G2Cdb::Gene report

Gene id
Gene symbol
Homo sapiens
cofilin 1 (non-muscle)
G00001165 (Mus musculus)

Databases (7)

ENSG00000172757 (Ensembl human gene)
1072 (Entrez Gene)
998 (G2Cdb plasticity & disease)
CFL1 (GeneCards)
601442 (OMIM)
Marker Symbol
HGNC:1874 (HGNC)
Protein Sequence
P23528 (UniProt)

Literature (92)

Pubmed - other

  • Tyrosine phosphorylation of cofilin at Y68 by v-Src leads to its degradation through ubiquitin-proteasome pathway.

    Yoo Y, Ho HJ, Wang C and Guan JL

    Division of Molecular Medicine and Genetics, Departments of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA.

    Cofilin is a major regulator of actin dynamics involved in the regulation of cell spreading and migration through its actin depolymerizing and severing activities. v-Src is an activated Src tyrosine kinase and a potent oncogene known to phosphorylate a variety of cellular proteins in cell transformation process including altered cell adhesion, spreading and migration. Recently, it has been suggested that cofilin is a potential substrate of v-Src (Rush et al., 2005). Here, we show direct tyrosine phosphorylation of cofilin by v-Src and identify Y68 as the major phosphorylation site. Cofilin phosphorylation at Y68 did not change its activity per se, but induced increased ubiquitination of cofilin and its degradation through the proteosome pathway. Furthermore, the negative effect of cofilin on cellular F-actin contents was inhibited by coexpression of v-Src, whereas that of cofilin mutant Y68F (Y68 mutated to F) was not affected, suggesting that v-Src-mediated cofilin phosphorylation at Y68 is required for the degradation of cofilin in vivo. Lastly, inhibition of cell spreading by v-Src was rescued partially by coexpression of cofilin, and to a greater extent by the Y68F mutant, which is not subjected to v-Src-induced degradation through phosphorylation, suggesting that v-Src-mediated changes in cell spreading is, at least in part, through inhibiting the function of cofilin through phosphorylating it at Y68. Together, these results suggest a novel mechanism by which cofilin is regulated by v-Src through tyrosine phosphorylation at Y68 that triggers the degradation of cofilin through ubiquitination-proteosome pathway and consequently inhibits cofilin activity in reducing cellular F-actin contents and cell spreading.

    Funded by: NCI NIH HHS: R01 CA150926; NIGMS NIH HHS: GM48050, R01 GM048050, R01 GM048050-17

    Oncogene 2010;29;2;263-72

  • Oxidant-induced apoptosis is mediated by oxidation of the actin-regulatory protein cofilin.

    Klamt F, Zdanov S, Levine RL, Pariser A, Zhang Y, Zhang B, Yu LR, Veenstra TD and Shacter E

    Laboratory of Biochemistry, Division of Therapeutic Proteins, Center for Drug Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA.

    Physiological oxidants that are generated by activated phagocytes comprise the main source of oxidative stress during inflammation. Oxidants such as taurine chloramine (TnCl) and hydrogen peroxide (H(2)O(2)) can damage proteins and induce apoptosis, but the role of specific protein oxidation in this process has not been defined. We found that the actin-binding protein cofilin is a key target of oxidation. When oxidation of this single regulatory protein is prevented, oxidant-induced apoptosis is inhibited. Oxidation of cofilin causes it to lose its affinity for actin and to translocate to the mitochondria, where it induces swelling and cytochrome c release by mediating opening of the permeability transition pore (PTP). This occurs independently of Bax activation and requires both oxidation of cofilin Cys residues and dephosphorylation at Ser 3. Knockdown of endogenous cofilin using targeted siRNA inhibits oxidant-induced apoptosis, which is restored by re-expression of wild-type cofilin but not by cofilin containing Cys to Ala mutations. Exposure of cofilin to TnCl results in intramolecular disulphide bonding and oxidation of Met residues to Met sulphoxide, but only Cys oxidation causes cofilin to induce mitochondrial damage.

    Funded by: Intramural NIH HHS: Z01 HL000225-31; NCI NIH HHS: N01-CO-12400, N01CO12400

    Nature cell biology 2009;11;10;1241-6

  • Coronin 2A regulates a subset of focal-adhesion-turnover events through the cofilin pathway.

    Marshall TW, Aloor HL and Bear JE

    Lineberger Comprehensive Cancer Center and Department of Cell and Developmental Biology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA.

    Coronins are conserved F-actin-binding proteins that are important for motility and actin dynamics. Unlike type I coronins, coronin 2A localizes to stress fibers and some focal adhesions, and is excluded from the leading edge. Depletion of coronin 2A in MTLn3 cells decreases cell motility and turnover of focal adhesions. Surprisingly, none of the pathways known to regulate focal-adhesion turnover are affected by depletion of coronin 2A. Depletion of coronin 2A does, however, increase phospho-cofilin, suggesting that misregulation of cofilin might affect adhesion dynamics. Slingshot-1L, a cofilin-activating phosphatase, localizes to focal adhesions and interacts with coronin 2A. Depletion of coronin 2A reduces cofilin activity at focal adhesions, as measured by barbed-end density and actin FRAP. In both fixed cells and live cells, cofilin localizes to the proximal end of some focal adhesions. Although expression of wild-type cofilin in coronin-2A-depleted cells has no major effect on focal-adhesion dynamics, expression of an active mutant of cofilin bypasses the defects in cell motility and focal-adhesion disassembly. These results implicate both coronin 2A and cofilin as factors that can regulate a subset of focal-adhesion-turnover events.

    Funded by: NIGMS NIH HHS: GM083035

    Journal of cell science 2009;122;Pt 17;3061-9

  • HIV-1 Nef interferes with host cell motility by deregulation of Cofilin.

    Stolp B, Reichman-Fried M, Abraham L, Pan X, Giese SI, Hannemann S, Goulimari P, Raz E, Grosse R and Fackler OT

    Department of Virology, Im Neuenheimer Feld 324, University of Heidelberg, Heidelberg 69120, Germany.

    HIV-1 Nef is a key factor in AIDS pathogenesis. Here, we report that Nef potently inhibits motility of fibroblasts and chemotaxis of HIV-1-infected primary human T lymphocytes toward the chemokines SDF-1alpha, CCL-19, and CCL-21 ex vivo. Furthermore, Nef inhibits guided motility of zebrafish primordial germ cells toward endogenous SDF-1a in vivo. These migration defects result from Nef-mediated inhibition of the actin remodeling normally triggered by migratory stimuli. Nef strongly induces phosphorylation of cofilin, inactivating this evolutionarily conserved actin-depolymerizing factor that promotes cell motility when unphosphorylated. Nef-dependent cofilin deregulation requires association of Nef with the cellular kinase Pak2. Disruption of Nef-Pak2 association restores the cofilin phosphorylation levels and actin remodeling that facilitate cell motility. We conclude that HIV-1 Nef alters Pak2 function, which directly or indirectly inactivates cofilin, thereby restricting migration of infected T lymphocytes as part of a strategy to optimize immune evasion and HIV-1 replication.

    Cell host & microbe 2009;6;2;174-86

  • Regulated expression of cofilin and the consequent regulation of p27(kip1) are essential for G(1) phase progression.

    Tsai CH, Chiu SJ, Liu CC, Sheu TJ, Hsieh CH, Keng PC and Lee YJ

    Department of Biomedical Imaging and Radiological Sciences, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei, Taiwan.

    Cofilin, a ubiquitously expressed actin binding protein, is responsible for the formation of the actin cytoskeleton and is indispensable for cell cycle control. However, the association between cofilin expression and the cell cycle remains to be elucidated. In this study, we found that the expression level of cofilin upregulated in G(1) phase-arrested confluent cells, while knockdown of cofilin expression by small interference RNA (siRNA) in these cells led to a reduction in the population of G(1) cells. To investigate the role of cofilin in the control of G(1) phase progression, a tet-on gene expression system was introduced to overexpress different concentrations of cofilin in cells. The results showed that G(1) phase progression was blocked following induction of exogenous cofilin. A survey of the cell cycle proteins controlling the G(1) phase progression revealed that the cyclin-dependent kinase inhibitor (CKI) p27(kip1) was the primary molecule induced by overexpressed cofilin in a time and dose dependent manner. Upregulated p27(kip1) repressed phosphorylation of the retinoblastoma protein (Rb) mediated by cyclin D1/CDK4 activity. Conversely, siRNA against p27(kip1) expression in the cofilin overexpressing cells released the G(1) phase arrest. Furthermore, we found that overexpression of cofilin led to induction of p27(kip1) gene promoter transactivation using luciferase reporter gene assay. This effect was associated with increase of p27(kip1) mRNA transiently. In addition, inhibition of threonine-187 phosphorylation of p27(kip1) protein for ubiquitinyl-proteasomal mediated degradation was also involved in upregulation of p27(kip1). These data suggest that cofilin expression and its regulation of p27(kip1) expression is important for the control of G(1) phase progression.

    Cell cycle (Georgetown, Tex.) 2009;8;15;2365-74

  • Essential role of cofilin-1 in regulating thrombin-induced RelA/p65 nuclear translocation and intercellular adhesion molecule 1 (ICAM-1) expression in endothelial cells.

    Fazal F, Bijli KM, Minhajuddin M, Rein T, Finkelstein JN and Rahman A

    Department of Pediatrics (Neonatology), Lung Biology and Disease Program, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA. Fabeha_Fazal@urmc.rochester.edu

    Activation of RhoA/Rho-associated kinase (ROCK) pathway and the associated changes in actin cytoskeleton induced by thrombin are crucial for activation of NF-kappaB and expression of its target gene ICAM-1 in endothelial cells. However, the events acting downstream of RhoA/ROCK to mediate these responses remain unclear. Here, we show a central role of cofilin-1, an actin-binding protein that promotes actin depolymerization, in linking RhoA/ROCK pathway to dynamic alterations in actin cytoskeleton that are necessary for activation of NF-kappaB and thereby expression of ICAM-1 in these cells. Stimulation of human umbilical vein endothelial cells with thrombin resulted in Ser(3) phosphorylation/inactivation of cofilin and formation of actin stress fibers in a ROCK-dependent manner. RNA interference knockdown of cofilin-1 stabilized the actin filaments and inhibited thrombin- and RhoA-induced NF-kappaB activity. Similarly, constitutively inactive mutant of cofilin-1 (Cof1-S3D), known to stabilize the actin cytoskeleton, inhibited NF-kappaB activity by thrombin. Overexpression of wild type cofilin-1 or constitutively active cofilin-1 mutant (Cof1-S3A), known to destabilize the actin cytoskeleton, also impaired thrombin-induced NF-kappaB activity. Additionally, depletion of cofilin-1 was associated with a marked reduction in ICAM-1 expression induced by thrombin. The effect of cofilin-1 depletion on NF-kappaB activity and ICAM-1 expression occurred downstream of IkappaBalpha degradation and was a result of impaired RelA/p65 nuclear translocation and consequently, RelA/p65 binding to DNA. Together, these data show that cofilin-1 occupies a central position in RhoA-actin pathway mediating nuclear translocation of RelA/p65 and expression of ICAM-1 in endothelial cells.

    Funded by: NHLBI NIH HHS: HL67424, R01 HL067424; NIEHS NIH HHS: ES-01247, P30 ES001247

    The Journal of biological chemistry 2009;284;31;21047-56

  • Protein kinase D regulates cell migration by direct phosphorylation of the cofilin phosphatase slingshot 1 like.

    Peterburs P, Heering J, Link G, Pfizenmaier K, Olayioye MA and Hausser A

    Institute of Cell Biology and Immunology, University of Stuttgart, Stuttgart, Germany.

    Protein kinase D (PKD) has been identified as a negative regulator of epithelial cell migration; however, its molecular substrates and downstream signaling pathways that mediate this activity have remained elusive. In this study, we provide evidence that the cofilin phosphatase slingshot 1 like (SSH1L), an important regulator of the complex actin remodeling machinery, is a novel in vivo PKD substrate. PKD-mediated phosphorylation of serines 937 and 978 regulates SSH1L subcellular localization by binding of 14-3-3 proteins and thus impacts the control of local cofilin activation and actin remodeling during cell migration. In line with this, we show that the loss of PKD decreases cofilin phosphorylation, induces a more spread cell morphology, and stimulates chemotactic migration of breast cancer cells in an SSHL1-dependent fashion. Our data thus identify PKD as a central regulator of the cofilin signaling network via direct phosphorylation and regulation of SSH1L.

    Cancer research 2009;69;14;5634-8

  • Proteomic analysis of dorsolateral prefrontal cortex indicates the involvement of cytoskeleton, oligodendrocyte, energy metabolism and new potential markers in schizophrenia.

    Martins-de-Souza D, Gattaz WF, Schmitt A, Maccarrone G, Hunyadi-Gulyás E, Eberlin MN, Souza GH, Marangoni S, Novello JC, Turck CW and Dias-Neto E

    Laboratório de Neurociências, Instituto de Psiquiatria, Faculdade de Medicina da USP, Rua Dr. Ovídio Pires de Campos, SP, Brazil. martins@mpipsykl.mpg.de

    Schizophrenia is likely to be a consequence of serial alterations in a number of genes that, together with environmental factors, will lead to the establishment of the illness. The dorsolateral prefrontal cortex (Brodmann's Area 46) is implicated in schizophrenia and executes high functions such as working memory, differentiation of conflicting thoughts, determination of right and wrong concepts, correct social behavior and personality expression. We performed a comparative proteome analysis using two-dimensional gel electrophoresis of pools from 9 schizophrenia and 7 healthy control patients' dorsolateral prefrontal cortex aiming to identify, by mass spectrometry, alterations in protein expression that could be related to the disease. In schizophrenia-derived samples, our analysis revealed 10 downregulated and 14 upregulated proteins. These included alterations previously implicated in schizophrenia, such as oligodendrocyte-related proteins (myelin basic protein and transferrin), as well as malate dehydrogenase, aconitase, ATP synthase subunits and cytoskeleton-related proteins. Also, six new putative disease markers were identified, including energy metabolism, cytoskeleton and cell signaling proteins. Our data not only reinforces the involvement of proteins previously implicated in schizophrenia, but also suggests new markers, providing further information to foster the comprehension of this important disease.

    Journal of psychiatric research 2009;43;11;978-86

  • BPAG1e maintains keratinocyte polarity through beta4 integrin-mediated modulation of Rac1 and cofilin activities.

    Hamill KJ, Hopkinson SB, DeBiase P and Jones JC

    Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, IL 60611, USA.

    alpha6beta4 integrin, a component of hemidesmosomes, also plays a role in keratinocyte migration via signaling through Rac1 to the actin-severing protein cofilin. Here, we tested the hypothesis that the beta4 integrin-associated plakin protein, bullous pemphigoid antigen 1e (BPAG1e) functions as a scaffold for Rac1/cofilin signal transduction. We generated keratinocyte lines exhibiting a stable knockdown in BPAG1e expression. Knockdown of BPAG1e does not affect expression levels of other hemidesmosomal proteins, nor the amount of beta4 integrin expressed at the cell surface. However, the amount of Rac1 associating with beta4 integrin and the activity of both Rac1 and cofilin are significantly lower in BPAG1e-deficient cells compared with wild-type keratinocytes. In addition, keratinocytes deficient in BPAG1e exhibit loss of front-to-rear polarity and display aberrant motility. These defects are rescued by inducing expression of constitutively active Rac1 or active cofilin. These data indicate that the BPAG1e is required for efficient regulation of keratinocyte polarity and migration by determining the activation of Rac1.

    Funded by: NIAMS NIH HHS: R01 AR054184

    Molecular biology of the cell 2009;20;12;2954-62

  • Reactive oxygen species regulate a slingshot-cofilin activation pathway.

    Kim JS, Huang TY and Bokoch GM

    Department of Immunology and Microbial Science and Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.

    Cellular stimuli generate reactive oxygen species (ROS) via the local action of NADPH oxidases (Nox) to modulate cytoskeletal organization and cell migration through unknown mechanisms. Cofilin is a major regulator of cellular actin dynamics whose activity is controlled by phosphorylation/dephosphorylation at Ser3. Here we show that Slingshot-1L (SSH-1L), a selective cofilin regulatory phosphatase, is involved in H(2)O(2)-induced cofilin dephosphorylation and activation. SSH-1L is activated by its release from a regulatory complex with 14-3-3zeta protein through the redox-mediated oxidation of 14-3-3zeta by H(2)O(2). The ROS-dependent activation of the SSH-1L-cofilin pathway stimulates the SSH-1L-dependent formation of cofilin-actin rods in cofilin-GFP-expressing HeLa cells. Similarly, the formation of endogenous ROS stimulated by angiotensin II (AngII) also activates the SSH-1L-cofilin pathway via oxidation of 14-3-3zeta to increase AngII-induced membrane ruffling and cell motility. These results suggest that the formation of ROS by NADPH oxidases engages a SSH-1L-cofilin pathway to regulate cytoskeletal organization and cell migration.

    Funded by: NHLBI NIH HHS: HL48008, R01 HL048008; NIGMS NIH HHS: GM44428, R01 GM044428

    Molecular biology of the cell 2009;20;11;2650-60

  • Plexin C1, a receptor for semaphorin 7a, inactivates cofilin and is a potential tumor suppressor for melanoma progression.

    Scott GA, McClelland LA, Fricke AF and Fender A

    Department of Dermatology, School of Medicine, University of Rochester, Rochester, New York, USA. Glynis_Scott@urmc.rochester.edu

    Melanocytes are progenitor cells for melanoma, which arises through step-wise progression from dysplastic to invasive, to metastatic tumor. Our previous data showed that semaphorin 7A (Sema7A), a protein involved in axon guidance, stimulates melanocyte adhesion and dendricity through opposing actions of beta1-integrin and Plexin C1 receptors. We now show that Plexin C1 is diminished or absent in human melanoma cell lines; analysis of tissue microarrays of nevi, melanoma, and metastatic melanoma showed a decrease in Plexin C1 expression in metastatic melanoma, and an inverse correlation of Plexin C1 expression with depth of invasion. We examined the signaling intermediates of Sema7A and downstream targets of Plexin C1 in human melanocytes. Sema7A activated mitogen-activated protein kinase and inactivated cofilin, an actin-binding protein involved in cell migration. When Plexin C1 expression was silenced, Sema7A failed to phosphorylate cofilin, indicating that cofilin is downstream of Plexin C1. Further, Lim kinase II, a protein that phosphorylates cofilin, is upregulated by Sema7A in a Plexin C1-dependent manner. These data identify Plexin C1 as a potential tumor suppressor protein in melanoma progression, and suggest that loss of Plexin C1 expression may promote melanoma invasion and metastasis through loss of inhibitory signaling on cofilin activation.

    The Journal of investigative dermatology 2009;129;4;954-63

  • Memo is a cofilin-interacting protein that influences PLCgamma1 and cofilin activities, and is essential for maintaining directionality during ErbB2-induced tumor-cell migration.

    Meira M, Masson R, Stagljar I, Lienhard S, Maurer F, Boulay A and Hynes NE

    Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland.

    Heregulin (HRG) activates ErbB2-ErbB3 heterodimers thereby stimulating many cellular responses, including motility. Memo and PLCgamma1 interact with ErbB2 autophosphorylation sites and are essential for HRG-induced chemotaxis. By tracing HRG-stimulated cell migration in Dunn chambers, we found that Memo- or PLCgamma1 knockdown (KD) strongly impairs cell directionality. Memo has no obvious enzymatic activity and was discovered via its ability to complex with ErbB2. Using the yeast two-hybrid approach to gain insight into Memo function, an interaction between Memo and cofilin, a regulator of actin dynamics, was uncovered. The interaction was confirmed in vitro using recombinant proteins and in vivo in co-immunoprecipitation experiments where Memo was detected in complexes with cofilin, ErbB2 and PLCgamma1. Interestingly, in Memo KD cells, HRG-induced PLCgamma1 phosphorylation was decreased, suggesting that Memo regulates PLCgamma1 activation. Furthermore, HRG-induced recruitment of GFP-cofilin to lamellipodia is impaired in Memo and in PLCgamma1 KD cells, suggesting that both proteins lie upstream of cofilin in models of ErbB2-driven tumor-cell migration. Finally, in vitro F-actin binding and depolymerization assays showed that Memo enhances cofilin depolymerizing and severing activity. In summary, these data indicate that Memo also regulates actin dynamics by interacting with cofilin and enhancing its function.

    Journal of cell science 2009;122;Pt 6;787-97

  • Mutational analysis of CLC-5, cofilin and CLC-4 in patients with Dent's disease.

    Wu F, Reed AA, Williams SE, Loh NY, Lippiat JD, Christie PT, Large O, Bettinelli A, Dillon MJ, Goldraich NP, Hoppe B, Lhotta K, Loirat C, Malik R, Morel D, Kotanko P, Roussel B, Rubinger D, Schrander-Stumpel C, Serdaroglu E, Nesbit MA, Ashcroft F and Thakker RV

    Nuffield Department of Clinical Medicine, Academic Endocrine Unit, University of Oxford, and Churchill Hospital, Oxford Centre for Diabetes, Endocrinology and Metabolism, Oxford, UK.

    Dent's disease is caused by mutations in the chloride/proton antiporter, CLC-5, or oculo-cerebro-renal-syndrome-of-Lowe (OCRL1) genes.

    Methods: Eighteen probands with Dent's disease were investigated for mutations in CLC-5 and two of its interacting proteins, CLC-4 and cofilin. Wild-type and mutant CLC-5s were assessed in kidney cells. Urinary calcium excretion following an oral calcium challenge was studied in one family.

    Results: Seven different CLC-5 mutations consisting of two nonsense mutations (Arg347Stop and Arg718Stop), two missense mutations (Ser244Leu and Arg516Trp), one intron 3 donor splice site mutation, one deletion-insertion (nt930delTCinsA) and an in-frame deletion (523delVal) were identified in 8 patients. In the remaining 10 patients, DNA sequence abnormalities were not detected in the coding regions of CLC-4 or cofilin, and were independently excluded for OCRL1. Patients with CLC-5 mutations were phenotypically similar to those without. The donor splice site CLC-5 mutation resulted in exon 3 skipping. Electrophysiology demonstrated that the 523delVal CLC-5 mutation abolished CLC-5-mediated chloride conductance. Sixty percent of women with the CLC-5 deletion-insertion had nephrolithiasis, although calcium excretion before and after oral calcium challenge was similar to that in unaffected females.

    Conclusions: Three novel CLC-5 mutations were identified, and mutations in OCRL1, CLC-4 and cofilin excluded in causing Dent's disease in this patient cohort.

    Funded by: Medical Research Council: G9825289; Wellcome Trust

    Nephron. Physiology 2009;112;4;p53-62

  • Cofilin mediates tight-junction opening by redistributing actin and tight-junction proteins.

    Nagumo Y, Han J, Bellila A, Isoda H and Tanaka T

    Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan. nag@agbi.tsukuba.ac.jp

    We previously found that capsaicin induces tight-junction (TJ) opening accompanied with cofilin dephosphorylation/activation in intestinal Caco-2 cells. Here, we examined the role of cofilin in TJ regulation, and analyzed the structural events that lead to TJ opening. We transfected Caco-2 cells with wild-type cofilin [cofilin(wt)] or its constitutively active mutant cofilin(S3A). We found that the decreases in transepithelial electrical resistance (TER) was slower in cofilin(wt) transfectants and faster in cofilin(S3A) mutants than in vector controls. Moreover, cofilin dephosphorylation corresponded to the rate of TER decrease. Capsaicin treatment changed the localization of TJ proteins and altered the F-actin structure, but in a manner different from those depend on myosin light chain kinase (MLCK). These results strongly support the importance of cofilin in TJ opening, suggesting cofilin as a target for TJ permeability regulation in epithelial cells.

    Biochemical and biophysical research communications 2008;377;3;921-5

  • A tropomyosin 1 induced defect in cytokinesis can be rescued by elevated expression of cofilin.

    Thoms JA, Loch HM, Bamburg JR, Gunning PW and Weinberger RP

    Oncology Research Unit, The Children's Hospital at Westmead, Westmead, New South Wales, Australia. julie.a.thoms@gmail.com

    Cytokinesis in eukaryotic cells is mediated by the contractile ring, an actomyosin-based structure which provides the force required to separate daughter cells. Isoforms of the actin-binding protein tropomyosin are also localised to the contractile ring in both fission yeast and human astrocytes. Although tropomyosin is required for cytokinesis in yeast, its precise role in the contractile ring is unknown. In this study we find that increased expression of a single tropomyosin isoform, tropomyosin 1, in U373MG astrocytoma cells leads to multinucleated cells and mitotic spindle defects. Furthermore, cells expressing increased levels of tropomyosin 1 usually fail to complete cytokinesis and this is accompanied by reduced accumulation of actin depolymerising factor/cofilin in the contractile ring. Adenovirus mediated expression of cofilin is able to relieve the tropomyosin 1 induced effects on cytokinesis. We conclude that tropomyosin 1 and cofilin play antagonistic roles within the contractile ring and that the balance between tropomyosin 1 and cofilin expression is important for cytokinesis.

    Cell motility and the cytoskeleton 2008;65;12;979-90

  • Molecular dissection of the mechanisms of substrate recognition and F-actin-mediated activation of cofilin-phosphatase Slingshot-1.

    Kurita S, Watanabe Y, Gunji E, Ohashi K and Mizuno K

    Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan.

    Slingshot-1 (SSH1), a member of a dual-specificity protein phosphatase family, regulates actin dynamics by dephosphorylating and reactivating cofilin, an actin-depolymerizing factor. SSH1 has the SSH family-specific, N-terminal, noncatalytic (SSH-N) domain, consisting of the A and B subdomains. SSH1 is activated by binding to actin filaments. In this study, we examined the mechanisms of SSH1 substrate recognition of phospho-cofilin (P-cofilin) and SSH1 activation by F-actin. We found that P-cofilin binds to a phosphatase-inactive mutant, SSH1(CS), in which the catalytic Cys-393 is replaced by Ser. Using a series of deletion mutants, we provided evidence that both the phosphatase (P) domain and the adjacent B domain are indispensable for P-cofilin binding of SSH1(CS) and cofilin-phosphatase activity of SSH1. In contrast, the A domain is required for the F-actin-mediated activation of SSH1, but not for P-cofilin binding or basal cofilin-phosphatase activity. The P domain alone is sufficient for the phosphatase activity toward p-nitrophenyl phosphate (pNPP), indicating that the SSH-N domain is not essential for the basal phosphatase activity of SSH1. Addition of F-actin increased the cofilin-phosphatase activity of SSH1 more than 1200-fold, but the pNPP-phosphatase activity only 2.2-fold, which suggests that F-actin principally affects the cofilin-specific phosphatase activity of SSH1. When expressed in cultured cells, SSH1, but not its mutant deleted of SSH-N, accumulated in the rear of the lamellipodium. Together, these findings suggest that the conserved SSH-N domain plays critical roles in P-cofilin recognition, F-actin-mediated activation, and subcellular localization of SSH1.

    The Journal of biological chemistry 2008;283;47;32542-52

  • Chronophin mediates an ATP-sensing mechanism for cofilin dephosphorylation and neuronal cofilin-actin rod formation.

    Huang TY, Minamide LS, Bamburg JR and Bokoch GM

    Departments of Immunology and Microbial Science, and of Cell Biology, The Scripps Research Institute, IMM14, 10550 N. Torrey Pines Rd., La Jolla, CA 92122, USA.

    Actin and its key regulatory component, cofilin, are found together in large rod-shaped assemblies in neurons subjected to energy stress. Such inclusions are also enriched in Alzheimer's disease brain, and appear in transgenic models of neurodegeneration. Neuronal insults, such as energy loss and/or oxidative stress, result in rapid dephosphorylation of the cellular cofilin pool prior to its assembly into rod-shaped inclusions. Although these events implicate a role for phosphatases in cofilin rod formation, a mechanism linking energy stress, phosphocofilin turnover, and subsequent rod assembly has been elusive. We demonstrate the ATP-sensitive interaction of the cofilin phosphatase chronophin (CIN) with the chaperone hsp90 to form a biosensor that mediates cofilin/actin rod formation. Our results suggest a model whereby attenuated interactions between CIN and hsp90 during ATP depletion enhance CIN-dependent cofilin dephosphorylation and consequent rod assembly, thereby providing a mechanism for the formation of pathological actin/cofilin aggregates during neurodegenerative energy flux.

    Funded by: NIGMS NIH HHS: GM44428, R01 GM044428, R01 GM044428-17, R01 GM044428-18; NINDS NIH HHS: NS40371, R01 NS040371

    Developmental cell 2008;15;5;691-703

  • HIV envelope-CXCR4 signaling activates cofilin to overcome cortical actin restriction in resting CD4 T cells.

    Yoder A, Yu D, Dong L, Iyer SR, Xu X, Kelly J, Liu J, Wang W, Vorster PJ, Agulto L, Stephany DA, Cooper JN, Marsh JW and Wu Y

    Department of Molecular and Microbiology, George Mason University, Manassas, VA 20110, USA.

    Binding of the HIV envelope to the chemokine coreceptors triggers membrane fusion and signal transduction. The fusion process has been well characterized, yet the role of coreceptor signaling remains elusive. Here, we describe a critical function of the chemokine coreceptor signaling in facilitating HIV infection of resting CD4 T cells. We find that static cortical actin in resting T cells represents a restriction and that HIV utilizes the Galphai-dependent signaling from the chemokine coreceptor CXCR4 to activate a cellular actin-depolymerizing factor, cofilin, to overcome this restriction. HIV envelope-mediated cofilin activation and actin dynamics are important for a postentry process that leads to viral nuclear localization. Inhibition of HIV-mediated actin rearrangement markedly diminishes viral latent infection of resting T cells. Conversely, induction of active cofilin greatly facilitates it. These findings shed light on viral exploitation of cellular machinery in resting T cells, where chemokine receptor signaling becomes obligatory.

    Funded by: NIAID NIH HHS: AI069981, R21 AI069981, R21 AI069981-01A2, R21 AI069981-02

    Cell 2008;134;5;782-92

  • Mitochondrial shuttling of CAP1 promotes actin- and cofilin-dependent apoptosis.

    Wang C, Zhou GL, Vedantam S, Li P and Field J

    Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.

    Mitochondria play a central role in regulating apoptosis by releasing proapoptotic contents such as cytochrome c, and generating reactive oxygen species (ROS). Early in apoptosis, proteins translocate to mitochondria to promote the release of their contents. Here, we show that the actin- and cofilin-interacting protein CAP1 has a role in apoptosis. When we induced apoptosis, CAP1 rapidly translocated to the mitochondria independently of caspase activation. Translocation was proapoptotic because CAP1-knockdown cells were resistant to apoptosis inducers. Overexpression of wild-type CAP1 did not stimulate apoptosis on its own, but stimulated cofilin-induced apoptosis. Apoptosis induction required a mitochondrial-targeting domain, localized in the N-terminus and also the actin-binding domain in the C-terminus. Taken together, these studies suggest that CAP1 provides a direct link from the actin cytoskeleton to the mitochondria by functioning as an actin shuttle.

    Funded by: NIGMS NIH HHS: GM48241, R01 GM048241, R01 GM048241-16

    Journal of cell science 2008;121;Pt 17;2913-20

  • Dual regulation of cofilin activity by LIM kinase and Slingshot-1L phosphatase controls platelet-derived growth factor-induced migration of human aortic smooth muscle cells.

    San Martín A, Lee MY, Williams HC, Mizuno K, Lassègue B and Griendling KK

    Division of Cardiology, Emory University, 1639 Pierce Dr, 319 WMB, Atlanta, GA 30322, USA.

    Platelet-derived growth factor (PDGF) plays a central role in vascular healing, atherosclerosis, and restenosis, partly by stimulating vascular smooth muscle cell (VSMC) migration. Migration requires rapid turnover of actin filaments, which is partially controlled by cofilin. Although cofilin is negatively regulated by Ser3 phosphorylation, the upstream signaling pathways have not been defined, nor has its role in VSMC migration been studied. We hypothesized that PDGF-induced migration of VSMCs involves cofilin activation and that this is regulated by the serine kinase LIM kinase (LIMK) and the novel phosphatase Slingshot (SSH)1L. In human VSMCs, stimulation with PDGF increased G-actin incorporation into the actin cytoskeleton. PDGF transiently activated the cofilin kinase, LIMK, with a peak at 5 minutes. However, cofilin was dephosphorylated between 5 and 45 minutes, with a maximum of 43+/-5% dephosphorylation at 30 minutes, suggesting that PDGF also activates a cofilin phosphatase. We found that VSMCs express SSH1L, which is induced and activated (564+/-73 versus 1021+/-141 picomoles of PO(4); P=0.015) by PDGF. Of importance, small interfering RNA directed against SSH1L blocked cofilin dephosphorylation and decreased migration (528+/-33 versus 318+/-25 cells/field; P<0.01). Taken together, our results suggest that PDGF participates in actin dynamics by dual regulation of cofilin activity via LIMK and SSH1L.

    Funded by: NHLBI NIH HHS: HL058863, HL38206

    Circulation research 2008;102;4;432-8

  • Differential involvement of destrin and cofilin-1 in the control of invasive properties of Isreco1 human colon cancer cells.

    Estornes Y, Gay F, Gevrey JC, Navoizat S, Nejjari M, Scoazec JY, Chayvialle JA, Saurin JC and Abello J

    Inserm, U865, Lyon, F-69372 France.

    Actin depolymerizing factor (ADF)/cofilin family proteins are key regulators of actin filament turnover and cytoskeleton reorganization. The role of cofilin-1 in cell motility has been demonstrated in several cell types but remained poorly documented in the case of colon cancer. In addition, the putative function of destrin (also known as ADF) had not been explored in this context despite the fact that it is expressed in all colon cancer cell lines examined. We were therefore prompted to evaluate the respective contributions of these proteins to the invasive properties of the human colon cancer Isreco1 cell line, which expresses a comparatively high destrin/cofilin ratio. Reduction of cofilin-1 or destrin expression in Isreco1 cells using RNA interference led to an increase of the number of multinucleated cells and altered polarized lamellipodium protrusion and distribution of paxillin-containing adhesions. Both cofilin-1 and destrin silencing enhanced cell adhesion to extracellular matrix components. However, only destrin appeared to be required for cell migration on collagen I and for cell invasion through Matrigel in response to the proinvasive neuroendocrine peptide bombesin. This differential functional involvement was supported by a destrin-dependent, cofilin-independent phosphorylation of p130Crk-associated substrate (p130Cas) upon cell adhesion to collagen I or Matrigel. Taken together, our results suggest that destrin is a significant regulator of various processes important for invasive phenotype of human colon cancer Isreco1 cells whereas cofilin-1 may be involved in only a subset of them.

    International journal of cancer 2007;121;10;2162-71

  • Association between CFL1 gene polymorphisms and spina bifida risk in a California population.

    Zhu H, Enaw JO, Ma C, Shaw GM, Lammer EJ and Finnell RH

    Center for Environmental and Genetic Medicine, Institute of Biosciences and Technology, Texas A&M University System Health Science Center, Houston, Texas 77030, USA. Hzhu@ibt.tamhsc.edu

    Background: CFL1 encodes human non-muscle cofilin (n-cofilin), which is an actin-depolymerizing factor and is essential in cytokinesis, endocytosis, and in the development of all embryonic tissues. Cfl1 knockout mice exhibit failure of neural tube closure at E10.5 and die in utero. We hypothesized that genetic variation within the human CFL1 gene may alter the protein's function and result in defective actin depolymerizing and cellular activity during neural tube closure. Such alterations may be associated with an increased risk for neural tube defects (NTDs).

    Methods: Having re-sequenced the human CFL1 gene and identified five common single nucleotide polymorphisms (SNPs) in our target population, we investigated whether there existed a possible association between the genetic variations of the CFL1 gene and risk of spina bifida. Samples were obtained from a large population-based case-control study in California. Allele association, genotype association and haplotype association were evaluated in two different ethnicity groups, non-Hispanic white and Hispanic white.

    Results: Homozygosity for the minor alleles of the SNPs studied (rs652021, rs665306, rs667555, rs4621 and rs11227332) appeared to produce an increased risk for spina bifida. Subjects with the haplotype composed of all minor alleles (CCGGT) appeared to have increased spina bifida risk (OR = 1.6, 95% CI: 0.9~2.9), however, this finding is not statistically significant likely due to limited sample size.

    Conclusion: The sequence variation of human CFL1 gene is a genetic modifier for spina bifida risk in this California population.

    Funded by: NINDS NIH HHS: R01 NS050249, R01NS050249

    BMC medical genetics 2007;8;12

  • Mapping the ADF/cofilin binding site on monomeric actin by competitive cross-linking and peptide array: evidence for a second binding site on monomeric actin.

    Mannherz HG, Ballweber E, Galla M, Villard S, Granier C, Steegborn C, Schmidtmann A, Jaquet K, Pope B and Weeds AG

    Department of Anatomy and Embryology Ruhr-University, Bochum, Germany. hans.g.mannherz@rub.de

    The binding sites for actin depolymerising factor (ADF) and cofilin on G-actin have been mapped by competitive chemical cross-linking using deoxyribonuclease I (DNase I), gelsolin segment 1 (G1), thymosin beta4 (Tbeta4), and vitamin D-binding protein (DbP). To reduce ADF/cofilin induced actin oligomerisation we used ADP-ribosylated actin. Both vitamin D-binding protein and thymosin beta4 inhibit binding by ADF or cofilin, while cofilin or ADF and DNase I bind simultaneously. Competition was observed between ADF or cofilin and G1, supporting the hypothesis that cofilin preferentially binds in the cleft between sub-domains 1 and 3, similar to or overlapping the binding site of G1. Because the affinity of G1 is much higher than that of ADF or cofilin, even at a 20-fold excess of the latter, the complexes contained predominantly G1. Nevertheless, cross-linking studies using actin:G1 complexes and ADF or cofilin showed the presence of low concentrations of ternary complexes containing both ADF or cofilin and G1. Thus, even with monomeric actin, it is shown for the first time that binding sites for both G1 and ADF or cofilin can be occupied simultaneously, confirming the existence of two separate binding sites. Employing a peptide array with overlapping sequences of actin overlaid by cofilin, we have identified five sequence stretches of actin able to bind cofilin. These sequences are located within the regions of F-actin predicted to bind cofilin in the model derived from image reconstructions of electron microscopical images of cofilin-decorated filaments. Three of the peptides map to the cleft region between sub-domains 1 and 3 of the upper actin along the two-start long-pitch helix, while the other two are in the DNase I loop corresponding to the site of the lower actin in the helix. In the absence of any crystal structures of ADF or cofilin in complex with actin, these studies provide further information about the binding sites on F-actin for these important actin regulatory proteins.

    Funded by: Medical Research Council: MC_U105184340

    Journal of molecular biology 2007;366;3;745-55

  • Large-scale mapping of human protein-protein interactions by mass spectrometry.

    Ewing RM, Chu P, Elisma F, Li H, Taylor P, Climie S, McBroom-Cerajewski L, Robinson MD, O'Connor L, Li M, Taylor R, Dharsee M, Ho Y, Heilbut A, Moore L, Zhang S, Ornatsky O, Bukhman YV, Ethier M, Sheng Y, Vasilescu J, Abu-Farha M, Lambert JP, Duewel HS, Stewart II, Kuehl B, Hogue K, Colwill K, Gladwish K, Muskat B, Kinach R, Adams SL, Moran MF, Morin GB, Topaloglou T and Figeys D

    Protana, Toronto, Ontario, Canada.

    Mapping protein-protein interactions is an invaluable tool for understanding protein function. Here, we report the first large-scale study of protein-protein interactions in human cells using a mass spectrometry-based approach. The study maps protein interactions for 338 bait proteins that were selected based on known or suspected disease and functional associations. Large-scale immunoprecipitation of Flag-tagged versions of these proteins followed by LC-ESI-MS/MS analysis resulted in the identification of 24,540 potential protein interactions. False positives and redundant hits were filtered out using empirical criteria and a calculated interaction confidence score, producing a data set of 6463 interactions between 2235 distinct proteins. This data set was further cross-validated using previously published and predicted human protein interactions. In-depth mining of the data set shows that it represents a valuable source of novel protein-protein interactions with relevance to human diseases. In addition, via our preliminary analysis, we report many novel protein interactions and pathway associations.

    Molecular systems biology 2007;3;89

  • 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

  • Expression of nonmuscle cofilin-1 and steroid responsiveness in severe asthma.

    Vasavda N, Eichholtz T, Takahashi A, Affleck K, Matthews JG, Barnes PJ and Adcock IM

    Airways Disease Section, National Heart and Lung Institute, Imperial College London, London, UK.

    Background: Glucocorticoids are the mainstay of asthma therapy; however, a proportion of patients with asthma has a severe form of the disease that fails to respond to therapy. Understanding the molecular mechanisms behind glucocorticoid-insensitive asthma is therefore of clinical importance. Evidence in glucocorticoid-unresponsive Henrietta Lack (HeLa) cells indicated that cofilin-1 could act as an inhibitor of glucocorticoid function.

    Objective: To determine whether cofilin-1 expression is abnormally expressed in cells from patients with severe glucocorticoid-insensitive asthma and examine the effect of cofilin-1 overexpression on glucocorticoid function.

    Methods: Peripheral blood CD4(+) T cells were purified from 16 subjects with severe glucocorticoid-insensitive asthma and 16 subjects with mild glucocorticoid-sensitive asthma, and cofilin-1 expression was determined by quantitative real-time RT-PCR and Western blotting. The effect of dexamethasone on cofilin-1 expression was determined in Jurkat T cells, and the effect of cofilin-1 overexpression on anti-CD3/CD28-stimulated IL-2 release was measured.

    Results: Peripheral blood CD4(+) T cells from subjects with severe glucocorticoid-insensitive asthma are less responsive to dexamethasone than cells from subjects with mild glucocorticoid-sensitive asthma. Cells from these patients express significantly (P < .05) higher levels of cofilin-1 than cells from subjects with mild asthma. Dexamethasone did not affect cofilin-1 expression in Jurkat T cells. Functionally, dexamethasone suppression of anti-CD3/CD28-stimulated IL-2 was attenuated in Jurkat cells overexpressing cofilin-1.

    Conclusion: These results suggest that increased cofilin-1 expression may be important in the regulation of glucocorticoid sensitivity in peripheral blood lymphocytes of patients with severe treatment-insensitive asthma.

    Understanding the mechanisms of enhanced cofilin-1 expression may lead to the development of new therapies for severe treatment-insensitive asthma.

    The Journal of allergy and clinical immunology 2006;118;5;1090-6

  • A probability-based approach for high-throughput protein phosphorylation analysis and site localization.

    Beausoleil SA, Villén J, Gerber SA, Rush J and Gygi SP

    Department of Cell Biology, Harvard Medical School, 240 Longwood Ave., Boston, Massachusetts 02115, USA.

    Data analysis and interpretation remain major logistical challenges when attempting to identify large numbers of protein phosphorylation sites by nanoscale reverse-phase liquid chromatography/tandem mass spectrometry (LC-MS/MS) (Supplementary Figure 1 online). In this report we address challenges that are often only addressable by laborious manual validation, including data set error, data set sensitivity and phosphorylation site localization. We provide a large-scale phosphorylation data set with a measured error rate as determined by the target-decoy approach, we demonstrate an approach to maximize data set sensitivity by efficiently distracting incorrect peptide spectral matches (PSMs), and we present a probability-based score, the Ascore, that measures the probability of correct phosphorylation site localization based on the presence and intensity of site-determining ions in MS/MS spectra. We applied our methods in a fully automated fashion to nocodazole-arrested HeLa cell lysate where we identified 1,761 nonredundant phosphorylation sites from 491 proteins with a peptide false-positive rate of 1.3%.

    Funded by: NHGRI NIH HHS: HG03456; NIGMS NIH HHS: GM67945

    Nature biotechnology 2006;24;10;1285-92

  • Substrate and functional diversity of lysine acetylation revealed by a proteomics survey.

    Kim SC, Sprung R, Chen Y, Xu Y, Ball H, Pei J, Cheng T, Kho Y, Xiao H, Xiao L, Grishin NV, White M, Yang XJ and Zhao Y

    Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.

    Acetylation of proteins on lysine residues is a dynamic posttranslational modification that is known to play a key role in regulating transcription and other DNA-dependent nuclear processes. However, the extent of this modification in diverse cellular proteins remains largely unknown, presenting a major bottleneck for lysine-acetylation biology. Here we report the first proteomic survey of this modification, identifying 388 acetylation sites in 195 proteins among proteins derived from HeLa cells and mouse liver mitochondria. In addition to regulators of chromatin-based cellular processes, nonnuclear localized proteins with diverse functions were identified. Most strikingly, acetyllysine was found in more than 20% of mitochondrial proteins, including many longevity regulators and metabolism enzymes. Our study reveals previously unappreciated roles for lysine acetylation in the regulation of diverse cellular pathways outside of the nucleus. The combined data sets offer a rich source for further characterization of the contribution of this modification to cellular physiology and human diseases.

    Funded by: NCI NIH HHS: CA107943

    Molecular cell 2006;23;4;607-18

  • A protein-protein interaction network for human inherited ataxias and disorders of Purkinje cell degeneration.

    Lim J, Hao T, Shaw C, Patel AJ, Szabó G, Rual JF, Fisk CJ, Li N, Smolyar A, Hill DE, Barabási AL, Vidal M and Zoghbi HY

    Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.

    Many human inherited neurodegenerative disorders are characterized by loss of balance due to cerebellar Purkinje cell (PC) degeneration. Although the disease-causing mutations have been identified for a number of these disorders, the normal functions of the proteins involved remain, in many cases, unknown. To gain insight into the function of proteins involved in PC degeneration, we developed an interaction network for 54 proteins involved in 23 inherited ataxias and expanded the network by incorporating literature-curated and evolutionarily conserved interactions. We identified 770 mostly novel protein-protein interactions using a stringent yeast two-hybrid screen; of 75 pairs tested, 83% of the interactions were verified in mammalian cells. Many ataxia-causing proteins share interacting partners, a subset of which have been found to modify neurodegeneration in animal models. This interactome thus provides a tool for understanding pathogenic mechanisms common for this class of neurodegenerative disorders and for identifying candidate genes for inherited ataxias.

    Funded by: NICHD NIH HHS: HD24064; NINDS NIH HHS: NS27699

    Cell 2006;125;4;801-14

  • Modifications in the human T cell proteome induced by intracellular HIV-1 Tat protein expression.

    Coiras M, Camafeita E, Ureña T, López JA, Caballero F, Fernández B, López-Huertas MR, Pérez-Olmeda M and Alcamí J

    AIDS Immunopathology Unit, National Centre of Microbiology, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.

    The effects of the human immunodeficiency virus type 1 (HIV-1) Tat protein on cellular gene expression were analysed using a Jurkat cell line that was stably transfected with tat gene in a doxycycline-repressible expression system. Expressed Tat protein (aa 1-101) was proved to present basically a nuclear localisation, and to be fully functional to induce HIV LTR transactivation. Tat expression also resulted in protection from Tunicamycin-induced apoptosis as determined by DNA staining and TUNEL assays. We applied proteomics methods to investigate changes in differential protein expression in the transfected Jurkat-Tat cells. Protein identification was performed using 2-D DIGE followed by MS analysis. We identified the down-regulation of several cytoskeletal proteins such as actin, beta-tubulin, annexin II, as well as gelsolin, cofilin and the Rac/Rho-GDI complex. Down-expression of these proteins could be involved in the survival of long-term reservoirs of HIV-infected CD4+ T cells responsible for continuous viral production. In conclusion, in addition to its role in viral mRNA elongation, the proteomic approach has provided insight into the way that Tat modifies host cell gene expression.

    Proteomics 2006;6 Suppl 1;S63-73

  • Transcriptomic and proteomic analyses of rhabdomyosarcoma cells reveal differential cellular gene expression in response to enterovirus 71 infection.

    Leong WF and Chow VT

    Human Genome Laboratory, Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Kent Ridge, Singapore 117597.

    Insights into the host antiviral strategies as well as viral disease manifestations can be achieved through the elucidation of host- and virus-mediated transcriptional responses. An oligo-based microarray was employed to analyse mRNAs from rhabdomyosarcoma cells infected with the MS/7423/87 strain of enterovirus 71 (EV71) at 20 h post infection. Using Acuity software and LOWESS normalization, 152 genes were found to be downregulated while 39 were upregulated by greater than twofold. Altered transcripts include those encoding components of cytoskeleton, protein translation and modification; cellular transport proteins; protein degradation mediators; cell death mediators; mitochondrial-related and metabolism proteins; cellular receptors and signal transducers. Changes in expression profiles of 15 representative genes were authenticated by real-time reverse transcription polymerase chain reaction (RT-PCR), which also compared the transcriptional responses of cells infected with EV71 strain 5865/Sin/000009 isolated from a fatal case during the Singapore outbreak in 2000. Western blot analyses of APOB, CLU, DCAMKL1 and ODC1 proteins correlated protein and transcript levels. Two-dimensional proteomic maps highlighted differences in expression of cellular proteins (CCT5, CFL1, ENO1, HSPB1, PSMA2 and STMN1) following EV71 infection. Expression of several apoptosis-associated genes was modified, coinciding with apoptosis attenuation observed in poliovirus infection. Interestingly, doublecortin and CaM kinase-like 1 (DCAMKL1) involved in brain development, was highly expressed during infection. Thus, microarray, real-time RT-PCR and proteomic analyses can elucidate the global view of the numerous and complex cellular responses that contribute towards EV71 pathogenesis.

    Cellular microbiology 2006;8;4;565-80

  • MAPKAPK-2-mediated LIM-kinase activation is critical for VEGF-induced actin remodeling and cell migration.

    Kobayashi M, Nishita M, Mishima T, Ohashi K and Mizuno K

    Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi, Japan.

    Vascular endothelial growth factor-A (VEGF-A) induces actin reorganization and migration of endothelial cells through a p38 mitogen-activated protein kinase (MAPK) pathway. LIM-kinase 1 (LIMK1) induces actin remodeling by phosphorylating and inactivating cofilin, an actin-depolymerizing factor. In this study, we demonstrate that activation of LIMK1 by MAPKAPK-2 (MK2; a downstream kinase of p38 MAPK) represents a novel signaling pathway in VEGF-A-induced cell migration. VEGF-A induced LIMK1 activation and cofilin phosphorylation, and this was inhibited by the p38 MAPK inhibitor SB203580. Although p38 phosphorylated LIMK1 at Ser-310, it failed to activate LIMK1 directly; however, MK2 activated LIMK1 by phosphorylation at Ser-323. Expression of a Ser-323-non-phosphorylatable mutant of LIMK1 suppressed VEGF-A-induced stress fiber formation and cell migration; however, expression of a Ser-323-phosphorylation-mimic mutant enhanced these processes. Knockdown of MK2 by siRNA suppressed VEGF-A-induced LIMK1 activation, stress fiber formation, and cell migration. Expression of kinase-dead LIMK1 suppressed VEGF-A-induced tubule formation. These findings suggest that MK2-mediated LIMK1 phosphorylation/activation plays an essential role in VEGF-A-induced actin reorganization, migration, and tubule formation of endothelial cells.

    The EMBO journal 2006;25;4;713-26

  • Insulin-dependent interactions of proteins with GLUT4 revealed through stable isotope labeling by amino acids in cell culture (SILAC).

    Foster LJ, Rudich A, Talior I, Patel N, Huang X, Furtado LM, Bilan PJ, Mann M and Klip A

    Center for Experimental BioInformatics (CEBI), Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.

    The insulin-regulated glucose transporter (GLUT4) translocates to the plasma membrane in response to insulin in order to facilitate the postprandial uptake of glucose into fat and muscle cells. While early insulin receptor signaling steps leading to this translocation are well defined, the integration of signaling and regulation of GLUT4 traffic remains elusive. Several lines of evidence suggest an important role for the actin cytoskeleton and for protein-protein interactions in regulating GLUT4 localization by insulin. Here, we applied stable isotope labeling by amino acids in cell culture (SILAC) to identify proteins that interact with GLUT4 in an insulin-regulated manner. Myc-tagged GLUT4 (GLUT4myc) stably expressed in L6 myotubes was immunoprecipitated via the myc epitope from total membranes isolated from basal and insulin-stimulated cells grown in medium containing normal isotopic abundance leucine or deuterated leucine, respectively. Proteins coprecipitating with GLUT4myc were analyzed by liquid chromatography/ tandem mass spectrometry. Of 603 proteins quantified, 36 displayed an insulin-dependent change of their interaction with GLUT4myc of more than 1.5-fold in either direction. Several cytoskeleton-related proteins were elevated in immunoprecipates from insulin-treated cells, whereas components of the ubiquitin-proteasome degradation system were generally reduced. Proteins participating in vesicle traffic also displayed insulin-regulated association. Of cytoskeleton-related proteins, alpha-actinin-4 recovery in GLUT4 immunoprecipitates rose in response to insulin 2.1 +/- 0.5-fold by SILAC and 2.9 +/- 0.8-fold by immunoblotting. Insulin caused GLUT4 and alpha-actinin-4 co-localization as revealed by confocal immunofluorescence microscopy. We conclude that insulin elicits changes in interactions between diverse proteins and GLUT4, and that cytoskeletal proteins, notably alpha-actinin-4, associate with the transporter, potentially to facilitate its routing to the plasma membrane.

    Journal of proteome research 2006;5;1;64-75

  • Inhibition of invasiveness of human lung cancer cell line H1299 by over-expression of cofilin.

    Lee YJ, Mazzatti DJ, Yun Z and Keng PC

    Department of Therapeutic Radiology, Yale University, 333 Cedar Street, New Haven, CT 06510, USA. y1343@e-mail.med.yale.edu

    The Rho-LIM-kinase (LIMK) signaling pathway, believed to be involved in the regulation of tumor invasion, specifically regulates the activity of cofilin. However, it is unclear whether cofilin plays a pivotal role in tumor invasiveness. In this paper we show using a tet-on gene expression system that over-expression of cofilin inhibits the invasiveness of human lung cancer H1299 cells. Over-expressed cofilin disrupts the actin cytoskeleton at the leading edge of the cell and up-regulates p27(kip1), which is known to be involved in regulating cell motility. Removal of cofilin over-expression normalizes the p27(kip1) level and concomitantly restores the invasiveness of the cultured cells. These findings suggest that excessive cofilin production might prevent cancer cell invasion.

    Cell biology international 2005;29;11;877-83

  • Towards a proteome-scale map of the human protein-protein interaction network.

    Rual JF, Venkatesan K, Hao T, Hirozane-Kishikawa T, Dricot A, Li N, Berriz GF, Gibbons FD, Dreze M, Ayivi-Guedehoussou N, Klitgord N, Simon C, Boxem M, Milstein S, Rosenberg J, Goldberg DS, Zhang LV, Wong SL, Franklin G, Li S, Albala JS, Lim J, Fraughton C, Llamosas E, Cevik S, Bex C, Lamesch P, Sikorski RS, Vandenhaute J, Zoghbi HY, Smolyar A, Bosak S, Sequerra R, Doucette-Stamm L, Cusick ME, Hill DE, Roth FP and Vidal M

    Center for Cancer Systems Biology and Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston, Massachusetts 02115, USA.

    Systematic mapping of protein-protein interactions, or 'interactome' mapping, was initiated in model organisms, starting with defined biological processes and then expanding to the scale of the proteome. Although far from complete, such maps have revealed global topological and dynamic features of interactome networks that relate to known biological properties, suggesting that a human interactome map will provide insight into development and disease mechanisms at a systems level. Here we describe an initial version of a proteome-scale map of human binary protein-protein interactions. Using a stringent, high-throughput yeast two-hybrid system, we tested pairwise interactions among the products of approximately 8,100 currently available Gateway-cloned open reading frames and detected approximately 2,800 interactions. This data set, called CCSB-HI1, has a verification rate of approximately 78% as revealed by an independent co-affinity purification assay, and correlates significantly with other biological attributes. The CCSB-HI1 data set increases by approximately 70% the set of available binary interactions within the tested space and reveals more than 300 new connections to over 100 disease-associated proteins. This work represents an important step towards a systematic and comprehensive human interactome project.

    Funded by: NCI NIH HHS: R33 CA132073; NHGRI NIH HHS: P50 HG004233, R01 HG001715, RC4 HG006066, U01 HG001715; NHLBI NIH HHS: U01 HL098166

    Nature 2005;437;7062;1173-8

  • Proteomics of human umbilical vein endothelial cells applied to etoposide-induced apoptosis.

    Bruneel A, Labas V, Mailloux A, Sharma S, Royer N, Vinh J, Pernet P, Vaubourdolle M and Baudin B

    Service de Biochimie A, Hôpital Saint-Antoine, AP-HP, Paris, France. arnaud.bruneel@sat.ap-hop-paris.fr

    We have undertaken to continue the proteomic study of human umbilical vein endothelial cells (HUVECs) using the combination of 2-DE, automated trypsin digestion, and PMF analysis after MALDI-TOF MS and peptide sequencing using nano LC-ESI-MS/MS. The overall functional characterization of the 162 identified proteins from primary cultures of HUVECs confirms the metabolic capabilities of endothelium and illustrates various cellular functions more related to cell motility and angiogenesis, protein folding, anti-oxidant defenses, signal transduction, proteasome pathway and resistance to apoptosis. In comparison with controls cells, the differential proteomic analysis of HUVECs treated by the pro-apoptotic topoisomerase inhibitor etoposide further revealed the variation of eight proteins, namely, GRP78, GRP94, valosin-containing protein, proteinase inhibitor 9, cofilin, 37-kDa laminin receptor protein, bovine apolipoprotein, and tropomyosin. These data suggest that etoposide-induced apoptosis of human vascular endothelial cells results from the intricate involvement of multiple apoptosis processes including at least the mitochondrial and the ER stress pathways. The presented 2-D pattern and protein database, as well as the data related to apoptosis of HUVECs, are available at http://www.huvec.com.

    Proteomics 2005;5;15;3876-84

  • A human protein-protein interaction network: a resource for annotating the proteome.

    Stelzl U, Worm U, Lalowski M, Haenig C, Brembeck FH, Goehler H, Stroedicke M, Zenkner M, Schoenherr A, Koeppen S, Timm J, Mintzlaff S, Abraham C, Bock N, Kietzmann S, Goedde A, Toksöz E, Droege A, Krobitsch S, Korn B, Birchmeier W, Lehrach H and Wanker EE

    Max Delbrueck Center for Molecular Medicine, 13092 Berlin-Buch, Germany.

    Protein-protein interaction maps provide a valuable framework for a better understanding of the functional organization of the proteome. To detect interacting pairs of human proteins systematically, a protein matrix of 4456 baits and 5632 preys was screened by automated yeast two-hybrid (Y2H) interaction mating. We identified 3186 mostly novel interactions among 1705 proteins, resulting in a large, highly connected network. Independent pull-down and co-immunoprecipitation assays validated the overall quality of the Y2H interactions. Using topological and GO criteria, a scoring system was developed to define 911 high-confidence interactions among 401 proteins. Furthermore, the network was searched for interactions linking uncharacterized gene products and human disease proteins to regulatory cellular pathways. Two novel Axin-1 interactions were validated experimentally, characterizing ANP32A and CRMP1 as modulators of Wnt signaling. Systematic human protein interaction screens can lead to a more comprehensive understanding of protein function and cellular processes.

    Cell 2005;122;6;957-68

  • Enhancement of radiosensitivity in H1299 cancer cells by actin-associated protein cofilin.

    Lee YJ, Sheu TJ and Keng PC

    Department of Pathology and Laboratory Medicine, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA. lee_yi_jang@hotmail.com

    Cofilin is an actin-associated protein that belongs to the actin depolymerization factor/cofilin family and is important for regulation of actin dynamics. Cofilin can import actin monomers into the nucleus under certain stress conditions, however the biological effects of nuclear transport are unclear. In this study, we found that over-expression of cofilin led to increased radiation sensitivity in human non-small lung cancer H1299 cells. Cell survival as determined by colony forming assay showed that cells over-expressing cofilin were more sensitive to ionizing radiation (IR) than normal cells. To determine whether the DNA repair capacity was altered in cofilin over-expressing cells, comet assays were performed on irradiated cells. Repair of DNA damage caused by ionizing radiation was detected in cofilin over-expressing cells after 24 h of recovery. Consistent with this observation, the key components for repair of DNA double-strand breaks, including Rad51, Rad52, and Ku70/Ku80, were down-regulated in cofilin over-expressing cells after IR exposure. These findings suggest that cofilin can influence radiosensitivity by altering DNA repair capacity.

    Biochemical and biophysical research communications 2005;335;2;286-91

  • Protein profiling of human pancreatic islets by two-dimensional gel electrophoresis and mass spectrometry.

    Ahmed M, Forsberg J and Bergsten P

    Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden. meftun.khandker@drl.ox.ac.uk

    Completion of the human genome sequence has provided scientists with powerful resources with which to explore the molecular events associated with disease states such as diabetes. Understanding the relative levels of expression of gene products, especially of proteins, and their post-translational modifications will be critical. However, though the pancreatic islets play a key role in glucose homeostasis, global protein expression data in human are decidedly lacking. We here report the two-dimensional protein map and database of human pancreatic islets. A high level of reproducibility was obtained among the gels and a total of 744 protein spots were detected. We have successfully identified 130 spots corresponding to 66 different protein entries and generated a reference map of human islets. The functionally characterized proteins include enzymes, chaperones, cellular structural proteins, cellular defense proteins, signaling molecules, and transport proteins. A number of proteins identified in this study (e.g., annexin A2, elongation factor 1-alpha 2, histone H2B.a/g/k, heat shock protein 90 beta, heat shock 27 kDa protein, cyclophilin B, peroxiredoxin 4, cytokeratins 7, 18, and 19) have not been previously described in the database of mouse pancreatic islets. In addition, altered expression of several proteins, like GRP78, GRP94, PDI, calreticulin, annexin, cytokeratins, profilin, heat shock proteins, and ORP150 have been associated with the development of diabetes. The data presented in this study provides a first-draft reference map of the human islet proteome, that will pave the way for further proteome analysis of pancreatic islets in both healthy and diabetic individuals, generating insights into the pathophysiology of this condition.

    Journal of proteome research 2005;4;3;931-40

  • Calcium signal-induced cofilin dephosphorylation is mediated by Slingshot via calcineurin.

    Wang Y, Shibasaki F and Mizuno K

    Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan.

    Cofilin, an essential regulator of actin filament dynamics, is inactivated by phosphorylation at Ser-3 and reactivated by dephosphorylation. Although cofilin undergoes dephosphorylation in response to extracellular stimuli that elevate intracellular Ca2+ concentrations, signaling mechanisms mediating Ca2+-induced cofilin dephosphorylation have remained unknown. We investigated the role of Slingshot (SSH) 1L, a member of a SSH family of protein phosphatases, in mediating Ca2+-induced cofilin dephosphorylation. The Ca2+ ionophore A23187 and Ca2+-mobilizing agonists, ATP and histamine, induced SSH1L activation and cofilin dephosphorylation in cultured cells. A23187- or histamine-induced SSH1L activation and cofilin dephosphorylation were blocked by calcineurin inhibitors or a dominant-negative form of calcineurin, indicating that calcineurin mediates Ca2+-induced SSH1L activation and cofilin dephosphorylation. Importantly, knockdown of SSH1L expression by RNA interference abolished A23187- or calcineurin-induced cofilin dephosphorylation. Furthermore, calcineurin dephosphorylated SSH1L and increased the cofilin-phosphatase activity of SSH1L in cell-free assays. Based on these findings, we suggest that Ca2+-induced cofilin dephosphorylation is mediated by calcineurin-dependent activation of SSH1L.

    The Journal of biological chemistry 2005;280;13;12683-9

  • Proteomic profiling identifies an UV-induced activation of cofilin-1 and destrin in human epidermis.

    Hensbergen P, Alewijnse A, Kempenaar J, van der Schors RC, van der Schors R, Balog CA, Deelder A, Beumer G, Ponec M and Tensen CP

    Department of Dermatology, Leiden University Medical Center, Leiden, The Netherlands.

    The human skin is the only line of defense against UV radiation. A series of responses to protect the skin are induced by UV radiation. In this study, a proteomic approach was used to study these responses. We have performed high-resolution two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) analysis of (solar simulated) UV-exposed reconstructed skin equivalents as well as native skin. Differentially expressed proteins were processed for mass spectrometric analysis, when consistent differences were observed in all individual human skin equivalents. In addition to proteins known to be involved in UV responses (HSP27, MnSOD, and PDX-2), we identified two novel proteins that were downregulated following UV exposure. Further analysis revealed that these proteins were the phosphorylated forms of the actin cytoskeleton modulators cofilin-1 and destrin. The de-phosphorylation of cofilin-1 was confirmed using western blotting of UV-exposed skin equivalents and ex vivo skin protein extracts. In conclusion, our study indicates the potency of a proteomic approach to study UV-induced changes in a tissue culture system mimicking human skin as well as excised human skin.

    The Journal of investigative dermatology 2005;124;4;818-24

  • LIM-kinase 2 and cofilin phosphorylation mediate actin cytoskeleton reorganization induced by transforming growth factor-beta.

    Vardouli L, Moustakas A and Stournaras C

    Department of Biochemistry, School of Medicine, University of Crete, GR-71110, Heraklion, Greece.

    Reorganization of the actin cytoskeleton in response to growth factor signaling, such as transforming growth factor beta (TGF-beta), controls cell adhesion, motility, and growth of diverse cell types. In Swiss3T3 fibroblasts, a widely used model for studies of actin reorganization, TGF-beta1 induced rapid actin polymerization into stress fibers and concomitantly activated RhoA and RhoB small GTPases. Consequently, dominant-negative RhoA and RhoB mutants blocked TGF-beta1-induced actin reorganization. Because Rho GTPases are known to regulate the activity of LIM-kinases (LIMK), we found that TGF-beta1 induced LIMK2 phosphorylation with similar kinetics to Rho activation. Cofilin and LIMK2 co-precipitated and cofilin became phosphorylated in response to TGF-beta1, whereas RNA interference against LIMK2 blocked formation of new stress fibers by TGF-beta1. Because the kinase ROCK1 links Rho GTPases to LIMK2, we found that inhibiting ROCK1 activity blocked completely TGF-beta1-induced LIMK2/cofilin phosphorylation and downstream stress fiber formation. We then tested whether the canonical TGF-beta receptor/Smad pathway mediates regulation of the above effectors and actin reorganization. Adenoviruses expressing constitutively activated TGF-beta type I receptor led to robust actin reorganization and Rho activation, whereas the constitutively activated TGF-beta type I receptor with mutated Smad docking sites (L45 loop) did not affect either actin organization or Rho activity. In line with this, ectopic expression of the inhibitory Smad7 inhibited TGF-beta1-induced Rho activation and cytoskeletal reorganization. Our data define a novel pathway emanating from the TGF-beta type I receptor and leading to regulation of actin assembly, via the kinase LIMK2.

    The Journal of biological chemistry 2005;280;12;11448-57

  • Interplay between components of a novel LIM kinase-slingshot phosphatase complex regulates cofilin.

    Soosairajah J, Maiti S, Wiggan O, Sarmiere P, Moussi N, Sarcevic B, Sampath R, Bamburg JR and Bernard O

    The Walter & Eliza Hall Institute of Medical Research, Victoria, Australia.

    Slingshot (SSH) phosphatases and LIM kinases (LIMK) regulate actin dynamics via a reversible phosphorylation (inactivation) of serine 3 in actin-depolymerizing factor (ADF) and cofilin. Here we demonstrate that a multi-protein complex consisting of SSH-1L, LIMK1, actin, and the scaffolding protein, 14-3-3zeta, is involved, along with the kinase, PAK4, in the regulation of ADF/cofilin activity. Endogenous LIMK1 and SSH-1L interact in vitro and co-localize in vivo, and this interaction results in dephosphorylation and downregulation of LIMK1 activity. We also show that the phosphatase activity of purified SSH-1L is F-actin dependent and is negatively regulated via phosphorylation by PAK4. 14-3-3zeta binds to phosphorylated slingshot, decreases the amount of slingshot that co-sediments with F-actin, but does not alter slingshot activity. Here we define a novel ADF/cofilin phosphoregulatory complex and suggest a new mechanism for the regulation of ADF/cofilin activity in mediating changes to the actin cytoskeleton.

    Funded by: NIGMS NIH HHS: GM35126, R01 GM035126; NINDS NIH HHS: NS40371

    The EMBO journal 2005;24;3;473-86

  • Cofilin activity during insulin-like growth factor I-stimulated neuroblastoma cell motility.

    Meyer G, Kim B, van Golen C and Feldman EL

    Department of Neurology, University of Michigan, 4414 Kresge III, 200 Zina Pitcher Place, Ann Arbor, MI 48109, USA.

    Insulin-like growth factor I (IGF-I) is a potent stimulator of neuroblastoma cell motility. Cell motility requires lamellipodium extension at the leading edge of the cell through organized actin polymerization, and IGF-I stimulates lamellipodial elaboration in human neuroblastoma cells. Rac is a Rho GTPase that stimulates lamellipodial formation via the regulation of actin polymerization. In this study, we show that IGF-I-stimulated phosphatidylinositol 3-kinase (PI-3K) activity promotes rac activation and subsequent activation of the down- stream effectors LIM kinase and cofilin. Overexpression of wild-type LIM kinase and wild-type Xenopus ADF/cofilin (XAC) suppresses IGF-I-stimulated motility in SH-SY5Y cells, while expression of dominant negative LIM kinase and constitutively active XAC increases SH-SY5Y motility in the absence of IGF-I stimulation. These results suggest that regulation by cofilin of actin depolymerization is important in the process of neuroblastoma cell motility, and IGF-I regulates cofilin activity in part through PI-3K, rac, and LIM kinase.

    Funded by: NINDS NIH HHS: NS 36778, NS 38849

    Cellular and molecular life sciences : CMLS 2005;62;4;461-70

  • Transducible heat shock protein 20 (HSP20) phosphopeptide alters cytoskeletal dynamics.

    Dreiza CM, Brophy CM, Komalavilas P, Furnish EJ, Joshi L, Pallero MA, Murphy-Ullrich JE, von Rechenberg M, Ho YS, Richardson B, Xu N, Zhen Y, Peltier JM and Panitch A

    The Biodesign Institute at Arizona State University, Tempe, Arizona, USA.

    Activation of cyclic nucleotide dependent signaling pathways leads to relaxation of smooth muscle, alterations in the cytoskeleton of cultured cells, and increases in the phosphorylation of HSP20. To determine the effects of phosphorylated HSP20 on the actin cytoskeleton, phosphopeptide analogs of HSP20 were synthesized. These peptides contained 1) the amino acid sequence surrounding the phosphorylation site of HSP20, 2) a phosphoserine, and 3) a protein transduction domain. Treatment of Swiss 3T3 cells with phosphopeptide analogs of HSP20 led to loss of actin stress fibers and focal adhesion complexes as demonstrated by immunocytochemistry, interference reflection microscopy, and biochemical quantitation of globular-actin. Treatment with phosphopeptide analogs of HSP20 also led to dephosphorylation of the actin depolymerizing protein cofilin. Pull-down assays demonstrated that 14-3-3 proteins associated with phosphopeptide analogs of HSP20 (but not peptide analogs in which the serine was not phosphorylated). The binding of 14-3-3 protein to phosphopeptide analogs of HSP20 prevented the association of cofilin with 14-3-3. These data suggest that HSP20 may modulate actin cytoskeletal dynamics by competing with the actin depolymerizing protein cofilin for binding to the scaffolding protein 14-3-3. Interestingly, the entire protein was not needed for this effect, suggesting that the association is modulated by phosphopeptide motifs of HSP20. These data also suggest the possibility that cyclic nucleotide dependent relaxation of smooth muscle may be mediated by a thin filament (actin) regulatory process. Finally, these data suggest that protein transduction can be used as a tool to elucidate the specific function of peptide motifs of proteins.

    Funded by: NHLBI NIH HHS: R01 HL58027

    FASEB journal : official publication of the Federation of American Societies for Experimental Biology 2005;19;2;261-3

  • Immunoaffinity profiling of tyrosine phosphorylation in cancer cells.

    Rush J, Moritz A, Lee KA, Guo A, Goss VL, Spek EJ, Zhang H, Zha XM, Polakiewicz RD and Comb MJ

    Cell Signaling Technology Inc., 166B Cummings Center, Beverly, Massachusetts 01915, USA.

    Tyrosine kinases play a prominent role in human cancer, yet the oncogenic signaling pathways driving cell proliferation and survival have been difficult to identify, in part because of the complexity of the pathways and in part because of low cellular levels of tyrosine phosphorylation. In general, global phosphoproteomic approaches reveal small numbers of peptides containing phosphotyrosine. We have developed a strategy that emphasizes the phosphotyrosine component of the phosphoproteome and identifies large numbers of tyrosine phosphorylation sites. Peptides containing phosphotyrosine are isolated directly from protease-digested cellular protein extracts with a phosphotyrosine-specific antibody and are identified by tandem mass spectrometry. Applying this approach to several cell systems, including cancer cell lines, shows it can be used to identify activated protein kinases and their phosphorylated substrates without prior knowledge of the signaling networks that are activated, a first step in profiling normal and oncogenic signaling networks.

    Funded by: NCI NIH HHS: 1R43CA101106

    Nature biotechnology 2005;23;1;94-101

  • Cofilin 1 is revealed as an inhibitor of glucocorticoid receptor by analysis of hormone-resistant cells.

    Rüegg J, Holsboer F, Turck C and Rein T

    Max Planck Institute of Psychiatry, Kraepelinstr. 10, D-80804 Munich, Germany.

    Significant knowledge about glucocorticoid signaling has accumulated, yet many aspects remain unknown. We aimed to discover novel factors involved in glucocorticoid receptor regulation that do not necessarily require direct receptor interaction. We achieved this by using a functional genetic screen: a stable cell line which cannot survive hormone treatment was engineered, randomly mutated, and selected in the presence of glucocorticoid. A hormone-resistant clone was analyzed by two-dimensional gel electrophoresis. Differentially expressed proteins were identified and tested as candidates for regulation of the glucocorticoid receptor. An unexpected candidate, cofilin 1, inhibited receptor activity. Cofilin is known to promote actin depolymerization and filament severing. Several experiments suggest that this feature of cofilin is involved in its inhibitory action. Both its actin depolymerization activity and its inhibitory action on the receptor are dependent on its phosphorylation state. Treatment of cells with a cytoskeleton-disrupting agent decreased receptor activity, as did overexpression of actin, particularly a mutant actin that does not polymerize. In addition, overexpression of cofilin and actin as well as chemical cytoskeleton disruption changed the subcellular receptor distribution and upregulated c-Jun, which could constitute the inhibitory mechanism of cofilin. In summary, cofilin represents a novel factor that can cause glucocorticoid resistance.

    Molecular and cellular biology 2004;24;21;9371-82

  • The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).

    Gerhard DS, Wagner L, Feingold EA, Shenmen CM, Grouse LH, Schuler G, Klein SL, Old S, Rasooly R, Good P, Guyer M, Peck AM, Derge JG, Lipman D, Collins FS, Jang W, Sherry S, Feolo M, Misquitta L, Lee E, Rotmistrovsky K, Greenhut SF, Schaefer CF, Buetow K, Bonner TI, Haussler D, Kent J, Kiekhaus M, Furey T, Brent M, Prange C, Schreiber K, Shapiro N, Bhat NK, Hopkins RF, Hsie F, Driscoll T, Soares MB, Casavant TL, Scheetz TE, Brown-stein MJ, Usdin TB, Toshiyuki S, Carninci P, Piao Y, Dudekula DB, Ko MS, Kawakami K, Suzuki Y, Sugano S, Gruber CE, Smith MR, Simmons B, Moore T, Waterman R, Johnson SL, Ruan Y, Wei CL, Mathavan S, Gunaratne PH, Wu J, Garcia AM, Hulyk SW, Fuh E, Yuan Y, Sneed A, Kowis C, Hodgson A, Muzny DM, McPherson J, Gibbs RA, Fahey J, Helton E, Ketteman M, Madan A, Rodrigues S, Sanchez A, Whiting M, Madari A, Young AC, Wetherby KD, Granite SJ, Kwong PN, Brinkley CP, Pearson RL, Bouffard GG, Blakesly RW, Green ED, Dickson MC, Rodriguez AC, Grimwood J, Schmutz J, Myers RM, Butterfield YS, Griffith M, Griffith OL, Krzywinski MI, Liao N, Morin R, Morrin R, Palmquist D, Petrescu AS, Skalska U, Smailus DE, Stott JM, Schnerch A, Schein JE, Jones SJ, Holt RA, Baross A, Marra MA, Clifton S, Makowski KA, Bosak S, Malek J and MGC Project Team

    The National Institutes of Health's Mammalian Gene Collection (MGC) project was designed to generate and sequence a publicly accessible cDNA resource containing a complete open reading frame (ORF) for every human and mouse gene. The project initially used a random strategy to select clones from a large number of cDNA libraries from diverse tissues. Candidate clones were chosen based on 5'-EST sequences, and then fully sequenced to high accuracy and analyzed by algorithms developed for this project. Currently, more than 11,000 human and 10,000 mouse genes are represented in MGC by at least one clone with a full ORF. The random selection approach is now reaching a saturation point, and a transition to protocols targeted at the missing transcripts is now required to complete the mouse and human collections. Comparison of the sequence of the MGC clones to reference genome sequences reveals that most cDNA clones are of very high sequence quality, although it is likely that some cDNAs may carry missense variants as a consequence of experimental artifact, such as PCR, cloning, or reverse transcriptase errors. Recently, a rat cDNA component was added to the project, and ongoing frog (Xenopus) and zebrafish (Danio) cDNA projects were expanded to take advantage of the high-throughput MGC pipeline.

    Funded by: PHS HHS: N01-C0-12400

    Genome research 2004;14;10B;2121-7

  • Backbone and sidechain 1H, 13C and 15N resonance assignments of human cofilin.

    Zierler-Gould KM, Pope BJ, Weeds AG and Ball LJ

    Journal of biomolecular NMR 2004;29;3;429-30

  • A pathway of neuregulin-induced activation of cofilin-phosphatase Slingshot and cofilin in lamellipodia.

    Nagata-Ohashi K, Ohta Y, Goto K, Chiba S, Mori R, Nishita M, Ohashi K, Kousaka K, Iwamatsu A, Niwa R, Uemura T and Mizuno K

    Dept. of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai, Miyagi 980-8578, Japan.

    Cofilin mediates lamellipodium extension and polarized cell migration by stimulating actin filament dynamics at the leading edge of migrating cells. Cofilin is inactivated by phosphorylation at Ser-3 and reactivated by cofilin-phosphatase Slingshot-1L (SSH1L). Little is known of signaling mechanisms of cofilin activation and how this activation is spatially regulated. Here, we show that cofilin-phosphatase activity of SSH1L increases approximately 10-fold by association with actin filaments, which indicates that actin assembly at the leading edge per se triggers local activation of SSH1L and thereby stimulates cofilin-mediated actin turnover in lamellipodia. We also provide evidence that 14-3-3 proteins inhibit SSH1L activity, dependent on the phosphorylation of Ser-937 and Ser-978 of SSH1L. Stimulation of cells with neuregulin-1beta induced Ser-978 dephosphorylation, translocation of SSH1L onto F-actin-rich lamellipodia, and cofilin dephosphorylation. These findings suggest that SSH1L is locally activated by translocation to and association with F-actin in lamellipodia in response to neuregulin-1beta and 14-3-3 proteins negatively regulate SSH1L activity by sequestering it in the cytoplasm.

    The Journal of cell biology 2004;165;4;465-71

  • The human plasma proteome: a nonredundant list developed by combination of four separate sources.

    Anderson NL, Polanski M, Pieper R, Gatlin T, Tirumalai RS, Conrads TP, Veenstra TD, Adkins JN, Pounds JG, Fagan R and Lobley A

    The Plasma Proteome Institute, Washington DC 20009-3450, USA. leighanderson@plasmaproteome.org

    We have merged four different views of the human plasma proteome, based on different methodologies, into a single nonredundant list of 1175 distinct gene products. The methodologies used were 1) literature search for proteins reported to occur in plasma or serum; 2) multidimensional chromatography of proteins followed by two-dimensional electrophoresis and mass spectroscopy (MS) identification of resolved proteins; 3) tryptic digestion and multidimensional chromatography of peptides followed by MS identification; and 4) tryptic digestion and multidimensional chromatography of peptides from low-molecular-mass plasma components followed by MS identification. Of 1,175 nonredundant gene products, 195 were included in more than one of the four input datasets. Only 46 appeared in all four. Predictions of signal sequence and transmembrane domain occurrence, as well as Genome Ontology annotation assignments, allowed characterization of the nonredundant list and comparison of the data sources. The "nonproteomic" literature (468 input proteins) is strongly biased toward signal sequence-containing extracellular proteins, while the three proteomics methods showed a much higher representation of cellular proteins, including nuclear, cytoplasmic, and kinesin complex proteins. Cytokines and protein hormones were almost completely absent from the proteomics data (presumably due to low abundance), while categories like DNA-binding proteins were almost entirely absent from the literature data (perhaps unexpected and therefore not sought). Most major categories of proteins in the human proteome are represented in plasma, with the distribution at successively deeper layers shifting from mostly extracellular to a distribution more like the whole (primarily cellular) proteome. The resulting nonredundant list confirms the presence of a number of interesting candidate marker proteins in plasma and serum.

    Molecular & cellular proteomics : MCP 2004;3;4;311-26

  • Screening of Hsp105alpha-binding proteins using yeast and bacterial two-hybrid systems.

    Saito Y, Doi K, Yamagishi N, Ishihara K and Hatayama T

    Department of Biochemistry, Kyoto Pharmaceutical University, 607-8414 Kyoto, Japan.

    Hsp105alpha is a 105-kDa stress protein, which is expressed constitutively at especially high levels in the brain compared with other tissues in mammals, and is also induced by a variety of stressors. Recently, we have shown that Hsp105alpha binds to alpha-tubulin and prevents the heat-induced disaggregation of microtubules. To further elucidate the function of Hsp105alpha, we searched for Hsp105alpha-binding proteins by screening a mouse FM3A cell library and human and mouse brain cDNA libraries using the yeast and bacterial two-hybrid systems. We showed here that Hsp105alpha interacted with several cellular proteins, such as cofilin, dynein light chain 2A, alpha-adducin, ubiquitin activating enzyme E1, phosphoglycerate kinase 1, and platelet-activating factor acethylhydrolase alpha1-subunit. The interaction was validated by the results of a pull-down assay and indirect immunofluorescence analysis. The significance of Hsp105alpha and Hsp105alpha-binding proteins in cells was discussed.

    Biochemical and biophysical research communications 2004;314;2;396-402

  • Solution structure of human cofilin: actin binding, pH sensitivity, and relationship to actin-depolymerizing factor.

    Pope BJ, Zierler-Gould KM, Kühne R, Weeds AG and Ball LJ

    Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom.

    Human actin-depolymerizing factor (ADF) and cofilin are pH-sensitive, actin-depolymerizing proteins. Although 72% identical in sequence, ADF has a much higher depolymerizing activity than cofilin at pH 8. To understand this, we solved the structure of human cofilin using nuclear magnetic resonance and compared it with human ADF. Important sequence differences between vertebrate ADF/cofilins were correlated with unique structural determinants in the F-actin-binding site to account for differences in biochemical activities of the two proteins. Cofilin has a short beta-strand at the C terminus, not found in ADF, which packs against strands beta3/beta4, changing the environment around Lys96, a residue essential for F-actin binding. A salt bridge involving His133 and Asp98 (Glu98 in ADF) may explain the pH sensitivity of human cofilin and ADF; these two residues are fully conserved in vertebrate ADF/cofilins. Chemical shift perturbations identified residues that (i) differ in their chemical environments between wild type cofilin and mutants S3D, which has greatly reduced G-actin binding, and K96Q, which does not bind F-actin; (ii) are affected when G-actin binds cofilin; and (iii) are affected by pH change from 6 to 8. Many residues affected by G-actin binding also show perturbation in the mutants or in response to pH. Our evidence suggests the involvement of residues 133-138 of strand beta5 in all of the activities examined. Because residues in beta5 are perturbed by mutations that affect both G-actin and F-actin binding, this strand forms a "boundary" or "bridge" between the proposed F- and G-actin-binding sites.

    The Journal of biological chemistry 2004;279;6;4840-8

  • Roles of TRP14, a thioredoxin-related protein in tumor necrosis factor-alpha signaling pathways.

    Jeong W, Chang TS, Boja ES, Fales HM and Rhee SG

    Laboratory of Cell Signaling, National Heart, Lung and Bllod Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.

    The possible roles of a 14-kDa human thioredoxin (Trx)-related protein (TRP14) in TNF-alpha signaling were studied in comparison with those of Trx1 by RNA interference in HeLa cells. Depletion of TRP14 augmented the TNF-alpha-induced phosphorylation and degradation of I kappa B alpha as well as the consequent activation of NF-kappa B to a greater extent than did Trx1 depletion. Deficiency of TRP14 or Trx1 enhanced TNF-alpha-induced activation of caspases and subsequent apoptosis by a similar extent. The TNF-alpha-induced activation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (MAPKs), however, was promoted by depletion of TRP14 but not by that of Trx1. Unlike Trx1, TRP14 neither associated with nor inhibited the kinase activity of apoptosis signal-regulating kinase-1 (ASK1), an upstream activator of JNK and p38. In combination with the results in the accompanying paper that TRP14 did not reduce the known substrates of Trx1, these results suggest that TRP14 modulates TNF-alpha signaling pathways, provably by interacting with proteins distinct from the targets of Trx1. In an effort to identify target proteins of TRP14, a mutant of TRP14, in which the active site cysteine (Cys(46)) was substituted with serine, was shown to form a disulfide-linked complex with LC8 cytoplasmic dynein light chain. The complex was detected in HeLa cells treated with H(2)O(2) or TNF-alpha but not in untreated cells, suggesting that LC8 cytoplasmic dynein light chain is a possible substrate of TRP14.

    The Journal of biological chemistry 2004;279;5;3151-9

  • 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

  • Mitochondrial translocation of cofilin is an early step in apoptosis induction.

    Chua BT, Volbracht C, Tan KO, Li R, Yu VC and Li P

    Laboratory of Apoptosis Regulation, Institute of Molecular and Cell Biology, National Institute of Singapore, 30 Medical Drive, 117609, Singapore.

    Increasing evidence suggests that movement of key proteins in or out of mitochondria during apoptosis is essential for the regulation of apoptosis. Here, we report identification of the actin-binding protein cofilin by a proteomic approach, as such a factor translocated from cytosol into mitochondria after induction of apoptosis. We found that after induction of apoptosis, cofilin was translocated to mitochondria before release of cytochrome c. Reduction of cofilin protein levels with small-interfering RNA (siRNA) resulted in inhibition of both cytochrome c release and apoptosis. Only dephosphorylated cofilin was translocated to mitochondria, and the cofilin S3D mutant, which mimicks the phosphorylated form, suppressed mitochondrial translocation and apoptosis. Translocation was achieved through exposure of an amino-terminal mitochondrial targeting signal in combination with carboxy-terminal sequences. When correctly targeted to mitochondria, cofilin induced massive apoptosis. The apoptosis-inducing ability of cofilin, but not its mitochondrial localization, was dependent on the functional actin-binding domain. Thus, domains involved in mitochondrial targeting and actin binding are indispensable for its pro-apoptotic function. Our data suggest that cofilin has an important function during the initiation phase of apoptosis.

    Nature cell biology 2003;5;12;1083-9

  • Cofilin interacts with ClC-5 and regulates albumin uptake in proximal tubule cell lines.

    Hryciw DH, Wang Y, Devuyst O, Pollock CA, Poronnik P and Guggino WB

    Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA

    Receptor-mediated endocytosis is a constitutive high capacity pathway for the reabsorption of proteins from the glomerular filtrate by the renal proximal tubule. ClC-5 is a voltage-gated chloride channel found in the proximal tubule where it has been shown to be essential for protein uptake, based on evidence from patients with Dent's disease and studies in ClC-5 knockout mice. To further delineate the role of ClC-5 in albumin uptake, we performed a yeast two-hybrid screen with the C-terminal tail of ClC-5 to identify any interactions of the channel with proteins involved in endocytosis. We found that the C-terminal tail of ClC-5 bound the actin depolymerizing protein, cofilin, a result that was confirmed by GST-fusion pulldown assays. In cultured proximal tubule cells, cofilin was distributed in nuclear, cytoplasmic, and microsomal fractions and co-localized with ClC-5. Phosphorylation of cofilin by overexpressing LIM kinase 1 resulted in a stabilization of the actin cytoskeleton. Phosphorylation of cofilin in two proximal tubule cell models (porcine renal proximal tubule and opossum kidney) was also accompanied by a pronounced inhibition of albumin uptake. This study identifies a novel interaction between the C-terminal tail of ClC-5 and cofilin, an actin-associated protein that is crucial in the regulation of albumin uptake by the proximal tubule.

    Funded by: NHLBI NIH HHS: HL47122; NIDDK NIH HHS: DK32753

    The Journal of biological chemistry 2003;278;41;40169-76

  • Direct signaling by the BMP type II receptor via the cytoskeletal regulator LIMK1.

    Foletta VC, Lim MA, Soosairajah J, Kelly AP, Stanley EG, Shannon M, He W, Das S, Massague J, Bernard O and Soosairaiah J

    The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade Parkville, Victoria 3050, Australia.

    Bone morphogenetic proteins (BMPs) regulate multiple cellular processes, including cell differentiation and migration. Their signals are transduced by the kinase receptors BMPR-I and BMPR-II, leading to Smad transcription factor activation via BMPR-I. LIM kinase (LIMK) 1 is a key regulator of actin dynamics as it phosphorylates and inactivates cofilin, an actin depolymerizing factor. During a search for LIMK1-interacting proteins, we isolated clones encompassing the tail region of BMPR-II. Although the BMPR-II tail is not involved in BMP signaling via Smad proteins, mutations truncating this domain are present in patients with primary pulmonary hypertension (PPH). Further analysis revealed that the interaction between LIMK1 and BMPR-II inhibited LIMK1's ability to phosphorylate cofilin, which could then be alleviated by addition of BMP4. A BMPR-II mutant containing the smallest COOH-terminal truncation described in PPH failed to bind or inhibit LIMK1. This study identifies the first function of the BMPR-II tail domain and suggests that the deregulation of actin dynamics may contribute to the etiology of PPH.

    Funded by: NCI NIH HHS: CA34610, R01 CA034610, R37 CA034610

    The Journal of cell biology 2003;162;6;1089-98

  • Cofilin phosphorylation and actin polymerization by NRK/NESK, a member of the germinal center kinase family.

    Nakano K, Kanai-Azuma M, Kanai Y, Moriyama K, Yazaki K, Hayashi Y and Kitamura N

    Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.

    Nck-interacting kinase (NIK)-related kinase (NRK)/NIK-like embryo-specific kinase (NESK) is a protein kinase that belongs to the germinal center kinase family, and activates the c-Jun N-terminal kinase (JNK) signaling pathway. In this study, we examined the effect of NRK/NESK on actin cytoskeletal organization. Overexpression of NRK/NESK in COS7 cells induced accumulation of polymerized actin at the perinuclear. Phosphorylation of cofilin, an actin-depolymerizing factor, was increased in NRK/NESK-expressing HEK 293T cells. In addition, in vitro phosphorylation of cofilin was observed on NRK/NESK immunoprecipitates from HEK 293T cells expressing the kinase domain of NRK/NESK. The cofilin phosphorylation occurred at the serine residue of position 3 (Ser-3). Since the phosphorylation at Ser-3 inactivates the actin-depolymerizing activity of cofilin, these results suggest that NRK/NESK induces actin polymerization through cofilin phosphorylation. The cofilin phosphorylation did not appear to be mediated through activation of LIM-kinasel, a cofilin-phosphorylating kinase, or through the activation of JNK. Thus, cofilin is likely to be a direct substrate of NRK/NESK. NRK/NESK is predominantly expressed in skeletal muscle during the late stages of mouse embryogenesis. Thus, NRK/NESK may be involved in the regulation of actin cytoskeletal organization in skeletal muscle cells through cofilin phosphorylation.

    Experimental cell research 2003;287;2;219-27

  • Exploring proteomes and analyzing protein processing by mass spectrometric identification of sorted N-terminal peptides.

    Gevaert K, Goethals M, Martens L, Van Damme J, Staes A, Thomas GR and Vandekerckhove J

    Department of Medical Protein Research, Flanders Interuniversity Institute for Biotechnology, Ghent University, A. Baertsoenkaai 3, B-9000 Ghent, Belgium. kris.gevaert@rug.ac.be

    Current non-gel techniques for analyzing proteomes rely heavily on mass spectrometric analysis of enzymatically digested protein mixtures. Prior to analysis, a highly complex peptide mixture is either separated on a multidimensional chromatographic system or it is first reduced in complexity by isolating sets of representative peptides. Recently, we developed a peptide isolation procedure based on diagonal electrophoresis and diagonal chromatography. We call it combined fractional diagonal chromatography (COFRADIC). In previous experiments, we used COFRADIC to identify more than 800 Escherichia coli proteins by tandem mass spectrometric (MS/MS) analysis of isolated methionine-containing peptides. Here, we describe a diagonal method to isolate N-terminal peptides. This reduces the complexity of the peptide sample, because each protein has one N terminus and is thus represented by only one peptide. In this new procedure, free amino groups in proteins are first blocked by acetylation and then digested with trypsin. After reverse-phase (RP) chromatographic fractionation of the generated peptide mixture, internal peptides are blocked using 2,4,6-trinitrobenzenesulfonic acid (TNBS); they display a strong hydrophobic shift and therefore segregate from the unaltered N-terminal peptides during a second identical separation step. N-terminal peptides can thereby be specifically collected for further liquid chromatography (LC)-MS/MS analysis. Omitting the acetylation step results in the isolation of non-lysine-containing N-terminal peptides from in vivo blocked proteins.

    Nature biotechnology 2003;21;5;566-9

  • Control of growth cone motility and morphology by LIM kinase and Slingshot via phosphorylation and dephosphorylation of cofilin.

    Endo M, Ohashi K, Sasaki Y, Goshima Y, Niwa R, Uemura T and Mizuno K

    Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan.

    Growth cone motility and morphology are based on actin-filament dynamics. Cofilin plays an essential role for the rapid turnover of actin filaments by severing and depolymerizing them. The activity of cofilin is repressed by phosphorylation at Ser3 by LIM kinase (LIMK, in which LIM is an acronym of the three gene products Lin-11, Isl-1, and Mec-3) and is reactivated by dephosphorylation by phosphatases, termed Slingshot (SSH). We investigated the roles of cofilin, LIMK, and SSH in the growth cone motility and morphology and neurite extension by expressing fluorescence protein-labeled cofilin, LIMK1, SSH1, or their mutants in chick dorsal root ganglion (DRG) neurons and then monitoring live images of growth cones by time-lapse video fluorescence microscopy. The expression of LIMK1 remarkably repressed growth cone motility and neurite extension, whereas the expression of SSH1 or a nonphosphorylatable S3A mutant of cofilin enhanced these events. The fan-like shape of growth cones was disorganized by the expression of any of these proteins. The repressive effects on growth cone behavior by LIMK1 expression were significantly rescued by the coexpression of S3A-cofilin or SSH1. These findings suggest that LIMK1 and SSH1 play critical roles in controlling growth cone motility and morphology and neurite extension by regulating the activity of cofilin and may be involved in signaling pathways that regulate stimulus-induced growth cone guidance. Using various mutants of cofilin, we also obtained evidence that the actin-filament-severing activity of cofilin is critical for growth cone motility and neurite extension.

    The Journal of neuroscience : the official journal of the Society for Neuroscience 2003;23;7;2527-37

  • Identification of cofilin and LIM-domain-containing protein kinase 1 as novel interaction partners of 14-3-3 zeta.

    Birkenfeld J, Betz H and Roth D

    Department of Neurochemistry, Max-Planck-Institute for Brain Research, Deutschordenstrasse 46, 60528 Frankfurt, Germany.

    Proteins of the 14-3-3 family have been implicated in various physiological processes, and are thought to function as adaptors in various signal transduction pathways. In addition, 14-3-3 proteins may contribute to the reorganization of the actin cytoskeleton by interacting with as yet unidentified actin-binding proteins. Here we show that the 14-3-3 zeta isoform interacts with both the actin-depolymerizing factor cofilin and its regulatory kinase, LIM (Lin-11/Isl-1/Mec-3)-domain-containing protein kinase 1 (LIMK1). In both yeast two-hybrid assays and glutathione S-transferase pull-down experiments, these proteins bound efficiently to 14-3-3 zeta. Deletion analysis revealed consensus 14-3-3 binding sites on both cofilin and LIMK1. Furthermore, the C-terminal region of 14-3-3 zeta inhibited the binding of cofilin to actin in co-sedimentation experiments. Upon co-transfection into COS-7 cells, 14-3-3 zeta-specific immunoreactivity was redistributed into characteristic LIMK1-induced actin aggregations. Our data are consistent with 14-3-3-protein-induced changes to the actin cytoskeleton resulting from interactions with cofilin and/or LIMK1.

    The Biochemical journal 2003;369;Pt 1;45-54

  • Interaction of cofilin with the serine phosphatases PP1 and PP2A in normal and neoplastic human T lymphocytes.

    Samstag Y and Nebl G

    Institute for Immunology, Ruprecht-Karls-University, Im Neuenheimer Feld 305, D-69120, Heidelberg, Germany. o69@ix.urz.uni-heidelberg.de

    Advances in enzyme regulation 2003;43;197-211

  • Interaction of cofilin with triose-phosphate isomerase contributes glycolytic fuel for Na,K-ATPase via Rho-mediated signaling pathway.

    Jung J, Yoon T, Choi EC and Lee K

    College of Pharmacy, Center for Cell Signaling Research and Division of Molecular Life Sciences, Ewha Woman's University, Seoul 120-750, Korea.

    We reported previously that cofilin, an actin-binding protein, interacts with Na,K-ATPase and enhances its activity (Lee, K., Jung, J., Kim, M., and Guidotti, G. (2001) Biochem. J. 353, 377-385). To understand the nature of this interaction and the role of cofilin in the regulation of Na,K-ATPase activity, we searched for cofilin-binding proteins in the rat skeletal muscle cDNA library using the yeast two-hybrid system. Several cDNA clones were isolated, some of which coded for triose-phosphate isomerase, a glycolytic enzyme. The interaction of cofilin with triose-phosphate isomerase as well as Na,K-ATPase was confirmed by immunoprecipitation and confocal microscopy in HeLa cells. Cofilin was translocated to the plasma membrane along with triose-phosphate isomerase by the Rho activator lysophosphatidic acid but not by the p160 Rho-associated kinase inhibitor Y-27632, suggesting that the phosphorylated form of cofilin bound to TPI interacts with Na,K-ATPase. Ouabain-sensitive (86)Rb(+) uptake showed that Na,K-ATPase activity was increased by the overexpression of cofilin and lysophosphatidic acid treatment, but not by the overexpression of mutant cofilin S3A and Y-27632 treatment. Pretreatment with the glycolytic inhibitor iodoacetic acid caused a remarkable reduction of Na,K-ATPase activity, whereas pretreatment with the oxidative inhibitor carbonyl cyanide m-chlorophenylhydrazone caused no detectable changes, suggesting that the phosphorylated cofilin is involved in feeding glycolytic fuel for Na,K-ATPase activity. These findings provide a novel molecular mechanism for the regulation of Na,K-ATPase activity and for the nature of the functional coupling of cellular energy transduction.

    The Journal of biological chemistry 2002;277;50;48931-7

  • Structural conservation between the actin monomer-binding sites of twinfilin and actin-depolymerizing factor (ADF)/cofilin.

    Paavilainen VO, Merckel MC, Falck S, Ojala PJ, Pohl E, Wilmanns M and Lappalainen P

    Program in Cellular Biotechnology, Institute of Biotechnology, P.O. Box 56, University of Helsinki, 00014 Helsinki, Finland.

    Twinfilin is an evolutionarily conserved actin monomer-binding protein that regulates cytoskeletal dynamics in organisms from yeast to mammals. It is composed of two actin-depolymerization factor homology (ADF-H) domains that show approximately 20% sequence identity to ADF/cofilin proteins. In contrast to ADF/cofilins, which bind both G-actin and F-actin and promote filament depolymerization, twinfilin interacts only with G-actin. To elucidate the molecular mechanisms of twinfilin-actin monomer interaction, we determined the crystal structure of the N-terminal ADF-H domain of twinfilin and mapped its actin-binding site by site-directed mutagenesis. This domain has similar overall structure to ADF/cofilins, and the regions important for actin monomer binding in ADF/cofilins are especially well conserved in twinfilin. Mutagenesis studies show that the N-terminal ADF-H domain of twinfilin and ADF/cofilins also interact with actin monomers through similar interfaces, although the binding surface is slightly extended in twinfilin. In contrast, the regions important for actin-filament interactions in ADF/cofilins are structurally different in twinfilin. This explains the differences in actin-interactions (monomer versus filament binding) between twinfilin and ADF/cofilins. Taken together, our data show that the ADF-H domain is a structurally conserved actin-binding motif and that relatively small structural differences at the actin interfaces of this domain are responsible for the functional variation between the different classes of ADF-H domain proteins.

    The Journal of biological chemistry 2002;277;45;43089-95

  • 14-3-3 regulates actin dynamics by stabilizing phosphorylated cofilin.

    Gohla A and Bokoch GM

    Department of Immunology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.

    The functionality of the actin cytoskeleton depends on a dynamic equilibrium between filamentous and monomeric actin. Proteins of the ADF/cofilin family are essential for the high rates of actin filament turnover observed in motile cells through regulation of actin polymerization/depolymerization cycles. Rho GTPases act through p21-activated kinase-1 (Pak-1) and Rho kinase to inhibit cofilin activity via the LIM kinase (LIMK)-mediated phosphorylation of cofilin on Ser3. We report the identification of 14-3-3zeta as a novel phosphocofilin binding protein involved in the maintenance of the cellular phosphocofilin pool. A Ser3 phosphocofilin binding protein was purified from bovine brain and was identified as 14-3-3zeta by mass spectrometry. The phosphorylation-dependent interaction between cofilin and 14-3-3zeta was confirmed in pulldown and coimmunoprecipitation experiments. Both Ser3 phosphorylation and a 14-3-3 recognition motif in cofilin are necessary for 14-3-3 binding. The expression of 14-3-3zeta increases phosphocofilin levels, and the coexpression of 14-3-3zeta with LIMK further elevates phosphocofilin levels and potentiates LIMK-dependent effects on the actin cytoskeleton. This potentiation of cofilin action appears to be a result of the protection of phosphocofilin from phosphatase-mediated dephosphorylation at Ser3 by bound 14-3-3zeta. Taken together, these results suggest that 14-3-3zeta proteins may play a dynamic role in the regulation of cellular actin structures through the maintenance of phosphocofilin levels.

    Funded by: NIGMS NIH HHS: GM39434

    Current biology : CB 2002;12;19;1704-10

  • Mitosis-specific activation of LIM motif-containing protein kinase and roles of cofilin phosphorylation and dephosphorylation in mitosis.

    Amano T, Kaji N, Ohashi K and Mizuno K

    Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miagi 980-8578, Japan.

    Actin filament dynamics play a critical role in mitosis and cytokinesis. LIM motif-containing protein kinase 1 (LIMK1) regulates actin reorganization by phosphorylating and inactivating cofilin, an actin-depolymerizing and -severing protein. To examine the role of LIMK1 and cofilin during the cell cycle, we measured cell cycle-associated changes in the kinase activity of LIMK1 and in the level of cofilin phosphorylation. Using synchronized HeLa cells, we found that LIMK1 became hyperphosphorylated and activated in prometaphase and metaphase, then gradually returned to the basal level as cells entered into telophase and cytokinesis. Although Rho-associated kinase and p21-activated protein kinase phosphorylate and activate LIMK1, they are not likely to be involved in mitosis-specific activation and phosphorylation of LIMK1. Immunoblot and immunofluorescence analyses using an anti-phosphocofilin-specific antibody revealed that the level of cofilin phosphorylation, similar to levels of LIMK1 activity, increased during prometaphase and metaphase then gradually declined in telophase and cytokinesis. Ectopic expression of LIMK1 increased the level of cofilin phosphorylation throughout the cell cycle and induced the formation of multinucleate cells. These results suggest that LIMK1 is involved principally in control of mitosis-specific cofilin phosphorylation and that dephosphorylation and reactivation of cofilin at later stages of mitosis play a critical role in cytokinesis of mammalian cells.

    The Journal of biological chemistry 2002;277;24;22093-102

  • Human CAP1 is a key factor in the recycling of cofilin and actin for rapid actin turnover.

    Moriyama K and Yahara I

    Department of Cell Biology, The Tokyo Metropolitan Institute of Medical Science, Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan. moriyama@rinshoken.or.jp

    Cofilin-ADF (actin-depolymerizing factor) is an essential driver of actin-based motility. We discovered two proteins, p65 and p55, that are components of the actin-cofilin complex in a human HEK293 cell extract and identified p55 as CAP1/ASP56, a human homologue of yeast CAP/SRV2 (cyclase-associated protein). CAP is a bifunctional protein with an N-terminal domain that binds to Ras-responsive adenylyl cyclase and a C-terminal domain that inhibits actin polymerization. Surprisingly, we found that the N-terminal domain of CAP1, but not the C-terminal domain, is responsible for the interaction with the actin-cofilin complex. The N-terminal domain of CAP1 was also found to accelerate the depolymerization of F-actin at the pointed end, which was further enhanced in the presence of cofilin and/or the C-terminal domain of CAP1. Moreover, CAP1 and its C-terminal domain were observed to facilitate filament elongation at the barbed end and to stimulate ADP-ATP exchange on G-actin, a process that regenerates easily polymerizable G-actin. Although cofilin inhibited the nucleotide exchange on G-actin even in the presence of the C-terminal domain of CAP1, its N-terminal domain relieved this inhibition. Thus, CAP1 plays a key role in speeding up the turnover of actin filaments by effectively recycling cofilin and actin and through its effect on both ends of actin filament.

    Journal of cell science 2002;115;Pt 8;1591-601

  • Control of actin reorganization by Slingshot, a family of phosphatases that dephosphorylate ADF/cofilin.

    Niwa R, Nagata-Ohashi K, Takeichi M, Mizuno K and Uemura T

    Department of Molecular Genetics, The Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan.

    The ADF (actin-depolymerizing factor)/cofilin family is a stimulus-responsive mediator of actin dynamics. In contrast to the mechanisms of inactivation of ADF/cofilin by kinases such as LIM-kinase 1 (LIMK1), much less is known about its reactivation through dephosphorylation. Here we report Slingshot (SSH), a family of phosphatases that have the property of F actin binding. In Drosophila, loss of ssh function dramatically increased levels of both F actin and phospho-cofilin (P cofilin) and disorganized epidermal cell morphogenesis. In mammalian cells, human SSH homologs (hSSHs) suppressed LIMK1-induced actin reorganization. Furthermore, SSH and the hSSHs dephosphorylated P cofilin in cultured cells and in cell-free assays. Our results strongly suggest that the SSH family plays a pivotal role in actin dynamics by reactivating ADF/cofilin in vivo.

    Cell 2002;108;2;233-46

  • Determining the differences in actin binding by human ADF and cofilin.

    Yeoh S, Pope B, Mannherz HG and Weeds A

    MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, UK.

    The actin-depolymerizing factor (ADF)/cofilin family of proteins play an essential role in actin dynamics and cytoskeletal re-organization. Human tissues express two isoforms in the same cells, ADF and cofilin, and these two proteins are more than 70% identical in amino acid sequence. We show that ADF is a much more potent actin-depolymerizing agent than cofilin: the maximum level of depolymerization at pH 8 by ADF is about 20 microM compared to 5 microM for cofilin, but little depolymerization occurs at pH 6.5 with either protein. However, we find little difference between the two proteins in their binding to filaments, their severing activities or their activation of subunit release from the pointed ends of filaments. Likewise, they show no significant differences in their affinities for monomeric actin: both bind 15-fold more tightly to actin.ADP than to actin.ATP. Complexes between actin.ADP and ADF or cofilin associate with both barbed and pointed ends of filaments at similar rates (close to those of actin.ATP and much higher than those of actin.ADP). This explains why high concentrations of both proteins reverse the activation of subunit release at pointed ends. The major difference between the two proteins is that the nucleating activity of cofilin-actin.ADP complexes is twice that of ADF-actin.ADP complexes and this, in turn, is twice that of actin.ATP alone. It is this weaker nucleating potential of ADF-actin.ADP that accounts for the much higher steady-state depolymerizing activity. The pH-sensitivity is due to the nucleating activity of complexes being greater at pH 6.5 than at pH 8. Sequence analysis of mammalian and avian isoforms shows a consistent pattern of charge differences in regions of the protein associated with F-actin-binding that may account for the differences in activity between ADF and cofilin.

    Journal of molecular biology 2002;315;4;911-25

  • The ADF/cofilin family: actin-remodeling proteins.

    Maciver SK and Hussey PJ

    Genes and Development Interdisciplinary Group, Department of Biomedical Sciences, University of Edinburgh, George Square, Edinburgh EH8 9XD, Scotland, UK. SKM@srv4.med.ed.ac.uk

    The ADF/cofilins are a family of actin-binding proteins expressed in all eukaryotic cells so far examined. Members of this family remodel the actin cytoskeleton, for example during cytokinesis, when the actin-rich contractile ring shrinks as it contracts through the interaction of ADF/cofilins with both monomeric and filamentous actin. The depolymerizing activity is twofold: ADF/cofilins sever actin filaments and also increase the rate at which monomers leave the filament's pointed end. The three-dimensional structure of ADF/cofilins is similar to a fold in members of the gelsolin family of actin-binding proteins in which this fold is typically repeated three or six times; although both families bind polyphosphoinositide lipids and actin in a pH-dependent manner, they share no obvious sequence similarity. Plants and animals have multiple ADF/cofilin genes, belonging in vertebrates to two types, ADF and cofilins. Other eukaryotes (such as yeast, Acanthamoeba and slime moulds) have a single ADF/cofilin gene. Phylogenetic analysis of the ADF/cofilins reveals that, with few exceptions, their relationships reflect conventional views of the relationships between the major groups of organisms.

    Genome biology 2002;3;5;reviews3007

  • Identification of yeast cofilin residues specific for actin monomer and PIP2 binding.

    Ojala PJ, Paavilainen V and Lappalainen P

    Program in Cellular Biotechnology, Institute of Biotechnology, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland.

    Cofilin/ADF is a ubiquitous actin-binding protein that is important for rapid actin dynamics in vivo. The long alpha-helix (helix 3 in yeast cofilin) forms the most highly conserved region in cofilin/ADF proteins, and residues in the NH2-terminal half of this alpha-helix have been shown to be essential for actin binding in cofilin/ADF. Recent studies also suggested that the basic residues in the COOH-terminal half of this alpha-helix would play an important role in F-actin binding. In contrast to these studies, we show here that the charged residues in the COOH-terminal half of helix 3 are not important for actin filament binding in yeast cofilin. Mutations in these residues, however, result in a small defect in actin monomer interactions. We also show that yeast cofilin can differentiate between various phosphatidylinositides, and mapped the PI(4,5)P2 binding site by using a collection of cofilin mutants. The PI(4,5)P2 binding site of yeast cofilin is a large positively charged surface that consists of residues in helix 3 as well as residues in other parts of the cofilin molecule. This suggests that cofilin/ADF proteins probably interact simultaneously with more than one PI(4,5)P2 molecule. The PI(4,5)P2-binding site overlaps with areas that are important for F-actin binding, explaining why the actin-related activities of cofilin/ADF are inhibited by PI(4,5)P2. The biological roles of actin and PI(4,5)P2 interactions of cofilin are discussed in light of phenotypes of specific yeast strains carrying mutations in residues that are important for actin and PI(4,5)P2 binding.

    Biochemistry 2001;40;51;15562-9

  • Interaction of ADP-ribosylated actin with actin binding proteins.

    Ballweber E, Galla M, Aktories K, Yeoh S, Weeds AG and Mannherz HG

    Department of Anatomy and Cell Biology, Ruhr-University, Universitätsstrasse 150, D-44780 Bochum, Germany.

    Actin ADP-ribosylated at Arg177 was previously shown not to polymerise after increasing the ionic strength, but to cap the barbed ends of filaments. Here we confirm that the polymerisation of ADP-ribosylated actin is inhibited, however, under specific conditions the modified actin copolymerises with native actin, indicating that its ability to take part in normal subunit interactions within filaments is not fully eliminated. We also show that ADP-ribosylated actin forms antiparallel but not parallel dimers: the former are not able to form filaments. ADP-ribosylated actin interacts with deoxyribonuclease I, vitamin D binding protein, thymosin beta(4), cofilin and gelsolin segment 1 like native actin. Interaction with myosin subfragment 1 revealed that the potential of the modified actin to aggregate into oligomers or short filaments is not fully eliminated.

    FEBS letters 2001;508;1;131-5

  • Cofilin phosphorylation and actin reorganization activities of testicular protein kinase 2 and its predominant expression in testicular Sertoli cells.

    Toshima J, Toshima JY, Takeuchi K, Mori R and Mizuno K

    Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan.

    We previously identified testicular protein kinase 1 (TESK1), which phosphorylates cofilin and induces actin cytoskeletal reorganization. We now report identification and characterization of another member of a TESK family, testicular protein kinase 2 (TESK2), with 48% amino acid identity with TESK1. Like TESK1, TESK2 phosphorylated cofilin specifically at Ser-3 and induced formation of actin stress fibers and focal adhesions. Both TESK1 and TESK2 are highly expressed in the testis, but in contrast to TESK1, which is predominantly expressed in testicular germ cells, TESK2 is expressed predominantly in nongerminal Sertoli cells. Thus, TESK1 and TESK2 seem to play distinct roles in spermatogenesis. In HeLa cells, TESK1 was localized mainly in the cytoplasm, whereas TESK2 was localized mainly in the nucleus, which means that TESK1 and TESK2 likely have distinct cellular functions. Because the kinase-inactive mutant of TESK2 was localized in the cytoplasm, nuclear/cytoplasmic localization of TESK2 depends on its kinase activity. A TESK2 mutant lacking the C-terminal noncatalytic region had about a 10-fold higher kinase activity in vitro and, when expressed in HeLa cells, induced punctate actin aggregates in the cytoplasm and unusual condensation and fragmentation of nuclei, followed by apoptosis. Thus, we propose that the C-terminal region plays important roles in regulating the kinase activity and cellular functions of TESK2.

    The Journal of biological chemistry 2001;276;33;31449-58

  • Activation of LIM kinases by myotonic dystrophy kinase-related Cdc42-binding kinase alpha.

    Sumi T, Matsumoto K, Shibuya A and Nakamura T

    Division of Molecular Regenerative Medicine, Course of Advanced Medicine, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.

    LIM kinases (LIMK1 and LIMK2) regulate actin cytoskeletal reorganization through cofilin phosphorylation downstream of distinct Rho family GTPases. Pak1 and ROCK, respectively, activate LIMK1 and LIMK2 downstream of Rac and Rho; however, an effector protein kinase for LIMKs downstream of Cdc42 remains to be defined. We now report evidence that LIMK1 and LIMK2 activities toward cofilin phosphorylation are stimulated in cells by the co-expression of myotonic dystrophy kinase-related Cdc42-binding kinase alpha (MRCKalpha), an effector protein kinase of Cdc42. In vitro, MRCKalpha phosphorylated the protein kinase domain of LIM kinases, and the site in LIMK2 phosphorylated by MRCKalpha proved to be threonine 505 within the activation segment. Expression of MRCKalpha induced phosphorylation of actin depolymerizing factor (ADF)/cofilin in cells, whereas MRCKalpha-induced ADF/cofilin phosphorylation was inhibited by the co-expression with the protein kinase-deficient form of LIM kinases. These results indicate that MRCKalpha phosphorylates and activates LIM kinases downstream of Cdc42, which in turn regulates the actin cytoskeletal reorganization through the phosphorylation and inactivation of ADF/cofilin.

    The Journal of biological chemistry 2001;276;25;23092-6

  • Cofilin phosphorylation by protein kinase testicular protein kinase 1 and its role in integrin-mediated actin reorganization and focal adhesion formation.

    Toshima J, Toshima JY, Amano T, Yang N, Narumiya S and Mizuno K

    Biological Institute, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.

    Testicular protein kinase 1 (TESK1) is a serine/threonine kinase with a structure composed of a kinase domain related to those of LIM-kinases and a unique C-terminal proline-rich domain. Like LIM-kinases, TESK1 phosphorylated cofilin specifically at Ser-3, both in vitro and in vivo. When expressed in HeLa cells, TESK1 stimulated the formation of actin stress fibers and focal adhesions. In contrast to LIM-kinases, the kinase activity of TESK1 was not enhanced by Rho-associated kinase (ROCK) or p21-activated kinase, indicating that TESK1 is not their downstream effector. Both the kinase activity of TESK1 and the level of cofilin phosphorylation increased by plating cells on fibronectin. Y-27632, a specific inhibitor of ROCK, inhibited LIM-kinase-induced cofilin phosphorylation but did not affect fibronectin-induced or TESK1-induced cofilin phosphorylation in HeLa cells. Expression of a kinase-negative TESK1 suppressed cofilin phosphorylation and formation of stress fibers and focal adhesions induced in cells plated on fibronectin. These results suggest that TESK1 functions downstream of integrins and plays a key role in integrin-mediated actin reorganization, presumably through phosphorylating and inactivating cofilin. We propose that TESK1 and LIM-kinases commonly phosphorylate cofilin but are regulated in different ways and play distinct roles in actin reorganization in living cells.

    Molecular biology of the cell 2001;12;4;1131-45

  • Interaction of the alpha subunit of Na,K-ATPase with cofilin.

    Lee K, Jung J, Kim M and Guidotti G

    College of Pharmacy, Center for Cell Signaling Research and Division of Molecular Life Sciences, Ewha Woman's University, Seoul 120-750, Korea. klyoon@mm.ewha.ac.kr

    The alpha1 subunit of rat Na,K-ATPase, composed of 1018 amino acids, is arranged in the membrane so that the middle third of the polypeptide forms a large cytoplasmic loop bordered on both sides by multiple transmembrane segments. To identify proteins that might interact with the large cytoplasmic loop of Na,K-ATPase and potentially affect the function and/or the disposition of the pump in the cell, the yeast two-hybrid system was used to screen a rat skeletal muscle cDNA library. Several cDNA clones were isolated, some of which coded for cofilin, an actin-binding protein. Cofilin was co-immunoprecipitated with the alpha subunit of Na,K-ATPase from extracts of COS-7 cells transiently transfected with haemagglutinin-epitope-tagged cofilin cDNA as well as from yeast extracts. By means of deletion analysis we showed that the segment of cofilin between residues 45 and 99 is essential for functional association with the large cytoplasmic loop of Na,K-ATPase. Recombinant cofilin was shown to bind to the membrane-bound Na,K-ATPase; the association between the two proteins was demonstrated by confocal microscopy. The increased level of cofilin in transfected COS-7 cells caused an increase in the rate of ouabain-sensitive (86)Rb(+) uptake, indicating that cofilin elicits, either directly or indirectly, enhanced Na,K-ATPase activity and that the interaction occurs in vivo.

    Funded by: NHLBI NIH HHS: HL08893; NIDDK NIH HHS: DK27626

    The Biochemical journal 2001;353;Pt 2;377-85

  • Nitric oxide induces chemotaxis of neutrophil-like HL-60 cells and translocation of cofilin to plasma membranes.

    Adachi R, Matsui S, Kinoshita M, Nagaishi K, Sasaki H, Kasahara T and Suzuki K

    Division of Xenobiotic Metabolism and Disposition, National Institute of Health Sciences, 1-18-1, Kamiyoga, Setagayaku, 158-8501, Tokyo, Japan.

    Nitric oxide (NO) plays various important roles in the physiological system. With regard to chemotaxis of neutrophils, there are reports that endogenous NO is a mediator of chemotaxis, and others that exogenous NO inhibits chemotaxis. It is also reported that NO itself expressed chemotactic activity. On the other hand, we have recently proposed the importance of cofilin, an actin-binding phosphoprotein, in phagocyte functions through dephosphorylation and translocation to the plasma membrane regions. Because chemotaxis is a phenomenon of dynamic cell movement, cofilin, a regulator of the cytoskeletal system, may be involved in its mechanisms. To clarify further the effect of NO on functions of leukocytes and to examine the effect of NO on cofilin, we investigated the chemotaxis of neutrophil-like HL-60 cells induced by NO, as well as the influence of NO on the phosphorylation and intracellular distribution of cofilin. Two NO donors, 3-[2-hydroxy-1-(1-methylethyl)-2-nitrosohydrazino]-1-propanamin e (NOC5) and S-nitroso-N-acetylpenicillamine (SNAP), were shown to cause chemotaxis, and, 2-(4-carboxyphenyl)-4,4,5, 5-tetramethylimidazole-1-oxyl 3-oxide (carboxy-PTIO), a NO-specific scavenger, inhibited the chemotaxis induced by NO-donors, suggesting that NO itself released from the NO donors has chemotactic activity. LY-83583 and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), inhibitors of soluble guanylate cyclase, inhibited the chemotaxis to NO donors, which implies that soluble guanylate cyclase is involved in the signaling pathway of this NO action. We also found that NO caused translocation of cofilin to the cell periphery, though dephosphorylation of cofilin was not detected. These results demonstrate that NO has chemotactic activity for neutrophils and caused the translocation of cofilin to the plasma membrane regions without its dephosphorylation.

    International journal of immunopharmacology 2000;22;11;855-64

  • Cofilin phosphorylation and actin cytoskeletal dynamics regulated by rho- and Cdc42-activated LIM-kinase 2.

    Sumi T, Matsumoto K, Takai Y and Nakamura T

    Division of Biochemistry, Department of Oncology, Biomedical Research Center, Osaka University Medical School, Suita, Japan.

    The rapid turnover of actin filaments and the tertiary meshwork formation are regulated by a variety of actin-binding proteins. Protein phosphorylation of cofilin, an actin-binding protein that depolymerizes actin filaments, suppresses its function. Thus, cofilin is a terminal effector of signaling cascades that evokes actin cytoskeletal rearrangement. When wild-type LIMK2 and kinase-dead LIMK2 (LIMK2/KD) were respectively expressed in cells, LIMK2, but not LIMK2/KD, phosphorylated cofilin and induced formation of stress fibers and focal complexes. LIMK2 activity toward cofilin phosphorylation was stimulated by coexpression of activated Rho and Cdc42, but not Rac. Importantly, expression of activated Rho and Cdc42, respectively, induced stress fibers and filopodia, whereas both Rho- induced stress fibers and Cdc42-induced filopodia were abrogated by the coexpression of LIMK2/KD. In contrast, the coexpression of LIMK2/KD with the activated Rac did not affect Rac-induced lamellipodia formation. These results indicate that LIMK2 plays a crucial role both in Rho- and Cdc42-induced actin cytoskeletal reorganization, at least in part by inhibiting the functions of cofilin. Together with recent findings that LIMK1 participates in Rac-induced lamellipodia formation, LIMK1 and LIMK2 function under control of distinct Rho subfamily GTPases and are essential regulators in the Rho subfamilies-induced actin cytoskeletal reorganization.

    The Journal of cell biology 1999;147;7;1519-32

  • Signaling from Rho to the actin cytoskeleton through protein kinases ROCK and LIM-kinase.

    Maekawa M, Ishizaki T, Boku S, Watanabe N, Fujita A, Iwamatsu A, Obinata T, Ohashi K, Mizuno K and Narumiya S

    Department of Pharmacology, Kyoto University Faculty of Medicine, Kyoto 606-8315, Japan.

    The actin cytoskeleton undergoes extensive remodeling during cell morphogenesis and motility. The small guanosine triphosphatase Rho regulates such remodeling, but the underlying mechanisms of this regulation remain unclear. Cofilin exhibits actin-depolymerizing activity that is inhibited as a result of its phosphorylation by LIM-kinase. Cofilin was phosphorylated in N1E-115 neuroblastoma cells during lysophosphatidic acid-induced, Rho-mediated neurite retraction. This phosphorylation was sensitive to Y-27632, a specific inhibitor of the Rho-associated kinase ROCK. ROCK, which is a downstream effector of Rho, did not phosphorylate cofilin directly but phosphorylated LIM-kinase, which in turn was activated to phosphorylate cofilin. Overexpression of LIM-kinase in HeLa cells induced the formation of actin stress fibers in a Y-27632-sensitive manner. These results indicate that phosphorylation of LIM-kinase by ROCK and consequently increased phosphorylation of cofilin by LIM-kinase contribute to Rho-induced reorganization of the actin cytoskeleton.

    Science (New York, N.Y.) 1999;285;5429;895-8

  • Aip1p interacts with cofilin to disassemble actin filaments.

    Rodal AA, Tetreault JW, Lappalainen P, Drubin DG and Amberg DC

    Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA.

    Actin interacting protein 1 (Aip1) is a conserved component of the actin cytoskeleton first identified in a two-hybrid screen against yeast actin. Here, we report that Aip1p also interacts with the ubiquitous actin depolymerizing factor cofilin. A two-hybrid-based approach using cofilin and actin mutants identified residues necessary for the interaction of actin, cofilin, and Aip1p in an apparent ternary complex. Deletion of the AIP1 gene is lethal in combination with cofilin mutants or act1-159, an actin mutation that slows the rate of actin filament disassembly in vivo. Aip1p localizes to cortical actin patches in yeast cells, and this localization is disrupted by specific actin and cofilin mutations. Further, Aip1p is required to restrict cofilin localization to cortical patches. Finally, biochemical analyses show that Aip1p causes net depolymerization of actin filaments only in the presence of cofilin and that cofilin enhances binding of Aip1p to actin filaments. We conclude that Aip1p is a cofilin-associated protein that enhances the filament disassembly activity of cofilin and restricts cofilin localization to cortical actin patches.

    Funded by: NIGMS NIH HHS: GM42759, GM56189, R01 GM042759, R01 GM056189, R37 GM042759

    The Journal of cell biology 1999;145;6;1251-64

  • Cofilin phosphorylation by LIM-kinase 1 and its role in Rac-mediated actin reorganization.

    Yang N, Higuchi O, Ohashi K, Nagata K, Wada A, Kangawa K, Nishida E and Mizuno K

    Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.

    Rac is a small GTPase of the Rho family that mediates stimulus-induced actin cytoskeletal reorganization to generate lamellipodia. Little is known about the signalling pathways that link Rac activation to changes in actin filament dynamics. Cofilin is known to be a potent regulator of actin filament dynamics, and its ability to bind and depolymerize actin is abolished by phosphorylation of serine residue at 3; however, the kinases responsible for this phosphorylation have not been identified. Here we show that LIM-kinase 1 (LIMK-1), a serine/threonine kinase containing LIM and PDZ domains, phosphorylates cofilin at Ser 3, both in vitro and in vivo. When expressed in cultured cells, LIMK-1 induces actin reorganization and reverses cofilin-induced actin depolymerization. Expression of an inactive form of LIMK-1 suppresses lamellipodium formation induced by Rac or insulin. Furthermore, insulin and an active form of Rac increase the activity of LIMK-1. Taken together, our results indicate that LIMK-1 participates in Rac-mediated actin cytoskeletal reorganization, probably by phosphorylating cofilin.

    Nature 1998;393;6687;809-12

  • Cytoskeletal proteins inside human immunodeficiency virus type 1 virions.

    Ott DE, Coren LV, Kane BP, Busch LK, Johnson DG, Sowder RC, Chertova EN, Arthur LO and Henderson LE

    AIDS Vaccine Program, National Cancer Institute, Frederick Cancer Research and Development Center, Maryland 21702-1201, USA. ott@avpvx1.ncifcrf.gov.

    We have identified three types of cytoskeletal proteins inside human immunodeficiency virus type 1 (HIV-1) virions by analyzing subtilisin-digested particles. HIV-1 virions were digested with protease, and the treated particles were isolated by sucrose density centrifugation. This method removes both exterior viral proteins and proteins associated with microvesicles that contaminate virion preparations. Since the proteins inside the virion are protected from digestion by the viral lipid envelope, they can be isolated and analyzed after treatment. Experiments presented here demonstrated that this procedure removed more than 95% of the protein associated with microvesicles. Proteins in digested HIV-1(MN) particles from infected H9 and CEM(ss) cell lines were analyzed by high-pressure liquid chromatography, protein sequencing, and immunoblotting. The data revealed that three types of cytoskeletal proteins are present in virions at different concentrations relative to the molar level of Gag: actin (approximately 10 to 15%), ezrin and moesin (approximately 2%), and cofilin (approximately 2 to 10%). Our analysis of proteins within virus particles detected proteolytic fragments of alpha-smooth muscle actin and moesin that were cleaved at sites which might be recognized by HIV-1 protease. These cleavage products are not present in microvesicles from uninfected cells. Therefore, these processed proteins are most probably produced by HIV-1 protease digestion. The presence of these fragments, as well as the incorporation of a few specific cytoskeletal proteins into virions, suggests an active interaction between cytoskeletal and viral proteins.

    Journal of virology 1996;70;11;7734-43

  • Dephosphorylation of serine 3 regulates nuclear translocation of cofilin.

    Nebl G, Meuer SC and Samstag Y

    Institute for Immunology, Ruprecht-Karls-University, Im Neuenheimer Feld 305, 69120 Heidelberg, Federal Republic of Germany.

    Signal transduction processes in T-cells and other cell types alter the phosphorylation state of cofilin, an actin-binding phosphoprotein. Whether reversible phosphorylation is responsible for the regulation of the functional activities of cofilin is not clear at present. Here we have identified the phosphoacceptor site of cofilin and analyzed the role of cofilin phosphorylation with respect to its subcellular localization. Site-directed mutagenesis studies show that phosphorylation occurs exclusively on Ser-3. Expression of non-phosphorylatable mutant cofilin proteins in NIH3T3 cells and determination of their subcellular localization by confocal laser scanning microscopy reveal that non-phosphorylated cofilin accumulates within nuclei. This analysis shows that the subcellular localization of cofilin depends on the phosphorylation state of Ser-3.

    The Journal of biological chemistry 1996;271;42;26276-80

  • Dephosphorylation of cofilin in polymorphonuclear leukocytes derived from peripheral blood.

    Okada K, Takano-Ohmuro H, Obinata T and Abe H

    Department of Biology, Chiba University, Japan.

    We show that human and porcine polymorphonuclear leukocytes express significant amounts of cofilin, a low-molecular-weight actin regulatory protein, as well as profilin. Fifty percent of the cofilin in the resting state was phosphorylated and dephosphorylation occurred after activation by fMLP or TPA. The time course of the dephosphorylation induced by fMLP was very rapid, ending within 1 min, while TPA induced relatively gradual dephosphorylation over a period of 10 min. Surprisingly, okadaic acid and calyculin A, potent inhibitors specific for phosphatase, both induced dephosphorylation of cofilin. This suggests that type 1 alone or both type 1 and 2A phosphatases are involved in the maintenance of the level of phosphorylation of cofilin in resting cells. The dephosphorylation of cofilin was barely detected by in vitro phosphatase assays, which can distinguish activities of types 1, 2B, and 2C. This indicates that cofilin is not dephosphorylated by conventional phosphatases. Although the dephosphorylation of cofilin was observed in cells treated with the calcium ionophore A23187, the phosphorylation level of cofilin was restored when the cells were further incubated in the presence of EGTA. Reactivation of these cells with TPA resulted in the dephosphorylation of cofilin; fMLP activation did not lead to dephosphorylation. Furthermore, a submicromolar concentration of wortmannin, which is an inhibitor specific for phosphatidylinositol 3-kinase, completely inhibited dephosphorylation of cofilin induced by fMLP, but did not suppress TPA-induced dephosphorylation. Thus, we conclude that the dephosphorylation of cofilin is differently regulated depending on either fMLP or TPA activation.

    Experimental cell research 1996;227;1;116-22

  • Mapping of human non-muscle type cofilin (CFL1) to chromosome 11q13 and muscle-type cofilin (CFL2) to chromosome 14.

    Gillett GT, Fox MF, Rowe PS, Casimir CM and Povey S

    MRC Human Biochemical Genetics Unit, Galton Laboratory, University College London.

    Cofilin is a widely-distributed, intracellular, actin binding protein which is involved in the translocation of actin-cofilin complex from cytoplasm to nucleus. We have cloned a non-muscle-type cofilin (CFL1) from a human promyelocytic cDNA library and mapped this to human chromosome 11 by PCR amplification of 3' untranslated sequence in a panel of rodent-human somatic cell hybrids, and to the interval 11q12-q13.2 in a chromosome 11 somatic cell hybrid mapping panel. Confirmation of regional localisation to 11q13 has been obtained by fluorescent in situ hybridisation of genomic cosmid clones, by demonstration of the presence of both SEA (the human homologue of avian retrovirus proviral tyrosine kinase, 11q13) and CFL1 in some of these clones and by close linkage of CFL1 to SEA in a panel of high-dose irradiation hybrids. We have identified human muscle-type cofilin sequences by comparison of human expressed sequence tags with M-type cofilins of other species and we have mapped the human M-type cofilin, CFL2, to chromosome 14.

    Annals of human genetics 1996;60;Pt 3;201-11

  • A provisional transcript map of the spinal muscular atrophy (SMA) critical region.

    van der Steege G, Draaijers TG, Grootscholten PM, Osinga J, Anzevino R, Velonà I, Den Dunnen JT, Scheffer H, Brahe C, van Ommen GJ et al.

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

    YACs from the region containing the spinal muscular atrophy (SMA) locus at 5q12 have been used as probes in a direct screening of cDNA libraries to isolate 8 cDNAs, mapped to different YAC fragments. Three clones showed complete identity to the genes for cyclin B1 (CCNB1), the p44 subunit of the transcription factor BTF2 (BTF2p44), and cofilin (CFL). Two clones showed partial identity to the beta-glucuronidase gene (GLCB) and a rat integral membrane glycoprotein gene (RNINMEGLA). CFL turned out to have been identified by a pseudogene sequence. Related sequences occurred on other chromosomes. CCNB1 and BTF2p44 were given an exact location. The GLCB-like gene and the RNINMEGLA-like gene detected loci on both 5q and 5p. The remaining three cDNA clones were localized to the SMA region only. Their sequences did not show identity to any gene for which a function is already known. Two of them have now turned out to be identical to recently reported candidate genes for SMA.

    Funded by: Telethon: 517

    European journal of human genetics : EJHG 1995;3;2;87-95

  • Dephosphorylation of cofilin in stimulated platelets: roles for a GTP-binding protein and Ca2+.

    Davidson MM and Haslam RJ

    Department of Pathology, McMaster University, Hamilton, Ontario, Canada.

    In human platelets, thrombin not only stimulates the phosphorylation of pleckstrin (P47) and of myosin P-light chains, but also induces the dephosphorylation of an 18-19 kDa phosphoprotein (P18) [Imaoka, Lynham and Haslam (1983) J. Biol. Chem. 258, 11404-11414]. We have now studied this protein in detail. The thrombin-induced dephosphorylation reaction did not begin until the phosphorylation of myosin P-light chains and the secretion of dense-granule 5-hydroxytryptamine were nearly complete, but did parallel the later stages of platelet aggregation. Experiments with ionophore A23187 and phorbol 12-myristate 13-acetate indicated that dephosphorylation of P18 was stimulated by Ca2+, but not by protein kinase C. Two-dimensional analysis of platelet proteins, using non-equilibrium pH gradient electrophoresis followed by SDS/PAGE, showed that thrombin decreased the amount of phosphorylated P18 in platelets by up to 70% and slightly increased the amount of a more basic unlabelled protein that was present in 3-fold excess of P18 in unstimulated platelets. These two proteins were identified as the phosphorylated and non-phosphorylated forms of the pH-sensitive actin-depolymerizing protein, cofilin, by sequencing of peptide fragments and immunoblotting with a monoclonal antibody specific for cofilin. The molar concentration of cofilin in platelets was approx. 10% that of actin. Platelet cofilin was phosphorylated exclusively on serine. Experiments with electropermeabilized platelets showed that dephosphorylation of cofilin could be stimulated by guanosine 5'-[gamma-thio]triphosphate (GTP[S]) in the absence of Ca2+ or by a free Ca2+ concentration of 10 microM. This GTP[S]-induced dephosphorylation reaction was inhibited by 1-naphthyl phosphate, but not by okadaic acid. Our results add cofilin to the actin-binding proteins that may regulate the platelet cytoskeleton, and suggest that platelet cofilin can be activated by dephosphorylation reactions initiated either by a GTP-binding protein or Ca2+.

    The Biochemical journal 1994;301 ( Pt 1);41-7

  • Characterization of a novel cofilin isoform that is predominantly expressed in mammalian skeletal muscle.

    Ono S, Minami N, Abe H and Obinata T

    Graduate School of Science and Technology, Chiba University, Japan.

    Cofilin is an actin-modulating protein of 20 kDa, which is widely distributed throughout muscle and non-muscle cells. By means of immunoblotting combined with two-dimensional gel electrophoresis, we found that two cofilin variants, muscle type (M-type) and non-muscle type (NM-type), exist in mammals, while a single isoform exists in chickens. During in vitro myogenesis of mouse C2 cells, expression of the M-type cofilin was upregulated. To better understand the nature of the M-type cofilin, we cloned cDNAs encoding M-type cofilin from the cDNA library of C2 myotubes and determined the entire sequence. The deduced peptide sequence contained a nuclear localization signal and a putative actin-binding sequence as reported in NM-type cofilin. The sequence showed 81% identity in the amino acid residues with the mouse NM-type cofilin sequence and, interestingly, higher homology (96% identity) with that of chicken cofilin. The mRNA encoding M-type cofilin, though it contains two variants that differ in the size of their 3'-non-coding sequences, was detected predominantly in heart, skeletal muscle, C2 myotubes, and testis by Northern blotting, while the mRNA for NM-type cofilin was seen in a variety of non-muscle tissues. The presence of the muscle type isoform of cofilin strongly suggests that cofilin is deeply involved in the regulation of actin function not only in non-muscle cells but also in muscle cells.

    The Journal of biological chemistry 1994;269;21;15280-6

  • Cytoplasmic localization and nuclear transport of cofilin in cultured myotubes.

    Abe H, Nagaoka R and Obinata T

    Department of Biology, Chiba University, Japan.

    We used immunofluorescence methods to examine the cellular distribution of cofilin in chicken myotubes in primary culture. Cofilin showed mainly diffuse distribution in the cytoplasm except for rather strong staining around the nuclei and faint striated patterns along myofibrils, but did not stain inside the nuclei. Neither stress fiber-like structures nor myofibrils were clearly stained. In the presence of 10% dimethyl sulfoxide (DMSO), intranuclear actin-cofilin rods, which were composed of alpha-actin isoform and cofilin, were formed in all the nuclei of individual myotubes. In the cofilin sequence, a putative nuclear localization signal (NLS) was observed. We examined the NLS activity of this portion by using a synthetic peptide corresponding to the putative NLS. When the NLS peptide conjugated with bovine serum albumin was microinjected into the cytoplasm of myotubes, it was rapidly accumulated into the nuclei. The same result was obtained with in vitro a nuclear protein import assay system with digitonin-permeabilized myotubes. Therefore, we suggest that this portion is responsible for the nuclear transport of cofilin. In myotubes, the majority of cofilin was present in an unphosphorylated form and this form remained unchanged after the DMSO treatment. Thus, we suggest that the phosphorylation of cofilin itself is not directly involved in its nuclear transport at least in myotubes.

    Experimental cell research 1993;206;1;1-10

  • Coding sequence of human placenta cofilin cDNA.

    Ogawa K, Tashima M, Yumoto Y, Okuda T, Sawada H, Okuma M and Maruyama Y

    Department of Internal Medicine, Faculty of Medicine, Kyoto University, Japan.

    Nucleic acids research 1990;18;23;7169

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
L00000016 G2C Homo sapiens Human PSP Human orthologues of mouse PSP adapted from Collins et al (2006) 1121
L00000049 G2C Homo sapiens TAP-PSD-95-CORE TAP-PSD-95 pull-down core list (ortho) 120
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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