INTERACTION BETWEEN FOCAL ADHESION KINASE AND CRK-ASSOCIATED TYROSINEKINASE SUBSTRATE P130(CAS)

The focal adhesion kinase (FAK) has been implicated in integrin-mediat ed signaling events and in the mechanism of cell transformation by the v-Src and v-Crk oncoproteins. To gain further insight into FAK signal ing pathways, we used a two-hybrid screen to identify proteins that in teract with mouse FAK. The screen identified two proteins that interac t with FAK via their Src homology 3 (SH3) domains: a v-Crk-associated tyrosine kinase substrate (Gas), p130(Cas), and a still uncharacterize d protein, FIPSH3-2, which contains an SH3 domain closely related to t hat of p130(Cas). These SH3 domains bind to the same proline-rich regi on of FAK (APPKPSR) encompassing residues 711-717. The mouse p130(Cas) amino acid sequence was deduced from cDNA clones, revealing an overal l high degree of similarity to the recently reported rat sequence, Coi mmunoprecipitation experiments confirmed that p130(Cas) and FAK are as sociated in mouse fibroblasts. The stable interaction between p130(Cas ) and FAK emerges as a likely key element in integrin-mediated signal transduction and further represents a direct molecular link between th e v-Src and v-Crk oncoproteins. The Src family kinase Fyn, whose Src h omology 2 (SH2) domain binds to the major FAIL autophosphorylation sit e (tyrosine 397), was also identified in the two-hybrid screen.