G2Cdb::Gene report

Gene id
Gene symbol
Homo sapiens
microtubule-associated protein 1B
G00000549 (Mus musculus)

Databases (7)

ENSG00000131711 (Ensembl human gene)
4131 (Entrez Gene)
967 (G2Cdb plasticity & disease)
MAP1B (GeneCards)
157129 (OMIM)
Marker Symbol
HGNC:6836 (HGNC)
Protein Sequence
P46821 (UniProt)

Synonyms (1)

  • MAP5

Literature (40)

Pubmed - other

  • Defining the human deubiquitinating enzyme interaction landscape.

    Sowa ME, Bennett EJ, Gygi SP and Harper JW

    Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.

    Deubiquitinating enzymes (Dubs) function to remove covalently attached ubiquitin from proteins, thereby controlling substrate activity and/or abundance. For most Dubs, their functions, targets, and regulation are poorly understood. To systematically investigate Dub function, we initiated a global proteomic analysis of Dubs and their associated protein complexes. This was accomplished through the development of a software platform called CompPASS, which uses unbiased metrics to assign confidence measurements to interactions from parallel nonreciprocal proteomic data sets. We identified 774 candidate interacting proteins associated with 75 Dubs. Using Gene Ontology, interactome topology classification, subcellular localization, and functional studies, we link Dubs to diverse processes, including protein turnover, transcription, RNA processing, DNA damage, and endoplasmic reticulum-associated degradation. This work provides the first glimpse into the Dub interaction landscape, places previously unstudied Dubs within putative biological pathways, and identifies previously unknown interactions and protein complexes involved in this increasingly important arm of the ubiquitin-proteasome pathway.

    Funded by: NIA NIH HHS: AG085011, R01 AG011085, R01 AG011085-16; NIGMS NIH HHS: GM054137, GM67945, R01 GM054137, R01 GM054137-14, R01 GM067945

    Cell 2009;138;2;389-403

  • Microtubule-associated protein 1b, a neuronal marker involved in odontoblast differentiation.

    Maurin JC, Couble ML, Staquet MJ, Carrouel F, About I, Avila J, Magloire H and Bleicher F

    University of Lyon, Lyon, France. jean-christophe.maurin@univ-reims.fr

    Introduction: Map-1B belongs to the family of proteins that govern the dynamic state and organization of microtubules within cells. MAP-1B is a microtubule-associated protein highly expressed during the development of the nervous system. Its expression, regulated by the fragile X mental retardation protein (FMRP), is essential to stabilize microtubules during the elongation of dendrites and neurites. Other microtubules-associated molecules such as tau or MAP2 seem to act similarly. The aim of this work was to identify the MAP-1B expression in in vitro and in vivo human odontoblasts during development and carious processes. The expression of MAP2 and tau was also studied.

    In cultured cells, MAP-1B expression was analyzed by real-time polymerase chain reaction, flow cytometry, and Western blot. Its distribution was visualized by in situ hybridization and immunochemistry both in vitro and in vivo. The expression of FMRP, MAP2, and tau was identified by real-time polymerase chain reaction and immunochemistry.

    Results: MAP-1B is specifically expressed in odontoblasts from adult third molars as well as incisor germs from human embryos. In adult carious teeth, it is also expressed in newly differentiated dentin-forming cells. In vitro, MAP-1B expression is related to the differentiation state of odontoblasts. MAP-1B clearly underlines the cellular architecture of cell bodies and processes of differentiated cells. FMRP, MAP2, and tau are also detected in vivo.

    Conclusion: On the basis of these data, MAP-1B could be considered as a new protein involved in the terminal differentiation of odontoblasts.

    Journal of endodontics 2009;35;7;992-6

  • Polymorphisms in genes involved in neurodevelopment may be associated with altered brain morphology in schizophrenia: preliminary evidence.

    Gregório SP, Sallet PC, Do KA, Lin E, Gattaz WF and Dias-Neto E

    Laboratório de Neurociências (LIM-27), Departmento e Instituto de Psiquiatria, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil.

    An abnormality in neurodevelopment is one of the most robust etiologic hypotheses in schizophrenia (SZ). There is also strong evidence that genetic factors may influence abnormal neurodevelopment in the disease. The present study evaluated in SZ patients, whose brain structural data had been obtained with magnetic resonance imaging (MRI), the possible association between structural brain measures, and 32 DNA polymorphisms, located in 30 genes related to neurogenesis and brain development. DNA was extracted from peripheral blood cells of 25 patients with schizophrenia, genotyping was performed using diverse procedures, and putative associations were evaluated by standard statistical methods (using the software Statistical Package for Social Sciences - SPSS) with a modified Bonferroni adjustment. For reelin (RELN), a protease that guides neurons in the developing brain and underlies neurotransmission and synaptic plasticity in adults, an association was found for a non-synonymous polymorphism (Val997Leu) with left and right ventricular enlargement. A putative association was also found between protocadherin 12 (PCDH12), a cell adhesion molecule involved in axonal guidance and synaptic specificity, and cortical folding (asymmetry coefficient of gyrification index). Although our results are preliminary, due to the small number of individuals analyzed, such an approach could reveal new candidate genes implicated in anomalous neurodevelopment in schizophrenia.

    Funded by: NCI NIH HHS: P30 CA016672

    Psychiatry research 2009;165;1-2;1-9

  • Molecular genetics of adult ADHD: converging evidence from genome-wide association and extended pedigree linkage studies.

    Lesch KP, Timmesfeld N, Renner TJ, Halperin R, Röser C, Nguyen TT, Craig DW, Romanos J, Heine M, Meyer J, Freitag C, Warnke A, Romanos M, Schäfer H, Walitza S, Reif A, Stephan DA and Jacob C

    ADHD Clinical Research Program, Molecular and Clinical Psychobiology, Department of Psychiatry, Psychosomatics and Psychotherapy, University of Wuerzburg, Fuechsleinstr. 15, 97080, Wuerzburg, Germany. kplesch@mail.uni-wuerzburg.de

    A genome-wide association (GWA) study with pooled DNA in adult attention-deficit/hyperactivity disorder (ADHD) employing approximately 500K SNP markers identifies novel risk genes and reveals remarkable overlap with findings from recent GWA scans in substance use disorders. Comparison with results from our previously reported high-resolution linkage scan in extended pedigrees confirms several chromosomal loci, including 16q23.1-24.3 which also reached genome-wide significance in a recent meta-analysis of seven linkage studies (Zhou et al. in Am J Med Genet Part B, 2008). The findings provide additional support for a common effect of genes coding for cell adhesion molecules (e.g., CDH13, ASTN2) and regulators of synaptic plasticity (e.g., CTNNA2, KALRN) despite the complex multifactorial etiologies of adult ADHD and addiction vulnerability.

    Journal of neural transmission (Vienna, Austria : 1996) 2008;115;11;1573-85

  • Microtubule-associated protein 1B light chain (MAP1B-LC1) negatively regulates the activity of tumor suppressor p53 in neuroblastoma cells.

    Lee SY, Kim JW, Jeong MH, An JH, Jang SM, Song KH and Choi KH

    Laboratory of Molecular Biology, Department of Life Science, College of Natural Sciences, Chung-Ang University, 221 Heuksuk-Dong, Dongjak-Ku, Seoul, Republic of Korea.

    The tumor suppressor and transcription factor p53 is a key modulator of cellular stress responses and can trigger apoptosis in many cell types, including neurons. In this study, we have shown that the Microtubule-Associated Protein 1B (MAP1B) light chain can interact with the tumor suppressor p53. We also demonstrate that both p53 and the MAP1B light chain (MAP1B-LC1) alter their localization from the cytoplasm to the nucleus when neuroblastoma cells, SH-SY5Y, are treated with doxorubicin. Additionally, we demonstrate that the MAP1B-LC1 negatively regulates p53-dependent transcriptional activity of a reporter construct driven by the p21 promoter. Consequently, MAP1B-LC1 binds to p53 and this interaction leads to the inhibition of doxorubicin-induced apoptosis in SH-SY5Y cells.

    FEBS letters 2008;582;19;2826-32

  • Amyloid-beta peptide binds to microtubule-associated protein 1B (MAP1B).

    Gevorkian G, Gonzalez-Noriega A, Acero G, Ordoñez J, Michalak C, Munguia ME, Govezensky T, Cribbs DH and Manoutcharian K

    Instituto de Investigaciones Biomedicas, Universidad Nacional Autonoma de Mexico, Apartado Postal 70228, Cuidad Universitaria, Mexico DF, CP 04510, Mexico. gokar@servidor.unam.mx <gokar@servidor.unam.mx&gt;

    Extracellular and intraneuronal formation of amyloid-beta aggregates have been demonstrated to be involved in the pathogenesis of Alzheimer's disease. However, the precise mechanism of amyloid-beta neurotoxicity is not completely understood. Previous studies suggest that binding of amyloid-beta to a number of targets have deleterious effects on cellular functions. In the present study we have shown for the first time that amyloid-beta 1-42 bound to a peptide comprising the microtubule binding domain of the heavy chain of microtubule-associated protein 1B by the screening of a human brain cDNA library expressed on M13 phage. This interaction may explain, in part, the loss of neuronal cytoskeletal integrity, impairment of microtubule-dependent transport and synaptic dysfunction observed previously in Alzheimer's disease.

    Funded by: NIA NIH HHS: AG 023534, AG-20241, R01 AG020241, R21 AG023534, R21 AG023534-01, R21 AG023534-02; NINDS NIH HHS: NS-050895, R01 NS050895

    Neurochemistry international 2008;52;6;1030-6

  • DAPK-1 binding to a linear peptide motif in MAP1B stimulates autophagy and membrane blebbing.

    Harrison B, Kraus M, Burch L, Stevens C, Craig A, Gordon-Weeks P and Hupp TR

    University of Edinburgh Cancer Centre, Cell Signalling Unit, South Crewe Road, Edinburgh, Scotland, United Kingdom.

    DAPK-1 (death-activated protein kinase) has wide ranging functions in cell growth control; however, DAPK-1 interacting proteins that mediate these effects are not well defined. Protein-protein interactions are driven in part by linear interaction motifs, and combinatorial peptide libraries were used to identify peptide interfaces for the kinase domain of DAPK-1. Peptides bound to DAPK-1core kinase domain fragments had homology to the N-terminal domain of the microtubule-associated protein MAP1B. Immunobinding assays demonstrated that DAPK-1 can bind to the full-length human MAP1B, a smaller N-terminal miniprotein containing amino acids 1-126 and the 12-amino acid polypeptides acquired by peptide selection. Amino acid starvation of cells induced a stable immune complex between MAP1B and DAPK-1, identifying a signal that forms the endogenous complex in cells. DAPK-1 and MAP1B co-expression form a synthetic lethal interaction as they cooperate to induce growth inhibition in a clonogenic assay. In cells, two co-localizing populations of DAPK-1 and MAP1B were observed using confocal microscopy; one pool co-localized with MAP1B plus tubulin, and a second pool co-localized with MAP1B plus cortical F-actin. Reduction of MAP1B protein using short interfering RNA attenuated DAPK-1-stimulated autophagy. Transfected MAP1B can synergize with DAPK-1 to stimulate membrane blebbing, whereas reduction of MAP1B using short interfering RNA attenuates DAPK-1 membrane blebbing activity. The autophagy inhibitor 3-methyladenine inhibits the DAPK-1 plus MAP1B-mediated membrane blebbing. These data highlight the utility of peptide aptamers to identify novel binding interfaces and highlight a role for MAP1B in DAPK-1-dependent signaling in autophagy and membrane blebbing.

    Funded by: Cancer Research UK; Medical Research Council: G0400034, G9900989

    The Journal of biological chemistry 2008;283;15;9999-10014

  • Modulation of 5-HT3 receptor desensitization by the light chain of microtubule-associated protein 1B expressed in HEK 293 cells.

    Sun H, Hu XQ, Emerit MB, Schoenebeck JC, Kimmel CE, Peoples RW, Miko A and Zhang L

    Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, TS24, Bethesda, MD 20892, USA.

    Regulation of ligand-gated ion channel (LGIC) function and trafficking by cytoskeleton proteins has been the topic of recent research. Here, we report that the light chain (LC1) of microtubule-associated protein 1B (MAP1B) specifically interacted with the 5-HT(3A) receptor, a predominant serotonin-gated ion channel in the brain. LC1 and 5-HT(3A) receptors were colocalized in central neurons and in HEK 293 cells expressing 5-HT(3A) receptors. LC1 reduced the steady-state density of 5-HT(3A) receptors at the membrane surface of HEK 293 cells and significantly accelerated receptor desensitization time constants from 3.8 +/- 0.3 s to 0.8 +/- 0.1 s. However, LC1 did not significantly alter agonist binding affinity and single-channel conductance of 5-HT(3A) receptors. On the other hand, application of specific LC1 antisense oligonucleotides and nocodazole, a microtubule disruptor, significantly prolonged the desensitization time of the recombinant and native neuronal 5-HT(3) receptors by 3- to 6-fold. This kinetic change induced by nocodazole was completely rescued by addition of LC1 but not GABA(A) receptor-associated protein (GABARAP), suggesting that LC1 can specifically interact with 5-HT(3A) receptors. These observations suggest that the LC1-5-HT(3A) receptor interaction contributes to a mechanism that regulates receptor desensitization kinetics. Such dynamic regulation may play a role in reshaping the efficacy of 5-HT(3) receptor-mediated synaptic transmission.

    Funded by: Intramural NIH HHS

    The Journal of physiology 2008;586;3;751-62

  • Global, in vivo, and site-specific phosphorylation dynamics in signaling networks.

    Olsen JV, Blagoev B, Gnad F, Macek B, Kumar C, Mortensen P and Mann M

    Center for Experimental BioInformatics, Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense, Denmark.

    Cell signaling mechanisms often transmit information via posttranslational protein modifications, most importantly reversible protein phosphorylation. Here we develop and apply a general mass spectrometric technology for identification and quantitation of phosphorylation sites as a function of stimulus, time, and subcellular location. We have detected 6,600 phosphorylation sites on 2,244 proteins and have determined their temporal dynamics after stimulating HeLa cells with epidermal growth factor (EGF) and recorded them in the Phosida database. Fourteen percent of phosphorylation sites are modulated at least 2-fold by EGF, and these were classified by their temporal profiles. Surprisingly, a majority of proteins contain multiple phosphorylation sites showing different kinetics, suggesting that they serve as platforms for integrating signals. In addition to protein kinase cascades, the targets of reversible phosphorylation include ubiquitin ligases, guanine nucleotide exchange factors, and at least 46 different transcriptional regulators. The dynamic phosphoproteome provides a missing link in a global, integrative view of cellular regulation.

    Cell 2006;127;3;635-48

  • Heterotypic complex formation between subunits of microtubule-associated proteins 1A and 1B is due to interaction of conserved domains.

    Noiges R, Stroissnigg H, Tranciková A, Kalny I, Eichinger R and Propst F

    Max F. Perutz Laboratories, Department of Molecular Cell Biology, University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria, Europe.

    The microtubule-associated proteins MAP1A and MAP1B are related but distinct multi-subunit protein complexes that consist of heavy and light chains. The predominant forms of these complexes are homotypic, i.e. they consist of a MAP1A heavy chain associated with MAP1A light chains or a MAP1B heavy chain associated with MAP1B light chains, respectively. In addition, MAP1A and MAP1B can exchange subunits and form heterotypic complexes consisting of a MAP1A heavy chain associated with MAP1B light chains which might play a role in a transition period of neuronal differentiation. Here we extend previous findings by confirming that heterotypic MAP1B heavy chain-MAP1A light chain complexes also exist in the developing murine brain. We show that these complexes form through interaction of homologous domains conserved in heavy and light chains of MAP1A and MAP1B. Likewise, conserved domains of the MAP1A and MAP1B light chains account for formation of light chain heterodimers. By yeast 2-hybrid analysis we located the light chain binding domain on the heavy chain to amino acids 211-508, thereby defining a new functional subdomain.

    Biochimica et biophysica acta 2006;1763;10;1011-6

  • Interaction of PDZRhoGEF with microtubule-associated protein 1 light chains: link between microtubules, actin cytoskeleton, and neuronal polarity.

    Longhurst DM, Watanabe M, Rothstein JD and Jackson M

    Centre for Neuroscience Research, the University of Edinburgh, Edinburgh EH9 1QH, Scotland, United Kingdom.

    Rat (r) PDZRhoGEF, initially identified as a glutamate transporter EAAT4-associated protein, is a member of a novel RhoGEF subfamily. The N terminus of the protein contains a PDZ and a proline-rich domain, two motifs known to be involved in protein-protein interactions. By using the yeast two-hybrid approach, we screened for proteins that interact with the N terminus of rPDZRhoGEF. The light chain 2 of microtubule-associated protein 1 (LC2) was the only protein identified from the screen that does not contain a type I PDZ-binding motif at its extreme C terminus (-(S/T)Xphi-COOH, where phi is a hydrophobic amino acid). However, the C terminus does conform to a type II-binding motif (-phiXphi). We report here that rPDZRhoGEF interacts with LC2 via the PDZ domain, and the interaction is abolished by mutations in the carboxylate-binding loop. The specificity of the interaction was confirmed using GST fusion protein pull-down assays and coimmunoprecipitations. Expression of rPDZRhoGEF mutants that are unable to interact with proteins via the carboxylate-binding loop induced changes in cell morphology and actin organization. These mutants alter the activation of RhoGTPases, and coexpression of dominant-negative RhoGTPases prevent the morphological changes. Furthermore, in cells expressing wild type rPDZRhoGEF, drug-induced microtubule depolymerization produces changes in cell morphology that are similar to those induced by rPDZRhoGEF mutants. These results indicate that modulation of the guanine nucleotide exchange activity of rPDZRhoGEF through interaction with microtubule-associated protein light chains may coordinate microtubule integrity and the reorganization of actin cytoskeleton. This coordinated action of the actin and microtubular cytoskeletons is essential for the development and maintenance of neuronal polarity.

    The Journal of biological chemistry 2006;281;17;12030-40

  • Nuclear export factor family protein participates in cytoplasmic mRNA trafficking.

    Tretyakova I, Zolotukhin AS, Tan W, Bear J, Propst F, Ruthel G and Felber BK

    Human Retrovirus Pathogenesis Section, Vaccine Branch, Center for Cancer Research, NCI-Frederick, National Institutes of Health, Frederick, Maryland 21702, USA.

    In eukaryotes, the nuclear export of mRNA is mediated by nuclear export factor 1 (NXF1) receptors. Metazoans encode additional NXF1-related proteins of unknown function, which share homology and domain organization with NXF1. Some mammalian NXF1-related genes are expressed preferentially in the brain and are thought to participate in neuronal mRNA metabolism. To address the roles of NXF1-related factors, we studied the two mouse NXF1 homologues, mNXF2 and mNXF7. In neuronal cells, mNXF2, but not mNXF7, exhibited mRNA export activity similar to that of Tip-associated protein/NXF1. Surprisingly, mNXF7 incorporated into mobile particles in the neurites that contained poly(A) and ribosomal RNA and colocalized with Staufen1-containing transport granules, indicating a role in neuronal mRNA trafficking. Yeast two-hybrid interaction, coimmunoprecipitation, and in vitro binding studies showed that NXF proteins bound to brain-specific microtubule-associated proteins (MAP) such as MAP1B and the WD repeat protein Unrip. Both in vitro and in vivo, MAP1B also bound to NXF export cofactor U2AF as well as to Staufen1 and Unrip. These findings revealed a network of interactions likely coupling the export and cytoplasmic trafficking of mRNA. We propose a model in which MAP1B tethers the NXF-associated mRNA to microtubules and facilitates their translocation along dendrites while Unrip provides a scaffold for the assembly of these transport intermediates.

    The Journal of biological chemistry 2005;280;36;31981-90

  • Phosphoproteome analysis of HeLa cells using stable isotope labeling with amino acids in cell culture (SILAC).

    Amanchy R, Kalume DE, Iwahori A, Zhong J and Pandey A

    McKusick-Nathans Institute for Genetic Medicine and the Department of Biological Chemistry and Oncology, Johns Hopkins University, 733 N. Broadway, Baltimore, MD 21205, USA.

    Identification of phosphorylated proteins remains a difficult task despite technological advances in protein purification methods and mass spectrometry. Here, we report identification of tyrosine-phosphorylated proteins by coupling stable isotope labeling with amino acids in cell culture (SILAC) to mass spectrometry. We labeled HeLa cells with stable isotopes of tyrosine, or, a combination of arginine and lysine to identify tyrosine phosphorylated proteins. This allowed identification of 118 proteins, of which only 45 proteins were previously described as tyrosine-phosphorylated proteins. A total of 42 in vivo tyrosine phosphorylation sites were mapped, including 34 novel ones. We validated the phosphorylation status of a subset of novel proteins including cytoskeleton associated protein 1, breast cancer anti-estrogen resistance 3, chromosome 3 open reading frame 6, WW binding protein 2, Nice-4 and RNA binding motif protein 4. Our strategy can be used to identify potential kinase substrates without prior knowledge of the signaling pathways and can also be applied to profiling to specific kinases in cells. Because of its sensitivity and general applicability, our approach will be useful for investigating signaling pathways in a global fashion and for using phosphoproteomics for functional annotation of genomes.

    Funded by: NCI NIH HHS: CA 88843; NHLBI NIH HHS: HV 28180

    Journal of proteome research 2005;4;5;1661-71

  • Binding of microtubule-associated protein 1B to LIS1 affects the interaction between dynein and LIS1.

    Jiménez-Mateos EM, Wandosell F, Reiner O, Avila J and González-Billault C

    Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Campus de Cantoblanco, Cantoblanco 28049, Madrid, Spain.

    For neuronal migration to occur, the cell must undergo morphological changes that require modifications of the cytoskeleton. Several different MAPs (microtubule-associated proteins) or actin-binding proteins are proposed to be involved in the migration of neurons. Therefore we have specifically analysed how two members of the MAP family, MAP1B and LIS1 (lissencephaly-related protein 1), interact with one another and participate in neuronal migration. Our results indicate that, in hippocampal neurons, MAP1B and LIS1 co-localize, associate and interact with each another. The interaction between these two MAPs is regulated by the phosphorylation of MAP1B. Furthermore, this interaction interferes with the association between LIS1 and the microtubule-dependent molecular motor, dynein. Clearly, the differential binding of these cytoskeletal proteins could regulate the functions attributed to the LIS1-dynein complex, including those related to extension of the neural processes necessary for neuronal migration.

    The Biochemical journal 2005;389;Pt 2;333-41

  • Phosphoproteomic analysis of the developing mouse brain.

    Ballif BA, Villén J, Beausoleil SA, Schwartz D and Gygi SP

    Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.

    Proper development of the mammalian brain requires the precise integration of numerous temporally and spatially regulated stimuli. Many of these signals transduce their cues via the reversible phosphorylation of downstream effector molecules. Neuronal stimuli acting in concert have the potential of generating enormous arrays of regulatory phosphoproteins. Toward the global profiling of phosphoproteins in the developing brain, we report here the use of a mass spectrometry-based methodology permitting the first proteomic-scale phosphorylation site analysis of primary animal tissue, identifying over 500 protein phosphorylation sites in the developing mouse brain.

    Funded by: NHGRI NIH HHS: HG00041

    Molecular & cellular proteomics : MCP 2004;3;11;1093-101

  • The C terminus of fragile X mental retardation protein interacts with the multi-domain Ran-binding protein in the microtubule-organising centre.

    Menon RP, Gibson TJ and Pastore A

    National Institute for Medical Research, London NW7 1AA, UK. rmenon@nimr.mrc.ac.uk

    Absence of the fragile X mental retardation protein (FMRP) causes fragile X syndrome, the most common form of hereditary mental retardation. FMRP is a mainly cytoplasmic protein thought to be involved in repression of translation, through a complex network of protein-protein and protein-RNA interactions. Most of the currently known protein partners of FMRP recognise the conserved N terminus of the protein. No interaction has yet been mapped to the highly charged, poorly conserved C terminus, so far thought to be involved in RNA recognition through an RGG motif. In the present study, we show that a two-hybrid bait containing residues 419-632 of human FMRP fishes out a protein that spans the sequence of the Ran-binding protein in the microtubule-organising centre (RanBPM/RanBP9). Specific interaction of RanBPM with FMRP was confirmed by in vivo and in vitro assays. In brain tissue sections, RanBPM is highly expressed in the neurons of cerebral cortex and the cerebellar purkinje cells, in a pattern similar to that described for FMRP. Sequence analysis shows that RanBPM is a multi-domain protein. The interaction with FMRP was mapped in a newly identified CRA motif present in the RanBPM C terminus. Our results suggest that the functional role of RanBPM binding is modulation of the RNA-binding properties of FMRP.

    Journal of molecular biology 2004;343;1;43-53

  • RASSF1A interacts with microtubule-associated proteins and modulates microtubule dynamics.

    Dallol A, Agathanggelou A, Fenton SL, Ahmed-Choudhury J, Hesson L, Vos MD, Clark GJ, Downward J, Maher ER and Latif F

    Section of Medical and Molecular Genetics, Division of Reproductive and Child Health, University of Birmingham, The Medical School, Edgbaston, Birmingham, United Kingdom.

    The candidate tumor suppressor gene RASSF1A is inactivated in many types of adult and childhood cancers. However, the mechanisms by which RASSF1A exerts its tumor suppressive functions have yet to be elucidated. To this end, we performed a yeast two-hybrid screen to identify novel RASSF1A-interacting proteins in a human brain cDNA library. Seventy percent of interacting clones had homology to microtubule-associated proteins, including MAP1B and VCY2IP1/C19ORF5. RASSF1A association with MAP1B and VCY2IP1/C19ORF5 was subsequently confirmed in mammalian cell lines. This suggested that RASSF1A may exert its tumor-suppressive functions through interaction with the microtubules. We demonstrate that RASSF1A associates with the microtubules, causing them to exist as hyperstabilized circular bundles. We found that two naturally occurring tumor-associated missense substitutions in the RASSF1A coding region, C65R and R257Q, perturb the association of RASSF1A with the microtubules. The C65R and R257Q in addition to VCY2IP1/C19ORF5 showed reduced ability to induce microtubule acetylation and were unable to protect the microtubules against the depolymerizing action of nocodazole. In addition, wild-type RASSF1A but not the C65R or the R257Q is able to block DNA synthesis. Our data identify a role for RASSF1A in the regulation of microtubules and cell cycle dynamics that could be part of the mechanism(s) by which RASSF1A exerts its growth inhibition on cancer cells.

    Cancer research 2004;64;12;4112-6

  • Computational and experimental studies on human misshapen/NIK-related kinase MINK-1.

    Qu K, Lu Y, Lin N, Singh R, Xu X, Payan DG and Xu D

    Rigel, Inc., 1180 Veterans Boulevard, South San Francisco, CA 94080, USA. kqu@rigel.com

    We have studied the structure and function of Human Misshapen/NIK-related kinase (MINK-1) through a combination of computational methods and experimental approaches, including (1) fold recognition and sequence-structure alignment for each structural domain using the threading program PROSPECT, (2) gene expression and protein-protein interaction analysis of yeast homologs of human MINK-1 domains, and (3) yeast two-hybrid screening for proteins that interact with human MINK-1. Our structure prediction dissects MINK-1 into four domains: a conserved N-terminal kinase domain, followed by a coiled-coil region and a proline-rich region, and a C-terminal GCK domain. Gene expression and yeast two-hybrid analysis of yeast homologs of the MINK-1 domains suggest that MINK-1 may be involved in cell-cycle progression and cytoskeletal control. Consistent with these predicted functions, our in-house yeast two-hybrid screen for proteins that interact with human MINK-1 provides strong evidence that the coiled-coil and proline-rich domains of MINK-1 participate in the regulation of cytoskeletal organization, cell-cycle control and apoptosis. A homology model of the MINK-1 kinase domain was used to screen the NCI open compound database in DOCK, and chemical compounds with pharmaceutically acceptable properties were identified. Further medicinal chemistry compound structure optimization and kinase assays are underway.

    Current medicinal chemistry 2004;11;5;569-82

  • Proteomic identification of brain proteins that interact with dynein light chain LC8.

    Navarro-Lérida I, Martínez Moreno M, Roncal F, Gavilanes F, Albar JP and Rodríguez-Crespo I

    Departamento de Bioquímicay Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Madrid, Spain. nacho@bbml.ucm.es

    Cytoplasmic dynein is a large minus end-directed microtubule motor that translocates cargos towards the minus end of microtubules. Light chain 8 of the dynein machinery (LC8) has been reported to interact with a large variety of proteins that possess K/RSTQT or GIQVD motifs in their sequence, hence permitting their transport in a retrograde manner. Yeast two-hybrid analysis has revealed that in brain, LC8 associates directly with several proteins such as neuronal nitric oxide synthase, guanylate kinase domain-associated protein and gephyrin. In this work, we report the identification of over 40 polypeptides, by means of a proteomic approach, that interact with LC8 either directly or indirectly. Many of the neuronal proteins that we identified cluster at the post-synaptic terminal, and some of them such as phosphofructokinase, lactate dehydrogenase or aldolase are directly involved in glutamate metabolism. Other pool of proteins identified displayed the LC8 consensus binding motif. Finally, recombinant LC8 was produced and a library of overlapping dodecapeptides (pepscan) was employed to map the LC8 binding site of some of the proteins that were previously identified using the proteomic approach, hence confirming binding to the consensus binding sites.

    Proteomics 2004;4;2;339-46

  • Complete sequencing and characterization of 21,243 full-length human cDNAs.

    Ota T, Suzuki Y, Nishikawa T, Otsuki T, Sugiyama T, Irie R, Wakamatsu A, Hayashi K, Sato H, Nagai K, Kimura K, Makita H, Sekine M, Obayashi M, Nishi T, Shibahara T, Tanaka T, Ishii S, Yamamoto J, Saito K, Kawai Y, Isono Y, Nakamura Y, Nagahari K, Murakami K, Yasuda T, Iwayanagi T, Wagatsuma M, Shiratori A, Sudo H, Hosoiri T, Kaku Y, Kodaira H, Kondo H, Sugawara M, Takahashi M, Kanda K, Yokoi T, Furuya T, Kikkawa E, Omura Y, Abe K, Kamihara K, Katsuta N, Sato K, Tanikawa M, Yamazaki M, Ninomiya K, Ishibashi T, Yamashita H, Murakawa K, Fujimori K, Tanai H, Kimata M, Watanabe M, Hiraoka S, Chiba Y, Ishida S, Ono Y, Takiguchi S, Watanabe S, Yosida M, Hotuta T, Kusano J, Kanehori K, Takahashi-Fujii A, Hara H, Tanase TO, Nomura Y, Togiya S, Komai F, Hara R, Takeuchi K, Arita M, Imose N, Musashino K, Yuuki H, Oshima A, Sasaki N, Aotsuka S, Yoshikawa Y, Matsunawa H, Ichihara T, Shiohata N, Sano S, Moriya S, Momiyama H, Satoh N, Takami S, Terashima Y, Suzuki O, Nakagawa S, Senoh A, Mizoguchi H, Goto Y, Shimizu F, Wakebe H, Hishigaki H, Watanabe T, Sugiyama A, Takemoto M, Kawakami B, Yamazaki M, Watanabe K, Kumagai A, Itakura S, Fukuzumi Y, Fujimori Y, Komiyama M, Tashiro H, Tanigami A, Fujiwara T, Ono T, Yamada K, Fujii Y, Ozaki K, Hirao M, Ohmori Y, Kawabata A, Hikiji T, Kobatake N, Inagaki H, Ikema Y, Okamoto S, Okitani R, Kawakami T, Noguchi S, Itoh T, Shigeta K, Senba T, Matsumura K, Nakajima Y, Mizuno T, Morinaga M, Sasaki M, Togashi T, Oyama M, Hata H, Watanabe M, Komatsu T, Mizushima-Sugano J, Satoh T, Shirai Y, Takahashi Y, Nakagawa K, Okumura K, Nagase T, Nomura N, Kikuchi H, Masuho Y, Yamashita R, Nakai K, Yada T, Nakamura Y, Ohara O, Isogai T and Sugano S

    Helix Research Institute, 1532-3 Yana, Kisarazu, Chiba 292-0812, Japan.

    As a base for human transcriptome and functional genomics, we created the "full-length long Japan" (FLJ) collection of sequenced human cDNAs. We determined the entire sequence of 21,243 selected clones and found that 14,490 cDNAs (10,897 clusters) were unique to the FLJ collection. About half of them (5,416) seemed to be protein-coding. Of those, 1,999 clusters had not been predicted by computational methods. The distribution of GC content of nonpredicted cDNAs had a peak at approximately 58% compared with a peak at approximately 42%for predicted cDNAs. Thus, there seems to be a slight bias against GC-rich transcripts in current gene prediction procedures. The rest of the cDNAs unique to the FLJ collection (5,481) contained no obvious open reading frames (ORFs) and thus are candidate noncoding RNAs. About one-fourth of them (1,378) showed a clear pattern of splicing. The distribution of GC content of noncoding cDNAs was narrow and had a peak at approximately 42%, relatively low compared with that of protein-coding cDNAs.

    Nature genetics 2004;36;1;40-5

  • Mapmodulin/leucine-rich acidic nuclear protein binds the light chain of microtubule-associated protein 1B and modulates neuritogenesis.

    Opal P, Garcia JJ, Propst F, Matilla A, Orr HT and Zoghbi HY

    Department of Neurology, Baylor College of Medicine, Houston, Texas 77030, USA. p-opal@northwestern.edu

    We had previously described the leucine-rich acidic nuclear protein (LANP) as a candidate mediator of toxicity in the polyglutamine disease, spinocerebellar ataxia type 1 (SCA1). This was based on the observation that LANP binds ataxin-1, the protein involved in this disease, in a glutamine repeat-dependent manner. Furthermore, LANP is expressed abundantly in purkinje cells, the primary site of ataxin-1 pathology. Here we focused our efforts on understanding the neuronal properties of LANP. In undifferentiated neuronal cells LANP is predominantly a nuclear protein, requiring a bona fide nuclear localization signal to be imported into the nucleus. LANP translocates from the nucleus to the cytoplasm during the process of neuritogenesis, interacts with the light chain of the microtubule-associated protein 1B (MAP1B), and modulates the effects of MAP1B on neurite extension. LANP thus could play a key role in neuronal development and/or neurodegeneration by its interactions with microtubule associated proteins.

    Funded by: NINDS NIH HHS: K08 NS02246-03, R01 NS27699-13

    The Journal of biological chemistry 2003;278;36;34691-9

  • JNK1 is required for maintenance of neuronal microtubules and controls phosphorylation of microtubule-associated proteins.

    Chang L, Jones Y, Ellisman MH, Goldstein LS and Karin M

    Laboratory of Gene Regulation and Signal Transduction, University of California, San Diego, School of Medicine, La Jolla, CA 92037, USA.

    Microtubules (MTs) play an important role in elaboration and maintenance of axonal and dendritic processes. MT dynamics are modulated by MT-associated proteins (MAPs), whose activities are regulated by protein phosphorylation. We found that a member of the c-Jun NH(2)-terminal protein kinase (JNK) subgroup of MAP kinases, JNK1, is involved in regulation of MT dynamics in neuronal cells. Jnk1(-/-) mice exhibit disrupted anterior commissure tract formation and a progressive loss of MTs within axons and dendrites. MAP2 and MAP1B polypeptides are hypophosphorylated in Jnk1(-/-) brains, resulting in compromised ability to bind MTs and promote their assembly. These results suggest that JNK1 is required for maintaining the cytoskeletal integrity of neuronal cells and is a critical regulator of MAP activity and MT assembly.

    Funded by: NINDS NIH HHS: 5F32NS10727-02

    Developmental cell 2003;4;4;521-33

  • Hmob3 brain-specific sequence is a part of phylogenetically conserved human MAP1B gene 3'-untranslated region.

    Dergunova LV, Raevskaya NM, Vladychenskaya IP and Limborska SA

    Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia. dergunov@img.ras.ru

    Using in vitro and in silico approaches, we demonstrate that the Hmob3 brain-specific sequence is a part of the extended human MAP1B gene 3'UTR encoded by the portion of the exon 7. Previously we had isolated the 1.4 kb Hmob3 clone (Acc. No Y09836) from the human medulla oblongata cDNA library. In the present paper, we report the RT-PCR detection of extended transcripts containing the Hmob3 sequence as well as a fragment of MAP1B mRNA in the human brain mRNA samples. The existence of such transcripts confirms that Hmob3 is transcribed from the MAP1B gene. Thus we report a previously unknown region of the human MAP1B gene which encodes the MAP1B mRNA 3'UTR. The length of the 3'UTR was estimated of 4330 nucleotides. Comparative sequence analysis shows high phylogenetic conservation of MAP1B 3'UTR in mammals. Using Hmob3 as a probe in the Northern blot analysis, we have revealed two different types of transcripts for brain and kidney mRNA samples; in the skeletal muscle sample we detected both transcripts.

    Biomolecular engineering 2003;20;3;91-6

  • Microtubule-associated parameters as predictive markers of docetaxel activity in advanced breast cancer patients: results of a pilot study.

    Bernard-Marty C, Treilleux I, Dumontet C, Cardoso F, Fellous A, Gancberg D, Bissery MC, Paesmans M, Larsimont D, Piccart MJ and Di Leo A

    Translational Research Unit, Jules Bordet Institute, Brussels, Belgium.

    Docetaxel is currently one of the most active agents for breast cancer. Predictive markers of docetaxel efficacy are clearly needed in order to avoid unnecessary toxicity in nonresponding or resistant patients and to improve the cost-effectiveness ratio of docetaxel. This pilot study correlates the clinical efficacy of docetaxel in 54 metastatic or locally advanced breast cancer patients with the expression of microtubule-associated parameters evaluated by immunohistochemistry in archival tumor samples. Among the 41 eligible patients (evaluable response to docetaxel and available predocetaxel treatment paraffin-embedded tumor tissue), response to docetaxel was: partial response 54%, stable disease 29%, and progressive disease 17%. Alfa- and b-tubulin and Tau protein were expressed in the majority of tumor samples. Class II, III, and IV b-tubulin isotypes were expressed in 56%, 65%, and 82% of samples, respectively. No clear association was found between response to docetaxel and the level of expression of Tau protein, a- and b-tubulin, and class III and IV b-tubulin isotypes. In patients with class II b-tubulin-positive tumors, the response rate was 39%, while in class II b-tubulin-negative tumors the response rate was 79% (P = 0.04). Therefore, we conclude that the class II b-tubulin isotype seems to be a promising predictive marker of docetaxel activity. Nevertheless, further investigations are needed due to the limited number of patients evaluated in this pilot study.

    Clinical breast cancer 2002;3;5;341-5

  • Microtubule-associated protein 1B: a neuronal binding partner for gigaxonin.

    Ding J, Liu JJ, Kowal AS, Nardine T, Bhattacharya P, Lee A and Yang Y

    Department of Neurology, Stanford University School of Medicine, CA 94305, USA.

    Giant axonal neuropathy (GAN), an autosomal recessive disorder caused by mutations in GAN, is characterized cytopathologically by cytoskeletal abnormality. Based on its sequence, gigaxonin contains an NH2-terminal BTB domain followed by six kelch repeats, which are believed to be important for protein-protein interactions (Adams, J., R. Kelso, and L. Cooley. 2000. Trends Cell Biol. 10:17-24.). Here, we report the identification of a neuronal binding partner of gigaxonin. Results obtained from yeast two-hybrid screening, cotransfections, and coimmunoprecipitations demonstrate that gigaxonin binds directly to microtubule-associated protein (MAP)1B light chain (LC; MAP1B-LC), a protein involved in maintaining the integrity of cytoskeletal structures and promoting neuronal stability. Studies using double immunofluorescent microscopy and ultrastructural analysis revealed physiological colocalization of gigaxonin with MAP1B in neurons. Furthermore, in transfected cells the specific interaction of gigaxonin with MAP1B is shown to enhance the microtubule stability required for axonal transport over long distance. At least two different mutations identified in GAN patients (Bomont, P., L. Cavalier, F. Blondeau, C. Ben Hamida, S. Belal, M. Tazir, E. Demir, H. Topaloglu, R. Korinthenberg, B. Tuysuz, et al. 2000. Nat. Genet. 26:370-374.) lead to loss of gigaxonin-MAP1B-LC interaction. The devastating axonal degeneration and neuronal death found in GAN patients point to the importance of gigaxonin for neuronal survival. Our findings may provide important insights into the pathogenesis of neurodegenerative disorders related to cytoskeletal abnormalities.

    The Journal of cell biology 2002;158;3;427-33

  • Microtubule-associated protein 1B: a neuronal binding partner for myelin-associated glycoprotein.

    Franzen R, Tanner SL, Dashiell SM, Rottkamp CA, Hammer JA and Quarles RH

    Laboratory of Molecular and Cellular Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-4440, USA.

    Myelin-associated glycoprotein (MAG) is expressed in periaxonal membranes of myelinating glia where it is believed to function in glia-axon interactions by binding to a component of the axolemma. Experiments involving Western blot overlay and coimmunoprecipitation demonstrated that MAG binds to a phosphorylated neuronal isoform of microtubule-associated protein 1B (MAP1B) expressed in dorsal root ganglion neurons (DRGNs) and axolemma-enriched fractions from myelinated axons of brain, but not to the isoform of MAP1B expressed by glial cells. The expression of some MAP1B as a neuronal plasma membrane glycoprotein (Tanner, S.L., R. Franzen, H. Jaffe, and R.H. Quarles. 2000. J. Neurochem. 75:553-562.), further documented here by its immunostaining without cell permeabilization, is consistent with it being a binding partner for MAG on the axonal surface. Binding sites for a MAG-Fc chimera on DRGNs colocalized with MAP1B on neuronal varicosities, and MAG and MAP1B also colocalized in the periaxonal region of myelinated axons. In addition, expression of the phosphorylated isoform of MAP1B was increased significantly when DRGNs were cocultured with MAG-transfected COS cells. The interaction of MAG with MAP1B is relevant to the known role of MAG in affecting the cytoskeletal structure and stability of myelinated axons.

    The Journal of cell biology 2001;155;6;893-8

  • GABAC receptor sensitivity is modulated by interaction with MAP1B.

    Billups D, Hanley JG, Orme M, Attwell D and Moss SJ

    Laboratory for Molecular Cell Biology, Department of Pharmacology, University College London, London, WC1E 6BT, United Kingdom.

    GABA(C) receptors contain rho subunits and mediate feedback inhibition from retinal amacrine cells to bipolar cells. We previously identified the cytoskeletal protein MAP1B as a rho1 subunit anchoring protein. Here, we analyze the structural basis and functional significance of the MAP1B-rho1 interaction. Twelve amino acids at the C terminus of the large intracellular loop of rho1 (and also rho2) are sufficient for interaction with MAP1B. Disruption of the MAP1B-rho interaction in bipolar cells in retinal slices decreased the EC(50) of their GABA(C) receptors, doubling the receptors' current at low GABA concentrations without affecting their maximum current at high concentrations. Thus, anchoring to the cytoskeleton lowers the sensitivity of GABA(C) receptors and provides a likely site for functional modulation of GABA(C) receptor-mediated inhibition.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2000;20;23;8643-50

  • Regulation of microtubule-associated protein 1B (MAP1B) subunit composition.

    Mei X, Sweatt AJ and Hammarback JA

    Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.

    The MAP1B and MAP1A genes each produce an mRNA that encodes a polyprotein. When cleaved, each polyprotein yields a single heavy chain and a single light chain, which become noncovalently associated. In previous work, it was found that the MAP1B light chains and heavy chains exist in a 2:1 ratio. Through use of quantitative immunoblot techniques, this finding was further examined in the developing rat brain. MAP1B heavy chain (HC) and light chain (LC1), as well as the light chain of MAP1A (LC2), were prepared in purified form for use as standards and/or immunogens for generation of antibodies for immunoblotting. Brain homogenates and microtubule-enriched fractions from developing rats were assayed for MAP1B HC and LC1 content. Results indicated that postnatal rat brain homogenates contain LC1 in a 6:1 to 8:1 molar ratio to the MAP1B HC. Purified microtubules also contain LC1 in excess of MAP1B HC, but at a ratio of 2:1. We propose that most of the excess LC1 in homogenates is either insoluble or not bound to microtubules. The findings raise the possibility of a function for the "excess" LC1 that does not require association with MAP1 HC and/or microtubules. Given a synthetic mechanism that produces MAP1B HC and LC1 in a 1:1 ratio at both transcription and translation steps, we propose that the "excess" LC1 in brain homogenates is a consequence of LC1 having a greater half-life than the MAP1B HC. Consistently with this hypothesis, a major pool of MAP1B HC is rapidly degraded after blocking protein synthesis with cycloheximide, whereas LC1 levels remain constant even after 24 hr of cycloheximide treatment.

    Journal of neuroscience research 2000;62;1;56-64

  • Evidence for expression of some microtubule-associated protein 1B in neurons as a plasma membrane glycoprotein.

    Tanner SL, Franzen R, Jaffe H and Quarles RH

    Myelin and Brain Development Section, Laboratory of Molecular and Cellular Neurobiology, National Institutes of Health, Bethesda, Maryland, USA.

    Microtubule-associated protein (MAP) 1B is a high-molecular-weight cytoskeletal protein that is abundant in developing neuronal processes and appears to be necessary for axonal growth. Various biochemical and immunocytochemical results are reported, indicating that a significant fraction of MAP1B is expressed as an integral membrane glycoprotein in vesicles and the plasma membrane of neurons. MAP1B is present in microsomal fractions isolated from developing rat brain and fractionates across a sucrose gradient in a manner similar to synaptophysin, a well-known vesicular and plasma membrane protein. MAP1B is also in axolemma-enriched fractions (AEFs) isolated from myelinated axons of rat brain. MAP1B in AEFs and membrane fractions from cultured dorsal root ganglion neurons (DRGNs) remains membrane-associated following high-salt washes and contains sialic acid. Furthermore, MAP1B in intact DRGNs is readily degraded by extracellular trypsin and is labeled by the cell surface probe sulfosuccinimidobiotin. Immunocytochemical examination of DRGNs shows that MAP1B is concentrated in vesicle-rich varicosities along the length of axons. Myelinated peripheral nerves immunostained for MAP1B show an enrichment at the axonal plasma membrane. These observations demonstrate that some of the MAP1B in developing neurons is an integral plasma membrane glycoprotein.

    Journal of neurochemistry 2000;75;2;553-62

  • Microtubule-associated protein 1B is a component of cortical Lewy bodies and binds alpha-synuclein filaments.

    Jensen PH, Islam K, Kenney J, Nielsen MS, Power J and Gai WP

    Department of Medical Biochemistry, University of Aarhus, DK-8000 Aarhus C, Denmark, Arpida AG, Munchenstein 4142, Switzerland. phj@biokemi.au.dk

    Lewy bodies, neuropathological hallmarks of Parkinson's disease and dementia with Lewy bodies, comprise alpha-synuclein filaments and other less defined proteins. Characterization of Lewy body proteins that interact with alpha-synuclein may provide insight into the mechanism of Lewy body formation. Double immunofluorescence labeling and confocal microscopy revealed approximately 80% of cortical Lewy bodies contained microtubule-associated protein 1B (MAP-1B) that overlapped with alpha-synuclein. Lewy bodies were isolated using an immunomagnetic technique from brain tissue of patients dying with dementia with Lewy bodies. Lewy body proteins were resolved by polyacrylamide gel electrophoresis. Immunoblotting confirmed the presence of MAP-1B and alpha-synuclein in purified Lewy bodies. Direct binding studies revealed a high affinity interaction (IC(50) approximately 20 nm) between MAP-1B and alpha-synuclein. The MAP-1B-binding sites were mapped to the last 45 amino acids of the alpha-synuclein C terminus. MAP-1B also bound in vitro assembled alpha-synuclein fibrils. Thus, MAP-1B may be involved in the pathogenesis of Lewy bodies via its interaction with monomeric and fibrillar alpha-synuclein.

    The Journal of biological chemistry 2000;275;28;21500-7

  • The protein MAP-1B links GABA(C) receptors to the cytoskeleton at retinal synapses.

    Hanley JG, Koulen P, Bedford F, Gordon-Weeks PR and Moss SJ

    Department of Pharmacology, University College, London, UK.

    The ionotropic type-A and type-C receptors for the neurotransmitter gamma-aminobutyric acid (GABA(A) and GABA(C) receptors) are the principal sites of fast synaptic inhibition in the central nervous system, but it is not known how these receptors are localized at GABA-dependent synapses. GABA(C) receptors, which are composed of rho-subunits, are expressed almost exclusively in the retina of adult vertebrates, where they are enriched on bipolar cell axon terminals. Here we show that the microtubule-associated protein 1B (MAP-1B) specifically interacts with the GABA(C) rho1 subunit but not with GABA(A) receptor subunits. Furthermore, GABA(C) receptors and MAP-1B co-localize at postsynaptic sites on bipolar cell axon terminals. Co-expression of MAP-1B and the rho1 subunit in COS cells results in a dramatic redistribution of the rho1 subunit. Our observations suggest a novel mechanism for localizing ionotropic GABA receptors to synaptic sites. This mechanism, which is specific for GABA(C) but not GABA(A) receptors, may allow these receptor subtypes, which have distinct physiological and pharmacological properties, to be differentially localized at inhibitory synapses.

    Funded by: Wellcome Trust

    Nature 1999;397;6714;66-9

  • Novel features of the light chain of microtubule-associated protein MAP1B: microtubule stabilization, self interaction, actin filament binding, and regulation by the heavy chain.

    Tögel M, Wiche G and Propst F

    Institute of Biochemistry and Molecular Cell Biology, Vienna Biocenter, University of Vienna, A-1030 Vienna, Austria.

    Previous studies on the role of microtubule-associated protein 1B (MAP1B) in adapting microtubules for nerve cell-specific functions have examined the activity of the entire MAP1B protein complex consisting of heavy and light chains and revealed moderate effects on microtubule stability. Here we have analyzed the effects of the MAP1B light chain in the absence or presence of the heavy chain by immunofluorescence microscopy of transiently transfected cells. Distinct from all other MAPs, the MAP1B light chain-induced formation of stable but apparently flexible microtubules resistant to the effects of nocodazole and taxol. Light chain activity was inhibited by the heavy chain. In addition, the light chain was found to harbor an actin filament binding domain in its COOH terminus. By coimmunoprecipitation experiments using epitope-tagged fragments of MAP1B we showed that light chains can dimerize or oligomerize. Furthermore, we localized the domains for heavy chain-light chain interaction to regions containing sequences homologous to MAP1A. Our findings assign several crucial activities to the MAP1B light chain and suggest a new model for the mechanism of action of MAP1B in which the heavy chain might act as the regulatory subunit of the MAP1B complex to control light chain activity.

    The Journal of cell biology 1998;143;3;695-707

  • Inhibition of GSK-3beta leading to the loss of phosphorylated MAP-1B is an early event in axonal remodelling induced by WNT-7a or lithium.

    Lucas FR, Goold RG, Gordon-Weeks PR and Salinas PC

    Developmental Biology Research Centre, The Randall Institute, King's College London, 26-29 Drury Lane, London WC2B 5RL, UK.

    WNT-7a induces axonal spreading and branching in developing cerebellar granule neurons. This effect is mediated through the inhibition of GSK-3beta, a serine/threonine kinase and a component of the WNT pathway. Lithium, an inhibitor of GSK-3beta, mimics WNT-7a in granule cells. Here we examined further the effect of GSK-3beta inhibition on cytoskeletal re-organisation. Lithium induces axonal spreading and increases growth cone area and perimeter. This effect is associated with the absence or reduction of stable microtubules in spread areas. Lithium induces the loss of a phosphorylated form of MAP-1B, a microtubule associated protein involved in axonal outgrowth. Down-regulation of the phosphorylated MAP-1B, MAP-1B-P, from axonal processes occurs before axonal remodelling is evident. In vitro phosphorylation assays show that MAP-1B-P is generated by direct phosphorylation of MAP-1B by GSK-3beta. WNT-7a, like lithium, also leads to loss of MAP-1B-P from spread axons and growth cones. Our data suggest that WNT-7a and lithium induce changes in microtubule dynamics by inhibiting GSK-3beta which in turn lead to changes in the phosphorylation of MAP-1B. These findings suggest a novel role for GSK-3beta and WNTs in axonal remodelling and identify MAP-1B as a new target for GSK-3beta and WNT.

    Funded by: Wellcome Trust

    Journal of cell science 1998;111 ( Pt 10);1351-61

  • Decreased expression of microtubule-associated protein 5 (MAP5) in the molecular layer of cerebellum in preterm infants with olivocerebellar lesions.

    Ohyu J and Takashima S

    Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, NCNP, Kodaira, Tokyo, Japan. ohyu@ncnaxp.ncnp.go.jp

    The changes in microtubule-associated protein 5 (MAP5) expression in the cerebellum with olivocerebellar degeneration (OCD) were investigated by means of immunohistochemical method, compared with gestational age-matched controls. In controls of 24-33 postmenstrual weeks, the molecular layer was diffusely immunoreactive. However, in cases of olivocerebellar degeneration (25-35 postmenstrual weeks), MAP5 immunoreactivity was reduced in the inner half of the molecular layer, especially in a portion where Purkinje cells were absent. The ratio of the density in the outer half of the molecular layer to that in the inner half was also determined with an image analyzer, and increased significantly in Purkinje cell-negative areas. Because MAP5 was believed to be expressed mainly on growing axons in the early fetal period, the reduction of MAP5 immunoreactivity in OCD cases suggested that normal interaction of Purkinje cells and climbing fibers is vulnerable to ischemia and hypoxia in developing stage and that retrograde transynaptic degeneration of the inferior olivary nuclei is secondarily induced.

    Brain & development 1998;20;1;22-6

  • Cloning of human microtubule-associated protein 1B and the identification of a related gene on chromosome 15.

    Lien LL, Feener CA, Fischbach N and Kunkel LM

    Department of Genetics, Harvard Medical School, Boston, Massachusetts.

    We report here the complete cloning and sequencing of human microtubule associated protein 1B (MAP1B). Comparisons to mouse and partial rat MAP1B sequence indicate that this gene is extremely well conserved, with 91 and 90% identity, respectively. The entire human MAP1B genomic region has been isolated and the genomic organization determined. The gene includes seven exons, and the third exon contains sequence not represented in mouse or rat MAP1B. This sequence, labeled 3A, is present at the 5' end of an alternative transcript that is expressed at approximately 1/10th the level of the full-length transcript. By comparisons of human MAP1B with the sequence databases, we have identified a MAP1B-related gene that is probably the human homologue of rat MAP1A. This gene is expressed at high levels in brain and spinal cord and much lower levels in muscle and maps to the long arm of human chromosome 15.

    Funded by: NICHD NIH HHS: HD 18658; NINDS NIH HHS: R01 NS23740

    Genomics 1994;22;2;273-80

  • Role of phosphorylated MAPlB in neuritogenesis.

    Avila J, Ulloa L, Diez-Guerra J and Diaz-Nido J

    Centro de Biologia Molecular Severo Ochoa (CSIC-UAM), Universidad Autonoma de Madrid, Spain.

    The distribution of microtubule-associated protein lB (MAPlB) phosphorylated by either proline-directed protein kinase (PDPK) or casein kinase II (CK II) in neuroblastoma cells and hippocampal neurons has been studied by immunofluorescence using specific antibodies to distinct phosphorylation-sensitive epitopes. A proximo-distal gradient of increasing PDPK-catalyzed phosphorylation of MAPlB is superimposed on a proximo distal gradient of decreasing CK II-catalyzed MAPlB phosphorylation within growing axon-like neurites. Additionally, CK II-phosphorylated MAPlB is present in cell bodies and dendrites where no PDPK-phosphorylated MAPlB is observed. These results suggest distinct roles for both types of modifications of MAPlB in developing neurons.

    Cell biology international 1994;18;5;309-14

  • Mapping of human microtubule-associated protein 1B in proximity to the spinal muscular atrophy locus at 5q13.

    Lien LL, Boyce FM, Kleyn P, Brzustowicz LM, Menninger J, Ward DC, Gilliam TC and Kunkel LM

    Department of Genetics, Harvard Medical School, Boston, MA 02115.

    A polyclonal antiserum directed against the C-terminal domain of dystrophin was used to isolate a cDNA clone encoding an antigenically cross-reactive protein, microtubule-associated protein 1B (MAP-1B). Physical mapping of the human MAP-1B locus places its chromosomal location at 5q13, in proximity to the spinal muscular atrophy (SMA) locus. SMA is a degenerative disorder primarily affecting motor neurons. Genetic linkage analysis of SMA families using a human dinucleotide repeat polymorphism just 3' of the MAP-1B gene has shown tight linkage to SMA mutations. These mapping data together with the postulated role of MAP-1B in neuronal morphogenesis and its localization in anterior horn motor neurons suggest a possible association with SMA.

    Funded by: NHGRI NIH HHS: R01 HG00272; NINDS NIH HHS: R01 NS23740, R01 NS528877

    Proceedings of the National Academy of Sciences of the United States of America 1991;88;17;7873-6

  • MAP1B is encoded as a polyprotein that is processed to form a complex N-terminal microtubule-binding domain.

    Hammarback JA, Obar RA, Hughes SM and Vallee RB

    Cell Biology Group, Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts 01545.

    Microtubule-associated protein 1B (MAP1B), an abundant developmentally regulated neuronal protein, is a stoichiometric complex of a heavy chain and two light chains (light chain 1 and light chain 3). We find that light chain 1 is encoded within the 3' end of a previously reported MAP1B heavy chain cDNA. Amino acid sequencing, epitope mapping, Northern blotting, and Southern blotting indicate that the light chain and heavy chain are encoded by the same mRNA within the same open reading frame. In addition, amino acid sequencing of a 120 kd microtubule-binding and light chain-binding fragment of the heavy chain reveals that light chain 1 binds near the heavy chain N-terminus. Together these data indicate that the heavy chain and light chain 1 are produced by proteolytic processing of a MAP1B polyprotein and form a complex microtubule-binding domain.

    Funded by: NIGMS NIH HHS: GM10943, GM26701

    Neuron 1991;7;1;129-39

  • MAP 1A and MAP 1B are structurally related microtubule associated proteins with distinct developmental patterns in the CNS.

    Schoenfeld TA, McKerracher L, Obar R and Vallee RB

    Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts 01545.

    Five high-molecular-weight microtubule-associated proteins (MAPs) were identified in brain tissue in previous work from this laboratory (Bloom et al., 1984). These proteins were termed MAP 1A, 1B, 1C, 2A, and 2B. The MAP 1's differed from the MAP 2's, and showed little evidence of interrelationship on the basis of immunological and biochemical comparison. We report here that MAP 1A and MAP 1B are, in fact, related at the level of subunit composition. Immunoprecipitation of the individual MAPs showed that both contained low-molecular-weight subunits of Mr 30,000 and Mr 19,000 (light chains 1 and 3). An additional subunit, light chain 2 (Mr 28,000), was primarily found in preparations of MAP 1A. The light chains co-sedimented with microtubules after chymotryptic digestion of the MAPs. This suggested an association of the light chains with the microtubule binding domains of the MAPs, which are identified here as distinct fragments of Mr 60,000 for MAP 1A and 120,000 for MAP 1B. A panel of monoclonal anti-MAP 1A and anti-MAP 1B antibodies, including one that reacts with a common phosphorylated epitope, was used to examine the distribution of these proteins in the developing rat brain and spinal cord. MAP 1B was found to be abundant in the newborn brain and to decrease with development, in contrast to MAP 1A which increased with development. By immunohistochemistry MAP 1B was found to be highly concentrated in developing axonal processes in the cerebellar molecular layer, the corticospinal tract, the mossy fibers in the hippocampus, and the olfactory nerve. Of particular interest, the mossy fiber and olfactory nerve staining persisted in the adult, indicating continued outgrowth of the mossy fibers as well as olfactory nerve axons. MAP 1A staining was, in contrast, weak or absent in developing axonal fibers but moderate in mature axons and intense in developing and mature dendritic processes. Our results indicate that MAP 1A and MAP 1B are structurally related components of the neuronal cytoskeleton with complementary patterns of expression.

    Funded by: NIGMS NIH HHS: GM26701

    The Journal of neuroscience : the official journal of the Society for Neuroscience 1989;9;5;1712-30

Gene lists (9)

Gene List Source Species Name Description Gene count
L00000009 G2C Homo sapiens Human PSD Human orthologues of mouse PSD adapted from Collins et al (2006) 1080
L00000011 G2C Homo sapiens Human clathrin Human orthologues of mouse clathrin coated vesicle genes adapted from Collins et al (2006) 150
L00000012 G2C Homo sapiens Human Synaptosome Human orthologues of mouse synaptosome adapted from Collins et al (2006) 152
L00000013 G2C Homo sapiens Human mGluR5 Human orthologues of mouse mGluR5 complex adapted from Collins et al (2006) 52
L00000016 G2C Homo sapiens Human PSP Human orthologues of mouse PSP adapted from Collins et al (2006) 1121
L00000059 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-CONSENSUS Human cortex PSD consensus 748
L00000061 G2C Homo sapiens BAYES-COLLINS-MOUSE-PSD-CONSENSUS Mouse cortex PSD consensus (ortho) 984
L00000069 G2C Homo sapiens BAYES-COLLINS-HUMAN-PSD-FULL Human cortex biopsy PSD full list 1461
L00000071 G2C Homo sapiens BAYES-COLLINS-MOUSE-PSD-FULL Mouse cortex PSD full list (ortho) 1556
© G2C 2014. The Genes to Cognition Programme received funding from The Wellcome Trust and the EU FP7 Framework Programmes:
EUROSPIN (FP7-HEALTH-241498), SynSys (FP7-HEALTH-242167) and GENCODYS (FP7-HEALTH-241995).

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