Translocation of CrkL to Focal Adhesions Mediates Integrin-Induced Migration Downstream of Src Family Kinases

Abstract

The adapter protein Crk-Like (CrkL) can associate with the Src substrate p130 ^Cas (Cas). The biological role of CrkL downstream of Cas, however, has been largely obscure. Consistent with the ability of CrkL to biochemically associate with Cas, we found that Src triggers translocation of CrkL to focal adhesions (FAs) in a manner dependent on Cas. Forced localization of CRKL to FAs (FA-CRKL) by itself was sufficient to induce activation of Rac1 and Cdc42 and rescued haptotaxis defects of mouse embryonic fibroblasts (MEFs) lacking Src, Yes, and Fyn, three broadly expressed Src family members required for integrin-induced migration. Consistent with Rac1 activation, FA-CRKL induced cotranslocation of a Rac1 activator, Dock1, to focal adhesions. These results therefore indicate a role for CrkL in mediating Src signaling by activating small G proteins at focal adhesions. Furthermore, MEFs lacking CrkL show impaired integrin-induced migration despite expression of a closely related protein, Crk-II, in these cells. These results therefore provide formal evidence that CrkL plays a specific role in integrin-induced migration as a downstream mediator of Src.

ACKNOWLEDGMENTS

We thank S. Kron for critical reading of the manuscript; B. J. Druker, F. B. Gertler, H. Hirai, M. Matsuda, G. P. Nolan, S. M. Thomas, M. A. Schwartz, and P. Soriano for valuable reagents; and S. Bond for technical assistance at the University of Chicago Digital Microscopy Facility.

This work was supported in part by grants to A.I. from Wendy Will Case Cancer Fund, the American Cancer Society (RPG 00-239-01-CSM), and Department of the Army (DAMD 17-02-1-0639).