© 1998 International Society for Neurochemistry Cytoskeletal and Phosphoinositide Requirements for Muscarinic Receptor Signaling to Focal

Abstract: The mechanism whereby agonist occupancy of muscarinic cholinergic receptors elicits an increased tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin has been examined. Addition of oxotremo-rine-M to SH-SY5Y neuroblastoma cells resulted in rapid increases in the phosphorylation of FAK (t112 = 2 mm)and paxillin that were independent of integrin—extracellular matrix interactions, cell attachment, and the production of phosphoinositide-derived second messengers. In con-trast, the increased tyrosine phosphorylations of FAK and paxillin were inhibited by inclusion of either cytochalasin D or mevastatin, agents that disrupt the cytoskeleton. Furthermore, phosphorylation of FAK and paxillin could be prevented by addition of either wortmannin or LY-294002, under conditions in which the synthesis of phos-phatidylinositol 4-phosphate was markedly attenuated. These results indicate that muscarinic receptor-mediated increases in the tyrosine phosphorylation of FAK and pax-illin in SH-SY5Y neuroblastoma cells depend on both the maintenance of an actin cytoskeleton and the ability of these cells to synthesize phosphoinositides. Ke