Fibroblast growth factor receptor-1-mediated endothelial cell proliferation is dependent on the Src homology (SH) 2/SH3 domain-containing adaptor protein Crk

Stimulation of fibroblast growth factor receptor-2 (FGFR-1) expressed on endothelial cells leads to cellular migration and proliferation. We have examined the role of the Src homology (SH) 2/SH3 domain-containing adaptor protein Crk in these processes. Transient tyrosine phosphorylation of Crk in fibroblast growth factor-2-stimulated endothelial cells was dependent on the juxtamembrane tyrosine residue 463 in FGFR-1, and a Crk SH2 domain precipitated FGFR-1 via phosphorylated Tyr-463, indicating direct complex formation between Crk and FGFR-1. Furthermore, Crk SH2 and SH3 domains formed ligand-independent complexes with Shc, C3G, and the Crk-associated substrate (Cas). Tyrosine phosphorylation of C3G and Cas increased as a consequence of growth factor treatment, We examined the role of Crk in FGFR-1-mediated cellular responses by use of cells expressing chimeric platelet-derived growth factor receptor-alpha/FGFR-1 (alpha R/FR) wild type and mutant Y463F receptors. The kinase activity of alpha R/FR Y463F was intact, but both Crk and the adaptor FRS-2 were no longer tyrosine-phosphorylated in the mutant cells. Both wild type and mutant receptor cells migrated efficiently, whereas cells expressing the mutant alpha R/FR Y463F failed to proliferate and Erk2 and Jun kinase activities were suppressed in these cells. In wild type alpha R/FR cells transiently expressing an SH2 domain mutant of Crk, Erk and Jun kinase activities as well as DNA synthesis were attenuated. Our data indicate that Crk participates in signaling complexes downstream of FGFR-1, which propagate mitogenic signals.