title: Muscle costameric protein, Chisel/Smpx, associates with focal adhesion complexes and modulates cell spreading in vitro via a Rac1/p38 pathway.
abstract: The murine X-linked gene Chisel (Csl/Smpx) encodes a 9-kDa protein that associates in heart and skeletal muscle cells with the costameric cytoskeleton, implicated in maintaining muscle integrity and responses to biomechanical stress. After expression in C2C12 myoblasts, MYC epitope-tagged Csl co-localized with actin networks at peripheral membranes, and with focal adhesion proteins vinculin, paxillin, integrin beta1, and the small GTPase Rac1. Csl could be co-immunoprecipitated with vinculin from extracts of C2C12 cells and native muscle. MYC-Csl induced cell spreading and lamellipodia formation in C2C12 cells at the expense of filopodia, suggestive of modulation of Rac1 activity. Lamellipodia formation was indeed Rac1-dependent, and in MYC-Csl cells replated on fibronectin, Rac1 activity was increased relative to controls. Expression of MYC-Csl led to an increased association between vinculin and p34, a subunit of the Arp2/3 actin nucleation complex, a Rac1-dependent event. Induced cell spreading was also dependent upon p38 kinases that act downstream of Rac1 to control the actin capping activity of heat shock protein 27. Our data suggest that Csl localizes to the costameric cytoskeleton of muscle cells through an association with focal adhesion proteins, where it may participate in regulation of cytoskeletal dynamics through the Rac1-p38 pathway.
authors.affiliation: Developmental Biology Program, Victor Chang Cardiac Research Institute, 384 Victoria Street, Darlinghurst NSW 2010, Australia.
authors.forename: Aaron
authors.initials: A
authors.lastname: Schindeler
authors.forename: Lopeti
authors.initials: L
authors.lastname: Lavulo
authors.forename: Richard P
authors.initials: RP
authors.lastname: Harvey
mesh_terms: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002460:Cell Line; D048430:Cell Shape / Q000502:physiology*; D024141:Collagen Type IV / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000378:metabolism; D022001:Focal Adhesions / Q000737:chemistry / Q000378:metabolism*; D006023:Glycoproteins / Q000494:pharmacology; D019012:Integrin beta1 / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D048290:Mitogen-Activated Protein Kinase 11 / Q000037:antagonists & inhibitors; D048308:Mitogen-Activated Protein Kinase 14 / Q000037:antagonists & inhibitors; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009154:Mutation / Q000235:genetics; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011554:Pseudopodia / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D016596:Vinculin / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020830:rac1 GTP-Binding Protein; D054460:rho-Associated Kinases
chemical_list: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; C495927:Actr2 protein, mouse; C495929:Actr3 protein, mouse; D015815:Cell Adhesion Molecules; D024141:Collagen Type IV; D003598:Cytoskeletal Proteins; D006023:Glycoproteins; D019012:Integrin beta1; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D009479:Neuropeptides; D051419:Paxillin; D010750:Phosphoproteins; D047428:Protein Kinase Inhibitors; C496062:Pxn protein, mouse; C484602:Rac1 protein, mouse; C499035:Smpx protein, mouse; D016596:Vinculin; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D048290:Mitogen-Activated Protein Kinase 11; D048308:Mitogen-Activated Protein Kinase 14; D048051:p38 Mitogen-Activated Protein Kinases; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein