DEPOLARIZATION-INDUCED TYROSINE PHOSPHORYLATION OF P130(CAS)

KCl-treatment of PC12 cells induces depolarization of the plasma membr ane and Ca2+ influx into the cells, We have previously shown that KCl induced tyrosine phosphorylation of cellular proteins of 120, 110, 68, 44, and 42 k, and that the 68 k protein was paxillin, In the present study, we found that the 120 k protein was a Crk-associated Src substr ate, p130(cas). KCl-induced tyrosine phosphorylation of p130(cas) was not observed in EGTA-containing medium, suggesting that it was due to Ca2+ influx into the cells, Time course experiments showed that tyrosi ne phosphorylation of p130(cas) peaked at 5 min after stimulation and returned to the basal level at 60 min, while mobility shift of p130(ca s) was observed within 2 min and lasted over 60 min, indicating that s erine or threonine residues, in addition to tyrosine, were phosphoryla ted on KCl stimulation. In vitro kinase assay of immunoprecipitates wi th anti-p130(cas) antibody suggested that some protein-tyrosine kinase s were associated with p130(cas). Using the substrate region of p130(c as) as the substrate, we found that Fyn and Src were activated on stim ulation with KCI. These results indicate that tyrosine phosphorylation of p130(cas) may be involved in Ca2+-dependent events in neuronal and neuroendocrine cells.