Activation of m3 muscarinic receptors induces rapid tyrosine phosphorylation of p125(FAK), p130(cas) and paxillin in rat pancreatic acini

Tyrosine phosphorylation plays a key role in transmembrane and cytoplasmic signal transduction mechanisms stimulated by oncogenes, integrins, growth f actors, neuropeptides, and bioactive lipids. Moreover, recent studies show that stimulation of odd-numbered muscarinic receptors increases the tyrosin e phosphorylation of several proteins in different cellular types. The pres ent study was aimed at examining whether activation of m3 muscarinic recept ors in rat pancreatic acini evokes tyrosine phosphorylation of p125(FAK), a nd its substrates, p130(cas) and paxillin. Results show that stimulation of pancreatic acini with carbachol resulted in a rapid and transient increase in tyrosine phosphorylation of p125(FAK), p130(cas), and paxillin. Tyrosin e phosphorylation of these proteins occurred in a time- and concentration-d ependent manner. Simultaneous blockage of both PKC activation and increases in [Ca2+](i) partially decreased p125(FAK), p130(cas), and paxillin tyrosi ne phosphorylation stimulated by carbachol. Pretreatment of pancreatic acin i with Clostridium botulinum C3 transferase, which specifically inactivates p21(rho), partially inhibited carbachol-induced p125(FAK), p130(cas), and paxillin tyrosine phosphorylation. In contrast, this treatment had no effec t on amylase release stimulated by carbachol. Cytochalasin D, which disrupt s actin microfilaments network, completely inhibited carbachol stimulated t yrosine phosphorylation of these proteins without having significant effect s in carbachol-stimulated amylase secretion. These results dissociate tyros ine phosphorylation of p125(FAK), p130(cas), and paxillin from amylase secr etion after m3 muscarinic receptors occupation in rat pancreatic acini. Tak en together, these data suggest that (a) activation of m3 muscarinic recept ors in rat pancreatic acini increases tyrosine phosphorylation of p125(FAK) and its substrates, p130(cas) and paxillin by diacylglycerol-activated PKC - and calcium- dependent, and independent pathways, (b) these responses req uire activation of p21(rho) and an intact actin cytoskeleton, and (c) p125( FAK), p130(cas), and paxillin are unlikely related to secretion in rat panc reatic acinar cells. (C) 2000 Academic Press.