Distinct roles for Crk adaptor isoforms in actin reorganization induced by extracellular signals.
Crk family adaptors, consisting of Src homology 2 (SH2) and SH3 protein-binding domains, mediate assembly of protein complexes in signaling. CrkI, an alternately spliced form of Crk, lacks the regulatory phosphorylation site and C-terminal SH3 domain present in CrkII and CrkL. We used gene silencing combined with mutational analysis to probe the role of Crk adaptors in platelet-derived growth-factor receptor beta (PDGFbetaR) signaling. We demonstrate that Crk adaptors are required for formation of focal adhesions, and for PDGF-stimulated remodeling of the actin cytoskeleton and cell migration. Crk-dependent signaling is crucial during the early stages of PDGFbetaR activation, whereas its termination by Abl family tyrosine kinases is important for turnover of focal adhesions and progression of dorsal-membrane ruffles. CrkII and CrkL preferentially activate the small GTPase Rac1, whereas variants lacking a functional C-terminal SH3 domain, including CrkI, preferentially activate Rap1. Thus, differences in the activity of Crk isoforms, including their effectors and their ability to be downregulated by phosphorylation, are important for coordinating dynamic changes in the actin cytoskeleton in response to extracellular signals.
Antoku
Susumu
S
Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT 06030-3301, USA.
Mayer
Bruce J
BJ
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology*; D022001:Focal Adhesions / Q000378:metabolism*; D020868:Gene Silencing; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D016315:Proto-Oncogene Proteins c-abl / Q000378:metabolism; D050737:Proto-Oncogene Proteins c-crk / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism; D018909:src Homology Domains / Q000502:physiology
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C485285:CRK protein, human; C082869:CRKL protein; D009687:Nuclear Proteins; D020033:Protein Isoforms; D050737:Proto-Oncogene Proteins c-crk; D020797:Receptor, Platelet-Derived Growth Factor beta; D016315:Proto-Oncogene Proteins c-abl; D020830:rac1 GTP-Binding Protein; D020827:rap1 GTP-Binding Proteins