Focal adhesion-associated proteins p125FAK and paxillin are substrates for bradykinin-stimulated tyrosine phosphorylation in Swiss 3T3 cells.

In this study we examined the involvement of the focal adhesion-associated proteins p125FAK and paxillin as substrates for bradykinin (BK)-stimulated tyrosine phosphorylation in Swiss 3T3 cells and the potential role of protein kinase C and Ca2+ in these events. BK (1 microM) stimulated tyrosine phosphorylation of p125FAK and paxillin. In addition, BK also increased the phosphotyrosine content of the src transformation-associated protein p130. The responses were rapid and transient and peaked at approximately 1 min after BK addition. Furthermore, the responses were dose-dependent with half-maximal effects occurring at 1-10 nM BK. The phosphotyrosine content of p125FAK, paxillin, and p130 was also increased following stimulation with phorbol 12-myristate 13-acetate (PMA) (0.1 microM). In contrast, PMA had no effect on the phosphotyrosine content of p125, a Ras-GAP-associated tyrosine phosphoprotein that we recently identified. Long term pretreatment (18 h) of cells with 0.3 microM PMA partially attenuated BK-stimulated phosphorylation of p125FAK but was without effect on phosphorylation of paxillin and Ras-GAP-associated p125. Furthermore, only a small inhibition of BK- and PMA-stimulated phosphorylation of p125FAK was observed following pretreatment with 25 microM BAPTA/AM. In all, these results show that multiple mechanisms are involved in BK-stimulated tyrosine phosphorylation of p125FAK, paxillin, Ras-GAP-associated p125, and src transformation-associated p130.