BOTULINUM C3 EXOENZYME BLOCKS THE TYROSINE PHOSPHORYLATION OF P125(FAK) AND PAXILLIN INDUCED BY BOMBESIN AND ENDOTHELIN

In this study we examined the role of rho p21 in neuropeptide-stimulat ed tyrosine phosphorylation. Intact Swiss 3T3 cells were treated with the Clostridium botulinum C3 exoenzyme which specifically ADP ribosyla tes and inactivates rho p21. C3 exoenzyme treatment of cells caused a marked decrease in both bombesin- and endothelin-stimulated tyrosine p hosphorylation of multiple proteins, including p125 focal adhesion kin ase (FAK) and paxillin. Our results suggest that rho p21 is a componen t of the signal transduction pathway linking seven transmembrane domai n receptors with tyrosine phosphorylation and cytoskeletal events.