Crk associates with a multimolecular Paxillin/GIT2/beta-PIX complex and promotes Rac-dependent relocalization of Paxillin to focal contacts.
We have previously demonstrated that the CrkII and CrkL adapter proteins are required for the spreading of epithelial colonies and the breakdown of adherens junctions in response to hepatocyte growth factor. When overexpressed, CrkII and CrkL promote lamellipodia formation, cell spreading, and the loss of epithelial adherens junctions in the absence of hepatocyte growth factor. The exact mechanism by which Crk proteins elicit these changes is unclear. We show that the overexpression of CrkII or CrkL, but not Src homology 2 or amino-terminal Src homology 3 domain mutant Crk proteins, promotes the relocalization of Paxillin to focal contacts throughout the cell and within lamellipodia in a Rac-dependent manner. In stable cell lines overexpressing CrkII, enhanced lamellipodia formation and cell spreading correlate with an increased association of CrkII with Paxillin, GIT2 (an ARF-GAP) and beta-PIX (a Rac1 exchange factor). Mutants of Paxillin that fail to associate with Crk or GIT2, or do not target to focal adhesions inhibit Crk-dependent cell spreading and lamellipodia formation. We conclude from these studies that the association of Crk with Paxillin is important for the spreading of epithelial colonies, by influencing the recruitment of Paxillin to focal complexes and promoting the enhanced assembly of Paxillin/GIT2/beta-PIX complexes.
Lamorte
Louie
L
Molecular Oncology Group, McGill University Health Centre, Department of Biochemistry, McGill University, Montreal, Quebec, Canada H3A 1A1.
Rodrigues
Sonia
S
Sangwan
Veena
V
Turner
Christopher E
CE
Park
Morag
M
D048868:Adaptor Proteins, Signal Transducing; D022005:Adherens Junctions / Q000187:drug effects; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002465:Cell Movement; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D022001:Focal Adhesions / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D017228:Hepatocyte Growth Factor / Q000378:metabolism / Q000494:pharmacology; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D051419:Paxillin; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D050737:Proto-Oncogene Proteins c-crk; D011554:Pseudopodia / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors
D048868:Adaptor Proteins, Signal Transducing; C082869:CRKL protein; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D051419:Paxillin; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; D064067:Rho Guanine Nucleotide Exchange Factors; D017228:Hepatocyte Growth Factor