a FAD-mutation. This failure could either be due to a synaptotoxic effect of Abeta potentially counteracting the synaptotrophic effect of APP. Alternatively, the FAD-mutation might impair the physiological function of the extracellular domain of APP and its fragments which might be required for the synaptotrophic effect. This suggests that not only "too much Abeta" but also "too less functional intact APP" might be relevant for synaptic pathology and degeneration in AD.

    Neurobiology of disease 2009;35;2;258-63

  • Ganglioside GM1 binding the N-terminus of amyloid precursor protein.

    Zhang H, Ding J, Tian W, Wang L, Huang L, Ruan Y, Lu T, Sha Y and Zhang D

    Institute of Mental Health, Peking University, Key Laboratories for Mental Health, Ministry of Health, Beijing, China.

    Secreted amyloid precursor protein (APPs) plays a role in several neuronal functions, including the promotion of synaptogenesis, neurite outgrowth and neuroprotection. Previous study has demonstrated that ganglioside GM1 inhibits the secretion of APPs; however the underlying mechanism remains unknown. Here we reported that GM1 can bind cellular full length APP and APPs secreted from APP(695) stably-transfected SH-SY5Y cells. To characterize the GM1-APP interaction further, we expressed and purified recombinant fragments of the N-terminal APP. Immunoprecipitation experiments revealed that GM1 was able to bind the recombinant APP(18-81) fragment. Moreover, the synthetic peptide APP(52-81) could inhibit the binding. Therefore, the binding site for GM1 appears to be located within residues 52-81 of APP. Furthermore, we found that only GM1, but not GD1a, GT1b and ceramide, binds APP-N-terminus, indicating that the specific binding depends on the sugar moiety of GM1. Fluorescent studies revealed a decrease in the intrinsic fluorescence intensity of the APP(52-81) peptide in phosphatidylcholine (PC)/GM1 vesicles. By using FTIR techniques, we found that the major secondary structure of the APP(52-81) peptide was altered in PC/GM1 vesicles. Our results demonstrate that GM1 binds the N-terminus of APP and induces a conformational change. These findings suggest that secreted APP is decreased by membrane GM1 binding to its precursor protein and provide a possible molecular mechanism to explain the involvement of GM1 in APP proteolysis and pathogenesis of Alzheimer's disease.

    Neurobiology of aging 2009;30;8;1245-53

  • S655 phosphorylation enhances APP secretory traffic.

    Vieira SI, Rebelo S, Domingues SC, da Cruz e Silva EF and da Cruz e Silva OA

    Centro de Biologia Celular, SACS, Universidade de Aveiro, Portugal.

    Cellular protein phosphorylation regulates proteolytic processing of the Alzheimer's Amyloid Precursor Protein (APP). This appears to occur both indirectly and directly via APP phosphorylation at residues within cytoplasmic motifs related to targeting and protein-protein interactions. The sorting signal (653)YTSI(656) comprises the S655 residue that can be phosphorylated by PKC, particularly in mature APP molecules. The YTSI domain has been associated with APP internalization and Golgi polarized sorting, but no functional significance has been attributed to S655 phosphorylation thus far. Using APP(695)-GFP S655 phosphomutants we show that S655 phosphorylation is a signal that positively modulates APP secretory traffic. The phosphomimicking and dephosphomimicking S655 mutants exhibited contrasting Golgi dynamics, which correlated with differential Golgi vesicular exit and secretory cleavage to sAPP. The role of S655 phosphorylation in APP trafficking at sorting stations, such as the Golgi, its contribution toward cytoprotective alpha sAPP production, and implications for Alzheimer's disease are discussed.

    Molecular and cellular biochemistry 2009;328;1-2;145-54

  • The clathrin assembly protein AP180 regulates the generation of amyloid-beta peptide.

    Wu F, Matsuoka Y, Mattson MP and Yao PJ

    Laboratory of Neurosciences, NIA/NIH Biomedical Research Center, Baltimore, MD 21224, USA.

    The overproduction and extracellular buildup of amyloid-beta peptide (Abeta) is a critical step in the etiology of Alzheimer's disease. Recent data suggest that intracellular trafficking is of central importance in the production of Abeta. Here we use a neuronal cell line to examine two structurally similar clathrin assembly proteins, AP180 and CALM. We show that RNA interference-mediated knockdown of AP180 reduces the generation of Abeta1-40 and Abeta1-42, whereas CALM knockdown has no effect on Abeta generation. Thus AP180 is among the traffic controllers that oversee and regulate amyloid precursor protein processing pathways. Our results also suggest that AP180 and CALM, while similar in their domain structures and biochemical properties, are in fact dedicated to separate trafficking pathways in neurons.

    Funded by: Intramural NIH HHS: Z01 AG000314-07, Z01 AG000317-07; NIA NIH HHS: K01 AG022455, K01AG022455, R01 AG026478, R01AG026478

    Biochemical and biophysical research communications 2009;385;2;247-50

  • Antiparallel beta-sheet: a signature structure of the oligomeric amyloid beta-peptide.

    Cerf E, Sarroukh R, Tamamizu-Kato S, Breydo L, Derclaye S, Dufrêne YF, Narayanaswami V, Goormaghtigh E, Ruysschaert JM and Raussens V

    Center for Structural Biology and Bioinformatics, Laboratory for Structure and Function of Biological Membranes, Faculté des Sciences, Université Libre de Bruxelles, CP 206/2, Blvd. du Triomphe, B-1050 Brussels, Belgium.

    AD (Alzheimer's disease) is linked to Abeta (amyloid beta-peptide) misfolding. Studies demonstrate that the level of soluble Abeta oligomeric forms correlates better with the progression of the disease than the level of fibrillar forms. Conformation-dependent antibodies have been developed to detect either Abeta oligomers or fibrils, suggesting that structural differences between these forms of Abeta exist. Using conditions which yield well-defined Abeta-(1-42) oligomers or fibrils, we studied the secondary structure of these species by ATR (attenuated total reflection)-FTIR (Fourier-transform infrared) spectroscopy. Whereas fibrillar Abeta was organized in a parallel beta-sheet conformation, oligomeric Abeta displayed distinct spectral features, which were attributed to an antiparallel beta-sheet structure. We also noted striking similarities between Abeta oligomers spectra and those of bacterial outer membrane porins. We discuss our results in terms of a possible organization of the antiparallel beta-sheets in Abeta oligomers, which may be related to reported effects of these highly toxic species in the amyloid pathogenesis associated with AD.

    The Biochemical journal 2009;421;3;415-23

  • Insulin receptor dysfunction impairs cellular clearance of neurotoxic oligomeric a{beta}.

    Zhao WQ, Lacor PN, Chen H, Lambert MP, Quon MJ, Krafft GA and Klein WL

    Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA. wei-qin_zhao@merck.com

    Accumulation of amyloid beta (Abeta) oligomers in the brain is toxic to synapses and may play an important role in memory loss in Alzheimer disease. However, how these toxins are built up in the brain is not understood. In this study we investigate whether impairments of insulin and insulin-like growth factor-1 (IGF-1) receptors play a role in aggregation of Abeta. Using primary neuronal culture and immortal cell line models, we show that expression of normal insulin or IGF-1 receptors confers cells with abilities to reduce exogenously applied Abeta oligomers (also known as ADDLs) to monomers. In contrast, transfection of malfunctioning human insulin receptor mutants, identified originally from patient with insulin resistance syndrome, or inhibition of insulin and IGF-1 receptors via pharmacological reagents increases ADDL levels by exacerbating their aggregation. In healthy cells, activation of insulin and IGF-1 receptor reduces the extracellular ADDLs applied to cells via seemingly the insulin-degrading enzyme activity. Although insulin triggers ADDL internalization, IGF-1 appears to keep ADDLs on the cell surface. Nevertheless, both insulin and IGF-1 reduce ADDL binding, protect synapses from ADDL synaptotoxic effects, and prevent the ADDL-induced surface insulin receptor loss. Our results suggest that dysfunctions of brain insulin and IGF-1 receptors contribute to Abeta aggregation and subsequent synaptic loss.

    Funded by: Intramural NIH HHS; NIA NIH HHS: R01 AG022547, R01-AG022547

    The Journal of biological chemistry 2009;284;28;18742-53

  • Influence of residue 22 on the folding, aggregation profile, and toxicity of the Alzheimer's amyloid beta peptide.

    Perálvarez-Marín A, Mateos L, Zhang C, Singh S, Cedazo-Mínguez A, Visa N, Morozova-Roche L, Gräslund A and Barth A

    Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden. apm@dbb.su.se

    Several biophysical techniques have been used to determine differences in the aggregation profile (i.e., the secondary structure, aggregation propensity, dynamics, and morphology of amyloid structures) and the effects on cell viability of three variants of the amyloid beta peptide involved in Alzheimer's disease. We focused our study on the Glu22 residue, comparing the effects of freshly prepared samples and samples aged for at least 20 days. In the aged samples, a high propensity for aggregation and beta-sheet secondary structure appears when residue 22 is capable of establishing polar (Glu22 in wild-type) or hydrophobic (Val22 in E22V) interactions. The Arctic variant (E22G) presents a mixture of mostly disordered and alpha-helix structures (with low beta-sheet contribution). Analysis of transmission electron micrographs and atomic force microscopy images of the peptide variants after aging showed significant quantitative and qualitative differences in the morphology of the formed aggregates. The effect on human neuroblastoma cells of these Abeta(12-28) variants does not correlate with the amount of beta-sheet of the aggregates. In samples allowed to age, the native sequence was found to have an insignificant effect on cell viability, whereas the Arctic variant (E22G), the E22V variant, and the slightly-aggregating control (F19G-F20G) had more prominent effects.

    Biophysical journal 2009;97;1;277-85

  • Evidence for novel beta-sheet structures in Iowa mutant beta-amyloid fibrils.

    Tycko R, Sciarretta KL, Orgel JP and Meredith SC

    Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, USA.

    Asp23-to-Asn mutation within the coding sequence of beta-amyloid, called the Iowa mutation, is associated with early onset, familial Alzheimer's disease and cerebral amyloid angiopathy, in which patients develop neuritic plaques and massive vascular deposition predominantly of the mutant peptide. We examined the mutant peptide, D23N-Abeta40, by electron microscopy, X-ray diffraction, and solid-state NMR spectroscopy. D23N-Abeta40 forms fibrils considerably faster than the wild-type peptide (k = 3.77 x 10(-3) min(-1) and 1.07 x 10(-4) min(-1) for D23N-Abeta40 and the wild-type peptide WT-Abeta40, respectively) and without a lag phase. Electron microscopy shows that D23N-Abeta40 forms fibrils with multiple morphologies. X-ray fiber diffraction shows a cross-beta pattern, with a sharp reflection at 4.7 A and a broad reflection at 9.4 A, which is notably smaller than the value for WT-Abeta40 fibrils (10.4 A). Solid-state NMR measurements indicate molecular level polymorphism of the fibrils, with only a minority of D23N-Abeta40 fibrils containing the in-register, parallel beta-sheet structure commonly found in WT-Abeta40 fibrils and most other amyloid fibrils. Antiparallel beta-sheet structures in the majority of fibrils are indicated by measurements of intermolecular distances through (13)C-(13)C and (15)N-(13)C dipole-dipole couplings. An intriguing possibility exists that there is a relationship between the aberrant structure of D23N-Abeta40 fibrils and the unusual vasculotropic clinical picture in these patients.

    Funded by: NCRR NIH HHS: RR-08630; NHLBI NIH HHS: HL07237; NIDDK NIH HHS: Z01 DK029061-02; NINDS NIH HHS: NS042852, R01 NS042852-06A2

    Biochemistry 2009;48;26;6072-84

  • A transgenic rat model of Alzheimer's disease with extracellular Abeta deposition.

    Flood DG, Lin YG, Lang DM, Trusko SP, Hirsch JD, Savage MJ, Scott RW and Howland DS

    Department of CNS Biology, Discovery Research, Cephalon, Inc., West Chester, PA 19380, USA. dflood@cephalon.com

    Many transgenic mouse models of Alzheimer's disease (AD) that deposit amyloid (Abeta) have been produced, but development of an Abeta-depositing rat model has not been successful. Here, we describe a rat model with extracellular fibrillar Abeta deposition. Two lines of Sprague Dawley rats with transgenes expressing human amyloid precursor protein (APP) with the familial AD (FAD) mutations K670N/M671L and K670N/M671L/V717I were crossed. Abeta production in the double homozygous rats was sufficient for deposition by 17-18 months of age. The age of onset of Abeta deposition was reduced by crossing in a third rat line carrying a human presenilin-1 (PS-1) transgene with the FAD M146V mutation. The triple homozygous line had an onset of Abeta deposition by 7 months of age. Deposits appeared similar to those observed in the mouse models and displayed surrounding glial and phosphorylated tau reactivity. Abeta levels measured by ELISA were comparable to those reported in mouse models, suggesting that substantially greater amounts of soluble Abeta are not required in the rat to generate Abeta deposition.

    Neurobiology of aging 2009;30;7;1078-90

  • ABAD: a potential therapeutic target for Abeta-induced mitochondrial dysfunction in Alzheimer's disease.

    Marques AT, Fernandes PA and Ramos MJ

    REQUIMTE, Departamento de Química, Faculdade de Ci ências, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.

    Amyloid-beta-peptide (Abetabinding to mitochondrial Abeta-binding alcohol dehydrogenase (ABAD) enzyme triggers a series of events leading to mitochondrial dysfunction characteristic of Alzheimer's disease (AD). Thus this interaction may represent a novel target for treatment strategy against AD. In this review we summarize current findings regarding the ABAD-Abeta interaction, namely structural and biophysical data, available inhibitors and more recent data from proteomic studies.

    Mini reviews in medicinal chemistry 2009;9;8;1002-8

  • Abeta43 is more frequent than Abeta40 in amyloid plaque cores from Alzheimer disease brains.

    Welander H, Frånberg J, Graff C, Sundström E, Winblad B and Tjernberg LO

    Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Dainippon Sumitomo Pharma Alzheimer Center, Novum, Huddinge, Sweden. hedvig.welander@ki.se

    One hallmark of Alzheimer disease (AD) is the extracellular deposition of the amyloid beta-peptide (Abeta) in senile plaques. Two major forms of Abeta are produced, 40 (Abeta40) and 42 (Abeta42) residues long. The most abundant form of Abeta is Abeta40, while Abeta42 is more hydrophobic and more prone to form toxic oligomers and the species of particular importance in early plaque formation. Thus, the length of the hydrophobic C-terminal seems to be very important for the oligomerization and neurotoxicity of the Abeta peptide. Here we investigated which Abeta species are deposited in AD brain. We analyzed plaque cores, prepared from occipital and frontal cortex, from sporadic and familial AD cases and performed a quantitative study using Abeta standard peptides. Cyanogen bromide was used to generate C-terminal Abeta fragments, which were analyzed by HPLC coupled to an electrospray ionisation ion trap mass spectrometer. We found a longer peptide, Abeta43, to be more frequent than Abeta40. No variants longer than Abeta43 could be observed in any of the brains. Immunohistochemistry was performed and was found to be in line with our findings. Abeta1-43 polymerizes rapidly and we suggest that this variant may be of importance for AD.

    Journal of neurochemistry 2009;110;2;697-706

  • Alzheimer's disease genetic mutation evokes ultrastructural alterations: correlation to an intracellular Abeta deposition and the level of GSK-3beta-P(Y216) phosphorylated form.

    Pajak B, Songin M, Strosznajder JB and Gajkowska B

    Department of Cell Ultrastructure, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106 Warsaw, Poland. bepaj@wp.pl

    Herein we demonstrate that PC12 cells, which overexpress human wild-type amyloid-beta precursor protein (AbetaPPwt) or AbetaPP bearing double Swedish mutation (AbetaPPsw), reveal phenotype characteristic for Alzheimer's disease (AD). The examination of cell ultrastructure showed the presence of peptide aggregates within the cells, activation of endosomal-lysosomal system and extensive exocytosis. Furthermore, the autophagy induction was also characteristic hallmark of amyloid-beta-induced cytotoxicity. Morphological changes were positively correlated with the extent of phosphorylated glycogen synthase kinase-3beta (phospho-Tyr(216)-GSK-3beta, GSK-3beta-P(Y216)). The activity of GSK-3beta is believed to cause tau protein hyper-phosphorylation, increased amyloid-beta production and local plaque-associated microglial-mediated inflammatory responses. All of them are symptomatic for AD. In our studies, the highly significant Y216 phosphorylation and over-expression of total GSK-3beta were observed in AbetaPPsw-transfected PC12 cells. In addition, the immuocytochemical analysis showed co-localization of GSK-3beta-P(Y216) and amyloid-beta deposits. Thus, our data support a functional role of GSK-3beta in AbetaPP processing, further implicating this kinase in the amyloid-beta-dependent pathogenesis.

    Neurotoxicology 2009;30;4;581-8

  • Binding and uptake of A beta1-42 by primary human astrocytes in vitro.

    Nielsen HM, Veerhuis R, Holmqvist B and Janciauskiene S

    Department of Clinical Chemistry, Pathology, The Alzheimer Centre, VU University Medical Center Amsterdam, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands. h.nielsen@vumc.nl

    Clearance of the amyloid-beta peptide (A beta) as a remedy for Alzheimer's disease (AD) is a major target in on-going clinical trials. In vitro studies confirmed that A beta is taken up by rodent astrocytes, but knowledge on human astrocyte-mediated A beta clearance is sparse. Therefore, by means of flow cytometry and confocal laser scanning microscopy (CLSM), we evaluated the binding and internalization of A beta1-42 by primary human fetal astrocytes and adult astrocytes, isolated from nondemented subjects (n = 8) and AD subjects (n = 6). Furthermore, we analyzed whether alpha1-antichymotrypsin (ACT), which is found in amyloid plaques and can influence A beta fibrillogenesis, affects the A beta uptake by human astrocytes. Upon over night exposure of astrocytes to FAM-labeled A beta1-42 (10 microM) preparations, (80.7 +/- 17.7)% fetal and (52.9 +/- 20.9)% adult A beta-positive astrocytes (P = 0.018) were observed. No significant difference was found in A beta1-42 uptake between AD and non-AD astrocytes, and no influence of ApoE genotype on A beta1-42 uptake was observed in any group. There was no difference in the percentage of A beta-positive cells upon exposure to A beta1-42 (10 microM) combined with ACT (1,000:1, 100:1, and 10:1 molar ratio), versus A beta1-42 alone. CLSM revealed binding of A beta1-42 to the cellular surfaces and cellular internalization of smaller A beta1-42 fragments. Under these conditions, there was no increase in cellular release of the proinflammatory chemokine monocyte-chemoattractant protein 1, as compared with nontreated control astrocytes. Thus, primary human astrocytes derived from different sources can bind and internalize A beta1-42, and fetal astrocytes were more efficient in A beta1-42 uptake than adult astrocytes.

    Glia 2009;57;9;978-88

  • c-Abl modulates AICD dependent cellular responses: transcriptional induction and apoptosis.

    Vázquez MC, Vargas LM, Inestrosa NC and Alvarez AR

    Department of Cellular and Molecular Biology, Faculty of Biological Sciences, Pontifical Catholic University of Chile, Santiago, Chile.

    APP intracellular domain (AICD) has been proposed as a transcriptional inductor that moves to the nucleus with the adaptor protein Fe65 and regulates transcription. The two proteins, APP and Fe65, can be phosphorylated by c-Abl kinase. Neprilysin has been proposed as a target gene for AICD. We found that AICD expression is decreased by treatment with STI-571, a c-Abl inhibitor, suggesting a modulation of AICD transcription by c-Abl kinase. We observed interaction between c-Abl kinase, the AICD fragment and the Fe65 adaptor protein. In addition, STI-571 reduces apoptosis in APPSw, and the apoptotic response induced by Fe65 over-expression was inhibited by with the expression of a kinase dead (KD) c-Abl and enhanced by over-expression of WT-c-Abl. However, in the APPSw cells, the ability of the KD-c-Abl to protect against Fe65 was reduced. Finally, in APPSw clone, we detected higher trans-activation of the pro-apoptotic p73 isoform, TAp73 promoter. Our results show that c-Abl modulates AICD dependent cellular responses, transcriptional induction as well as the apoptotic response, which could participate in the onset and progression of the neurodegenerative pathology, observed in Alzheimer's disease (AD).

    Journal of cellular physiology 2009;220;1;136-43

  • Circulating immune complexes of Abeta and IgM in plasma of patients with Alzheimer's disease.

    Marcello A, Wirths O, Schneider-Axmann T, Degerman-Gunnarsson M, Lannfelt L and Bayer TA

    Department of Psychiatry, University Medicine Goettingen, Göttingen 37075, Germany.

    It has previously been shown that immune complexes (IC) of a given biomarker with class M immunoglobulins (IgM) provide better performances compared to the unbound biomarker in a number of cancer entities. In the present work, we investigated IC of IgM-Abeta as a potential biomarker for Alzheimer's disease (AD). Abeta-IgM concentration has been measured in 75 plasma samples from patients with AD, individuals with mild cognitive impairment (MCI), and healthy age- and sex-matched controls (HC). To characterize the fractions associated with Abeta, pooled plasma samples were subjected to gel-filtration analysis. Size-separated fractions were analyzed for the presence of Abeta using a sandwich ELISA assay. A strong reactivity was observed in the high molecular weight IgM (>500 kDa) and 150 kDa (IgG) fractions indicating that blood Abeta is strongly associated with antibodies. Using an ELISA assay detecting Abeta-IgM complexes, we observed that high levels of Abeta-IgMs were detectable in HC and MCI patients; however, there was no significant difference to the AD group.

    Journal of neural transmission (Vienna, Austria : 1996) 2009;116;7;913-20

  • Mild cholesterol depletion reduces amyloid-beta production by impairing APP trafficking to the cell surface.

    Guardia-Laguarta C, Coma M, Pera M, Clarimón J, Sereno L, Agulló JM, Molina-Porcel L, Gallardo E, Deng A, Berezovska O, Hyman BT, Blesa R, Gómez-Isla T and Lleó A

    Alzheimer Laboratory, Neurology Department, Hospital de la Santa Creu i Sant Pau, Universitat Autonoma de Barcelona, Barcelona, Spain.

    It has been suggested that cellular cholesterol levels can modulate the metabolism of the amyloid precursor protein (APP) but the underlying mechanism remains controversial. In the current study, we investigate in detail the relationship between cholesterol reduction, APP processing and gamma-secretase function in cell culture studies. We found that mild membrane cholesterol reduction led to a decrease in Abeta(40) and Abeta(42) in different cell types. We did not detect changes in APP intracellular domain or Notch intracellular domain generation. Western blot analyses showed a cholesterol-dependent decrease in the APP C-terminal fragments and cell surface APP. Finally, we applied a fluorescence resonance energy transfer (FRET)-based technique to study APP-Presenilin 1 (PS1) interactions and lipid rafts in intact cells. Our data indicate that cholesterol depletion reduces association of APP into lipid rafts and disrupts APP-PS1 interaction. Taken together, our results suggest that mild membrane cholesterol reduction impacts the cleavage of APP upstream of gamma-secretase and appears to be mediated by changes in APP trafficking and partitioning into lipid rafts.

    Funded by: NIA NIH HHS: AG026593, AG15379, P01 AG015379-110009, R01 AG026593-01A1, R01 AG026593-04

    Journal of neurochemistry 2009;110;1;220-30

  • Overexpression of Tfam protects mitochondria against beta-amyloid-induced oxidative damage in SH-SY5Y cells.

    Xu S, Zhong M, Zhang L, Wang Y, Zhou Z, Hao Y, Zhang W, Yang X, Wei A, Pei L and Yu Z

    Department of Occupational Health, Third Military Medical University, Chongqing, China.

    There is strong evidence that beta-amyloid (Abeta) causes oxidative stress and induces mitochondrial dysfunction in the pathogenesis of Alzheimer's disease. Mitochondrial transcription factor A (Tfam) has multiple roles in the maintenance of mtDNA. To study the protective roles of Tfam against amyloid neurotoxicity, we established SH-SY5Y cell lines stably overexpressing Tfam and exposed them to 10 microm Abeta1-42 for 24 h. We found that Tfam overexpression attenuated Abeta1-42-induced cell viability damage and apoptosis. In addition, Tfam overexpression significantly suppressed the increase in excess reactive oxygen species and reversed the reduction in cytochrome c oxidase activity and ATP production induced by Abeta1-42. Furthermore, overexpression of DeltaC-Tfam, which has no functional domain for stimulating mtDNA transcription but can still maintain the mtDNA nucleoid formation and mtDNA copy number, also exhibited protective effects against Abeta1-42 cytotoxicity in SH-SY5Y cells. Together, our data suggest that Tfam overexpression protects mitochondria against Abeta-induced oxidative damage in SH-SY5Y cells. These beneficial effects may be attributable to the roles of Tfam in maintaining mtDNA nucleoid formation and mtDNA copy number.

    The FEBS journal 2009;276;14;3800-9

  • Zinc and copper modulate Alzheimer Abeta levels in human cerebrospinal fluid.

    Strozyk D, Launer LJ, Adlard PA, Cherny RA, Tsatsanis A, Volitakis I, Blennow K, Petrovitch H, White LR and Bush AI

    Albert Einstein College of Medicine, Department of Neurology, Bronx, NY, USA.

    Abnormal interaction of beta-amyloid 42 (Abeta42) with copper, zinc and iron induce peptide aggregation and oxidation in Alzheimer's disease (AD). However, in health, Abeta degradation is mediated by extracellular metalloproteinases, neprilysin, insulin degrading enzyme (IDE) and matrix metalloproteinases. We investigated the relationship between levels of Abeta and biological metals in CSF. We assayed CSF copper, zinc, other metals and Abeta42 in ventricular autopsy samples of Japanese American men (N=131) from the population-based Honolulu Asia Aging Study. There was a significant inverse correlation of CSF Abeta42 with copper, zinc, iron, manganese and chromium. The association was particularly strong in the subgroup with high levels of both zinc and copper. Selenium and aluminum levels were not associated to CSF Abeta42. In vitro, the degradation of synthetic Abeta substrate added to CSF was markedly accelerated by low levels (2microM) of exogenous zinc and copper. While excessive interaction with copper and zinc may induce neocortical Abeta precipitation in AD, soluble Abeta degradation is normally promoted by physiological copper and zinc concentrations.

    Funded by: NIA NIH HHS: 1 U01 AG19349-01, 1R01 AG12686, 5 R01 AG017155-04, R01 AG012686-10

    Neurobiology of aging 2009;30;7;1069-77

  • Microscopic factors that control beta-sheet registry in amyloid fibrils formed by fragment 11-25 of amyloid beta peptide: insights from computer simulations.

    Negureanu L and Baumketner A

    Department of Physics and Optical Science, University of North Carolina Charlotte, 28223, USA.

    Short fragments of amyloidogenic proteins are widely used as model systems in studies of amyloid formation. Fragment 11-25 of the amyloid beta protein involved in Alzheimer's disease (Abeta11-25) was recently shown to form amyloid fibrils composed of anti-parallel beta-sheets. Interestingly, fibrils grown under neutral and acidic conditions were seen to possess different registries of their inter-beta-strand hydrogen bonds. In an effort to explain the microscopic origin of this pH dependence, we studied Abeta11-25 fibrils using methods of theoretical modeling. Several structural models were built for fibrils at low and neutral pH levels and these were examined in short molecular dynamics simulations in explicit water. The models that displayed the lowest free energy, as estimated using an implicit solvent model, were selected as representative of the true fibrillar structure. It was shown that the registry of these models agrees well with the experimental results. At neutral pH, the main contribution to the free energy difference between the two registries comes from the electrostatic interactions. The charge group of the carboxy terminus makes a large contribution to these interactions and thus appears to have a critical role in determining the registry.

    Funded by: NIGMS NIH HHS: R01 GM083600-02, R01GM083600-02

    Journal of molecular biology 2009;389;5;921-37

  • Interaction of reelin with amyloid precursor protein promotes neurite outgrowth.

    Hoe HS, Lee KJ, Carney RS, Lee J, Markova A, Lee JY, Howell BW, Hyman BT, Pak DT, Bu G and Rebeck GW

    Department of Neuroscience, Georgetown University Medical Center, Washington, DC 20057-1464, USA.

    The processing of amyloid precursor protein (APP) to Abeta is an important event in the pathogenesis of Alzheimer's disease, but the physiological function of APP is not well understood. Our previous work has shown that APP processing and Abeta production are regulated by the extracellular matrix protein Reelin. In the present study, we examined whether Reelin interacts with APP, and the functional consequences of that interaction in vitro. Using coimmunoprecipitation, we found that Reelin interacted with APP through the central domain of Reelin (repeats 3-6) and the E1 extracellular domain of APP. Reelin increased cell surface levels of APP and decreased endocytosis of APP in hippocampal neurons in vitro. In vivo, Reelin levels were increased in brains of APP knock-out mice and decreased in APP-overexpressing mice. RNA interference knockdown of APP decreased neurite outgrowth in vitro and prevented Reelin from increasing neurite outgrowth. Knock-out of APP or Reelin decreased dendritic arborization in cortical neurons in vivo, and APP overexpression increased dendritic arborization. APP and Reelin have previously been shown to promote neurite outgrowth through interactions with integrins. We confirmed that APP interacted with alpha3beta1 integrin, and alpha3beta1 integrin altered APP trafficking and processing. Addition of an alpha3beta1 integrin antibody prevented APP and Reelin-induced neurite outgrowth. These findings demonstrate that Reelin interacts with APP, potentially having important effects on neurite development.

    Funded by: NIA NIH HHS: AG014473, AG032330, P01 AG030128, R01 AG014473, R01 AG014473-13, R01 AG027924, R01 AG035355, R03 AG030060, R03 AG030060-02, R03 AG032330, R29 AG014473, R37 AG012406; NINDS NIH HHS: R01 NS048085, R01 NS048085-04

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;23;7459-73

  • BRI3 inhibits amyloid precursor protein processing in a mechanistically distinct manner from its homologue dementia gene BRI2.

    Matsuda S, Matsuda Y and D'Adamio L

    Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, New York 1046, USA.

    Alzheimer disease (AD) is characterized by senile plaques, which are mainly composed of beta amyloid (Abeta) peptides. Abeta is cleaved off from amyloid precursor protein (APP) with consecutive proteolytic processing: beta-secretase, followed by gamma-secretase. Here, we show that BRI3, a member of the BRI gene family that includes the familial British and Danish dementia gene BRI2, interacts with APP and serves as an endogenous negative regulator of Abeta production. BRI3 colocalizes with APP along neuritis in differentiated N2a cells; endogenous BRI3-APP complexes are readily detectable in mouse brain extract; reducing endogenous BRI3 levels by RNA interference results in increased Abeta secretion. BRI3 resembles BRI2, because BRI3 overexpression reduces both alpha- and beta-APP cleavage. We propose that BRI3 inhibits the various processing of APP by blocking the access of alpha- and beta-secretases to APP. However, unlike BRI2, the binding of BRI3 to the beta-secretase cleaved APP C-terminal fragment is negligible and BRI3 does not cause the massive accumulation of this APP fragment, suggesting that, unlike BRI2, BRI3 is a poor gamma-cleavage inhibitor. Competitive inhibition of APP processing by BRI3 may provide a new approach to AD therapy and prevention.

    Funded by: NIA NIH HHS: R01 AG021588, R01 AG022024, R01 AG21588, R01 AG22024, R21 AG027139

    The Journal of biological chemistry 2009;284;23;15815-25

  • Intracellular Abeta and C99 aggregates induce mitochondria-dependent cell death in human neuroglioma H4 cells through recruitment of the 20S proteasome subunits.

    Park HJ, Kim SS, Kang S and Rhim H

    School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea.

    Recent studies have reported that neuronal apoptosis is induced not only by extracellular Abeta but also by intracellular Abeta; however, the mechanism by which intracellular Abeta contributes to the regulation of cell death associated with the pathogenesis of AD remains to be elucidated. Using immunological assays and a short-lived enhanced green fluorescent protein (d2EGFP) system, we showed that intracellular Abeta and C99 form perinuclear aggregates in the cytosol, and the resulting aggregates attenuate the activity of the 26S proteasome. In addition, the immunofluorescence assays (IFA) revealed that the 20S proteasome alpha-subunits are recruited into perinuclear aggregates in both human embryonic kidney (HEK293) and human neuroglioma H4 (H4) cells. Interestingly, we observed an increase in the levels of Bax, cleavage of PARP-1, and mitochondrial release of proapoptotic proteins, such as cytochrome c and HtrA2, in H4 cells with intracellular Abeta or C99 aggregates, but not in HEK293 cells with those aggregates. The results of the present study indicate that intracellular Abeta and C99 aggregates induce mitochondria-dependent apoptotic cell death via elevation of Bax levels as a result of proteasome inhibition in a cell type-specific manner.

    Brain research 2009;1273;1-8

  • APP/PS1KI bigenic mice develop early synaptic deficits and hippocampus atrophy.

    Breyhan H, Wirths O, Duan K, Marcello A, Rettig J and Bayer TA

    Division of Molecular Psychiatry, Department of Psychiatry, Alzheimer Ph.D. Graduate School, University of Goettingen, Goettingen, Germany.

    Abeta accumulation has an important function in the etiology of Alzheimer's disease (AD) with its typical clinical symptoms, like memory impairment and changes in personality. However, the mode of this toxic activity is still a matter of scientific debate. We used the APP/PS1KI mouse model for AD, because it is the only model so far which develops 50% hippocampal CA1 neuron loss at the age of 1 year. Previously, we have shown that this model develops severe learning deficits occurring much earlier at the age of 6 months. This observation prompted us to study the anatomical and cellular basis at this time point in more detail. In the current report, we observed that at 6 months of age there is already a 33% CA1 neuron loss and an 18% atrophy of the hippocampus, together with a drastic reduction of long-term potentiation and disrupted paired pulse facilitation. Interestingly, at 4 months of age, there was no long-term potentiation deficit in CA1. This was accompanied by reduced levels of pre- and post-synaptic markers. We also observed that intraneuronal and total amount of different Abeta peptides including N-modified, fibrillar and oligomeric Abeta species increased and coincided well with CA1 neuron loss. Overall, these data provide the basis for the observed robust working memory deficits in this mouse model for AD at 6 months of age.

    Acta neuropathologica 2009;117;6;677-85

  • Deprivation-induced dendritic shrinkage might be oppositely affected by the expression of wild-type and mutated human amyloid precursor protein.

    Alpár A, Naumann N, Ueberham U, Arendt T and Gärtner U

    Department of Anatomy, Histology and Embryology, Semmelweis University Medical School, Budapest, Hungary. dralpar@gmx.net

    The physiological role of the amyloid precursor protein (APP) and its proteolytic fragments in the brain is associated with neuronal survival, neurite outgrowth, synaptic formation, and neuronal plasticity. However, malregulation of APP processing leads to disordered balance of fragments, which may results in opposite, degenerative neuronal effects. In the present study, we analyzed in vivo effects of the expression of wild-type or mutated human APP on afferent deprivation-induced changes of dendritic morphology. After vibrissectomy, expression of wild-type human APP prevented diameter shrinkage of dendritic segments as well as dendritic rarefaction of apical arbors. In contrast, mutant human APP expression exacerbated degenerative changes of deprived barrel neurons. Degradation of apical arbors was especially pronounced. Results demonstrate for the first time opposite effects of the expression of wild-type and mutated human APP on deprivation-induced dendritic restructuring in vivo.

    Journal of neuroscience research 2009;87;8;1813-22

  • Mutations in amyloid precursor protein affect its interactions with presenilin/gamma-secretase.

    Herl L, Thomas AV, Lill CM, Banks M, Deng A, Jones PB, Spoelgen R, Hyman BT and Berezovska O

    Alzheimer Research Unit, MassGeneral Institute for Neurodegenerative, Diseases, Massachusetts General Hospital, 114 16th Street, Charlestown, MA 02129, USA.

    Alzheimer's disease is characterized by accumulation of toxic beta-amyloid (Abeta) in the brain and neuronal death. Several mutations in presenilin (PS1) and beta-amyloid precursor protein (APP) associate with an increased Abeta(42/40) ratio. Abeta(42), a highly fibrillogenic species, is believed to drive Abeta aggregation. Factors shifting gamma-secretase cleavage of APP to produce Abeta(42) are unclear. We investigate the molecular mechanism underlying altered Abeta(42/40) ratios associated with APP mutations at codon 716 and 717. Using FRET-based fluorescence lifetime imaging to monitor APP-PS1 interactions, we show that I716F and V717I APP mutations increase the proportion of interacting molecules earlier in the secretory pathway, resulting in an increase in Abeta generation. A PS1 conformation assay reveals that, in the presence of mutant APP, PS1 adopts a conformation reminiscent of FAD-associated PS1 mutations, thus influencing APP binding to PS1/gamma-secretase. Mutant APP affects both intracellular location and efficiency of APP-PS1 interactions, thereby changing the Abeta(42/40) ratio.

    Funded by: NIA NIH HHS: AG 15379, AG026593, P01 AG015379, P01 AG015379-110009, R01 AG026593, R01 AG026593-01A1, R01 AG026593-02, R01 AG026593-03

    Molecular and cellular neurosciences 2009;41;2;166-74

  • Pharmacology of the intracellular pathways activated by amyloid beta protein.

    Balleza-Tapia H and Peña F

    Departamento de Farmacobiología, Cinvestav-Sede Sur, Col. Granjas Coapa, 14330, México, México.

    Alzheimer's disease (AD) is a late-life cognitive disorder associated, among other things, to the presence of extracellular aggregates of fibrillar amyloid beta protein (Abeta). However, there is growing evidence that early stages of AD may be due to neuronal network dysfunction produced by the actions of soluble forms of Abeta. Therefore, the development of new therapeutic strategies to treat AD, at least during its first stages, may be focused on preventing or reversing, the deleterious effects that soluble Abeta exerts on neuronal circuit function. In order to do so, it is necessary to elucidate the pathophysiological processes involved in Abeta-induced neuronal network dysfunction and the molecular processes underlying such dysfunction. Over the last decades, there has been extensive research about the molecular mechanisms involved in the effects of Abeta as well as possible neuroprotective strategies against such effects. Here we are going to review some of the intracellular pathways triggered by Abeta, which involve membrane receptors such as nicotinic-R, NMDA-R, integrins, TNF-R1, RAGE, FPRL and p75NTR and their intracellular mediators such as GSK3, PKC, PI3K, Akt, FAK, MAPK family, Src family and cdk5. Several of these pathways may constitute therapeutic targets for the treatment of the Abeta-induced neuronal network dysfunction which is, at least in part, the basis for cognitive dysfunction in AD.

    Mini reviews in medicinal chemistry 2009;9;6;724-40

  • Abeta40, either soluble or aggregated, is a remarkably potent antioxidant in cell-free oxidative systems.

    Baruch-Suchodolsky R and Fischer B

    Department of Chemistry, Gonda-Goldschmied Medical Research Center, Bar-Ilan University, Ramat-Gan 52900, Israel.

    The brains of individuals diagnosed with Alzheimer's disease (AD) are characterized by amyloid plaques, of which the major component is Abeta peptide. Excessive Cu and Fe ions binding to Abeta were suggested to have a deleterious effect on promoting both the aggregation of Abeta and the generation of reactive oxygen species (ROS). Other studies suggested that Abeta plays a protective role by acting as an antioxidant at nanomolar concentrations. The apparent confusion regarding the antioxidant and pro-oxidant properties of Abeta(40) encouraged us to explore the modulatory role of Abeta(40) at the molecular level under oxidative stress conditions. Here, we focused on Abeta(40) in the simplest oxidative system, namely, Cu(I)/Cu(II)/Fe(II)-H(2)O(2). Using ESR, we monitored the production of OH radicals in the above-mentioned systems in the presence of Abeta(40). We found that Abeta(40), either in its soluble or in its aggregated form, functioned as a remarkably potent antioxidant in Cu(I)/Fe(II)-catalyzed radical-producing systems and slightly less potently in the presence of Cu(II) with IC(50) values of 13-62 muM. Abeta(40) proved to be 3.8-6.5 and 15-42 times more potent than the soluble Abeta(28) and the potent antioxidant Trolox, respectively, in the Cu(I)/Fe(II)-H(2)O(2) systems. Time-dependent enhancement of ROS production by Abeta(40) occurs only at low concentrations of aggregated Abeta(40) and in the presence of Cu(II). On the basis of the extremely low IC(50) values of Abeta(40) and the extensive oxidative damage caused to Abeta(40) in Cu(I)/Fe(II)-H(2)O(2) systems, we propose that radical scavenging is the major mechanism of antioxidant activity of Abeta(40) in addition to metal ion chelation. In summary, Abeta(40), either soluble or aggregated, at either nanomolar or micromolar concentrations is a highly potent antioxidant in cell-free oxidative systems, acting mainly as a radical scavenger. Therefore, we propose that it is not the Abeta(40)-Cu(I)/Fe(II) complex per se that is responsible for the oxidative damage in AD.

    Biochemistry 2009;48;20;4354-70

  • Copper(II) binding to amyloid-beta fibrils of Alzheimer's disease reveals a picomolar affinity: stoichiometry and coordination geometry are independent of Abeta oligomeric form.

    Sarell CJ, Syme CD, Rigby SE and Viles JH

    School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK.

    Cu(2+) ions are found concentrated within senile plaques of Alzheimer's disease patients directly bound to amyloid-beta peptide (Abeta) and are linked to the neurotoxicity and self-association of Abeta. The affinity of Cu(2+) for monomeric Abeta is highly disputed, and there have been no reports of affinity of Cu(2+) for fibrillar Abeta. We therefore measured the affinity of Cu(2+) for both monomeric and fibrillar Abeta(1-42) using two independent methods: fluorescence quenching and circular dichroism. The binding curves were almost identical for both fibrillar and monomeric forms. Competition studies with free glycine, l-histidine, and nitrilotriacetic acid (NTA) indicate an apparent (conditional) dissociation constant of 10(-11) M, at pH 7.4. Previous studies of Cu-Abeta have typically found the affinity 2 or more orders of magnitude weaker, largely because the affinity of competing ligands or buffers has been underestimated. Abeta fibers are able to bind a full stoichiometric complement of Cu(2+) ions with little change in their secondary structure and have coordination geometry identical to that of monomeric Abeta. Electron paramagnetic resonance studies (EPR) with Abeta His/Ala analogues suggest a dynamic view of the tetragonal Cu(2+) complex, with axial as well as equatorial coordination of imidazole nitrogens creating an ensemble of coordination geometries in exchange between each other. Furthermore, the N-terminal amino group is essential for the formation of high-pH complex II. The Abeta(1-28) fragment binds an additional Cu(2+) ion compared to full-length Abeta, with appreciable affinity. This second binding site is revealed in Abeta(1-42) upon addition of methanol, indicating hydrophobic interactions block the formation of this weaker carboxylate-rich complex. A Cu(2+) affinity for Abeta of 10(11) M(-1) supports a modified amyloid cascade hypothesis in which Cu(2+) is central to Abeta neurotoxicity.

    Funded by: Biotechnology and Biological Sciences Research Council: BB/D005027/1

    Biochemistry 2009;48;20;4388-402

  • Overexpression of amyloid precursor protein increases copper content in HEK293 cells.

    Suazo M, Hodar C, Morgan C, Cerpa W, Cambiazo V, Inestrosa NC and Gonzalez M

    INTA, Laboratorio de Bioinformatica y Expresion Genica, Universidad de Chile, Macul, Santiago, Chile.

    Amyloid precursor protein (APP) is a transmembrane glycoprotein widely expressed in mammalian tissues and plays a central role in Alzheimer's disease. However, its physiological function remains elusive. Cu(2+) binding and reduction activities have been described in the extracellular APP135-156 region, which might be relevant for cellular copper uptake and homeostasis. Here, we assessed Cu(2+) reduction and (64)Cu uptake in two human HEK293 cell lines overexpressing APP. Our results indicate that Cu(2+) reduction increased and cells accumulated larger levels of copper, maintaining cell viability at supra-physiological levels of Cu(2+) ions. Moreover, wild-type cells exposed to both Cu(2+) ions and APP135-155 synthetic peptides increased copper reduction and uptake. Complementation of function studies in human APP751 transformed Fre1 defective Saccharomyces cerevisiae cells rescued low Cu(2+) reductase activity and increased (64)Cu uptake. We conclude that Cu(2+) reduction activity of APP facilitates copper uptake and may represent an early step in cellular copper homeostasis.

    Biochemical and biophysical research communications 2009;382;4;740-4

  • Longitudinal regional brain volume changes quantified in normal aging and Alzheimer's APP x PS1 mice using MRI.

    Maheswaran S, Barjat H, Rueckert D, Bate ST, Howlett DR, Tilling L, Smart SC, Pohlmann A, Richardson JC, Hartkens T, Hill DL, Upton N, Hajnal JV and James MF

    Department of Computing, Imperial College, London, UK.

    In humans, mutations of amyloid precursor protein (APP) and presenilins (PS) 1 and 2 are associated with amyloid deposition, brain structural change and cognitive decline, like in Alzheimer's disease (AD). Mice expressing these proteins have illuminated neurodegenerative disease processes but, unlike in humans, quantitative imaging has been little used to systematically determine their effects, or those of normal aging, on brain structure in vivo. Accordingly, we investigated wildtype (WT) and TASTPM mice (expressing human APP(695(K595N, M596L)) x PS1(M146V)) longitudinally using MRI. Automated global and local image registration, allied to a standard digital atlas, provided pairwise segmentation of 13 brain regions. We found the mature mouse brain, unlike in humans, enlarges significantly from 6-14 months old (WT 3.8+/-1.7%, mean+/-SD, P<0.0001). Significant changes were also seen in other WT brain regions, providing an anatomical benchmark for comparing other mouse strains and models of brain disorder. In TASTPM, progressive amyloidosis and astrogliosis, detected immunohistochemically, reflected even larger whole brain changes (5.1+/-1.4%, P<0.0001, transgenexage interaction P=0.0311). Normalising regional volumes to whole brain measurements revealed significant, prolonged, WT-TASTPM volume differences, suggesting transgene effects establish at <6 months old of age in most regions. As in humans, gray matter-rich regions decline with age (e.g. thalamus, cerebral cortex and caudoputamen); ventricles and white matter (corpus callosum, corticospinal tract, fornix system) increase; in TASTPMs such trends often varied significantly from WT (especially hippocampus). The pervasive, age-related structural changes between WT and AD transgenic mice (and mouse and human) suggest subtle but fundamental species differences and AD transgene effects.

    Funded by: Medical Research Council: MC_U120061309

    Brain research 2009;1270;19-32

  • Experimental characterization of disordered and ordered aggregates populated during the process of amyloid fibril formation.

    Carulla N, Zhou M, Arimon M, Gairí M, Giralt E, Robinson CV and Dobson CM

    Institució Catalana de Recerca i Estudis Avançats Researcher at Institut de Recerca Biomèdica, Baldiri Reixac 10-12, 08028 Barcelona, Spain. natalia.carulla@irbbarcelona.org

    Recent experimental evidence points to intermediates populated during the process of amyloid fibril formation as the toxic moieties primarily responsible for the development of increasingly common disorders such as Alzheimer's disease and type II diabetes. We describe here the application of a pulse-labeling hydrogen-deuterium (HD) exchange strategy monitored by mass spectrometry (MS) and NMR spectroscopy (NMR) to characterize the aggregation process of an SH3 domain under 2 different conditions, both of which ultimately lead to well-defined amyloid fibrils. Under one condition, the intermediates appear to be largely amorphous in nature, whereas under the other condition protofibrillar species are clearly evident. Under the conditions favoring amorphous-like intermediates, only species having no protection against HD exchange can be detected in addition to the mature fibrils that show a high degree of protection. By contrast, under the conditions favoring protofibrillar-like intermediates, MS reveals that multiple species are present with different degrees of HD exchange protection, indicating that aggregation occurs initially through relatively disordered species that subsequently evolve to form ordered aggregates that eventually lead to amyloid fibrils. Further analysis using NMR provides residue-specific information on the structural reorganizations that take place during aggregation, as well as on the time scales by which they occur.

    Funded by: Wellcome Trust

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;19;7828-33

  • Stimulus pattern dependence of the Alzheimer's disease amyloid-beta 42 peptide's inhibition of long term potentiation in mouse hippocampal slices.

    Smith JP, Lal V, Bowser D, Cappai R, Masters CL and Ciccotosto GD

    Colorado State University-Pueblo, Pueblo, CO 81001, USA. jeff.smith@colostate-pueblo.edu

    Increasing evidence has pointed to inhibition of Long Term Potentiation (LTP) by soluble A beta 42 oligomers as central in the etiology of the learning and memory deficits that are hallmarks of Alzheimer Disease. These effects are thought to occur by an interaction between A beta 42 and certain cellular effectors that induce LTP, however, the precise identity of the A beta 42-interactive signaling molecules is unknown. Identification of such effectors is made more difficult because LTP induced by different stimulation protocols can be expressed through heterogeneous signaling pathways. The aim of this study was to compare differences in the A beta 42-dependent levels of inhibition of LTPs that were induced using high frequency stimulation (HFS), versus theta burst stimulation (TBS). Our results show that untreated control brain slices tetanized with either HFS or TBS gave similar levels of LTP and post tetanic stimulation (PTP), suggesting that the response induced by either protocol was comparable. However, A beta 42 peptide significantly blocked LTP and PTP induced by HFS, but not when TBS was used. NMDA receptor antagonists, D-AP5 and ifenprodil, both blocked LTPs that were induced by HFS or TBS. We propose that unknown signaling effectors, other than the NMDA receptor, which are differentially involved in the induction of LTP by TBS, as compared to HFS, may be responsible for this resistance of TBS-induced LTP to A beta 42 dependent inhibition.

    Brain research 2009;1269;176-84

  • Amyloid beta interaction with receptor for advanced glycation end products up-regulates brain endothelial CCR5 expression and promotes T cells crossing the blood-brain barrier.

    Li M, Shang DS, Zhao WD, Tian L, Li B, Fang WG, Zhu L, Man SM and Chen YH

    Department of Developmental Biology, Key Laboratory of Cell Biology, Ministry of Public Health of China, China Medical University, Shenyang, People's Republic of China.

    How circulating T cells infiltrate into the brain in Alzheimer disease (AD) remains unclear. We previously reported that amyloid beta (Abeta)-dependent CCR5 expression in brain endothelial cells is involved in T cell transendothelial migration. In this study, we explored the signaling pathway of CCR5 up-regulation by Abeta. We showed that inhibitors of JNK, ERK, and PI3K significantly decreased Abeta-induced CCR5 expression in human brain microvascular endothelial cells (HBMECs). Chromatin immunoprecipitation assay revealed that Abeta-activated JNK, ERK, and PI3K promoted brain endothelial CCR5 expression via transcription factor Egr-1. Furthermore, neutralization Ab of receptor for advanced glycation end products (RAGE; an Abeta receptor) effectively blocked Abeta-induced JNK, ERK, and PI3K activation, contributing to CCR5 expression in HBMECs. Abeta fails to induce CCR5 expression when truncated RAGE was overexpressed in HBMECs. Transendothelial migration assay showed that the migration of MIP-1alpha (a CCR5 ligand)-expressing AD patients' T cells through in vitro blood-brain barrier model was effectively blocked by anti-RAGE Ab, overexpression of truncated RAGE, and dominant-negative PI3K, JNK/ERK, or Egr-1 RNA interference in HBMECs, respectively. Importantly, blockage of intracerebral RAGE abolished the up-regulation of CCR5 on brain endothelial cells and the increased T cell infiltration in the brain induced by Abeta injection in rat hippocampus. Our results suggest that intracerebral Abeta interaction with RAGE at BBB up-regulates endothelial CCR5 expression and causes circulating T cell infiltration in the brain in AD. This study may provide a new insight into the understanding of inflammation in the progress of AD.

    Journal of immunology (Baltimore, Md. : 1950) 2009;182;9;5778-88

  • Novel role of RanBP9 in BACE1 processing of amyloid precursor protein and amyloid beta peptide generation.

    Lakshmana MK, Yoon IS, Chen E, Bianchi E, Koo EH and Kang DE

    Department of Neurosciences, University of California, San Diego, La Jolla, California 92093, USA.

    Accumulation of the amyloid beta (Abeta) peptide derived from the proteolytic processing of amyloid precursor protein (APP) is the defining pathological hallmark of Alzheimer disease. We previously demonstrated that the C-terminal 37 amino acids of lipoprotein receptor-related protein (LRP) robustly promoted Abeta generation independent of FE65 and specifically interacted with Ran-binding protein 9 (RanBP9). In this study we found that RanBP9 strongly increased BACE1 cleavage of APP and Abeta generation. This pro-amyloidogenic activity of RanBP9 did not depend on the KPI domain or the Swedish APP mutation. In cells expressing wild type APP, RanBP9 reduced cell surface APP and accelerated APP internalization, consistent with enhanced beta-secretase processing in the endocytic pathway. The N-terminal half of RanBP9 containing SPRY-LisH domains not only interacted with LRP but also with APP and BACE1. Overexpression of RanBP9 resulted in the enhancement of APP interactions with LRP and BACE1 and increased lipid raft association of APP. Importantly, knockdown of endogenous RanBP9 significantly reduced Abeta generation in Chinese hamster ovary cells and in primary neurons, demonstrating its physiological role in BACE1 cleavage of APP. These findings not only implicate RanBP9 as a novel and potent regulator of APP processing but also as a potential therapeutic target for Alzheimer disease.

    Funded by: NIA NIH HHS: AG 005131-24S1

    The Journal of biological chemistry 2009;284;18;11863-72

  • Amyloid-beta42 is preferentially accumulated in muscle fibers of patients with sporadic inclusion-body myositis.

    Vattemi G, Nogalska A, King Engel W, D'Agostino C, Checler F and Askanas V

    USC Neuromuscular Center, Department of Neurology, University of Southern California Keck School of Medicine, Good Samaritan Hospital, Los Angeles, CA, 90017, USA.

    Sporadic inclusion-body myositis (s-IBM) is the only muscle disease in which accumulation of amyloid-beta (Abeta) in abnormal muscle fibers appears to play a key pathogenic role. Increased amyloid-beta precursor protein (AbetaPP) and Abeta accumulation have been reported to be upstream steps in the development of the s-IBM pathologic phenotype, based on cellular and animal models. Abeta is released from AbetaPP as a 40 or 42 aminoacid peptide. Abeta42 is considered more cytotoxic than Abeta40, and it has a higher propensity to aggregate and form amyloid fibrils. Using highly specific antibodies, we evaluated in s-IBM muscle biopsies intra-muscle fiber accumulation of Abeta40 and Abeta42-immunoreactive aggregates by light- and electron-microscopic immunocytochemistry, and quantified their amounts by ELISA. In s-IBM, 80-90% of the vacuolated muscle fibers and 5-20% of the non-vacuolated muscle fibers contained plaque-like Abeta42-immunoreactive inclusions, while only 69% of those fibers also contained Abeta40 deposits. By immuno-electronmicroscopy, Abeta42 was associated with 6-10 nm amyloid-like fibrils, small electron-dense floccular clumps and larger masses of amorphous material. Abeta40 was present only on small patches of floccular clumps and amorphous material; it was not associated with 6-10 nm amyloid fibrils. By ELISA, in s-IBM muscle biopsies Abeta42 was present in values 8.53-44.7 pg/ml, while Abeta40 was not detectable; normal age-matched control biopsies did not have any detectable Abeta42 or Abeta40. Thus, in s-IBM muscle fibers, Abeta42 is accumulated more than Abeta40. We suggest that Abeta42 oligomers and their cytotoxicity may play an important role in the s-IBM pathogenesis.

    Acta neuropathologica 2009;117;5;569-74

  • MCP-1 involvement in glial differentiation of neuroprogenitor cells through APP signaling.

    Vrotsos EG, Kolattukudy PE and Sugaya K

    Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32816-2364, USA.

    Previously it has been reported that neural stem cells undergoing apoptotic stress have increased levels of amyloid precursor protein (APP) and increased APP expression results in glial differentiation. APP activity was also shown to be required for staurosporine-induced glial differentiation of neuroprogenitor cells. Monocyte chemoattractant protein-1 (MCP-1) is a chemokine that is expressed early during inflammation. The binding of MCP-1 to its chemokine receptor induces expression of novel transcription factor MCP-1-induced protein (MCPIP). MCPIP expression subsequently leads to cell death. Previous studies have shown that pro-apoptotic factors have the ability to induce neural differentiation. Therefore, we investigated if MCPIP expression leads to differentiation of NT2 neuroprogenitor cells. Results showed that MCPIP expression increased glial fibrillary acid protein (GFAP) expression and also caused distinct morphological changes, both indicative of glial differentiation. Similar results were observed with MCP-1 treatment. Interestingly, APP expression decreased in response to MCPIP. Instead, we found APP activity regulates expression of both MCP-1 and MCPIP. Furthermore, inhibition of either p38 MAPK or JAK signaling pathways significantly reduced APP's effect on MCP-1 and MCPIP. These data demonstrates the role APP has in glial differentiation of NT2 cells through MCP-1/MCPIP signaling. It is possible that increased APP expression after CNS injury could play a role in MCP-1 production, possibly promoting astrocyte activation at injured site.

    Funded by: NIA NIH HHS: AG 23472, R01 AG023472, R01 AG023472-01

    Brain research bulletin 2009;79;2;97-103

  • Fibrillar amyloid-beta burden in cognitively normal people at 3 levels of genetic risk for Alzheimer's disease.

    Reiman EM, Chen K, Liu X, Bandy D, Yu M, Lee W, Ayutyanont N, Keppler J, Reeder SA, Langbaum JB, Alexander GE, Klunk WE, Mathis CA, Price JC, Aizenstein HJ, DeKosky ST and Caselli RJ

    Banner Alzheimer's Institute and the Positron Emission Tomography Center, Good Samaritan Regional Medical Center, Phoenix, AZ 85006, USA. eric.reiman@bannerhealth.com

    Fibrillar amyloid-beta (Abeta) is found in the brains of many cognitively normal older people. Whether or not this reflects a predisposition to Alzheimer's disease (AD) is unknown. We used Pittsburgh Compound B (PiB) PET to characterize the relationship between fibrillar Abeta burden and this predisposition in cognitively normal older people at 3 mean levels of genetic risk for AD. Dynamic PiB PET scans, the Logan method, statistical parametric mapping, and automatically labeled regions of interest (ROIs) were used to characterize and compare cerebral-to-cerebellar PIB distribution volume ratios, reflecting fibrillar Abeta burden, in 28 cognitively normal persons (mean age, 64 years) with a reported family history of AD and 2 copies, 1 copy, and no copies of the apolipoprotein E (APOE) epsilon4 allele. The 8 epsilon4 homozygotes, 8 heterozygotes, and 12 noncarriers did not differ significantly in terms of age, sex, or cognitive scores. Fibrillar Abeta was significantly associated with APOE epsilon4 carrier status and epsilon4 gene dose in AD-affected mean cortical, frontal, temporal, posterior cingulate-precuneus, parietal, and basal ganglia ROIs, and was highest in an additional homozygote who had recently developed mild cognitive impairment. These findings suggest that fibrillar Abeta burden in cognitively normal older people is associated with APOE epsilon4 gene dose, the major genetic risk factor for AD. Additional studies are needed to track fibrillar Abeta accumulation in persons with different kinds and levels of AD risk; to determine the extent to which fibrillar Abeta, alone or in combination with other biomarkers and risk factors, predicts rates of cognitive decline and conversion to clinical AD; and to establish the role of fibrillar Abeta imaging in primary prevention trials.

    Funded by: NIA NIH HHS: P01 AG025204, P01 AG025204-04S1, P01 AG025204-05, P01 AG025204-06, P01 AG025204-07, P01 AG025204-08, P30 AG019610, P30 AG019610-01, P30 AG019610-02, P30 AG019610-03, P30 AG019610-04, P30 AG019610-04S1, P30 AG019610-05, P30 AG019610-05S1, P30 AG019610-06, P30 AG019610-07, P30 AG019610-07S1, P30 AG019610-08, P30 AG019610-08S1, P30 AG019610-08S2, P30 AG019610-09, P30 AG19610, P50 AG005133, R01 AG018402, R01 AG025526, R01 AG031581, R01 AG031581-10, R01 AG031581-11, R37 AG025516, R37 AG025516-01, R37 AG025516-02, R37 AG025516-03, R37 AG025516-04, R37 AG025516-05, R37 AG025516-05S1, R37 AG025516-06, R37 AG025516-07, R37 AG025516-08, RF1 AG025516; NIMH NIH HHS: R01 MH057899, R01 MH057899-02, R01 MH057899-03, R01 MH057899-04, R01 MH057899-05, R01 MH057899-06, R01 MH057899-07, R01 MH057899-08, R01 MH057899-09, R01 MH070729, R01 MH70729

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;16;6820-5

  • Expression of human amyloid precursor protein in rat cortical neurons inhibits calcium oscillations.

    Santos SF, Pierrot N, Morel N, Gailly P, Sindic C and Octave JN

    Experimental Pharmacology Unit, Institute of Neuroscience, Université catholique de Louvain, B-1200 Brussels, Belgium.

    Synchronous calcium oscillations are observed in primary cultures of rat cortical neurons when mature networks are formed. This spontaneous neuronal activity needs an accurate control of calcium homeostasis. Alteration of intraneuronal calcium concentration is described in many neurodegenerative disorders, including Alzheimer disease (AD). Although processing of amyloid precursor protein (APP) that generates Abeta peptide has critical implications for AD pathogenesis, the neuronal function of APP remains unclear. Here, we report that expression of human APP (hAPP) in rat cortical neurons increases L-type calcium currents, which stimulate SK channels, calcium-dependent K(+) channels responsible for medium afterhyperpolarization (mAHP). In a neuronal network, increased mAHP in some neurons expressing hAPP leads to inhibition of calcium oscillations in all the cells of the network. This inhibition is independent of production and secretion of Abeta and other APP metabolites. In a neuronal network, reduction of endogenous APP expression using shRNA increases the frequency and reduces the amplitude of calcium oscillations. Altogether, these data support a key role for APP in the control of neuronal excitability.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;15;4708-18

  • S-nitrosylation of Drp1 mediates beta-amyloid-related mitochondrial fission and neuronal injury.

    Cho DH, Nakamura T, Fang J, Cieplak P, Godzik A, Gu Z and Lipton SA

    Center for Neuroscience, Aging, and Stem Cell Research, Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.

    Mitochondria continuously undergo two opposing processes, fission and fusion. The disruption of this dynamic equilibrium may herald cell injury or death and may contribute to developmental and neurodegenerative disorders. Nitric oxide functions as a signaling molecule, but in excess it mediates neuronal injury, in part via mitochondrial fission or fragmentation. However, the underlying mechanism for nitric oxide-induced pathological fission remains unclear. We found that nitric oxide produced in response to beta-amyloid protein, thought to be a key mediator of Alzheimer's disease, triggered mitochondrial fission, synaptic loss, and neuronal damage, in part via S-nitrosylation of dynamin-related protein 1 (forming SNO-Drp1). Preventing nitrosylation of Drp1 by cysteine mutation abrogated these neurotoxic events. SNO-Drp1 is increased in brains of human Alzheimer's disease patients and may thus contribute to the pathogenesis of neurodegeneration.

    Funded by: NEI NIH HHS: R01 EY005477, R01 EY005477-25, R01 EY05477; NICHD NIH HHS: P01 HD029587, P01 HD029587-16, P01 HD29587; NIEHS NIH HHS: P01 ES016738, P01 ES016738-01, P01 ES016738-02; NINDS NIH HHS: P30 NS057096, P30 NS057096-04

    Science (New York, N.Y.) 2009;324;5923;102-5

  • Amyloid beta peptides trigger CD47-dependent mast cell secretory and phagocytic responses.

    Niederhoffer N, Levy R, Sick E, Andre P, Coupin G, Lombard Y and Gies JP

    Université de Strasbourg, CNRS UMR 7213, Laboratoire de Biophotonique et Pharmacologie, Faculté de Pharmacie, Illkirch, France. Nathalie.niederhoffer@pharma.u-strasbg.fr

    Mast cells are found in the brain, where they contribute to immune responses. They have been implicated in multiple sclerosis, but their potential role in Alzheimers disease (AD), another inflammatory disease of the central nervous system, remains elusive. In the present study, we examined mast cell responses to amyloid beta (Abeta) peptides 1-40 and 1-42, the major components of the Alzheimer amyloid plaques. Rat peritoneal mast cells were used as experimental model for human brain serosal mast cells. Fibrillar Abeta1-40 and Ami1-42 peptides induced concentration-dependent exocytosis, as assessed by measurement of histamine secretion; exocytosis was reduced by pre-treatment with pertussis toxin and with antibodies against the CD47 receptor and the beta1-integrin subunit. Fibrillar Abeta1-40 and Abeta1- 42 peptides coated on heat-inactivated yeast particles and soluble fibrillar Abeta1-40 and Abeta1-42 peptides were also recognized and phagocyted by mast cells. Uptake of the peptides was decreased in the presence of 4N1, a peptide agonist of the CD47 receptor, but remained unchanged in the presence of 4NGG, a peptide derived from 4N1 which does not bind to CD47. Non-fibrillar forms of Abeta1-40 and 1-42 peptides were unable to elicit mast cell responses. These results show that fibrillar Abeta peptides can trigger mast cells and elicit exocytosis and phagocytosis. The Abeta-induced activation of mast cells operates through a CD47/beta1-integrin membrane complex coupled with Gi-protein. The present data support the hypothesis that mast cells, similarly to microglial cells, could play a major role in AD pathogenesis.

    International journal of immunopathology and pharmacology 2009;22;2;473-83

  • Dysmorphic findings in two cases of abeta/hypobetalipoproteinemia.

    Solomon BD, Mohan P and Tifft CJ

    Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA. solomonb@mail.nih.gov

    Clinical dysmorphology 2009;18;2;90-1

  • Increased frequency of alpha-synuclein in the substantia nigra in human immunodeficiency virus infection.

    Khanlou N, Moore DJ, Chana G, Cherner M, Lazzaretto D, Dawes S, Grant I, Masliah E, Everall IP and HNRC Group

    Department of Pathology and Laboratory Medicine, Division of Neuropathology, David Geffen School of Medicine, Ronald Reagan UCLA Medical Center, Los Angeles, California, USA.

    The frequency of neurodegenerative markers among long surviving human immunodeficiency virus (HIV)-infected individuals is unknown, therefore, the present study investigated the frequency of alpha-synuclein, beta-amyloid, and HIV-associated brain pathology in the brains of older HIV-infected individuals. We examined the substantia nigra of 73 clinically well-characterized HIV-infected individuals aged 50 to 76 years from the National NeuroAIDS Tissue Consortium. We also examined the frontal and temporal cortical regions of a subset of 36 individuals. Neuritic alpha-synuclein expression was found in 16% (12/73) of the substantia nigra of the HIV+cases and none of the older control cases (0/18). beta-Amyloid deposits were prevalent and found in nearly all of the HIV+cases (35/36). Despite these increases of degenerative pathology, HIV-associated brain pathology was present in only 10% of cases. Among older HIV+adults, HIV-associated brain pathology does not appear elevated; however, the frequency of both alpha-synuclein and beta-amyloid is higher than that found in older healthy persons. The increased prevalence of alpha-synuclein and beta-amyloid in the brains of older HIV-infected individuals may predict an increased risk of developing neurodegenerative disease.

    Funded by: NIMH NIH HHS: MH 62512, MH62512, R24 MH059745, R24 MH59745, U01 MH083506

    Journal of neurovirology 2009;15;2;131-8

  • Reduced amyloidogenic processing of the amyloid beta-protein precursor by the small-molecule Differentiation Inducing Factor-1.

    Myre MA, Washicosky K, Moir RD, Tesco G, Tanzi RE and Wasco W

    Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA. myre@chgr.mgh.harvard.edu

    The detection of cell cycle proteins in Alzheimer's disease (AD) brains may represent an early event leading to neurodegeneration. To identify cell cycle modifiers with anti-Abeta properties, we assessed the effect of Differentiation-Inducing Factor-1 (DIF-1), a unique, small-molecule from Dictyostelium discoideum, on the proteolysis of the amyloid beta-protein precursor (APP) in a variety of different cell types. We show that DIF-1 slows cell cycle progression through G0/G1 that correlates with a reduction in cyclin D1 protein levels. Western blot analysis of DIF-treated cells and conditioned medium revealed decreases in the levels of secreted APP, mature APP, and C-terminal fragments. Assessment of conditioned media by sandwich ELISA showed reduced levels of Abeta40 and Abeta42, also demonstrating that treatment with DIF-1 effectively decreases the ratio of Abeta42 to Abeta40. In addition, DIF-1 significantly diminished APP phosphorylation at residue T668. Interestingly, site-directed mutagenesis of APP residue Thr668 to alanine or glutamic acid abolished the effect of DIF-1 on APP proteolysis and restored secreted levels of Abeta. Finally, DIF-1 prevented the accumulation of APP C-terminal fragments induced by the proteasome inhibitor lactacystin, and calpain inhibitor N-acetyl-leucyl-leucyl-norleucinal (ALLN). Our findings suggest that DIF-1 affects G0/G1-associated amyloidogenic processing of APP by a gamma-secretase-, proteasome- and calpain-insensitive pathway, and that this effect requires the presence of residue Thr668.

    Funded by: NIA NIH HHS: AG015379, P01 AG015379, R01 AG016361

    Cellular signalling 2009;21;4;567-76

  • Interprotofilament interactions between Alzheimer's Abeta1-42 peptides in amyloid fibrils revealed by cryoEM.

    Zhang R, Hu X, Khant H, Ludtke SJ, Chiu W, Schmid MF, Frieden C and Lee JM

    Graduate Program in Structural and Computational Biology and Molecular Biophysics, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.

    Alzheimer's disease is a neurodegenerative disorder characterized by the accumulation of amyloid plaques in the brain. This amyloid primarily contains amyloid-beta (Abeta), a 39- to 43-aa peptide derived from the proteolytic cleavage of the endogenous amyloid precursor protein. The 42-residue-length Abeta peptide (Abeta(1-42)), the most abundant Abeta peptide found in plaques, has a much greater propensity to self-aggregate into fibrils than the other peptides and is believed to be more pathogenic. Synthetic human Abeta(1-42) peptides self-aggregate into stable but poorly-ordered helical filaments. We determined their structure to approximately 10-A resolution by using cryoEM and the iterative real-space reconstruction method. This structure reveals 2 protofilaments winding around a hollow core. Previous hairpin-like NMR models for Abeta(17-42) fit well in the cryoEM density map and reveal that the juxtaposed protofilaments are joined via the N terminus of the peptide from 1 protofilament connecting to the loop region of the peptide in the opposite protofilament. This model of mature Abeta(1-42) fibrils is markedly different from previous cryoEM models of Abeta(1-40) fibrils. In our model, the C terminus of Abeta forms the inside wall of the hollow core, which is supported by partial proteolysis analysis.

    Funded by: NCRR NIH HHS: P41RR02250; NEI NIH HHS: PN1EY016525; NIDDK NIH HHS: DK13332; NIGMS NIH HHS: R01 GM080139-03; NINDS NIH HHS: P01 NS032636, P01 NS032636-139001, R01 NS048283, R01 NS048283-03, R01 NS048283-04

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;12;4653-8

  • Amyloid beta-induced neuronal hyperexcitability triggers progressive epilepsy.

    Minkeviciene R, Rheims S, Dobszay MB, Zilberter M, Hartikainen J, Fülöp L, Penke B, Zilberter Y, Harkany T, Pitkänen A and Tanila H

    A. I. Virtanen Institute, University of Kuopio, FIN-70211 Kuopio, Finland.

    Alzheimer's disease is associated with an increased risk of unprovoked seizures. However, the underlying mechanisms of seizure induction remain elusive. Here, we performed video-EEG recordings in mice carrying mutant human APPswe and PS1dE9 genes (APdE9 mice) and their wild-type littermates to determine the prevalence of unprovoked seizures. In two recording episodes at the onset of amyloid beta (Abeta) pathogenesis (3 and 4.5 months of age), at least one unprovoked seizure was detected in 65% of APdE9 mice, of which 46% had multiple seizures and 38% had a generalized seizure. None of the wild-type mice had seizures. In a subset of APdE9 mice, seizure phenotype was associated with a loss of calbindin-D28k immunoreactivity in dentate granular cells and ectopic expression of neuropeptide Y in mossy fibers. In APdE9 mice, persistently decreased resting membrane potential in neocortical layer 2/3 pyramidal cells and dentate granule cells underpinned increased network excitability as identified by patch-clamp electrophysiology. At stimulus strengths evoking single-component EPSPs in wild-type littermates, APdE9 mice exhibited decreased action potential threshold and burst firing of pyramidal cells. Bath application (1 h) of Abeta1-42 or Abeta25-35 (proto-)fibrils but not oligomers induced significant membrane depolarization of pyramidal cells and increased the activity of excitatory cell populations as measured by extracellular field recordings in the juvenile rodent brain, confirming the pathogenic significance of bath-applied Abeta (proto-)fibrils. Overall, these data identify fibrillar Abeta as a pathogenic entity powerfully altering neuronal membrane properties such that hyperexcitability of pyramidal cells culminates in epileptiform activity.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2009;29;11;3453-62

  • A recessive mutation in the APP gene with dominant-negative effect on amyloidogenesis.

    Di Fede G, Catania M, Morbin M, Rossi G, Suardi S, Mazzoleni G, Merlin M, Giovagnoli AR, Prioni S, Erbetta A, Falcone C, Gobbi M, Colombo L, Bastone A, Beeg M, Manzoni C, Francescucci B, Spagnoli A, Cantù L, Del Favero E, Levy E, Salmona M and Tagliavini F

    Division of Neurology and Neuropathology, "Carlo Besta" National Neurological Institute, 20133 Milan, Italy.

    beta-Amyloid precursor protein (APP) mutations cause familial Alzheimer's disease with nearly complete penetrance. We found an APP mutation [alanine-673-->valine-673 (A673V)] that causes disease only in the homozygous state, whereas heterozygous carriers were unaffected, consistent with a recessive Mendelian trait of inheritance. The A673V mutation affected APP processing, resulting in enhanced beta-amyloid (Abeta) production and formation of amyloid fibrils in vitro. Co-incubation of mutated and wild-type peptides conferred instability on Abeta aggregates and inhibited amyloidogenesis and neurotoxicity. The highly amyloidogenic effect of the A673V mutation in the homozygous state and its anti-amyloidogenic effect in the heterozygous state account for the autosomal recessive pattern of inheritance and have implications for genetic screening and the potential treatment of Alzheimer's disease.

    Funded by: NINDS NIH HHS: NS42029, R01 NS042029-01A1, R01 NS042029-02, R01 NS042029-03, R01 NS042029-04, R01 NS042029-05, R01 NS042029-06

    Science (New York, N.Y.) 2009;323;5920;1473-7

  • Amyloid beta induces cellular relocalization and production of agrin and glypican-1.

    Timmer NM, van Horssen J, Otte-Holler I, Wilhelmus MM, David G, van Beers J, de Waal RM and Verbeek MM

    Department of Neurology, Laboratory of Pediatrics and Neurology, Donders Centre for Brain, Cognition and Behaviour, Alzheimer Centre Nijmegen, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. n.timmer@cukz.umcn.nl

    The major component of senile plaques and vascular amyloid in Alzheimer's disease (AD) brains is the amyloid beta protein (Abeta). Besides Abeta, several other proteins have been identified in these lesions, in particular heparan sulfate proteoglycans (HSPG). However, it is still unclear, what causes the excessive accumulation of HSPG in AD brains. Therefore, we investigated if Abeta may influence production and expression of two major Abeta-associated HSPG species, agrin and glypican-1. When human brain pericytes (HBP) were cultured in the presence of Abeta, protein and mRNA expression of both agrin and glypican-1 were increased and more radioactive sulfate was incorporated in the glycosaminoglycan fraction of Abeta-treated HBP. Furthermore, after Abeta treatment, these HSPG were found in association with the amyloid fibrils attached to the cell membrane, in contrast to the intracellular agrin and glypican-1 staining observed in untreated cells. We conclude that Abeta can modulate the cellular expression of agrin and glypican-1, which may contribute to the accumulation of these HSPG in AD lesions.

    Brain research 2009;1260;38-46

  • Oligomeric amyloid beta associates with postsynaptic densities and correlates with excitatory synapse loss near senile plaques.

    Koffie RM, Meyer-Luehmann M, Hashimoto T, Adams KW, Mielke ML, Garcia-Alloza M, Micheva KD, Smith SJ, Kim ML, Lee VM, Hyman BT and Spires-Jones TL

    Neurology Department, Massachusetts General Hospital, Charlestown, MA 02129, USA.

    Synapse loss correlates with a cognitive decline in Alzheimer's disease (AD), but whether this is caused by fibrillar deposits known as senile plaques or soluble oligomeric forms of amyloid beta (Abeta) is controversial. By using array tomography, a technique that combines ultrathin sectioning of tissue with immunofluorescence, allowing precise quantification of small structures, such as synapses, we have tested the hypothesis that oligomeric Abeta surrounding plaques contributes to synapse loss in a mouse model of AD. We find that senile plaques are surrounded by a halo of oligomeric Abeta. Analysis of >14,000 synapses (represented by PSD95-stained excitatory synapses) shows that there is a 60% loss of excitatory synapses in the halo of oligomeric Abeta surrounding plaques and that the density increases to reach almost control levels in volumes further than 50 microm from a plaque in an approximately linear fashion (linear regression, r(2) = 0.9; P < 0.0001). Further, in transgenic cortex, microdeposits of oligomeric Abeta associate with a subset of excitatory synapses, which are significantly smaller than those not in contact with oligomeric Abeta. The proportion of excitatory synapses associated with Abeta correlates with decreasing density (correlation, -0.588; P < 0.0001). These data show that senile plaques are a potential reservoir of oligomeric Abeta, which colocalizes with the postsynaptic density and is associated with spine collapse, reconciling the apparently competing schools of thought of "plaque" vs. "oligomeric Abeta" as the synaptotoxic species in the brain of AD patients.

    Funded by: NIA NIH HHS: 2 P50 AG05134-24, AG08487

    Proceedings of the National Academy of Sciences of the United States of America 2009;106;10;4012-7

  • Structural characterization of a soluble amyloid beta-peptide oligomer.

    Yu L, Edalji R, Harlan JE, Holzman TF, Lopez AP, Labkovsky B, Hillen H, Barghorn S, Ebert U, Richardson PL, Miesbauer L, Solomon L, Bartley D, Walter K, Johnson RW, Hajduk PJ and Olejniczak ET

    Pharmaceutical Discovery Division, GPRD, Abbott Laboratories, Abbott Park, Illinois 60064-6098, USA.

    Alzheimer's disease (AD) is a neurodegenerative disorder that is linked to the presence of amyloid beta-peptides that can form insoluble fibrils or soluble oligomeric assemblies. Soluble forms are present in the brains and tissues of Alzheimer's patients, and their presence correlates with disease progression. Long-lived soluble forms can be generated in vitro by using small amounts of aliphatic hydrocarbon chains of detergents or fatty acids in preparations of amyloid beta-peptides. Using NMR, we have characterized soluble oligomers of Abeta preglobulomer and globulomer that are stable and alter synaptic activity. The NMR data indicate that these soluble forms have a mixed parallel and antiparallel beta-sheet structure that is different from fibrils which contain only parallel beta-sheets. Using the structural data, we engineered a disulfide bond into the soluble Abeta globulomer to give a "new" soluble antigen that is stable, homogeneous, and binds with the same affinity to selective antibodies as the parent wt globulomer.

    Biochemistry 2009;48;9;1870-7

  • Angiotensin II AT2 receptor oligomers mediate G-protein dysfunction in an animal model of Alzheimer disease.

    AbdAlla S, Lother H, el Missiry A, Langer A, Sergeev P, el Faramawy Y and Quitterer U

    Heinrich-Pette-Institute, Martinistrasse 52, D-20251 Hamburg, Germany.

    Progressive neurodegeneration and decline of cognitive functions are major hallmarks of Alzheimer disease (AD). Neurodegeneration in AD correlates with dysfunction of diverse signal transduction mechanisms, such as the G-protein-stimulated phosphoinositide hydrolysis mediated by Galphaq/11. We report here that impaired Galphaq/11-stimulated signaling in brains of AD patients and mice correlated with the appearance of cross-linked oligomeric angiotensin II AT2 receptors sequestering Galphaq/11. Amyloid beta (Abeta) was causal to AT2 oligomerization, because cerebral microinjection of Abeta triggered AT2 oligomerization in the hippocampus of mice in a dose-dependent manner. Abeta induced AT2 oligomerization by a two-step process of oxidative and transglutaminase-dependent cross-linking. The induction of AT2 oligomers in a transgenic mouse model with AD-like symptoms was associated with Galphaq/11 dysfunction and enhanced neurodegeneration. Vice versa, stereotactic inhibition of AT2 oligomers by RNA interference prevented the impairment of Galphaq/11 and delayed Tau phosphorylation. Thus, Abeta induces the formation of cross-linked AT2 oligomers that contribute to the dysfunction of Galphaq/11 in an animal model of Alzheimer disease.

    The Journal of biological chemistry 2009;284;10;6554-65

  • The E693Delta mutation in amyloid precursor protein increases intracellular accumulation of amyloid beta oligomers and causes endoplasmic reticulum stress-induced apoptosis in cultured cells.

    Nishitsuji K, Tomiyama T, Ishibashi K, Ito K, Teraoka R, Lambert MP, Klein WL and Mori H

    Department of Neuroscience, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8585, Japan.

    The E693Delta mutation within the amyloid precursor protein (APP) has been suggested to cause dementia via the enhanced formation of synaptotoxic amyloid beta (Abeta) oligomers. However, this mutation markedly decreases Abeta secretion, implying the existence of an additional mechanism of neuronal dysfunction that is independent of extracellular Abeta. We therefore examined the effects of this mutation on both APP processing to produce Abeta as well as subcellular localization and accumulation of Abeta in transfected HEK293 and COS-7 cells. Both beta- and gamma-cleavage of mutant APP increased, indicating a lack of inhibition in Abeta production. Instead, this mutation promoted Abeta accumulation within cells, including the endoplasmic reticulum (ER), Golgi apparatus, early and late endosomes, lysosomes, and autophagosomes, all of which have been proposed as intracellular sites of Abeta generation and/or degradation, suggesting impairment of APP/Abeta trafficking. Notably, the intracellular mutant Abeta was found to predominantly form oligomers. Concomitant with this accumulation, the ER stress markers Grp78 and phosphorylated eIF2alpha were both strongly induced. Furthermore, the activation of caspase-4 and -3 as well as DNA fragmentation were detected in these cells. These results suggest that mutant Abeta induces alteration of Abeta trafficking and subsequent ER stress-induced apoptosis via enhancement of its intracellular oligomerization. Our findings suggest that Abeta oligomers exhibit toxicity in the extracellular space and within the cells themselves.

    The American journal of pathology 2009;174;3;957-69

  • The insulin/Akt signaling pathway is targeted by intracellular beta-amyloid.

    Lee HK, Kumar P, Fu Q, Rosen KM and Querfurth HW

    Department of Neurology, Caritas St. Elizabeth's Medical Center, Tufts University School of Medicine, Boston, MA 02135, USA.

    Intraneuronal beta-amyloid (Abeta(i)) accumulates early in Alzheimer's disease (AD) and inclusion body myositis. Several organelles, receptor molecules, homeostatic processes, and signal transduction components have been identified as sensitive to Abeta. Although prior studies implicate the insulin-PI3K-Akt signaling cascade, a specific step within this or any essential metabolic or survival pathway has not emerged as a molecular target. We tested the effect of Abeta42 on each component of this cascade. In AD brain, the association between PDK and Akt, phospho-Akt levels and its activity were all decreased relative to control. In cell culture, Abeta(i) expression inhibited both insulin-induced Akt phosphorylation and activity. In vitro experiments identified that beta-amyloid (Abeta), especially oligomer preparations, specifically interrupted the PDK-dependent activation of Akt. Abeta(i) also blocked the association between PDK and Akt in cell-based and in vitro experiments. Importantly, Abeta did not interrupt Akt or PI3K activities (once stimulated) nor did it affect more proximal signal events. These results offer a novel therapeutic strategy to neutralize Abeta-induced energy failure and neuronal death.

    Funded by: DS NIH HHS: DS 41373; NIMH NIH HHS: R24 MH068855, R24-MH068855

    Molecular biology of the cell 2009;20;5;1533-44

  • Abeta(1-42) stimulated T cells express P-PKC-delta and P-PKC-zeta in Alzheimer disease.

    Miscia S, Ciccocioppo F, Lanuti P, Velluto L, Bascelli A, Pierdomenico L, Genovesi D, Di Siena A, Santavenere E, Gambi F, Ausili-Cèfaro G, Grimley PM, Marchisio M and Gambi D

    Cell Signalling Unit, Department of Biomorphology, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy. s.miscia@morpho.unich.it

    The protein kinase C (PKC) family of enzymes is a regulator of transmembrane signal transduction, and involvement of some PKC isoforms in T-cell activation has been demonstrated. Nevertheless, very little is known about their involvement in the Amyloid beta (Abeta)-dependent molecular signals in the T lymphocytes of Alzheimer disease (AD) patients. Therefore, the aim of this study was to investigate the involvement of PKC-alpha, PKC-delta and PKC-zeta expression and activity in the signaling machinery activated in Abeta-reactive T cells, in adult healthy individuals, elderly healthy subjects, and from patients with AD. The results show that in peripheral T-cells from early AD patients, Abeta(1-42) produced a distinct subpopulation highly expressing P-PKC-delta, while in severe AD patients the same treatment induced two distinct P-PKC-delta and P-PKC-zeta T-cell subpopulations. Such subpopulations were not noticeable following CD3/CD28 treatment of the same samples or after treatment of peripheral T cells from healthy adult or elderly subjects with Abeta(1-42) or with CD3/CD28. We believe that these findings may be of help in possible attempts to develop further diagnostic strategies useful for the characterization of AD.

    Neurobiology of aging 2009;30;3;394-406

  • Assessment of beta-amyloid deposits in human brain: a study of the BrainNet Europe Consortium.

    Alafuzoff I, Thal DR, Arzberger T, Bogdanovic N, Al-Sarraj S, Bodi I, Boluda S, Bugiani O, Duyckaerts C, Gelpi E, Gentleman S, Giaccone G, Graeber M, Hortobagyi T, Höftberger R, Ince P, Ironside JW, Kavantzas N, King A, Korkolopoulou P, Kovács GG, Meyronet D, Monoranu C, Nilsson T, Parchi P, Patsouris E, Pikkarainen M, Revesz T, Rozemuller A, Seilhean D, Schulz-Schaeffer W, Streichenberger N, Wharton SB and Kretzschmar H

    Department of Clinical Medicine, Kuopio University, Finland. irina.alafuzoff@uku.fi

    beta-Amyloid (A-beta) related pathology shows a range of lesions which differ both qualitatively and quantitatively. Pathologists, to date, mainly focused on the assessment of both of these aspects but attempts to correlate the findings with clinical phenotypes are not convincing. It has been recently proposed in the same way as iota and alpha synuclein related lesions, also A-beta related pathology may follow a temporal evolution, i.e. distinct phases, characterized by a step-wise involvement of different brain-regions. Twenty-six independent observers reached an 81% absolute agreement while assessing the phase of A-beta, i.e. phase 1 = deposition of A-beta exclusively in neocortex, phase 2 = additionally in allocortex, phase 3 = additionally in diencephalon, phase 4 = additionally in brainstem, and phase 5 = additionally in cerebellum. These high agreement rates were reached when at least six brain regions were evaluated. Likewise, a high agreement (93%) was reached while assessing the absence/presence of cerebral amyloid angiopathy (CAA) and the type of CAA (74%) while examining the six brain regions. Of note, most of observers failed to detect capillary CAA when it was only mild and focal and thus instead of type 1, type 2 CAA was diagnosed. In conclusion, a reliable assessment of A-beta phase and presence/absence of CAA was achieved by a total of 26 observers who examined a standardized set of blocks taken from only six anatomical regions, applying commercially available reagents and by assessing them as instructed. Thus, one may consider rating of A-beta-phases as a diagnostic tool while analyzing subjects with suspected Alzheimer's disease (AD). Because most of these blocks are currently routinely sampled by the majority of laboratories, assessment of the A-beta phase in AD is feasible even in large scale retrospective studies.

    Funded by: Parkinson's UK: G-0909

    Acta neuropathologica 2009;117;3;309-20

  • E22Q-mutant Abeta peptide (AbetaDutch) increases vascular but reduces parenchymal Abeta deposition.

    Herzig MC, Eisele YS, Staufenbiel M and Jucker M

    Department of Cellular Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, Otfried-Müller Strasse 27, D-72076 Tübingen, Germany.

    Patients that have hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D) generate both wild-type beta-amyloid (Abetawt) and E22Q-mutant beta-amyloid (AbetaDutch). Postmortem analysis of HCHWA-D brains reveals severe cerebral amyloid angiopathy with very little parenchymal amyloid deposition. To investigate amyloidosis in the presence of both Abetawt and AbetaDutch variants, transgenic (tg) APP23 mice were crossed with APPDutch mice. Although single-tg APP23 mice deposited Abetawt with aging, double-tg APP23/APPDutch mice co-deposited AbetaDutch (mainly AbetaDutch1-40) and Abetawt at twofold higher total Abeta levels. Vascular Abeta deposits and hemorrhages were twice as high in APP23/APPDutch mice compared with APP23 mice. Surprisingly, parenchymal Abeta deposition was reduced in the double-tg mice compared with the single-tg APP23 mice. Our findings suggest that AbetaDutch1-40 inhibits parenchymal amyloidosis but exacerbates vascular amyloid, hence explaining the compartment-specific distribution of cerebral amyloid in HCHWA-D patients.

    The American journal of pathology 2009;174;3;722-6

  • Inverse association of cortisol serum levels with T-tau, P-tau 181 and P-tau 231 peptide levels and T-tau/Abeta 1-42 ratios in CSF in patients with mild Alzheimer's disease dementia.

    Laske C, Stransky E, Fritsche A, Eschweiler GW and Leyhe T

    Dept. of Psychiatry and Psychotherapy, University of Tuebingen, Osianderstr. 24, 72076, Tuebingen, Germany. christoph.laske@med.uni-tuebingen.de

    Hypercortisolemia and increased levels of hyperphosphorylated tau proteins in cerebrospinal fluid (CSF) are common features with pathogenic relevance in Alzheimer;s disease (AD). Experimental studies point to an influence of cortisol on Abeta and tau pathology in AD. Association of both parameters have not yet been described in a sample of AD patients. In the present study, serum levels of cortisol were determined in 26 patients with mild AD dementia and 20 age-matched healthy elderly controls by ELISA. In addition, we measured in AD patients CSF levels of cortisol, total tau (T-tau), tau phosphorylated at threonine 181 (P-tau 181), tau protein phosphorylated at threonine 231 (P-tau 231) and beta-Amyloid (Abeta) 1-42 and determined T-tau/Abeta 1-42 ratios in CSF. We found in AD patients significantly increased cortisol serum levels (551.4 +/- 146.1 nmol/l; P = 0.002) as compared to healthy controls (435.3 +/- 83.9 nmol/l). In AD patients, cortisol serum levels were significantly inversely correlated with T-tau (r = -0.496; P = 0.01), P-tau 181 (r = -0.558; P = 0.003) and P-tau 231 (-0.500; P = 0.009) protein levels and T-tau/Abeta 1-42 ratios (r = -0.450; P = 0.021) in CSF. In addition, cortisol serum levels showed a trend of positive correlation with Abeta 1-42 CSF levels (r = 0.386; P = 0.052). However, no significant correlations of cortisol serum with CSF levels as well as cortisol CSF levels with CSF biomarkers could be detected in AD patients. In conclusion, our results show that increased cortisol serum but not CSF levels are associated with minor signs of AD pathology in CSF, indicating a putative neuroprotective effect of moderately elevated cortisol serum levels in patients with mild AD dementia.

    European archives of psychiatry and clinical neuroscience 2009;259;2;80-5

  • JNK regulates APP cleavage and degradation in a model of Alzheimer's disease.

    Colombo A, Bastone A, Ploia C, Sclip A, Salmona M, Forloni G and Borsello T

    Istituto di Ricerche Farmacologiche Mario Negri, Via La Masa 19, 20156 Milano, Italy.

    Secretion of Amyloid-beta peptide (Abeta) circulating oligomers and their aggregate forms derived by processing of beta-amyloid precursor protein (APP) are a key event in Alzheimer's disease (AD). We show that phosphorylation of APP on threonine 668 may play a role in APP metabolism in H4-APP(sw) cell line, a degenerative AD model. We proved that JNK plays a fundamental role in this phosphorylation since its specific inhibition, with the JNK inhibitor peptide (D-JNKI1), induced APP degradation and prevented APP phosphorylation at T668. This results in a significant drop of betaAPPs, Abeta fragments and Abeta circulating oligomers. Moreover the D-JNKI1 treatment produced a switch in the APP metabolism, since the peptide reduced the rate of the amyloidogenic processing in favour of the non-amyloidogenic one. All together our results suggest an important link between APP metabolism and the JNK pathway and contribute to shed light on the molecular signalling pathway of this disease indicating JNK as an innovative target for AD therapy.

    Neurobiology of disease 2009;33;3;518-25

  • Overexpression of wild-type human APP in mice causes cognitive deficits and pathological features unrelated to Abeta levels.

    Simón AM, Schiapparelli L, Salazar-Colocho P, Cuadrado-Tejedor M, Escribano L, López de Maturana R, Del Río J, Pérez-Mediavilla A and Frechilla D

    Division of Neurosciences, CIMA, University of Navarra, Av. Pio XII 55, 31008 Pamplona, Spain.

    Transgenic mice expressing mutant human amyloid precursor protein (APP) develop an age-dependent amyloid pathology and memory deficits, but no overt neuronal loss. Here, in mice overexpressing wild-type human APP (hAPP(wt)) we found an early memory impairment, particularly in the water maze and to a lesser extent in the object recognition task, but beta-amyloid peptide (Abeta(42)) was barely detectable in the hippocampus. In these mice, hAPP processing was basically non-amyloidogenic, with high levels of APP carboxy-terminal fragments, C83 and APP intracellular domain. A tau pathology with an early increase in the levels of phosphorylated tau in the hippocampus, a likely consequence of enhanced ERK1/2 activation, was also observed. Furthermore, these mice presented a loss of synapse-associated proteins: PSD95, AMPA and NMDA receptor subunits and phosphorylated CaMKII. Importantly, signs of neurodegeneration were found in the hippocampal CA1 subfield and in the entorhinal cortex that were associated to a marked loss of MAP2 immunoreactivity. Conversely, in mice expressing mutant hAPP, high levels of Abeta(42) were found in the hippocampus, but no signs of neurodegeneration were apparent. The results support the notion of Abeta-independent pathogenic pathways in Alzheimer's disease.

    Neurobiology of disease 2009;33;3;369-78

  • IGF-1 promotes beta-amyloid production by a secretase-independent mechanism.

    Araki W, Kume H, Oda A, Tamaoka A and Kametani F

    Department of Demyelinating Disease and Aging, National Institute of Neuroscience, NCNP, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan. araki@ncnp.go.jp

    Beta-amyloid peptide (Abeta) is generated via the sequential proteolysis of beta-amyloid precursor protein (APP) by beta- and gamma-secretases, and plays a crucial role in the pathogenesis of Alzheimer's disease (AD). Here, we sought to clarify the role of insulin-like growth factor-1 (IGF-1), implicated in the AD pathomechanism, in the generation of Abeta. Treatment of neuroblastoma SH-SY5Y cells expressing AD-associated Swedish mutant APP with IGF-1 did not alter cellular levels of APP, but significantly increased those of beta-C-terminal fragment (beta-CTF) and secreted Abeta. IGF-1 also enhanced APP phosphorylation at Thr668. Treatment of beta-CTF-expressing cells with IGF-1 increased the levels of beta-CTF and secreted Abeta. The IGF-1-induced augmentation of beta-CTF was observed in the presence of gamma-secretase inhibitors, but not in cells expressing beta-CTF with a Thr668 to alanine substitution. These results suggest that IGF-1 promotes Abeta production through a secretase-independent mechanism involving APP phosphorylation.

    Biochemical and biophysical research communications 2009;380;1;111-4

  • Cellular prion protein mediates impairment of synaptic plasticity by amyloid-beta oligomers.

    Laurén J, Gimbel DA, Nygaard HB, Gilbert JW and Strittmatter SM

    Cellular Neuroscience, Neurodegeneration and Repair Program, Yale University School of Medicine, New Haven, Connecticut 06536, USA.

    A pathological hallmark of Alzheimer's disease is an accumulation of insoluble plaque containing the amyloid-beta peptide of 40-42 amino acid residues. Prefibrillar, soluble oligomers of amyloid-beta have been recognized to be early and key intermediates in Alzheimer's-disease-related synaptic dysfunction. At nanomolar concentrations, soluble amyloid-beta oligomers block hippocampal long-term potentiation, cause dendritic spine retraction from pyramidal cells and impair rodent spatial memory. Soluble amyloid-beta oligomers have been prepared from chemical syntheses, transfected cell culture supernatants, transgenic mouse brain and human Alzheimer's disease brain. Together, these data imply a high-affinity cell-surface receptor for soluble amyloid-beta oligomers on neurons-one that is central to the pathophysiological process in Alzheimer's disease. Here we identify the cellular prion protein (PrP(C)) as an amyloid-beta-oligomer receptor by expression cloning. Amyloid-beta oligomers bind with nanomolar affinity to PrP(C), but the interaction does not require the infectious PrP(Sc) conformation. Synaptic responsiveness in hippocampal slices from young adult PrP null mice is normal, but the amyloid-beta oligomer blockade of long-term potentiation is absent. Anti-PrP antibodies prevent amyloid-beta-oligomer binding to PrP(C) and rescue synaptic plasticity in hippocampal slices from oligomeric amyloid-beta. Thus, PrP(C) is a mediator of amyloid-beta-oligomer-induced synaptic dysfunction, and PrP(C)-specific pharmaceuticals may have therapeutic potential for Alzheimer's disease.

    Funded by: NIDA NIH HHS: P30 DA018343; NINDS NIH HHS: R01 NS039962, R01 NS039962-09, R01 NS042304, R01 NS042304-08, R37 NS033020, R37 NS033020-17; PHS HHS: 5T32GN07205

    Nature 2009;457;7233;1128-32

  • APP binds DR6 to trigger axon pruning and neuron death via distinct caspases.

    Nikolaev A, McLaughlin T, O'Leary DD and Tessier-Lavigne M

    Division of Research, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, USA.

    Naturally occurring axonal pruning and neuronal cell death help to sculpt neuronal connections during development, but their mechanistic basis remains poorly understood. Here we report that beta-amyloid precursor protein (APP) and death receptor 6 (DR6, also known as TNFRSF21) activate a widespread caspase-dependent self-destruction program. DR6 is broadly expressed by developing neurons, and is required for normal cell body death and axonal pruning both in vivo and after trophic-factor deprivation in vitro. Unlike neuronal cell body apoptosis, which requires caspase 3, we show that axonal degeneration requires caspase 6, which is activated in a punctate pattern that parallels the pattern of axonal fragmentation. DR6 is activated locally by an inactive surface ligand(s) that is released in an active form after trophic-factor deprivation, and we identify APP as a DR6 ligand. Trophic-factor deprivation triggers the shedding of surface APP in a beta-secretase (BACE)-dependent manner. Loss- and gain-of-function studies support a model in which a cleaved amino-terminal fragment of APP (N-APP) binds DR6 and triggers degeneration. Genetic support is provided by a common neuromuscular junction phenotype in mutant mice. Our results indicate that APP and DR6 are components of a neuronal self-destruction pathway, and suggest that an extracellular fragment of APP, acting via DR6 and caspase 6, contributes to Alzheimer's disease.

    Funded by: NEI NIH HHS: R01 EY007025, R01 EY007025-24, R01 EY07025; NIA NIH HHS: R01 AG025970

    Nature 2009;457;7232;981-9

  • Decrease of dynamin 2 levels in late-onset Alzheimer's disease alters Abeta metabolism.

    Kamagata E, Kudo T, Kimura R, Tanimukai H, Morihara T, Sadik MG, Kamino K and Takeda M

    Department of Geriatric Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, Japan.

    Late-onset Alzheimer's disease (LOAD) is significantly associated with a single nucleotide polymorphism located in the dynamin (DNM) 2 gene, especially in non-carriers of the apolipoprotein E-epsilon4 allele. In this study we used real-time PCR to show that DNM2 mRNA is significantly reduced in the cortex of AD brains and in the peripheral blood of dementia patients. Neuroblastoma cells transfected with a dominant negative DNM2 had increased amyloid beta protein (Abeta) secretion and most of the amyloid precursor protein (APP) in these cells was localized to the plasma membrane. In addition, these cells were rich in flotillin, which is a component of lipid rafts. These data suggest that DNM2 expression is reduced in LOAD, which results in the accumulation of APP in lipid raft-rich plasma membranes. Consequently, Abeta secretion may increase in LOAD neurons.

    Biochemical and biophysical research communications 2009;379;3;691-5

  • Oligomeric amyloid-beta(1-42) induces THP-1 human monocyte adhesion and maturation.

    Crouse NR, Ajit D, Udan ML and Nichols MR

    Department of Chemistry and Biochemistry and Center for Nanoscience, University of Missouri-St. Louis, One University Boulevard, St. Louis, MO 63121, USA.

    Amyloid-beta (Abeta) is a naturally occurring 40- or 42-residue peptide fragment with a primary role in Alzheimer's disease (AD). Aggregated Abeta accumulates as both dense core plaques and diffuse deposits in the brains of AD patients. Abeta plaques are surrounded by activated microglia, some of which are believed to be derived from peripheral blood monocytes that have infiltrated the central nervous system and differentiated into phagocytes in response to Abeta. We have modeled this process using THP-1 human monocytes and found Abeta(1-42) to be as effective as phorbol myristate acetate at differentiating THP-1 monocytes based on cell adhesion, fibronectin binding, CD11b cell-surface expression, and morphological changes. Cell adhesion studies and atomic force microscopy imaging revealed an inverse correlation between Abeta(1-42)-induced monocyte maturation and aggregation progression. Freshly reconstituted Abeta(1-42) solutions were the most effective, yet continued aggregation reduced, and eventually abolished, the ability to induce monocyte adhesion. Abeta(1-40), lower aggregation concentrations of Abeta(1-42), and an aggregation-restricted Abeta(1-42) L34P mutant had little effect on monocyte adhesion under the same conditions as Abeta(1-42). These findings implicated an oligomeric, but not monomeric or fibrillar, Abeta(1-42) aggregation species in the monocyte maturation process. The rapidly-formed Abeta(1-42) oligomers were distinct from Abeta-derived diffusible ligands which did not elicit significant THP-1 monocyte adhesion. These data demonstrate that a specific oligomeric Abeta(1-42) aggregation species can potently initiate the THP-1 monocyte maturation process.

    Brain research 2009;1254;109-19

  • Abnormal cleavage of APP impairs its functions in cell adhesion and migration.

    Sheng B, Song B, Zheng Z, Zhou F, Lu G, Zhao N, Zhang X and Gong Y

    State Key Laboratory of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China.

    Amyloid precursor protein (APP) is expressed ubiquitously but its wrong cleavage only occurs in central nervous system. In this research, overexpression of wild type human APP695 was found to stimulate the adhesion and migration of N2a cells. In the cells co-transfected by familial Alzheimer's disease (FAD)-linked Swedish mutant of APP695 gene plus big up tri, openE9 deleted presenilin1 gene (N2a/Swe. big up tri, open9), however, this stimulating function was impaired compared to that in the cells co-transfected by Swedish mutant of APP695 gene plus dominant negative mutant of presenilin1 D385A gene (N2a/Swe.385). Furthermore, it was also found that the phosphorylation of FAK Tyr-861 and GSK-3beta Ser-9 was reduced in N2a/Swe.Delta9 cells, which can be possibly taken as a reasonable explanation for the underlying mechanism. Our results suggest that impaired cell adhesion and migration induced by abnormal cleavage of APP could contribute to the pathological effects in FAD brain.

    Neuroscience letters 2009;450;3;327-31

  • Alzheimer disease Abeta production in the absence of S-palmitoylation-dependent targeting of BACE1 to lipid rafts.

    Vetrivel KS, Meckler X, Chen Y, Nguyen PD, Seidah NG, Vassar R, Wong PC, Fukata M, Kounnas MZ and Thinakaran G

    Department of Neurobiology, Neurology, and Pathology, The University of Chicago, Chicago, Illinois 60637, USA.

    Alzheimer disease beta-amyloid (Abeta) peptides are generated via sequential proteolysis of amyloid precursor protein (APP) by BACE1 and gamma-secretase. A subset of BACE1 localizes to cholesterol-rich membrane microdomains, termed lipid rafts. BACE1 processing in raft microdomains of cultured cells and neurons was characterized in previous studies by disrupting the integrity of lipid rafts by cholesterol depletion. These studies found either inhibition or elevation of Abeta production depending on the extent of cholesterol depletion, generating controversy. The intricate interplay between cholesterol levels, APP trafficking, and BACE1 processing is not clearly understood because cholesterol depletion has pleiotropic effects on Golgi morphology, vesicular trafficking, and membrane bulk fluidity. In this study, we used an alternate strategy to explore the function of BACE1 in membrane microdomains without altering the cellular cholesterol level. We demonstrate that BACE1 undergoes S-palmitoylation at four Cys residues at the junction of transmembrane and cytosolic domains, and Ala substitution at these four residues is sufficient to displace BACE1 from lipid rafts. Analysis of wild type and mutant BACE1 expressed in BACE1 null fibroblasts and neuroblastoma cells revealed that S-palmitoylation neither contributes to protein stability nor subcellular localization of BACE1. Surprisingly, non-raft localization of palmitoylation-deficient BACE1 did not have discernible influence on BACE1 processing of APP or secretion of Abeta. These results indicate that post-translational S-palmitoylation of BACE1 is not required for APP processing, and that BACE1 can efficiently cleave APP in both raft and non-raft microdomains.

    Funded by: NIA NIH HHS: AG019070, AG021495, R01 AG019070

    The Journal of biological chemistry 2009;284;6;3793-803

  • Oxidative stress induces macroautophagy of amyloid beta-protein and ensuing apoptosis.

    Zheng L, Kågedal K, Dehvari N, Benedikz E, Cowburn R, Marcusson J and Terman A

    Division of Geriatric Medicine, Linköping University, SE-581 85 Linköping, Sweden. lin.zheng@liu.se

    There is increasing evidence for the toxicity of intracellular amyloid beta-protein (Abeta) to neurons and the involvement of lysosomes in this process in Alzheimer disease (AD). We have recently shown that oxidative stress, a recognized determinant of AD, enhances macroautophagy and leads to intralysosomal accumulation of Abeta in cultured neuroblastoma cells. We hypothesized that oxidative stress promotes AD by stimulating macroautophagy of Abeta that further may induce cell death by destabilizing lysosomal membranes. To investigate such possibility, we compared the effects of hyperoxia (40% ambient oxygen) in cultured HEK293 cells that were transfected with an empty vector (Vector), wild-type APP (APPwt), or Swedish mutant APP (APPswe). Exposure to hyperoxia for 5 days increased the number of cells with Abeta-containing lysosomes, as well as the number of apoptotic cells, compared to normoxic conditions. The rate of apoptosis in all three cell lines demonstrated dependence on intralysosomal Abeta content (Vector<APPwt<APPswe). Furthermore, the degree of apoptosis was positively correlated with lysosomal membrane permeabilization, whereas inhibitors of macroautophagy and lysosomal function decreased oxidant-induced apoptosis and diminished the differences in apoptotic response between different cell lines. These results suggest that oxidative stress can induce neuronal death through macroautophagy of Abeta and consequent lysosomal membrane permeabilization, which may help explain the mechanisms behind neuronal loss in AD.

    Free radical biology & medicine 2009;46;3;422-9

  • Subcellular localization and dimerization of APLP1 are strikingly different from APP and APLP2.

    Kaden D, Voigt P, Munter LM, Bobowski KD, Schaefer M and Multhaup G

    Institut für Chemie und Biochemie, Freie Universität Berlin, Berlin, Germany.

    The molecular association between APP and its mammalian homologs has hardly been explored. In systematically addressing this issue, we show by live cell imaging that APLP1 mainly localizes to the cell surface, whereas APP and APLP2 are mostly found in intracellular compartments. Homo- and heterotypic cis interactions of APP family members could be detected by FRET and co-immunoprecipitation analysis and occur in a modular mode. Only APLP1 formed trans interactions, supporting the argument for a putative specific role of APLP1 in cell adhesion. Deletion mutants of APP family members revealed two highly conserved regions as important for the protein crosstalk. In particular, the N-terminal half of the ectodomain was crucial for APP and APLP2 interactions. By contrast, multimerization of APLP1 was only partially dependent on this domain but strongly on the C-terminal half of the ectodomain. We further observed that coexpression of APP with APLP1 or APLP2 leads to diminished generation of Abeta42. The current data suggest that this is due to the formation of heteromeric complexes, opening the way for novel therapeutic strategies targeting these complexes.

    Journal of cell science 2009;122;Pt 3;368-77

  • A specific enzyme-linked immunosorbent assay for measuring beta-amyloid protein oligomers in human plasma and brain tissue of patients with Alzheimer disease.

    Xia W, Yang T, Shankar G, Smith IM, Shen Y, Walsh DM and Selkoe DJ

    Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, HIM 616, 77 Ave Louis Pasteur, Boston, MA 02115, USA. wxia@rics.bwh.harvard.edu

    Objective: To examine in vivo levels of beta-amyloid (Abeta) oligomers (oAbeta) vs monomeric Abeta in plasma and brain tissue of patients with sporadic and familial Alzheimer disease (AD) using a new enzyme-linked immunosorbent assay (ELISA) specific for oAbeta.

    Design: To establish the oAbeta ELISA, the same N-terminal Abeta antibody was used for antigen capture and detection. Plasma and postmortem brain tissue from patients with AD and control subjects were systematically analyzed by conventional monomeric Abeta and new oAbeta ELISAs.

    Subjects: We measured oAbeta species in plasma samples from 36 patients with clinically well-characterized AD and 10 control subjects. In addition, postmortem samples were obtained from brain autopsies of 9 patients with verified AD and 7 control subjects.

    Oligomeric Abeta and 4 monomeric Abeta species in plasma samples from patients with AD and control subjects were measured by ELISA.

    Results: The specificity of the oAbeta ELISA was validated with a disulfide-crossed-linked, synthetic Abeta(1-40)Ser26Cys dimer that was specifically detected before but not after the dissociation of the dimers in beta-mercaptoethanol. Plasma assays showed that relative oAbeta levels were closely associated with relative Abeta(42) monomer levels across all of the subjects. Analysis of sequential plasma samples from a subset of the patients with AD, including a patient with AD caused by a presenilin mutation, revealed decreases in both oAbeta and Abeta(42) monomer levels over a 1- to 2-year period. In brain tissue from 9 patients with AD and 7 control subjects, both oAbeta and monomeric Abeta(42) levels were consistently higher in the AD cases.

    Conclusions: An oAbeta-specific ELISA reveals a tight link between oAbeta and Abeta(42) monomer levels in plasma and brain. Both forms can decline over time in plasma, presumably reflecting their increasing insolubility in the brain.

    Funded by: NIA NIH HHS: AG015379, P01 AG015379, P01 AG015379-05, P01 AG015379-06, P01 AG015379-07, P01 AG015379-08, R01 AG025888, R01 AG025888-03; Wellcome Trust: 067660

    Archives of neurology 2009;66;2;190-9

  • Alzheimer's disease risk variants show association with cerebrospinal fluid amyloid beta.

    Kauwe JS, Wang J, Mayo K, Morris JC, Fagan AM, Holtzman DM and Goate AM

    Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA.

    The use of quantitative endophenotypes in genetic studies may provide greater power, allowing for the use of powerful statistical methods and a biological model for the effects of the disease-associated genetic variation. Cerebrospinal fluid (CSF) amyloid beta (Abeta) levels are promising endophenotypes for late-onset Alzheimer's disease (LOAD) and show correlation with LOAD status and Abeta deposition. In this study, we investigated 29 single nucleotide polymorphisms (SNPs) positive in AlzGene ( http://www.alzgene.org ) meta-analyses, for association with CSF Abeta levels in 313 individuals. This study design makes it possible to replicate reported LOAD risk alleles while contributing novel information about the mechanism by which they might affect that risk. Alleles in ACE, APOE, BDNF, DAPK1, and TF are significantly associated with CSF Abeta levels. In vitro analysis of the TF SNP showed a change in secreted Abeta consistent with the CSF phenotype and known Alzheimer's disease variants, demonstrating the utility of this approach in identifying SNPs that influence risk for disease via an Abeta-related mechanism.

    Funded by: NCATS NIH HHS: UL1 TR000448; NCRR NIH HHS: 1-KL2-RR024994-01, 1-TL1-RR024995-01, KL2 RR024994, TL1 RR024995, UL1 RR024992; NIA NIH HHS: P01 AG003991, P01 AG003991-268686, P01 AG026276, P01 AG026276-03, P01-AG026276, P01-AG03991, P50 AG005681, P50 AG005681-229010, P50-AG05681, R01 AG016208, R01 AG016208-09, R01 AG016208-09S1, R01-AG16208; NIMH NIH HHS: T32 MH014677, T32 MH14677; NINDS NIH HHS: P30 NS057105, P30 NS057105-03; PHS HHS: P30-N5057105

    Neurogenetics 2009;10;1;13-7

  • Alzheimer disease macrophages shuttle amyloid-beta from neurons to vessels, contributing to amyloid angiopathy.

    Zaghi J, Goldenson B, Inayathullah M, Lossinsky AS, Masoumi A, Avagyan H, Mahanian M, Bernas M, Weinand M, Rosenthal MJ, Espinosa-Jeffrey A, de Vellis J, Teplow DB and Fiala M

    Department of Orthopaedic Surgery, UCLA-Orthopaedic Hospital Research Center, Los Angeles, CA 90095-7358, USA.

    Neuronal accumulation of oligomeric amyloid-beta (Alphabeta) is considered the proximal cause of neuronal demise in Alzheimer disease (AD) patients. Blood-borne macrophages might reduce Abeta stress to neurons by immigration into the brain and phagocytosis of Alphabeta. We tested migration and export across a blood-brain barrier model, and phagocytosis and clearance of Alphabeta by AD and normal subjects' macrophages. Both AD and normal macrophages were inhibited in Alphabeta export across the blood-brain barrier due to adherence of Abeta-engorged macrophages to the endothelial layer. In comparison to normal subjects' macrophages, AD macrophages ingested and cleared less Alphabeta, and underwent apoptosis upon exposure to soluble, protofibrillar, or fibrillar Alphabeta. Confocal microscopy of stained AD brain sections revealed oligomeric Abeta in neurons and apoptotic macrophages, which surrounded and infiltrated congophilic microvessels, and fibrillar Abeta in plaques and microvessel walls. After incubation with AD brain sections, normal subjects' monocytes intruded into neurons and uploaded oligomeric Abeta. In conclusion, in patients with AD, macrophages appear to shuttle Abeta from neurons to vessels where their apoptosis may release fibrillar Abeta, contributing to cerebral amyloid angiopathy.

    Funded by: NIA NIH HHS: AG027818, P01 AG027818

    Acta neuropathologica 2009;117;2;111-24

  • Elucidation of O-glycosylation structures of the beta-amyloid precursor protein by liquid chromatography-mass spectrometry using electron transfer dissociation and collision induced dissociation.

    Perdivara I, Petrovich R, Allinquant B, Alliquant B, Deterding LJ, Tomer KB and Przybylski M

    National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.

    Accumulation and deposition of beta-amyloid peptide, a major constituent in neuritic plaques are hallmarks of Alzheimer's disease (AD) and AD-related neurodegenerative diseases. beta-Amyloid (Abeta) is derived from the proteolytic cleavage of amyloid precursor protein (APP), a transmembrane protein present in three major isoforms in brain comprising 695, 751 and 770 amino acids, respectively. Among other post-translational modifications, APP is modified during maturation by N- and O-glycosylation, which are thought to be responsible for its expression and secretion. Unlike N-glycosylation, no sites of O-glycosylation of APP have previously been reported. We report here the identification of three specific O-glycosylation sites of the secreted APP695 (sAPP695) produced in CHO cells, using a combination of high-performance liquid chromatography and electrospray-tandem mass spectrometry. With the use of electron transfer dissociation and collision induced dissociation (ETD and CID), we identified type, composition and structures of the Core 1 type O-linked glycans attached at the residues Thr 291, Thr 292 and Thr 576 of the full-length APP695. The glycosylations comprise multiple short glycans, containing N-acetyl galactosamine (GalNAc), Gal-GalNAc and sialic acid terminated structures. The presence of the glycopeptides in the tryptic mixture was identified using the CID-generated sugar oxonium ions. ETD proved to be valuable for the unambiguous identification of the modified sites as ETD fragmentation occurred along the peptide backbone with little or no cleavage of the glycans. Thus, the combination of the CID and ETD techniques in LC-MS is shown here, as a powerful tool for de novo identification of O-glycosylations at unknown modification sites in proteins.

    Funded by: Intramural NIH HHS: Z01 ES050171-08

    Journal of proteome research 2009;8;2;631-42

  • Novel polymorphisms of the amyloid precursor protein (APP) gene in Chinese/Taiwanese patients with Alzheimer's disease.

    Thajeb P, Wang P, Chien CL and Harrigan R

    Department of Neurology and Medical Research, Mackay Memorial Hospital, Taipei, Taiwan. peterus@hawaii.edu

    We aimed to determine if the amyloid precursor protein (APP) gene polymorphism is present in Chinese/Taiwanese patients with Alzheimer's disease (AD). This is a 3-year prospective assessment of the genotypes of the APP gene among Chinese/Taiwanese patients with AD. The sample consisted of 50 AD patients and 50 unaffected controls. Participants were recruited from the practices of the authors. Controls were comprised of 45 unrelated healthy subjects and 5 unaffected family members of AD patients. Data were collected in a university-based research unit of a tertiary medical center. Sequencing of the APP gene from exon 15 to exon 18 was performed on the peripheral blood of the patients and the unaffected controls after their informed consent was obtained. Among 50 AD subjects, 11 (7 men, 4 women) had APP gene polymorphisms. Mean age of onset was 72 years (range 65-82 years). Polymorphism of APP gene with A to C substitution at nucleotide position (nt) 284490 (A284490C) was found in 8 AD patients, at nt 284493 (A284493C) in 5, T284497C in 3 patients, and T284500C in 1 patient. These single nucleotide substitutions of the APP gene corresponded to the amino acid substitutions I718L, L720S, and V710G. These polymorphisms were not found in the unaffected controls. The mutations were confirmed by StyI restriction enzyme digestion assay using the subclone from polymerase chain reaction (PCR) products of the mutated APP gene. Thus, APP gene polymorphisms at codon 718 (I>L), 720 (L>S), and 710 (V>G) can be found in certain Chinese/Taiwanese patients with Alzheimer's disease.

    Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia 2009;16;2;259-63

  • O-Mannosylation is required for the solubilization of heterologously expressed human beta-amyloid precursor protein in Saccharomyces cerevisiae.

    Murakami-Sekimata A, Sato K, Sato K, Takashima A and Nakano A

    RIKEN Brain Science Institute, Wako, Saitama, Japan.

    In an attempt to express human beta-amyloid precursor protein (APP) in yeast, we fortuitously found that this protein is only O-glycosylated in yeast. APP was effectively expressed in yeast, processed by yeast alpha-secretases, members of the Yapsin family, to produce N-terminal (sAPPalpha) and C-terminal (CTFalpha) domains, when its signal sequence was replaced by that of the yeast alpha-mating factor. APP is known to acquire N- and O-glycosylation through the endoplasmic reticulum (ER) and the Golgi apparatus and is transported to the plasma membrane in mammalian cells. In spite of the presence of canonical N-glycosylation consensus sequences, APP was not N-glycosylated in the yeast system. Pulse-chase experiments demonstrated that APP received only O-mannosylation in yeast. Examination of yeast pmt mutants, which are defective in the initiation of O-mannosylation in the ER, revealed that Pmt4p is most responsible for the oligosaccharide modification of APP. Maturation of APP was slowed down and aggregated forms of APP were observed by sucrose density gradient fractionation of the Deltapmt4 mutant lysate. This caused decreased production of CTFalpha. We conclude that O-mannosylation is required for the solubilization of exogenously expressed human APP.

    Genes to cells : devoted to molecular & cellular mechanisms 2009;14;2;205-15

  • p120 catenin recruits cadherins to gamma-secretase and inhibits production of Abeta peptide.

    Kouchi Z, Barthet G, Serban G, Georgakopoulos A, Shioi J and Robakis NK

    Department of Psychiatry, Mount Sinai School of Medicine, New York, New York 10029, USA.

    The gamma-secretase complex cleaves many transmembrane proteins, including amyloid precursor protein, EphB and ErbB tyrosine kinase receptors, Notch1 receptors, and adhesion factors. Presenilin 1, the catalytic subunit of gamma-secretase, associates with the cadherin/catenin cell-cell adhesion/communication system and promotes cadherin processing (Georgakopoulos, A., et al. (1999) Mol. Cell 4, 893-902; Marambaud, P., et al. (2002) EMBO J. 21, 1948-1956), but the mechanism by which gamma-secretase and cadherins associate is unclear. Here we report that p120 catenin (p120ctn), a component of the cadherin-catenin complex, recruits gamma-secretase to cadherins, thus stimulating their processing while inhibiting production of Abeta peptide and the amyloid precursor protein intracellular domain. This function of p120ctn depends on both p120ctn-cadherin and p120ctn-presenilin 1 binding, indicating that p120ctn is the central factor that bridges gamma-secretase and cadherin-catenin complexes. Our data show that p120ctn is a unique positive regulator of the gamma-secretase processing of cadherins and a negative regulator of the amyloid precursor protein processing. Furthermore, our data suggest that specific members of the gamma-secretase complex may be used to recruit different substrates and that distinct PS1 sequences are required for processing of APP and cadherins.

    Funded by: NIA NIH HHS: AG-08200, AG-17926, R37 AG017926; NINDS NIH HHS: NS047229, R01 NS047229

    The Journal of biological chemistry 2009;284;4;1954-61

  • S-palmitoylation of gamma-secretase subunits nicastrin and APH-1.

    Cheng H, Vetrivel KS, Drisdel RC, Meckler X, Gong P, Leem JY, Li T, Carter M, Chen Y, Nguyen P, Iwatsubo T, Tomita T, Wong PC, Green WN, Kounnas MZ and Thinakaran G

    Department of Neurobiology, The University of Chicago, Chicago, Illinois 60637, USA.

    Proteolytic processing of amyloid precursor protein (APP) by beta- and gamma-secretases generates beta-amyloid (Abeta) peptides, which accumulate in the brains of individuals affected by Alzheimer disease. Detergent-resistant membrane microdomains (DRM) rich in cholesterol and sphingolipid, termed lipid rafts, have been implicated in Abeta production. Previously, we and others reported that the four integral subunits of the gamma-secretase associate with DRM. In this study we investigated the mechanisms underlying DRM association of gamma-secretase subunits. We report that in cultured cells and in brain the gamma-secretase subunits nicastrin and APH-1 undergo S-palmitoylation, the post-translational covalent attachment of the long chain fatty acid palmitate common in lipid raft-associated proteins. By mutagenesis we show that nicastrin is S-palmitoylated at Cys(689), and APH-1 is S-palmitoylated at Cys(182) and Cys(245). S-Palmitoylation-defective nicastrin and APH-1 form stable gamma-secretase complexes when expressed in knock-out fibroblasts lacking wild type subunits, suggesting that S-palmitoylation is not essential for gamma-secretase assembly. Nevertheless, fractionation studies show that S-palmitoylation contributes to DRM association of nicastrin and APH-1. Moreover, pulse-chase analyses reveal that S-palmitoylation is important for nascent polypeptide stability of both proteins. Co-expression of S-palmitoylation-deficient nicastrin and APH-1 in cultured cells neither affects Abeta40, Abeta42, and AICD production, nor intramembrane processing of Notch and N-cadherin. Our findings suggest that S-palmitoylation plays a role in stability and raft localization of nicastrin and APH-1, but does not directly modulate gamma-secretase processing of APP and other substrates.

    Funded by: NIA NIH HHS: AG019070, AG021495; NINDS NIH HHS: NS45150, P01 NS047308

    The Journal of biological chemistry 2009;284;3;1373-84

  • Neprilysin gene expression requires binding of the amyloid precursor protein intracellular domain to its promoter: implications for Alzheimer disease.

    Belyaev ND, Nalivaeva NN, Makova NZ and Turner AJ

    Faculty of Biological Sciences, Institute of Molecular and Cellular Biology, University of Leeds, Leeds, UK.

    Amyloid beta-peptide (Abeta) accumulation leads to neurodegeneration and Alzheimer disease; however, amyloid metabolism is a dynamic process and enzymic mechanisms exist for Abeta removal. Considerable controversy surrounds whether the intracellular domain of the amyloid precursor protein (AICD) regulates expression of the Abeta-degrading metalloprotease, neprilysin (NEP). By comparing two neuroblastoma cell lines differing substantially in NEP expression, we show by chromatin immunoprecipitation (ChIP) that AICD is bound directly to the NEP promoter in high NEP-expresser (NB7) cells but not in low-expresser (SH-SY5Y) cells. The methylation status of the NEP promoter does not regulate expression in these cells, whereas the histone deacetylase inhibitors trichostatin A and valproate partly restore NEP expression and activity in SH-SY5Y cells. ChIP analysis also reveals AICD binding to the NEP promoter in rat primary neurons but not in HUVEC cells. Chromatin remodelling of crucial Alzheimer disease-related genes by valproate could provide a new therapeutic strategy.

    Funded by: Medical Research Council: G0501565, G9824728

    EMBO reports 2009;10;1;94-100

  • Proteomic analysis reveals Hrs ubiquitin-interacting motif-mediated ubiquitin signaling in multiple cellular processes.

    Pridgeon JW, Webber EA, Sha D, Li L and Chin LS

    Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA.

    Despite the critical importance of protein ubiquitination in the regulation of diverse cellular processes, the molecular mechanisms by which cells recognize and transmit ubiquitin signals remain poorly understood. The endosomal sorting machinery component hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) contains a ubiquitin-interacting motif (UIM), which is believed to bind ubiquitinated membrane cargo proteins and mediate their sorting to the lysosomal degradation pathway. To gain insight into the role of Hrs UIM-mediated ubiquitin signaling in cells, we performed a proteomic screen for Hrs UIM-interacting ubiquitinated proteins in human brain by using an in vitro expression cloning screening approach. We have identified 48 ubiquitinated proteins that are specifically recognized by the UIM domain of Hrs. Among them, 12 are membrane proteins that are likely to be Hrs cargo proteins, and four are membrane protein-associated adaptor proteins whose ubiquitination may act as a signal to target their associated membrane cargo for Hrs-mediated endosomal sorting. Other classes of the identified proteins include components of the vesicular trafficking machinery, cell signaling molecules, proteins associated with the cytoskeleton and cytoskeleton-dependent transport, and enzymes involved in ubiquitination and metabolism, suggesting the involvement of Hrs UIM-mediated ubiquitin signaling in the regulation of multiple cellular processes. We have characterized the ubiquitination of two identified proteins, Munc18-1 and Hsc70, and their interaction with Hrs UIM, and provided functional evidence supporting a role for Hsc70 in the regulation of Hrs-mediated endosome-to-lysosome trafficking.

    Funded by: NIGMS NIH HHS: GM082828, R01 GM082828, R01 GM082828-01A1, R01 GM082828-02, R01 GM082828-02S1; NINDS NIH HHS: NS047575, NS050650, R01 NS047575, R01 NS047575-01, R01 NS047575-02, R01 NS047575-03, R01 NS047575-04, R01 NS050650, R01 NS050650-01A1, R01 NS050650-02, R01 NS050650-03, R01 NS050650-04, T32 NS007480, T32 NS007480-05, T32 NS007480-06, T32 NS007480-07, T32 NS007480-08, T32 NS007480-09, T32NS007480

    The FEBS journal 2009;276;1;118-31

  • [Studying pathogenesis of Alzheimer's disease in a Drosophila melanogaster model: human APP overexpression in the brain of transgenic flies leads to deficit of the synaptic protein synaptotagmin].

    Sarantseva SV, Bol'shakova OI, Timoshenko SI, Rodin DI, Vitek MP and Shvartsman AL

    Alzheimer's disease (AD) is a progressive neurodegenerative disease whose main pathomorphological sign is synapse degeneration in the cortex and hippocampus. Abnormal synaptogenesis precedes amyloidosis and neurodegeneration and correlates with memory impairment during the early clinical phase. Mutations in the amyloid precursor protein (APP) gene cause familial AD and enhance the secretion of amyloid-beta-protein (Abeta). However, it remains unclear in what way APP and Abeta are involved in synaptic disorder in the absence of visible amyloid structures. In this study, the role of the human APP gene in synaptogenesis in transgenic lines of Drosophila melanogaster whose nerve cells express the human APP695 isoform, truncated APPs, and the presynaptic marker synaptotagmin driving the sequence of the green fluorescent protein. The expression of APP and its truncated forms caused a decrease in the synaptotagmin content of antennal lobes and mushroom lobes of the D. melanogaster brain, as well as neurodegeneration that progressed with age. The results suggest that that abnormal synaptogenesis and neurodegeneration occur in the Drosophila brain in the absence of Abeta. It is assumed that impaired cellular functions of APP and secretion of Abeta independently contribute to the pathogenesis of AD.

    Genetika 2009;45;1;119-26

  • AbetaPP A713T mutation in late onset Alzheimer's disease with cerebrovascular lesions.

    Bernardi L, Geracitano S, Colao R, Puccio G, Gallo M, Anfossi M, Frangipane F, Curcio SA, Mirabelli M, Tomaino C, Vasso F, Smirne N, Maletta R and Bruni AC

    Regional Neurogenetic Centre, ASP Catanzaro, Lamezia Terme (CZ), Italy.

    Mutations in the amyloid-beta protein precursor (AbetaPP) gene can cause autosomal dominant early-onset Alzheimer's disease, or Alzheimer's disease (AD) associated with cerebral amyloid angiopathy (CAA), cerebral hemorrhage, or both. We have previously reported that the AbetaPP A713T mutation is associated with AD and subcortical ischemic lesions at magnetic resonance imaging in a large family which neuropathology confirmed CAA, stroke, and AD lesions. The objective of this clinical and molecular study was to investigate AbetaPP gene mutations in 59 patients affected by AD with cerebrovascular lesions (CVLs) and a family history of dementia. We identified three affected subjects with the AbetaPP A713T mutation. Since the prevalence of this mutation worldwide is very low, a common founder could exist in southern Italy. The pathogenicity of this mutation was confirmed and the clinical AD phenotype with CVLs seems to be a distinctive feature in the southern Italian population. The identification of these patients suggests that genetic epidemiology in large cohorts of familial late onset AD with CVLs would increase the probability of identifying AbetaPP mutations.

    Journal of Alzheimer's disease : JAD 2009;17;2;383-9

  • Amyloid-beta colocalizes with apolipoprotein B in absorptive cells of the small intestine.

    Galloway S, Takechi R, Pallebage-Gamarallage MM, Dhaliwal SS and Mamo JC

    The Australian Technology Network Centre for Metabolic Fitness, School of Public Health, Curtin Health Innovation Research Institute, Curtin University of Technology, Perth, Western Australia, Australia. susan.galloway@postgrad.curtin.edu.au

    Background: Amyloid-beta is recognized as the major constituent of senile plaque found in subjects with Alzheimer's disease. However, there is increasing evidence that in a physiological context amyloid-beta may serve as regulating apolipoprotein, primarily of the triglyceride enriched lipoproteins. To consider this hypothesis further, this study utilized an in vivo immunological approach to explore in lipogenic tissue whether amyloid-beta colocalizes with nascent triglyceride-rich lipoproteins.

    Results: In murine absorptive epithelial cells of the small intestine, amyloid-beta had remarkable colocalization with chylomicrons (Manders overlap coefficient = 0.73 +/- 0.03 (SEM)), the latter identified as immunoreactive apolipoprotein B. A diet enriched in saturated fats doubled the abundance of both amyloid-beta and apo B and increased the overlap coefficient of the two proteins (0.87 +/- 0.02). However, there was no evidence that abundance of the two proteins was interdependent within the enterocytes (Pearson's Coefficient < 0.02 +/- 0.03), or in plasma (Pearson's Coefficient < 0.01).

    Conclusion: The findings of this study are consistent with the possibility that amyloid-beta is secreted by enterocytes as an apolipoprotein component of chylomicrons. However, secretion of amyloid-beta appears to be independent of chylomicron biogenesis.

    Lipids in health and disease 2009;8;46

  • CD74 interacts with APP and suppresses the production of Abeta.

    Matsuda S, Matsuda Y and D'Adamio L

    Albert Einstein College of Medicine, Department of Microbiology & Immunology, 1300 Morris Park Avenue, Bronx, NY 10461, USA. ldadamio@aecom.yu.edu.

    Background: Alzheimer disease (AD) is characterized by senile plaques, which are mainly composed of beta amyloid (Abeta) peptides. Abeta is cleaved off from amyloid precursor protein (APP) with consecutive proteolytic processing by beta-secretase and gamma-secretase.

    Results: Here, we show that CD74, the invariant chain of class II major histocompatibility complex, interacts with APP and serves as a negative regulator of Abeta. CD74 resembles other APP interacters such as BRI2 and BRI3, since all of them reduce the level of Abeta. However, unlike BRIs, CD74 does not reduce the secretion of sAPPalpha or sAPPbeta. Interestingly, in HeLa cells, over expression of CD74 steers APP, but not Notch, to large vacuoles created by CD74.

    Conclusion: Taken together, we propose that CD74 inhibits Abeta production by interacting with and derailing normal trafficking of APP.

    Molecular neurodegeneration 2009;4;41

  • Cerebral amyloid angiopathy: a common cause of cerebral hemorrhage.

    Pezzini A, Del Zotto E, Volonghi I, Giossi A, Costa P and Padovani A

    Department of Medical and Surgical Sciences, Neurology Clinic, University of Brescia, Brescia, Italy. ale_pezzini@hotmail.com

    Amyloid is a term used to describe protein deposits with circumscript physical characteristics: beta-pleated sheet configuration, apple green birefringence under polarized light after Congo red staining, fibrillary structure and high insolubility. Cerebral amyloid angiopathy (CAA) defines a clinicopathological phenomenon characterized by amyloid deposition in the walls of leptomeningeal and cortical arteries, arterioles, and, less often capillaries and veins of the central nervous system. CAAs are currently classified according to the protein deposited including amyloid beta peptide (Abeta), cystatin C (ACys C), prion protein (PrP(Sc)), ABri/ADan, transthyretin (ATTR), and gelsolin (AGel). Most often amyloid deposition occurs in sporadic forms. In less common hereditary forms, a mutated variant protein or precursor protein is abnormally metabolized by proteolytic pathways in consequence of specific gene mutations, and accumulates as amyloid. The spectrum of clinical phenotypes associated with CAA-related vasculopathic changes includes both ischemic and hemorrhagic presentations, primary intracerebral hemorrhage (PICH) being probably the most well-recognized. However, in spite of accumulating data and recent progress in understanding the pathogenesis of CAA-related hemorrhage, the exact mechanisms leading to vessel rupture in these cases are yet to be established. This represents, at present, a major limitation to the identification of reliable biomarkers and the development of disease-specific treatment options. The present paper summarizes epidemiologic and clinical aspects of CAA, and highlights the presumed pathomechanisms of amyloid deposition in both sporadic and hereditary forms.

    Current medicinal chemistry 2009;16;20;2498-513

  • Deprotonation of the Asp1-Ala2 peptide bond induces modification of the dynamic copper(II) environment in the amyloid-beta peptide near physiological pH.

    Hureau C, Coppel Y, Dorlet P, Solari PL, Sayen S, Guillon E, Sabater L and Faller P

    CNRS; LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, 31077 Toulouse, France. christelle.hureau@lcc-toulouse.fr

    Angewandte Chemie (International ed. in English) 2009;48;50;9522-5

  • MPEP reduces seizure severity in Fmr-1 KO mice over expressing human Abeta.

    Westmark CJ, Westmark PR and Malter JS

    Department of Pathology & Laboratory Medicine and Waisman Center for Developmental Disabilities, University of Wisconsin, Madison, WI 53705, USA. westmark@wisc.edu

    Metabotropic glutamate receptor 5 (mGluR(5)) regulates the translation of amyloid precursor protein (APP) mRNA. Under resting conditions, mRNA is bound to and translationally repressed by the fragile X mental retardation protein (FMRP). Upon group 1 mGluR activation, FMRP dissociates from the mRNA and translation ensues. APP levels are elevated in the dendrites of primary neuronal cultures as well as in synaptoneurosomes (SN) prepared from embryonic and juvenile fmr-1 knockout (KO) mice, respectively. In order to study the effects of APP and its proteolytic product Abeta on Fragile X syndrome (FXS) phenotypes, we created a novel mouse model (FRAXAD) that over-expresses human APPSwe/Abeta in an fmr-1 KO background. Herein, we assess (1) human APP(Swe) and Abeta levels as a function of age in FRAXAD mice, and (2) seizure susceptibility to pentylenetetrazol (PTZ) after mGluR(5) blockade. PTZ-induced seizure severity is decreased in FRAXAD mice pre-treated with the mGluR(5) antagonist MPEP. These data suggest that Abeta contributes to seizure incidence and may be an appropriate therapeutic target to lessen seizure pathology in FXS, Alzheimer's disease (AD) and Down syndrome (DS) patients.

    Funded by: NIA NIH HHS: R01 AG10675; NICHD NIH HHS: P30 HD03352; NIDA NIH HHS: DA026067

    International journal of clinical and experimental pathology 2009;3;1;56-68

  • Novel T719P AbetaPP mutation unbalances the relative proportion of amyloid-beta peptides.

    Ghidoni R, Albertini V, Squitti R, Paterlini A, Bruno A, Bernardini S, Cassetta E, Rossini PM, Squitieri F, Benussi L and Binetti G

    Proteomics Unit, IRCCS Centro S. Giovanni di Dio-FBF, Brescia, Italy. rghidoni@fatebenefratelli.it

    A novel missense mutation (T719P) in the amyloid-beta protein precursor (AbetaPP) gene was discovered in a 46-year old patient affected by early onset familial Alzheimer's disease. Using surface enhanced laser desorption/ionization mass spectrometry (SELDI-TOF MS), we determined mass profiles of amyloid-beta peptides (Abeta) in cerebrospinal fluid (CSF) of the AbetaPP mutated patient, healthy control subjects (n = 10), and of two subjects carrying mutations in presenilins genes (PS) (i.e., PS1 P117L and PS2 T122R): seven different C-terminally and three N-terminally truncated Abeta peptides were found in CSF. The investigated AbetaPP as well as PS mutations were associated with an overall reduction of Abeta species, except for Abeta(10-40). Interestingly, the AbetaPP T719P mutation unbalanced the relative proportion of Abeta peptides with a reduction of Abeta(1-40) and Abeta(1-42) paralleled by an increase of Abeta(1-38) and Abeta(10-40). Despite the specific neuropeptidomic phenotype associated with the AbetaPP T719P mutation, the enrichment in Abeta(10-40) paralleled by depletion of Abeta(1-42) seems to be a common theme in familial AD. The AbetaPP T719P mutation is of particular interest because it is the only mutation located in close proximity to the AbetaPP epsilon-cleavage site.

    Journal of Alzheimer's disease : JAD 2009;18;2;295-303

  • Oligomerization partially explains the lowering of Abeta42 in Alzheimer's disease cerebrospinal fluid.

    Englund H, Degerman Gunnarsson M, Brundin RM, Hedlund M, Kilander L, Lannfelt L and Pettersson FE

    Department of Public Health and Caring Sciences/Molecular Geriatrics, Rudbeck Laboratory Uppsala University, Uppsala, Sweden.

    The lowering of natively analyzed Abeta42 in cerebrospinal fluid (CSF) is used as a diagnostic tool in Alzheimer's disease (AD). The presence of Abeta oligomers can interfere with such analyses causing underestimation of Abeta levels due to epitope masking. The aim was to investigate if the lowering of CSF Abeta42 seen in AD is caused by oligomerization.

    Methods: Abeta42 was analyzed under both denaturing and non-denaturing conditions. An Abeta42 oligomer ratio was calculated from these quantifications. The presence of oligomers leads to Abeta42 epitope masking during non-denaturing assays, resulting in a higher ratio.

    Results: The Abeta42 oligomer ratio was used for the assessment of oligomerized Abeta in human CSF, after being evaluated in transgenic mouse brain homogenates. AD and mild cognitive impairment (MCI) samples displayed the expected decrease in natively measured Abeta42 compared to healthy controls and frontotemporal dementia, but not when analyzing under denaturing conditions. Accordingly, AD and MCI CSF had a higher Abeta42 oligomer ratio in CSF.

    Conclusion: Combining denaturing and non-denaturing quantifications of Abeta42 into an oligomer ratio enables the assessment of Abeta oligomers in biological samples. The increased Abeta42 oligomer ratio for AD and MCI indicates the presence of oligomers in CSF and that the lowering of natively measured Abeta42 is caused by oligomerization.

    Neuro-degenerative diseases 2009;6;4;139-47

  • Plasma amyloid-beta peptide levels correlate with adipocyte amyloid precursor protein gene expression in obese individuals.

    Lee YH, Martin JM, Maple RL, Tharp WG and Pratley RE

    Diabetes and Metabolism Translational Medicine Unit, University of Vermont College of Medicine, Burlington, Vt., USA. ylee325@cu.ac.kr

    Several studies have demonstrated that midlife obesity increases the risk for dementia and Alzheimer's disease. Moreover, plasma 42-amino-acid amyloid-beta (Abeta42) levels appear to correlate with BMI. We recently demonstrated that adipocyte amyloid precursor protein (APP) expression is upregulated in obesity and correlates with insulin resistance and adipose tissue inflammation. In this study, we aimed to investigate the relation between adipocyte APP expression and plasma Abeta peptide levels.

    Methods: We conducted a pilot study in which we measured adipocyte APP gene expression and the circulating plasma levels of Abeta40 in 10 obese individuals before and after a 6-month behaviorally based weight loss intervention. Subjects had an oral glucose tolerance test with measurement of insulin levels, Abeta40 levels measured by ELISA and transcript levels of APP in subcutaneous abdominal adipocytes measured by quantitative real-time PCR.

    Results: At baseline, adipocyte APP expression correlated significantly with plasma Abeta40 levels and with 2-hour insulin concentrations. Following the 6-month weight loss intervention, body weight and BMI decreased significantly. Fasting plasma concentrations of glucose and insulin were improved. Adipocyte APP expression was significantly decreased (p < 0.001) after weight loss. Changes in adipocyte APP expression correlated with changes in plasma Abeta40 levels (R = 0.74, p = 0.01) and changes in 2-hour insulin (R = 0.75, p = 0.01).

    Conclusion: The results of this pilot study suggest that increased circulating plasma levels of Abeta peptides in obesity may be due to increased adipocyte APP gene expression. While these results suggest a possible mechanism linking midlife obesity with the later development of Alzheimer's disease, further research is necessary to elucidate the regulation and functional significance of APP in adipocytes.

    Neuroendocrinology 2009;90;4;383-90

  • Exceptional amyloid beta peptide hydrolyzing activity of nonphysiological immunoglobulin variable domain scaffolds.

    Taguchi H, Planque S, Sapparapu G, Boivin S, Hara M, Nishiyama Y and Paul S

    Chemical Immunology Research Center, Department of Pathology and Laboratory Medicine, University of Texas Houston Medical School, Houston, Texas 77030, USA.

    Nucleophilic sites in the paired variable domains of the light and heavy chains (VL and VH domains) of Ig can catalyze peptide bond hydrolysis. Amyloid beta (Abeta)-binding Igs are under consideration for immunotherapy of Alzheimer disease. We searched for Abeta-hydrolyzing human IgV domains (IgVs) in a library containing a majority of single chain Fv clones mimicking physiological VL-VH-combining sites and minority IgV populations with nonphysiological structures generated by cloning errors. Random screening and covalent selection of phage-displayed IgVs with an electrophilic Abeta analog identified rare IgVs that hydrolyzed Abeta mainly at His14-Gln15. Inhibition of IgV catalysis and irreversible binding by an electrophilic hapten suggested a nucleophilic catalytic mechanism. Structural analysis indicated that the catalytic IgVs are nonphysiological structures, a two domain heterodimeric VL (IgVL2-t) and single domain VL clones with aberrant polypeptide tags (IgVL-t'). The IgVs hydrolyzed Abeta at rates superior to naturally occurring Igs by 3-4 orders of magnitude. Forced pairing of the single domain VL with VH or VL domains resulted in reduced Abeta hydrolysis, suggesting catalysis by the unpaired VL domain.Angstrom level amino acid displacements evident in molecular models of the two domain and unpaired VL domain clones explain alterations of catalytic activity. In view of their superior catalytic activity, the VL domain IgVs may help attain clearance of medically important antigens more efficiently than natural Igs.

    Funded by: NIA NIH HHS: R01AG025304

    The Journal of biological chemistry 2008;283;52;36724-33

  • The binding of thioflavin T and its neutral analog BTA-1 to protofibrils of the Alzheimer's disease Abeta(16-22) peptide probed by molecular dynamics simulations.

    Wu C, Wang Z, Lei H, Duan Y, Bowers MT and Shea JE

    Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA.

    Thioflavin T (ThT) is a fluorescent dye commonly used to stain amyloid plaques, but the binding sites of this dye onto fibrils are poorly characterized. We present molecular dynamics simulations of the binding of ThT and its neutral analog BTA-1 [2-(4'-methylaminophenyl)benzothiazole] to model protofibrils of the Alzheimer's disease Abeta(16-22) (amyloid beta) peptide. Our simulations reveal two binding modes located at the grooves of the beta-sheet surfaces and at the ends of the beta-sheet. These simulations provide new insight into recent experimental work and allow us to characterize the high-capacity, micromolar-affinity site seen in experiment as binding to the beta-sheet surface grooves and the low-capacity, nanomolar-affinity site seen as binding to the beta-sheet extremities of the fibril. The structure-activity relationship upon mutating charged ThT to neutral BTA-1 in terms of increased lipophilicity and binding affinity was studied, with calculated solvation free energies and binding energies found to be in qualitative agreement with the experimental measurements.

    Funded by: NIA NIH HHS: AG027818, P01 AG027818, P01 AG027818-01, P01 AG027818-010001, P01 AG027818-019001, P01 AG027818-02, P01 AG027818-020001, P01 AG027818-029001, P01 AG027818-03, P01 AG027818-030001, P01 AG027818-039001

    Journal of molecular biology 2008;384;3;718-29

  • The low density lipoprotein receptor-related protein 1 mediates uptake of amyloid beta peptides in an in vitro model of the blood-brain barrier cells.

    Yamada K, Hashimoto T, Yabuki C, Nagae Y, Tachikawa M, Strickland DK, Liu Q, Bu G, Basak JM, Holtzman DM, Ohtsuki S, Terasaki T and Iwatsubo T

    Department of Neuropathology and Neuroscience, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan.

    The metabolism of amyloid beta peptide (A beta) in the brain is crucial to the pathogenesis of Alzheimer disease. A body of evidence suggests that A beta is actively transported from brain parenchyma to blood across the blood-brain barrier (BBB), although the precise mechanism remains unclear. To unravel the cellular and molecular mechanism of A beta transport across the BBB, we established a new in vitro model of the initial internalization step of A beta transport using TR-BBB cells, a conditionally immortalized endothelial cell line from rat brain. We show that TR-BBB cells rapidly internalize A beta through a receptor-mediated mechanism. We also provide evidence that A beta internalization is mediated by LRP1 (low density lipoprotein receptor-related protein 1), since administration of LRP1 antagonist, receptor-associated protein, neutralizing antibody, or small interference RNAs all reduced A beta uptake. Despite the requirement of LRP1-dependent internalization, A beta does not directly bind to LRP1 in an in vitro binding assay. Unlike TR-BBB cells, mouse embryonic fibroblasts endogenously expressing functional LRP1 and exhibiting the authentic LRP1-mediated endocytosis (e.g. of tissue plasminogen activator) did not show rapid A beta uptake. Based on these data, we propose that the rapid LRP1-dependent internalization of A beta occurs under the BBB-specific cellular context and that TR-BBB is a useful tool for analyzing the molecular mechanism of the rapid transport of A beta across BBB.

    Funded by: NIA NIH HHS: AG13956, R01 AG027924

    The Journal of biological chemistry 2008;283;50;34554-62

  • Dexras1 interacts with FE65 to regulate FE65-amyloid precursor protein-dependent transcription.

    Lau KF, Chan WM, Perkinton MS, Tudor EL, Chang RC, Chan HY, McLoughlin DM and Miller CC

    Department of Biochemistry and Molecular Biotechnology Programme, Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR. kflau@cuhk.edu.hk

    FE65 is an adaptor protein that binds to and forms a transcriptionally active complex with the gamma-secretase-derived amyloid precursor protein (APP) intracellular domain. The regulatory mechanisms of FE65-APP-mediated transcription are still not clear. In this report, we demonstrate that Dexras1, a Ras family small G protein, binds to FE65 PTB2 domain and potently suppresses the FE65-APP-mediated transcription. The suppression is not via competition for binding of FE65 between Dexras1 and APP because the two proteins can simultaneously bind to the FE65 PTB2 domain. Phosphorylation of FE65 tyrosine 547 within the PTB2 domain has been shown to enhance FE65-APP-mediated transcription but not to influence binding to APP. Here we find that this phosphorylation event reduces the binding between Dexras1 and FE65. We also demonstrate that Dexras1 inhibits the FE65-APP-mediated transcription of glycogen synthase kinase 3beta (GSK3 beta). Moreover, small interfering RNA knockdown of Dexras1 enhances GSK3 beta expression and increases phosphorylation of Tau, a GSK3 beta substrate. Thus, Dexras1 functions as a suppressor of FE65-APP-mediated transcription, and FE65 tyrosine 547 phosphorylation enhances FE65-APP-mediated transcription, at least in part, by modulating the interaction between FE65 and Dexras1. These findings reveal a novel regulatory mechanism for FE65-APP-mediated signaling.

    Funded by: Biotechnology and Biological Sciences Research Council: BB/C506913/1; Medical Research Council: G0000749, G0501573; Wellcome Trust

    The Journal of biological chemistry 2008;283;50;34728-37

  • Phosphorylation of amyloid precursor protein (APP) at Tyr687 regulates APP processing by alpha- and gamma-secretase.

    Takahashi K, Niidome T, Akaike A, Kihara T and Sugimoto H

    Department of Neuroscience for Drug Discovery, Graduate School of Pharmaceutical Sciences, Yoshida-Shimoadachi-cho, Sakyo-ku, Kyoto University, Kyoto 606-8501, Japan.

    Abnormal proteolytic processing of amyloid precursor protein (APP) is a pathologic feature of Alzheimer's disease. Recent studies have demonstrated that serine/threonine phosphorylation specifically at amino-acid residue Thr668 (APP695 numbering) regulates APP processing. In this study, we investigated the possibility that tyrosine phosphorylation of APP regulates APP processing. A tyrosine kinase inhibitor decreased expression of the C83 fragment which is a cleaved product of APP by alpha-secretase. By overexpressing APP mutant proteins, Tyr687 was found to be the major tyrosine kinase phosphorylation site. Expression of the C83 fragment was decreased in APPY687A-expressing cells relative to APP wild-type (APPWT)-expressing cells, which likely reflects the different cellular localization patterns of these two proteins. Expression of APP intracellular domain (AICD) which is a cleaved product of the C83 fragment by gamma-secretase was decreased in C83Y687A-expressing cells. These results suggest that phosphorylation of APP at Tyr687 regulates APP processing by alpha- and gamma-secretases, determining the expression level of AICD.

    Biochemical and biophysical research communications 2008;377;2;544-549

  • Reduced brain volumes in mice expressing APP-Austrian mutation but not in mice expressing APP-Swedish-Austrian mutations.

    Van Broeck B, Vanhoutte G, Cuijt I, Pereson S, Joris G, Timmermans JP, Van der Linden A, Van Broeckhoven C and Kumar-Singh S

    Neurodegenerative Brain Diseases Group, Department of Molecular Genetics, VIB, Antwerpen, Belgium.

    We previously described two transgenic mouse lines expressing sub-endogenous levels of the 'Austrian' APP-T714I mutation (driven by the prenatally active PDGF-beta promoter; APP-Au mice) and showing intraneuronal Abeta pathology and reduced brain volumes on MRI at 12 and 20 months of age. To further investigate whether reduced brain sizes were caused by neurodegeneration or a neurodevelopmental defect, we now measured brain volumes as early as postnatal day 10. At this age, a distinguishable reduction in brain volumes was absent, indicating that brain volume deficits in APP-Au mice are not caused by a neurodevelopmental defect. To further study the association between intraneuronal Abeta and reduced brain volumes, we further generated and analyzed an APP transgenic mouse model expressing both Austrian and Swedish (K670N/M671L) mutations (APP-SwAu mice). APP-Swedish mutation is known to lead to altered APP processing in the secretory pathway, precluding its later processing in endosomal-lysosomal compartments, the site of intraneuronal Abeta accumulation. Also, to have higher levels of transgene expression only after birth, a murine Thy-1 promoter was utilized for APP-SwAu mouse lines. Despite having five times higher transgene APP levels compared to APP-Au mice, APP-SwAu mice showed significantly lower intraneuronal Abeta levels in the absence of reduced brain volumes, suggesting that intraneuronal Abeta accumulation is related to reduced brain volumes in APP-Au mice. These data also provide a first in vivo indication of altered processing of APP-Swedish at sub-endogenous levels, an effect not observed in mouse models expressing the APP-Swedish mutation in high amounts.

    Neuroscience letters 2008;447;2-3;143-7

  • Amyloid-beta overproduction causes abnormal mitochondrial dynamics via differential modulation of mitochondrial fission/fusion proteins.

    Wang X, Su B, Siedlak SL, Moreira PI, Fujioka H, Wang Y, Casadesus G and Zhu X

    Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA.

    Mitochondrial dysfunction is a prominent feature of Alzheimer disease but the underlying mechanism is unclear. In this study, we investigated the effect of amyloid precursor protein (APP) and amyloid beta on mitochondrial dynamics in neurons. Confocal and electron microscopic analysis demonstrated that approximately 40% M17 cells overexpressing WT APP (APPwt M17 cells) and more than 80% M17 cells overexpressing APPswe mutant (APPswe M17 cells) displayed alterations in mitochondrial morphology and distribution. Specifically, mitochondria exhibited a fragmented structure and an abnormal distribution accumulating around the perinuclear area. These mitochondrial changes were abolished by treatment with beta-site APP-cleaving enzyme inhibitor IV. From a functional perspective, APP overexpression affected mitochondria at multiple levels, including elevating reactive oxygen species levels, decreasing mitochondrial membrane potential, and reducing ATP production, and also caused neuronal dysfunction such as differentiation deficiency upon retinoic acid treatment. At the molecular level, levels of dynamin-like protein 1 and OPA1 were significantly decreased whereas levels of Fis1 were significantly increased in APPwt and APPswe M17 cells. Notably, overexpression of dynamin-like protein 1 in these cells rescued the abnormal mitochondrial distribution and differentiation deficiency, but failed to rescue mitochondrial fragmentation and functional parameters, whereas overexpression of OPA1 rescued mitochondrial fragmentation and functional parameters, but failed to restore normal mitochondrial distribution. Overexpression of APP or Abeta-derived diffusible ligand treatment also led to mitochondrial fragmentation and reduced mitochondrial coverage in neuronal processes in differentiated primary hippocampal neurons. Based on these data, we concluded that APP, through amyloid beta production, causes an imbalance of mitochondrial fission/fusion that results in mitochondrial fragmentation and abnormal distribution, which contributes to mitochondrial and neuronal dysfunction.

    Funded by: NIA NIH HHS: AG031852

    Proceedings of the National Academy of Sciences of the United States of America 2008;105;49;19318-23

  • The effects of NOS2 gene deletion on mice expressing mutated human AbetaPP.

    Colton CA, Wilcock DM, Wink DA, Davis J, Van Nostrand WE and Vitek MP

    Division of Neurology, Duke University Medical Center, Durham, NC 27710, USA. glia01@aol.com

    Nitric oxide synthase 2 (NOS2) and its gene product, inducible NOS (iNOS) play an important role in neuroinflammation by generating nitric oxide (NO), a critical signaling and redox factor in the brain. Although NO is associated with tissue damage, it can also promote cell survival. We hypothesize that during long-term exposure to amyloid-beta (Abeta) in Alzheimer's disease (AD), NO levels fall in the brain to a threshold at which the protective effects of NO cannot be sustained, promoting Abeta mediated damage. Two new mouse models of AD have been developed that utilize this concept of NO's action. These mice express human amyloid-beta protein precursor (AbetaPP) mutations that generate Abeta peptides on a mouse NOS2 knockout background. The APP/NOS2(-/-) bigenic mice progress from Abeta production and amyloid deposition to hyperphosphorylated normal mouse tau at AD-associated epitopes, aggregation and redistribution of tau to somatodendritic regions of neurons and significant neuronal loss including loss of interneurons. This AD-like pathology is accompanied by robust behavioral changes. As APP/NOS2(-/-) bigenic mice more fully model the human AD disease pathology, they may serve as a tool to better understand disease progression in AD and the role of NO in altering chronic neurological disease processes.

    Funded by: NIA NIH HHS: AG030942, AG19740, AG19780, F32 AG030942, F32 AG030942-02, P30 AG028377, R01 AG019740-04, R01 AG019780, R01 AG019780-05

    Journal of Alzheimer's disease : JAD 2008;15;4;571-87

  • C-terminal 37 residues of LRP promote the amyloidogenic processing of APP independent of FE65.

    Lakshmana MK, Chen E, Yoon IS and Kang DE

    Department of Neurosciences, University of California, San Diego, Gilman Drive, La Jolla, CA 92093, USA.

    The major defining pathological hallmark of Alzheimer's disease (AD) is the accumulation of amyloid beta protein (Abeta), a small peptide derived from beta- and gamma-secretase cleavages of the amyloid precursor protein (APP). Recent studies have shown that the Low-density lipoprotein receptor-related protein (LRP) plays a pivotal role in the trafficking of APP and generation of Abeta. In particular, we recently showed that the soluble cytoplasmic tail of LRP (LRP-ST) without a membrane tether was sufficient to promote Abeta generation. In this study, we demonstrate that the last 37 residues of LRP cytoplasmic tail (LRP-C37) lacking the NPxY motifs and FE65 binding mediate the core pro-amyloidogenic activity of LRP-ST. Moreover, we show that the conserved dileucine motif within the LRP-C37 region is a key determinant of its Abeta promoting activity. Finally, results from a yeast two-hybrid screen using LRP-C37 region as bait reveal four new LRP-binding proteins implicated in intracellular signalling and membrane protein trafficking. Our findings indicate that the LRP-C37 sequence represents a new protein-binding domain that may be useful as a therapeutic target and tool to lower Abeta generation in AD.

    Funded by: NIA NIH HHS: AG 005131-24S1, P50 AG005131, P50 AG005131-26

    Journal of cellular and molecular medicine 2008;12;6B;2665-74

  • Enduring involvement of tau, beta-amyloid, alpha-synuclein, ubiquitin and TDP-43 pathology in the amyotrophic lateral sclerosis/parkinsonism-dementia complex of Guam (ALS/PDC).

    Miklossy J, Steele JC, Yu S, McCall S, Sandberg G, McGeer EG and McGeer PL

    Kinsmen Laboratory of Neurological Research, The University of British Columbia, 2255 Wesbrook Mall, Vancouver, BC, V6T 1Z3, Canada.

    Guam ALS/PDC is a severe tangle forming disorder endemic to Guam with features overlapping such neurodegenerative disorders as Alzheimer disease (AD), Parkinson disease (PD), progressive supranuclear palsy (PSP), ALS, corticobasal degeneration (CBD) and pallido-ponto-nigral degeneration (PPND). Since the prevalence is declining, we examined brain tissue from 35 clinically diagnosed Chamorro patients with ALS/PDC and two Chamorro controls autopsied between 1946 and 2006, to determine if distinct variations in the pathology could be identified up to this time. Although the age at autopsy increased by 4.5-5 years per decade, we identified no qualitative differences in pathological deposits with antibodies against tau, ubiquitin, A beta, alpha-synuclein and TDP-43, indicating that these more recently identified proteins have been involved in the neuropathogenesis over the past 6 decades. Tau and TDP-43 positive neuronal, oligodendroglial and astrocytic inclusions involving multiple nerve fiber tracts occurred in both the ALS and PDC types, reinforcing the concept that these forms are part of the same disorder. The results obtained may help to define the commonality of the Guam disease with other tangle forming disorders and may help in monitoring the epidemiological changes that are taking place.

    Acta neuropathologica 2008;116;6;625-37

  • Oxidative stress, telomere length and biomarkers of physical aging in a cohort aged 79 years from the 1932 Scottish Mental Survey.

    Starr JM, Shiels PG, Harris SE, Pattie A, Pearce MS, Relton CL and Deary IJ

    MRC Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Royal Victoria Hospital, Edinburgh EH4 2DN, UK. jstarr@staffmail.ed.ac.uk

    Telomere shortening is a biomarker of cellular senescence and is associated with a wide range of age-related disease. Oxidative stress is also associated with physiological aging and several age-related diseases. Non-human studies suggest that variants in oxidative stress genes may contribute to both telomere shortening and biological aging. We sought to test whether oxidative stress-related gene polymorphisms contribute to variance in both telomere length and physical biomarkers of aging in humans. Telomere lengths were calculated for 190 (82 men, 108 women) participants aged 79 years and associations with 384 SNPs, from 141 oxidative stress genes, identified 9 significant SNPS, of which those from 5 genes (GSTZ1, MSRA, NDUFA3, NDUFA8, VIM) had robust associations with physical aging biomarkers, respiratory function or grip strength. Replication of associations in a sample of 318 (120 males, 198 females) participants aged 50 years confirmed significant associations for two of the five SNPs (MSRA rs4841322, p=0.008; NDUFA8 rs6822, p=0.048) on telomere length. These data indicate that oxidative stress genes may be involved in pathways that lead to both telomere shortening and physiological aging in humans. Oxidative stress may explain, at least in part, associations between telomere shortening and physiological aging.

    Funded by: Biotechnology and Biological Sciences Research Council: S18386; Chief Scientist Office: CZB/4/505, ETM/55; Medical Research Council; Wellcome Trust

    Mechanisms of ageing and development 2008;129;12;745-51

  • Selective induction of calcineurin activity and signaling by oligomeric amyloid beta.

    Reese LC, Zhang W, Dineley KT, Kayed R and Taglialatela G

    Department of Neuroscience and Cell Biology, University of Texas Medical Branch at Galveston, Texas, USA.

    Alzheimer's disease (AD) is a terminal age-associated dementia characterized by early synaptic dysfunction and late neurodegeneration. Although the presence of plaques of fibrillar aggregates of the amyloid beta peptide (Abeta) is a signature of AD, evidence suggests that the preplaque small oligomeric Abeta promotes both synaptic dysfunction and neuronal death. We found that young Tg2576 transgenic mice, which accumulate Abeta and develop cognitive impairments prior to plaque deposition, have high central nervous system (CNS) activity of calcineurin (CaN), a phosphatase involved in negative regulation of memory function via inactivation of the transcription factor cAMP responsive element binding proteins (CREB), and display CaN-dependent memory deficits. These results thus suggested the involvement of prefibrillary forms of Abeta. To investigate this issue, we compared the effect of monomeric, oligomeric, and fibrillar Abeta on CaN activity, CaN-dependent pCREB and phosphorylated Bcl-2 Associated death Protein (pBAD) levels, and cell death in SY5Y cells and in rat brain slices, and determined the role of CaN on CREB phosphorylation in the CNS of Tg2576 mice. Our results show that oligomeric Abeta specifically induces CaN activity and promotes CaN-dependent CREB and Bcl-2 Asociated death Protein (BAD) dephosphorylation and cell death. Furthermore, Tg2576 mice display Abeta oligomers and reduced pCREB in the CNS, which is normalized by CaN inhibition. These findings suggest a role for CaN in mediating effects of oligomeric Abeta on neural cells. Because elevated CaN levels have been reported in the CNS of cognitively impaired aged rodents, our results further suggest that abnormal CaN hyperactivity may be a common event exacerbating the cognitive and neurodegenerative impact of oligomeric Abeta in the aging CNS.

    Funded by: NIEHS NIH HHS: T32 ES007254; NINDS NIH HHS: F31 NS062558, NS053986, R21 NS053986, R21 NS053986-02

    Aging cell 2008;7;6;824-35

  • Transient intraneuronal A beta rather than extracellular plaque pathology correlates with neuron loss in the frontal cortex of APP/PS1KI mice.

    Christensen DZ, Kraus SL, Flohr A, Cotel MC, Wirths O and Bayer TA

    Division of Molecular Psychiatry and Alzheimer Ph.D. Graduate School, Department of Psychiatry, University of Goettingen, von-Siebold-Str. 5, 37075, Göttingen, Germany.

    The accumulation of beta-amyloid (A beta) plaques and neurofibrillary tangles consisting of hyperphosphorylated tau protein are pathological features of Alzheimer's disease (AD) commonly modeled in mice using known human familial mutations; however, the loss of neurons also found to occur in AD is rarely observed in such models. The mechanism of neuron degeneration remains unclear but is of great interest as it is very likely an important factor for the onset of adverse memory deficits occurring in individuals with AD. The role of A beta in the neuronal degeneration is a matter of controversial debates. In the present study we investigated the impact of extracellular plaque A beta versus intraneuronal A beta on neuronal cell death. The thalamus and the frontal cortex of the APP/PS1KI mouse model were chosen for stereological quantification representing regions with plaques only (thalamus) or plaques as well as intraneuronal A beta (frontal cortex). A loss of neurons was found in the frontal cortex at the age of 6 months coinciding with the decrease of intraneuronal immunoreactivity, suggesting that the neurons with early intraneuronal A beta accumulation were lost. Strikingly, no neuron loss was observed in the thalamus despite the development of abundant plaque pathology with levels comparable to the frontal cortex. This study suggests that plaques have no effect on neuron death whereas accumulation of intraneuronal A beta may be an early transient pathological event leading to neuron loss in AD.

    Acta neuropathologica 2008;116;6;647-55

  • Molecular structural basis for polymorphism in Alzheimer's beta-amyloid fibrils.

    Paravastu AK, Leapman RD, Yau WM and Tycko R

    Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA.

    We describe a full structural model for amyloid fibrils formed by the 40-residue beta-amyloid peptide associated with Alzheimer's disease (Abeta(1-40)), based on numerous constraints from solid state NMR and electron microscopy. This model applies specifically to fibrils with a periodically twisted morphology, with twist period equal to 120 +/- 20 nm (defined as the distance between apparent minima in fibril width in negatively stained transmission electron microscope images). The structure has threefold symmetry about the fibril growth axis, implied by mass-per-length data and the observation of a single set of (13)C NMR signals. Comparison with a previously reported model for Abeta(1-40) fibrils with a qualitatively different, striated ribbon morphology reveals the molecular basis for polymorphism. At the molecular level, the 2 Abeta(1-40) fibril morphologies differ in overall symmetry (twofold vs. threefold), the conformation of non-beta-strand segments, and certain quaternary contacts. Both morphologies contain in-register parallel beta-sheets, constructed from nearly the same beta-strand segments. Because twisted and striated ribbon morphologies are also observed for amyloid fibrils formed by other polypeptides, such as the amylin peptide associated with type 2 diabetes, these structural variations may have general implications.

    Funded by: Intramural NIH HHS

    Proceedings of the National Academy of Sciences of the United States of America 2008;105;47;18349-54

  • Valproic acid inhibits Abeta production, neuritic plaque formation, and behavioral deficits in Alzheimer's disease mouse models.

    Qing H, He G, Ly PT, Fox CJ, Staufenbiel M, Cai F, Zhang Z, Wei S, Sun X, Chen CH, Zhou W, Wang K and Song W

    Department of Psychiatry, Townsend Family Laboratories, Brain Research Center, University of British Columbia, Vancouver, BC, Canada.

    Neuritic plaques in the brains are one of the pathological hallmarks of Alzheimer's disease (AD). Amyloid beta-protein (Abeta), the central component of neuritic plaques, is derived from beta-amyloid precursor protein (APP) after beta- and gamma-secretase cleavage. The molecular mechanism underlying the pathogenesis of AD is not yet well defined, and there has been no effective treatment for AD. Valproic acid (VPA) is one of the most widely used anticonvulsant and mood-stabilizing agents for treating epilepsy and bipolar disorder. We found that VPA decreased Abeta production by inhibiting GSK-3beta-mediated gamma-secretase cleavage of APP both in vitro and in vivo. VPA treatment significantly reduced neuritic plaque formation and improved memory deficits in transgenic AD model mice. We also found that early application of VPA was important for alleviating memory deficits of AD model mice. Our study suggests that VPA may be beneficial in the prevention and treatment of AD.

    The Journal of experimental medicine 2008;205;12;2781-9

  • Association between the SERPING1 gene and age-related macular degeneration: a two-stage case-control study.

    Ennis S, Jomary C, Mullins R, Cree A, Chen X, Macleod A, Jones S, Collins A, Stone E and Lotery A

    Genetic Epidemiology and Bioinformatics Group, University of Southampton, Human Genetics Division (Mp 808), Southampton General Hospital, Southampton, UK.

    Background: Age-related macular degeneration is the most prevalent form of visual impairment and blindness in developed countries. Genetic studies have made advancements in establishing the molecular cause of this disease, identifying mutations in the complement factor H (CFH) gene and a locus on chromosome 10 encompassing the HTRA1/LOC387715/ARMS2 genes. Variants in complement 3 (C3) and an HLA locus containing both factor B and C2 genes have also been implicated. We aimed to identify further genetic risk factors for this disease.

    Methods: We used a case-control study design in a UK sample of patients with age-related macular degeneration (n=479) and controls (n=479) and undertook a low-density screen of 32 genes using 93 single nucleotide polymorphisms (SNPs). Genes were selected as candidates on the basis of potential functional relevance to age-related macular degeneration. Significant initial findings were confirmed by replication in an independent US cohort of 248 unrelated patients with disease and 252 controls, and by high-density genotyping around association signals.

    Findings: The SNP variant rs2511989, located within intron six of the SERPING1 gene, showed highly significant genotypic association with age-related macular degeneration (uncorrected p=4.0x10(-5), corrected p=0.00372). We detected no evidence for association between disease and the other 31 candidate genes. The odds ratio for age-related macular degeneration in rs2511989 G/A heterozygotes compared with wild type G/G homozygotes was 0.63 (95% CI 0.47-0.84). A similar comparison of the A/A homozygotes with the wild type yielded an odds ratio of 0.44 (0.31-0.64). We replicated the observed genotypic association in a US cohort (p=0.008). Furthermore, a secondary high-density genotyping study across the SERPING1 gene region identified five additional SNP variants similarly associated with age-related macular degeneration (rs2244169, rs2511990, rs2509897, rs1005510, and rs2511988).

    Interpretation: Genetic variation in SERPING1 significantly alters susceptibility to age-related macular degeneration. SERPING1 encodes the C1 inhibitor, which has a crucial role in inhibition of complement component 1 (C1) and might implicate the classic pathway of complement activation in this disease.

    Funded by: Howard Hughes Medical Institute; NEI NIH HHS: EY-016822, EY-017451, R01 EY016822, R01 EY017451; Wellcome Trust: 076169

    Lancet (London, England) 2008;372;9652;1828-34

  • Effects of grape seed-derived polyphenols on amyloid beta-protein self-assembly and cytotoxicity.

    Ono K, Condron MM, Ho L, Wang J, Zhao W, Pasinetti GM and Teplow DB

    Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7334, USA.

    Epidemiological evidence suggests that moderate consumption of red wine reduces the incidence of Alzheimer disease (AD). To study the protective effects of red wine, experiments recently were executed in the Tg2576 mouse model of AD. These studies showed that a commercially available grape seed polyphenolic extract, MegaNatural-AZ (MN), significantly attenuated AD-type cognitive deterioration and reduced cerebral amyloid deposition (Wang, J., Ho, L., Zhao, W., Ono, K., Rosensweig, C., Chen, L., Humala, N., Teplow, D. B., and Pasinetti, G. M. (2008) J. Neurosci. 28, 6388-6392). To elucidate the mechanistic bases for these observations, here we used CD spectroscopy, photo-induced cross-linking of unmodified proteins, thioflavin T fluorescence, size exclusion chromatography, and electron microscopy to examine the effects of MN on the assembly of the two predominant disease-related amyloid beta-protein alloforms, Abeta40 and Abeta42. We also examined the effects of MN on Abeta-induced cytotoxicity by assaying 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide metabolism and lactate dehydrogenase activity in Abeta-treated, differentiated pheochromocytoma (PC12) cells. Initial studies revealed that MN blocked Abeta fibril formation. Subsequent evaluation of the assembly stage specificity of the effect showed that MN was able to inhibit protofibril formation, pre-protofibrillar oligomerization, and initial coil --> alpha-helix/beta-sheet secondary structure transitions. Importantly, MN had protective effects in assays of cytotoxicity in which MN was mixed with Abeta prior to peptide assembly or following assembly and just prior to peptide addition to cells. These data suggest that MN is worthy of consideration as a therapeutic agent for AD.

    Funded by: NCCIH NIH HHS: P01 AT004511; NIA NIH HHS: AG027818

    The Journal of biological chemistry 2008;283;47;32176-87

  • Sulfated polysaccharides promote the assembly of amyloid beta(1-42) peptide into stable fibrils of reduced cytotoxicity.

    Bravo R, Arimon M, Valle-Delgado JJ, García R, Durany N, Castel S, Cruz M, Ventura S and Fernàndez-Busquets X

    Biomolecular Interactions Team, Nanobioengineering Group, Institute for Bioengineering of Catalonia, Barcelona Science Park, University of Barcelona, Baldiri Reixac 10, Barcelona E08028, Spain.

    The histopathological hallmarks of Alzheimer disease are the self-aggregation of the amyloid beta peptide (Abeta) in extracellular amyloid fibrils and the formation of intraneuronal Tau filaments, but a convincing mechanism connecting both processes has yet to be provided. Here we show that the endogenous polysaccharide chondroitin sulfate B (CSB) promotes the formation of fibrillar structures of the 42-residue fragment, Abeta(1-42). Atomic force microscopy visualization, thioflavin T fluorescence, CD measurements, and cell viability assays indicate that CSB-induced fibrils are highly stable entities with abundant beta-sheet structure that have little toxicity for neuroblastoma cells. We propose a wedged cylinder model for Abeta(1-42) fibrils that is consistent with the majority of available data, it is an energetically favorable assembly that minimizes the exposure of hydrophobic areas, and it explains why fibrils do not grow in thickness. Fluorescence measurements of the effect of different Abeta(1-42) species on Ca(2+) homeostasis show that weakly structured nodular fibrils, but not CSB-induced smooth fibrils, trigger a rise in cytosolic Ca(2+) that depends on the presence of both extracellular and intracellular stocks. In vitro assays indicate that such transient, local Ca(2+) increases can have a direct effect in promoting the formation of Tau filaments similar to those isolated from Alzheimer disease brains.

    The Journal of biological chemistry 2008;283;47;32471-83

  • Oxidative damage in brain from human mutant APP/PS-1 double knock-in mice as a function of age.

    Abdul HM, Sultana R, St Clair DK, Markesbery WR and Butterfield DA

    Department of Chemistry, Center for Membrane Sciences, University of Kentucky, Lexington, KY 40506-0055, USA.

    Oxidative stress is strongly implicated in the progressive decline of cognition associated with aging and neurodegenerative disorders. In the brain, free radical-mediated oxidative stress plays a critical role in the age-related decline of cellular function as a result of the oxidation of proteins, lipids, and nucleic acids. A number of studies indicate that an increase in protein oxidation and lipid peroxidation is associated with age-related neurodegenerative diseases and cellular dysfunction observed in aging brains. Oxidative stress is one of the important factors contributing to Alzheimer's disease (AD), one of whose major hallmarks includes brain depositions of amyloid beta-peptide (Abeta) derived from amyloid precursor protein (APP). Mutation in APP and PS-1 genes, which increases production of the highly amyloidogenic amyloid beta-peptide (Abeta42), is the major cause of familial AD. In the present study, protein oxidation and lipid peroxidation in the brain from knock-in mice expressing human mutant APP and PS-1 were compared with brain from wild type, as a function of age. The results suggest that there is an increased oxidative stress in the brain of wild-type mice as a function of age. In APP/PS-1 mouse brain, there is a basal increase (at 1 month) in oxidative stress compared to the wild type (1 month), as measured by protein oxidation and lipid peroxidation. In addition, age-related elevation of oxidative damage was observed in APP/PS-1 mice brain compared to that of wild-type mice brain. These results are discussed with reference to the importance of Abeta42-associated oxidative stress in the pathogenesis of AD.

    Funded by: NIA NIH HHS: AG-029839, AG-05119, AG-10836, P01 AG005119, P01 AG005119-110001, P01 AG005119-120001, P01 AG005119-12S20001, P01 AG005119-130001, P01 AG005119-13S10001, P01 AG005119-140001, P01 AG005119-20A10010, P01 AG010836, P01 AG010836-110011, P01 AG010836-120011, P01 AG010836-130011, P01 AG010836-140011, P01 AG010836-150011, R01 AG029839

    Free radical biology & medicine 2008;45;10;1420-5

  • Diagnostic utility of APOE, soluble CD40, CD40L, and Abeta1-40 levels in plasma in Alzheimer's disease.

    Ait-ghezala G, Abdullah L, Volmar CH, Paris D, Luis CA, Quadros A, Mouzon B, Mullan MA, Keegan AP, Parrish J, Crawford FC, Mathura VS and Mullan MJ

    Roskamp Institute, 2040 Whitfield Avenue, Sarasota, FL 34243, USA. gaitghezala@rfdn.org

    A continuous inflammatory state is associated with Alzheimer's disease (AD) evidenced by an increase in proinflammatory cytokines around beta-amyloid (Abeta) deposits. In addition, functional loss of CD40L is shown to result in diminished Amyloid precursor proton (APP) processing and microglial activation, supporting a prominent role of CD40-CD40L in AD etiology. We therefore hypothesize that a peripheral increase in Abeta may result in corresponding increase of sCD40 and sCD40L further contributing to AD pathogenesis. We measured plasma Abeta, sCD40 and sCD40L levels in 73 AD patients and compared to 102 controls matched on general demographics. We demonstrated that Abeta(1-40), levels of sCD40 and sCD40L are increased in AD and declining MMSE scores correlated with increasing sCD40L, which in turn, correlated positively with Abeta(1-42). We then combined sCD40, sCD40L, Abeta and APOE and found that this biomarker panel has high sensitivity and specificity (>90%) as a predictor of clinical AD diagnosis. Given the imminent availability of potentially disease modifying therapies for AD, a great need exists for peripheral diagnostic markers of AD. Thus, we present preliminary evidence for potential usefulness for combination of plasma sCD40, sCD40L along with Abeta(1-40) and APOE epsilon4 in improving the clinical diagnosis of AD.

    Cytokine 2008;44;2;283-7

  • Increased bisecting and core-fucosylated N-glycans on mutant human amyloid precursor proteins.

    Akasaka-Manya K, Manya H, Sakurai Y, Wojczyk BS, Spitalnik SL and Endo T

    Glycobiology Research Group, Tokyo Metropolitan Institute of Gerontology, Foundation for Research on Aging and Promotion of Human Welfare, 35-2 Sakaecho, Itabashi-ku, Tokyo, 173-0015, Japan.

    Alteration of glycoprotein glycans often changes various properties of the glycoprotein. To understand the significance of N-glycosylation in the pathogenesis of early-onset familial Alzheimer's disease (AD) and in beta-amyloid (Abeta) production, we examined whether the mutations in the amyloid precursor protein (APP) gene found in familial AD affect the N-glycans on APP. We purified the secreted forms of wild-type and mutant human APPs (both the Swedish type and the London type) produced by transfected C17 cells and determined the N-glycan structures of these three recombinant APPs. Although the major N-glycan species of the three APPs were similar, both mutant APPs contained higher contents of bisecting N-acetylglucosamine and core-fucose residues as compared to wild-type APP. These results demonstrate that familial AD mutations in the polypeptide backbone of APP can affect processing of the attached N-glycans; however, whether these changes in N-glycosylation affect Abeta production remains to be established.

    Glycoconjugate journal 2008;25;8;775-86

  • Prion infection of mice transgenic for human APPSwe: increased accumulation of cortical formic acid extractable Abeta(1-42) and rapid scrapie disease development.

    Baier M, Apelt J, Riemer C, Gültner S, Schwarz A, Bamme T, Burwinkel M and Schliebs R

    Project Neurodegenerative Diseases, Robert-Koch-Institute, Nordufer 20, 13353 Berlin, Germany. baierm@rki.de

    Neuropathological, epidemiological and experimental data indicate a potential interrelationship between Alzheimer's disease and prion diseases. Proteolytic processing of amyloid precursor protein (APP) by beta-secretase was recently suggested to be controlled by prion protein expression. Here, we characterized the prion infection of Tg2576 mice, which overexpress the human APP(Swe) protein. Prion infection of Tg2576-mice led to an early death of the animals, which was preceded by a relatively short symptomatic stage. However, disease-associated gliosis and deposition of misfolded prion protein PrP(Sc) were identical in infected Tg2576-mice and non-transgenic littermate controls. To analyze the effect of prion infection on APP processing and generation of beta-amyloid we determined cortical levels of SDS- and formic acid (FA)-extractable forms of beta-amyloid (1-40) and (1-42) by ELISA. Formic acid-extractable Abeta (1-42) levels were 10-fold higher in infected versus uninfected Tg2576 mice whereas other forms of Abeta were essentially unaffected by the prion infection. Hence, the experimental model demonstrates that a prion infection of the CNS promotes selectively formation of FA-extractable Abeta(1-42) in Tg2576 mice.

    International journal of developmental neuroscience : the official journal of the International Society for Developmental Neuroscience 2008;26;7;821-4

  • Structure of the intracellular domain of the amyloid precursor protein in complex with Fe65-PTB2.

    Radzimanowski J, Simon B, Sattler M, Beyreuther K, Sinning I and Wild K

    Heidelberg University Biochemistry Center, University of Heidelberg, INF328, D-69120 Heidelberg, Germany.

    Cleavage of the amyloid precursor protein (APP) is a crucial event in Alzheimer disease pathogenesis that creates the amyloid-beta peptide (Abeta) and liberates the carboxy-terminal APP intracellular domain (AICD) into the cytosol. The interaction of the APP C terminus with the adaptor protein Fe65 mediates APP trafficking and signalling, and is thought to regulate APP processing and Abeta generation. We determined the crystal structure of the AICD in complex with the C-terminal phosphotyrosine-binding (PTB) domain of Fe65. The unique interface involves the NPxY PTB-binding motif and two alpha helices. The amino-terminal helix of the AICD is capped by threonine T(668), an Alzheimer disease-relevant phosphorylation site involved in Fe65-binding regulation. The structure together with mutational studies, isothermal titration calorimetry and nuclear magnetic resonance experiments sets the stage for understanding T(668) phosphorylation-dependent complex regulation at a molecular level. A molecular switch model is proposed.

    EMBO reports 2008;9;11;1134-40

  • Synergistic induction of ER stress by homocysteine and beta-amyloid in SH-SY5Y cells.

    Kim HJ, Cho HK and Kwon YH

    Department of Food and Nutrition, Seoul National University, Seoul 151-742, South Korea.

    Clinical studies have raised the possibility that elevated plasma levels of homocysteine increase the risk of atherosclerosis, stroke and possibly neurodegenerative diseases such as Alzheimer's disease (AD); however, the direct impact of homocysteine on neuron cells and the mechanism by which it could induce neurodegeneration have yet to be clearly demonstrated. Here, we investigated the effect of homocysteine on endoplasmic reticulum (ER) stress, the suggested mechanism of neurotoxicity, in human neuroblastoma SH-SY5Y cells. The effect of homocysteine on amyloid-beta (Abeta)-induced neurotoxicity and the protective activity of folate were also investigated. Homocysteine led to increased expressions of the binding protein (BiP) and the spliced form of X-box-protein (XBP)-1 mRNAs, suggesting activation of the unfolded-protein response and an increase in apoptosis. When cells were cotreated with homocysteine and Abeta, caspase-3 activity was significantly increased, and expressions of BiP and the spliced form of XBP-1 mRNAs were significantly induced. The neurotoxicity of homocysteine was attenuated by the treatment of cells with folate, as determined by caspase-3 activity and apoptotic body staining. These findings indicate that homocysteine induces ER stress and, ultimately, apoptosis and sensitizes neurons to amyloid toxicity via the synergistic induction of ER stress. Furthermore, a neuroprotective effect of folate against homocysteine-induced toxicity was also observed. Therefore, the findings of our study suggest that ER stress-induced homocysteine toxicity may play an important physiological role in enhancing the pathogenesis of Abeta-induced neuronal degeneration.

    The Journal of nutritional biochemistry 2008;19;11;754-61

  • The intracellular domain of amyloid precursor protein induces neuron-specific apoptosis.

    Nakayama K, Ohkawara T, Hiratochi M, Koh CS and Nagase H

    Department of Anatomy, Shinshu University, School of Medicine, Matsumoto, Nagano, Japan. kohzona@gipac.shinshu-u.ac.jp

    Although amyloid precursor protein (APP) has central roles in Alzheimer's disease, the physiological functions of this protein have yet to be fully elucidated. APP homologues show significant sequence conservation in the intracellular domain through evolution, which may reflect the functional importance of the intracellular domain of APP (AICD). To examine this possibility, we established embryonic carcinoma P19 cell lines overexpressing AICD. Although neurons could be differentiated from these cell lines with retinoic acid treatment, overexpression of AICD gave rise to neuron-specific cell death. Furthermore, DNA fragmentation was detected and TUNEL-positive cells were also Tuj1-positive neurons. Taken together, we concluded that AICD can induce neuron-specific apoptosis.

    Neuroscience letters 2008;444;2;127-31

  • Membrane microdomain switching: a regulatory mechanism of amyloid precursor protein processing.

    Sakurai T, Kaneko K, Okuno M, Wada K, Kashiyama T, Shimizu H, Akagi T, Hashikawa T and Nukina N

    Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan.

    Neuronal activity has an impact on beta cleavage of amyloid precursor protein (APP) by BACE1 to generate amyloid-beta peptide (Abeta). However, the molecular mechanisms underlying this effect remain to be elucidated. Cholesterol dependency of beta cleavage prompted us to analyze immunoisolated APP-containing detergent-resistant membranes from rodent brains. We found syntaxin 1 as a key molecule for activity-dependent regulation of APP processing in cholesterol-dependent microdomains. In living cells, APP associates with syntaxin 1-containing microdomains through X11-Munc18, which inhibits the APP-BACE1 interaction and beta cleavage via microdomain segregation. Phosphorylation of Munc18 by cdk5 causes a shift of APP to BACE1-containing microdomains. Neuronal hyperactivity, implicated in Abeta overproduction, promotes the switching of APP microdomain association as well as beta cleavage in a partially cdk5-dependent manner. We propose that microdomain switching is a mechanism of cholesterol- and activity-dependent regulation of APP processing in neurons.

    The Journal of cell biology 2008;183;2;339-52

  • Genetic association between low-density lipoprotein receptor-related protein gene polymorphisms and Alzheimer's disease in Chinese Han population.

    Zhou YT, Zhang ZX, Chan P, He XM, Tang MN, Wu CB and Hong Z

    Department of Neurology and Neurobiology, Key Laboratory of Neurodegenerative Diseases for Ministry of Education, Beijing Institute of Geriatrics and Xuanwu Hospital of Capital University of Medical Sciences, 100053 Beijing, China.

    Alzheimer's disease (AD) is the most common neurodegenerative disorders in the elderly. Low-density lipoprotein receptor-related protein (LRP), as a receptor of apolipoprotein E (APOE), APP, and alpha2 macroglobulin (alpha2-M), keeps the balance between degeneration and production of beta-amyloid protein (Abeta) clearance. Its gene had been defined as a candidate gene for AD, but the results were not universal. Total 496 AD patients and 478 controls were recruited in Chinese Han population and real-time PCR was used to detect the polymorphism of LRP C766T. Multiple logistic regression, Chi-square test and survival analysis were performed to explore the association. The distribution of LRP genotypes and alleles was significantly different between cases and controls, and T allele could reduce the risk for developing AD (OR of CT genotype: 0.57; 95% CI: 0.38-0.85, rho=0.003; OR of T allele: 0.57; 95% CI: 0.39-0.83, rho=0.003). TT genotype carriers had 5 years later for developing AD compared with CC genotype carriers, but survival analysis did not conform this (LRP TT vs. CT and CC log rank chi(2)=2.71, rho=0.26). The distribution of LRP C766T genotypes and alleles was different among different severity stratified by MMSE yet (rho=0.26). Our data suggested that the polymorphism of LRP C766T was strongly associated with AD and T allele might be a protective factor for AD in Chinese Han population.

    Neuroscience letters 2008;444;1;109-11

  • Sumoylation of amyloid precursor protein negatively regulates Abeta aggregate levels.

    Zhang YQ and Sarge KD

    Department of Molecular and Cellular Biochemistry, University of Kentucky, 741 S. Limestone Street, Lexington, KY 40536, USA.

    The proteolytic processing of amyloid precursor protein (APP) to produce Abeta peptides is thought to play an important role in the mechanism of Alzheimer's disease. Here, we show that lysines 587 and 595 of APP, which are immediately adjacent to the site of beta-secretase cleavage, are covalently modified by SUMO proteins in vivo. Sumoylation of these lysine residues is associated with decreased levels of Abeta aggregates. Further, overexpression of the SUMO E2 enzyme ubc9 along with SUMO-1 results in decreased levels of Abeta aggregates in cells transfected with the familial Alzheimer's disease-associated V642F mutant APP, indicating the potential of up-regulating activity of the cellular sumoylation machinery as an approach against Alzheimer's disease. The results also provide the first demonstration that the SUMO E2 enzyme (ubc9) is present within the endoplasmic reticulum, indicating how APP, and perhaps other proteins that enter this compartment, can be sumoylated.

    Funded by: NIGMS NIH HHS: GM64606, R01 GM061053, R01 GM061053-04, R01 GM064606, R01 GM064606-01A2, R01 GM064606-02, R01 GM064606-03, R01 GM064606-04

    Biochemical and biophysical research communications 2008;374;4;673-8

  • The structure of the amyloid-beta peptide high-affinity copper II binding site in Alzheimer disease.

    Streltsov VA, Titmuss SJ, Epa VC, Barnham KJ, Masters CL and Varghese JN

    Commonwealth Scientific Industrial Research Organization Molecular and Health Technologies, and Preventative Health Flagship, Parkville, Victoria 3052, Australia. victor.streltsov@csiro.au

    Neurodegeneration observed in Alzheimer disease (AD) is believed to be related to the toxicity from reactive oxygen species (ROS) produced in the brain by the amyloid-beta (Abeta) protein bound primarily to copper ions. The evidence for an oxidative stress role of Abeta-Cu redox chemistry is still incomplete. Details of the copper binding site in Abeta may be critical to the etiology of AD. Here we present the structure determined by combining x-ray absorption spectroscopy (XAS) and density functional theory analysis of Abeta peptides complexed with Cu(2+) in solution under a range of buffer conditions. Phosphate-buffered saline buffer salt (NaCl) concentration does not affect the high-affinity copper binding mode but alters the second coordination sphere. The XAS spectra for truncated and full-length Abeta-Cu(2+) peptides are similar. The novel distorted six-coordinated (3N3O) geometry around copper in the Abeta-Cu(2+) complexes include three histidines: glutamic, or/and aspartic acid, and axial water. The structure of the high-affinity Cu(2+) binding site is consistent with the hypothesis that the redox activity of the metal ion bound to Abeta can lead to the formation of dityrosine-linked dimers found in AD.

    Biophysical journal 2008;95;7;3447-56

  • Association between progranulin and beta-amyloid in dementia with Lewy bodies.

    Revuelta GJ, Rosso A and Lippa CF

    Department of Neurology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, USA.

    Recent studies demonstrated that progranulin plays an integral role in the pathogenesis of frontotemporal dementia. To begin to explore the role of progranulin in dementia with Lewy bodies, we investigate its association with pathologic proteins that characterize this disease. We assessed immunoreactivity for progranulin in medial temporal lobe structures of 12 cases of dementia with Lewy bodies. Similar data were collected for beta-amyloid burden, and alpha-synuclein pathology. Blinded investigators used a 0-3-point scale to quantify progranulin burden. Double labeling for progranulin and beta-amyloid was also performed. We were able to demonstrate progranulin immunoreactivity throughout the medial temporal lobe in all dementia with Lewy body cases. We identified a significant positive correlation (r = 0.606; P = .037) between beta-amyloid burden and progranulin. There was no significant correlation between alpha-synuclein pathology or Braak stage and progranulin. Progranulin and beta-amyloid colocalized in plaques in dementia with Lewy bodies, suggesting that there is likely a biological association between these 2 aggregated proteins.

    American journal of Alzheimer's disease and other dementias 2008;23;5;488-93

  • Beta-amyloid peptide stimulates endozepine release in cultured rat astrocytes through activation of N-formyl peptide receptors.

    Tokay T, Hachem R, Masmoudi-Kouki O, Gandolfo P, Desrues L, Leprince J, Castel H, Diallo M, Amri M, Vaudry H and Tonon MC

    INSERM U413, Laboratory of Cellular and Molecular Neuroendocrinology, University of Rouen, Mont-Saint-Aignan, France.

    Astroglial cells synthesize and release endozepines, a family of neuropeptides derived from diazepam-binding inhibitor (DBI). The authors have recently shown that beta-amyloid peptide (Abeta) stimulates DBI gene expression and endozepine release. The purpose of this study was to determine the mechanism of action of Abeta in cultured rat astrocytes. Abeta(25-35) and the N-formyl peptide receptor (FPR) agonist N-formyl-Met-Leu-Phe (fMLF) increased the secretion of endozepines in a dose-dependent manner with EC(50) value of approximately 2 microM. The stimulatory effects of Abeta(25-35) and the FPR agonists fMLF and N-formyl-Met-Met-Met (fMMM) on endozepine release were abrogated by the FPR antagonist N-t-Boc-Phe-Leu-Phe-Leu-Phe. In contrast, Abeta(25-35) increased DBI mRNA expression through a FPR-independent mechanism. Abeta(25-35) induced a transient stimulation of cAMP formation and a sustained activation of polyphosphoinositide turnover. The stimulatory effect of Abeta(25-35) on endozepine release was blocked by the adenylyl cyclase inhibitor somatostatin, the protein kinase A (PKA) inhibitor H89, the phospholipase C inhibitor U73122, the protein kinase C (PKC) inhibitor chelerythrine and the ATP binding cassette transporter blocker glyburide. Taken together, these data demonstrate for the first time that Abeta(25-35) stimulates endozepine release from rat astrocytes through a FPR receptor positively coupled to PKA and PKC.

    Glia 2008;56;13;1380-9

  • Cyclophilin D deficiency attenuates mitochondrial and neuronal perturbation and ameliorates learning and memory in Alzheimer's disease.

    Du H, Guo L, Fang F, Chen D, Sosunov AA, McKhann GM, Yan Y, Wang C, Zhang H, Molkentin JD, Gunn-Moore FJ, Vonsattel JP, Arancio O, Chen JX and Yan SD

    Department of Surgery, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, New York 10032, USA.

    Cyclophilin D (CypD, encoded by Ppif) is an integral part of the mitochondrial permeability transition pore, whose opening leads to cell death. Here we show that interaction of CypD with mitochondrial amyloid-beta protein (Abeta) potentiates mitochondrial, neuronal and synaptic stress. The CypD-deficient cortical mitochondria are resistant to Abeta- and Ca(2+)-induced mitochondrial swelling and permeability transition. Additionally, they have an increased calcium buffering capacity and generate fewer mitochondrial reactive oxygen species. Furthermore, the absence of CypD protects neurons from Abeta- and oxidative stress-induced cell death. Notably, CypD deficiency substantially improves learning and memory and synaptic function in an Alzheimer's disease mouse model and alleviates Abeta-mediated reduction of long-term potentiation. Thus, the CypD-mediated mitochondrial permeability transition pore is directly linked to the cellular and synaptic perturbations observed in the pathogenesis of Alzheimer's disease. Blockade of CypD may be a therapeutic strategy in Alzheimer's disease.

    Funded by: NIA NIH HHS: P01 AG017490, P01 AG017490-08, P01 AG17490, P050 AG08702, P50 AG008702, P50 AG008702-11A19002

    Nature medicine 2008;14;10;1097-105

  • Heparan sulfate accumulation with Abeta deposits in Alzheimer's disease and Tg2576 mice is contributed by glial cells.

    O'Callaghan P, Sandwall E, Li JP, Yu H, Ravid R, Guan ZZ, van Kuppevelt TH, Nilsson LN, Ingelsson M, Hyman BT, Kalimo H, Lindahl U, Lannfelt L and Zhang X

    Department of Public Health and Caring Sciences, Division of Molecular Geriatrics, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden.

    Amyloid beta-peptide (Abeta) plaques, one of the major neuropathological lesions in Alzheimer's disease (AD), can be broadly subdivided into two morphological categories: neuritic and diffuse. Heparan sulfate (HS) and HS proteoglycans (HSPGs) are codeposits of multiple amyloidoses, including AD. Although HS has been considered a limiting factor in the initiation of amyloid deposition, the pathological implications of HS in Abeta deposits of AD remain unclear. In this study, immunohistochemistry combined with fluorescence and confocal microscopy was employed to gain deeper insight into the accumulation of HS with Abeta plaques in sporadic and familial AD. Here we demonstrate that HS preferentially accumulated around the Abeta40 dense cores of neuritic plaques, but was largely absent from diffuse Abeta42 plaques, suggesting that Abeta42 deposition may occur independently of HS. A codeposition pattern of HS with Abeta deposits in Tg2576 mice was also examined. We identified the membrane-bound HSPGs, glypican-1 (GPC1) and syndecan-3 (SDC3), in glial cells associated with Abeta deposits, proximal to sites of HS accumulation. In mouse primary glial cultures, we observed increased levels of GPC1 and SDC3 following Abeta stimulation. These results suggest that HS codeposits with Abeta40 in neuritic plaques and is mainly derived from glial cells.

    Funded by: NIA NIH HHS: P50 AG005134-26, PS0AG05134

    Brain pathology (Zurich, Switzerland) 2008;18;4;548-61

  • Phosphorylated tau in neuritic plaques of APP(sw)/Tau (vlw) transgenic mice and Alzheimer disease.

    Pérez M, Morán MA, Ferrer I, Avila J and Gómez-Ramos P

    Departamento de Anatomía, Histología y Neurociencia, Facultad de Medicina, Universidad Autónoma de Madrid, C/Arzobispo Morcillo s/n, 28029 Madrid, Spain.

    We have previously reported that double-transgenic APP(SW)/Tau(VLW) mice show enhanced amyloid deposition, stronger tau hyperphosphorylation, increased sarkosyl tau polymers, and wider tau filaments when compared to simple mutant models. To validate these transgenic mice as models of Alzheimer disease pathology, in the present study we analyze tau phosphorylation at 12E8 and AT-8 epitopes in amyloid plaques. In APP(SW) mice, phospho-tau in plaque-associated neurites suggests a local direct effect of plaque-amyloid (and/or APP(SW)) on tau phosphorylation. In vitro, attempts to identify which kinases are induced by fibrillar amyloid reveal to Protein Kinase C as responsible for phosphorylation at the 12E8 epitope. Tau(VLW) mice, without plaques, show increased tau phosphorylation at the 12E8 epitope, particularly in pyramidal neurons. APP(SW)/Tau(VLW) mice show earlier and stronger 12E8 tau phosphorylation. Ultrastructurally, the same two types of neurites are found in plaques from APP(SW)/Tau(VLW) and Alzheimer disease (AD) brains: (a) dystrophic giant neurites filled with degenerating organelles and/or phospho-tau-positive filaments and (b) non-dystrophic phospho-tau-positive small punctiform neurites. Both types of plaque-associated neurites are AT-8 positive in APP(SW)/Tau(VLW) mice and AD, but 12E8-positive dystrophic neurites are only detected in AD. We conclude that the simultaneous presence of human mutated Tau(VLW) and plaque-amyloid (and/or APP(SW)) potentiates and anticipates tau phosphorylation at the 12E8 epitope, intensifying pyramidal neuron immunostaining and tau filament formation in this double-transgenic model. Thus, the APP(SW)/Tau(VLW) mouse is a useful model to study neuritic plaques, since they reproduce most of the characteristics that these structures have in AD.

    Acta neuropathologica 2008;116;4;409-18

  • Secondary structure conversions of Alzheimer's Abeta(1-40) peptide induced by membrane-mimicking detergents.

    Wahlström A, Hugonin L, Perálvarez-Marín A, Jarvet J and Gräslund A

    Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, Sweden.

    The amyloid beta peptide (Abeta) with 39-42 residues is the major component of amyloid plaques found in brains of Alzheimer's disease patients, and soluble oligomeric peptide aggregates mediate toxic effects on neurons. The Abeta aggregation involves a conformational change of the peptide structure to beta-sheet. In the present study, we report on the effect of detergents on the structure transitions of Abeta, to mimic the effects that biomembranes may have. In vitro, monomeric Abeta(1-40) in a dilute aqueous solution is weakly structured. By gradually adding small amounts of sodium dodecyl sulfate (SDS) or lithium dodecyl sulfate to a dilute aqueous solution, Abeta(1-40) is converted to beta-sheet, as observed by CD at 3 degrees C and 20 degrees C. The transition is mainly a two-state process, as revealed by approximately isodichroic points in the titrations. Abeta(1-40) loses almost all NMR signals at dodecyl sulfate concentrations giving rise to the optimal beta-sheet content (approximate detergent/peptide ratio = 20). Under these conditions, thioflavin T fluorescence measurements indicate a maximum of aggregated amyloid-like structures. The loss of NMR signals suggests that these are also involved in intermediate chemical exchange. Transverse relaxation optimized spectroscopy NMR spectra indicate that the C-terminal residues are more dynamic than the others. By further addition of SDS or lithium dodecyl sulfate reaching concentrations close to the critical micellar concentration, CD, NMR and FTIR spectra show that the peptide rearranges to form a micelle-bound structure with alpha-helical segments, similar to the secondary structures formed when a high concentration of detergent is added directly to the peptide solution.

    The FEBS journal 2008;275;20;5117-28

  • Cross-strand pairing and amyloid assembly.

    Liang Y, Pingali SV, Jogalekar AS, Snyder JP, Thiyagarajan P and Lynn DG

    Center for Fundamental and Applied Molecular Evolution, Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.

    Amino acid cross-strand pairing interactions along a beta-sheet surface have been implicated in protein beta-structural assembly and stability, yet the relative contributions have been difficult to evaluate directly. Here we develop the central core sequence of the Abeta peptide associated with Alzheimer's disease, Abeta(16-22), as an experimental system for evaluating these interactions. The peptide allows for internal comparisons between electrostatic and steric interactions within the beta-sheet and an evaluation of these cross-strand pair contributions to beta-sheet registry. A morphological transition from fibers to hollow nanotubes arises from changes in beta-sheet surface complementarity and provides a convenient indicator of the beta-strand strand registry. The intrinsic beta-sequence and pair correlations are critical to regulate secondary assembly. These studies provide evidence for a critical desolvation step that is not present in most models of the nucleation-dependent pathway for amyloid assembly.

    Biochemistry 2008;47;38;10018-26

  • Imaging amyloid deposition in Lewy body diseases.

    Gomperts SN, Rentz DM, Moran E, Becker JA, Locascio JJ, Klunk WE, Mathis CA, Elmaleh DR, Shoup T, Fischman AJ, Hyman BT, Growdon JH and Johnson KA

    Massachusetts General Hospital, Boston, MA 02114, USA.

    Background: Extrapyramidal motor symptoms precede dementia in Parkinson disease (PDD) by many years, whereas dementia occurs early in dementia with Lewy bodies (DLB). Despite this clinical distinction, the neuropsychological and neuropathologic features of these conditions overlap. In addition to widespread distribution of Lewy bodies, both diseases have variable burdens of neuritic plaques and neurofibrillary tangles characteristic of Alzheimer disease (AD).

    Objectives: To determine whether amyloid deposition, as assessed by PET imaging with the beta-amyloid-binding compound Pittsburgh Compound B (PiB), can distinguish DLB from PDD, and to assess whether regional patterns of amyloid deposition correlate with specific motor or cognitive features.

    Methods: Eight DLB, 7 PDD, 11 Parkinson disease (PD), 15 AD, and 37 normal control (NC) subjects underwent PiB-PET imaging and neuropsychological assessment. Amyloid burden was quantified using the PiB distribution volume ratio.

    Results: Cortical amyloid burden was higher in the DLB group than in the PDD group, comparable to the AD group. Amyloid deposition in the PDD group was low, comparable to the PD and NC groups. Relative to global cortical retention, occipital PiB retention was lower in the AD group than in the other groups. For the DLB, PDD, and PD groups, amyloid deposition in the parietal (lateral and precuneus)/posterior cingulate region was related to visuospatial impairment. Striatal PiB retention in the DLB and PDD groups was associated with less impaired motor function.

    Conclusions: Global cortical amyloid burden is high in dementia with Lewy bodies (DLB) but low in Parkinson disease dementia. These data suggest that beta-amyloid may contribute selectively to the cognitive impairment of DLB and may contribute to the timing of dementia relative to the motor signs of parkinsonism.

    Funded by: NIA NIH HHS: 3R01AG027435-02S1, P01 AG025204, P01 AG025204-040001, P50 AG005133, P50 AG005133-250021, P50 AG05133, P50-AG05134, R01 AG018402, R37 AG025516, R37 AG025516-04, RF1 AG025516; NINDS NIH HHS: P50-NS38372, R21-NS060310

    Neurology 2008;71;12;903-10

  • Numb endocytic adapter proteins regulate the transport and processing of the amyloid precursor protein in an isoform-dependent manner: implications for Alzheimer disease pathogenesis.

    Kyriazis GA, Wei Z, Vandermey M, Jo DG, Xin O, Mattson MP and Chan SL

    Biomolecular Science Center, University of Central Florida, 4000 Central Florida Boulevard, Orlando, FL 32816, USA.

    Central to the pathogenesis of Alzheimer disease is the aberrant processing of the amyloid precursor protein (APP) to generate amyloid beta-peptide (Abeta), the principle component of amyloid plaques. The cell fate determinant Numb is a phosphotyrosine binding domain (PTB)-containing endocytic adapter protein that interacts with the carboxyl-terminal domain of APP. The physiological relevance of this interaction is unknown. Mammals produce four alternatively spliced variants of Numb that differ in the length of their PTB and proline-rich region. In the current study, we determined the influence of the four human Numb isoforms on the intracellular trafficking and processing of APP. Stable expression of Numb isoforms that differ in the PTB but not in the proline-rich region results in marked differences in the sorting of APP to the recycling and degradative pathways. Neural cells expressing Numb isoforms that lack the insert in the PTB (short PTB (SPTB)) exhibited marked accumulation of APP in Rab5A-labeled early endosomal and recycling compartments, whereas those expressing isoforms with the insertion in the PTB (long PTB (LPTB)) exhibited reduced amounts of cellular APP and its proteolytic derivatives relative to parental control cells. Neither the activities of the beta- and gamma-secretases nor the expression of APP mRNA were significantly different in the stably transfected cells, suggesting that the differential effects of the Numb proteins on APP metabolism is likely to be secondary to altered APP trafficking. In addition, the expression of SPTB-Numb increases at the expense of LPTB-Numb in neuronal cultures subjected to stress, suggesting a role for Numb in stress-induced Abeta production. Taken together, these results suggest distinct roles for the human Numb isoforms in APP metabolism and may provide a novel potential link between altered Numb isoform expression and increased Abeta generation.

    The Journal of biological chemistry 2008;283;37;25492-502

  • Structural studies of the transmembrane C-terminal domain of the amyloid precursor protein (APP): does APP function as a cholesterol sensor?

    Beel AJ, Mobley CK, Kim HJ, Tian F, Hadziselimovic A, Jap B, Prestegard JH and Sanders CR

    Department of Biochemistry and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37232-8725, USA.

    The amyloid precursor protein (APP) is subject to alternative pathways of proteolytic processing, leading either to production of the amyloid-beta (Abeta) peptides or to non-amyloidogenic fragments. Here, we report the first structural study of C99, the 99-residue transmembrane C-terminal domain of APP liberated by beta-secretase cleavage. We also show that cholesterol, an agent that promotes the amyloidogenic pathway, specifically binds to this protein. C99 was purified into model membranes where it was observed to homodimerize. NMR data show that the transmembrane domain of C99 is an alpha-helix that is flanked on both sides by mostly disordered extramembrane domains, with two exceptions. First, there is a short extracellular surface-associated helix located just after the site of alpha-secretase cleavage that helps to organize the connecting loop to the transmembrane domain, which is known to be essential for Abeta production. Second, there is a surface-associated helix located at the cytosolic C-terminus, adjacent to the YENPTY motif that plays critical roles in APP trafficking and protein-protein interactions. Cholesterol was seen to participate in saturable interactions with C99 that are centered at the critical loop connecting the extracellular helix to the transmembrane domain. Binding of cholesterol to C99 and, most likely, to APP may be critical for the trafficking of these proteins to cholesterol-rich membrane domains, which leads to cleavage by beta- and gamma-secretase and resulting amyloid-beta production. It is proposed that APP may serve as a cellular cholesterol sensor that is linked to mechanisms for suppressing cellular cholesterol uptake.

    Funded by: NIA NIH HHS: R21 AG026581, R21 AG026581-02, R21 AG236581; NIGMS NIH HHS: 5P41GM066340-05, P01 GM080513, P01 GM080513-01A1, P01 GM080513-01A10003, P01 GM80513, P41 GM066340-05

    Biochemistry 2008;47;36;9428-46

  • Region-specific changes in the microanatomy of single dendritic spines over time might account for selective memory alterations in ageing hAPPsweTg2576 mice, a mouse model for Alzheimer disease.

    Middei S, Restivo L, Caprioli A, Aceti M and Ammassari-Teule M

    CNR Institute for Neuroscience, S. Lucia Foundation, Via del Fosso di Fiorano 64/65, 00143 Rome, Italy. s.middei@hsantalucia.it

    Tg2576 mice over-expressing human mutant APP (hAPPswe) show progressive impairments in hippocampal plasticity and episodic memory while fronto-striatal plasticity and procedural memory remain intact. Here we examine the status of synaptic connectivity in the hippocampus and the dorsolateral striatum (DLS) of 3- and 15-month-old Tg2576 and wild-type mice through the analysis of single dendritic spines microanatomy. We found that, in each region, all mice showed a global reduction in the size of spines as a function of age. Ageing mutants, however, exhibited smaller spines with shorter necks on CA1 pyramidal neurons but larger spines with longer necks on DLS spiny neurons compared to their age-matched wild-type controls. Our findings indicate that hippocampal and DLS dendritic spines in hAPPswe mutants undergo a different pattern of morphological changes over time and point to minor alterations in the microanatomy of DLS spines as a compensatory mechanism maintaining procedural abilities in the ageing mutants.

    Neurobiology of learning and memory 2008;90;2;467-71

  • Amyloid-beta dynamics correlate with neurological status in the injured human brain.

    Brody DL, Magnoni S, Schwetye KE, Spinner ML, Esparza TJ, Stocchetti N, Zipfel GJ and Holtzman DM

    Department of Neurology, Washington University, St. Louis, MO 63110, USA. brodyd@neuro.wustl.edu

    The amyloid-beta peptide (Abeta) plays a central pathophysiological role in Alzheimer's disease, but little is known about the concentration and dynamics of this secreted peptide in the extracellular space of the human brain. We used intracerebral microdialysis to obtain serial brain interstitial fluid (ISF) samples in 18 patients who were undergoing invasive intracranial monitoring after acute brain injury. We found a strong positive correlation between changes in brain ISF Abeta concentrations and neurological status, with Abeta concentrations increasing as neurological status improved and falling when neurological status declined. Brain ISF Abeta concentrations were also lower when other cerebral physiological and metabolic abnormalities reflected depressed neuronal function. Such dynamics fit well with the hypothesis that neuronal activity regulates extracellular Abeta concentration.

    Funded by: NIDDK NIH HHS: P30 DK056341, P30 DK056341-07, P30 DK056341-08; NINDS NIH HHS: K08 NS049237-01, K08 NS049237-02, K08 NS049237-03, K08 NS049237-04, K08 NS049237-05

    Science (New York, N.Y.) 2008;321;5893;1221-4

  • The amyloid-beta rise and gamma-secretase inhibitor potency depend on the level of substrate expression.

    Burton CR, Meredith JE, Barten DM, Goldstein ME, Krause CM, Kieras CJ, Sisk L, Iben LG, Polson C, Thompson MW, Lin XA, Corsa J, Fiedler T, Pierdomenico M, Cao Y, Roach AH, Cantone JL, Ford MJ, Drexler DM, Olson RE, Yang MG, Bergstrom CP, McElhone KE, Bronson JJ, Macor JE, Blat Y, Grafstrom RH, Stern AM, Seiffert DA, Zaczek R, Albright CF and Toyn JH

    Bristol-Myers Squibb Research and Development, Wallingford, Connecticut 06492, USA.

    The amyloid-beta (Abeta) peptide, which likely plays a key role in Alzheimer disease, is derived from the amyloid-beta precursor protein (APP) through consecutive proteolytic cleavages by beta-site APP-cleaving enzyme and gamma-secretase. Unexpectedly gamma-secretase inhibitors can increase the secretion of Abeta peptides under some circumstances. This "Abeta rise" phenomenon, the same inhibitor causing an increase in Abeta at low concentrations but inhibition at higher concentrations, has been widely observed. Here we show that the Abeta rise depends on the beta-secretase-derived C-terminal fragment of APP (betaCTF) or C99 levels with low levels causing rises. In contrast, the N-terminally truncated form of Abeta, known as "p3," formed by alpha-secretase cleavage, did not exhibit a rise. In addition to the Abeta rise, low betaCTF or C99 expression decreased gamma-secretase inhibitor potency. This "potency shift" may be explained by the relatively high enzyme to substrate ratio under conditions of low substrate because increased concentrations of inhibitor would be necessary to affect substrate turnover. Consistent with this hypothesis, gamma-secretase inhibitor radioligand occupancy studies showed that a high level of occupancy was correlated with inhibition of Abeta under conditions of low substrate expression. The Abeta rise was also observed in rat brain after dosing with the gamma-secretase inhibitor BMS-299897. The Abeta rise and potency shift are therefore relevant factors in the development of gamma-secretase inhibitors and can be evaluated using appropriate choices of animal and cell culture models. Hypothetical mechanisms for the Abeta rise, including the "incomplete processing" and endocytic models, are discussed.

    The Journal of biological chemistry 2008;283;34;22992-3003

  • Long-term prevention of Alzheimer's disease-like behavioral deficits in PDAPP mice carrying a mutation in Asp664.

    Galvan V, Zhang J, Gorostiza OF, Banwait S, Huang W, Ataie M, Tang H and Bredesen DE

    Buck Institute for Age Research, 8001 Redwood Blvd., Novato, CA 94945, USA. vgalvan@buckinstitute.org

    The deficits of Alzheimer's disease (AD) are believed to result, at least in part, from neurotoxicity of beta-amyloid (Abeta), a set of 38-43 amino acid fragments derived from the beta-amyloid precursor protein (APP). In addition, APP generates the APP-C31 and Jcasp toxic fragments intracellularly by cleavage at Asp664. We reported that mutation of Asp664 to Ala in a FAD-human APP transgene prevented AD-like deficits but did not affect Abeta production or deposition in PDAPP mice, arguing that D664A plays a crucial role in the generation of AD-like deficits. Whether D664A simply delays or completely prevents AD-like deficits, however, remained undefined. To address this question, we performed behavioral studies longitudinally on a pretrained mouse cohort at 9 and 13 months (mo) of age. While behavioral deficits were present in PDAPP mice, performance of Tg PDAPP(D664A) mice was not significantly different from non-Tg littermates' across all ages tested. Moreover, aberrant patterns in non-cognitive components of behavior in PDAPP mice were ameliorated in PDAPP(D664A) animals as well. A trend towards poorer retention at 9 mo and poorer learning at 13 mo that did not reach statistical significance was observed in PDAPP(D664A) mice. These results support and extend recent studies showing that cleavage of APP at Asp664 (or protein-protein interactions dependent on Asp664) is a crucial event in the generation of AD-like deficits in PDAPP mice. Our results thus further demonstrate that the D664A mutation either completely precludes, or markedly delays (beyond 13 mo) the appearance of AD-like deficits in this mouse model of AD.

    Funded by: NINDS NIH HHS: R01 NS045093, R01 NS045093-01, R01 NS045093-02, R01 NS045093-03, R01 NS045093-04, R01 NS045093-05

    Behavioural brain research 2008;191;2;246-55

  • Swedish amyloid precursor protein mutation increases cell cycle-related proteins in vitro and in vivo.

    Ahn KW, Joo Y, Choi Y, Kim M, Lee SH, Cha SH, Suh YH and Kim HS

    Department of Pharmacology, College of Medicine, Seoul National University, Seoul, Korea.

    Reactivation of the cell cycle, including DNA replication, might play a major role in Alzheimer's disease. In this study, we report that the expressions of Swedish double mutation of amyloid precursor protein (Swe-APP) or of the APP intracellular domain (AICD) into nerve growth factor (NGF)-differentiated PC12 cells or rat primary cortical neurons increased mRNA and protein levels of cyclin D1 and cyclin B1. Treatment with lithium chloride (a glycogen synthase kinase-3beta inhibitor) down-regulated cyclin B1 induced by Swe-APP expression but up-regulated cyclin D1 expression induced by Swe-APP, suggesting that glycogen synthase kinase-3beta activity is involved in these expression changes of cyclins D1 and B1. Swe-APP, which is a prevailing cause of familial Alzheimer's disease, is well known to increase amyloid beta peptide production both in vitro and in vivo, but the underlying molecular means whereby it leads to the pathogenesis of AD remains unknown. The finding that cyclin D1 and B1 expressions were up-regulated by Swe-APP in in vitro cultured cells was substantiated in the brain tissues of Tg2576 mice, which harbor the Swe-APP mutation. These results suggest that some disturbances in cell cycle regulation may be involved in Swe-APP or AICD-induced neurodegeneration and that these contribute to the pathogenesis of AD.

    Journal of neuroscience research 2008;86;11;2476-87

  • CSF beta-amyloid 1-42 and tau in Tunisian patients with Alzheimer's disease: the effect of APOE epsilon4 allele.

    Smach MA, Charfeddine B, Lammouchi T, Harrabi I, Ben Othman L, Dridi H, Bennamou S and Limem K

    Department of Biochemistry, Faculty of Medicine of Sousse, Tunisia. dalifms@yahoo.fr

    Alzheimer's disease (AD) is the leading cause of dementia. Currently, no definitive diagnostic test for AD exists. An accurate, convenient and objective test to detect AD is urgently needed for efficient drug development and effective clinical use of emerging therapies. The aim of the present work is to investigate the usefulness of cerebrospinal fluid (CSF) beta-amyloid protein (Abeta1-42) and total tau protein (t-tau) analyses in the diagnosis of AD and whether apolipoprotein E (ApoE) epsilon4 allele is a factor for AD affecting Tunisian people. Abeta1-42 and t-tau levels were measured in CSF from AD patients (n=73), non-Alzheimer dementia (nAD, n=35) and healthy controls (HC, n=38) by sandwich enzyme-linked immunosorbent assay. Abeta1-42 levels were decreased and t-tau increased in AD patients. The combination of Abeta1-42 and t-tau at baseline yielded a sensitivity of 87.4% for detection of AD. The specificities were 97.3% for controls and 82.7% for other dementia. The ApoE epsilon4 allele frequency (29.5%) was significantly higher in the AD patients than in the nAD patients (17.1%) or in the control groups (9.5%). AD patients carrying ApoE epsilon4 allele had lower Abeta1-42 (p<0.001) levels than those without a epsilon4 allele. The combination of t-tau and Abeta1-42 is a robust and reliable assay that may be useful in discriminating cases at risk for AD such as ApoE epsilon4 allele carriers from nAD patients or from age-matched control subjects.

    Neuroscience letters 2008;440;2;145-9

  • Effects of familial Alzheimer's disease mutations on the folding nucleation of the amyloid beta-protein.

    Krone MG, Baumketner A, Bernstein SL, Wyttenbach T, Lazo ND, Teplow DB, Bowers MT and Shea JE

    Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106-9510, USA.

    The effect of single amino acid substitutions associated with the Italian (E22K), Arctic (E22G), Dutch (E22Q) and Iowa (D23N) familial forms of Alzheimer's disease and cerebral amyloid angiopathy on the structure of the 21-30 fragment of the Alzheimer amyloid beta-protein (Abeta) is investigated by replica-exchange molecular dynamics simulations. The 21-30 segment has been shown in our earlier work to adopt a bend structure in solution that may serve as the folding nucleation site for Abeta. Our simulations reveal that the 24-28 bend motif is retained in all E22 mutants, suggesting that mutations involving residue E22 may not affect the structure of the folding nucleation site of Abeta. Enhanced aggregation in Abeta with familial Alzheimer's disease substitutions may result from the depletion of the E22-K28 salt bridge, which destabilizes the bend structure. Alternately, the E22 mutations may affect longer-range interactions outside the 21-30 segment that can impact the aggregation of Abeta. Substituting at residue D23, on the other hand, leads to the formation of a turn rather than a bend motif, implying that in contrast to E22 mutants, the D23N mutant may affect monomer Abeta folding and subsequent aggregation. Our simulations suggest that the mechanisms by which E22 and D23 mutations affect the folding and aggregation of Abeta are fundamentally different.

    Funded by: NIA NIH HHS: AG027818, P01 AG027818-010003; NIGMS NIH HHS: GM083600

    Journal of molecular biology 2008;381;1;221-8

  • Increased AICD generation does not result in increased nuclear translocation or activation of target gene transcription.

    Waldron E, Isbert S, Kern A, Jaeger S, Martin AM, Hébert SS, Behl C, Weggen S, De Strooper B and Pietrzik CU

    Institute of Physiological Chemistry and Pathobiochemistry, Molecular Neurodegeneration, Johannes Gutenberg-University Mainz, 55099 Mainz, Germany.

    A sequence of amyloid precursor protein (APP) cleavages culminates in the sequential release of the APP intracellular domain (AICD) and the amyloid beta peptide (Abeta) and/or p3 fragment. One of the environmental factors favouring the accumulation of AICD appears to be a rise in intracellular pH. Here we further identified the metabolism and subcellular localization of artificially expressed constructs under such conditions. We also co-examined the mechanistic lead up to the AICD accumulation and explored possible significances for its increased expression. We found that most of the AICD generated under pH neutralized conditions is likely cleaved from C83. While the AICD surplus was unable to further activate transcription of a luciferase reporter via a Gal4-DNA-binding domain, it failed entirely via the endogenous promoter regions of proposed target genes, APP and KAI1. The lack of a specific transactivation potential was also demonstrated by the unchanged levels of target gene mRNA. However, rather than translocating to the nucleus, the AICD surplus remains membrane tethered or free in the cytosol where it interacts with Fe65. Therefore we provide strong evidence that an increase in AICD generation does not directly promote gene activation of previously proposed target genes.

    Experimental cell research 2008;314;13;2419-33

  • Amyloid-beta protein dimers isolated directly from Alzheimer's brains impair synaptic plasticity and memory.

    Shankar GM, Li S, Mehta TH, Garcia-Munoz A, Shepardson NE, Smith I, Brett FM, Farrell MA, Rowan MJ, Lemere CA, Regan CM, Walsh DM, Sabatini BL and Selkoe DJ

    Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, USA.

    Alzheimer's disease constitutes a rising threat to public health. Despite extensive research in cellular and animal models, identifying the pathogenic agent present in the human brain and showing that it confers key features of Alzheimer's disease has not been achieved. We extracted soluble amyloid-beta protein (Abeta) oligomers directly from the cerebral cortex of subjects with Alzheimer's disease. The oligomers potently inhibited long-term potentiation (LTP), enhanced long-term depression (LTD) and reduced dendritic spine density in normal rodent hippocampus. Soluble Abeta from Alzheimer's disease brain also disrupted the memory of a learned behavior in normal rats. These various effects were specifically attributable to Abeta dimers. Mechanistically, metabotropic glutamate receptors were required for the LTD enhancement, and N-methyl D-aspartate receptors were required for the spine loss. Co-administering antibodies to the Abeta N-terminus prevented the LTP and LTD deficits, whereas antibodies to the midregion or C-terminus were less effective. Insoluble amyloid plaque cores from Alzheimer's disease cortex did not impair LTP unless they were first solubilized to release Abeta dimers, suggesting that plaque cores are largely inactive but sequester Abeta dimers that are synaptotoxic. We conclude that soluble Abeta oligomers extracted from Alzheimer's disease brains potently impair synapse structure and function and that dimers are the smallest synaptotoxic species.

    Funded by: NIA NIH HHS: AG R01 027443, R01 AG027443, R01 AG027443-01, R01 AG027443-02, R01 AG027443-03, R01 AG027443-04; NINDS NIH HHS: R01 NS046579, R01 NS046579-06A1; Wellcome Trust: 067660

    Nature medicine 2008;14;8;837-42

  • Cholesterol potentiates beta-amyloid-induced toxicity in human neuroblastoma cells: involvement of oxidative stress.

    Ferrera P, Mercado-Gómez O, Silva-Aguilar M, Valverde M and Arias C

    Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, AP 70-228, 04510, Mexico, DF, Mexico.

    Alterations in brain cholesterol concentration and metabolism seem to be involved in Alzheimer's disease (AD). In fact, several experimental studies have reported that modification of cholesterol content can influence the expression of the amyloid precursor protein (APP) and amyloid beta peptide (Abeta) production. However, it remains to be determined if changes in neuronal cholesterol content may influence the toxicity of Abeta peptides and the mechanism involved. Aged mice, AD patients and neurons exposed to Abeta, show a significant increase in membrane-associated oxidative stress. Since Abeta is able to promote oxidative stress directly by catalytically producing H(2)O(2) from cholesterol, the present work analyzed the effect of high cholesterol incorporated into human neuroblastoma cells in Abeta-mediated neurotoxicity and the role of reactive oxygen species (ROS) generation. Neuronal viability was studied also in the presence of 24S-hydroxycholesterol, the main cholesterol metabolite in brain, as well as the potential protective role of the lipophilic statin, lovastatin.

    Neurochemical research 2008;33;8;1509-17

  • Evidence for a role of the amyloid precursor protein in thyroid carcinogenesis.

    Krause K, Karger S, Sheu SY, Aigner T, Kursawe R, Gimm O, Schmid KW, Dralle H and Fuhrer D

    Division of Endocrinology, Department of Internal Medicine, University of Leipzig, Ph.-Rosenthal-Str. 27, D-04103 Leipzig, Germany.

    We have recently found an increased expression of amyloid precursor protein (APP) in cold thyroid nodules that are difficult to classify as a truly benign thyroid neoplasm or a lesion with the potential for further dedifferentiation. Since differences in APP activity have been found in other human cancers, we asked whether thyroid carcinogenesis might be associated with an altered APP expression and function. APP regulation was studied in vitro in differentiated (FRTL-5) and dedifferentiated follicular thyroid carcinomas (FTC-133) thyroid cells after specific inhibition or activation of the cAMP-PKA, the PI3K/AKT or the protein kinase c (PKC) cascades. In vivo analysis of APP expression and downstream signalling was performed in benign and malignant thyroid tissues. We found that upregulation of APP expression and sAPP secretion is induced by TSH in differentiated thyroid cells and by insulin in thyroid cancer cells. PKC is a strong activator of APP cleavage and in FTC-133 confers prolonged release of the APP ectodomain. FTC-133 but not FRTL-5 cells show a prominent cell surface expression of the APP ectodomain, which has been suggested to function as an autocrine growth factor. Thyroid cancers are characterized by APP upregulation, increased membrane targeting of the APP ectodomain and significantly increased mRNA levels of the APP scaffold proteins JIP1, ShcA and Fe65.

    The Journal of endocrinology 2008;198;2;291-9

  • Protein expression of BACE1, BACE2 and APP in Down syndrome brains.

    Cheon MS, Dierssen M, Kim SH and Lubec G

    Department of Pediatrics, Medical University of Vienna, Vienna, Austria.

    Down syndrome (DS) is the most common human chromosomal abnormality caused by an extra copy of chromosome 21. The phenotype of DS is thought to result from overexpression of a gene or genes located on the triplicated chromosome or chromosome region. Several reports have shown that the neuropathology of DS comprises developmental abnormalities and Alzheimer-like lesions such as senile plaques. A key component of senile plaques is amyloid beta-peptide which is generated from the amyloid precursor protein (APP) by sequential action of beta-secretases (BACE1 and BACE2) and gamma-secretase. While BACE1 maps to chromosome 11, APP and BACE2 are located on chromosome 21. To challenge the gene dosage effect and gain insight into the expressional relation between beta-secretases and APP in DS brain, we evaluated protein expression levels of BACE1, BACE2 and APP in fetal and adult DS brain compared to controls. In fetal brain, protein expression levels of BACE2 and APP were comparable between DS and controls. BACE1 was increased, but did not reach statistical significance. In adult brain, BACE1 and BACE2 were comparable between DS and controls, but APP was significantly increased. We conclude that APP overexpression seems to be absent during the development of DS brain up to 18-19 weeks of gestational age. However, its overexpression in adult DS brain could lead to disturbance of normal function of APP contributing to neurodegeneration. Comparable expression of BACE1 and BACE2 speaks against the hypothesis that increased beta-secretase results in (or even underlies) increased production of amyloidogenic A beta fragments. Furthermore, current data indicate that the DS phenotype cannot be fully explained by simple gene dosage effect.

    Amino acids 2008;35;2;339-43

  • Amyloid beta-peptide levels in laser capture microdissected cornu ammonis 1 pyramidal neurons of Alzheimer's brain.

    Aoki M, Volkmann I, Tjernberg LO, Winblad B and Bogdanovic N

    Karolinska Institutet and Sumitomo Pharmaceuticals Alzheimer Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Novum plan 5, Huddinge, Sweden.

    Deposition of the amyloid beta-peptide (Abeta) is a pathophysiological event associated with Alzheimer's disease. Although much is known about the molecular composition of extracellular Abeta deposits, the role of the intracellular pool of Abeta is not fully understood. We investigated whether Abeta levels are increased in cornu ammonis 1 pyramidal neurons of Alzheimer's disease hippocampus, using laser capture microdissection to isolate the neurons and enzyme-linked immunosorbent assay for quantification. Our results showed increased Abeta42 levels and an elevated Abeta42/Abeta40 ratio in neurons from sporadic as well as from familial cases of Alzheimer's disease, whereas Abeta40 levels remain unchanged between the cases and controls. We speculate that intracellular accumulation of Abeta42 increase vulnerability of cornu ammonis 1 pyramidal neurons in Alzheimer's disease.

    Neuroreport 2008;19;11;1085-9

  • Evidence that CD147 modulation of beta-amyloid (Abeta) levels is mediated by extracellular degradation of secreted Abeta.

    Vetrivel KS, Zhang X, Meckler X, Cheng H, Lee S, Gong P, Lopes KO, Chen Y, Iwata N, Yin KJ, Lee JM, Parent AT, Saido TC, Li YM, Sisodia SS and Thinakaran G

    Department of Neurobiology and Neurology, The University of Chicago, Chicago, Illinois 60637, USA.

    Cerebral deposition of beta-amyloid (Abeta) peptides is a pathological hallmark of Alzheimer disease. Intramembranous proteolysis of amyloid precursor protein by a multiprotein gamma-secretase complex generates Abeta. Previously, it was reported that CD147, a glycoprotein that stimulates production of matrix metalloproteinases (MMPs), is a subunit of gamma-secretase and that the levels of secreted Abeta inversely correlate with CD147 expression. Here, we show that the levels and localization of CD147 in fibroblasts, as well as postnatal expression and distribution in brain, are distinct from those of integral gamma-secretase subunits. Notably, we show that although depletion of CD147 increased extracellular Abeta levels in intact cells, membranes isolated from CD147-depleted cells failed to elevate Abeta production in an in vitro gamma-secretase assay. Consistent with an extracellular source that modulates Abeta metabolism, synthetic Abeta was degraded more rapidly in the conditioned medium of cells overexpressing CD147. Moreover, modulation of CD147 expression had no effect on epsilon-site cleavage of amyloid precursor protein and Notch1 receptor. Collectively, our results demonstrate that CD147 modulates Abeta levels not by regulating gamma-secretase activity, but by stimulating extracellular degradation of Abeta. In view of the known function of CD147 in MMP production, we postulate that CD147 expression influences Abeta levels by an indirect mechanism involving MMPs that can degrade extracellular Abeta.

    Funded by: NIA NIH HHS: AG019070, AG021495, AG026660, R01 AG019070, R01 AG021495; NINDS NIH HHS: P01 NS032636, P01 NS032636-139001, R01 NS048283, R01 NS048283-03, R01 NS048283-04

    The Journal of biological chemistry 2008;283;28;19489-98

  • Regulation of FE65 nuclear translocation and function by amyloid beta-protein precursor in osmotically stressed cells.

    Nakaya T, Kawai T and Suzuki T

    Laboratory of Neuroscience, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-12 Nishi-6, Kita-ku, Sapporo 060-0812, Japan.

    FE65, a neural adaptor protein, interacts with amyloid beta-protein precursor (APP) and is known to regulate amyloid beta generation from APP. FE65 also associates with nuclear proteins; however, its physiological function in the nucleus remains unclear. A fixed population of cytoplasmic FE65 is tethered to membranes by binding APP. This membrane-tethered FE65 is liberated from membranes by APP phosphorylation, which is facilitated by a stress-activated protein kinase in sorbitol-treated cells. Here we show that liberated FE65, which is distinct from "virgin" FE65 in the cytoplasm, translocates into the nucleus and accumulates in the nuclear matrix forming a patched structure. Targeting of FE65 into the nuclear matrix was suppressed by the APP intracellular domain fragment, which is generated by consecutive cleavages of APP. Thus, nuclear translocation of FE65 is under the regulation of APP. In the nucleus, FE65 induced gammaH2AX, which plays an important role in DNA repair as a cellular response by stress-damaged cells. These observations suggest that APP-regulated FE65 plays an important role in the early stress response of cells and that FE65 deregulated from APP induces apoptosis.

    The Journal of biological chemistry 2008;283;27;19119-31

  • Amyloid precursor protein expression is upregulated in adipocytes in obesity.

    Lee YH, Tharp WG, Maple RL, Nair S, Permana PA and Pratley RE

    Diabetes and Metabolism Translational Medicine Unit, University of Vermont College of Medicine, Burlington, Vermont, USA.

    The aim of this study was to determine whether amyloid precursor protein (APP) is expressed in human adipose tissue, dysregulated in obesity, and related to insulin resistance and inflammation. APP expression was examined by microarray expression profiling of subcutaneous abdominal adipocytes (SAC) and cultured preadipocytes from obese and nonobese subjects. Quantitative real-time PCR (QPCR) was performed to confirm differences in APP expression in SAC and to compare APP expression levels in adipose tissue, adipocytes, and stromal vascular cells (SVCs) from subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) specimens. Adipose tissue samples were also examined by western blot and immunofluorescence confocal microscopy. Microarray studies demonstrated that APP mRNA expression levels were higher in SAC (approximately 2.5-fold) and preadipocytes (approximately 1.4) from obese subjects. Real-time PCR confirmed increased APP expression in SAC in a separate group of obese compared with nonobese subjects (P=0.02). APP expression correlated to in vivo indices of insulin resistance independently of BMI and with the expression of proinflammatory genes, such as monocyte chemoattractant protein-1 (MCP-1) (R=0.62, P=0.004), macrophage inflammatory protein-1alpha (MIP-1alpha) (R=0.60, P=0.005), and interleukin-6 (IL-6) (R=0.71, P=0.0005). Full-length APP protein was detected in adipocytes by western blotting and APP and its cleavage peptides, Abeta40 and Abeta42, were observed in SAT and VAT by immunofluorescence confocal microscopy. In summary, APP is highly expressed in adipose tissue, upregulated in obesity, and expression levels correlate with insulin resistance and adipocyte cytokine expression levels. These data suggest a possible role for APP and/or Abeta in the development of obesity-related insulin resistance and adipose tissue inflammation.

    Funded by: NCRR NIH HHS: M01 RR000109

    Obesity (Silver Spring, Md.) 2008;16;7;1493-500

  • Increased total-Tau levels in cerebrospinal fluid of pediatric hydrocephalus and brain tumor patients.

    de Bont JM, Vanderstichele H, Reddingius RE, Pieters R and van Gool SW

    Erasmus MC, University Medical Center, Sophia Children's Hospital, Rotterdam, The Netherlands. j.debont@erasmusmc.nl

    Total Tau (t-Tau), hyperphosphorylated Tau (p-Tau(181P)) and beta-amyloid(1-42) in cerebrospinal fluid (CSF) have shown to be markers of neuronal and axonal degeneration in various neurological and neurodegenerative diseases. The aim of this study was to evaluate the influence of the presence of a brain tumor and hydrocephalus on t-Tau, p-Tau(181P) and beta-amyloid(1-42) levels in CSF of pediatric patients. t-Tau, p-Tau(181P) and beta-amyloid(1-42) levels were simultaneously quantified by xMAP technology in 22 lumbar and 15 ventricular CSF samples from newly diagnosed pediatric brain tumor patients and 39 lumbar and 12 ventricular CSF samples from pediatric patients without a brain tumor. t-Tau, p-Tau(181P) and beta-amyloid(1-42) levels in both lumbar and ventricular CSF were not significantly correlated with age. t-Tau levels in lumbar CSF were elevated in brain tumor patients, being especially high in medulloblastoma patients. Lumbar CSF p-Tau(181P) levels were lower in brain tumor patients compared to normal controls. Ventricular levels of t-Tau, p-Tau(181P) and beta-amyloid(1-42) were not significantly different between the brain tumor patients and non-tumor patients, but t-Tau levels were significantly increased in patients with radiological signs of hydrocephalus. Two patients with an infected ventriculo-peritoneal drain also had high CSF t-Tau levels. In conclusion, high t-Tau levels in CSF are found in pediatric patients with a brain tumor, patients with hydrocephalus and patients with a serious CNS infection, reflecting neuronal and axonal damage. Ongoing studies should determine whether these neurodegenerative markers in CSF can be used to monitor neuronal and axonal degeneration in these patients during therapy and long-term follow up.

    European journal of paediatric neurology : EJPN : official journal of the European Paediatric Neurology Society 2008;12;4;334-41

  • Plasma lipoprotein beta-amyloid in subjects with Alzheimer's disease or mild cognitive impairment.

    Mamo JC, Jian L, James AP, Flicker L, Esselmann H and Wiltfang J

    Division of Health Sciences, Curtin University of Technology and ATN Centre for Metabolic Health and Fitness. J.Mamo@Curtin.edu.au

    Background: Plasma amyloid beta-peptide (Abeta) can compromise the blood-brain barrier, contributing to cerebrovascular alterations and amyloid angiopathy in Alzheimer's disease (AD). The objectives of this study were to investigate the distribution of lipoprotein-bound plasma-Abeta isoforms.

    Methods: This involved a case-control study of subjects with AD or amnestic mild cognitive impairment (MCI) versus controls. Lipoprotein Abeta distribution was determined in fasted plasma. For assessment of chylomicron homeostasis in the postabsorptive state, subjects were bled 4 h after a low-fat meal. The main outcome measures were plasma lipoprotein Abeta isoform distribution and lipid homeostasis.

    Results: We found the majority of plasma Abeta to be associated with triglyceride-rich lipoproteins (TRLs) encompassing chylomicrons, VLDL and IDL. For all lipoprotein groups, Abeta1-40 was the predominant isoform, accounting for approximately 50% of the total. Thereafter, equivalent amounts of the isoforms 1-42, 2-40, 1-38, 1-37 and 1-39 were found. Abeta1-37, Abeta1-38 and Abeta2-40 isoforms were significantly enriched within the TRL fraction of AD/MCI subjects and similar trends were observed for isoforms Abeta1-39, Abeta1-40 and Abeta1-42. Lipoprotein-Abeta was inversely associated with plasma total- and LDL cholesterol. AD/MCI subjects were not dyslipidaemic, however, there was evidence of accumulation of chylomicrons in the postabsorptive state.

    Conclusions: Our data show that Abeta was found to be associated with plasma lipoproteins, especially those enriched with triglyceride. We find that Abeta may be increased in normolipidaemic AD subjects, commensurate with possible disturbances in postprandial lipoprotein homeostasis.

    Annals of clinical biochemistry 2008;45;Pt 4;395-403

  • A polymorphism in CALHM1 influences Ca2+ homeostasis, Abeta levels, and Alzheimer's disease risk.

    Dreses-Werringloer U, Lambert JC, Vingtdeux V, Zhao H, Vais H, Siebert A, Jain A, Koppel J, Rovelet-Lecrux A, Hannequin D, Pasquier F, Galimberti D, Scarpini E, Mann D, Lendon C, Campion D, Amouyel P, Davies P, Foskett JK, Campagne F and Marambaud P

    Litwin-Zucker Research Center for the Study of Alzheimer's Disease, The Feinstein Institute for Medical Research, North Shore-LIJ, Manhasset, NY 11030, USA.

    Alzheimer's disease (AD) is a genetically heterogeneous disorder characterized by early hippocampal atrophy and cerebral amyloid-beta (Abeta) peptide deposition. Using TissueInfo to screen for genes preferentially expressed in the hippocampus and located in AD linkage regions, we identified a gene on 10q24.33 that we call CALHM1. We show that CALHM1 encodes a multipass transmembrane glycoprotein that controls cytosolic Ca(2+) concentrations and Abeta levels. CALHM1 homomultimerizes, shares strong sequence similarities with the selectivity filter of the NMDA receptor, and generates a large Ca(2+) conductance across the plasma membrane. Importantly, we determined that the CALHM1 P86L polymorphism (rs2986017) is significantly associated with AD in independent case-control studies of 3404 participants (allele-specific OR = 1.44, p = 2 x 10(-10)). We further found that the P86L polymorphism increases Abeta levels by interfering with CALHM1-mediated Ca(2+) permeability. We propose that CALHM1 encodes an essential component of a previously uncharacterized cerebral Ca(2+) channel that controls Abeta levels and susceptibility to late-onset AD.

    Funded by: NIMH NIH HHS: R01 MH059937, R01 MH059937-09

    Cell 2008;133;7;1149-61

  • Secreted APP regulates the function of full-length APP in neurite outgrowth through interaction with integrin beta1.

    Young-Pearse TL, Chen AC, Chang R, Marquez C and Selkoe DJ

    Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. tyoung@rics.bwh.harvard.edu

    Background: Beta-amyloid precursor protein (APP) has been reported to play a role in the outgrowth of neurites from cultured neurons. Both cell-surface APP and its soluble, ectodomain cleavage product (APPs-alpha) have been implicated in regulating the length and branching of neurites in a variety of assays, but the mechanism by which APP performs this function is not understood.

    Results: Here, we report that APP is required for proper neurite outgrowth in a cell autonomous manner, both in vitro and in vivo. Neurons that lack APP undergo elongation of their longest neurite. Deletion of APLP1 or APLP2, homologues of APP, likewise stimulates neurite lengthening. Intriguingly, wild-type neurons exposed to APPs-alpha, the principal cleavage product of APP, also undergo neurite elongation. However, APPs-alpha is unable to stimulate neurite elongation in the absence of cellular APP expression. The outgrowth-enhancing effects of both APPs-alpha and the deletion of APP are inhibited by blocking antibodies to Integrin beta1 (Itgbeta1). Moreover, full length APP interacts biochemically with Itgbeta1, and APPs-alpha can interfere with this binding.

    Conclusion: Our findings indicate that APPs-alpha regulates the function of APP in neurite outgrowth via the novel mechanism of competing with the binding of APP to Itgbeta1.

    Funded by: NIA NIH HHS: R01 AG006173, R0I AG06173; NINDS NIH HHS: F32 NS053320, F32 NS053320-01A1

    Neural development 2008;3;15

  • The catalytic domain of insulin-degrading enzyme forms a denaturant-resistant complex with amyloid beta peptide: implications for Alzheimer disease pathogenesis.

    Llovera RE, de Tullio M, Alonso LG, Leissring MA, Kaufman SB, Roher AE, de Prat Gay G, Morelli L and Castaño EM

    Fundación Instituto Leloir-Instituto de Investigaciones Bioquímicas de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 435 Av. Patricias Argentinas, Ciudad de Buenos Aires C1405BWE, Argentina.

    Insulin-degrading enzyme (IDE) is central to the turnover of insulin and degrades amyloid beta (Abeta) in the mammalian brain. Biochemical and genetic data support the notion that IDE may play a role in late onset Alzheimer disease (AD), and recent studies suggest an association between AD and diabetes mellitus type 2. Here we show that a natively folded recombinant IDE was capable of forming a stable complex with Abeta that resisted dissociation after treatment with strong denaturants. This interaction was also observed with rat brain IDE and detected in an SDS-soluble fraction from AD cortical tissue. Abeta sequence 17-27, known to be crucial in amyloid assembly, was sufficient to form a stable complex with IDE. Monomeric as opposed to aggregated Abeta was competent to associate irreversibly with IDE following a very slow kinetics (t(1/2) approximately 45 min). Partial denaturation of IDE as well as preincubation with a 10-fold molar excess of insulin prevented complex formation, suggesting that the irreversible interaction of Abeta takes place with at least part of the substrate binding site of the protease. Limited proteolysis showed that Abeta remained bound to a approximately 25-kDa N-terminal fragment of IDE in an SDS-resistant manner. Mass spectrometry after in gel digestion of the IDE .Abeta complex showed that peptides derived from the region that includes the catalytic site of IDE were recovered with Abeta. Taken together, these results are suggestive of an unprecedented mechanism of conformation-dependent substrate binding that may perturb Abeta clearance, insulin turnover, and promote AD pathogenesis.

    The Journal of biological chemistry 2008;283;25;17039-48

  • A common beta-sheet architecture underlies in vitro and in vivo beta2-microglobulin amyloid fibrils.

    Jahn TR, Tennent GA and Radford SE

    Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.

    Misfolding and aggregation of normally soluble proteins into amyloid fibrils and their deposition and accumulation underlies a variety of clinically significant diseases. Fibrillar aggregates with amyloid-like properties can also be generated in vitro from pure proteins and peptides, including those not known to be associated with amyloidosis. Whereas biophysical studies of amyloid-like fibrils formed in vitro have provided important insights into the molecular mechanisms of amyloid generation and the structural properties of the fibrils formed, amyloidogenic proteins are typically exposed to mild or more extreme denaturing conditions to induce rapid fibril formation in vitro. Whether the structure of the resulting assemblies is representative of their natural in vivo counterparts, thus, remains a fundamental unresolved issue. Here we show using Fourier transform infrared spectroscopy that amyloid-like fibrils formed in vitro from natively folded or unfolded beta(2)-microglobulin (the protein associated with dialysis-related amyloidosis) adopt an identical beta-sheet architecture. The same beta-strand signature is observed whether fibril formation in vitro occurs spontaneously or from seeded reactions. Comparison of these spectra with those of amyloid fibrils extracted from patients with dialysis-related amyloidosis revealed an identical amide I' absorbance maximum, suggestive of a characteristic and conserved amyloid fold. Our results endorse the relevance of biophysical studies for the investigation of the molecular mechanisms of beta(2)-microglobulin fibrillogenesis, knowledge about which may inform understanding of the pathobiology of this protein.

    Funded by: Wellcome Trust

    The Journal of biological chemistry 2008;283;25;17279-86

  • Independent generation of Abeta42 and Abeta38 peptide species by gamma-secretase.

    Czirr E, Cottrell BA, Leuchtenberger S, Kukar T, Ladd TB, Esselmann H, Paul S, Schubenel R, Torpey JW, Pietrzik CU, Golde TE, Wiltfang J, Baumann K, Koo EH and Weggen S

    Molecular Neuropathology Group, Department of Neuropathology, Heinrich Heine-University, D-40225 Duesseldorf, Germany.

    Proteolytic processing of the amyloid precursor protein by beta- and gamma-secretase generates the amyloid-beta (Abeta) peptides, which are principal drug targets in Alzheimer disease therapeutics. gamma-Secretase has imprecise cleavage specificity and generates the most abundant Abeta40 and Abeta42 species together with longer and shorter peptides such as Abeta38. Several mechanisms could explain the production of multiple Abeta peptides by gamma-secretase, including sequential processing of longer into shorter Abeta peptides. A novel class of gamma-secretase modulators (GSMs) that includes some non-steroidal anti-inflammatory drugs has been shown to selectively lower Abeta42 levels without a change in Abeta40 levels. A signature of GSMs is the concomitant increase in shorter Abeta peptides, such as Abeta38, leading to the suggestion that generation of Abeta42 and Abeta38 peptide species by gamma-secretase is coordinately regulated. However, no evidence for or against such a precursor-product relationship has been provided. We have previously shown that stable overexpression of aggressive presenilin-1 (PS1) mutations associated with early-onset familial Alzheimer disease attenuated the cellular response to GSMs, resulting in greatly diminished Abeta42 reductions as compared with wild type PS1. We have now used this model system to investigate whether Abeta38 production would be similarly affected indicating coupled generation of Abeta42 and Abeta38 peptides. Surprisingly, treatment with the GSM sulindac sulfide increased Abeta38 production to similar levels in four different PS1 mutant cell lines as compared with wild type PS1 cells. This was confirmed with the structurally divergent GSMs ibuprofen and indomethacin. Mass spectrometry analysis and high resolution urea gel electrophoresis further demonstrated that sulindac sulfide did not induce detectable compensatory changes in levels of other Abeta peptide species. These data provide evidence that Abeta42 and Abeta38 species can be independently generated by gamma-secretase and argue against a precursor-product relationship between these peptides.

    The Journal of biological chemistry 2008;283;25;17049-54

  • Structure of alpha-helical membrane-bound human islet amyloid polypeptide and its implications for membrane-mediated misfolding.

    Apostolidou M, Jayasinghe SA and Langen R

    Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.

    Human islet amyloid polypeptide (hIAPP) misfolding is thought to play an important role in the pathogenesis of type II diabetes mellitus. It has recently been shown that membranes can catalyze the misfolding of hIAPP via an alpha-helical intermediate of unknown structure. To better understand the mechanism of membrane-mediated misfolding, we used site-directed spin labeling and EPR spectroscopy to generate a three-dimensional structural model of this membrane-bound form. We find that hIAPP forms a single alpha-helix encompassing residues 9-22. The helix is flanked by N- and C-terminal regions that do not take up a clearly detectable secondary structure and are less ordered. Residues 21 and 22 are located in a transitional region between the alpha-helical structure and C terminus and exhibit significant mobility. The alpha-helical structure presented here has important implications for membrane-mediated aggregation. Anchoring hIAPP to the membrane not only increases the local concentration but also reduces the encounter between peptides to essentially a two-dimensional process. It is significant to note that the alpha-helical membrane-bound form leaves much of an important amyloidogenic region of hIAPP (residues 20-29) exposed for misfolding. Misfolding of this and other regions is likely further aided by the low dielectric environment near the membrane that is known to promote secondary structure formation. Based upon these considerations, a structural model for membrane-mediated aggregation is discussed.

    Funded by: NIA NIH HHS: AG027936

    The Journal of biological chemistry 2008;283;25;17205-10

  • TMP21 regulates Abeta production but does not affect caspase-3, p53, and neprilysin.

    Dolcini V, Dunys J, Sevalle J, Chen F, Guillot-Sestier MV, St George-Hyslop P, Fraser PE and Checler F

    Institut de Pharmacologie Moléculaire et Cellulaire, UMR 6097, Centre National de la Recherche Scientifique-Université Nice-Sophia-Antipolis, Equipe labellisée Fondation pour la Recherche Médicale, 660 Route des Lucioles, 06560 Valbonne, France.

    The presenilin (PS)-dependent gamma-secretase activity refers to a high molecular mass-complex including, besides PS1 or PS2, three other proteins recently identified, namely nicastrin, Aph-1, and Pen-2. This proteolytic complex has been shown to contribute to both gamma- and epsilon-cleavages of the beta-amyloid precursor protein (betaAPP), thereby generating beta-amyloid peptides (Abeta) and the APP intracellular domain (AICD), respectively. TMP21, a member of the p24 cargo protein family, was recently shown to interact with PS complexes. Interestingly, TMP21 modulates gamma-secretase-mediated Abeta production but does not regulate epsilon-secretase-derived AICD formation [F. Chen, H. Hasegawa, G. Schmitt-ulms, T. Kawarai, C. Bohm, T. Katayama, Y. Gu, N. Sanjo, M. Glista, E. Rogaeva, Y. Wakutami, R. Pardossi-Piquard, X. Ruan, A. Tandon, F. Checler, P. Marambaud, K. Hansen, D. Westaway, P. St. George-Hyslop, P. Fraser, TMP21 is a presenilin complex component that modulates gamma- but not epsilon-secretase activities, Nature 440 (2006) 1208-1212]. Here we investigate the functional incidence of the over-expression or depletion of TMP21 on both intracellular and secreted Abeta recoveries and AICD-associated phenotypes. First we confirm that TMP21 depletion yields increased levels of secreted Abeta40. However, we demonstrate that both staurosporine-stimulated caspase-3 activation, p53 and neprilysin expression and activity were not affected by TMP21 over-expression or depletion. Overall, our functional data further reinforce the view that TMP21 behaves as a regulator of gamma- but not epsilon-cleavages generated by PS-dependent gamma-secretase complex.

    Biochemical and biophysical research communications 2008;371;1;69-74

  • Enzymatic characteristics of I213T mutant presenilin-1/gamma-secretase in cell models and knock-in mouse brains: familial Alzheimer disease-linked mutation impairs gamma-site cleavage of amyloid precursor protein C-terminal fragment beta.

    Shimojo M, Sahara N, Mizoroki T, Funamoto S, Morishima-Kawashima M, Kudo T, Takeda M, Ihara Y, Ichinose H and Takashima A

    Laboratory for Alzheimer's Disease, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan.

    Presenilin (PS)/gamma-secretase-mediated intramembranous proteolysis of amyloid precursor protein produces amyloid beta (Abeta) peptides in which Abeta species of different lengths are generated through multiple cleavages at the gamma-, zeta-, and epsilon-sites. An increased Abeta42/Abeta40 ratio is a common characteristic of most cases of familial Alzheimer disease (FAD)-linked PS mutations. However, the molecular mechanisms underlying amyloid precursor protein proteolysis leading to increased Abeta42/Abeta40 ratios still remain unclear. Here, we report our findings on the enzymatic analysis of gamma-secretase derived from I213T mutant PS1-expressing PS1/PS2-deficient (PS(-/-)) cells and from the brains of I213T mutant PS1 knock-in mice. Kinetics analyses revealed that the FAD mutation reduced de novo Abeta generation, suggesting that mutation impairs the total catalytic rate of gamma-secretase. Analysis of each Abeta species revealed that the FAD mutation specifically reduced Abeta40 levels more drastically than Abeta42 levels, leading to an increased Abeta42/Abeta40 ratio. By contrast, the FAD mutation increased the generation of longer Abeta species such as Abeta43, Abeta45, and >Abeta46. These results were confirmed by analyses of gamma-secretase derived from I213T knock-in mouse brains, in which the reduction of de novo Abeta generation was mutant allele dose-dependent. Our findings clearly indicate that the mechanism underlying the increased Abeta42/Abeta40 ratio observed in cases of FAD mutations is related to the differential inhibition of gamma-site cleavage reactions, in which the reaction producing Abeta40 is subject to more inhibition than that producing Abeta42. Our results also provide novel insight into how enhancing the generation of longer Abetas may contribute to Alzheimer disease onset.

    The Journal of biological chemistry 2008;283;24;16488-96

  • Transglutaminase induces protofibril-like amyloid beta-protein assemblies that are protease-resistant and inhibit long-term potentiation.

    Hartley DM, Zhao C, Speier AC, Woodard GA, Li S, Li Z and Walz T

    Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois 60612, USA. dean_hartley@rush.edu

    An increasing body of evidence suggests that soluble assemblies of amyloid beta-protein (Abeta) play an important role in the initiation of Alzheimer disease (AD). In vitro studies have found that synthetic Abeta can form soluble aggregates through self-assembly, but this process requires Abeta concentrations 100- to 1000-fold greater than physiological levels. Tissue transglutaminase (TGase) has been implicated in neurodegeneration and can cross-link Abeta. Here we show that TGase induces rapid aggregation of Abeta within 0.5-30 min, which was not observed with chemical cross-linkers. Both Abeta40 and Abeta42 are good substrates for TGase but show different aggregation patterns. Guinea pig and human TGase induced similar Abeta aggregation patterns, and oligomerization was observed with Abeta40 concentrations as low as 50 nm. The formed Abeta40 species range from 5 to 6 nm spheres to curvilinear structures of the same width, but up to 100 nm in length, that resemble the previously described self-assembled Abeta protofibrils. TGase-induced Abeta40 assemblies are resistant to a 1-h incubation with either neprilysin or insulin degrading enzyme, whereas the monomer is rapidly degraded by both proteases. In support of these species being pathological, TGase-induced Abeta40 assemblies (100 nm) inhibited long term potentiation recorded in the CA1 region of mouse hippocampus slices. Our data suggest that TGase can contribute to AD by initiating Abeta oligomerization and aggregation at physiological levels, by reducing the clearance of Abeta due to the generation of protease-resistant Abeta species, and by forming Abeta assemblies that inhibit processes involved in memory and learning. Our data suggest that TGase might constitute a specific therapeutic target for slowing or blocking the progression of AD.

    Funded by: NIA NIH HHS: AG19770; NIGMS NIH HHS: P01 GM062580

    The Journal of biological chemistry 2008;283;24;16790-800

  • Upregulation of beta-amyloid precursor protein expression in glioblastoma multiforme.

    Culicchia F, Cui JG, Li YY and Lukiw WJ

    LSU Neuroscience Center and Department of Neurosurgery, Louisiana State University Health Science Center, New Orleans, Louisiana 70112-2272, USA.

    Glioma and glioblastoma multiforme constitute rapidly proliferating glial cell tumors whose pathogenic mechanisms are not well understood. This study examined proinflammatory and neurodegenerative gene expression in five American Tissue Culture Collection glioma and glioblastoma multiforme tumor cell lines and in 14 glioma and glioblastoma samples obtained from human brain biopsy. Expression of the low-abundance cyclooxygenase-1 and the high-abundance cytoskeletal element beta-actin were found not to significantly change in any cells or tissues studied and were used as internal controls. In contrast, proinflammatory cyclooxygenase-2, cytosolic phospholipase A2, IL-1beta, and beta-amyloid precursor protein expression levels were found to be significantly upregulated. These studies suggest that glioma and glioblastoma exhibit robust upregulation of proinflammatory and neurodegenerative genetic markers that may contribute to the pathobiology, phenotype, and proliferation of glial cell growth.

    Neuroreport 2008;19;9;981-5

  • The autophagy-related protein beclin 1 shows reduced expression in early Alzheimer disease and regulates amyloid beta accumulation in mice.

    Pickford F, Masliah E, Britschgi M, Lucin K, Narasimhan R, Jaeger PA, Small S, Spencer B, Rockenstein E, Levine B and Wyss-Coray T

    Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, USA.

    Autophagy is the principal cellular pathway for degradation of long-lived proteins and organelles and regulates cell fate in response to stress. Recently, autophagy has been implicated in neurodegeneration, but whether it is detrimental or protective remains unclear. Here we report that beclin 1, a protein with a key role in autophagy, was decreased in affected brain regions of patients with Alzheimer disease (AD) early in the disease process. Heterozygous deletion of beclin 1 (Becn1) in mice decreased neuronal autophagy and resulted in neurodegeneration and disruption of lysosomes. In transgenic mice that express human amyloid precursor protein (APP), a model for AD, genetic reduction of Becn1 expression increased intraneuronal amyloid beta (Abeta) accumulation, extracellular Abeta deposition, and neurodegeneration and caused microglial changes and profound neuronal ultrastructural abnormalities. Administration of a lentiviral vector expressing beclin 1 reduced both intracellular and extracellular amyloid pathology in APP transgenic mice. We conclude that beclin 1 deficiency disrupts neuronal autophagy, modulates APP metabolism, and promotes neurodegeneration in mice and that increasing beclin 1 levels may have therapeutic potential in AD.

    Funded by: NCI NIH HHS: CA84254, R01 CA084254; NIA NIH HHS: AG02270, AG10435, AG18440, AG20603, AG22074, AG5131, P01 AG010435, P01 AG022074, P50 AG005131, R01 AG018440, R01 AG020603, R01 AG030144, R37 AG018440

    The Journal of clinical investigation 2008;118;6;2190-9

  • The granulocyte macrophage colony stimulating factor (GM-CSF) regulates amyloid beta (Abeta) production.

    Volmar CH, Ait-Ghezala G, Frieling J, Paris D and Mullan MJ

    Roskamp Institute, 2040 Whitfield Avenue, Sarasota, FL 34243, USA.

    One of the hallmarks of Alzheimer's disease (AD) is the accumulation of amyloid beta (Abeta) plaques in the brain parenchyma. An inflammatory component to AD has been suggested in association with increased cytokine release. We have previously shown that CD40L stimulation of microglia induces increases in pro-inflammatory cytokines such as interleukin-1beta (IL-1beta), IL-6, IL-8 and GM-CSF. We have also shown that CD40L stimulation increases Abeta levels in HEK-293 cells over-expressing both the amyloid precursor protein (APP) and CD40 (HEK/APPsw/CD40). In this study, we show that GM-CSF neutralizing antibodies mitigate the CD40L-induced production of Abeta in HEK/APPsw/CD40 cells. In addition, we demonstrate that treatment of these cells with recombinant GM-CSF significantly increases Abeta levels. Furthermore, we show that shRNA silencing of the GM-CSF receptor gene significantly reduces Abeta levels to below base line in non-stimulated HEK/APPsw/CD40 cells. Analysis of cell surface proteins revealed that silencing of the GM-CSF receptor also decreases APP endocytosis (therefore reducing the availability of APP to be cleaved in the endosomes). Taken together, our results suggest that GM-CSF operates downstream of CD40/CD40L interaction and that GM-CSF modulates Abeta production by influencing APP trafficking. GM-CSF signaling may be a suitable therapeutic target against Abeta production in AD.

    Cytokine 2008;42;3;336-44

  • Altered ingestive behavior, weight changes, and intact olfactory sense in an APP overexpression model.

    Vloeberghs E, Van Dam D, Franck F, Serroyen J, Geert M, Staufenbiel M and De Deyn PP

    Laboratory of Neurochemistry and Behaviour, Institute Born-Bunge, Department of Biomedical Sciences, University of Antwerp, Wilrijk, Belgium.

    Transgenic APP23 mice were generated to model Alzheimer's disease. The APP23 model develops pathological features, learning deficits, and memory deficits analogous to dementing patients. In this report, transgenic mice exhibited several behavioral disturbances indicating the presence of neuropsychiatric symptoms of dementia. Aiming to verify whether the model also develops other behavioral problems, the authors investigated ingestive behavior in APP23 males of 3, 6 and 12 months. In addition, body weights of a naive male group were longitudinally monitored starting at weaning. Olfactory acuity was evaluated in mice of different age groups. Although olfactory functioning of APP23 mice appeared intact, they drank more and took more food pellets compared with wild-type littermates during a 1-week registration period. From the age of 4.5 weeks onward, APP23 males weighed significantly less than their control littermates, whereas this difference became more prominent with increasing age. Our results suggest the presence of a hypermetabolic state in this model. This is the first report, evidencing the presence of changes in eating and drinking behavior in a single transgenic Alzheimer mouse model.

    Behavioral neuroscience 2008;122;3;491-7

  • Co-localization of amyloid beta and tau pathology in Alzheimer's disease synaptosomes.

    Fein JA, Sokolow S, Miller CA, Vinters HV, Yang F, Cole GM and Gylys KH

    School of Nursing, University of California at Los Angeles School of Medicine, Sepulveda Veterans Administration Medical Center, Los Angeles, California 90095-6919, USA.

    The amyloid cascade hypothesis proposes that amyloid beta (Abeta) pathology precedes and induces tau pathology, but the neuropathological connection between these two lesions has not been demonstrated. We examined the regional distribution and co-localization of Abeta and phosphorylated tau (p-tau) in synaptic terminals of Alzheimer's disease brains. To quantitatively examine large populations of individual synaptic terminals, flow cytometry was used to analyze synaptosomes prepared from cryopreserved Alzheimer's disease tissue. An average 68.4% of synaptic terminals in the Alzheimer's disease cohort (n = 11) were positive for Abeta, and 32.3% were positive for p-tau; Abeta and p-tau fluorescence was lowest in cerebellum. In contrast to synaptic p-tau, which was highest in the entorhinal cortex and hippocampus (P = 0.004), synaptic Abeta fluorescence was significantly lower in the entorhinal cortex and hippocampus relative to neocortical regions (P = 0.0003). Synaptic Abeta and p-tau fluorescence was significantly correlated (r = 0.683, P < 0.004), and dual-labeling experiments demonstrated that 24.1% of Abeta-positive terminals were also positive for p-tau, with the highest fraction of dual labeling (39.3%) in the earliest affected region, the entorhinal cortex. Western blotting experiments show a significant correlation between synaptic Abeta levels measured by flow cytometry and oligomeric Abeta species (P < 0.0001). These results showing overlapping Abeta and tau pathology are consistent with a model in which both synaptic loss and dysfunction are linked to a synaptic amyloid cascade within the synaptic compartment.

    Funded by: NCI NIH HHS: CA 16042; NIA NIH HHS: 050 AG05142, 5AG016570, AG18879, P50 AG 16570; NIAID NIH HHS: AI 28697; NINDS NIH HHS: NS43946

    The American journal of pathology 2008;172;6;1683-92

  • Homer2 and Homer3 interact with amyloid precursor protein and inhibit Abeta production.

    Parisiadou L, Bethani I, Michaki V, Krousti K, Rapti G and Efthimiopoulos S

    Division of Animal and Human Physiology, Department of Biology, National and Kapodistrian University of Athens, 157 84 Panepistimiopolis, Ilisia, Athens, Greece.

    The study of Amyloid Precursor Protein (APP) processing has been the focus of considerable interest, since it leads to Abeta peptide generation, the main constituent of neuritic plaques found in brains of Alzheimer's disease patients. Therefore, the identification of novel APP binding partners that regulate Abeta peptide production represents a pharmaceutical target aiming at reducing Alphabeta pathology. In this study, we provide evidence that Homer2 and Homer3 but not Homer1 proteins interact specifically with APP. Their expression inhibits APP processing and reduces secretion of Abeta peptides. In addition, they decrease the levels of cell surface APP and inhibit maturation of APP and beta-secretase (BACE1). The effects of Homer2 and Homer3 on APP trafficking to the cell surface and/or on APP and BACE1 maturation could be part of the mechanism by which the expression of these proteins leads to the significant reduction of Abeta peptide production.

    Neurobiology of disease 2008;30;3;353-64

  • Plasma amyloid beta-protein and C-reactive protein in relation to the rate of progression of Alzheimer disease.

    Locascio JJ, Fukumoto H, Yap L, Bottiglieri T, Growdon JH, Hyman BT and Irizarry MC

    Massachusetts Alzheimer's Disease Research Center, Wang Ambulatory Care Center, Suite 720, Room 731-G, Massachusetts General Hospital, 15 Parkman St, Boston, MA 02114, USA. jlocascio@partners.org

    Objective: To examine whether plasma markers of amyloid precursor protein metabolism (amyloid beta-protein ending in Val-40 [Abeta40] and Ala-42 [Abeta42]), inflammation (high-sensitivity C-reactive protein), and folic acid metabolism (folic acid, vitamin B(12), and total homocysteine levels) are associated with the rate of cognitive and functional decline in persons with Alzheimer disease.

    Design: Longitudinal study across a mean (SD) of 4.2 (2.6) years with assessments at approximately 6- to 12-month intervals.

    Setting: Outpatient care.

    Patients: A cohort of 122 patients having a clinical diagnosis of probable Alzheimer disease, each with at least 2 assessments across time.

    Scores on the cognitive Information-Memory-Concentration subscale of the Blessed Dementia Scale and the functional Weintraub Activities of Daily Living Scale.

    Results: Low plasma levels of Abeta40, Abeta42, and high-sensitivity C-reactive protein were associated with a significantly more rapid cognitive decline, as indexed using the Blessed Dementia Scale, than were high levels. Low levels of Abeta42 and high-sensitivity C-reactive protein were significantly associated with more rapid functional decline on the Weintraub Activities of Daily Living Scale than were high levels. These plasma markers contributed about 5% to 12% of the variance accounted for on the Blessed Dementia Scale and the Activities of Daily Living Scale by fixed-effects predictors. Measures of folic acid metabolism were not associated with changes on either the Blessed Dementia Scale or the Activities of Daily Living Scale.

    Conclusions: Plasma markers of amyloid precursor protein metabolism and C-reactive protein may be associated with the rate of cognitive and functional decline in patients with Alzheimer disease.

    Funded by: NCCIH NIH HHS: R21 AT002311, R21 AT002311-01A2; NIA NIH HHS: AG05134, P50 AG005134; NINDS NIH HHS: T32 NS048005, T32 NS048005-04, T32 NS048005-05, T32NS048005

    Archives of neurology 2008;65;6;776-85

  • Regulation of Abeta pathology by beclin 1: a protective role for autophagy?

    Lee JA and Gao FB

    Gladstone Institute of Neurological Disease and Department of Neurology, UCSF, San Francisco, California 94158, USA.

    The amyloid beta (Abeta) peptide is thought to be a major culprit in Alzheimer disease (AD), and its production and degradation have been intensely investigated. Nevertheless, it remains largely unknown how Abeta pathology is modulated by the autophagy pathway. The study by Pickford and colleagues in this issue of the JCI shows that beclin 1, a multifunctional protein that also plays an important role in the autophagy pathway, affects some aspects of Abeta pathology in aged but not young transgenic mice expressing amyloid precursor protein (APP) (see the related article beginning on page 2190). These findings further support the notion that modulation of autophagy, in this case through beclin 1, may represent a novel therapeutic strategy for AD.

    The Journal of clinical investigation 2008;118;6;2015-8

  • Impact of cholesterol level upon APP and BACE proximity and APP cleavage.

    von Arnim CA, von Einem B, Weber P, Wagner M, Schwanzar D, Spoelgen R, Strauss WL and Schneckenburger H

    Deparment of Neurology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany. christine.arnim@uni-ulm.de

    Cleavage of APP by BACE is the first proteolytic step in the production of Amyloid beta (Abeta, which accumulates in senile plaques in Alzheimer's disease. BACE-cleavage of APP is thought to happen in endosomes. However, there are controversial data whether APP and BACE can already interact on the cell surface dependent on the cholesterol level. To examine whether APP and BACE come into close proximity on the cell surface in living cells, we employed a novel technique by combining time-resolved Förster resonance energy transfer (FRET) measurements with total internal reflection microscopy (TIRET microscopy). Our data indicate that BACE and APP come into close proximity within the cell, but probably not on the cell surface. To analyze the impact of alterations in cholesterol level upon BACE-cleavage, we measured sAPP secretion. Alteration of APP processing and BACE proximity by cholesterol might be explained by alterations in cell membrane fluidity.

    Biochemical and biophysical research communications 2008;370;2;207-12

  • Modulation of 'A'-type K+ current by rodent and human forms of amyloid beta protein.

    Kerrigan TL, Atkinson L, Peers C and Pearson HA

    Institutes of aMembrane and Systems Biology bCardiovascular Research, University of Leeds, Leeds, UK.

    The Alzheimer's disease related peptide amyloid beta (Abeta) might have a physiological role in upregulating K channel currents in neurones. Earlier studies used the human form of Abeta1-40 on rat neurones. We sought to confirm our hypothesis by use of rat Abeta, which has no Alzheimer's association. In rat cerebellar granule neurones and HEK293 cells expressing Kv4.2 subunits, whole-cell patch clamp of K currents revealed that preincubation of cells with recombinant human or rat Abeta1-40 (10 nM for 24 h) significantly increased K channel current density. This was accompanied by increased mRNA levels for Kv4.2. These data indicate that rodent and human Abeta are effective in modulating K currents. The effectiveness of nonaggregating rat Abeta also strongly supports a physiological role for the peptide.

    Funded by: Medical Research Council: G0600936

    Neuroreport 2008;19;8;839-43

  • Paired beta-sheet structure of an Abeta(1-40) amyloid fibril revealed by electron microscopy.

    Sachse C, Fändrich M and Grigorieff N

    Rosenstiel Basic Medical Sciences Research Center and Howard Hughes Medical Institute, Brandeis University, MS 029, Waltham, MA 02454-9110, USA.

    Alzheimer's disease is a neurodegenerative disorder that is characterized by the cerebral deposition of amyloid fibrils formed by Abeta peptide. Despite their prevalence in Alzheimer's and other neurodegenerative diseases, important details of the structure of amyloid fibrils remain unknown. Here, we present a three-dimensional structure of a mature amyloid fibril formed by Abeta(1-40) peptide, determined by electron cryomicroscopy at approximately 8-A resolution. The fibril consists of two protofilaments, each containing approximately 5-nm-long regions of beta-sheet structure. A local twofold symmetry within each region suggests that pairs of beta-sheets are formed from equivalent parts of two Abeta(1-40) peptides contained in each protofilament. The pairing occurs via tightly packed interfaces, reminiscent of recently reported steric zipper structures. However, unlike these previous structures, the beta-sheet pairing is observed within an amyloid fibril and includes significantly longer amino acid sequences.

    Funded by: Howard Hughes Medical Institute; NIGMS NIH HHS: 1 P01 GM-62580, P01 GM062580

    Proceedings of the National Academy of Sciences of the United States of America 2008;105;21;7462-6

  • A novel sorting nexin modulates endocytic trafficking and alpha-secretase cleavage of the amyloid precursor protein.

    Schöbel S, Neumann S, Hertweck M, Dislich B, Kuhn PH, Kremmer E, Seed B, Baumeister R, Haass C and Lichtenthaler SF

    Center for Integrated Protein Science and the Adolf-Butenandt-Institut, Ludwig Maximilians University, Munich, Germany.

    Ectodomain shedding of the amyloid precursor protein (APP) by the two proteases alpha- and beta-secretase is a key regulatory event in the generation of the Alzheimer disease amyloid beta peptide (Abeta). beta-Secretase catalyzes the first step in Abeta generation, whereas alpha-secretase cleaves within the Abeta domain, prevents Abeta generation, and generates a secreted form of APP with neuroprotective properties. At present, little is known about the cellular mechanisms that control APP alpha-secretase cleavage and Abeta generation. To explore the contributory pathways, we carried out an expression cloning screen. We identified a novel member of the sorting nexin (SNX) family of endosomal trafficking proteins, called SNX33, as a new activator of APP alpha-secretase cleavage. SNX33 is a homolog of SNX9 and was found to be a ubiquitously expressed phosphoprotein. Exogenous expression of SNX33 in cultured cells increased APP alpha-secretase cleavage 4-fold but surprisingly had little effect on beta-secretase cleavage. This effect was similar to the expression of the dominant negative dynamin-1 mutant K44A. SNX33 bound the endocytic GTPase dynamin and reduced the rate of APP endocytosis in a dynamin-dependent manner. This led to an increase of APP at the plasma membrane, where alpha-secretase cleavage mostly occurs. In summary, our study identifies SNX33 as a new endocytic protein, which modulates APP endocytosis and APP alpha-secretase cleavage, and demonstrates that the rate of APP endocytosis is a major control factor for APP alpha-secretase cleavage.

    The Journal of biological chemistry 2008;283;21;14257-68

  • Atypical early-onset Alzheimer's disease caused by the Iranian APP mutation.

    Lindquist SG, Nielsen JE, Stokholm J, Schwartz M, Batbayli M, Ballegaard M, Erdal J, Krabbe K and Waldemar G

    Memory Disorders Research Group, Department of Neurology, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. suzanne.lindquist@rh.regionh.dk

    Background: Approximately 1% of all cases of Alzheimer's disease are inherited autosomal dominantly, and to date, three causative genes have been found, the Presenilin 1 (PSEN1) gene, the Presenilin 2 (PSEN2) gene and the Amyloid precursor protein (APP) gene. We describe atypical phenotypic features in a family with a pathogenic APP gene mutation and discuss possible explanations for these atypical features.

    We report a family with a history of dementia compatible with autosomal dominant transmission. The disease course in the proband was not typical for Alzheimer's disease as the diagnosis was preceded by 8 years of an isolated amnesia. Further, the proband had epilepsy with complex partial seizures and central degenerative autonomic failure as determined by clinical physiology. Sequencing the three known causative Alzheimer genes revealed a pathogenic missense mutation, APP Thr714Ala (the Iranian mutation).

    Conclusions: The atypical clinical phenotype with long prodromal phase, autonomic failure and seizures in this new proband with the APP Thr714Ala mutation illustrates the clinical heterogeneity in families with identical pathogenic mutations.

    Journal of the neurological sciences 2008;268;1-2;124-30

  • Intracellular copper deficiency increases amyloid-beta secretion by diverse mechanisms.

    Cater MA, McInnes KT, Li QX, Volitakis I, La Fontaine S, Mercer JF and Bush AI

    Oxidation Biology Laboratory, Mental Health Research Institute of Victoria, Parkville, Victoria 3052, Australia.

    In Alzheimer's disease there is abnormal brain copper distribution, with accumulation of copper in amyloid plaques and a deficiency of copper in neighbouring cells. Excess copper inhibits Abeta (amyloid beta-peptide) production, but the effects of deficiency have not yet been determined. We therefore studied the effects of modulating intracellular copper levels on the processing of APP (amyloid precursor protein) and the production of Abeta. Human fibroblasts genetically disposed to copper accumulation secreted higher levels of sAPP (soluble APP ectodomain)alpha into their medium, whereas fibroblasts genetically manipulated to be profoundly copper deficient secreted predominantly sAPPbeta and produced more amyloidogenic beta-cleaved APP C-termini (C99). The level of Abeta secreted from copper-deficient fibroblasts was however regulated and limited by alpha-secretase cleavage. APP can be processed by both alpha- and beta-secretase, as copper-deficient fibroblasts secreted sAPPbeta exclusively, but produced primarily alpha-cleaved APP C-terminal fragments (C83). Copper deficiency also markedly reduced the steady-state level of APP mRNA whereas the APP protein level remained constant, indicating that copper deficiency may accelerate APP translation. Copper deficiency in human neuroblastoma cells significantly increased the level of Abeta secretion, but did not affect the cleavage of APP. Therefore copper deficiency markedly alters APP metabolism and can elevate Abeta secretion by either influencing APP cleavage or by inhibiting its degradation, with the mechanism dependent on cell type. Overall our results suggest that correcting brain copper imbalance represents a relevant therapeutic target for Alzheimer's disease.

    The Biochemical journal 2008;412;1;141-52

  • APPswe mutation increases the frequency of spontaneous Ca2+-oscillations in rat hippocampal neurons.

    Kloskowska E, Malkiewicz K, Winblad B, Benedikz E and Bruton JD

    Karolinska Institutet, NVS Department, Div. Neurodegeneration, Novum Plan 5, 14186 Stockholm, Sweden. ewa.kloskowska@ki.se

    Altered calcium homeostasis is implicated in the pathogenesis of Alzheimer's disease (AD). Much effort has been put into understanding the association between protein mutations causative of this devastating neurodegenerative disease and perturbed calcium signaling. Whereas the presenilin mutations have received most attention in the context of neuronal calcium signaling, we focused on the effects of APP with the so-called Swedish mutation (APPswe) on spontaneous neuronal activity. We observed that primary hippocampal neurons from an APPswe transgenic rat showed increased frequency and unaltered amplitude of spontaneous calcium oscillations as compared to wild-type neurons. We found that the altered calcium signaling of APPswe transgenic neurons was unlikely to be due to modulation of the NMDA or nicotinic neurotransmitter systems, and did not depend on secreted APP derivates. The implications of this effect of APP are discussed.

    Neuroscience letters 2008;436;2;250-4

  • Abeta-globulomers are formed independently of the fibril pathway.

    Gellermann GP, Byrnes H, Striebinger A, Ullrich K, Mueller R, Hillen H and Barghorn S

    Neuroscience Discovery Research, Abbott GmbH & Co. KG, Knollstrasse, D-67061 Ludwigshafen, Germany.

    Soluble A beta-oligomers are currently discussed as the major causative species for the development of Alzheimer's disease (AD). Consequently, the beta-amyloid cascade hypothesis was extended by A beta-oligomers and their central neuropathogenic role in AD. However, the molecular structure of A beta-oligomers and their relation to amyloid fibril formation remains elusive. Previously we demonstrated that incubation of A beta(1-42) with SDS or fatty acids induces the formation of a homogeneous globular A beta-oligomer termed A beta-globulomer. In this study we investigated the role of A beta-globulomers in the aggregation pathway of A beta-peptide. We used in vitro assays such as thioflavin-T binding and aggregation inhibitors like Congo red to reveal that A beta-peptide in its A beta-globulomer conformation is a structural entity which is independent from amyloid fibril formation. In addition, cellular Alzheimer's-like plaque forming assays show the resistance of A beta-globulomers to deposition as amyloid plaques. We hypothesize that a conformational switch of A beta is decisive for either fibril formation or alternatively and independently A beta-globulomer formation.

    Neurobiology of disease 2008;30;2;212-20

  • FDG autoradiography reveals developmental and pathological effects of mutant amyloid in PDAPP transgenic mice.

    Valla J, Gonzalez-Lima F and Reiman EM

    Barrow Neurological Institute, St Joseph's Hospital & Medical Center, Phoenix, AZ 85013, USA. jvalla@chw.edu

    Transgenic mouse models of Alzheimer's disease (AD) show some characteristic features of the disease, and we aim to further bridge the gap between studies of humans with AD, those at risk, and these murine models by providing shared markers of disease which could be used to track progression and assess future interventions. Brain imaging measurements may prove useful in this regard. We previously found that the homozygous PDAPP mouse model of AD showed significant declines in glucose uptake with age in posterior cingulate cortex (PCC), an area homologous to the human posterior cingulate, which shows significant declines in AD and in those at risk for AD. To further evaluate this potential biomarker and its correlation across age, we used fluorodeoxyglucose (FDG) autoradiography at two ages (2 and 12 months) in wildtype, heterozygous, and homozygous PDAPP mice. We found significant posterior cingulate fluorodeoxyglucose uptake declines again in homozygous PDAPP mice, but at both ages assessed. There was a strong effect of gene dose; homozygous mice showed larger and earlier effects. These results, in conjunction with our previous analyses, indicate a nonlinear progression stemming from synergistic effects of the overexpressed mutant gene, both developmental and pathological. The posterior cingulate is preferentially vulnerable to both effects of transgene in the PDAPP mouse, and both are independent of amyloid deposition.

    Funded by: NIA NIH HHS: P30 AG 019610, P30 AG019610-07; NIMH NIH HHS: MH 076847, MH 65728

    International journal of developmental neuroscience : the official journal of the International Society for Developmental Neuroscience 2008;26;3-4;253-8

  • Adaptor protein sorting nexin 17 regulates amyloid precursor protein trafficking and processing in the early endosomes.

    Lee J, Retamal C, Cuitiño L, Caruano-Yzermans A, Shin JE, van Kerkhof P, Marzolo MP and Bu G

    Department of Pediatrics and Cell Biology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

    Accumulation of extracellular amyloid beta peptide (Abeta), generated from amyloid precursor protein (APP) processing by beta- and gamma-secretases, is toxic to neurons and is central to the pathogenesis of Alzheimer disease. Production of Abeta from APP is greatly affected by the subcellular localization and trafficking of APP. Here we have identified a novel intracellular adaptor protein, sorting nexin 17 (SNX17), that binds specifically to the APP cytoplasmic domain via the YXNPXY motif that has been shown previously to bind several cell surface adaptors, including Fe65 and X11. Overexpression of a dominant-negative mutant of SNX17 and RNA interference knockdown of endogenous SNX17 expression both reduced steady-state levels of APP with a concomitant increase in Abeta production. RNA interference knockdown of SNX17 also decreased APP half-life, which led to the decreased steady-state levels of APP. Immunofluorescence staining confirmed a colocalization of SNX17 and APP in the early endosomes. We also showed that a cell surface adaptor protein, Dab2, binds to the same YXNPXY motif and regulates APP endocytosis at the cell surface. Our results thus provide strong evidence that both cell surface and intracellular adaptor proteins regulate APP endocytic trafficking and processing to Abeta. The identification of SNX17 as a novel APP intracellular adaptor protein highly expressed in neurons should facilitate the understanding of the relationship between APP intracellular trafficking and processing to Abeta.

    Funded by: FIC NIH HHS: TW006456; NIA NIH HHS: R01 AG027924

    The Journal of biological chemistry 2008;283;17;11501-8

  • Role of the familial Dutch mutation E22Q in the folding and aggregation of the 15-28 fragment of the Alzheimer amyloid-beta protein.

    Baumketner A, Krone MG and Shea JE

    Department of Physics and Optical Science, University of North Carolina, Charlotte, NC 28223, USA. abaumket@uncc.edu

    Amyloid fibrils, large ordered aggregates of amyloid beta proteins (Abeta), are clinical hallmarks of Alzheimer's disease (AD). The aggregation properties of amyloid beta proteins can be strongly affected by single-point mutations at positions 22 and 23. The Dutch mutation involves a substitution at position 22 (E22Q) and leads to increased deposition rates of the AbetaE22Q peptide onto preseeded fibrils. We investigate the effect of the E22Q mutation on two key regions involved in the folding and aggregation of the Abeta peptide through replica exchange molecular dynamics simulations of the 15-28 fragment of the Abeta peptide. The Abeta15-28 peptide encompasses the 22-28 region that constitutes the most structured part of the Abeta peptide (the E22-K28 bend), as well as the central hydrophobic cluster (CHC) (segment 17-21), the primary docking site for Abeta monomers depositing onto fibrils. Our simulations show that the 22-28 bend is preserved in the Abeta(15-28) peptide and that the CHC, which is mostly unstructured, interacts with this bend region. The E22Q mutation does not affect the structure of the bend but weakens the interactions between the CHC and the bend. This leads to an increased population of beta-structure in the CHC. Our analysis of the fibril elongation reaction reveals that the CHC adopts a beta-strand conformation in the transition state ensemble, and that the E22Q mutation increases aggregation rates by lowering the barrier for Abeta monomer deposition onto a fibril. Thermodynamic signatures of this enhanced fibrillization process from our simulations are in good agreement with experimental observations.

    Funded by: NIGMS NIH HHS: GM083001

    Proceedings of the National Academy of Sciences of the United States of America 2008;105;16;6027-32

  • Identifying the minimal copper- and zinc-binding site sequence in amyloid-beta peptides.

    Minicozzi V, Stellato F, Comai M, Dalla Serra M, Potrich C, Meyer-Klaucke W and Morante S

    Dipartimento di Fisica, Università di Roma Tor Vergata and Istituto Nazionale di Fisica Nucleare, Via della Ricerca Scientifica 1, I-00133 Roma, Italy.

    With a combination of complementary experimental techniques, namely sedimentation assay, Fourier transform infrared spectroscopy, and x-ray absorption spectroscopy, we are able to determine the atomic structure around the metal-binding site in samples where amyloid-beta (Abeta) peptides are complexed with either Cu(II) or Zn(II). Exploiting information obtained on a selected set of fragments of the Abeta peptide, we identify along the sequence the histidine residues coordinated to the metal in the various peptides we have studied (Abeta(1-40), Abeta(1-16), Abeta(1-28), Abeta(5-23), and Abeta(17-40)). Our data can be consistently interpreted assuming that all of the peptides encompassing the minimal 1-16 amino acidic sequence display a copper coordination mode that involves three histidines (His(6), His(13), and His(14)). In zinc-Abeta complexes, despite the fact that the metal coordination appears to be more sensitive to solution condition and shows a less rigid geometry around the binding site, a four-histidine coordination mode is seen to be preferred. Lacking a fourth histidine along the Abeta peptide sequence, this geometrical arrangement hints at a Zn(II)-promoted interpeptide aggregation mode.

    The Journal of biological chemistry 2008;283;16;10784-92

  • NFkappaB-dependent control of BACE1 promoter transactivation by Abeta42.

    Buggia-Prevot V, Sevalle J, Rossner S and Checler F

    Institut de Pharmacologie Moléculaire et Cellulaire, UMR 6097 CNRS/UNSA, Equipe Labellisée Fondation pour la Recherche Médicale, 06560 Valbonne, France.

    Beta-amyloid (Abeta) peptides that accumulate in Alzheimer disease are generated from the beta-amyloid precursor protein (betaAPP) by cleavages by beta-secretase BACE1 and by presenilin-dependent gamma-secretase activities. Very few data document a putative cross-talk between these proteases and the regulatory mechanisms underlying such interaction. We show that presenilin deficiency lowers BACE1 maturation and affects both BACE1 activity and promoter transactivation. The specific gamma-secretase inhibitor DFK167 triggers the decrease of BACE1 activity in wild-type but not in presenilin-deficient fibroblasts. This decrease is also elicited by catalytically inactive gamma-secretase. The overexpression of APP intracellular domain (AICD), the gamma/epsilon-secretase-derived C-terminal product of beta-amyloid precursor protein, does not modulate BACE1 activity or promoter transactivation in fibroblasts and does not alter BACE1 expression in AICD transgenic brains of mice. A DFK167-sensitive increase of BACE1 activity is observed in cells overexpressing APPepsilon (the N-terminal product of betaAPP generated by epsilon-secretase cleavage harboring the Abeta domain but lacking the AICD sequence), suggesting that the production of Abeta could account for the modulation of BACE1. Accordingly, we show that HEK293 cells overexpressing wild-type betaAPP exhibit a DFK167-sensitive increase in BACE1 promoter transactivation that is increased by the Abeta-potentiating Swedish mutation. This effect was mimicked by exogenous application of Abeta42 but not Abeta40 or by transient transfection of cDNA encoding Abeta42 sequence. The IkappaB kinase inhibitor BMS345541 prevents Abeta-induced BACE1 promoter transactivation suggesting that NFkappaB could mediate this Abeta-associated phenotype. Accordingly, the overexpression of wild-type or Swedish mutated betaAPP does not modify the transactivation of BACE1 promoter constructs lacking NFkappaB-responsive element. Furthermore, APP/beta-amyloid precursor protein-like protein deficiency does not affect BACE1 activity and expression. Overall, these data suggest that physiological levels of endogenous Abeta are not sufficient per se to modulate BACE1 promoter transactivation but that exacerbated Abeta production linked to wild-type or Swedish mutated betaAPP overexpression modulates BACE1 promoter transactivation and activity via an NFkappaB-dependent pathway.

    The Journal of biological chemistry 2008;283;15;10037-47

  • Beta-amyloid(1-42) induces neuronal death through the p75 neurotrophin receptor.

    Sotthibundhu A, Sykes AM, Fox B, Underwood CK, Thangnipon W and Coulson EJ

    Queensland Brain Institute, The University of Queensland, Brisbane, Queensland 4072, Australia.

    Alzheimer's disease is characterized by the accumulation of neurotoxic amyloidogenic peptide Abeta, degeneration of the cholinergic innervation to the hippocampus (the septohippocampal pathway), and progressive impairment of cognitive function, particularly memory. Abeta is a ligand for the p75 neurotrophin receptor (p75(NTR)), which is best known for mediating neuronal death and has been consistently linked to the pathology of Alzheimer's disease. Here we examined whether p75(NTR) is required for Abeta-mediated effects. Treatment of wild-type but not p75(NTR)-deficient embryonic mouse hippocampal neurons with human Abeta(1-42) peptide induced significant cell death. Furthermore, injection of Abeta(1-42) into the hippocampus of adult mice resulted in significant degeneration of wild-type but not p75(NTR)-deficient cholinergic basal forebrain neurons, indicating that the latter are resistant to Abeta-induced toxicity. We also found that neuronal death correlated with Abeta(1-42) peptide-stimulated accumulation of the death-inducing p75(NTR) C-terminal fragment generated by extracellular metalloprotease cleavage of full-length p75(NTR). Although neuronal death was prevented in the presence of the metalloprotease inhibitor TAPI-2 (tumor necrosis factor-alpha protease inhibitor-2), Abeta(1-42)-induced accumulation of the C-terminal fragment resulted from inhibition of gamma-secretase activity. These results provide a novel mechanism to explain the early and characteristic loss of cholinergic neurons in the septohippocampal pathway that occurs in Alzheimer's disease.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2008;28;15;3941-6

  • Promotion of amyloid beta protein misfolding and fibrillogenesis by a lipid oxidation product.

    Liu L, Komatsu H, Murray IV and Axelsen PH

    Department of Pharmacology, University of Pennsylvania, Philadelphia, PA 19104, USA.

    Oxidatively damaged lipid membranes are known to promote the aggregation of amyloid beta proteins and fibril formation. Oxidative damage typically produces 4-hydroxy-2-nonenal when lipid membranes contain omega-6 polyunsaturated fatty acyl chains, and this compound is known to modify the three His residues in Abeta proteins by Michael addition. In this report, the ability of 4-hydroxy-2-nonenal to reproduce the previously observed amyloidogenic effects of oxidative lipid damage on amyloid beta proteins is demonstrated and the mechanism by which it exerts these effects is examined. Results indicate that 4-hydroxy-2-nonenal modifies the three His residues in amyloid beta proteins, which increases their membrane affinity and causes them to adopt a conformation on membranes that is similar to their conformation in a mature amyloid fibril. As a consequence, fibril formation is accelerated at relatively low protein concentrations, and the ability to seed the formation of fibrils by unmodified amyloid beta proteins is enhanced. These in vitro findings linking oxidative stress to amyloid fibril formation may be significant to the in vivo mechanism by which oxidative stress is linked to the formation of amyloid plaques in Alzheimer's disease.

    Journal of molecular biology 2008;377;4;1236-50

  • Beta-amyloid peptides 1-40betaA and 25-35betaA suppress human amylin-mediated death of RINm5F islet beta-cells with distinct actions on fibril formation.

    Bai JZ

    Department of Physiology, School of Medical and Health Sciences, University of Auckland, Auckland, New Zealand. j.bai@auckland.ac.nz

    Amyloid deposition is a common feature of Alzheimer's disease and type 2 diabetes related to beta-amyloid peptides (betaA) and human amylin (hA), respectively. Both betaA and hA form aggregates and fibrils and kill cultured cells. To investigate whether betaA and hA display peptide-specific toxicity on cultured islet beta-cells, we examined the effects of (1-40)betaA and (25-35)betaA peptides on hA-mediated cell death and [(125)I-Tyr(37)]hA precipitation. Synthetic hA aggregated in solution and evoked both conformation- and sequence-dependent cell death. While neither (1-40)betaA nor (25-35)betaA was toxic to islet beta-cells, they suppressed hA-evoked cell death in a concentration-dependent and saturable manner. Only (1-40)betaA, but not (25-35)betaA, showed trophic effects on cultured islet beta-cells and inhibited the precipitation of [(125)I]hA caused by hA. These results suggest that (25-35)betaA does not interfere with hA-mediated fibril formation. Suppression of hA-evoked death of cultured pancreatic islet beta-cells by the betaA peptides is likely to occur through a competing interaction at these cells.

    Cell biology international 2008;32;4;447-55

  • Carbon 11-labeled pittsburgh compound B positron emission tomographic amyloid imaging in patients with APP locus duplication.

    Remes AM, Laru L, Tuominen H, Aalto S, Kemppainen N, Mononen H, Någren K, Parkkola R and Rinne JO

    Clinical Research Centre, Oulu University Hospital, University of Oulu, Oulu, Finland. anne.remes@oulu.fi

    Objective: To investigate amyloid accumulation by carbon 11-labeled Pittsburgh Compound B (11C-PiB) in hereditary cerebral amyloid angiopathy and APP locus duplication.

    Positron emission tomography with 11C-PiB and magnetic resonance imaging were performed for 2 patients, 49-year-old and 60-year-old siblings with APP locus duplication, with hereditary Alzheimer disease and cerebral amyloid angiopathy.

    Change in 11C-PiB uptake.

    Results: Uptake of 11C-PiB was increased especially in the striatum (caudate nucleus to 225% and 280% of the control mean and putamen to 166% and 185% of the control mean) and in the posterior cingulate (to 168% and 198% of the control mean), and it was marginally increased in other cortical brain areas. The pattern of increased 11C-PiB uptake was different from that seen in sporadic Alzheimer disease.

    Conclusions: Amyloid imaging with 11C-PiB positron emission tomography is a useful tool for detecting in vivo amyloid accumulation in patients with hereditary cerebral amyloid angiopathy. However, the pattern of 11C-PiB accumulation differs between patients with typical AD and patients with APP locus duplication.

    Archives of neurology 2008;65;4;540-4

  • Clinical and neuropathological features of the arctic APP gene mutation causing early-onset Alzheimer disease.

    Basun H, Bogdanovic N, Ingelsson M, Almkvist O, Näslund J, Axelman K, Bird TD, Nochlin D, Schellenberg GD, Wahlund LO and Lannfelt L

    Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Huddinge, Sweden. hans.basun@pubcare.uu.se

    Background: A majority of mutations within the beta-amyloid region of the amyloid precursor protein (APP) gene cause inherited forms of intracerebral hemorrhage. Most of these mutations may also cause cognitive impairment, but the Arctic APP mutation is the only known intra-beta-amyloid mutation to date causing the more typical clinical picture of Alzheimer disease.

    Objective: To describe features of 1 Swedish and 1 American family with the previously reported Arctic APP mutation.

    Affected and nonaffected carriers of the Arctic APP mutation from the Swedish and American families were investigated clinically. In addition, 1 brain from each family was investigated neuropathologically.

    Results: The clinical picture, with age at disease onset in the sixth to seventh decade of life and dysfunction in multiple cognitive areas, is indicative of Alzheimer disease and similar to the phenotype for other Alzheimer disease APP mutations. Several affected mutation carriers displayed general brain atrophy and reduced blood flow of the parietal lobe as demonstrated by magnetic resonance imaging and single-photon emission computed tomography. One Swedish case and 1 American case with the Arctic APP mutation came to autopsy, and both showed no signs of hemorrhage but revealed severe congophilic angiopathy, region-specific neurofibrillary tangle pathological findings, and abundant amyloid plaques. Intriguingly, most plaques from both of these cases had a characteristic ringlike character.

    Conclusions: Overall, our findings corroborate that the Arctic APP mutation causes a clinical and neuropathological picture compatible with Alzheimer disease.

    Funded by: NIA NIH HHS: P50 AG005136, P50 AG005136-25

    Archives of neurology 2008;65;4;499-505

  • Identification of PSEN1 and APP gene mutations in Korean patients with early-onset Alzheimer's disease.

    Park HK, Na DL, Lee JH, Kim JW and Ki CS

    Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

    Although mutations in three genes, amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2), have been identified as genetic causes of early-onset Alzheimer s disease (EOAD), there has been a single report on a PSEN1 mutation in Koreans. In the present study, we performed a genetic analysis of six Korean patients with EOAD. Direct sequencing analysis of the APP, PSEN1 and PSEN2 genes revealed two different mutations of the PSEN1 gene (G206S and M233T) and one mutation of the APP gene (V715M) in three patients with age-at-onset of 34, 35, and 42 yr, respectively. In addition, two patients with age-at-onset of 55 and 62 yr, respectively, were homozygous for APOE epsilon 4 allele. One woman had no genetic alterations. These findings suggest that PSEN1 and APP gene mutations may not be uncommon in Korean patients with EOAD and that genetic analysis should be provided to EOAD patients not only for the identification of their genetic causes but also for the appropriate genetic counseling.

    Journal of Korean medical science 2008;23;2;213-7

  • Inhibitory effects of short-term administration of DL-alpha-lipoic acid on oxidative vulnerability induced by Abeta amyloid fibrils (25-35) in mice.

    Jesudason EP, Masilamoni JG, Ashok BS, Baben B, Arul V, Jesudoss KS, Jebaraj WC, Dhandayuthapani S, Vignesh S and Jayakumar R

    Bio-Organic and Neurochemistry Laboratory, Central Leather Research Institute, Adyar, Chennai 600 020, India.

    Abeta amyloid peptide is believed to induce oxidative stress leading to inflammation, which is postulated to play a significant role in the toxicity of Alzheimer's disease (AD). This study was designed to investigate the inhibitory effects of DL-alpha lipoic acid (LA), a potential free radical scavenger, on oxidative vulnerability induced by intraperitoneal injection of Abeta25-35 amyloid fibrils in mice. Mice were divided into three groups: control, Abeta amyloid toxicity induced (AT), and LA treated (ATL). Blood Plasma was separated, liver, spleen and brain were dissected and analysis of oxidants, antioxidants, ATPases, glial fibrillary acidic protein (GFAP) and nuclear factor kappa-B (NFkappaB) were carried out. Results show biochemical parameters such as reactive oxygen species (ROS) and lipid peroxidation (LPO) were significantly lowered (P < 0.05) and levels of antioxidants and ATPase (P < 0.05) were significantly increased (P < 0.05) in hepatocytes, splenocytes and astrocytes of the ATL group. Moreover, our histological results revealed a decreased GFAP immunoreactivity in the neocortical region and NFkappaB immunoreactivity in neocortex, liver and spleen. This study reiterates LA as a potent free radical scavenger to combat oxidative vulnerability in the treatment for Abeta amyloid toxicity.

    Molecular and cellular biochemistry 2008;311;1-2;145-56

  • Amyloidogenic processing but not amyloid precursor protein (APP) intracellular C-terminal domain production requires a precisely oriented APP dimer assembled by transmembrane GXXXG motifs.

    Kienlen-Campard P, Tasiaux B, Van Hees J, Li M, Huysseune S, Sato T, Fei JZ, Aimoto S, Courtoy PJ, Smith SO, Constantinescu SN and Octave JN

    Center for Neurosciences, Experimental Pharmacology Unit, Université Catholique de Louvain, B-1200 Brussels, Belgium.

    The beta-amyloid peptide (Abeta) is the major constituent of the amyloid core of senile plaques found in the brain of patients with Alzheimer disease. Abeta is produced by the sequential cleavage of the amyloid precursor protein (APP) by beta- and gamma-secretases. Cleavage of APP by gamma-secretase also generates the APP intracellular C-terminal domain (AICD) peptide, which might be involved in regulation of gene transcription. APP contains three Gly-XXX-Gly (GXXXG) motifs in its juxtamembrane and transmembrane (TM) regions. Such motifs are known to promote dimerization via close apposition of TM sequences. We demonstrate that pairwise replacement of glycines by leucines or isoleucines, but not alanines, in a GXXXG motif led to a drastic reduction of Abeta40 and Abeta42 secretion. beta-Cleavage of mutant APP was not inhibited, and reduction of Abeta secretion resulted from inhibition of gamma-cleavage. It was anticipated that decreased gamma-cleavage of mutant APP would result from inhibition of its dimerization. Surprisingly, mutations of the GXXXG motif actually enhanced dimerization of the APP C-terminal fragments, possibly via a different TM alpha-helical interface. Increased dimerization of the TM APP C-terminal domain did not affect AICD production.

    Funded by: NIA NIH HHS: AG027317, R01 AG027317, R01 AG027317-01, R01 AG027317-02, R01 AG027317-03, RF1 AG027317

    The Journal of biological chemistry 2008;283;12;7733-44

  • Protofibril assemblies of the arctic, Dutch, and Flemish mutants of the Alzheimer's Abeta1-40 peptide.

    Fawzi NL, Kohlstedt KL, Okabe Y and Head-Gordon T

    UCSF/UCB Joint Graduate Group in Bioengineering, Berkeley, California 94720, USA.

    Using a coarse-grained model of the Abeta peptide, we analyze the Arctic (E22G), Dutch (E22Q), and Flemish (A21G) familial Alzheimer's disease (FAD) mutants for any changes in the stability of amyloid assemblies with respect to the wild-type (WT) sequence. Based on a structural reference state of two protofilaments aligned to create the "agitated" protofibril as determined by solid-state NMR, we determine free energy trends for Abeta assemblies for the WT and FAD familial sequences. We find that the structural characteristics and oligomer size of the critical nucleus vary dramatically among the hereditary mutants. The Arctic mutant's disorder in the turn region introduces new stabilizing interactions that better align the two protofilaments, yielding a well-defined protofibril axis at relatively small oligomer sizes with respect to WT. By contrast, the critical nucleus for the Flemish mutant is beyond the 20 chains characterized in this study, thereby showing a strong shift in the equilibrium toward monomers with respect to larger protofibril assemblies. The Dutch mutant forms more ordered protofilaments than WT, but exhibits greater disorder in protofibril structure that includes an alternative polymorph of the WT fibril. An important conclusion of this work is that the Dutch mutant does not support the agitated protofibril assembly. We discuss the implications of the structural ensembles and free energy profiles for the FAD mutants in regards to interpretation of the kinetics of fibril assembly using chromatography and dye-binding experiments.

    Funded by: NIGMS NIH HHS: R01 GM 070919, R01 GM070919-02

    Biophysical journal 2008;94;6;2007-16

  • Homophilic interactions of the amyloid precursor protein (APP) ectodomain are regulated by the loop region and affect beta-secretase cleavage of APP.

    Kaden D, Munter LM, Joshi M, Treiber C, Weise C, Bethge T, Voigt P, Schaefer M, Beyermann M, Reif B and Multhaup G

    Institut für Chemie und Biochemie, Freie Universität Berlin, 14195 Berlin, Germany.

    We found previously by fluorescence resonance energy transfer experiments that amyloid precursor protein (APP) homodimerizes in living cells. APP homodimerization is likely to be mediated by two sites of the ectodomain and a third site within the transmembrane sequence of APP. We have now investigated the role of the N-terminal growth factor-like domain in APP dimerization by NMR, biochemical, and cell biological approaches. Under nonreducing conditions, the N-terminal domain of APP formed SDS-labile and SDS-stable complexes. The presence of SDS was sufficient to convert native APP dimers entirely into monomers. Addition of an excess of a synthetic peptide (APP residues 91-116) containing the disulfide bridge-stabilized loop inhibited cross-linking of pre-existing SDS-labile APP ectodomain dimers. Surface plasmon resonance analysis revealed that this peptide specifically bound to the N-terminal domain of APP and that binding was entirely dependent on the oxidation of the thiol groups. By solution-state NMR we detected small chemical shift changes indicating that the loop peptide interacted with a large protein surface rather than binding to a defined pocket. Finally, we studied the effect of the loop peptide added to the medium of living cells. Whereas the levels of alpha-secretory APP increased, soluble beta-cleaved APP levels decreased. Because Abeta40 and Abeta42 decreased to similar levels as soluble beta-cleaved APP, we conclude either that beta-secretase binding to APP was impaired or that the peptide allosterically affected APP processing. We suggest that APP acquires a loop-mediated homodimeric state that is further stabilized by interactions of hydrophobic residues of neighboring domains.

    The Journal of biological chemistry 2008;283;11;7271-9

  • Fyn modulation of Dab1 effects on amyloid precursor protein and ApoE receptor 2 processing.

    Hoe HS, Minami SS, Makarova A, Lee J, Hyman BT, Matsuoka Y and Rebeck GW

    Department of Neuroscience, Georgetown University Medical Center, 3970 Reservoir Road NW, Washington, DC 20057, USA.

    Dab1 is an intracellular adaptor protein that interacts with amyloid precursor protein (APP) and apoE receptor 2 (apoEr2), increases their levels on the cell surface, and increases their cleavage by alpha-secretases. To investigate the mechanism underlying these alterations in processing and trafficking of APP and apoEr2, we examined the effect of Fyn, an Src family-tyrosine kinase known to interact with and phosphorylate Dab1. Co-immunoprecipitation, co-immunostaining, and fluorescence lifetime imaging demonstrated an association between Fyn and APP. Fyn induced phosphorylation of APP at Tyr-757 of the (757)YENPTY(762) motif and increased cell surface expression of APP. Overexpression of Fyn alone did not alter levels of sAPPalpha or cytoplasmic C-terminal fragments, although it significantly decreased production of Abeta. However, in the presence of Dab1, Fyn significantly increased sAPPalpha and C-terminal fragments. Fyn-induced APP phosphorylation and cell surface levels of APP were potentiated in the presence of Dab1. Fyn also induced phosphorylation of apoEr2 and increased its cell surface levels and, in the presence of Dab1, affected processing of its C-terminal fragment. In vivo studies showed that sAPPalpha was decreased in the Fyn knock-out, supporting a role for Fyn in APP processing. These data demonstrate that Fyn, due in part to its effects on Dab1, regulates the phosphorylation, trafficking, and processing of APP and apoEr2.

    Funded by: NIA NIH HHS: AG 022455, AG 14473, P01 AG030128

    The Journal of biological chemistry 2008;283;10;6288-99

  • A new amyloid beta variant favoring oligomerization in Alzheimer's-type dementia.

    Tomiyama T, Nagata T, Shimada H, Teraoka R, Fukushima A, Kanemitsu H, Takuma H, Kuwano R, Imagawa M, Ataka S, Wada Y, Yoshioka E, Nishizaki T, Watanabe Y and Mori H

    Department of Neuroscience, Osaka City University Graduate School of Medicine, Osaka, Japan.

    Objective: Soluble oligomers of amyloid beta (Abeta), rather than amyloid fibrils, have been proposed to initiate synaptic and cognitive dysfunction in Alzheimer's disease (AD). However, there is no direct evidence in humans that this mechanism can cause AD. Here, we report a novel amyloid precursor protein (APP) mutation that may provide evidence to address this question.

    Methods: A Japanese pedigree showing Alzheimer's-type dementia was examined for mutations in APP, PSEN1, and PSEN2. In addition, 5,310 Japanese people, including 2,121 patients with AD, were screened for the novel APP mutation. The pathogenic effects of this mutation on Abeta production, degradation, aggregation, and synaptotoxicity were also investigated.

    Results: We identified a novel APP mutation (E693Delta) producing variant Abeta lacking gulutamate-22 (E22Delta) in Japanese pedigrees showing Alzheimer's-type dementia and AD. Although the secretion of total Abeta was markedly reduced by this mutation, the variant Abeta was more resistant to proteolytic degradation. The mutant peptides showed the unique aggregation property of enhanced oligomerization but no fibrillization, and inhibited hippocampal long-term potentiation more potently than wild-type peptide in rats in vivo. Consistent with the nonfibrillogenic property of the variant Abeta, a very low amyloid signal was observed in the patient's brain on positron emission tomography using Pittsburgh compound-B.

    Interpretation: The E693Delta mutation has been suggested as a cause of dementia because of enhanced formation of synaptotoxic Abeta oligomers. Our findings may provide genetic validation in humans for the emerging hypothesis that the synaptic and cognitive impairment in AD is primarily caused by soluble Abeta oligomers.

    Annals of neurology 2008;63;3;377-87

  • Interaction of amyloid precursor protein with contactins and NgCAM in the retinotectal system.

    Osterfield M, Egelund R, Young LM and Flanagan JG

    Department of Cell Biology and Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA.

    The amyloid precursor protein (APP) plays a central role in Alzheimer's disease, but its actions in normal development are not well understood. Here, a tagged APP ectodomain was used to identify extracellular binding partners in developing chick brain. Prominent binding sites were seen in the olfactory bulb and on retinal axons growing into the optic tectum. Co-precipitation from these tissues and tandem mass spectrometry led to the identification of two associated proteins: contactin 4 and NgCAM. In vitro binding studies revealed direct interactions among multiple members of the APP and contactin protein families. Levels of the APP processing fragment, CTFalpha, were modulated by both contactin 4 and NgCAM. In the developing retinotectal system, APP, contactin 4 and NgCAM are expressed in the retina and tectum in suitable locations to interact. Functional assays revealed regulatory effects of both APP and contactin 4 on NgCAM-dependent growth of cultured retinal axons, demonstrating specific functional interactions among these proteins. These studies identify novel binding and functional interactions among proteins of the APP, contactin and L1CAM families, with general implications for mechanisms of APP action in neural development and disease.

    Funded by: NEI NIH HHS: EY11559; NICHD NIH HHS: HD29417

    Development (Cambridge, England) 2008;135;6;1189-99

  • Presenilin-1 280Glu-->Ala mutation alters C-terminal APP processing yielding longer abeta peptides: implications for Alzheimer's disease.

    Van Vickle GD, Esh CL, Kokjohn TA, Patton RL, Kalback WM, Luehrs DC, Beach TG, Newel AJ, Lopera F, Ghetti B, Vidal R, Castaño EM and Roher AE

    The Longtine Center for Molecular Biology and Genetics, Sun Health Research Institute, Sun City, Arizona 85351, USA.

    Presenilin (PS) mutations enhance the production of the Abeta42 peptide that is derived from the amyloid precursor protein (APP). The pathway(s) by which the Abeta42 species is preferentially produced has not been elucidated, nor is the mechanism by which PS mutations produce early-onset dementia established. Using a combination of histological, immunohistochemical, biochemical, and mass spectrometric methods, we examined the structural and morphological nature of the amyloid species produced in a patient expressing the PS1 280Glu-->Ala familial Alzheimer's disease mutation. Abundant diffuse plaques were observed that exhibited a staining pattern and morphology distinct from previously described PS cases, as well as discreet amyloid plaques within the white matter. In addition to finding increased amounts of CT99 and Abeta42 peptides, our investigation revealed the presence of a complex array of Abeta peptides substantially longer than 42/43 amino acid residue species. The increased hydrophobic nature of longer Abeta species retained within the membrane walls could impact the structure and function of plasma membrane and organelles. These C-terminally longer peptides may, through steric effects, dampen the rate of turnover by critical amyloid degrading enzymes such as neprilysin and insulin degrading enzyme. A complete understanding of the deleterious side effects of membrane bound Abeta as a consequence of gamma-secretase alterations is needed to understand Alzheimer's disease pathophysiology and will aid in the design of therapeutic interventions.

    Funded by: NIA NIH HHS: P30 AG010133, P30 AG019610, P30 AG10133, P30 AG19610, R01 AG019795, R01 AG019795-08, R01AG-19795

    Molecular medicine (Cambridge, Mass.) 2008;14;3-4;184-94

  • Toward a confocal subcellular atlas of the human proteome.

    Barbe L, Lundberg E, Oksvold P, Stenius A, Lewin E, Björling E, Asplund A, Pontén F, Brismar H, Uhlén M and Andersson-Svahn H

    Department of Biotechnology, AlbaNova University Center, Royal Institute of Technology, SE-106 91 Stockholm, Sweden.

    Information on protein localization on the subcellular level is important to map and characterize the proteome and to better understand cellular functions of proteins. Here we report on a pilot study of 466 proteins in three human cell lines aimed to allow large scale confocal microscopy analysis using protein-specific antibodies. Approximately 3000 high resolution images were generated, and more than 80% of the analyzed proteins could be classified in one or multiple subcellular compartment(s). The localizations of the proteins showed, in many cases, good agreement with the Gene Ontology localization prediction model. This is the first large scale antibody-based study to localize proteins into subcellular compartments using antibodies and confocal microscopy. The results suggest that this approach might be a valuable tool in conjunction with predictive models for protein localization.

    Molecular & cellular proteomics : MCP 2008;7;3;499-508

  • Beta2-microglobulin amyloid fragment organization and morphology and its comparison to Abeta suggests that amyloid aggregation pathways are sequence specific.

    Zheng J, Jang H and Nussinov R

    Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325, USA. zhengj@uakron.edu

    Beta2-microglobulin (beta2-m) can form dialysis-related amyloid deposits. The structure of a fragment of beta2-m (K3, Ser20-Lys41) in the oligomeric state has recently been solved. We modeled equilibrium structures of K3 oligomers with different organizations (single and double layers) and morphologies (linear-like and annular-like) for the wild-type and mutants using all-atom molecular dynamics (MD) simulations. We focused on the sheet-to-sheet association force, which is the key in the amyloid organization and morphology. For the linear-like morphology, we observed two stable organizations: (i) single-layered parallel-stranded beta-sheets and (ii) double-layered parallel-stranded antiparallel beta-sheets stacked perpendicular to the fibril axis through the hydrophobic N-terminal-N-terminal (NN) interface. No stable annular structures were observed. The structural instability of the annular morphology was mainly attributed to electrostatic repulsion of three negatively charged residues (Asp15, Glu17, and Asp19) projecting from the same beta-strand surface. Linear-like and annular-like double-layered oligomers with the NN interface are energetically more favorable than other oligomers with C-terminal-C-terminal (CC) or C-terminal-N-terminal (CN) interfaces, emphasizing the importance of hydrophobic interactions and side-chain packing in stabilizing these oligomers. Moreover, only linear-like structures, rather than annular structures, with parallel beta-strands and antiparallel beta-sheet arrangements are possible intermediate states for the K3 beta2-m amyloid fibrils in solution. Comparing the beta2-m fragment with Abeta indicates that while both adopt similar beta-strand-turn-beta-strand motifs, the final amyloid structures can be dramatically different in size, structure, and morphology due to differences in side-chain packing arrangements, intermolecular driving forces, sequence composition, and residue positions, suggesting that the mechanism leading to distinct morphologies and the aggregation pathways is sequence specific.

    Funded by: Intramural NIH HHS; NCI NIH HHS: N01-CO-12400

    Biochemistry 2008;47;8;2497-509

  • Inhibition of APP intracellular domain (AICD) transcriptional activity via covalent conjugation with Nedd8.

    Lee MR, Lee D, Shin SK, Kim YH and Choi CY

    Department of Biological Science, Sungkyunkwan University, 300 Chunchundong, Suwon 440-746, Republic of Korea.

    The processing of amyloid precursor protein (APP) by gamma-secretase generates the APP intracellular domain (AICD), which functions as a transcriptional factor for target gene activation following localization into the nucleus. In this study, we demonstrate that AICD could be modified via covalent conjugation with Nedd8, a ubiquitin-like protein. Domain analysis and site-directed substitution of neddylation sites showed that multiple lysine residues of the APP C-terminal C99 fragment including AICD were acceptor sequences for Nedd8 conjugation. AICD-mediated transcriptional activation was inhibited by Nedd8 conjugation. Furthermore, the transcriptional activity of the neddylation-defective AICD mutant was not altered by Nedd8 expression. Nedd8 conjugation of AICD inhibited its interaction with Fe65, and consequently resulted in the impairment of AICD-Fe65-Tip60 complex formation for the transcriptional activation of the target gene. These results illustrate the regulatory mechanisms by which AICD transcriptional activity might be regulated via covalent conjugation with Nedd8.

    Biochemical and biophysical research communications 2008;366;4;976-81

  • Membrane fusogenic activity of the Alzheimer's peptide A beta(1-42) demonstrated by small-angle neutron scattering.

    Dante S, Hauss T, Brandt A and Dencher NA

    BENSC, Hahn-Meitner-Institut, Glienicker Strasse 100, D-14109 Berlin, Germany. silvia.dante@hmi.de

    Amyloid-beta peptide (A beta) is considered a triggering agent of Alzheimer's disease. In relation to a therapeutic treatment of the disease, the interaction of A beta with the cell membrane has to be elucidated at the molecular level to understand its mechanism of action. In previous works, we had ascertained by neutron diffraction on stacked lipid multilayers that a toxic fragment of A beta is able to penetrate and perturb the lipid bilayer. Here, the influence of A beta(1-42), the most abundant A beta form in senile plaques, on unilamellar lipid vesicles of phospholipids is investigated by small-angle neutron scattering. We have used the recently proposed separated form factor method to fit the data and to obtain information about the vesicle diameter and structure of the lipid bilayer and its change upon peptide administration. The lipid membrane parameters were obtained with different models of the bilayer profile. As a result, we obtained an increase in the vesicle radii, indicating vesicle fusion. This effect was particularly enhanced at pH 7.0 and at a high peptide/lipid ratio. At the same time, a thinning of the lipid bilayer occurred. A fusogenic activity of the peptide may have very important consequences and may contribute to cytotoxicity by destabilizing the cell membrane. The perturbation of the bilayer structure suggests a strong interaction and/or insertion of the peptide into the membrane, although its localization remains beyond the limit of the experimental resolution.

    Journal of molecular biology 2008;376;2;393-404

  • Cellular localization of Nicastrin affects amyloid beta species production.

    Morais VA, Leight S, Pijak DS, Lee VM and Costa J

    Instituto de Tecnologia Química e Biológica, Apartado 127, Oeiras 2781-901, Portugal.

    The gamma-secretase complex, composed by presenilin, nicastrin, APH-1 and PEN-2, is involved in intramembranous proteolysis of membrane proteins, such as amyloid precursor protein or Notch. Cleavage occurs in multiple cellular compartments. Here, nicastrin mutants containing targeting signals to the endoplasmic reticulum, trans-Golgi network, lysosomes, or plasma membrane have been shown to yield active gamma-secretase complexes with different activities and specificities: wild-type and plasma membrane nicastrin complexes yielded the highest amounts of secreted amyloid-beta peptide (Abeta), predominantly Abeta40, whereas intracellular targeted mutants produced intracellular Abeta, with a comparatively higher amount of Abeta42. These results suggest that compartmental microenvironments play a role in gamma-secretase activity and specificity.

    FEBS letters 2008;582;3;427-33

  • Expression of amyloid beta peptide in human platelets: pivotal role of the phospholipase Cgamma2-protein kinase C pathway in platelet activation.

    Shen MY, Hsiao G, Fong TH, Chou DS and Sheu JR

    Graduate Institute of Medical Sciences, Taipei Medical University, Taipei, Taiwan.

    The amyloid beta peptide (Abeta), a mediator of neuronal and vascular degeneration in the pathogenesis of Alzheimer's disease and cerebral amyloid angiopathy may have peripheral actions. Platelets are enriched with Abeta and have been shown to enhance platelet actions. However, the detailed signaling pathways through which Abeta activates platelets have not been previously explored. In this study, we examined the intra-platelet Abeta distribution using a gold labeling technique and noted that Abeta was predominantly localized in the cytoplasm of resting platelets. A marked increase in Abeta-gold labeling in an open canalicular system was observed in collagen-activated platelets. Exogenous Abeta (2-10 microM) stimulated platelet aggregation accompanied by phospholipase Cgamma2 (PLCgamma2) phosphorylation, phosphoinositide breakdown, and [Ca(2+)]i mobilization as well as protein kinase C (PKC) activation. Ro318220, an inhibitor of PKC, suppressed Abeta-induced platelet aggregation, PKC activation, and [Ca(2+)]i mobilization in platelets, suggesting that the PLCgamma2-PKC pathway is involved in Abeta-induced platelet aggregation. In the electron spin resonance study, Abeta (2 and 10 microM) markedly triggered hydroxyl radical formation in platelets. In an in vivo study, Abeta (2mg/kg) significantly shortened the latency for inducing platelet plug formation in the mesenteric venules of mice. In conclusion, we are the first to demonstrate (1) the distribution of Abeta in human platelets; and that (2) Abeta activation of platelets is mediated, at least partially, by the PLCgamma2-PKC pathway; and (3) Abeta triggers thrombus formation in vivo.

    Pharmacological research : the official journal of the Italian Pharmacological Society 2008;57;2;151-8

  • Low prevalence of APP duplications in Swedish and Finnish patients with early-onset Alzheimer's disease.

    Blom ES, Viswanathan J, Kilander L, Helisalmi S, Soininen H, Lannfelt L, Ingelsson M, Glaser A and Hiltunen M

    Section of Molecular Geriatrics, Department of Public Health and Caring Sciences, Uppsala University, Uppsala, Sweden. elin.blom@pubcare.uu.se

    Familial early-onset Alzheimer's disease with cerebral amyloid angiopathy (EOAD/CAA) was recently associated with duplications of the gene for the amyloid-beta precursor protein (APP). In this study, we have screened for duplications of APP in patients with EOAD from Sweden and Finland. Seventy-five individuals from families with EOAD and 66 individuals with EOAD without known familial inheritance were screened by quantitative PCR. On the basis of the initial results, a portion of the samples was also investigated with quantitative multiplex PCR. No duplications of APP were identified, whereby we conclude that this is not a common cause of EOAD in the Swedish and Finnish populations, at least not in our collection of families and cases.

    European journal of human genetics : EJHG 2008;16;2;171-5

  • One-year longitudinal evaluation of sensorimotor functions in APP751SL transgenic mice.

    Le Cudennec C, Faure A, Ly M and Delatour B

    Laboratoire de Neurobiologie de l'Apprentissage, de la Mémoire & de la Communication, CNRS UMR 8620, Université Paris-Sud, Orsay Cedex, France.

    Intracerebral amyloid-beta (Abeta) peptide deposition is considered to play a key role in Alzheimer's disease and is designated as a principal therapeutic target. The relationship between brain Abeta levels and clinical deficits remains, however, unclear, both in human patients and in animal models of the disease. The purpose of the present study was to investigate, in a transgenic mouse model of brain amyloidosis, the consequences of Abeta deposition on basic neurological functions using a longitudinal approach. Animals were phenotyped at different ages corresponding to graded neuropathological stages (from no extracellular Abeta deposition to high amyloid loads). Sensory functions were evaluated by assessing visual and olfactory abilities and did not show any effects of the amyloid precursor protein (APP) transgene. Motor functions were assessed using multiple experimental paradigms. Results showed that motor strength was considerably reduced in APP transgenic mice compared with control animals. No deficit was noted in a motor coordination test although APP transgenic mice displayed decreased locomotion on a stationary beam. Hypolocomotion was also observed in the standard open-field test. Measures of anxiety obtained in the elevated plus-maze show some evidence of hyperanxiety in 15-month-old transgenic mice. Some of the neurological impairments showed by APP mice had an early onset and worsened with progressive aging, in parallel to gradual accumulation of Abeta in brain parenchyma. Relationships between neuropathologically assessed amyloid loads and behavioral deficits were further explored, and it was observed that motor strength deficits were correlated with cortical amyloid burden.

    Genes, brain, and behavior 2008;7 Suppl 1;83-91

  • Plasma beta amyloid and cytokine profile in women with Alzheimer's disease.

    Baranowska-Bik A, Bik W, Wolinska-Witort E, Martynska L, Chmielowska M, Barcikowska M and Baranowska B

    Neuroendocrinology Department, Medical Centre of Postgraduate Education, Warsaw, Poland. zncmkp@op.pl

    Alzheimer's disease (AD) belongs to a group of neurodegenerative disorders. It is characterized by irreversible and progressive memory loss accompanied with decline in other cognitive functions. At a microscopic level, the typical neuropathologic features, senile plaques and neurofibrillary lesions are found. The pathological processes lead to neuronal loss, synaptic dysfunction and inappropriate activity of neurotransmitters. The major constituent of senile plaques is abnormally aggregated beta amyloid protein. Beta amyloid (Abeta) is a short (40-42 amino acid) product of proteolysis of the transmembrane amyloid precursor protein (APP). Extracellular depositions of Abeta 1-42 may initiate a wide range of pathological processes including glia activation, neuroinflammation and neuronal apoptosis. There is convincing evidence that inflammatory response to accumulation of beta amyloid plays a pivotal role in the progression of neuropathological changes found in AD. Current research was directed at assessing beta amyloid, cytokines (IL-6, IL-10 and TNF alpha) plasma levels in women with AD. Hundred and twenty four women, aged between 59 to 86 years, were enrolled in the study. Amongst them 57 were diagnosed with AD (29 subjects in early stage and 28 subjects with moderate to severe stadium of disease) and 67 women without dementia were investigated as a control group. The lowest values of Abeta 1-42 were found in AD subjects in moderate to severe stage of disease as compared with the early stage of AD (p< 0.05) and the control group (p<0.01). Change in IL-6 values was significantly different between groups with the lowest values found in women without dementia. Both subset of AD patients demonstrated statistically enhanced IL-6 levels when compared with the control group (p<0.001, p<0.01 respectively for early and moderate/severe stage of AD). Moreover, our study revealed a trend to increase in TNF alfa and IL-10 values in AD. However, those differences were not statistically significant. In addition, we did not detect any correlations between plasma beta amyloid and investigated cytokines.

    Neuro endocrinology letters 2008;29;1;75-9

  • Promoter polymorphisms which modulate APP expression may increase susceptibility to Alzheimer's disease.

    Lv H, Jia L and Jia J

    Department of Neurology, Xuanwu Hospital of the Capital University of Medical Sciences, Beijing 100053, PR China.

    Increasing evidence indicates that variants in promoter of the beta-amyloid precursor protein (APP) gene could up-regulate the APP gene expression and aggravate the amyloid beta protein (A beta) accumulation, thus contributing to the development of Alzheimer's disease (AD). In Chinese Han populations we found three polymorphisms in APP promoter: -877T/C(rs466433), -955A/G(rs364048) and -9G/C. The -877T and -955A alleles were over-represented in 209 sporadic AD (SAD) patients when compared to those in 437 healthy individuals. Furthermore, -877T/C and -955A/G were in strong linkage disequilibrium and they constructed a relatively risky -877T/-955A and a relatively protective -877C/-955G. Luciferase reporter assay indicated -877T/-955A had four times higher transcriptional activity than -877C/-955G. A more marked increase in -877T/-955A transcriptional activity was seen when under A beta(25-35) treatment. As for the -9G/C polymorphism, significant differences between the two alleles were not observed either in genetic evaluation or in functional assay. The present study provides strong evidence that APP promoter polymorphisms that significantly increase APP expression levels are associated with development of SAD.

    Neurobiology of aging 2008;29;2;194-202

  • Amyloid beta oligomers (A beta(1-42) globulomer) suppress spontaneous synaptic activity by inhibition of P/Q-type calcium currents.

    Nimmrich V, Grimm C, Draguhn A, Barghorn S, Lehmann A, Schoemaker H, Hillen H, Gross G, Ebert U and Bruehl C

    Neuroscience Discovery, Global Pharmaceutical Research and Development, Abbott, D-67061 Ludwigshafen, Germany. volker.nimmrich@abbott.com

    Abnormal accumulation of soluble oligomers of amyloid beta (Abeta) is believed to cause malfunctioning of neurons in Alzheimer's disease. It has been shown that Abeta oligomers impair synaptic plasticity, thereby altering the ability of the neuron to store information. We examined the underlying cellular mechanism of Abeta oligomer-induced synaptic modifications by using a recently described stable oligomeric Abeta preparation called "Abeta(1-42) globulomer." Synthetically prepared Abeta(1-42) globulomer has been shown to localize to neurons and impairs long-term potentiation (Barghorn et al., 2005). Here, we demonstrate that Abeta(1-42) globulomer does not affect intrinsic neuronal properties, as assessed by measuring input resistance and discharge characteristics, excluding an unspecific alteration of membrane properties. We provide evidence that Abeta(1-42) globulomer, at concentrations as low as 8 nM, specifically suppresses spontaneous synaptic activity resulting from a reduction of vesicular release at terminals of both GABAergic and glutamatergic synapses. EPSCs and IPSCs were primarily unaffected. A detailed search for the precise molecular target of Abeta(1-42) globulomer revealed a specific inhibition of presynaptic P/Q calcium currents, whereas other voltage-activated calcium currents remained unaltered. Because intact P/Q calcium currents are needed for synaptic plasticity, the disruption of such currents by Abeta(1-42) globulomer may cause deficits in cellular mechanisms of information storage in brains of Alzheimer's disease patients. The inhibitory effect of Abeta(1-42) globulomer on synaptic vesicle release could be reversed by roscovitine, a specific enhancer of P/Q currents. Selective enhancement of the P/Q calcium current may provide a promising strategy in the treatment of Alzheimer's disease.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2008;28;4;788-97

  • Exclusion of the native alpha-helix from the amyloid fibrils of a mixed alpha/beta protein.

    Morgan GJ, Giannini S, Hounslow AM, Craven CJ, Zerovnik E, Turk V, Waltho JP and Staniforth RA

    Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.

    Members of the cystatin superfamily are involved in an inherited form of cerebral amyloid angiopathy and readily form amyloid fibrils in vitro. We have determined the structured core of human stefin B (cystatin B) amyloid fibrils using quenched hydrogen exchange and NMR. The core contains residues from four of the five strands of the native beta-sheet, delimited by unprotected loop regions analogous to those of the native monomeric structure. However, non-native features are also apparent, the most striking of which is the exclusion of the native alpha-helix. Before forming amyloid in vitro, cystatins dimerise via 3D domain swapping, and assemble into tetramers with trans to cis isomerism of a conserved proline. In the fibril, the hinge loop that forms an extended beta-structure in the dimer remains protected, consistent with the domain-swapping interface being maintained. However, the fibril data are not compatible with a simple 3D domain-swapping model for amyloid formation, and the displacement of the helix points to alternative packing arrangements of native-like beta-structure, in which proline isomerism is important in preventing steric clashing.

    Journal of molecular biology 2008;375;2;487-98

  • PI3-K- and PKC-dependent up-regulation of APP processing enzymes by retinoic acid.

    Holback S, Adlerz L, Gatsinzi T, Jacobsen KT and Iverfeldt K

    Department of Neurochemistry, Stockholm University, SE10691 Stockholm, Sweden.

    Retinoic acid stimulates alpha-secretase processing of amyloid precursor protein (APP) and decreases beta-secretase cleavage that leads to amyloid-beta formation. Here, we investigated the effect of retinoic acid on the two putative alpha-secretases, the disintegrin metalloproteinases ADAM10 and TACE, and the beta-site cleaving enzyme BACE1, in human neuroblastoma SH-SY5Y cells. Western blot analysis showed that exposure to retinoic acid resulted in significantly increased levels of ADAM10 and TACE, suggesting that regulation of alpha-secretases causes the effects on APP processing. The presence of the phosphatidylinositol 3-kinase inhibitor LY 294002 selectively reduced the effect on ADAM10 protein levels but not on ADAM10 mRNA levels as determined by RT-PCR. On the other hand, the effect on TACE was shown to be dependent on protein kinase C, since it was completely blocked in the presence of the inhibitor bisindolylmaleimide XI. Our data indicate that different signalling pathways are involved in retinoic acid-induced up-regulation of the secretases.

    Biochemical and biophysical research communications 2008;365;2;298-303

  • Stepwise dynamics of epitaxially growing single amyloid fibrils.

    Kellermayer MS, Karsai A, Benke M, Soós K and Penke B

    Department of Biophysics, Faculty of Medicine, University of Pécs, Szigeti út 12, H-7624, Pécs, Hungary. miklos.kellermayer.jr@aok.pte.hu

    The assembly mechanisms of amyloid fibrils, tissue deposits in a variety of degenerative diseases, is poorly understood. With a simply modified application of the atomic force microscope, we monitored the growth, on mica surface, of individual fibrils of the amyloid beta25-35 peptide with near-subunit spatial and subsecond temporal resolution. Fibril assembly was polarized and discontinuous. Bursts of rapid (up to 300-nm(-1)) growth phases that extended the fibril by approximately 7 nm or its integer multiples were interrupted with pauses. Stepwise dynamics were also observed for amyloid beta1-42 fibrils growing on graphite, suggesting that the discontinuous assembly mechanisms may be a general feature of epitaxial amyloid growth. Amyloid assembly may thus involve fluctuation between a fast-growing and a blocked state in which the fibril is kinetically trapped because of intrinsic structural features. The used scanning-force kymography method may be adapted to analyze the assembly dynamics of a wide range of linear biopolymers.

    Proceedings of the National Academy of Sciences of the United States of America 2008;105;1;141-4

  • Mint3/X11gamma is an ADP-ribosylation factor-dependent adaptor that regulates the traffic of the Alzheimer's Precursor protein from the trans-Golgi network.

    Shrivastava-Ranjan P, Faundez V, Fang G, Rees H, Lah JJ, Levey AI and Kahn RA

    Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322-3050, USA.

    Beta-amyloid peptides (Abeta) are the major component of plaques in brains of Alzheimer's patients, and are they derived from the proteolytic processing of the beta-amyloid precursor protein (APP). The movement of APP between organelles is highly regulated, and it is tightly connected to its processing by secretases. We proposed previously that transport of APP within the cell is mediated in part through its sorting into Mint/X11-containing carriers. To test our hypothesis, we purified APP-containing vesicles from human neuroblastoma SH-SY5Y cells, and we showed that Mint2/3 are specifically enriched and that Mint3 and APP are present in the same vesicles. Increasing cellular APP levels increased the amounts of both APP and Mint3 in purified vesicles. Additional evidence supporting an obligate role for Mint3 in traffic of APP from the trans-Golgi network to the plasma membrane include the observations that depletion of Mint3 by small interference RNA (siRNA) or mutation of the Mint binding domain of APP changes the export route of APP from the basolateral to the endosomal/lysosomal sorting route. Finally, we show that increased expression of Mint3 decreased and siRNA-mediated knockdowns increased the secretion of the neurotoxic beta-amyloid peptide, Abeta(1-40). Together, our data implicate Mint3 activity as a critical determinant of post-Golgi APP traffic.

    Funded by: NIA NIH HHS: AG-025688; NIGMS NIH HHS: GM-077569, GM-67226; NINDS NIH HHS: NS-42599

    Molecular biology of the cell 2008;19;1;51-64

  • The extended tau haplotype and the age of onset of dementia in Down syndrome.

    Jones EL, Margallo-Lana M, Prasher VP and Ballard CG

    Wolfson Centre for Age-Related Disease, Guy's Campus, King's College London, London, UK. emma.3.jones@kcl.ac.uk

    Most people with Down syndrome (DS) develop Alzheimer's disease (AD). The extended tau haplotype has been linked to AD. In this study, we examined the haplotype's effect on the age of onset of AD in DS.

    Methods: People with DS were assessed for dementia. Genotyping was performed for the extended tau haplotype, APOE and a polymorphism in APP, attt(5-8).

    Results: Haplotype frequencies vary between those developing AD before 45 and those developing dementia after this age (p = 0.03). H1/H2 individuals are more likely to develop dementia before 45 than H1/H1 individuals (OR = 3, 95% CI = 1.01-8.91).

    Conclusion: Even in a condition driven by excess amyloid pathology, factors affecting tau are also important and should be considered as potential treatment targets.

    Dementia and geriatric cognitive disorders 2008;26;3;199-202

  • Abeta42 mutants with different aggregation profiles induce distinct pathologies in Drosophila.

    Iijima K, Chiang HC, Hearn SA, Hakker I, Gatt A, Shenton C, Granger L, Leung A, Iijima-Ando K and Zhong Y

    Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, USA. Koichi.Iijima@jefferson.edu

    Aggregation of the amyloid-beta-42 (Abeta42) peptide in the brain parenchyma is a pathological hallmark of Alzheimer's disease (AD), and the prevention of Abeta aggregation has been proposed as a therapeutic intervention in AD. However, recent reports indicate that Abeta can form several different prefibrillar and fibrillar aggregates and that each aggregate may confer different pathogenic effects, suggesting that manipulation of Abeta42 aggregation may not only quantitatively but also qualitatively modify brain pathology. Here, we compare the pathogenicity of human Abeta42 mutants with differing tendencies to aggregate. We examined the aggregation-prone, EOFAD-related Arctic mutation (Abeta42Arc) and an artificial mutation (Abeta42art) that is known to suppress aggregation and toxicity of Abeta42 in vitro. In the Drosophila brain, Abeta42Arc formed more oligomers and deposits than did wild type Abeta42, while Abeta42art formed fewer oligomers and deposits. The severity of locomotor dysfunction and premature death positively correlated with the aggregation tendencies of Abeta peptides. Surprisingly, however, Abeta42art caused earlier onset of memory defects than Abeta42. More remarkably, each Abeta induced qualitatively different pathologies. Abeta42Arc caused greater neuron loss than did Abeta42, while Abeta42art flies showed the strongest neurite degeneration. This pattern of degeneration coincides with the distribution of Thioflavin S-stained Abeta aggregates: Abeta42Arc formed large deposits in the cell body, Abeta42art accumulated preferentially in the neurites, while Abeta42 accumulated in both locations. Our results demonstrate that manipulation of the aggregation propensity of Abeta42 does not simply change the level of toxicity, but can also result in qualitative shifts in the pathology induced in vivo.

    PloS one 2008;3;2;e1703

  • Association between deposition of beta-amyloid and pathological prion protein in sporadic Creutzfeldt-Jakob disease.

    Debatin L, Streffer J, Geissen M, Matschke J, Aguzzi A and Glatzel M

    Institute of Neuropathology, University Hospital Zurich, Zurich, Switzerland.

    Background: Alzheimer's disease (AD) and prion diseases such as sporadic Creutzfeldt-Jakob disease (sCJD) share common features concerning their molecular pathogenesis and neuropathological presentation and the coexistence of AD and CJD in patients suggest an association between the deposition of the proteolytically processed form of the amyloid precursor protein, beta-amyloid (Abeta), which deposits in AD, and the abnormal form of the prion protein, PrP(Sc), which deposits in sCJD.

    Methods: We have characterized sCJD patients (n = 14), AD patients (n = 5) and nondemented controls (n = 5) with respect to the deposition of PrP(Sc) and Abeta morphologically, biochemically and genetically and correlated these findings to clinical data.

    Results: sCJD-diseased individuals with abundant deposits of Abeta present with a specific clinicopathological profile, defined by higher age at disease onset, long disease duration, a genetic profile and only minimal amounts of PrP(Sc) in the cerebellum.

    Conclusion: The co-occurrence of pathological changes typical for sCJD and AD in combination with the inverse association between accumulation of Abeta and PrP(Sc) in a subgroup of sCJD patients is indicative of common pathways involved in the generation or clearance of Abeta and PrP(Sc) in a subgroup of sCJD patients.

    Neuro-degenerative diseases 2008;5;6;347-54

  • Beta-amyloid oligomers affect the structure and function of the postsynaptic region: role of the Wnt signaling pathway.

    Dinamarca MC, Colombres M, Cerpa W, Bonansco C and Inestrosa NC

    Centro de Regulación Celular y Patología Joaquín V. Luco, MIFAB, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.

    Background: Alzheimer's disease (AD) is the most prevalent neurodegenerative disease in the growing population of elderly people. Synaptic dysfunction is an early manifestation of AD. The cellular mechanism by which beta-amyloid peptide (Abeta) affects synapses remains unclear. Abeta oligomers target synapses in cultured rat hippocampal neurons suggesting that they play a key role in the regulation of synapses.

    Objective: The aim of this work is to study the effect of Abeta oligomers on the central synapses and the possible role of the Wnt signaling pathway in preventing the Abeta effects.

    Methods: We used rat hippocampal neurons, immunofluorescence and western blot procedures to detect synaptic proteins.

    Results: Abeta oligomers induced a reduction of the postsynaptic density protein 95 (PSD-95) and the NMDA glutamate receptors. We found that Wnt-5a, a noncanonical Wnt ligand, prevents the decrease triggered by Abeta oligomers in the glutamate receptor and PSD-95.

    Conclusion: Altogether, our results suggest that Abeta oligomers decrease the synaptic responses by affecting the postsynaptic region at different levels. The Wnt signaling activation prevents synaptic damage induced by Abeta, which raises the possibility of a new therapeutic intervention for the treatment of synaptic changes observed in AD.

    Neuro-degenerative diseases 2008;5;3-4;149-52

  • Cube copying test in combination with rCBF or CSF A beta 42 predicts development of Alzheimer's disease.

    Buchhave P, Stomrud E, Warkentin S, Blennow K, Minthon L and Hansson O

    Clinical Memory Research Unit, Department of Clinical Sciences Malmö, Lund University, Lund, Sweden.

    The aim was to identify subjects with incipient Alzheimer's disease (AD) among patients with mild cognitive impairment (MCI) using brief cognitive tests.

    Methods: A total of 147 MCI patients were followed for 4-6 years and the incidence of AD was 11.6%/year. At baseline, the cube copying test, clock drawing test, MMSE and measurements of regional cerebral blood flow (rCBF) and cerebrospinal fluid (CSF) beta-amyloid(1-42) (A beta (42)) were performed.

    Results: The cube copying test, but not the clock drawing test, could predict AD among MCI patients with an area under the receiver operating characteristic curve of 0.64 (p < 0.01). The relative risk for future AD was increased in MCI subjects with impaired cube copying test (sex- and age-adjusted hazard ratio = 1.8, p < 0.05) and the incidence of AD was 18.2% in this subgroup. Combining the cube copying test with either rCBF or CSF A beta(42) had additive effects on the risk assessment for future development of AD. MCI patients achieving high scores on both MMSE and cube copying test had a very low risk of developing AD (incidence of AD = 1.6%).

    Conclusion: In conclusion, combinations of the cube copying test with MMSE, rCBF and CSF A beta (42) measurements can identify subgroups of MCI subjects with either substantially reduced or increased risk for future development of AD.

    Dementia and geriatric cognitive disorders 2008;25;6;544-52

  • Dimerization of the transmembrane domain of amyloid precursor proteins and familial Alzheimer's disease mutants.

    Gorman PM, Kim S, Guo M, Melnyk RA, McLaurin J, Fraser PE, Bowie JU and Chakrabartty A

    Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Toronto, Ontario, M5G 2M9, Canada. pgorman@westwindpartners.ca

    Background: Amyloid precursor protein (APP) is enzymatically cleaved by gamma-secretase to form two peptide products, either Abeta40 or the more neurotoxic Abeta42. The Abeta42/40 ratio is increased in many cases of familial Alzheimer's disease (FAD). The transmembrane domain (TM) of APP contains the known dimerization motif GXXXA. We have investigated the dimerization of both wild type and FAD mutant APP transmembrane domains.

    Results: Using synthetic peptides derived from the APP-TM domain, we show that this segment is capable of forming stable transmembrane dimers. A model of a dimeric APP-TM domain reveals a putative dimerization interface, and interestingly, majority of FAD mutations in APP are localized to this interface region. We find that FAD-APP mutations destabilize the APP-TM dimer and increase the population of APP peptide monomers.

    Conclusion: The dissociation constants are correlated to both the Abeta42/Abeta40 ratio and the mean age of disease onset in AD patients. We also show that these TM-peptides reduce Abeta production and Abeta42/Abeta40 ratios when added to HEK293 cells overexpressing the Swedish FAD mutation and gamma-secretase components, potentially revealing a new class of gamma-secretase inhibitors.

    Funded by: NIGMS NIH HHS: GM063919, R01 GM063919-05, R01 GM063919-06, R01 GM063919-07, R01 GM063919-08

    BMC neuroscience 2008;9;17

  • Increased prevalence of significant recurrent headache in preclinical familial Alzheimer's disease mutation carriers.

    Ringman JM, Romano JD, Medina LD, Rodriguez-Agudelo Y, Schaffer B, Varpetian A, Ortiz F, Fitten LJ, Cummings JL and Baloh RW

    Alzheimer's Disease Research Center, UCLA, Los Angeles, CA 90095-7226, USA. jringman@mednet.ucla.edu

    A previous study found a high prevalence of headaches in persons with familial Alzheimer's disease (FAD) due to a PSEN1 mutation. In our study we compared the prevalence of headaches between nondemented FAD mutation carriers (MCs) and non-mutation-carrying controls (NCs).

    Methods: A headache questionnaire that assessed the prevalence of significant headaches and diagnosis of migraine and aura by ICHD-2 criteria was administered to 27 individuals at risk for FAD. Frequency of significant headaches, migraine, and aura were compared between MCs and NCs by chi(2) or Fisher's exact tests.

    Results: Twenty-three subjects were at risk for PSEN1 mutations and 4 for an APP substitution. The majority of subjects were female (23/27). MCs were more likely to report significant recurrent headache than NCs (67 vs. 25%, p = 0.031). Forty percent of MCs had headaches that met criteria for migraine whereas 17% of NCs met such criteria. The tendency for a higher prevalence of headaches in MCs held for different PSEN1 and APP mutations but was not significant unless all families were combined.

    Conclusions: In this population, headache was more common in nondemented FAD MCs than NCs. Possible mechanisms for this include cerebral inflammation, aberrant processing of Notch3, or disrupted intracellular calcium regulation.

    Funded by: NCRR NIH HHS: M01-RR00865; NIA NIH HHS: K08 AG-22228, P50 AG-16570, R01 AG-21055

    Dementia and geriatric cognitive disorders 2008;25;4;380-4

  • Intraneuronal beta-amyloid is a major risk factor--novel evidence from the APP/PS1KI mouse model.

    Bayer TA, Breyhan H, Duan K, Rettig J and Wirths O

    Department of Psychiatry, Division of Molecular Psychiatry, University of Goettingen, Goettingen, Germany. tbayer@gwdg.de

    Accumulating evidence points to an important role of intraneuronal beta-amyloid (Abeta) in the development of Alzheimer's disease (AD), with its typical clinical symptoms like memory impairment and changes in personality. We have previously reported on the Abeta precursor protein and presenilin-1 knock-out (APP/PS1KI) mouse model with abundant intraneuronal Abeta(42) accumulation and a 50% loss of CA1 neurons at 10 months of age. In addition, we observed reduced short- and long-term synaptic plasticity, hippocampal neuron loss, and reduced performance in a working memory task. These observations support a pivotal role of intraneuronal Abeta accumulation as a principal pathological trigger in AD.

    Neuro-degenerative diseases 2008;5;3-4;140-2

  • Mechanism of glial differentiation of neural progenitor cells by amyloid precursor protein.

    Sugaya K

    Burnett College of Biomedical Sciences, University of Central Florida, Orlando, Fla. 32816-2364, USA. ksugaya@mail.ucf.edu

    Background: We found that human neural progenitor cells (HNPCs) exposed to high concentrations of amyloid precursor protein (APP) or transplanted into APP transgenic mice (APP23) primarily differentiated into astrocytes, suggesting that pathological alterations of APP processing in Alzheimer's disease (AD) may prevent neuronal differentiation of HNPCs.

    Objectives: To investigate the mechanism of APP-induced glial differentiation of HNPCs.

    Methods: We treat HNPCs with APP and analyze the expression and phosphorylation of signaling molecules using PCR and Western blots. To confirm the involvement of the factors, RNA interference of the signaling molecule is conducted.

    Results: APP treatment caused inductions of CNTF, gp130 and JAK1 gene expressions, and STAT3 phosphorylation, while silencing of these genes by RNA interference suppressed the glial differentiation of the cells, indicating involvement of the IL-6/gp130 pathway. APP also increased the generation of notch intracellular domain and gene expression of Hes1, indicating that glial differentiation of HNPCs may be mediated by the notch signaling.

    Conclusion: These results indicate that APP may regulate HNPC differentiation through activation of both the IL-6/gp130 and notch signaling pathway. Although the importance of adult neurogenesis is not clear, glial differentiation of HNPCs may cause problems in maintaining normal brain function and may contribute to the AD pathology.

    Neuro-degenerative diseases 2008;5;3-4;170-2

  • Prediction of Alzheimer's disease using a cerebrospinal fluid pattern of C-terminally truncated beta-amyloid peptides.

    Höglund K, Hansson O, Buchhave P, Zetterberg H, Lewczuk P, Londos E, Blennow K, Minthon L and Wiltfang J

    Neurochemistry Lab, Department of Neuroscience and Physiology, Göteborg University, Molndal, Sweden. kina.hoglund@neuro.gu.se

    Background: Identifying individuals at high risk of developing Alzheimer's disease (AD) is important for future therapeutic strategies, and there is a clinical need for diagnostic biomarkers to identify incipient AD.

    Objective: The aim of the present study was to investigate if the AD-associated Abeta peptide pattern recently found in cerebrospinal fluid (CSF) could discriminate between patients with incipient AD and those with stable mild cognitive impairment (MCI) by analyzing CSF from patients with MCI at baseline.

    Methods: The levels of Abeta(1-37, -38, -39, -40, -42) were analyzed by Abeta-SDS-PAGE/immunoblot in CSF from 19 healthy controls, 25 patients with stable MCI and from 25 patients with MCI who later developed AD during 4- to 6-year follow-up.

    Results: All healthy controls and 20 out of 22 patients who developed AD were correctly classified by their baseline Abeta peptide pattern. In 9 out of 25 stable MCI patients, the pattern indicated incipient AD in spite of clinical nonconversion. Interestingly, these individuals had apolipoprotein E genotypes and CSF levels of tau and phospho-tau that are known to be associated with high risk of AD.

    Conclusion: Altogether, our study reveals the novel finding that the Abeta peptide pattern is able to predict AD in patients with MCI with a sensitivity of 91% and specificity of 64%. The specificity would increase to 94% if the high-risk patients in the stable MCI cohort developed AD during extended follow-up.

    Neuro-degenerative diseases 2008;5;5;268-76

  • Soluble beta-amyloid leads to mitochondrial defects in amyloid precursor protein and tau transgenic mice.

    Eckert A, Hauptmann S, Scherping I, Rhein V, Müller-Spahn F, Götz J and Müller WE

    Neurobiology Research Laboratory, Psychiatric University Clinics, Basel, Switzerland. anne.eckert@upkbs.ch

    Background: Mitochondrial dysfunction has been identified in neurodegenerative disorders including Alzheimer's disease, where accumulation of beta-amyloid (Abeta) and oxidative stress seem to play central roles in the pathogenesis, by probably directly leading to mitochondrial dysfunction.

    Objective: In order to study the in vivo effect of Abeta load during aging, we evaluated the mitochondrial function of brain cells from transgenic mice bearing either mutant amyloid precursor protein (tgAPP) or mutant amyloid precursor protein and mutant PS1 (tgAPP/PS1) as well as from nontransgenic wild-type littermates. tgAPP mice exhibit onset of Abeta plaques at an age of 6 months, but the intracellular soluble Abeta load is already increased at 3 months of age. In contrast, onset of Abeta plaques starts at an age of 3 months in tgAPP/PS1 mice. In addition, we investigated the effects of different Abeta preparations on mitochondrial function of brain cells from tau transgenic mice.

    Results: Of note, mitochondrial damage such as reduced mitochondrial membrane potential and ATP levels can already be detected in the brains from these mice before the onset of plaques. In agreement with our findings in tgAPP mice, soluble Abeta induced mitochondrial dysfunction in brain cells from tau transgenic mice.

    Conclusion: Our results indicate that mitochondrial dysfunction is exacerbated by the presence of soluble Abeta species as a very early event during pathogenesis.

    Neuro-degenerative diseases 2008;5;3-4;157-9

  • The binding constant for amyloid Abeta40 peptide interaction with human serum albumin.

    Rózga M, Kłoniecki M, Jabłonowska A, Dadlez M and Bal W

    Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland.

    Human serum albumin (HSA) is the major carrier of Abeta peptides in blood plasma. 1:1 interaction stoichiometries were established in previous indirect antibody-based studies for both Abeta40 and Abeta42, but corresponding binding constants were not provided. In this study we applied direct titrations of HSA with Abeta40 monitored using circular dichroism spectroscopy and obtained a dissociation constant (K(d)) of 5+/-1 microM for a HSA complex with Abeta40. The interaction resulted in an increase of the alpha-helical contents in the complex, compared to its components, which is quantitatively consistent with the known ability of Abeta40 to adopt a partially alpha-helical conformation in a hydrophobic environment. The relevance of these findings for the role of HSA in Abeta physiology is discussed.

    Biochemical and biophysical research communications 2007;364;3;714-8

  • Huperzine A regulates amyloid precursor protein processing via protein kinase C and mitogen-activated protein kinase pathways in neuroblastoma SK-N-SH cells over-expressing wild type human amyloid precursor protein 695.

    Peng Y, Lee DY, Jiang L, Ma Z, Schachter SC and Lemere CA

    Center for Neurologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Harvard New Research Building, Room 636F, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.

    Alpha-secretase (alpha-secretase), cleaves the amyloid precursor protein (APP) within the amyloid-beta (Abeta) sequence, resulting in the release of a secreted fragment of APP (alphaAPPs) and precluding Abeta generation. We investigated the effects of the acetylcholinesterase inhibitor, huperzine A (Hup A), on APP processing and Abeta generation in human neuroblastoma SK-N-SH cells overexpressing wild-type human APP695. Hup A dose-dependently (0-10 microM) increased alphaAPPs release. Therefore, we evaluated two alpha-secretase candidates, a disintegrin and metalloprotease (ADAM) 10 and ADAM17 in Hup A-induced non-amyloidogenic APP metabolism. Hup A enhanced the level of ADAM10, and the inhibitor of tumor necrosis factor-alpha converting enzyme (TACE)/ADAM17 inhibited the Hup A-induced rise in alphaAPPs levels, further suggesting Hup A directed APP metabolism toward the non-amyloidogenic alpha-secretase pathway. Hup A had no effect on Abeta generation in this cell line. The steady-state levels of full-length APP and cell viability were unaffected by Hup A. Alpha-APPs release induced by Hup A treatment was significantly reduced by muscarinic acetylcholine receptor antagonists (particularly by an M1 antagonist), protein kinase C (PKC) inhibitors, GF109203X and calphostin C, and the mitogen-activated kinase kinase (MEK) inhibitors, U0126 and PD98059. Furthermore, Hup A markedly increased the phosphorylation of p44/p42 mitogen-activated protein (MAP) kinase, which was blocked by treatment with U0126 and PD98059. In addition, Hup A inhibited acetylcholinesterase activity by 20% in neuroblastoma cells. Our results indicate that the activation of muscarinic acetylcholine receptors, PKC and MAP kinase may be involved in Hup A-induced alphaAPPs secretion in neuroblastoma cells and suggest multiple pharmacological mechanisms of Hup A regarding the treatment of Alzheimer's disease (AD).

    Neuroscience 2007;150;2;386-95

  • Abeta(1-40)-induced secretion of matrix metalloproteinase-9 results in sAPPalpha release by association with cell surface APP.

    Talamagas AA, Efthimiopoulos S, Tsilibary EC, Figueiredo-Pereira ME and Tzinia AK

    Institute of Biology, National Centre for Scientific Research "Demokritos", 15310 Agia Paraskevi, Athens, Greece.

    To understand matrix metalloproteinase-9 (MMP-9) involvement in Alzheimer's disease, we examined mechanisms mediating increased expression of MMP-9 in the presence of Abeta(1-40) and the role of MMP-9 on amyloid precursor protein (APP) processing. Up-regulation of MMP-9 expressed by SK-N-SH cells in the presence of Abeta(1-40) was mediated by alpha(3)beta(1) and alpha(2)beta(1) integrin receptors. Overexpression of MMP-9 or treatment of HEK/APP695 cells with activated recombinant MMP-9 resulted in enhanced secretion of soluble APP (sAPPalpha), a product of alpha-secretase cleavage, and reduction of Abeta release. MMP-9 effect was enhanced by phorbol 12-mysistrate-13-acetate (PMA), an alpha-secretase activator and inhibited by EDTA or SB-3CT, an MMP-9 inhibitor. Additionally, immunoprecipitation and confocal microscopy demonstrated that MMP-9 and APP695 were associated on the cell surface. These results indicate that Abeta peptide increases MMP-9 secretion through integrins; MMP-9 then directly processes cell surface APP695 with an alpha-secretase like activity, substantially reducing the levels of secreted Abeta peptide.

    Neurobiology of disease 2007;28;3;304-15

  • Abeta 1-42 induces mild endoplasmic reticulum stress in an aggregation state-dependent manner.

    Chafekar SM, Hoozemans JJ, Zwart R, Baas F and Scheper W

    Neurogenetics Laboratory, University of Amsterdam, Amsterdam, The Netherlands.

    Alzheimer's disease (AD) is characterized by the aggregation of misfolded proteins. Previously we reported activation of the unfolded protein response (UPR) in AD neurons. A potential source for UPR activation in AD neurons may be the increased levels of beta-amyloid (Abeta). In this study, we used preparations enriched in oligomeric or fibrillar Abeta (1-42) to investigate the role of the conformational state of Abeta in UPR activation in differentiated neuroblastoma cells. Both oligomeric and fibrillar Abeta (1-42) do not induce BiP expression to the extent that it can be detected in a pool of cells. However, using a fluorescent UPR reporter cell line that allows analysis of individual cells, we demonstrated mild activation of the UPR by oligomeric but not fibrillar Abeta (1-42). We showed that oligomeric Abeta (1-42) is significantly more toxic to cells primed for UPR than is fibrillar Abeta (1-42), indicating that activation of the UPR contributes to oligomer-specific Abeta (1-42) toxicity. Because UPR activation is observed in AD brain at a stage that precedes the massive fibrillar Abeta deposition and tangle formation, this may indicate a role for nonfibrillar Abeta in the induction of the UPR in AD neurons.

    Antioxidants & redox signaling 2007;9;12;2245-54

  • Cystatin C inhibits amyloid-beta deposition in Alzheimer's disease mouse models.

    Mi W, Pawlik M, Sastre M, Jung SS, Radvinsky DS, Klein AM, Sommer J, Schmidt SD, Nixon RA, Mathews PM and Levy E

    Nathan S. Kline Institute, Orangeburg, New York 10962, USA.

    Using transgenic mice expressing human cystatin C (encoded by CST3), we show that cystatin C binds soluble amyloid-beta peptide and inhibits cerebral amyloid deposition in amyloid-beta precursor protein (APP) transgenic mice. Cystatin C expression twice that of the endogenous mouse cystatin C was sufficient to substantially diminish amyloid-beta deposition. Thus, cystatin C has a protective role in Alzheimer's disease pathogenesis, and modulation of cystatin C concentrations may have therapeutic implications for the disease.

    Funded by: NIA NIH HHS: AG017617; NINDS NIH HHS: NS42029

    Nature genetics 2007;39;12;1440-2

  • Cystatin C modulates cerebral beta-amyloidosis.

    Kaeser SA, Herzig MC, Coomaraswamy J, Kilger E, Selenica ML, Winkler DT, Staufenbiel M, Levy E, Grubb A and Jucker M

    Department of Cellular Neurology, Hertie-Institute for Clinical Brain Research, University of Tübingen, Otfried-Müller Strasse 27, D-72076 Tübingen, Germany.

    The CST3 Thr25 allele of CST3, which encodes cystatin C, leads to reduced cystatin C secretion and conveys susceptibility to Alzheimer's disease. Here we show that overexpression of human cystatin C in brains of APP-transgenic mice reduces cerebral amyloid-beta deposition and that cystatin C binds amyloid-beta and inhibits its fibril formation. Our results suggest that cystatin C concentrations modulate cerebral amyloidosis risk and provide an opportunity for genetic risk assessment and therapeutic interventions.

    Nature genetics 2007;39;12;1437-9

  • Lipoprotein receptor-related protein-1 mediates amyloid-beta-mediated cell death of cerebrovascular cells.

    Wilhelmus MM, Otte-Höller I, van Triel JJ, Veerhuis R, Maat-Schieman ML, Bu G, de Waal RM and Verbeek MM

    Department of Neurology and Alzheimer Center, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.

    Inefficient clearance of A beta, caused by impaired blood-brain barrier crossing into the circulation, seems to be a major cause of A beta accumulation in the brain of late-onset Alzheimer's disease patients and hereditary cerebral hemorrhage with amyloidosis Dutch type. We observed association of receptor for advanced glycation end products, CD36, and low-density lipoprotein receptor (LDLR) with cerebral amyloid angiopathy in both Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis Dutch type brains and increased low-density lipoprotein receptor-related protein-1 (LRP-1) expression by perivascular cells in cerebral amyloid angiopathy. We investigated if these A beta receptors are involved in A beta internalization and in A beta-mediated cell death of human cerebrovascular cells and astrocytes. Expression of both the LRP-1 and LDLR by human brain pericytes and leptomeningeal smooth muscle cells, but not by astrocytes, increased on incubation with A beta. Receptor-associated protein specifically inhibited A beta-mediated up-regulation of LRP-1, but not of LDLR, and receptor-associated protein also decreased A beta internalization and A beta-mediated cell death. We conclude that especially LRP-1 and, to a minor extent, LDLR are involved in A beta internalization by and A beta-mediated cell death of cerebral perivascular cells. Although perivascular cells may adapt their A beta internalization capacity to the levels of A beta present, saturated LRP-1/LDLR-mediated uptake of A beta results in degeneration of perivascular cells.

    Funded by: NIA NIH HHS: AG027924, R01 AG027924

    The American journal of pathology 2007;171;6;1989-99

  • Amyloid beta-protein precursor juxtamembrane domain regulates specificity of gamma-secretase-dependent cleavages.

    Ren Z, Schenk D, Basi GS and Shapiro IP

    Elan Pharmaceuticals, Inc., South San Francisco, California 94080, USA.

    Amyloid beta-protein (Abeta), the major component of cerebral plaques associated with Alzheimer disease, is derived from amyloid beta-protein precursor (APP) through sequential proteolytic cleavage involving beta- and gamma-secretase. The intramembrane cleavage of APP by gamma-secretase occurs at two major sites, gamma and epsilon, although the temporal and/or mechanistic relationships between these cleavages remain unknown. In our attempt to address this issue, we uncovered an important regulatory role for the APP luminal juxtamembrane domain. We demonstrated in cell-based assays that domain replacements in this region can greatly reduce secreted Abeta resulting from gamma-cleavage without affecting the epsilon-cleavage product. This Abeta reduction is likely due to impaired proteolysis at the gamma-cleavage site. Further analyses with site-directed mutagenesis identified two juxtamembrane residues, Lys-28 and Ser-26 (Abeta numbering), as the critical determinants for efficient intramembrane proteolysis at the gamma-site. Consistent with the growing evidence that epsilon-cleavage of APP precedes gamma-processing, longer Abeta species derived from the gamma-cleavage-deficient substrates were detected intracellularly. These results indicate that the luminal juxtamembrane region of APP is an important regulatory domain that modulates gamma-secretase-dependent intramembrane proteolysis, particularly in differentiating gamma- and epsilon-cleavages.

    The Journal of biological chemistry 2007;282;48;35350-60

  • Fe65 stimulates proteolytic liberation of the beta-amyloid precursor protein intracellular domain.

    Wiley JC, Smith EA, Hudson MP, Ladiges WC and Bothwell M

    Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, USA.

    The beta-amyloid precursor protein (APP)-binding protein Fe65 is involved in APP nuclear signaling and several steps in APP proteolytic processing. In this study, we show that Fe65 stimulates gamma-secretase-mediated liberation of the APP intracellular domain (AICD). The mechanism of Fe65-mediated stimulation of AICD formation appears to be through enhanced production of the carboxyl-terminal fragment substrates of gamma-secretase and direct stimulation of processing by gamma-secretase. The stimulatory capacity of Fe65 is isoform-dependent, as the non-neuronal and a2 isoforms promote APP processing more effectively than the exon 9 inclusive neuronal form of Fe65. Intriguingly, Fe65 stimulation of AICD production appears to be inversely related to pathogenic beta-amyloid production as the Fe65 isoforms profoundly stimulate AICD production and simultaneously decrease Abeta42 production. Despite the capacity of Fe65 to stimulate gamma-secretase-mediated APP proteolysis, it does not rescue the loss of proteolytic function associated with the presenilin-1 familial Alzheimer disease mutations. These data suggest that Fe65 regulation of APP proteolysis may be integrally associated with its nuclear signaling function, as all antecedent proteolytic steps prior to release of Fe65 from the membrane are fostered by the APP-Fe65 interaction.

    Funded by: NIA NIH HHS: AG21127, AG26476

    The Journal of biological chemistry 2007;282;46;33313-25

  • Soluble Abeta inhibits specific signal transduction cascades common to the insulin receptor pathway.

    Townsend M, Mehta T and Selkoe DJ

    Department of Neurology, Harvard Medical School and Center for Neurologic Diseases, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.

    Numerous studies have now shown that the amyloid beta-protein (Abeta), the principal component of cerebral plaques in Alzheimer disease, rapidly and potently inhibits certain forms of synaptic plasticity. The amyloid (or Abeta) hypothesis proposes that the continuous disruption of normal synaptic physiology by Abeta contributes to the development of Alzheimer disease. However, there is little consensus about how Abeta mediates this inhibition at the molecular level. Using mouse primary hippocampal neurons, we observed that a brief treatment with cell-derived, soluble, human Abeta disrupted the activation of three kinases (Erk/MAPK, CaMKII, and the phosphatidylinositol 3-kinase-activated protein Akt/protein kinase B) that are required for long term potentiation, whereas two other kinases (protein kinase A and protein kinase C) were stimulated normally. An antagonist of the insulin receptor family of tyrosine kinases was found to mimic the pattern of Abeta-mediated kinase inhibition. We then found that soluble Abeta binds to the insulin receptor and interferes with its insulin-induced autophosphorylation. Taken together, these data demonstrate that physiologically relevant levels of naturally secreted Abeta interfere with insulin receptor function in hippocampal neurons and prevent the rapid activation of specific kinases required for long term potentiation.

    Funded by: NIA NIH HHS: AG027443; NINDS NIH HHS: T32 NS07484-04

    The Journal of biological chemistry 2007;282;46;33305-12

  • Effect of different salt ions on the propensity of aggregation and on the structure of Alzheimer's abeta(1-40) amyloid fibrils.

    Klement K, Wieligmann K, Meinhardt J, Hortschansky P, Richter W and Fändrich M

    Leibniz-Institut für Altersforschung, Beutenbergstrasse 11, D-07745 Jena, Germany.

    The formation of amyloid fibrils and other polypeptide aggregates depends strongly on the physico-chemical environment. One such factor affecting aggregation is the presence and concentration of salt ions. We have examined the effects of salt ions on the aggregation propensity of Alzheimer's Abeta(1-40) peptide and on the structure of the dissolved and of the fibrillar peptide. All salts examined promote aggregation strongly. The most pronounced effect is seen within the cationic series, i.e. for MgCl2. Evaluation of different possible explanations suggests that Abeta(1-40) aggregation depends on direct interaction between ions and Abeta(1-40) peptide, and correlates with ion-induced changes of the surface tension. Salts have profound effects on the fibril structure. In the presence of salts, fibrils are associated with smaller diameters, narrower crossover distances and lower amide I maxima. Since Abeta(1-40) aggregation responds to salts in a manner unlike that for other polypeptides, such as glucagon, beta2-microglobulin or alpha-synuclein; these data argue that there is no fully uniform way in which salts affect aggregation of different polypeptide chains. These observations are important for understanding and predicting aggregation on the basis of simple physico-chemical properties.

    Journal of molecular biology 2007;373;5;1321-33

  • Involvement of prostaglandin E2 in production of amyloid-beta peptides both in vitro and in vivo.

    Hoshino T, Nakaya T, Homan T, Tanaka K, Sugimoto Y, Araki W, Narita M, Narumiya S, Suzuki T and Mizushima T

    Graduate School of Medical and Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.

    Amyloid-beta peptides (Abeta), generated by proteolysis of the beta-amyloid precursor protein (APP) by beta- and gamma-secretases, play an important role in the pathogenesis of Alzheimer disease (AD). Inflammation is also believed to be integral to the pathogenesis of AD. Here we show that prostaglandin E(2) (PGE(2)), a strong inducer of inflammation, stimulates the production of Abeta in cultured human embryonic kidney (HEK) 293 or human neuroblastoma (SH-SY5Y) cells, both of which express a mutant type of APP. We have demonstrated using subtype-specific agonists that, of the four main subtypes of PGE(2) receptors (EP(1-4)), EP(4) receptors alone or EP(2) and EP(4) receptors together are responsible for this PGE(2)-stimulated production of Abeta in HEK293 or SH-SY5Y cells, respectively. An EP(4) receptor antagonist suppressed the PGE(2)-stimulated production of Abeta in HEK293 cells. This stimulation was accompanied by an increase in cellular cAMP levels, and an analogue of cAMP stimulated the production of Abeta, demonstrating that increases in the cellular level of cAMP are responsible for the PGE(2)-stimulated production of Abeta. Immunoblotting experiments and direct measurement of gamma-secretase activity suggested that PGE(2)-stimulated production of Abeta is mediated by activation ofgamma-secretase but not of beta-secretase. Transgenic mice expressing the mutant type of APP showed lower levels of Abeta in the brain, when they were crossed with mice lacking either EP(2) or EP(4) receptors, suggesting that PGE(2)-mediated activation of EP(2) and EP(4) receptors is involved in the production of Abeta in vivo and in the pathogenesis of AD.

    The Journal of biological chemistry 2007;282;45;32676-88

  • Three histidine residues of amyloid-beta peptide control the redox activity of copper and iron.

    Nakamura M, Shishido N, Nunomura A, Smith MA, Perry G, Hayashi Y, Nakayama K and Hayashi T

    Department of Chemistry, Asahikawa Medical College, Asahikawa 078-8510, Japan. nmasao@asahikawa-med. ac.jp

    Zinc, iron and copper are concentrated in senile plaques of Alzheimer disease. Copper and iron catalyze the Fenton-Haber-Weiss reaction, which likely contributes to oxidative stress in neuronal cells. In this study, we found that ascorbate oxidase activity and the intensity of ascorbate radicals measured using ESR spectroscopy, generated by free Cu(II), was decreased in the presence of amyloid-beta (Abeta), the major component of senile plaques. Specifically, the ascorbate oxidase activity was strongly inhibited (85% decrease) in the presence of Abeta1-16 or Abeta1-42, whereas it was only slightly inhibited in the presence of Abeta1-12 or Abeta25-35 (<20% inhibition). Ascorbate-dependent hydroxyl radical generation by free Cu(II) decreased in the presence of Abeta in the identical order of Abeta1-42, Abeta1-16 > Abeta1-12 and was abolished in the presence of 2-fold molar excess glycylhystidyllysine (GHK). Ascorbate oxidase activity and ascorbate-dependent hydroxyl radical generation by free Fe(III) were inhibited by Abeta1-42, Abeta1-16, and Abeta1-12. Although Cu(II)-Abeta shows a significant SOD-like activity, the rate constant for the reaction of superoxide with Cu(II)-Abeta was much slower than that with SOD. Overall, our results suggest that His6, His13, and His14 residues of Abeta1-42 control the redox activity of transition metals present in senile plaques.

    Biochemistry 2007;46;44;12737-43

  • Decreased insulin-receptor signaling promotes the autophagic degradation of beta-amyloid peptide in C. elegans.

    Florez-McClure ML, Hohsfield LA, Fonte G, Bealor MT and Link CD

    Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado 80309, USA. maria.mcclure@colorado.edu

    Autophagy is a conserved membrane trafficking pathway that mediates the delivery of cytoplasmic substrates to the lysosome for degradation. Impaired autophagic function is implicated in the pathology of various neurodegenerative diseases. We have generated transgenic C. elegans that express human beta-amyloid peptide (Abeta) in order to examine the mechanism(s) of Abeta-toxicity. In this model, Abeta expression causes autophagosome accumulation, thereby mimicking a pathology found in brains of Alzheimer's disease patients. Furthermore, we demonstrate that decreased insulin-receptor signaling [using the daf-2(e1370) mutation] suppresses Abeta-induced paralysis by a mechanism that requires autophagy. Surprisingly, the daf-2 mutation also decreases Abeta-induced autophagosome accumulation. These observations can be explained by a model in which decreased insulin-receptor signaling promotes the maturation of autophagosomes into degradative autolysosomes, whereas Abeta impairs this process. Consistent with this model, we find that RNAi-mediated knock-down of lysosomal components results in enhanced Abeta-toxicity and autophagosome accumulation. Also, Abeta; daf-2(e1370) nematodes contain more lysosomes than either Abeta or control strains. Finally, we demonstrate that decreased insulin-receptor signaling promotes the autophagic degradation of Abeta.

    Funded by: NIA NIH HHS: AG12423; NICHD NIH HHS: HD007289

    Autophagy 2007;3;6;569-80

  • Molecular and cellular mechanisms for Alzheimer's disease: understanding APP metabolism.

    Zhang YW and Xu H

    Institute for Biomedical Research, Xiamen University, China.

    Alzheimer's disease (AD) is the most common neurodegenerative disease associated with aging. One important pathologic feature of AD is the formation of extracellular senile plaques in the brain, whose major components are small peptides called beta-amyloid (Abeta) that are derived from beta-amyloid precursor protein (APP) through sequential cleavages by beta-secretase and gamma-secretase. Because of the critical role of Abeta in the pathogenesis of AD, unraveling the cellular and molecular events underlying APP/Abeta metabolism has been and remains, of paramount importance to AD research. In this article we will focus on the regulation of APP metabolism leading to Abeta generation. We will review current knowledge of the secretases (alpha-, beta-, and gamma-secretases) involved in APP processing and various molecular and cellular mechanisms underlying intracellular trafficking of APP, which is a highly regulated process and whose disturbance has direct impacts on the production of Abeta.

    Current molecular medicine 2007;7;7;687-96

  • Pathogenic role of mitochondrial [correction of mitochondral] amyloid-beta peptide.

    Chen JX and Yan SD

    Harvey Cushing Institutes of Neuroscience, North Shore-Long Island Jewish Health System, Great Neck, NY 11021, USA. jchen1@nshs.edu

    Metabolic dysfunction is one of the early features in Alzheimer's disease (AD) affected brain. Amyloid-beta peptide (Abeta), a major peptide deposited in neuritic plaques, has been considered as an important initiating molecule in the pathogenesis of AD. However, the pathogenic role of Abeta remains to be determined. Here, we review current studies showing that progressive accumulation of Abeta occurs within the mitochondria of both transgenic mice overexpressing mutant Abeta peptide precursor protein and autopsied brains from AD patients. Interaction of Abeta with Abeta-binding alcohol dehydrogenase (ABAD), a short-chain alcohol dehydrogenase in the mitochondrial matrix, leads to mitochondrial dysfunction evidenced by increased reactive oxygen species generation, mitochondrial membrane permeability formation and caspase-3-like activity induction, and decreased activities of the Krebs cycle. These effects can be blocked by intracellular transduction of the ABAD decoy peptide. We hypothesize that Abeta-induced and mitochondria-dependent cytotoxic pathways might play an important role in AD pathogenesis and could be a potential therapeutic target.

    Funded by: NIA NIH HHS: AG16736, P01 AG17490, P50 AG08702

    Expert review of neurotherapeutics 2007;7;11;1517-25

  • Downregulation of myosin II-B by siRNA alters the subcellular localization of the amyloid precursor protein and increases amyloid-beta deposition in N2a cells.

    Massone S, Argellati F, Passalacqua M, Armirotti A, Melone L, d'Abramo C, Marinari UM, Domenicotti C, Pronzato MA and Ricciarelli R

    Department of Experimental Medicine, University of Genoa, Via L.B. Alberti 2, 16132 Genoa, Italy.

    The Alzheimer's disease (AD) brain pathology is characterized by extracellular deposits of amyloid-beta (Abeta) peptides and intraneuronal fibrillar structures. These pathological features may be functionally linked, but the mechanism by which Abeta accumulation relates to neuronal degeneration is still poorly understood. Abeta peptides are fragments cleaved from the amyloid precursor protein (APP), a transmembrane protein ubiquitously expressed in the nervous system. Although the proteolytic processing of APP has been implicated in AD, the physiological function of APP and the subcellular site of APP cleavages remain unknown. The overall structure of the protein and its fast anterograde transport along the axon support the idea that APP functions as a vesicular receptor for cytoskeletal motor proteins. In the current study, we test the hypothesis that myosin II, important contributor to the cytoskeleton of neuronal cells, may influence the trafficking and/or the processing of APP. Our results demonstrate that downregulation of myosin II-B, the major myosin isoform in neurons, is able to increase Abeta deposition, concomitantly altering the subcellular localization of APP. These new insights might be important for the understanding of the function of APP and provide a novel conceptual framework in which to analyze its pathological role.

    Biochemical and biophysical research communications 2007;362;3;633-8

  • Familial Alzheimer's disease mutations alter the stability of the amyloid beta-protein monomer folding nucleus.

    Grant MA, Lazo ND, Lomakin A, Condron MM, Arai H, Yamin G, Rigby AC and Teplow DB

    Division of Molecular and Vascular Medicine, Beth Israel Deaconess Medical Center, and Department of Medicine, Harvard Medical School, Boston, MA 02215, USA.

    Amyloid beta-protein (Abeta) oligomers may be the proximate neurotoxins in Alzheimer's disease (AD). Recently, to elucidate the oligomerization pathway, we studied Abeta monomer folding and identified a decapeptide segment of Abeta, (21)Ala-(22)Glu-(23)Asp-(24)Val-(25)Gly-(26)Ser-(27)Asn-(28)Lys-(29)Gly-(30)Ala, within which turn formation appears to nucleate monomer folding. The turn is stabilized by hydrophobic interactions between Val-24 and Lys-28 and by long-range electrostatic interactions between Lys-28 and either Glu-22 or Asp-23. We hypothesized that turn destabilization might explain the effects of amino acid substitutions at Glu-22 and Asp-23 that cause familial forms of AD and cerebral amyloid angiopathy. To test this hypothesis, limited proteolysis, mass spectrometry, and solution-state NMR spectroscopy were used here to determine and compare the structure and stability of the Abeta(21-30) turn within wild-type Abeta and seven clinically relevant homologues. In addition, we determined the relative differences in folding free energies (DeltaDeltaG(f)) among the mutant peptides. We observed that all of the disease-associated amino acid substitutions at Glu-22 or Asp-23 destabilized the turn and that the magnitude of the destabilization correlated with oligomerization propensity. The Ala21Gly (Flemish) substitution, outside the turn proper (Glu-22-Lys-28), displayed a stability similar to that of the wild-type peptide. The implications of these findings for understanding Abeta monomer folding and disease causation are discussed.

    Funded by: NIA NIH HHS: AG027818; NINDS NIH HHS: NS038328

    Proceedings of the National Academy of Sciences of the United States of America 2007;104;42;16522-7

  • Germ line origin and somatic mutations determine the target tissues in systemic AL-amyloidosis.

    Enqvist S, Sletten K, Stevens FJ, Hellman U and Westermark P

    Department of Genetics and Pathology, Uppsala University, Uppsala, Sweden.

    Background: Amyloid is insoluble aggregated proteins deposited in the extra cellular space. About 25 different proteins are known to form amyloid in vivo and are associated with severe diseases such as Alzheimer's disease, prion diseases and type-2 diabetes. Light chain (AL) -amyloidosis is unique among amyloid diseases in that the fibril protein, a monoclonal immunoglobulin light chain, varies between individuals and that no two AL-proteins with identical primary structures have been described to date. The variability in tissue distribution of amyloid deposits is considerably larger in systemic AL-amyloidosis than in any other form of amyloidosis. The reason for this variation is believed to be based on the differences in properties of the amyloidogenic immunoglobulin light chain. However, there is presently no known relationship between the structure of an AL-protein and tissue distribution.

    We compared the pattern of amyloid deposition in four individuals with amyloid protein derived from variable light chain gene O18-O8, the source of a high proportion of amyloidogenic light chains, and in whom all or most of the fibril protein had been determined by amino acid sequencing. In spite of great similarities between the structures of the proteins, there was a pronounced variability in deposition pattern. We also compared the tissue distribution in these four individuals with that of four other patients with AL-amyloid derived from the L2-L16 gene. Although the interindividual variations were pronounced, liver and kidney involvement was much more evident in the latter four.

    We conclude that although the use of a specific gene influences the tissue distribution of amyloid, each light chain exhibits one or more determinants of organ-specificity, which originate from somatic mutations and post-translational modifications. Eventual identification of such determinants could lead to improved treatment of patients with AL amyloidosis.

    PloS one 2007;2;10;e981

  • Structure of Alzheimer's disease amyloid precursor protein copper-binding domain at atomic resolution.

    Kong GK, Adams JJ, Cappai R and Parker MW

    Biota Structural Biology Laboratory, St Vincent's Institute, 9 Princes Street, Fitzroy, Victoria 3065, Australia.

    Amyloid precursor protein (APP) plays a central role in the pathogenesis of Alzheimer's disease, as its cleavage generates the Abeta peptide that is toxic to cells. APP is able to bind Cu2+ and reduce it to Cu+ through its copper-binding domain (CuBD). The interaction between Cu2+ and APP leads to a decrease in Abeta production and to alleviation of the symptoms of the disease in mouse models. Structural studies of CuBD have been undertaken in order to better understand the mechanism behind the process. Here, the crystal structure of CuBD in the metal-free form determined to ultrahigh resolution (0.85 A) is reported. The structure shows that the copper-binding residues of CuBD are rather rigid but that Met170, which is thought to be the electron source for Cu2+ reduction, adopts two different side-chain conformations. These observations shed light on the copper-binding and redox mechanisms of CuBD. The structure of CuBD at atomic resolution provides an accurate framework for structure-based design of molecules that will deplete Abeta production.

    Acta crystallographica. Section F, Structural biology and crystallization communications 2007;63;Pt 10;819-24

  • The amyloid-beta precursor protein is phosphorylated via distinct pathways during differentiation, mitosis, stress, and degeneration.

    Muresan Z and Muresan V

    Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ 07103, USA. muresazo@umdnj.edu

    Phosphorylation of amyloid-beta precursor protein (APP) at Thr(668) is a normal process linked to neurite extension and anterograde transport of vesicular cargo. By contrast, increased phosphorylation of APP is a pathological trait of Alzheimer's disease. APP is overexpressed in Down's syndrome, a condition that occasionally leads to increased APP phosphorylation, in cultured cells. Whether phosphorylation of APP in normal versus high APP conditions occurs by similar or distinct signaling pathways is not known. Here, we addressed this problem using brainstem-derived neurons (CAD cells). CAD cells that ectopically overexpress APP frequently show features of degenerating neurons. We found that, in degenerating cells, APP is hyperphosphorylated and colocalizes with early endosomes. By contrast, in normal CAD cells, phosphorylated APP (pAPP) is excluded from endosomes, and localizes to the Golgi apparatus and to transport vesicles within the neurites. Whereas the neuritic APP is phosphorylated by c-Jun NH(2)-terminal kinase through a pathway that is modulated by glycogen synthase kinase 3beta, the endosomal pAPP in degenerated CAD cells results from activation of cyclin-dependent kinase 5. Additional signaling pathways, leading to APP phosphorylation, become active during stress and mitosis. We conclude that distinct pathways of APP phosphorylation operate in proliferating, differentiating, stressed, and degenerating neurons.

    Funded by: NIGMS NIH HHS: R01GM068596

    Molecular biology of the cell 2007;18;10;3835-44

  • Abeta40 is associated with cognitive function, body fat and physical fitness in healthy older adults.

    Leahey TM, Myers TA, Gunstad J, Glickman E, Spitznagel MB, Alexander T and Juvancic-Heltzel J

    Department of Psychology, Kent State University, Kent, OH 44240, USA.

    Body composition and obesity-related lifestyle factors are associated with increased risk for Alzheimer's disease (AD). Amyloid beta (Abeta) is a peptide integral in the pathogenesis of AD. Abeta has been shown to be related to body fat and exercise in younger adults; however, no study to date has examined the possible relationship among Abeta, body composition and fitness indices in older adults.

    Thirty-five older adults without significant neurological or psychiatric history, underwent fasting blood draw and completed cognitive testing and body composition and physical fitness assessments.

    Results: Partial correlations showed Abeta levels were inversely related to cognitive function, body fat and physical fitness measures.

    Conclusions: Findings indicate Abeta is associated with cognitive function, body fat and physical fitness in neurologically healthy older adults. Further work is needed to clarify possible mechanisms, particularly longitudinal studies.

    Nutritional neuroscience 2007;10;5-6;205-9

  • AP-2 participates in the transcriptional control of the amyloid precursor protein (APP) gene in oral squamous cell carcinoma.

    Provenzano MJ, Yu L, Hitchler MJ, Fitzgerald MP, Robinson RA, Wayne S, Ver Meer M and Domann FE

    Department of Otolaryngology - Head and Neck Surgery, University of Iowa, Iowa City, IA 52242-1181, USA.

    Amyloid precursor protein (APP) has been implicated in squamous cell carcinoma. In this study we show that forced expression of the transcription factor activating protein 2alpha (AP-2alpha) results in significantly increased steady state levels of APP mRNA in human keratinocytes. Sequence analysis of the 5' end of the human APP gene revealed five putative binding sites for AP-2, suggesting that APP is a direct target for transactivation by AP-2. AP-2 protein bound at least 3 of these putative promoter elements in vitro as determined by electrophoretic mobility shift assay. Chromatin immunoprecipitation (ChIP) analysis showed that these binding sites were occupied by AP-2 in cells, thus indicating the relevance to AP-2 binding in vivo. We then analyzed APP and AP-2 mRNA and protein expression in squamous cell carcinoma tumor samples. Analysis of RNA extracted from human tissue showed a significant positive correlation between AP-2alpha and APP mRNA expression. Immunohistochemical staining of tumor samples also demonstrated a positive correlation which was substantiated through western blot studies. Taken together, these findings demonstrate a role for the transcription factor AP-2alpha in the regulation of APP gene expression in human keratinocytes.

    Funded by: NCI NIH HHS: 5P01CA66081, 5P20CA103672, 5P30CA086862, 5T32CA078586, P01 CA066081, P01 CA066081-09, P20 CA103672, R01 CA073612, R01 CA073612-10, R01CA73612, T32 CA078586, T32 CA078586-08; NIDCD NIH HHS: 5T32DC000040, T32 DC000040, T32 DC000040-16

    Experimental and molecular pathology 2007;83;2;277-82

  • APP locus duplication in a Finnish family with dementia and intracerebral haemorrhage.

    Rovelet-Lecrux A, Frebourg T, Tuominen H, Majamaa K, Campion D and Remes AM

    INSERM U614, IFRMP, Faculty of Medicine, Rouen, France.

    Journal of neurology, neurosurgery, and psychiatry 2007;78;10;1158-9

  • Beta-amyloid (Abeta40, Abeta42) binding to modified LDL accelerates macrophage foam cell formation.

    Schulz B, Liebisch G, Grandl M, Werner T, Barlage S and Schmitz G

    Institute for Clinical Chemistry and Laboratory Medicine, University of Regensburg, 93042 Regensburg, Germany.

    Apart from its role as a risk factor in arteriosclerosis, plasma cholesterol is increasingly recognized to play a major role in the pathogenesis of Alzheimer's disease (AD). Moreover, alterations of intracellular cholesterol metabolism in neuronal and vascular cells are of considerable importance for the understanding of AD. Cellular cholesterol accumulation enhances the deposition of insoluble beta-amyloid peptides, which is considered a hallmark in the pathogenesis of AD. In order to test the hypothesis, whether exogenous beta-amyloid peptides (Abeta42, Abeta40) might contribute to cellular cholesterol accumulation by opsonization of lipoproteins, we compared the binding and uptake of native LDL, enzymatically modified LDL (E-LDL), copper oxidized LDL (Ox-LDL) and HDL as control, preincubated either in the absence or presence of Abeta42 or Abeta40, by human monocytes or monocyte-derived macrophages. Incubation of monocytes and macrophages with Abeta-lipoprotein-complexes lead to increased cellular free and esterified cholesterol when compared to non-opsonized lipoproteins, except for HDL. Furthermore, the cellular uptake of these complexes regulated Abeta-receptors such as FPRL-1 or LRP/CD91. In summary, our results suggest that Abeta42 and Abeta40 act as potent opsonins for LDL, E-LDL and Ox-LDL and enhance cellular cholesterol accumulation as well as Abeta-deposition in vessel wall macrophages.

    Biochimica et biophysica acta 2007;1771;10;1335-44

  • Fe65 does not stabilize AICD during activation of transcription in a luciferase assay.

    Huysseune S, Kienlen-Campard P and Octave JN

    Université Catholique de Louvain, Center for Neurosciences, Laboratoire de Pharmacologie (FARL 5410), Avenue Hippocrate 54, B-1200 Brussels, Belgium.

    The APP intracellular domain (AICD) could be involved in signaling via interaction with the adaptor protein Fe65, and with the histone acetyl transferase Tip60. However, the real function of AICD and Fe65 in regulation of transcription remains controversial. In this study, the human APPGal4 fusion protein was expressed in CHO cells and the transcriptional activity of AICDGal4 was measured in a luciferase-based reporter assay. AICDGal4 was stabilized by expression of Fe65 and levels of AICDGal4 controlled luciferase activity. On the contrary, when human APP was expressed in CHO cells, coexpression of Fe65 increased luciferase activity without affecting the amount of AICD fragment. AICD produced from APP was protected from degradation by orthophenanthroline, but not by lactacystine, indicating that AICD is not a substrate of the chymotryptic activity of the proteasome. It is concluded that Fe65 can control luciferase activity without stabilizing the labile AICD fragment.

    Biochemical and biophysical research communications 2007;361;2;317-22

  • HtrA2 regulates beta-amyloid precursor protein (APP) metabolism through endoplasmic reticulum-associated degradation.

    Huttunen HJ, Guénette SY, Peach C, Greco C, Xia W, Kim DY, Barren C, Tanzi RE and Kovacs DM

    Neurobiology of Disease Laboratory, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.

    Alzheimer disease-associated beta-amyloid peptide is generated from its precursor protein APP. By using the yeast two-hybrid assay, here we identified HtrA2/Omi, a stress-responsive chaperone-protease as a protein binding to the N-terminal cysteinerich region of APP. HtrA2 coimmunoprecipitates exclusively with immature APP from cell lysates as well as mouse brain extracts and degrades APP in vitro. A subpopulation of HtrA2 localizes to the cytosolic side of the endoplasmic reticulum (ER) membrane where it contributes to ER-associated degradation of APP together with the proteasome. Inhibition of the proteasome results in accumulation of retrotranslocated forms of APP and increased association of APP with HtrA2 and Derlin-1 in microsomal membranes. In cells lacking HtrA2, APP holoprotein is stabilized and accumulates in the early secretory pathway correlating with elevated levels of APP C-terminal fragments and increased Abeta secretion. Inhibition of ER-associated degradation (either HtrA2 or proteasome) promotes binding of APP to the COPII protein Sec23 suggesting enhanced trafficking of APP out of the ER. Based on these results we suggest a novel function for HtrA2 as a regulator of APP metabolism through ER-associated degradation.

    The Journal of biological chemistry 2007;282;38;28285-95

  • Enhancing Th2 immune responses against amyloid protein by a DNA prime-adenovirus boost regimen for Alzheimer's disease.

    Kim HD, Jin JJ, Maxwell JA and Fukuchi K

    Department of Cancer Biology and Pharmacology, University of Illinois College of Medicine at Peoria, P.O. Box 1649, Peoria, IL 61656, USA.

    Accumulation of aggregated amyloid beta-protein (Abeta) in the brain is thought to be the initiating event leading to neurodegeneration and dementia in Alzheimer's disease (AD). Therefore, therapeutic strategies that clear accumulated Abeta and/or prevent Abeta production and its aggregation are predicted to be effective against AD. Immunization of AD mouse models with synthetic Abeta prevented or reduced Abeta load in the brain and ameliorated their memory and learning deficits. The clinical trials of Abeta immunization elicited immune responses in only 20% of AD patients and caused T-lymphocyte meningoencephalitis in 6% of AD patients. In attempting to develop safer vaccines, we previously demonstrated that an adenovirus vector, AdPEDI-(Abeta1-6)11, which encodes 11 tandem repeats of Abeta1-6 can induce anti-inflammatory Th2 immune responses in mice. Here, we investigated whether a DNA prime-adenovirus boost regimen could elicit a more robust Th2 response using AdPEDI-(Abeta1-6)11 and a DNA plasmid encoding the same antigen. All mice (n=7) subjected to the DNA prime-adenovirus boost regimen were positive for anti-Abeta antibody, while, out of 7 mice immunized with only AdPEDI-(Abeta1-6)11, four mice developed anti-Abeta antibody. Anti-Abeta titers were indiscernible in mice (n=7) vaccinated with only DNA plasmid. The mean anti-Abeta titer induced by the DNA prime-adenovirus boost regimen was approximately 7-fold greater than that by AdPEDI-(Abeta1-6)11 alone. Furthermore, anti-Abeta antibodies induced by the DNA prime-adenovirus boost regimen were predominantly of the IgG1 isotype. These results indicate that the DNA prime-adenovirus boost regimen can enhance Th2-biased responses with AdPEDI-(Abeta1-6)11 in mice and suggest that heterologous prime-boost strategies may make AD immunotherapy more effective in reducing accumulated Abeta.

    Funded by: NINDS NIH HHS: NS43947, R01 NS043947-01, R01 NS043947-02, R01 NS043947-03, R01 NS043947-04, R01 NS043947-05

    Immunology letters 2007;112;1;30-8

  • Aberrant excitatory neuronal activity and compensatory remodeling of inhibitory hippocampal circuits in mouse models of Alzheimer's disease.

    Palop JJ, Chin J, Roberson ED, Wang J, Thwin MT, Bien-Ly N, Yoo J, Ho KO, Yu GQ, Kreitzer A, Finkbeiner S, Noebels JL and Mucke L

    Gladstone Institute of Neurological Disease, San Francisco, CA 94158, USA. jpalop@gladstone.ucsf.edu

    Neural network dysfunction may play an important role in Alzheimer's disease (AD). Neuronal circuits vulnerable to AD are also affected in human amyloid precursor protein (hAPP) transgenic mice. hAPP mice with high levels of amyloid-beta peptides in the brain develop AD-like abnormalities, including cognitive deficits and depletions of calcium-related proteins in the dentate gyrus, a region critically involved in learning and memory. Here, we report that hAPP mice have spontaneous nonconvulsive seizure activity in cortical and hippocampal networks, which is associated with GABAergic sprouting, enhanced synaptic inhibition, and synaptic plasticity deficits in the dentate gyrus. Many Abeta-induced neuronal alterations could be simulated in nontransgenic mice by excitotoxin challenge and prevented in hAPP mice by blocking overexcitation. Aberrant increases in network excitability and compensatory inhibitory mechanisms in the hippocampus may contribute to Abeta-induced neurological deficits in hAPP mice and, possibly, also in humans with AD.

    Funded by: NCRR NIH HHS: RR018928; NIA NIH HHS: AG011385, AG022074, AG023501; NICHD NIH HHS: HD024064; NINDS NIH HHS: K08 NS054811, K08 NS054811-02, NS041787, NS29709, NS39074, NS54811

    Neuron 2007;55;5;697-711

  • Amyloid-beta-peptide reduces the expression level of mitochondrial cytochrome oxidase subunits.

    Hong WK, Han EH, Kim DG, Ahn JY, Park JS and Han BG

    Biobank for Health Sciences, Center for Genome Sciences, National Institute of Health, Korea Center for Disease Control and Prevention (KCDC), 194, Tongil-Ro, Eunpyung-Ku, Seoul 122-701, Korea.

    Mitochondrial dysfunction is an important cause of neurological disorder including Alzheimer's disease (AD). Mitochondria play a key role in the generation of reactive oxygen species (ROS), resulting in oxidative damage to neuronal cell and cellular compartments in the AD brain. Cytotoxicity induced by amyloid-beta (Abeta), a protein fragment of 25-35 amino acids in amyloid plaques has been shown to have neuro-toxic properties. They seem to involve mitochondrial dysfunction, but the underlying mechanisms are not clearly understood. The purpose of this study was to assess whether Abeta induced mitochondrial dysfunction involves changes in cytochrome c oxidase (COX) expression. We measured the activities of COX after expose of SK-N-SH cells (a human neuroblastoma cell line) to Abeta. We found that levels of mRNAs expressing mitochondrial COX subunits decreased significantly in Abeta-treated SK-N-SH cells in a dose-dependent manner. Human mitochondrial transcription factor-1 (TFAM) mRNA level also decreased after Abeta-treatment. These results suggest that Abeta modulates the mitochondrial gene expression through a decrease in TFAM.

    Neurochemical research 2007;32;9;1483-8

  • Clearance of amyloid-beta by circulating lipoprotein receptors.

    Sagare A, Deane R, Bell RD, Johnson B, Hamm K, Pendu R, Marky A, Lenting PJ, Wu Z, Zarcone T, Goate A, Mayo K, Perlmutter D, Coma M, Zhong Z and Zlokovic BV

    Frank P. Smith Laboratory for Neuroscience and Neurosurgical Research, Department of Neurosurgery, University of Rochester Medical School, Rochester, New York 14642, USA.

    Low-density lipoprotein receptor-related protein-1 (LRP) on brain capillaries clears amyloid beta-peptide (Abeta) from brain. Here, we show that soluble circulating LRP (sLRP) provides key endogenous peripheral 'sink' activity for Abeta in humans. Recombinant LRP cluster IV (LRP-IV) bound Abeta in plasma in mice and Alzheimer's disease-affected humans with compromised sLRP-mediated Abeta binding, and reduced Abeta-related pathology and dysfunction in a mouse model of Alzheimer disease, suggesting that LRP-IV can effectively replace native sLRP and clear Abeta.

    Funded by: NIA NIH HHS: P50 AG005681, P50 AG05681, R37 AG023084, R37 AG023084-02; NINDS NIH HHS: R01 NS034467, R01 NS034467-07, R37 NS034467, R37 NS34467

    Nature medicine 2007;13;9;1029-31

  • Effects of beta-amyloid peptide and estrogen on platelet mitochondrial function of Sprague-Dawley rats.

    Xu J, Shi C, Li Q, Lam WP, Wai MS and Yew DT

    Department of Anatomy, Zhongshan School of Medicine, Sun Yat-Sen University Guangzhou, Guangdong 510080, China.

    Beta-amyloid peptide (Abeta) peptides play a central role in the development of Alzheimer's disease. They are known to induce mitochondrial dysfunction and caspase activation, resulting in apoptosis of neuronal cells. In the present experiment, an Abeta-induced damage model of platelets was established to observe the effects of Abeta, estradiol benzoate (EB) and genistein on platelets and platelet mitochondria. It was found that after the addition of Abeta, platelet number, platelet mitochondrial membrane potential (DeltaPsim) and adenosine triphosphate (ATP) content were lowered while no protective effects of EB and genistein had been observed. The platelets could serve as a biomarker for detection of mitochondrial function and age related disease.

    Platelets 2007;18;6;460-8

  • [Evaluation of amyloid-beta by the E280A mutation in presenilin gene].

    Villegas A, Castañeda MM, Arias LF, Vieco B, Lopera F and Bedoya G

    Grupo de Neurociencias de Antioquia, Universidad de Antioquia, Medellín, Colombia. villegas@neurociencias.udea.edu.co

    Introduction: The E280A mutation of the presenilin 1 gene has been found to be the most common associate in Alzheimers patients with a family history of this disease. Presenilin 1 is a critical component of the g-secretase complex and plays an essential role in the production of amyloid-beta peptide. This peptide has been strongly associated with the physiopathology of the disease.

    Objective: The E280A mutation in the presenilin 1 was investigated for increased production of amyloid-beta , as a response to gain in gamma-secretase function.

    Levels of systemic amyloid-beta were measured with congo red staining and immuno-histochemistry of the tissues of affected cadavers, compared with non-affected cadavers. The 40 and 42 amino acid amyloid-beta levels were quantified by ELISA assay in CHO cell cultures. The amyloid precursor protein expressed by the cultures was detected by transfection with the cDNAs of presenilin 1 carrying the M146L, E280A, DE9 y L392V mutations.

    Results: Protein deposits were found in all tissues investigatged, but only a few with beta -amyloid deposition. No differences were observed in the amount or location of amyloid-beta between affected and unaffected cadavers. Not increase was noted in the production of amyloid-beta from the CHO cells transfected with cDNA from any of the mutations of presenilin 1.

    Conclusions: The E280A mutation in the presenilin 1 gene was not associated with the increased production of amyloid-beta in non-neuronal peripheral tissues, or in the in vitro model. This is in contrast to the expectation in a gamma-secretase gain of function.

    Biomedica : revista del Instituto Nacional de Salud 2007;27;3;372-84

  • Severe amyloid deposition in mammary glands of familial amyloid polyneuropathy patients.

    Tokuda T, Takei Y, Takayama B, Hoshii Y and Ikeda S

    Department of Internal Medicine (Neurology and Rheumatology), Shinshu University School of Medicine, Matsumoto, Japan.

    Clinical pictures of familial amyloid polyneuropathy (FAP) vary considerably, perhaps because of the many gene mutations of transthyretin (TTR), but even in patients having the most common mutation of TTR (the substitution of methionine for valine at position 30 (ATTRVal30Met)), the age of onset ranges from the late 20s to the early 60s. Although genetic anticipation has been considered to play a role in producing this wide range of ages of onset, the precise pathogenesis is incompletely understood. It has been experimentally shown that murine systemic AA and AApoAII amyloidoses can be transmitted by ingestion of amyloid fibrils themselves or amyloid-like pathological agents. In this study, we examined biopsied mammary glands obtained from three female ATTRVal30Met FAP patients who were of gestation age. Amyloid deposition was commonly seen in the glands and, in the two patients with apparent FAP symptoms, heavy deposits of amyloid surrounded many lactiferous alveoli and ducts, where some deposits of amyloid actually faced the central lumens. These findings raise the possibility that milk from FAP mothers contains ATTR-derived amyloid fibrils and/or fragments, which might be causally related to the development of genetic anticipation in this disease.

    Amyloid : the international journal of experimental and clinical investigation : the official journal of the International Society of Amyloidosis 2007;14;3;249-53

  • Amyolid precursor protein mediates presynaptic localization and activity of the high-affinity choline transporter.

    Wang B, Yang L, Wang Z and Zheng H

    Huffington Center on Aging and Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.

    The key pathological features of Alzheimer's disease include synaptic dysfunction, profound changes in the cholinergic system, and deposition of beta-amyloid peptides generated by proteolytic processing of the amyloid-beta precursor protein (APP). However, the pathways linking APP with synaptic activity and cholinergic neuronal function are poorly understood. We report here that APP is essential in regulating the presynaptic expression and activity of the high-affinity choline transporter (CHT), a molecule that mediates the rate-limiting step of cholinergic synaptic transmission in both the neuromuscular junction and central cholinergic neurons. Loss of APP leads to aberrant localization of CHT at the neuromuscular synapses and reduced CHT activity at cholinergic projections. At the cellular level, we show that APP and CHT can be found in Rab5-positive endosomal compartments and that APP affects CHT endocytosis. Furthermore, we demonstrate that APP interacts with CHT through the C-terminal domain, providing support for a specific and direct regulation of CHT by APP through protein-protein interactions. These results identify a physiological activity of APP in cholinergic neurons, and our data indicate that deregulation of APP function may contribute to cholinergic impairment and AD pathogenesis.

    Funded by: NIA NIH HHS: AG20670, AG21141, T32 AG000183; NINDS NIH HHS: NS40039

    Proceedings of the National Academy of Sciences of the United States of America 2007;104;35;14140-5

  • Insensitivity to Abeta42-lowering nonsteroidal anti-inflammatory drugs and gamma-secretase inhibitors is common among aggressive presenilin-1 mutations.

    Czirr E, Leuchtenberger S, Dorner-Ciossek C, Schneider A, Jucker M, Koo EH, Pietrzik CU, Baumann K and Weggen S

    Emmy Noether Research Group, Mainz, Germany.

    Abeta42-lowering nonsteroidal anti-inflammatory drugs (NSAIDs) constitute the founding members of a new class of gamma-secretase modulators that avoid side effects of pan-gamma-secretase inhibitors on NOTCH processing and function, holding promise as potential disease-modifying agents for Alzheimer disease (AD). These modulators are active in cell-free gamma-secretase assays indicating that they directly target the gamma-secretase complex. Additional support for this hypothesis was provided by the observation that certain mutations in presenilin-1 (PS1) associated with early-onset familial AD (FAD) change the cellular drug response to Abeta42-lowering NSAIDs. Of particular interest is the PS1-DeltaExon9 mutation, which provokes a pathogenic increase in the Abeta42/Abeta40 ratio and dramatically reduces the cellular response to the Abeta42-lowering NSAID sulindac sulfide. This FAD PS1 mutant is unusual as a splice-site mutation results in deletion of amino acids Thr(291)-Ser(319) including the endoproteolytic cleavage site of PS1, and an additional amino acid exchange (S290C) at the exon 8/10 splice junction. By genetic dissection of the PS1-DeltaExon9 mutation, we now demonstrate that a synergistic effect of the S290C mutation and the lack of endoproteolytic cleavage is sufficient to elevate the Abeta42/Abeta40 ratio and that the attenuated response to sulindac sulfide results partially from the deficiency in endoproteolysis. Importantly, a wider screen revealed that a diminished response to Abeta42-lowering NSAIDs is common among aggressive FAD PS1 mutations. Surprisingly, these mutations were also partially unresponsive to gamma-secretase inhibitors of different structural classes. This was confirmed in a mouse model with transgenic expression of the PS1-L166P mutation, in which the potent gamma-secretase inhibitor LY-411575 failed to reduce brain levels of soluble Abeta42. In summary, these findings highlight the importance of genetic background in drug discovery efforts aimed at gamma-secretase, suggesting that certain AD mouse models harboring aggressive PS mutations may not be informative in assessing in vivo effects of gamma-secretase modulators and inhibitors.

    The Journal of biological chemistry 2007;282;34;24504-13

  • Influence of Hypericum perforatum extract and its single compounds on amyloid-beta mediated toxicity in microglial cells.

    Kraus B, Wolff H, Heilmann J and Elstner EF

    Chair of Phytopathology, Technical University of Munich, Wissenschaftszentrum Weihenstephan, Am Hochanger 2, Freising, Germany. birgitl.kraus@chemie.uni-regensburg.de

    As immunocompetent cells of the brain, microglia are able to counteract the damaging effects of amyloid-beta in Alzheimer's disease by phagocytosis-mediated clearance of protein aggregates. The survival and health of microglia are therefore critical for attenuating and preventing neurodegenerative diseases. In a microglial cell line pretreated with St. John's wort (Hypericum perforatum L.) extract (HPE), the cell death evoked by treatment with amyloid-beta (25-35) and (1-40) was attenuated significantly in a dose-dependent manner. Investigation of the single compounds in the extract revealed that the flavanols (+)-catechin and (-)-epicatechin increase cell viability slightly, whereas the flavonol quercetin and its glycosides rutin, hyperosid and quercitrin showed no effect on cell viability. In contrast, at the same concentration, the flavonoids reduced the formation of amyloid-induced reactive oxygen species in microglia, indicating that improvement of cell viability by the catechins is not correlated to the antioxidant activity. No influence of HPE on the capacity of microglia to phagocytose sub-toxic concentrations of fibrillar amyloid-beta (1-40) was observed. Other experiments showed that HPE, (+)-catechin and (-)-epicatechin can alter cellular membrane fluidity and thereby may have a beneficial effect on cell health. Our findings provide in vitro evidence that treatment especially with the complex plant extract HPE may restore or improve microglial viability and thereby attenuate amyloid-beta mediated toxicity in Alzheimer's disease.

    Life sciences 2007;81;11;884-94

  • Accelerating amyloid-beta fibrillization reduces oligomer levels and functional deficits in Alzheimer disease mouse models.

    Cheng IH, Scearce-Levie K, Legleiter J, Palop JJ, Gerstein H, Bien-Ly N, Puoliväli J, Lesné S, Ashe KH, Muchowski PJ and Mucke L

    Gladstone Institute of Neurological Disease, San Francisco, California 94158, USA.

    Many proteins suspected of causing neurodegenerative diseases exist in diverse assembly states. For most, it is unclear whether shifts from one state to another would be helpful or harmful. We used mutagenesis to change the assembly state of Alzheimer disease (AD)-associated amyloid-beta (Abeta) peptides. In vitro, the "Arctic" mutation (AbetaE22G) accelerated Abeta fibrillization but decreased the abundance of nonfibrillar Abeta assemblies, compared with wild-type Abeta. In human amyloid precursor protein (hAPP) transgenic mice carrying mutations adjacent to Abeta that increase Abeta production, addition of the Arctic mutation markedly enhanced the formation of neuritic amyloid plaques but reduced the relative abundance of a specific nonfibrillar Abeta assembly (Abeta*56). Mice overexpressing Arctic mutant or wild-type Abeta had similar behavioral and neuronal deficits when they were matched for Abeta*56 levels but had vastly different plaque loads. Thus, Abeta*56 is a likelier determinant of functional deficits in hAPP mice than fibrillar Abeta deposits. Therapeutic interventions that reduce Abeta fibrils at the cost of augmenting nonfibrillar Abeta assemblies could be harmful.

    Funded by: NCRR NIH HHS: RR 18928-01; NIA NIH HHS: AG011385, AG022074, AG023501; NINDS NIH HHS: NS33249

    The Journal of biological chemistry 2007;282;33;23818-28

  • Production, purification and functional validation of human secreted amyloid precursor proteins for use as neuropharmacological reagents.

    Turner PR, Bourne K, Garama D, Carne A, Abraham WC and Tate WP

    Department of Biochemistry, University of Otago, Dunedin, New Zealand.

    The secreted fragment of the amyloid precursor protein (sAPPalpha) generated following cleavage by alpha-secretase is an important mediator of cell function and is both neurotrophic and neuroprotective. HEK 293T cells have been stably integrated with a fragment of the APP gene to produce and secrete either sAPPalpha, or the alternative cleavage product sAPPbeta. Heparin binding domains on the proteins have been utilised to develop a one-step fast-performance-liquid-chromatography (FPLC) purification of sAPPs from the conditioned media. Immunoblotting analyses with a sAPP specific antibody coupled with highly sensitive silver staining techniques have validated the expression and purification strategy. Functional activity of the purified fragments was demonstrated by their ability to protect COS-7 and SH-SY5Y (neuroblastoma) cells against the adverse effects of glucose deprivation in a cell viability assay. The purified sAPPs also activated the NFkappaB transcription factor in COS-7 cells transfected with a luciferase reporter plasmid, with sAPPalpha the more potent activator as expected. The simple protocol to produce these mammalian expressed proteins will facilitate their use as potential neuropharmacological reagents in the elucidation of biochemical pathways modulated by sAPPs, and in the study of Alzheimer's disease mechanisms in general.

    Journal of neuroscience methods 2007;164;1;68-74

  • Redox reactions of copper complexes formed with different beta-amyloid peptides and their neuropathological [correction of neuropathalogical] relevance.

    Jiang D, Men L, Wang J, Zhang Y, Chickenyen S, Wang Y and Zhou F

    Department of Chemistry and Biochemistry, California State University, Los Angeles, Los Angeles, California 90032, USA.

    The binding stoichiometry between Cu(II) and the full-length beta-amyloid Abeta(1-42) and the oxidation state of copper in the resultant complex were determined by electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) and cyclic voltammetry. The same approach was extended to the copper complexes of Abeta(1-16) and Abeta(1-28). A stoichiometric ratio of 1:1 was directly observed, and the oxidation state of copper was deduced to be 2+ for all of the complexes, and residues tyrosine-10 and methionine-35 are not oxidized in the Abeta(1-42)-Cu(II) complex. The stoichiometric ratio remains the same in the presence of more than a 10-fold excess of Cu(II). Redox potentials of the sole tyrosine residue and the Cu(II) center were determined to be ca. 0.75 and 0.08 V vs Ag/AgCl [or 0.95 and 0.28 V vs normal hydrogen electrode (NHE)], respectively. More importantly, for the first time, the Abeta-Cu(I) complex has been generated electrochemically and was found to catalyze the reduction of oxygen to produce hydrogen peroxide. The voltammetric behaviors of the three Abeta segments suggest that diffusion of oxygen to the metal center can be affected by the length and hydrophobicity of the Abeta peptide. The determination and assignment of the redox potentials clarify some misconceptions in the redox reactions involving Abeta and provide new insight into the possible roles of redox metal ions in the Alzheimer's disease (AD) pathogenesis. In cellular environments, the reduction potential of the Abeta-Cu(II) complex is sufficiently high to react with antioxidants (e.g., ascorbic acid) and cellular redox buffers (e.g., glutathione), and the Abeta-Cu(I) complex produced could subsequently reduce oxygen to form hydrogen peroxide via a catalytic cycle. Using voltammetry, the Abeta-Cu(II) complex formed in solution was found to be readily reduced by ascorbic acid. Hydrogen peroxide produced, in addition to its role in damaging DNA, protein, and lipid molecules, can also be involved in the further consumption of antioxidants, causing their depletion in neurons and eventually damaging the neuronal defense system. Another possibility is that Abeta-Cu(II) could react with species involved in the cascade of electron transfer events of mitochondria and might potentially sidetrack the electron transfer processes in the respiratory chain, leading to mitochondrial dysfunction.

    Funded by: NCI NIH HHS: R01 CA101864; NIGMS NIH HHS: GM 08101, S06 GM008101; NIMHD NIH HHS: P20 MD001824, P20 MD001824-01

    Biochemistry 2007;46;32;9270-82

  • Effects of Alzheimer's disease on different cortical layers: the role of intrinsic differences in Abeta susceptibility.

    Romito-DiGiacomo RR, Menegay H, Cicero SA and Herrup K

    Department of Neuroscience, Alzheimer Research Laboratory, Case School of Medicine, Cleveland, Ohio 44106, USA.

    Alzheimer's disease is late life dementia associated with significant neurodegeneration in both cortical and subcortical regions. During the approximately 10 year course of the disease, neurons are lost in a progressive pattern that is relatively consistent among individuals. One example of this is the progression of disease pathology found in both the neocortex and archicortex. In these structures, the earliest problems can be found in superficial cortical layers (II-IV), whereas later the disease advances to involve the deeper cortical layers (V-VI). It is unclear whether these apparent differences in sensitivity are intrinsic to the neurons or imposed by external factors such as the pattern of connections. We used beta-amyloid (Abeta) peptide treatment of cultured mouse neurons as our model system. We show first that, as in hippocampus, dissociated cultures of embryonic cortical neurons are biased toward the survival of cells that were finishing division in the ventricular zone at the time of harvest. Thus, embryonic day 13.5 (E13.5) cultures contain primarily deep-layer neurons whereas E16.5 cultures contain cells destined for upper layers. We use this cell-type specific segregation to our advantage and show, using both differences in gene expression profiles and Abeta survival curves, that deeper layer neurons are significantly more resistant to the toxic effects of Abeta than are cells from the more superficial strata. This suggests that an intrinsic underlying biology drives at least part of the AD progression pattern and that the time of harvest is a crucial variable in the interpretation of any cortical culture experiment.

    Funded by: NINDS NIH HHS: NS20591

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;32;8496-504

  • Stable insertion of Alzheimer Abeta peptide into the ER membrane strongly correlates with its length.

    Lundin C, Johansson S, Johnson AE, Näslund J, von Heijne G and Nilsson I

    Stockholm Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 12, SE-106 91 Stockholm, Sweden.

    Alzheimer's disease is characterized by the deposition of amyloid beta-peptide (Abeta) plaques in the brain. Full-length amyloid-beta precursor protein (APP) is processed by alpha- and beta-secretases to yield soluble APP derivatives and membrane-bound C-terminal fragments, which are further processed by gamma-secretase to a non-amyloidogenic 3 kDa product or to Abeta fragments. As different Abeta fragments contain different parts of the APP transmembrane helix, one may speculate that they are retained more or less efficiently in the membrane. Here, we use the translocon-mediated insertion of different APP-derived polypeptide segments into the endoplasmic reticulum membrane to assess the propensities for membrane retention of Abeta fragments. Our results show a strong correlation between the length of an Abeta-derived segment and its ability to integrate into the microsomal membrane.

    Funded by: NIGMS NIH HHS: GM26494, R01 GM026494, R01 GM026494-26, R01 GM026494-27

    FEBS letters 2007;581;20;3809-13

  • Effects of wild-type and mutant human amyloid precursor protein on cortical afferent network.

    Alpár A, Ueberham U, Seeger G, Arendt T and Gärtner U

    Department of Anatomy, Histology and Embryology, Semmelweis University Medical School, Budapest, Hungary. dralpar@gmx.net

    Alzheimer's disease is characterized by severe neuronal disintegration supposed to be partly associated with amyloid pathology. Recently, we described morphological alterations of pyramidal cell structure in transgenic mice expressing wild-type or mutant human amyloid precursor protein (hAPP) (strains B6-Py8.9 and Tg2576), which are unrelated to direct plaque-associated changes. In this study, we focused on the pattern of cortical afferent connections in these transgenic mice. The quantity of cholinergic afferents is increased in both transgenic lines. Glutamatergic intra- and interhemispheric afferents are augmented in B6-Py8.9 mice but decreased in Tg2576 mice. Furthermore, perisomatic inhibition of pyramidal neurons was found to be reduced in Tg2576 mice. Findings suggest different effects of wild-type and mutant hAPP on neuronal connectivity.

    Neuroreport 2007;18;12;1247-50

  • Upregulation of amyloid precursor protein by platelet-derived growth factor in hippocampal precursor cells.

    Lim JS, Cho H, Hong HS, Kwon H, Mook-Jung I and Kwon YK

    Department of Biology and Life and Nanopharmaceutical Science, Institute of Age-related and Brain Disease, Kyunghee University, Korea.

    Amyloid precursor protein generates the secreted amyloid precursor protein alpha, which protects hippocampal neurons from ischemic injury and facilitates neuronal survival and synaptogenesis in the developing nervous system. Here, we examined whether platelet-derived growth factor regulates the generation of secreted amyloid precursor protein alpha during the neuronal differentiation of hippocampal precursor cells, HiB5. We showed that platelet-derived growth factor promoted amyloid precursor protein production and secreted amyloid precursor protein alpha secretion. These effects of platelet-derived growth factor were diminished by the PI3K-specific inhibitor wortmannin and the protein kinase C-specific inhibitor GF109203X, suggesting the involvement of the PI3K and protein kinase C-signaling pathway. Furthermore, the conditioned media enriched with secreted amyloid precursor protein alpha promoted the survival of HiB5 cells during neuronal differentiation. These results suggest that the neurotrophic effect of platelet-derived growth factor is mediated in part via upregulation of the expression and release of secreted amyloid precursor protein alpha.

    Neuroreport 2007;18;12;1225-9

  • Anti-A beta 1-11 antibody binds to different beta-amyloid species, inhibits fibril formation, and disaggregates preformed fibrils but not the most toxic oligomers.

    Mamikonyan G, Necula M, Mkrtichyan M, Ghochikyan A, Petrushina I, Movsesyan N, Mina E, Kiyatkin A, Glabe CG, Cribbs DH and Agadjanyan MG

    Department of Immunology, The Institute for Molecular Medicine, Huntington Beach, California 92647, USA.

    Different strategies proposed as therapy for Alzheimer disease (AD) have aimed to reduce the level of toxic forms of A beta peptide in the brain. Here, we directly analyze the therapeutic utility of the polyclonal anti-A beta(1-11) antibody induced in 3xTg-AD mice vaccinated with the second generation prototype epitope vaccine. Substoichiometric concentrations of purified anti-A beta(1-11) antibody prevented aggregation of A beta(42) and induced disaggregation of preformed A beta(42) fibrils down to nonfilamentous and nontoxic species. Anti-A beta(1-11) antibody delayed A beta(42) oligomer formation but ultimately appeared to stabilize nonfibrillar conformations, including oligomer-like assemblies. The reduced oligomer-mediated cytotoxicity observed upon preincubation of A beta oligomers with the anti-A beta(1-11) antibody in the absence of oligomer disaggregation suggests a possible oligomer rearrangement in the presence of the antibody. These in vitro observations suggest that preventive vaccination may protect from AD or may delay the onset of the disease, whereas therapeutic vaccination cannot disrupt the toxic oligomers and may only minimally alleviate preexisting AD pathology.

    Funded by: NIA NIH HHS: R01 AG20241, R01 AG020241, R01 AG020241-05; NINDS NIH HHS: NS3I230, R01 NS031230, R01 NS031230-07, R01 NS050895, R01 NS050895-02, R01 NS50895

    The Journal of biological chemistry 2007;282;31;22376-86

  • Expression of APP pathway mRNAs and proteins in Alzheimer's disease.

    Matsui T, Ingelsson M, Fukumoto H, Ramasamy K, Kowa H, Frosch MP, Irizarry MC and Hyman BT

    Alzheimer Disease Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Charlestown, MA 02129, USA.

    In both trisomy 21 and rare cases of triplication of amyloid precursor protein (APP) Alzheimer's disease (AD) pathological changes are believed to be secondary to increased expression of APP. We hypothesized that sporadic AD may also be associated with changes in transcription of APP or its metabolic partners. To address this issue, temporal neocortex of 27 AD and 21 non-demented control brains was examined to assess mRNA levels of APP isoforms (total APP, APP containing the Kunitz protease inhibitor domain [APP-KPI] and APP770) and APP metabolic enzymatic partners (the APP cleaving enzymes beta-secretase [BACE] and presenilin-1 [PS-1], and putative clearance molecules, low-density lipoprotein receptor protein [LRP] and apolipoprotein E [apoE]). Furthermore, we evaluated how changes in APP at the mRNA level affect the amount of Tris buffer extractable APP protein and Abeta40 and 42 peptides in AD and control brains. As assessed by quantitative PCR, APP-KPI (p=0.007), APP770 (p=0.004), PS-1 (p=0.004), LRP (p=0.003), apoE (p=0.0002) and GFAP (p<0.0001) mRNA levels all increased in AD, and there was a shift from APP695 (a neuronal isoform) towards KPI containing isoforms that are present in glia as well. APP-KPI mRNA levels correlated with soluble APPalpha-KPI protein (sAPPalpha-KPI) levels measured by ELISA (tau=0.33, p=0.015 by Kendall's rank correlation); in turn, soluble APPalpha-KPI protein levels positively correlated with Tris-extractable, soluble Abeta40 (p=0.046) and 42 levels (p=0.007). The ratio of soluble APPalpha-KPI protein levels to total APP protein increased in AD, and also correlated with GFAP protein levels in AD. These results suggest that altered transcription of APP in AD is proportionately associated with Abeta peptide, may occur in the context of gliosis, and may contribute to Abeta deposition in sporadic AD.

    Funded by: NIA NIH HHS: AG08487, P50 AG05134

    Brain research 2007;1161;116-23

  • Methylene blue inhibits amyloid Abeta oligomerization by promoting fibrillization.

    Necula M, Breydo L, Milton S, Kayed R, van der Veer WE, Tone P and Glabe CG

    Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA.

    Amyloid plaques are hallmark neuropathological lesions in Alzheimer's disease, which consist of abnormally aggregated Abeta protein. Multiple Abeta aggregated species have been identified, and neurotoxicity appears to be correlated with the amount of nonfibrillar oligomers. Therefore, selective inhibition of Abeta oligomer formation has emerged as an attractive means of therapeutic intervention. To investigate whether small molecules can modulate aggregation to achieve selective inhibition of neurotoxic amyloid oligomers, Abeta aggregation was assayed in vitro in the presence of methylene blue, using immunoreactivity with the prefibrillar oligomer-specific antibody A11, transmission electron microscopy, and turbidity assays. Methylene blue inhibited oligomerization when used at substoichiometric concentrations relative to that of the Abeta monomer. Inhibition of Abeta oligomerization was achieved concomitant with promotion of fibrillization, suggesting that oligomer and fibril formation are distinct and competing pathways. Methylene blue-mediated promotion of fiber formation occurred via a dose-dependent decrease in the lag time and an increase in the fibrillization rate, consistent with promotion of both filament nucleation and elongation. Addition of methylene blue to preformed oligomers resulted in oligomer loss and promotion of fibrillization. The data show that Abeta oligomer formation is inhibited by promoting fibril formation, which suggests that the relative pathological significance of oligomers and fibrils may be tested in vivo using methylene blue. If Abeta oligomers represent the primary pathogenic species, then inhibition of this highly toxic species via promotion of formation of less toxic aggregates may be therapeutically useful.

    Funded by: NINDS NIH HHS: NS 31230

    Biochemistry 2007;46;30;8850-60

  • Rab5 mediates an amyloid precursor protein signaling pathway that leads to apoptosis.

    Laifenfeld D, Patzek LJ, McPhie DL, Chen Y, Levites Y, Cataldo AM and Neve RL

    Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts 02478, USA. dlaifenfeld@mclean.harvard.edu

    Alzheimer's disease (AD) involves activation of apoptotic pathways that may be regulated through signaling cascades initiated by the amyloid precursor protein (APP). Enlarged endosomes have been observed in postmortem AD brains at very early stages of the disease. We show here that exogenous expression of a familial AD (FAD) mutant of APP or of the APP binding protein APP-BP1 in neurons causes enlargement of early endosomes, increased receptor-mediated endocytosis via a pathway dependent on APP-BP1 binding to APP, and apoptosis. Levels of both APP-BP1 and Rab5 are elevated in early endosomes in cortical embryonic neurons expressing APP(V642I) or APP-BP1, in cultured skin fibroblast cells from Down syndrome subjects, and in postmortem hippocampal tissue of individuals with AD. Indeed, Rab5 was found to bind specifically to APP-BP1, between amino acids 443 and 479. Inhibition of Rab5 or dynamin activity, but not of Eps15 (epidermal growth factor receptor pathway substrate 15) activity, rescued neurons from apoptosis induced by either APP(V642I) or APP-BP1, without affecting levels of intracellular or secreted amyloid-beta (Abeta). Induction of Rab5 activity via expression of a constitutively active mutant led to an increase in neuronal apoptosis more than twice that attributable to induction of endosome enlargement via a Rab5-independent mechanism, regardless of Abeta production. Together, these findings suggest that Rab5 activation via an APP/APP-BP1-initiated signaling pathway mediates neuronal apoptosis caused by FAD mutants of APP and that, within this pathway, Rab5 has a specific role in signaling that is distinct from, although not independent of, its role in trafficking.

    Funded by: NIA NIH HHS: AG021185, AG12954

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;27;7141-53

  • A genetic association analysis of cognitive ability and cognitive ageing using 325 markers for 109 genes associated with oxidative stress or cognition.

    Harris SE, Fox H, Wright AF, Hayward C, Starr JM, Whalley LJ and Deary IJ

    Department of Psychology, University of Edinburgh, Edinburgh, UK. Sarah.Harris@hgu.mrc.ac.uk <Sarah.Harris@hgu.mrc.ac.uk&gt;

    Background: Non-pathological cognitive ageing is a distressing condition affecting an increasing number of people in our 'ageing society'. Oxidative stress is hypothesised to have a major role in cellular ageing, including brain ageing.

    Results: Associations between cognitive ageing and 325 single nucleotide polymorphisms (SNPs), located in 109 genes implicated in oxidative stress and/or cognition, were examined in a unique cohort of relatively healthy older people, on whom we have cognitive ability scores at ages 11 and 79 years (LBC1921). SNPs showing a significant positive association were then genotyped in a second cohort for whom we have cognitive ability scores at the ages of 11 and 64 years (ABC1936). An intronic SNP in the APP gene (rs2830102) was significantly associated with cognitive ageing in both LBC1921 and a combined LBC1921/ABC1936 analysis (p < 0.01), but not in ABC1936 alone.

    Conclusion: This study suggests a possible role for APP in normal cognitive ageing, in addition to its role in Alzheimer's disease.

    Funded by: Medical Research Council: MC_U127561128

    BMC genetics 2007;8;43

  • Studies on brain volume, Alzheimer-related proteins and cytokines in mice with chronic overexpression of IL-1 receptor antagonist.

    Oprica M, Hjorth E, Spulber S, Popescu BO, Ankarcrona M, Winblad B and Schultzberg M

    Department of Neurobiology, Care Sciences and Society, Division of Neurodegeneration & Neuroinflammation, Karolinska Institutet, Huddinge, SE-14186 Stockholm, Sweden. Mircea.Oprica@ki.se

    Inflammation is associated with both acute and chronic neurological disorders, including stroke and Alzheimer's disease (AD). Cytokines such as interleukin (IL)-1 have several activities in the brain both under physiological and pathophysiological conditions. The objective of this study was to evaluate consequences of the central blockade of IL-1 transmission in a previously developed transgenic mouse strain with brain-directed overexpression of human soluble IL-1 receptor antagonist (Tg hsIL-1ra). Effects on brain morphology and brain levels of the AD-related proteins beta-amyloid precursor protein (APP) and presenilin 1(PS1), as well as the levels of IL-1beta, IL-6 and tumour necrosis factor-alpha (TNF-alpha) were analysed in homozygotic and heterozygotic mice and wild type (WT) controls, of both genders and of young (30-40 days) and adult (13-14 months) age. A marked reduction in brain volume was observed in transgenic mice as determined by volumetry. Western blot analysis showed higher levels of APP, but lower levels of PS1, in adult animals than in young ones. In the cerebellum, heterozygotic (Tg hsIL-1ra(+/-)) mice had lower levels of APP and PS1 than WT mice. With one exception, there were no genotypic differences in the levels of IL-1beta, IL-6 and TNF-alpha. The cytokine levels were generally higher in adult than in young mice. In conclusion, the chronic blockade of IL-1 signalling in the brain was associated with an atrophic phenotype of the brain, and with modified levels of APP and PS1. Brain-directed overexpression of hsIL-1ra was not followed by major compensatory changes in the levels of pro-inflammatory cytokines.

    Journal of cellular and molecular medicine 2007;11;4;810-25

  • Tauopathies and synucleinopathies: do cerebrospinal fluid beta-amyloid peptides reflect disease-specific pathogenesis?

    Mollenhauer B, Bibl M, Esselmann H, Steinacker P, Trenkwalder C, Wiltfang J and Otto M

    Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA. bmollenhauer@rics.bwh.harvard.edu

    To evaluate variations in amyloid beta (Abeta) peptide pattern in cerebrospinal fluid (CSF) in neurodegenerative disorders. A recently established quantitative urea-based Abeta-sodium-dodecylsulfate-polyacrylamide-gel-electrophoresis with western immunoblot (Abeta-SDS-PAGE/immunoblot) revealed a highly conserved Abeta peptide (Abeta1-37, 1-38, 1-39, 1-40, 1-42) pattern in CSF. We asked whether the variation might be useful to further elucidate the overlap between or distinctions among neurodegenerative diseases in Abeta-processing. We used the Abeta-SDS-PAGE/immunoblot to investigate CSF for disease-specific Abeta peptide patterns. CSF samples from 96 patients with mainly clinically diagnosed Alzheimer's disease (n = 15), progressive supranuclear palsy (n = 20), corticobasal degeneration (n = 12), Parkinson's disease (n = 11), multiple systems atrophy (n = 18), and dementia with Lewy-bodies (n = 20) were analysed as well a comparison group (n = 19). The Abeta peptide patterns varied between tauopathies and synucleinopathies and between all diseases and the comparison group, possibly due to the influence of tau and alpha-synuclein on Abeta-processing.

    Journal of neural transmission (Vienna, Austria : 1996) 2007;114;7;919-27

  • Time resolved structure analysis of growing beta-amyloid fibers.

    Witte T, Haller LA, Luttmann E, Krüger J, Fels G and Huber K

    Fakultät für Naturwissenschaften, Department Chemie, Physikalische Chemie Universität Paderborn, Warburger Str. 100, D-33098 Paderborn, Germany.

    Formation of beta-amyloid plaques is a crucial feature of Alzheimer's disease. In the present work time resolved static light scattering was applied to investigate the size and shape of growing beta-amyloid aggregates preceding plaque formation. The beta-amyloid protein with 40 amino acid residues was used. Salt free buffer solutions and solutions with 0.15M NaCl at 37 degrees C served as the aggregation medium. The focus lay on the first 2h following initiation of the aggregation process which corresponds to the protofibril phase. Addition of the NaCl accelerated the aggregation process considerably. Scattering data from aggregation in saline solutions indicated formation of long fibers which suggest interpretation of data with the worm-like chain model. Two important results were revealed: (i) At the end of the time resolved recordings, the worm-like chain model provided a fully adequate picture for the growing aggregates. Chain stiffness is characterised in terms of the persistence length, which is close to 50 nm. The linear mass density of the growing fibers approached a value of two monomers per nm corresponding to single stranded fibers, which is in accordance with presently existing models for the aggregation of beta-amyloid. The fibers finally reached contour lengths of several thousand nanometers. (ii) The plateau values for the persistence length and linear mass density observed in the final regime are gradually approached from higher values. This observation is inconsistent with simple worm-like chains. Rather does it indicate existence of another species during the initial phase of the aggregation, in addition to monomers and fibers. Aside from further insight into fundamental aspects of beta-amyloid aggregation, time resolved static light scattering provides an appropriate tool for assay tests with drugs designed to interfere with the aggregation process.

    Journal of structural biology 2007;159;1;71-81

  • Validation of amyloid-beta peptides in CSF diagnosis of neurodegenerative dementias.

    Bibl M, Mollenhauer B, Lewczuk P, Esselmann H, Wolf S, Trenkwalder C, Otto M, Stiens G, Rüther E, Kornhuber J and Wiltfang J

    Department of Psychiatry, University of Goettingen, Goettingen, Germany. mbibl@gwdg.de

    Biomarkers for differential diagnosis of the three most frequent degenerative forms of dementia, Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and frontotemporal dementias (FTD), are currently under intensive investigation, but disease-specific biomarkers for FTD and DLB are still lacking. We analyzed 303 cerebrospinal fluid (CSF) samples of 71 AD, 32 DLB and 36 FTD patients in comparison to 93 various other dementias (OD), 20 peripheral neurologic disease (PND) controls, 25 neurodegenerative disorders without dementia (ND) and 26 depressive cognitive complainers (DCC) for distinct CSF amyloid-beta (Abeta) peptide patterns, using the quantitative Abeta-SDS-PAGE/immunoblot. Additionally, the novel electrochemiluminescence technique (MSD) was used to validate the measures on Abeta1-38. The main outcome measures were a striking decrease of Abeta1-42 in AD (P=7.4 x 10(-19)), and most interestingly a pronounced decrease of Abeta1-38 in FTD (P=9.6 x 10(-7)). Moreover, a novel peptide that most probably represents an oxidized alpha-helical form of Abeta1-40 (Abeta1-40(ox)) displayed a highly significant increase in DLB (P=3.7 x 10(-3)) as compared to non-demented disease controls. The overall diagnostic accuracy of percentage Abeta peptide abundances (Abeta1-X%) was clearly superior to absolute CSF Abeta levels. Abeta1-42% and Abeta1-38% enabled contrasts of 85% or beyond to distinguish AD and FTD, respectively, from all other investigated subjects. Abeta1-40(ox)% yielded a diagnostic sensitivity and specificity of 88 and 73% for the detection of DLB among all other investigated patients. We found a strong correlation between Abeta1-38 levels as measured by the Abeta-SDS-PAGE/immunoblot and MSD, respectively. CSF Abeta peptides may reflect disease-specific impact of distinct neurodegenerative processes on Abeta peptide metabolism and represent a potential diagnostic biomarker for AD, FTD and DLB.

    Molecular psychiatry 2007;12;7;671-80

  • Cellular prion protein regulates beta-secretase cleavage of the Alzheimer's amyloid precursor protein.

    Parkin ET, Watt NT, Hussain I, Eckman EA, Eckman CB, Manson JC, Baybutt HN, Turner AJ and Hooper NM

    Proteolysis Research Group, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, and Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT, United Kingdom.

    Proteolytic processing of the amyloid precursor protein (APP) by beta-secretase, beta-site APP cleaving enzyme (BACE1), is the initial step in the production of the amyloid beta (Abeta) peptide, which is involved in the pathogenesis of Alzheimer's disease. The normal cellular function of the prion protein (PrP(C)), the causative agent of the transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease in humans, remains enigmatic. Because both APP and PrP(C) are subject to proteolytic processing by the same zinc metalloproteases, we tested the involvement of PrP(C) in the proteolytic processing of APP. Cellular overexpression of PrP(C) inhibited the beta-secretase cleavage of APP and reduced Abeta formation. Conversely, depletion of PrP(C) in mouse N2a cells by siRNA led to an increase in Abeta peptides secreted into the medium. In the brains of PrP knockout mice and in the brains from two strains of scrapie-infected mice, Abeta levels were significantly increased. Two mutants of PrP, PG14 and A116V, that are associated with familial human prion diseases failed to inhibit the beta-secretase cleavage of APP. Using constructs of PrP, we show that this regulatory effect of PrP(C) on the beta-secretase cleavage of APP required the localization of PrP(C) to cholesterol-rich lipid rafts and was mediated by the N-terminal polybasic region of PrP(C) via interaction with glycosaminoglycans. In conclusion, this is a mechanism by which the cellular production of the neurotoxic Abeta is regulated by PrP(C) and may have implications for both Alzheimer's and prion diseases.

    Funded by: Medical Research Council: G9824728; NINDS NIH HHS: NS042192, NS048554-01, R01 NS042192, R01 NS048554

    Proceedings of the National Academy of Sciences of the United States of America 2007;104;26;11062-7

  • Alkalizing drugs induce accumulation of amyloid precursor protein by-products in luminal vesicles of multivesicular bodies.

    Vingtdeux V, Hamdane M, Loyens A, Gelé P, Drobeck H, Bégard S, Galas MC, Delacourte A, Beauvillain JC, Buée L and Sergeant N

    INSERM, U837, Neurodegenerative Disorders and Neuronal Death, Lille, France.

    Amyloid precursor protein (APP) metabolism is central to the pathogenesis of Alzheimer disease. We showed recently that the amyloid intracellular domain (AICD), which is released by gamma-secretase cleavage of APP C-terminal fragments (CTFs), is strongly increased in cells treated with alkalizing drugs (Vingtdeux, V., Hamdane, M., Bégard, S., Loyens, A., Delacourte, A., Beauvillain, J.-C., Buée, L., Marambaud, P., and Sergeant, N. (2007) Neurobiol. Dis. 25, 686-696). Herein, we aimed to determine the cell compartment in which AICD accumulates. We show that APP-CTFs and AICD are present in multivesicular structures. Multivesicular bodies contain intraluminal vesicles (known as exosomes) when released in the extracellular space. We demonstrate that APP, APP-CTFs, and AICD are integrated and secreted within exosomes in differentiated neuroblastoma and primary neuronal culture cells. Together with recent data showing that amyloid-beta is also found in exosomes, our data show that multivesicular bodies are essential organelles for APP metabolism and that all APP metabolites can be secreted in the extracellular space.

    The Journal of biological chemistry 2007;282;25;18197-205

  • Abeta40 protects non-toxic Abeta42 monomer from aggregation.

    Yan Y and Wang C

    Center for Biotechnology and Interdisciplinary Studies, Biology Department, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.

    Abeta40 and Abeta42 are the predominant Abeta species in the human body. Toxic Abeta42 oligomers and fibrils are believed to play a key role in causing Alzheimer's disease (AD). However, the role of Abeta40 in AD pathogenesis is not well established. Emerging evidence indicates a protective role for Abeta40 in AD pathogenesis. Although Abeta40 is known to inhibit Abeta42 fibril formation, it is not clear whether the inhibition acts on the non-toxic monomer or acts on the toxic Abeta42 oligomers. In contrast to conventional methods that detect the appearance of fibrils, in our study Abeta42 aggregation was monitored by the decreasing NMR signals from Abeta42 monomers. In addition, differential NMR isotope labelling enabled the selective observation of Abeta42 aggregation in a mixture of Abeta42 and Abeta40. We found Abeta40 monomers inhibit the aggregation of non-toxic Abeta42 monomers, in an Abeta42/Abeta40 ratio-dependent manner. NMR titration revealed that Abeta40 monomers bind to Abeta42 aggregates with higher affinity than Abeta42 monomers. Abeta40 can also release Abeta42 monomers from Abeta42 aggregates. Thus, Abeta40 likely protects Abeta42 monomers by competing for the binding sites on pre-existing Abeta42 aggregates. Combining our data with growing evidence from transgenic mice and human genetics, we propose that Abeta40 plays a critical, protective role in Alzheimer's by inhibiting the aggregation of Abeta42 monomer. Abeta40 itself, a peptide already present in the human body, may therefore be useful for AD prevention and therapy.

    Journal of molecular biology 2007;369;4;909-16

  • Association studies testing for risk for late-onset Alzheimer's disease with common variants in the beta-amyloid precursor protein (APP).

    Nowotny P, Simcock X, Bertelsen S, Hinrichs AL, Kauwe JS, Mayo K, Smemo S, Morris JC and Goate A

    Department of Psychiatry, Washington University School of Medicine, St. Louis, MO 63110, USA.

    Linkage studies have suggested a susceptibility locus for late-onset Alzheimer's disease (LOAD) on chromosome 21. A functional candidate gene in this region is the beta-amyloid precursor protein (APP) gene. Previously, coding mutations in APP have been associated with early onset Alzheimer's Disease (EOAD). Three copies of APP are associated with AD pathology in Down's syndrome and in EOAD, suggesting that overexpression of APP may be a risk factor for LOAD. Although APP is a strong functional and positional candidate, to date there has been no thorough investigation using a dense map of SNPs across the APP gene. In order to investigate the role of common variation in the APP gene in the risk of LOAD, we genotyped 44 SNPs, spanning 300 kb spanning the entire gene, in a large case-control series of 738 AD cases and 657 healthy controls. The SNPs showed no association in genotypic or allelic tests, even after stratification for presence or absence of the APOE 4 allele. Haplotype analysis also failed to reveal significant association with any common haplotypes. These results suggest that common variation in the APP gene is not a significant risk factor for LOAD. However, we cannot rule out the possibility that multiple rare variants that increase APP expression or Abeta production might influence the risk for LOAD.

    Funded by: NIA NIH HHS: P01 AG03991, P50 AG05681, R01 AG16208

    American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics 2007;144B;4;469-74

  • Kinetic analysis of aggregated amyloid-beta peptide clearance in adult bone-marrow-derived macrophages from APP and CCL2 transgenic mice.

    Yamamoto M, Kiyota T, Walsh SM and Ikezu T

    The Center for Neurovirology and Neurodegenerative Disorders, Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, 985880 Nebraska Medical Center, Omaha, NE 68198-5880, USA. tikezu@unmc.edu

    Accumulating evidence suggests that bone-marrow (BM)-derived mononuclear phagocytes have an important role in the clearance of soluble and aggregated amyloid-beta peptides (Abeta) in Alzheimer's disease (AD) brains. However, the exact kinetics of Abeta clearance in mononuclear phagocytes derived from transgenic animal models of AD expressing beta-amyloid precursor protein (APP) mutants have been poorly characterized. We have examined whether CCL2 and APP expression affects the clearance of Abeta in conjunction with our control, acetylated low-density lipoprotein (AcLDL), using primary cultured BM-derived macrophages derived from adult APP, CCL2, APP/CCL2, and control littermates. Pulse-chase analysis demonstrated three distinct destinations for Abeta40 and AcLDL: intracellular retention, degradation, and secretion. As predicted, 50% of Abeta remained intracellularly contained even 5 days after pulse, while 40% of degraded and 14% of nondegraded Abeta were secreted. APP/CCL2 macrophages show reduced intracellular Abeta retention, along with enhanced secretion of both degraded and nondegraded Abeta. Abeta accumulation in aggresome is also partially reduced in APP/CCL2 macrophages as compared to other APP, CCL2, or control groups, suggesting impaired sorting of aggregated Abeta in aggresomes. The degradation of intracranially injected (125)I-Abeta40 aggregates was also enhanced in adult APP/CCL2 mice as compared to APP littermates in vivo. These data suggest that APP and CCL2 synergistically enhance BM-derived macrophage-mediated clearance of Abeta. In contrast, the clearance of AcLDL by BM-derived macrophages was not significantly enhanced by the presence of either APP or CCL2.

    Funded by: NINDS NIH HHS: NS043985

    Journal of neuroimmune pharmacology : the official journal of the Society on NeuroImmune Pharmacology 2007;2;2;213-21

  • Notch1 intracellular domain suppresses APP intracellular domain-Tip60-Fe65 complex mediated signaling through physical interaction.

    Kim SY, Kim MY, Mo JS and Park HS

    Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Yongbong-dong, Buk-ku, Gwangju, 500-757, Republic of Korea.

    The amyloid beta-precursor protein (APP) and the Notch receptor are both type 1 integral transmembrane proteins, and both are cleaved by presenilin-dependent gamma-secretase activity. In this study, we have demonstrated that the Notch intracellular domain (Notch1-IC) suppresses APP-intracellular domain (AICD)-mediated ROS generation and cell death after being processed by gamma secretase. Notch1-IC physically interacts with AICD, Fe65, and Tip60, thereby disrupting the association of the AICD-Fe65-Tip60 trimeric transcription activator complex in AICD signaling. AICD-Fe65-Tip60 mediated reactive oxygen species generation was found to be suppressed by Notch1-IC. Furthermore, AICD-Fe65-Tip60 was shown to mediate cell death in human neuroblastoma cells, and the overexpression of Notch1-IC inhibited cell death induced by AICD-Fe65-Tip60. Collectively, our findings indicate that Notch1-IC plays the role of a negative regulator in AICD signaling via the disruption of the AICD-Fe65-Tip60 trimeric complex.

    Biochimica et biophysica acta 2007;1773;6;736-46

  • Apoptosis signal-regulating kinase 1 in amyloid beta peptide-induced cerebral endothelial cell apoptosis.

    Hsu MJ, Hsu CY, Chen BC, Chen MC, Ou G and Lin CH

    Graduate Institute of Medical Sciences, Taipei Medical University, Taipei 110, Taiwan.

    A pathological hallmark of Alzheimer's disease is accumulation of amyloid-beta peptide (Abeta) in senile plaques. Abeta has also been implicated in vascular degeneration in cerebral amyloid angiopathy because of its cytotoxic effects on non-neuronal cells, including cerebral endothelial cells (CECs). We explore the role of apoptosis signal-regulating kinase 1 (ASK1) in Abeta-induced death in primary cultures of murine CECs. Abeta induced ASK1 dephosphorylation, which could be prevented by selective inhibition of protein phosphatase 2A (PP2A) but not PP2B. ASK1 dephosphorylation resulted in its dissociation from 14-3-3. ASK1, released from 14-3-3 inhibition, activated p38 mitogen-activated protein kinase (p38MAPK), leading to p53 phosphorylation. p53, a proapoptotic transcription factor, in turn transactivated the expression of Bax, a proapoptotic protein. Transfection with various dominant-negative mutants (DNs), including ASK1 DN and p38MAPK DN, suppressed Abeta-induced p38MAPK activation, p53 phosphorylation, and Bax upregulation and partially prevented CEC death. Bax knockdown using a bax small interfering RNA strategy also reduced Bax expression and subsequent CEC death. These results suggest that Abeta activates the ASK1-p38MAPK-p53-Bax cascade to cause CEC death in a PP2A-dependent manner.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;21;5719-29

  • A mutation screening by DHPLC of PSEN1 and APP genes reveals no significant variation associated with the sporadic late-onset form of Alzheimer's disease.

    Scacchi R, Gambina G, Moretto G and Corbo RM

    CNR Institute of Molecular Biology and Pathology, c/o Department of Genetics and Molecular Biology, University La Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy. Renato.Scacchi@uniromal.it

    Alzheimer's disease (AD), the most common cause of dementia in the elderly, is usually divided into familial and sporadic forms, according to family history. The familial form has often been reportedly caused by mutations in amyloid precursor protein (APP), presenilin-1 (PSEN1), or presenilin-2 (PSEN2) genes, whereas the genetic component for the sporadic form is less clear. We carried out mutation screening in exons 16 and 17 of APP, and in exons 3, 4, 5, 6, 7, 10 of PSEN1 genes in patients with the sporadic late-onset form of AD (LOAD). The aim of this study was to ascertain whether any variation in these genes, besides that of the well-known apolipoprotein E common polymorphism, could be involved in the onset of the disease. To search for the single nucleotide substitutions, we examined 172 LOAD patients by the denaturing high-performance liquid chromatography (DHPLC) technique. Only one same-sense mutation in exon 4 of PSEN1 gene (N32) was observed in this patient group. We concluded that the variation in the screened exons of the APP and PSEN1 genes, reportedly associated with familial AD, is not present in LOAD.

    Neuroscience letters 2007;418;3;282-5

  • Swedish amyloid precursor protein mutation increases phosphorylation of eIF2alpha in vitro and in vivo.

    Kim HS, Choi Y, Shin KY, Joo Y, Lee YK, Jung SY, Suh YH and Kim JH

    Department of Pharmacology, College of Medicine, National Creative Research Initiative Center for Alzheimer's Dementia and Neuroscience Research Institute, MRC, Seoul National University, Seoul, South Korea.

    Swedish double mutation (KM670/671NL) of amyloid precursor protein (Swe-APP), a prevailing cause of familial Alzheimer's disease (FAD), is known to increase in Abeta production both in vitro and in vivo, but its underlying molecular basis leading to Alzheimer's disease (AD) pathogenesis remains to be elucidated, especially for the early phase of disease. We have confirmed initially that the expression of Swe-APP mutant transgene reduced cell viability via ROS production but this effect was eliminated by an anti-oxidative agent, vitamin E. We also found that eukaryotic translation initiation factor-2alpha (eIF2alpha), which facilitates binding of initiator tRNA to ribosomes to set on protein synthesis, was phosphorylated in cultured cells expressing Swe-APP. This increase in phosphorylated eIF2alpha was also attenuated significantly by treatment with vitamin E. The finding that eIF2alpha became highly phosphorylated by increased production of Abeta was substantiated in brain tissues of both an AD animal model and AD patients. Although an increase in Abeta production would result in cell death eventually (in late-phase of the disease), the altered phosphorylation state of eIF2alpha evoked by Abeta may account for the decreased efficacy of mRNA translation and de novo protein synthesis required for synaptic plasticity, and may consequently be one of molecular causes for impairment of cognitive functions exhibited in the early phase of AD patients.

    Journal of neuroscience research 2007;85;7;1528-37

  • The Arctic Alzheimer mutation favors intracellular amyloid-beta production by making amyloid precursor protein less available to alpha-secretase.

    Sahlin C, Lord A, Magnusson K, Englund H, Almeida CG, Greengard P, Nyberg F, Gouras GK, Lannfelt L and Nilsson LN

    Department of Public Health and Caring Sciences, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden. charlotte.sahlin@pubcare.uu.se

    Mutations within the amyloid-beta (Abeta) domain of the amyloid precursor protein (APP) typically generate hemorrhagic strokes and vascular amyloid angiopathy. In contrast, the Arctic mutation (APP E693G) results in Alzheimer's disease. Little is known about the pathologic mechanisms that result from the Arctic mutation, although increased formation of Abeta protofibrils in vitro and intraneuronal Abeta aggregates in vivo suggest that early steps in the amyloidogenic pathway are facilitated. Here we show that the Arctic mutation favors proamyloidogenic APP processing by increased beta-secretase cleavage, as demonstrated by altered levels of N- and C-terminal APP fragments. Although the Arctic mutation is located close to the alpha-secretase site, APP harboring the Arctic mutation is not an inferior substrate to a disintegrin and metalloprotease-10, a major alpha-secretase. Instead, the localization of Arctic APP is altered, with reduced levels at the cell surface making Arctic APP less available for alpha-secretase cleavage. As a result, the extent and subcellular location of Abeta formation is changed, as revealed by increased Abeta levels, especially at intracellular locations. Our findings suggest that the unique clinical symptomatology and neuropathology associated with the Arctic mutation, but not with other intra-Abeta mutations, could relate to altered APP processing with increased steady-state levels of Arctic Abeta, particularly at intracellular locations.

    Funded by: NIA NIH HHS: AG09464

    Journal of neurochemistry 2007;101;3;854-62

  • Plasma beta amyloid and impaired CO2-induced cerebral vasomotor reactivity.

    van Dijk EJ, Prins ND, Hofman A, van Duijn CM, Koudstaal PJ and Breteler MM

    Department of Epidemiology and Biostatistics, Erasmus MC, Erasmus University Medical Center, PO Box 1738, 3000 Rotterdam, The Netherlands.

    Amyloid beta (Abeta) may disturb cerebral autoregulation by damaging the wall of small cerebral blood vessels and by direct negative vasoactive properties. We assessed whether previous and concurrent plasma Abeta(1-40) and Abeta(1-42) levels were associated with an impaired CO2-induced cerebral vasomotor response. In the longitudinal population-based Rotterdam Study we measured plasma Abeta levels and cerebral vasomotor reactivity to hypercapnia with transcranial Doppler ultrasonography (TCD) in 441 people, aged 60-90 years. We performed age and sex adjusted logistic regression analysis. Plasma Abeta levels assessed on average 6.5-year before TCD were linearly associated with an impaired CO2-induced cerebral vasomotor response (odds ratio 1.48 (95%CI 1.19;1.84) per standard deviation increase in Abeta(1-40), and 1.36 (95%CI 1.09;1.70) per standard deviation increase in Abeta(1-42)). Such an association was not present for Abeta assessed concurrently with the TCD measurement. Persons whose plasma Abeta(1-40) levels had decreased in the 6.5-year period preceding TCD measurements were more likely to have an impaired CO2-induced vasomotor reactivity. Overall our observations are most compatible with plasma Abeta levels representing vascular Abeta deposits years later resulting in impaired CO2-induced vasomotor reactivity.

    Neurobiology of aging 2007;28;5;707-12

  • Proteins that bind to the RERMS region of beta amyloid precursor protein.

    Pawlik M, Otero DA, Park M, Fischer WH, Levy E and Saitoh T

    Nathan Kline Institute, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA. MPawlik@nki.rfmh.org

    The main objective of this study was to investigate the biological function of beta amyloid precursor protein (APP), in particular its nerve growth factor-like activity. We hypothesize that the extracellular domain containing the sequence RERMS, amino acids 328-332 of APP(695), represents the active site for this function. Binding assays using peptide fragments of this domain have demonstrated specific and saturable binding to the cell surface with affinity in the low nanomolar range. This induced our quest for an APP-specific receptor. We chose different peptide fragments of the RERMS domain as ligands and displacing agents on affinity columns to purify APP-binding molecules. Amino acid microsequencing yielded partial sequences of serum albumin, actin, two novel proteins of 41 and 63kDa, and human Collapsin Response Mediator Protein-2 (hCRMP-2). Because both APP and hCRMP-2 promote neuronal outgrowth and use a common signaling pathway, APP could be acting through a semaphorin receptor as well.

    Funded by: NINDS NIH HHS: NS42029, R01 NS042029-06

    Biochemical and biophysical research communications 2007;355;4;907-12

  • Regulated intramembrane proteolysis of the interleukin-1 receptor II by alpha-, beta-, and gamma-secretase.

    Kuhn PH, Marjaux E, Imhof A, De Strooper B, Haass C and Lichtenthaler SF

    Adolf-Butenandt-Institut, Ludwig-Maximilians-University, Schillerstrasse 44, 80336 Munich, Germany.

    Ectodomain shedding and intramembrane proteolysis of the amyloid precursor protein (APP) by alpha-, beta- and gamma-secretase are involved in the pathogenesis of Alzheimer disease (AD). Increased proteolytic processing and secretion of another membrane protein, the interleukin-1 receptor II (IL-1R2), have also been linked to the pathogenesis of AD. IL-1R2 is a decoy receptor that may limit detrimental effects of IL-1 in the brain. At present, the proteolytic processing of IL-1R2 remains little understood. Here we show that IL-1R2 can be proteolytically processed in a manner similar to APP. IL-1R2 expressed in human embryonic kidney 293 cells first undergoes ectodomain shedding in an alpha-secretase-like manner, resulting in secretion of the IL-1R2 ectodomain and the generation of an IL-1R2 C-terminal fragment. This fragment undergoes further intramembrane proteolysis by gamma-secretase, leading to the generation of the soluble intracellular domain of IL-1R2. Intramembrane cleavage of IL-1R2 was abolished by a highly specific inhibitor of gamma-secretase and was absent in mouse embryonic fibroblasts deficient in gamma-secretase activity. Surprisingly, the beta-secretase BACE1 and its homolog BACE2 increased IL-1R2 secretion resulting in C-terminal fragments nearly identical to the ones generated by the alpha-secretase-like cleavage. This suggests that both proteases may act as alternative alpha-secretase-like proteases. Importantly, BACE1 and BACE2 did not cleave several other membrane proteins, demonstrating that both proteases do not contribute to general membrane protein turnover but only cleave specific proteins. This study reveals a similar proteolytic processing of IL-1R2 and APP and may provide an explanation for the increased IL-1R2 secretion observed in AD.

    The Journal of biological chemistry 2007;282;16;11982-95

  • Dysfunction of amyloid precursor protein signaling in neurons leads to DNA synthesis and apoptosis.

    Neve RL and McPhie DL

    Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, MA 02478, USA. neve@helix.mgh.harvard.edu

    The classic neuropathological diagnostic markers for AD are amyloid plaques and neurofibrillary tangles, but their role in the etiology and progression of the disease remains incompletely defined. Research over the last decade has revealed that cell cycle abnormalities also represent a major neuropathological feature of AD. These abnormalities appear very early in the disease process, prior to the appearance of plaques and tangles; and it has been suggested that neuronal cell cycle regulatory failure may be a significant component of the pathogenesis of AD. The amyloid precursor protein (APP) is most commonly known as the source of the beta-amyloid (Abeta) peptides that accumulate in the brains of patients with AD. However, a large body of work supports the idea that APP is also a signaling receptor. Most recently, it has been shown that familial AD (FAD) mutations in APP or simple overexpression of wild type APP cause dysfunction of APP signaling, resulting in initiation of DNA synthesis in neurons and consequent apoptosis. In this article, we review the evidence that APP has the potential to activate aberrant neuronal cell cycle re-entry in AD, and we describe a signal transduction pathway that may mediate this abnormal activation of the cell cycle.

    Funded by: NIA NIH HHS: AG021185, AG12954, R01 AG012954-11, R01 AG012954-12, R01 AG021185-03, R01 AG021185-04

    Biochimica et biophysica acta 2007;1772;4;430-7

  • Focal adhesions regulate Abeta signaling and cell death in Alzheimer's disease.

    Caltagarone J, Jing Z and Bowser R

    Department of Pathology, University of Pittsburgh School of Medicine, BST S-420, 200 Lothrop St., Pittsburgh, PA 15261, USA.

    Alzheimer's disease (AD) is a neurodegenerative disorder that results from a loss of synaptic transmission and ultimately cell death. The presenting pathology of AD includes neuritic plaques composed of beta-amyloid peptide (Abeta) and neurofibrillary tangles composed of hyperphosphorylated tau, with neuronal loss in specific brain regions. However, the mechanisms that induce neuronal cell loss remain elusive. Focal adhesion (FA) proteins assemble into intracellular complexes involved in integrin-mediated communication between the extracellular matrix and the actin cytoskeleton, regulating many cell physiological processes including the cell cycle. Interestingly, recent studies report that integrins bind to Abeta fibrils, mediating Abeta signal transmission from extracellular sites of Abeta deposits into the cell and ultimately to the nucleus. In this review, we will discuss the Abeta induced integrin/FA signaling pathways that mediate cell cycle activation and cell death.

    Funded by: NINDS NIH HHS: NS042724, R01 NS042724-01A2, R01 NS042724-04

    Biochimica et biophysica acta 2007;1772;4;438-45

  • Membrane-mediated amyloidogenesis and the promotion of oxidative lipid damage by amyloid beta proteins.

    Murray IV, Liu L, Komatsu H, Uryu K, Xiao G, Lawson JA and Axelsen PH

    Department of Pharmacology, Center for Neurodegenerative Disease Research, Penn Genomics Institute, University of Pennsylvania, Philadelphia, PA 19104, USA.

    Evidence of oxidative stress and the accumulation of fibrillar amyloid beta proteins (Abeta) in senile plaques throughout the cerebral cortex are consistent features in the pathology of Alzheimer disease. To define a mechanistic link between these two processes, various aspects of the relationship between oxidative lipid membrane damage and amyloidogenesis were characterized by chemical and physical techniques. Earlier studies of this relationship demonstrated that oxidatively damaged synthetic lipid membranes promoted amyloidogenesis. The studies reported herein specify that 4-hydroxy-2-nonenal (HNE) is produced in both synthetic lipids and human brain lipid extracts by oxidative lipid damage and that it can account for accelerated amyloidogenesis. Abeta promotes the copper-mediated generation of HNE from polyunsaturated lipids, and in turn, HNE covalently modifies the histidine side chains of Abeta. HNE-modified Abeta have an increased affinity for lipid membranes and an increased tendency to aggregate into amyloid fibrils. Thus, the prooxidant activity of Abeta leads to its own covalent modification and to accelerated amyloidogenesis. These results illustrate how lipid membranes may be involved in templating the pathological misfolding of Abeta, and they suggest a possible chemical mechanism linking oxidative stress with amyloid formation.

    Funded by: NIA NIH HHS: P30 AG010124, R03 AG027893-01, R03 AG027893-02, R03 AG027893-03

    The Journal of biological chemistry 2007;282;13;9335-45

  • Flow-induced alignment of amyloid protofilaments revealed by linear dichroism.

    Adachi R, Yamaguchi K, Yagi H, Sakurai K, Naiki H and Goto Y

    Institute for Protein Research, Osaka University and CREST, Japan Science and Technology Agency, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.

    Amyloid fibrils underlying various serious amyloidoses including Alzheimer and prion diseases form characteristic deposits in which linear fibrils with an unbranched and rigid morphology associate laterally or radially, e.g. radial senile amyloid plaques of amyloid beta. To clarify the formation of these high order amyloid deposits, studying the rheology is important. A 22-residue K3 peptide fragment of beta2-microglobulin, a protein responsible for dialysis-related amyloidosis, forms long and homogeneous protofilament-like fibrils in 20% (v/v) 2,2,2-trifluoroethanol and 10 mM HCl (pH approximately 2). Here, using circular dichroism and linear dichroism, we observed the flow-induced alignment of fibrils. Analysis of far- and near-UV linear dichroism spectra suggested that both the net pi-pi* transition moment of the backbone carbonyl group and L(b) transition moment of the Tyr(26) side chain are oriented in parallel to the fibril axis, revealing the structural details of amyloid protofilaments. Moreover, the intensities of flow-induced circular dichroism or linear dichroism signals depended critically on the length and type of fibrils, suggesting that they are useful for detecting and characterizing amyloid fibrils.

    The Journal of biological chemistry 2007;282;12;8978-83

  • The novel cargo Alcadein induces vesicle association of kinesin-1 motor components and activates axonal transport.

    Araki Y, Kawano T, Taru H, Saito Y, Wada S, Miyamoto K, Kobayashi H, Ishikawa HO, Ohsugi Y, Yamamoto T, Matsuno K, Kinjo M and Suzuki T

    Laboratory of Neuroscience, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.

    Alcadeinalpha (Alcalpha) is an evolutionarily conserved type I membrane protein expressed in neurons. We show here that Alcalpha strongly associates with kinesin light chain (K(D) approximately 4-8x10(-9) M) through a novel tryptophan- and aspartic acid-containing sequence. Alcalpha can induce kinesin-1 association with vesicles and functions as a novel cargo in axonal anterograde transport. JNK-interacting protein 1 (JIP1), an adaptor protein for kinesin-1, perturbs the transport of Alcalpha, and the kinesin-1 motor complex dissociates from Alcalpha-containing vesicles in a JIP1 concentration-dependent manner. Alcalpha-containing vesicles were transported with a velocity different from that of amyloid beta-protein precursor (APP)-containing vesicles, which are transported by the same kinesin-1 motor. Alcalpha- and APP-containing vesicles comprised mostly separate populations in axons in vivo. Interactions of Alcalpha with kinesin-1 blocked transport of APP-containing vesicles and increased beta-amyloid generation. Inappropriate interactions of Alc- and APP-containing vesicles with kinesin-1 may promote aberrant APP metabolism in Alzheimer's disease.

    The EMBO journal 2007;26;6;1475-86

  • GxxxG motifs within the amyloid precursor protein transmembrane sequence are critical for the etiology of Abeta42.

    Munter LM, Voigt P, Harmeier A, Kaden D, Gottschalk KE, Weise C, Pipkorn R, Schaefer M, Langosch D and Multhaup G

    Institut für Chemie und Biochemie, Freie Universität Berlin, Berlin, Germany.

    Processing of the amyloid precursor protein (APP) by beta- and gamma-secretases leads to the generation of amyloid-beta (Abeta) peptides with varying lengths. Particularly Abeta42 contributes to cytotoxicity and amyloid accumulation in Alzheimer's disease (AD). However, the precise molecular mechanism of Abeta42 generation has remained unclear. Here, we show that an amino-acid motif GxxxG within the APP transmembrane sequence (TMS) has regulatory impact on the Abeta species produced. In a neuronal cell system, mutations of glycine residues G29 and G33 of the GxxxG motif gradually attenuate the TMS dimerization strength, specifically reduce the formation of Abeta42, leave the level of Abeta40 unaffected, but increase Abeta38 and shorter Abeta species. We show that glycine residues G29 and G33 are part of a dimerization site within the TMS, but do not impair oligomerization of the APP ectodomain. We conclude that gamma-secretase cleavages of APP are intimately linked to the dimerization strength of the substrate TMS. The results demonstrate that dimerization of APP TMS is a risk factor for AD due to facilitating Abeta42 production.

    The EMBO journal 2007;26;6;1702-12

  • The correlation between neurotoxicity, aggregative ability and secondary structure studied by sequence truncated Abeta peptides.

    Liao MQ, Tzeng YJ, Chang LY, Huang HB, Lin TH, Chyan CL and Chen YC

    Institute of Molecular and Cellular Biology, Tzu Chi University, Hualien 970, Taiwan.

    Aggregated beta-amyloid (Abeta) peptides are neurotoxic and cause neuronal death both in vitro and in vivo. Although the formation of a beta-sheet structure is usual required to form aggregates, the relationship between neurotoxicity and the Abeta sequence remains unclear. To explore the correlation between Abeta sequence, secondary structure, aggregative ability, and neurotoxicity, we utilized both full-length and fragment-truncated Abeta peptides. Using a combination of spectroscopic and cellular techniques, we demonstrated that neurotoxicity and aggregative ability are correlated while the relationship between these characteristics and secondary structure is not significant. The hydrophobic C-terminus, particularly the amino acids of 17-21, 25-35, and 41-42, is the main region responsible for neurotoxicity and aggregation. Deleting residues 17-21, 25-35 or 41-42 significantly reduced the toxicity. On the other hand, truncation of the peptides at either residues 22-24 or residues 36-40 had little effect on toxicity and aggregative ability. While the N-terminal residues 1-16 may not play a major role in neurotoxicity and aggregation, a lack of N-terminal fragment Abeta peptide, (e.g. Abeta17-35), does not display the neurotoxicity of either full-length or 17-21, 25-35 truncated Abeta peptides.

    FEBS letters 2007;581;6;1161-5

  • Endoplasmic reticulum chaperones inhibit the production of amyloid-beta peptides.

    Hoshino T, Nakaya T, Araki W, Suzuki K, Suzuki T and Mizushima T

    Graduate School of Medical and Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan.

    Abeta (amyloid-beta peptides) generated by proteolysis of APP (beta-amyloid precursor protein), play an important role in the pathogenesis of AD (Alzheimer's disease). ER (endoplasmic reticulum) chaperones, such as GRP78 (glucose-regulated protein 78), make a major contribution to protein quality control in the ER. In the present study, we examined the effect of overexpression of various ER chaperones on the production of Abeta in cultured cells, which produce a mutant type of APP (APPsw). Overexpression of GRP78 or inhibition of its basal expression, decreased and increased respectively the level of Abeta40 and Abeta42 in conditioned medium. Co-expression of GRP78's co-chaperones ERdj3 or ERdj4 stimulated this inhibitory effect of GRP78. In the case of the other ER chaperones, overexpression of some (150 kDa oxygen-regulated protein and calnexin) but not others (GRP94 and calreticulin) suppressed the production of Abeta. These results indicate that certain ER chaperones are effective suppressors of Abeta production and that non-toxic inducers of ER chaperones may be therapeutically beneficial for AD treatment. GRP78 was co-immunoprecipitated with APP and overexpression of GRP78 inhibited the maturation of APP, suggesting that GRP78 binds directly to APP and inhibits its maturation, resulting in suppression of the proteolysis of APP. On the other hand, overproduction of APPsw or addition of synthetic Abeta42 caused up-regulation of the mRNA of various ER chaperones in cells. Furthermore, in the cortex and hippocampus of transgenic mice expressing APPsw, the mRNA of some ER chaperones was up-regulated in comparison with wild-type mice. We consider that this up-regulation is a cellular protective response against Abeta.

    The Biochemical journal 2007;402;3;581-9

  • Natural oligomers of the Alzheimer amyloid-beta protein induce reversible synapse loss by modulating an NMDA-type glutamate receptor-dependent signaling pathway.

    Shankar GM, Bloodgood BL, Townsend M, Walsh DM, Selkoe DJ and Sabatini BL

    Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.

    Alzheimer's disease (AD) is characterized by decreased synapse density in hippocampus and neocortex, and synapse loss is the strongest anatomical correlate of the degree of clinical impairment. Although considerable evidence supports a causal role for the amyloid-beta protein (Abeta) in AD, a direct link between a specific form of Abeta and synapse loss has not been established. We demonstrate that physiological concentrations of naturally secreted Abeta dimers and trimers, but not monomers, induce progressive loss of hippocampal synapses. Pyramidal neurons in rat organotypic slices had markedly decreased density of dendritic spines and numbers of electrophysiologically active synapses after exposure to picomolar levels of soluble oligomers. Spine loss was reversible and was prevented by Abeta-specific antibodies or a small-molecule modulator of Abeta aggregation. Mechanistically, Abeta-mediated spine loss required activity of NMDA-type glutamate receptors (NMDARs) and occurred through a pathway involving cofilin and calcineurin. Furthermore, NMDAR-mediated calcium influx into active spines was reduced by Abeta oligomers. Partial blockade of NMDARs by pharmacological antagonists was sufficient to trigger spine loss. We conclude that soluble, low-n oligomers of human Abeta trigger synapse loss that can be reversed by therapeutic agents. Our approach provides a quantitative cellular model for elucidating the molecular basis of Abeta-induced neuronal dysfunction.

    Funded by: NIA NIH HHS: 1R01AG027443; NINDS NIH HHS: R01 NS046579-05

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;11;2866-75

  • Reelin depletion in the entorhinal cortex of human amyloid precursor protein transgenic mice and humans with Alzheimer's disease.

    Chin J, Massaro CM, Palop JJ, Thwin MT, Yu GQ, Bien-Ly N, Bender A and Mucke L

    Gladstone Institute of Neurological Disease, University of California, San Francisco, San Francisco, California 94158, USA.

    Reelin regulates nervous system development and modulates synaptic plasticity in the adult brain. Several findings suggest that alterations in Reelin signaling may contribute to neuronal dysfunction associated with Alzheimer's disease (AD). Cell surface receptors for Reelin, including integrins and very-low-density lipoprotein receptor/apolipoprotein E2 receptor, may be targets of amyloid-beta (Abeta) peptides presumed to play key roles in the pathogenesis of AD. Reelin also regulates the extent of tau phosphorylation. Finally, increased amounts of Reelin fragments have been found in CSF from AD patients, suggesting altered processing of Reelin. We therefore hypothesized that Reelin levels might be altered in the brains of human amyloid precursor protein (hAPP) transgenic mice, particularly in brain regions vulnerable to AD such as hippocampus and entorhinal cortex. Compared with nontransgenic controls, hAPP mice had significantly fewer Reelin-expressing pyramidal cells in the entorhinal cortex, the major population of glutamatergic neurons expressing Reelin in the brain. Western blot analysis of the hippocampus, which receives projections from the entorhinal cortex, revealed significant reductions in Reelin levels. In contrast, the number of Reelin-expressing GABAergic interneurons was not altered in either the entorhinal cortex or the hippocampus. Thus, neuronal expression of hAPP/Abeta is sufficient to reduce Reelin expression in a specific population of entorhinal cortical pyramidal neurons in vivo. Underscoring the relevance of these findings, we found qualitatively similar reductions of Reelin-expressing pyramidal neurons in the entorhinal cortex of AD brains. We conclude that alterations in Reelin processing or signaling may be involved in AD-related neuronal dysfunction.

    Funded by: NCRR NIH HHS: RR018928; NIA NIH HHS: AG022074, AG023501, P01AG007232, P50AG008702; NINDS NIH HHS: NS041787

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;11;2727-33

  • Non-cognitive behaviours in an APP/PS1 transgenic model of Alzheimer's disease.

    Pugh PL, Richardson JC, Bate ST, Upton N and Sunter D

    Neurology & GI CEDD, GlaxoSmithKline Research and Development Limited, New Frontiers Science Park, Third Avenue, Harlow, Essex CM19 5AW, UK. Pippa_L_Pugh@gsk.com

    Alzheimer's disease (AD) is characterised by progressive cognitive impairment with neuropsychiatric symptoms such as anomalous motor behaviour, depression, anxiety, weight loss, irritability and agitation. The effect of hAPP and PS1 overexpression on cognition has been well characterised in a variety of transgenic mouse models, however, non-cognitive behaviours have not been considered as systematically. The non-cognitive behaviour of the hAPP/PS1 transgenic mouse model (TASTPM) was observed at ages spanning the rapid progression of amyloid neuropathology. TASTPM transgenic mice, of both genders, exhibited decreased spontaneous motor activity, disinhibition, increased frequency and duration of feeding bouts, reduced body weight and, by 10 months, increased activity over a 24h period. In addition to the aforementioned behaviours, male transgenic mice also displayed enhanced aggression relative to wildtype controls. These data reveal previously unreported disease relevant behavioural changes that demonstrate the value of measuring behaviour in APP/PS1 transgenic models. These behavioural readouts could be useful in screening putative drug treatments for AD.

    Behavioural brain research 2007;178;1;18-28

  • Intracellular pH regulates amyloid precursor protein intracellular domain accumulation.

    Vingtdeux V, Hamdane M, Bégard S, Loyens A, Delacourte A, Beauvillain JC, Buée L, Marambaud P and Sergeant N

    INSERM U815, Centre Jean-Pierre Aubert, Neurodegenerative Disorders and Neuronal Death, 1, Place de Verdun, F-59045 Lille, France.

    The amyloid precursor protein (APP) metabolism is central to pathogenesis of Alzheimer's disease (AD). Parenchymal amyloid deposits, a neuropathological hallmark of AD, are composed of amyloid-beta peptides (Abeta). Abeta derives from the amyloid precursor protein (APP) by sequential cleavages by beta- and gamma-secretases. Gamma-secretase cleavage releases the APP intracellular domain (AICD), suggested to mediate a nuclear signaling. Physiologically, AICD is seldom detected and thus supposed to be rapidly degraded. The mechanisms responsible of its degradation remain unknown. We used a pharmacological approach and showed that several alkalizing drugs induce the accumulation of AICD in neuroblastoma SY5Y cell lines stably expressing APP constructs. Moreover, alkalizing drugs induce AICD accumulation in naive SY5Y, HEK and COS cells. This accumulation is not mediated by the proteasome or metallopeptidases and is not the result of an increased gamma-secretase activity since the gamma-secretase cleavage of Notch1 and N-Cadherin is not affected by alkalizing drug treatments. Altogether, our data demonstrate for the first time that alkalizing drugs induce the accumulation of AICD, a mechanism likely mediated by the endosome/lysosome pathway.

    Neurobiology of disease 2007;25;3;686-96

  • Polarized transport of Alzheimer amyloid precursor protein is mediated by adaptor protein complex AP1-1B.

    Icking A, Amaddii M, Ruonala M, Höning S and Tikkanen R

    Institute of Biochemistry II and Cluster of Excellence 'Macromolecular Complexes', University Clinic of Frankfurt, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany.

    Alzheimer amyloid precursor protein (APP) is the precursor for the Abeta peptide involved in pathogenesis of Alzheimer's disease. The soluble ectodomain fragment of APP (sAPP) functions as a growth factor for epithelial cells, suggesting an important function for APP outside neuronal tissue. Previous studies have shown that in polarized epithelial cells, APP is targeted to the basolateral domain. Tyr653 within the cytoplasmic tail of APP mediates the basolateral targeting of APP, but the sorting machinery that binds to this residue has largely remained unknown. In this study, we analyzed the role of adaptor complexes in the polarized sorting of APP. We show that the medium subunit mu1B of the epithelia-specific adaptor protein (AP)-1B binds onto the cytoplasmic tail of APP in a Tyr653-dependent way. Moreover, ectopic expression of mu1B in cells lacking AP-1B resulted in correction of apical missorting of wild-type but not Tyr653Ala APP. Basolateral secretion of sAPP was found to be independent of Tyr653. We propose a model for polarized targeting of APP according to which sorting of APP to basolateral domain is dependent on binding of AP-1B on Tyr653 in basolateral endosomes. This model is in accordance with the current understanding of sorting mechanisms mediating polarized targeting of membrane proteins.

    Traffic (Copenhagen, Denmark) 2007;8;3;285-96

  • Variations in the APP gene promoter region and risk of Alzheimer disease.

    Guyant-Maréchal L, Rovelet-Lecrux A, Goumidi L, Cousin E, Hannequin D, Raux G, Penet C, Ricard S, Macé S, Amouyel P, Deleuze JF, Frebourg T, Brice A, Lambert JC and Campion D

    INSERM U614, Faculty of Medicine, IFRMP, 76000 Rouen, France.

    We genotyped five polymorphisms, including two polymorphisms with known effects on transcriptional activity, in a large cohort of 427 Alzheimer disease (AD) cases and 472 control subjects. An association between rs463946 (-3102 G/C) and AD was found and was confirmed in a replication sample of a similar size. By contrast, analysis of three recently described rare mutations influencing APP transcription did not confirm their association with AD risk.

    Neurology 2007;68;9;684-7

  • Molecular dynamics studies of hexamers of amyloid-beta peptide (16-35) and its mutants: influence of charge states on amyloid formation.

    Han W and Wu YD

    Department of Chemistry, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China.

    To study the early stage of amyloid-beta peptide (Abeta) aggregation, hexamers of the wild-type (WT) Abeta(16-35) and its mutants with amyloid-like conformations have been studied by molecular dynamics simulations in explicit water for a total time of 1.7 micros. We found that the amyloid-like structures in the WT oligomers are destabilized by the solvation of ionic D23/K28 residues, which are buried in the fibrils. This means that the desolvation of D23/K28 residues may contribute to the kinetic barrier of aggregation in the early stage. In the E22Q/D23N, D23N/K28Q, and E22Q/D23N/K28Q mutants, hydration becomes much less significant because the mutated residues have neutral amide side-chains. These amide side-chains can form linear cross-strand hydrogen bond chains, or "polar zippers", if dehydrated. These "polar zippers" increase the stability of the amyloid-like conformation, reducing the barrier for the early-stage oligomerization. This is in accord with experimental observations that both the D23/K28 lactamization and the E22Q/D23N mutation promote aggregation. We also found that the E22Q/D23N mutant prefers an amyloid-like conformation that differs from the one found for WT Abeta. This suggests that different amyloid structures may be formed under different conditions.

    Proteins 2007;66;3;575-87

  • Absolute correlation between lag time and growth rate in the spontaneous formation of several amyloid-like aggregates and fibrils.

    Fändrich M

    Leibniz-Institut für Altersforschung, Fritz-Lipmann Institut, Beutenbergstrasse 11, D-07745 Jena, Germany. fandrich@fli-leibniz.de

    The formation of polypeptide aggregates, including amyloid fibrils and prions, is a biochemical process of considerable interest in the context of its association with ageing and neurodegeneration. Aggregation occurs typically with a lag phase and a growth phase that reflect an underlying nucleation-polymerisation mechanism. While the propensity of nucleation can be estimated from the lag time t(l), the efficiency of growth is represented by the growth rate k(g). Here, I have analysed the absolute k(g) and t(l) values from a total of 298 samples prepared from insulin, glucagon and different sequence variants of the Alzheimer's Abeta(1-40) peptide. Although these samples differ in the conditions of aggregation, systematic comparison reveals an overall similarity in the plot of k(g)versus t(l). The plot fits readily with the simple equation k(g)=alpha/t(l) and by using a proportionality factor alpha of 4.5. In contrast to the individual values of k(g) and t(l) that depend substantially on sequential and environmental parameters, alpha seems much less affected by such factors. These data suggest mechanistic similarities in the nucleation behaviour of different amyloid-like fibrils and aggregates.

    Journal of molecular biology 2007;365;5;1266-70

  • The amyloid precursor protein potentiates CHOP induction and cell death in response to ER Ca2+ depletion.

    Copanaki E, Schürmann T, Eckert A, Leuner K, Müller WE, Prehn JH and Kögel D

    Department of Neurosurgery, Johann Wolfgang Goethe University Clinics, D-60590 Frankfurt, Germany.

    Here we investigated the role of the amyloid precursor protein (APP) in regulation of Ca(2+) store depletion-induced neural cell death. Ca(2+) store depletion from the endoplasmic reticulum (ER) was induced by the SERCA (Sarco/Endoplasmic Reticulum Calcium ATPase) inhibitor thapsigargin which led to a rapid induction of the unfolded protein response (UPR) and a delayed activation of executioner caspases in the cultures. Overexpression of APP potently enhanced cytosolic Ca(2+) levels and cell death after ER Ca(2+) store depletion in comparison to vector-transfected controls. GeneChip and RT-PCR analysis revealed that the expression of classical UPR chaperone genes was not altered by overexpression of APP. Interestingly, the induction of the ER stress-responsive pro-apoptotic transcription factor CHOP was significantly upregulated in APP-overexpressing cells in comparison to vector-transfected controls. Chelation of intracellular Ca(2+) with BAPTA-AM revealed that enhanced CHOP expression after store depletion occurred in a Ca(2+)-dependent manner in APP-overexpressing cells. Prevention of CHOP induction by BAPTA-AM and by RNA interference was also able to abrogate the potentiating effect of APP on thapsigargin-induced apoptosis. Application of the store-operated channel (SOC)-inhibitors SK & F96365 and 2-APB downmodulated APP-triggered potentiation of cytosolic Ca(2+) levels and apoptosis after treatment with thapsigargin. Our data demonstrate that APP significantly modulates Ca(2+) store depletion-induced cell death in a SOC- and CHOP-dependent manner, but independent of the UPR.

    Biochimica et biophysica acta 2007;1773;2;157-65

  • Impaired spatial learning in the APPSwe + PSEN1DeltaE9 bigenic mouse model of Alzheimer's disease.

    Reiserer RS, Harrison FE, Syverud DC and McDonald MP

    Department of Pharmacology, Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37232-0325, USA.

    Mice co-expressing the Swedish amyloid precursor protein mutation (APP(Swe)) and exon 9 deletion (DeltaE9) of the PSEN1 gene begin to develop amyloid plaques at 6-7 months of age. We demonstrate here a spatial learning deficit in 7-month-old APP(Swe) + PSEN1DeltaE9 bigenic mice using an adaptation of the Barnes maze. Mice were first trained on a cued target followed by a hidden-target condition. Although bigenic mice quickly learned the cued-target version of the task, they were significantly impaired when switched to the hidden-target version. In contrast, a separate group of double-transgenic mice trained first on the spatial hidden-target version of the task were unimpaired relative to wild-type controls. We propose that processes such as general rule learning, context learning and exploratory habituation exert a greater influence when the testing environment is novel and overshadow the spatial memory deficit in naive bigenic mice. However, when cued-target training is conducted first, these processes habituate and the spatial learning deficit is unmasked. Seven-month-old APP(Swe) + PSEN1DeltaE9 mice were unimpaired on tests of memory that did not involve learning the rules governing spatial associations.

    Funded by: NIA NIH HHS: AG022439; NICHD NIH HHS: HD015052

    Genes, brain, and behavior 2007;6;1;54-65

  • When loss is gain: reduced presenilin proteolytic function leads to increased Abeta42/Abeta40. Talking Point on the role of presenilin mutations in Alzheimer disease.

    Wolfe MS

    Center for Neurologic Diseases, Harvard Medical School, Brigham and Women's Hospital, 77 Avenue Louis Pasteur, Harvard Institute of Medicine 754, Boston, Massachusetts 02115, USA. mwolfe@rics.bwh.harvard.edu

    More than 100 missense mutations in presenilin 1 and 2 are associated with early-onset dominant Alzheimer disease. These proteins span the membrane several times and are ostensibly the catalytic component of the gamma-secretase complex, which is responsible for producing the amyloid beta-peptide (Abeta) that deposits in the Alzheimer brain. A common outcome of Alzheimer-associated presenilin mutations is an increase in the ratio of the more aggregation-prone 42-residue form of Abeta to the 40-residue variant, which is often referred to as a presenilin 'gain of function'. An apparent paradox is that most of these mutant presenilins have reduced proteolytic efficiency, which forms part of the counter argument that presenilin 'loss of function' can cause the neuronal dysfunction and death that lead to the disease. In this review, a unifying hypothesis is presented that puts forward a biochemical mechanism by which slower less-efficient forms of the protease can result in a greater proportion of 42-residue Abeta.

    EMBO reports 2007;8;2;136-40

  • Bim is elevated in Alzheimer's disease neurons and is required for beta-amyloid-induced neuronal apoptosis.

    Biswas SC, Shi Y, Vonsattel JP, Leung CL, Troy CM and Greene LA

    Department of Pathology, Center for Neurobiology and Behavior and Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA. scb34@columbia.edu

    The molecules that mediate neuron death in Alzheimer's disease (AD) are largely unknown. We report that beta-amyloid (Abeta), a death-promoting peptide implicated in the pathophysiology of AD, induces the proapoptotic protein Bcl-2 interacting mediator of cell death (Bim) in cultured hippocampal and cortical neurons. We further find that Bim is an essential mediator of Abeta-induced neurotoxicity. Our examination of postmortem AD human brains additionally reveals upregulation of Bim in vulnerable entorhinal cortical neurons, but not in cerebellum, a region usually unaffected by AD. Accumulating evidence links inappropriate induction/activation of cell cycle-related proteins to AD, but their roles in the disease have been unclear. We find that the cell cycle molecule cyclin-dependent kinase 4 (cdk4) and its downstream effector B-myb, are required for Abeta-dependent Bim induction and death in cultured neurons. Moreover, neurons that overexpress Bim in AD brains also show elevated levels of the cell cycle-related proteins cdk4 and phospho-Rb. Our observations indicate that Bim is a proapoptotic effector of Abeta and of dysregulated cell cycle proteins in AD and identify both Bim and cell cycle elements as potential therapeutic targets.

    Funded by: NIA NIH HHS: AG-08702

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;4;893-900

  • Abeta40 inhibits amyloid deposition in vivo.

    Kim J, Onstead L, Randle S, Price R, Smithson L, Zwizinski C, Dickson DW, Golde T and McGowan E

    Department of Neuroscience, Mayo Clinic College of Medicine, Jacksonville, Florida 32224, USA.

    Numerous studies have established a pivotal role for Abeta42 in Alzheimer's disease (AD) pathogenesis. In contrast, although Abeta40 is the predominant form of amyloid beta (Abeta) produced and accumulates to a variable degree in the human AD brain, its role in AD pathogenesis has not been established. It has generally been assumed that an increase in Abeta40 would accelerate amyloid plaque formation in vivo. We have crossed BRI-Abeta40 mice that selectively express high levels of Abeta40 with both Tg2576 (APPswe, K670N+M671L) mice and BRI-Abeta42A mice expressing Abeta42 selectively and analyzed parenchymal and cerebrovascular Abeta deposition in the bitransgenic mice compared with their singly transgenic littermates. In the bitransgenic mice, the increased steady-state levels of Abeta40 decreased Abeta deposition by 60-90%. These results demonstrate that Abeta42 and Abeta40 have opposing effects on amyloid deposition: Abeta42 promotes amyloid deposition but Abeta40 inhibits it. In addition, increasing Abeta40 levels protected BRI-Abeta40/Tg2576 mice from the premature-death phenotype observed in Tg2576 mice. The protective properties of Abeta40 with respect to amyloid deposition suggest that strategies that preferentially target Abeta40 may actually worsen the disease course and that selective increases in Abeta40 levels may actually reduce the risk for development of AD.

    Funded by: NIA NIH HHS: R01 AG022595

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2007;27;3;627-33

  • Presenilin/gamma-secretase and alpha-secretase-like peptidases cleave human MHC Class I proteins.

    Carey BW, Kim DY and Kovacs DM

    Neurobiology of Disease Laboratory, Genetics and Aging Research Unit/MIND, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, 114 16th St., Charlestown, MA 02129, USA.

    HLA (human leucocyte antigen)-A2 is an MHC Class I protein with primary functions in T-cell development and initi-ation of immune cell responses. MHC I proteins also play roles in intercellular adhesion, apoptosis, cell proliferation and neuronal plasticity. By utilizing a sequence comparison analysis, we recently identified HLA-A2 as a potential substrate for the Alzheimer's disease-associated PS1 (presenilin 1)/gamma-secretase. alpha-Secretase-like membrane metalloproteinases are responsible for an initial shedding event, partially mediated by ADAM (a disinteg-rin and metalloproteinase)-10. Accordingly, activation or inhibition of alpha-secretase-like membrane metalloproteinases directly modulated levels of a 14 kDa HLA-A2 CTF (C-terminal frag-ment) in CHO (Chinese-hamster ovary) cells. To show that the HLA-A2 CTF is subsequently cleaved by PS1/gamma-secretase, we re-duced its activity in cell lines stably expressing HLA-A2 and in Jurkat T-cells expressing endogenous MHC I. Treatment with specific PS1/gamma-secretase inhibitors or expression of a dominant-negative construct led to a significant accumulation of HLA-A2 CTFs. We also identified the PS1/gamma-secretase cleavage product of HLA-A2 CTF, termed HLA-A2 intracellular domain, in cell-free and cell-based experiments. In the absence of proteasome inhibitors, HLA-A2 intracellular domain underwent rapid degrad-ation. These data indicate that MHC I proteins undergo extra-cellular domain cleavage mediated by alpha-secretases and the cleavage product is subsequently cleaved by PS1/gamma-secretase.

    The Biochemical journal 2007;401;1;121-7

  • Time-dependent DNA condensation induced by amyloid beta-peptide.

    Yu H, Ren J and Qu X

    Division of Biological Inorganic Chemistry, Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Graduate School of the Chinese Academy of Sciences, Changchun, Jilin, China.

    The major protein component of the amyloid deposition in Alzheimer's disease is a 39-43 residue peptide, amyloid beta (Abeta). Abeta is toxic to neurons, although the mechanism of neurodegeneration is uncertain. Evidence exists for non-B DNA conformation in the hippocampus of Alzheimer's disease brains, and Abeta was reportedly able to transform DNA conformation in vitro. In this study, we found that DNA conformation was altered in the presence of Abeta, and Abeta induced DNA condensation in a time-dependent manner. Furthermore, Abeta sheets, serving as condensation nuclei, were crucial for DNA condensation, and Cu(2+) and Zn(2+) ions inhibited Abeta sheet-induced DNA condensation. Our results suggest DNA condensation as a mechanism of Abeta toxicity.

    Biophysical journal 2007;92;1;185-91

  • Altered subcellular distribution of the Alzheimer's amyloid precursor protein under stress conditions.

    Domingues SC, Henriques AG, Wu W, Da Cruz e Silva EF and Da Cruz e Silva OA

    Neuroscience Laboratory, Centre for Cell Biology, University of Aveiro, Aveiro, Portugal.

    Altered metabolism of the Alzheimer's amyloid precursor protein (APP) appears to be a key event in the pathogenesis of Alzheimer's disease (AD), and both altered phosphorylation and oxidative stress appear to affect the production of the toxic Abeta fragment. Our results show that altered processing of APP was observed under conditions of stress induced by sodium azide in the presence of 2-deoxy-D-glucose (2DG). As previously reported, the production of the secreted fragment of APP (sAPP) was inhibited. Using APP-GFP fusion proteins, we show that 2DG causes the accumulation/delay of APP in the endoplasmic reticulum (ER)/Golgi (G). The 751 isoform accumulated preferentially in the G, whereas the 695 isoform was blocked preferentially at the ER. This effect was augmented in the presence of sodium azide. APP subcellular distribution was also affected at the plasma membrane. The involvement of protein phosphorylation in APP subcellular localization was reinforced by the effect of drugs, such as phorbol 12-myristate 13-acetate (PMA), since APP was completely depleted from the membrane in the presence of 2DG and PMA. Thus, the hypothesis that APP is processed in a phosphorylation-dependent manner and that this may be of clinical relevance appears to hold true even under stress conditions. Our results provide evidence for a role of protein phosphorylation in APP sorting under stress conditions and contribute to the understanding of the molecular basis of AD.

    Annals of the New York Academy of Sciences 2007;1096;184-95

  • Amyloid precursor protein and Presenilin 1 interaction studied by FRET in human H4 cells.

    Nizzari M, Venezia V, Bianchini P, Caorsi V, Diaspro A, Repetto E, Thellung S, Corsaro A, Carlo P, Schettini G, Florio T and Russo C

    Pharmacology, Department of Oncology, Biology and Genetics, University of Genova, Genova, Italy.

    The mayor pathologic hallmarks of Alzheimer's disease (AD) are senile plaque and neurofibrillary tangles. Senile plaque are primarily made up of deposits of amyloid-beta protein, a proteolytic product derived from the amyloid precursor protein (APP). APP is a transmembrane protein detected into the endoplasmic reticulum, in the Golgi apparatus, at the cell surface, recycled by endocytosis to endosomes, whose physiological function is unclear. Presenilins (PS), are a component of gamma-secretase complex that cleave alpha-CTFs (carboxy-terminal fragment), or beta-CTFs, leaving 40 or 42 amino acids amyloid-beta peptides and 58 or 56 amino acids intracellular domains (AICD). Where the amyloid-beta peptides is generated is not clear. The study of APP-PS interaction in specific cell compartments provides a good opportunity to light upon the molecular mechanisms regulating the activity of the "gamma-secretase complex," and where beta-amyloid is generated. In our study we used a biophysical assay of protein proximity: fluorescence resonance energy transfer (FRET), that can provide information about molecular interactions when two proteins are in the close proximity (<10 nm), to examine the subcellular localization and interaction between APP and PS1 in human neuroglioma cells (H4). Confocal microscopic analysis reveals extensive colocalization in different cells' compartment, and centrosomal or microtubule organizing center (MTOC) localization of APP and PS1, but not necessarily a close molecular interaction. We used FRET to determine if APP and PS1 interact at the cell centrosome. FRET data suggest a close interaction between APP and PS1 in subcellular compartments and at the centrosome of H4 cells. Using this approach we show that APP and PS1 are closely associated in the centrosomes of the H4 cell.

    Annals of the New York Academy of Sciences 2007;1096;249-57

  • Differential distribution of Alzheimer's amyloid precursor protein family variants in human sperm.

    Fardilha M, Vieira SI, Barros A, Sousa M, Da Cruz e Silva OA and Da Cruz e Silva EF

    Signal Transduction Laboratory, Centre for Cell Biology, University of Aveiro, Aveiro, Portugal.

    The Alzheimer's amyloid precursor protein (APP) is a type I transmembrane glycoprotein with receptor-like characteristics that originates the Abeta peptide by proteolytic processing. Abeta is potentially cytotoxic and the major component of the cerebral amyloid plaques in Alzheimer's disease (AD) patients. APP is known to be ubiquitously expressed in mammalian cells, with a broad tissue distribution, and Abeta deposition has been reported to occur also in many cells outside the nervous system. Although many putative functions have been suggested for APP, its precise physiological role remains to be elucidated. As several results point to a role of chronic inflammation in AD pathogenesis and suggest that AD might be a systemic disorder, the importance of APP function in non-neuronal cells/tissues has gained increased relevance. Previous studies have shown that amyloid precursor-like protein 2 (APLP2) is highly expressed in testis and sperm, but failed to unambiguously prove the presence of APP itself in mammalian sperm. The use of a battery of available antibodies that detect APP-specific epitopes or epitopes shared with other APP family members, revealed quite distinct distributions in human sperm. Our results are consistent with previous observations of APLP2 in sperm and unequivocally demonstrate the presence of APP itself in human sperm, thus suggesting a putative role for this important protein in sperm function.

    Annals of the New York Academy of Sciences 2007;1096;196-206

  • Modulation of gene expression and cytoskeletal dynamics by the amyloid precursor protein intracellular domain (AICD).

    Müller T, Concannon CG, Ward MW, Walsh CM, Tirniceriu AL, Tribl F, Kögel D, Prehn JH and Egensperger R

    Institute of Pathology and Neuropathology, University Hospital Essen, D-45122 Essen, Germany. thorsten.t.mueller@rub.de

    Amyloidogenic processing of the amyloid precursor protein (APP) results in the generation of beta-amyloid, the main constituent of Alzheimer plaques, and the APP intracellular domain (AICD). Recently, it has been demonstrated that AICD has transactivation potential; however, the targets of AICD-dependent gene regulation and hence the physiological role of AICD remain largely unknown. We analyzed transcriptome changes during AICD-dependent gene regulation by using a human neural cell culture system inducible for expression of AICD, its coactivator FE65, or the combination of both. Induction of AICD was associated with increased expression of genes with known function in the organization and dynamics of the actin cytoskeleton, including alpha2-Actin and Transgelin (SM22). AICD target genes were also found to be differentially regulated in the frontal cortex of Alzheimer's disease patients compared with controls as well as in AICD/FE65 transiently transfected murine cortical neurons. Confocal image analysis of neural cells and cortical neurons expressing both AICD and FE65 confirmed pronounced changes in the organization of the actin cytoskeleton, including the destabilization of actin fibers and clumping of actin at the sites of cellular outgrowth. Our data point to a role of AICD in developmental and injury-related cytoskeletal dynamics in the nervous system.

    Molecular biology of the cell 2007;18;1;201-10

  • Release of beta-amyloid from high-density platelets: implications for Alzheimer's disease pathology.

    Casoli T, Di Stefano G, Giorgetti B, Grossi Y, Balietti M, Fattoretti P and Bertoni-Freddari C

    Neurobiology of Aging Laboratory, INRCA Research Department, Via Birarelli 8, 60121 Ancona, Italy. t.casoli@inrca.it

    The main component of Alzheimer's disease (AD) senile plaques in the brain is amyloid-beta peptide (Abeta), a proteolytic fragment of the amyloid precursor protein (APP). Platelets contain both APP and Abeta and much evidence suggests that these cells may represent a useful tool to study both amyloidogenic and nonamyloidogenic pathways of APP processing. It has been demonstrated that platelets activated by physiological agonists, such as thrombin and collagen, specifically secrete Abeta ending at residue 40. To verify whether APP beta-processing could be observed also in an in vitro system of highly concentrated platelets, we measured the Abeta released in the incubation media of 5 x 10(9) platelets/mL by enzyme-linked immunosorbent assay (ELISA). The activation status of platelets was investigated by ultrastructural analysis. We found that Abeta(40) levels were significantly higher in incubation media of 5 x 10(9)/mL platelets in comparison with 10(8)/mL platelets (normalized values), while Abeta(42) levels were not affected by cell density. The ultrastructural analysis showed platelets at different phases of activation: some platelets were at earlier stage, characterized by granule swelling and dilution, others had granules concentrated in a compact mass in the cell centers within constricted rings of circumferential microtubules (later stage). Normally concentrated cells had the characteristic morphology of resting platelets. Our data suggest that high-density platelets undergo activation likely by increased frequency of platelet-platelet collisions. This, in turn, determines the activation of APP beta-processing with consequent release of Abeta(40). Investigating the biochemical pathways triggering Abeta secretion in platelets might provide important information for developing tools to modulate this phenomenon in AD brains.

    Annals of the New York Academy of Sciences 2007;1096;170-8

  • Beta 2-microglobulin amyloid deposit in HLA-B27 transgenic rats.

    Fukunishi S, Yoh K, Kamae S and Yoshiya S

    Department of Orthopaedic Surgery, Hyogo college of Medicine, 1-1 Mukogawa-cho, Nishinomiya, 663-8501, Japan. f9457@hyo-med.ac.jp

    Beta 2-microglobulin (beta 2-m) amyloid deposition develops serious orthopedic complications in patients with long-term hemodialysis. However, the exact pathogenesis of amyloid deposition in patients with dialysis is unknown. We used transgenic rats with HLA-B27 and beta 2-m to develop an in vivo animal model with beta 2-m amyloid-associated disorders to investigate the mechanism of formation and to report histological findings of beta 2-m amyloid deposition. Transgenic rats were divided into two groups: group 1, no treatment; group 2, arthritis induced by type II collagen. A large number of cells labeled with beta 2-m were observed in the bone marrow and synovium of the knee joint in transgenic rats. In addition, amyloid deposition, identified by Congo red staining, was found only in the knee joints of the transgenic rats with collagen-induced arthritis. Immunostaining with beta 2-m demonstrated the same pattern of tissue distribution as Congo red in serial sections. We hypothesized that elevated serum beta 2-m level-associated local chronic inflammation leads to the development of amyloid deposits and resultant arthropathy.

    Modern rheumatology 2007;17;5;380-4

  • Immunotherapy against APP beta-secretase cleavage site improves cognitive function and reduces neuroinflammation in Tg2576 mice without a significant effect on brain abeta levels.

    Rakover I, Arbel M and Solomon B

    Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv, Tel-Aviv, Israel.

    Active and passive immunization methodologies against amyloid-beta (Abeta) are employed to clear and reduce cerebral Abetatowards treatment of Alzheimer's disease (AD) patients. The therapeutic potential of these antibodies in AD patients is limited because of adverse inflammatory reactions and cerebral hemorrhage, which are associated with the treatment. We propose a novel approach to inhibit Abeta production via antibodies against the beta-secretase cleavage site of the amyloid precursor protein (APP). Such an approach limits APP processing by beta-secretase, mainly through the endocytic pathway, and overcomes some of the limitations of BACE inhibition. Anti-APP beta-site antibodies, tested in a cellular model expressing wild-type APP, were found to bind full-length APP, internalize into the cells and interfere with BACE activity, inhibiting both intra- and extracellular Abeta peptide formation.

    Methods: We investigated the effect of anti-beta-site antibodies in an AD animal model regarding antibody efficacy, as well as possible adverse effects in the brain and periphery that may result from antibody treatment.

    Here, we show that long-term systemic administration of anti-APP beta-site antibodies to Tg2576 transgenic mice improved mouse cognitive functions associated with a reduction in both brain inflammation and the incidence of microhemorrhage. Furthermore, antibody treatment did not induce any peripheral autoimmunity responses. In spite of the beneficial effects observed in antibody-treated mice, brain Abeta levels were not altered as a result of antibody treatment.

    Neuro-degenerative diseases 2007;4;5;392-402

  • Increase in beta-amyloid levels in cerebrospinal fluid of children with Down syndrome.

    Englund H, Annerén G, Gustafsson J, Wester U, Wiltfang J, Lannfelt L, Blennow K and Höglund K

    Department of Public Health and Caring Sciences, Section of Molecular Geriatrics, Uppsala University, and Department of Women's and Children's Health, Uppsala University Children's Hospital, Sweden.

    Background: Individuals with Down syndrome (DS) invariably develop Alzheimer's disease (AD) during their life span. It is therefore of importance to study young DS patients when trying to elucidate early events in AD pathogenesis.

    Aim: To investigate how levels of different amyloid-beta (Abeta) peptides, as well as tau and phosphorylated tau, in cerebrospinal fluid (CSF) from children with DS change over time. The first CSF sample was taken at 8 months and the following two samples at 20-40 and 54 months of age.

    Results: Individual levels of the Abeta peptides, as well as total Abeta levels in CSF increased over time when measured with Western blot. Tau in CSF decreased whereas there was no change in levels of phosphorylated tau over time.

    Conclusion: The increasing levels of Abeta in CSF during early childhood of DS patients observed in this study are probably due to the trisomy of the Abeta precursor APP, which leads to an overproduction of Abeta. Despite the increased CSF concentrations of Abeta, there were no signs of an AD-indicating tau pattern in CSF, since the levels of total tau decreased and phosphorylated tau remained unchanged. This observation further strengthens the theory of Abeta pathology preceding tau pathology in AD.

    Dementia and geriatric cognitive disorders 2007;24;5;369-74

  • Localizations of endogenous APP/APP-proteolytic products are consistent with microtubular transport.

    Zitnik G, Wang L, Martin GM and Hu Q

    Department of Pathology, University of Washington, Seattle, WA 98195-7470, USA. gzitnik@u.washington.edu

    Dementia of the Alzheimer type (DAT) is associated with the accumulation of beta-amyloid (A beta) peptides derived from beta-amyloid precursor protein (APP). Goldstein and coworkers have suggested that APP acts as a cargo receptor connecting post-Golgi vesicles and motor proteins. Sisodia and colleagues have suggested that APP is a passive passenger within the vesicles. Both views predict that one should be able to visualize colocalizations of APP with microtubules, the object of the present investigation. To avoid possible artifacts created by APP overexpression, we studied endogenous expression in a human neuroblastoma cell line (SK-N-SH). Using high resolution fluorescence microscopy and antibodies specific for the amino termini of APP and A beta sequences, we found that endogenous APP and A beta peptide immunoreactivities colocalized with microtubules in interphase cells. Disruption of microtubules, followed by fixation at various time points during repolymerization, allowed us to observe the sequence and timing of these colocalizations in interphase cells. In addition, to our surprise, we found that A beta immunoreactivities colocalize with the mitotic spindle, a bundle of specialized microtubules. Because of the condensed cytoplasm found in neurons, we suggest that SK-N-SH cells might be a more convenient experimental system for exploring the mechanisms that underlie these protein localizations and the pathology that might result from altered APP protein structure and function.

    Funded by: NIA NIH HHS: AG019711-01

    Journal of molecular neuroscience : MN 2007;31;1;59-68

  • Tyr687 dependent APP endocytosis and Abeta production.

    Rebelo S, Vieira SI, Esselmann H, Wiltfang J, da Cruz e Silva EF and da Cruz e Silva OA

    Laboratório de Neurociências, Centro de Biologia Celular, Universidade de Aveiro, Aveiro 3810-193, Portugal.

    The neurotoxic Abeta peptide is derived by proteolytic processing from the Alzheimer's amyloid precursor protein (APP), whose short cytoplasmic domain contains several phosphorylatable amino acids. The latter can be phosphorylated 'in vitro' and 'in vivo,' and in some cases phosphorylation appears to be associated with the disease condition. Using APP-GFP fusion proteins to monitor APP processing, the role of Tyr687 was addressed by mimicking its constitutive phosphorylation (Y687E) and dephosphorylation (Y687F). Contrasting effects on subcellular APP distribution were observed. Y687E-APP-GFP was targeted to the membrane but could not be detected in transferrin containing vesicular structures, and exhibited a concomitant and dramatic decrease in Abeta production. In contrast, Y687F-APP-GFP was endocytosed similarly to wild type APP, but was relatively favoured for beta-secretase cleavage. Overall, Tyr687 appears to be a critical residue determining APP targeting and processing via different pathways, including endocytosis and retrograde transport. Significantly, from a disease perspective, mimicking Tyr687 phosphorylation resulted in a hitherto undescribed inhibition of Abeta production. Our results provide novel insights into the role of direct APP phosphorylation on APP targeting, processing and Abeta production.

    Journal of molecular neuroscience : MN 2007;32;1;1-8

  • Deficits in synaptic transmission and learning in amyloid precursor protein (APP) transgenic mice require C-terminal cleavage of APP.

    Saganich MJ, Schroeder BE, Galvan V, Bredesen DE, Koo EH and Heinemann SF

    Salk Institute for Biological Studies, La Jolla, California 92037, USA. saganich@salk.edu

    Synaptic dysfunction has been shown to be one of the earliest correlates of disease progression in animal models of Alzheimer's disease. Amyloid-beta protein (Abeta) is thought to play an important role in disease-related synaptic dysfunction, but the mechanism by which Abeta leads to synaptic dysfunction is not understood. Here we describe evidence that cleavage of APP in the C terminus may be necessary for the deficits present in APP transgenic mice. In APP transgenic mice with a mutated cleavage site at amino acid 664, normal synaptic transmission, synaptic plasticity, and learning were maintained despite the presence of elevated levels of APP, Abeta42, and even plaque accumulation. These results indicate that cleavage of APP may play a critical role in the development of synaptic and behavioral dysfunction in APP transgenic mice.

    Funded by: NIA NIH HHS: AG00216, AG05131, P01 AG10435-12; NINDS NIH HHS: 5 R01 NS2809, NS45093

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2006;26;52;13428-36

  • Reduction of soluble Abeta and tau, but not soluble Abeta alone, ameliorates cognitive decline in transgenic mice with plaques and tangles.

    Oddo S, Vasilevko V, Caccamo A, Kitazawa M, Cribbs DH and LaFerla FM

    Departments of Neurobiology and Behavior and Neurology, and Institute for Brain Aging and Dementia, University of California, Irvine, California 92697, USA.

    Increasing evidence points to soluble assemblies of aggregating proteins as a major mediator of neuronal and synaptic dysfunction. In Alzheimer disease (AD), soluble amyloid-beta (Abeta) appears to be a key factor in inducing synaptic and cognitive abnormalities. Here we report the novel finding that soluble tau also plays a role in the cognitive decline in the presence of concomitant Abeta pathology. We describe improved cognitive function following a reduction in both soluble Abeta and tau levels after active or passive immunization in advanced aged 3xTg-AD mice that contain both amyloid plaques and neurofibrillary tangles (NFTs). Notably, reducing soluble Abeta alone did not improve the cognitive phenotype in mice with plaques and NFTs. Our results show that Abeta immunotherapy reduces soluble tau and ameliorates behavioral deficit in old transgenic mice.

    Funded by: NIA NIH HHS: AG0212982, AG20241

    The Journal of biological chemistry 2006;281;51;39413-23

  • The intracellular domain of the amyloid precursor protein (AICD) enhances the p53-mediated apoptosis.

    Ozaki T, Li Y, Kikuchi H, Tomita T, Iwatsubo T and Nakagawara A

    Division of Biochemistry, Chiba Cancer Center Research Institute, Chiba 260-8717, Japan.

    Amyloid precursor protein (APP)-derived intracellular domain (AICD) has a cytotoxic effect on neuronal cells and also participates in the regulation of gene transactivation. However, the precise molecular mechanisms behind the AICD-mediated apoptosis remain unknown. In this study, we have demonstrated that AICD interacts with p53 and enhances its transcriptional and pro-apoptotic functions. p53 was induced to be accumulated and associated with APP in response to cisplatin. Indeed, APP-C57 was co-immunoprecipitated with the endogenous p53. Enforced expression of APP-C57 or APP-C59 in U2OS cells bearing wild-type p53 led to an increase in number of apoptotic cells, whereas they had undetectable effects on p53-deficient H1299 cells, suggesting that AICD contributes to the activation of the p53-mediated apoptotic pathway. Consistent with this notion, the p53-mediated transcriptional activation and apoptosis were significantly enhanced by co-expression with APP-C57 or APP-C59. Thus, our present results strongly suggest that AICD triggers apoptosis through the p53-dependent mechanisms.

    Biochemical and biophysical research communications 2006;351;1;57-63

  • Neuronal pentraxin 1 contributes to the neuronal damage evoked by amyloid-beta and is overexpressed in dystrophic neurites in Alzheimer's brain.

    Abad MA, Enguita M, DeGregorio-Rocasolano N, Ferrer I and Trullas R

    Neurobiology Unit, Institut d'Investigacions Biomèdiques de Barcelona, Consejo Superior de Investigaciones Científicas, Institut d'Investigacions Biomèdiques August Pi i Sunyer, 08036 Barcelona, Spain.

    Accumulation of amyloid-beta (Abeta) is thought to play a central role in the progressive loss of synapses, the neurite damage, and the neuronal death that are characteristic in brains affected by Alzheimer's disease. However, the mechanisms through which Abeta produces such neurotoxicity remain unclear. Because Abeta depresses synaptic activity, we investigated whether the neurotoxicity of Abeta depends on the expression of NP1, a protein involved in excitatory synapse remodeling that has recently been shown to mediate neuronal death induced by reduction in neuronal activity in mature neurons. We found that treatment of cortical neurons in culture with Abeta produces a marked increase in NP1 protein that precedes apoptotic neurotoxicity. Silencing NP1 gene expression by RNA interference (short hairpin RNA for RNA interference) prevents the loss of synapses, the reduction in neurite outgrowth, and the apoptosis evoked by Abeta. Transgene overexpression of NP1 reproduced these neurotoxic effects of Abeta. Moreover, we found that NP1 was increased in dystrophic neurites of brains from patients with sporadic late-onset Alzheimer's disease. Dual immunohistochemistry for NP1 and tau showed that NP1 colocalizes with tau deposits in dystrophic neurites. Furthermore, NP1 colocalized with SNAP-25 (synaptosomal-associated protein of 25 kDa) in the majority of dystrophic neurites surrounding amyloid deposits. NP1 was also increased in cell processes surrounding amyloid plaques in the cerebral cortex and hippocampus of APP/PS1 (mutant amyloid precursor protein/presenilin 1) transgenic mice. These findings show that NP1 is a key factor for the synapse loss, the neurite damage, and the apoptotic neuronal death evoked by Abeta and indicate that Abeta contributes to the pathology of Alzheimer's disease by regulating NP1 expression.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2006;26;49;12735-47

  • Lipid-induced beta-amyloid peptide assemblage fragmentation.

    Widenbrant MJ, Rajadas J, Sutardja C and Fuller GG

    Department of Chemical Engineering, Stanford University, Stanford, CA, USA.

    Alzheimer's disease is the most common cause of dementia and is widely believed to be due to the accumulation of beta-amyloid peptides (Abeta) and their interaction with the cell membrane. Abetas are hydrophobic peptides derived from the amyloid precursor proteins by proteolytic cleavage. After cleavage, these peptides are involved in a self-assembly-triggered conformational change. They are transformed into structures that bind to the cell membrane, causing cellular degeneration. However, it is not clear how these peptide assemblages disrupt the structural and functional integrity of the membrane. Membrane fluidity is one of the important parameters involved in pathophysiology of disease-affected cells. Probing the Abeta aggregate-lipid interactions will help us understand these processes with structural detail. Here we show that a fluid lipid monolayer develop immobile domains upon interaction with Abeta aggregates. Atomic force microscopy and transmission electron microscopy data indicate that peptide fibrils are fragmented into smaller nano-assemblages when interacting with the membrane lipids. Our findings could initiate reappraisal of the interactions between lipid assemblages and Abeta aggregates involved in Alzheimer's disease.

    Biophysical journal 2006;91;11;4071-80

  • AbetaPP-overexpression and proteasome inhibition increase alphaB-crystallin in cultured human muscle: relevance to inclusion-body myositis.

    Wojcik S, Engel WK, McFerrin J, Paciello O and Askanas V

    USC Neuromuscular Center, Department of Neurology, University of Southern California Keck School of Medicine, Good Samaritan Hospital, Los Angeles, CA 90017-1912, USA.

    Amyloid-beta precursor protein (AbetaPP) and its fragment amyloid-beta (Abeta) are increased in s-IBM muscle fibers and appear to play an important role in the pathogenic cascade. alphaB-Crystallin (alphaBC) was shown immunohistochemically to be accumulated in s-IBM muscle fibers, but the stressor(s) influencing alphaBC accumulation was not identified. We now demonstrate, using our experimental IBM model based on genetic overexpression of AbetaPP into cultured normal human muscle fibers, that: (1) AbetaPP overexpression increased alphaBC 3.7-fold (p=0.025); (2) additional inhibition of proteasome with epoxomicin increased alphaBC 7-fold (p=0.002); and (3) alphaBC physically associated with AbetaPP and Abeta oligomers. We also show that in biopsied s-IBM muscle fibers, alphaBC was similarly increased 3-fold (p=0.025) and physically associated with AbetaPP and Abeta oligomers. We propose that increased AbetaPP is a stressor increasing alphaBC expression in s-IBM muscle fibers. Determining the consequences of alphaBC association with Abeta oligomers could have clinical therapeutic relevance.

    Funded by: NIA NIH HHS: AG16768, R37 AG016768, R37 AG016768-07

    Neuromuscular disorders : NMD 2006;16;12;839-44

  • Beta-amyloid aggregation in human brains with cerebrovascular lesions.

    Aho L, Jolkkonen J and Alafuzoff I

    Department of Clinical Medicine, Neurology, Kuopio University, P-O-B 1647, Harjulantie 1, Kuopio, Finland.

    The present study assessed beta-amyloid (Abeta) protein aggregates in postmortem human brains in subjects who had experienced stroke to examine the proposed association between ischemic stress and the accumulation of Abeta reported in rodents.

    Methods: A sample of 484 postmortem brains from nondemented subjects, lacking isocortical neurodegenerative pathology with verified cerebrovascular lesions, and 57 age-matched controls were assessed with respect to Abeta, Abeta40, and Abeta42 aggregates in the cortex and thalamus by immunohistochemical techniques.

    Results: The load of Abeta aggregates did not display a significant association with cerebrovascular lesions. The load of Abeta, Abeta40, and Abeta42 aggregates increased with age, and there was a tendency toward higher odds ratios for Abeta aggregates, though not statistically significant, in subjects with acute cerebrovascular lesions. In the oldest subjects with cerebrovascular lesions and with both thalamic and cortical Abeta aggregates, the load of thalamic Abeta42 was significantly higher than the load of Abeta40.

    Conclusions: Our findings indicate that cerebrovascular disease does not influence the load of Abeta, whereas a shift of aggregation from the Abeta40 to the Abeta42 residue is noted in the thalamus but only in aged subjects. It is impossible, however, to state whether this result is attributable to increased Abeta produ