FOCAL ADHESION AND STRESS FIBER FORMATION IS REGULATED BY TYROSINE PHOSPHATASE-ACTIVITY

Tyrosine phosphorylation of cytoskeletal proteins plays an important r ole in the regulation of focal adhesions and stress fiber organization . In the present study we examined the role of tyrosine phosphatases i n this process using p125FAK and paxillin as substrates. We show that tyrosine phosphatase activity in Swiss 3T3 cells was markedly increase d when actin stress fibers were disassembled by cell detachment from t he substratum, by serum starvation, or by cytochalasin D treatment. Th is activity was blocked by phenylarsine oxide, an inhibitor of a speci fic class of tyrosine phosphatases characterized by two vicinal thiol groups in the active site, Phenylarsine oxide treatment of serum-starv ed cells induced increased tyrosine phosphorylation of p125FAK and pax illin in a dose-dependent manner and induced assembly of focal adhesio ns and actin stress fibers, showing that inhibition of one or more phe nylarsine oxide-sensitive tyrosine phosphatases is a sufficient stimul us for triggering focal adhesion and actin stress fiber formation in a dherent cells. (C) 1996 Academic Press, Inc.