Fig. 8. FAK and Src cooperate in integrin-initiated tyrosine phosphorylation of cortactin. (A) Serum-starved FAK(+) and FAK(–) cells were either kept in suspension (Sus) or seeded on fibronectin (Fn) or poly-L-lysine (PL)-coated dishes for 30 minutes. Samples were treated with pervanadate for 5 minutes before lysis. After cortactin immunoprecipitation (IP), samples were analysed by western blotting with monoclonal anti-phosphotyrosine antibody (P.Tyr; upper panel). Following stripping, the blot was re-probed with polyclonal anti-cortactin antibodies (lower panel). The graph shows the ratio between phosphorylated cortactin and the total amount of cortactin present in the immunoprecipitates. For comparison, the ratio of FAK(–) cells plated onto poly-L-lysine was set to 1. (B) Serum-starved FAK(+) or FAK(–) cells were seeded onto poly-L-lysine-coated dishes and infected with S. aureus for 1 hours or left uninfected. Whole cell lysates (WCL) were analysed by western blotting and probed with monoclonal anti-phosphotyrosine antibody (P.Ttyr; upper panel). After stripping, membranes were re-probed with polyclonal anti-cortactin antibodies (lower panel). (C) Serum-starved FAK(+) cells were seeded onto poly-L-lysine-coated dishes and either left uninfected or infected with S. aureus for 1 hour in the presence or absence of 5 µM PP2. After cortactin immunoprecipitation (IP), samples were analysed by western blotting with monoclonal anti-phosphotyrosine antibody (P.Tyr; upper panel). Following stripping, the blot was re-probed with polyclonal anti-cortactin antibodies (lower panel).