Y-27632, an inhibitor of Rho-associated kinases, prevents tyrosine phosphorylation of focal adhesion kinase and paxillin induced by bombesin: Dissociation from tyrosine phosphorylation of p130(cas)

A rapid increase in tyrosine phosphorylation of focal adhesion kinase (FAK) , paxillin, and Crk-associated substrate (CAS) are prominent early events t riggered by many G protein-coupled receptors (GrPCRs), but the mechanisms i nvolved remain unclear. Here, we examined whether the Rho-associated protei n serine/threonine kinase family (ROCK) is a critical Rho effector in the p athway that links GPCR activation to the tyrosine phosphorylation of FAK, C AS, and paxillin. Treatment of Swiss 3T3 cells with Y-27632, a preferential inhibitor of ROCK, dramatically inhibited the formation of actin stress fi bers, the assembly of focal contacts, and the increase in tyrosine phosphor ylation of FAK and paxillin induced by bombesin in these cells. Surprisingl y, we found that treatment with Y-27632 did not produce any detectable effe ct on bombesin-elicited CAS tyrosine phosphorylation even at the highest co ncentrations of Y-27632 tested. HA-1077, a preferential inhibitor of ROCK a ctivity structurally unrelated to Y-27632, also attenuated the increase in the tyrosine phosphorylation of FAK and paxillin but did not affect the tyr osine phosphorylation of CAS induced by bombesin in Swiss 3T3 cells. The re sults demonstrate that ROCK-dependent tyrosine phosphorylation of FAK and p axillin can be dissociated from a ROCK-independent pathway leading to tyros ine phosphorylation of CAS. (C) 2001 Academic Press.