Identification of a novel protein complex containing annexin VI, Fyn, Pyk2, and the p120GAP C2 domain

p120(GAP) (RasGAP) has been proposed to function as both an inhibitor and effector of Ras. Previously Ive have shown that RasGAP contains a C2 domain which mediates both Ca2+ dependent membrane association and protein-protein interactions. Specifically, three proteins have been isolated in a complex with the C2 domain of RasGAP: these are the Ca2+-dependent lipid binding protein annexin VI (p70) and two previously unidentified proteins, p55 and p120, Here we provide evidence that p55 is the Src family kinase Fyn and p120 is the focal adhesion kinase family member Pyk2. In addition, in vitro binding assays indicate that Fyn, but not Pyk2 binds directly to annexin VI. Finally, co-immunoprecipitation studies in Rat-1 fibroblasts confirm that Fyn, Pyk2, annexin VI and RasGAP can form a protein complex: in mammalian cells. (C) 2000 Federation of European Biochemical Societies.