title: Phosphorylation of the cytoskeletal protein CAP1 controls its association with cofilin and actin.
abstract: Cell signaling can control the dynamic balance between filamentous and monomeric actin by modulating actin regulatory proteins. One family of actin regulating proteins that controls actin dynamics comprises cyclase-associated proteins 1 and 2 (CAP1 and 2, respectively). However, cell signals that regulate CAPs remained unknown. We mapped phosphorylation sites on mouse CAP1 and found S307 and S309 to be regulatory sites. We further identified glycogen synthase kinase 3 as a kinase phosphorylating S309. The phosphomimetic mutant S307D/S309D lost binding to its partner cofilin and, when expressed in cells, caused accumulation of actin stress fibers similar to that in cells with reduced CAP expression. In contrast, the non-phosphorylatable S307A/S309A mutant showed drastically increased cofilin binding and reduced binding to actin. These results suggest that the phosphorylation serves to facilitate release of cofilin for a subsequent cycle of actin filament severing. Moreover, our results suggest that S307 and S309 function in tandem; neither the alterations in binding cofilin and/or actin, nor the defects in rescuing the phenotype of the enlarged cell size in CAP1 knockdown cells was observed in point mutants of either S307 or S309. In summary, we identify a novel regulatory mechanism of CAP1 through phosphorylation.
authors.affiliation: Department of Biological Sciences, Arkansas State University, State University, AR 72467, USA Molecular Biosciences Program, Arkansas State University, State University, AR 72467, USA gzhou@astate.edu.
authors.forename: Guo-Lei
authors.initials: GL
authors.lastname: Zhou
authors.affiliation: Department of Biological Sciences, Arkansas State University, State University, AR 72467, USA Molecular Biosciences Program, Arkansas State University, State University, AR 72467, USA.
authors.forename: Haitao
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Biological Sciences, Arkansas State University, State University, AR 72467, USA.
authors.forename: Huhehasi
authors.initials: H
authors.lastname: Wu
authors.affiliation: Department of Biological Sciences, Arkansas State University, State University, AR 72467, USA Molecular Biosciences Program, Arkansas State University, State University, AR 72467, USA.
authors.forename: Pooja
authors.initials: P
authors.lastname: Ghai
authors.affiliation: Department of Pharmacology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Field
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002465:Cell Movement; D055785:Gene Knockdown Techniques; D005838:Genotype; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D009154:Mutation; D041681:NIH 3T3 Cells; D010641:Phenotype; D010766:Phosphorylation; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D015398:Signal Transduction; D014162:Transfection
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D002352:Carrier Proteins; C525401:CAP1 cyclase-associated protein, mouse; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3
keywords: Actin cytoskeleton; Actin dynamics; Cell migration; Cell signaling; Kinase