ACUTE LOSS OF CELL-CELL COMMUNICATION CAUSED BY G-PROTEIN-COUPLED RECEPTORS - A CRITICAL ROLE FOR C-SRC

Gap junctions mediate cell-cell communication in almost all tissues, b ut little is known about their regulation by physiological stimuli. Us ing a novel single-electrode technique, together with dye coupling stu dies, we show that in cells expressing gap junction protein connexin43 , cell-cell communication is rapidly disrupted by G protein-coupled re ceptor agonists, notably lysophosphatidic acid, thrombin, and neuropep tides. In the continuous presence of agonist, junctional communication fully recovers within 1-2 h of receptor stimulation. In contrast, a d esensitization-defective G protein-coupled receptor mediates prolonged uncoupling, indicating that recovery of communication is controlled, at least in part, by receptor desensitization. Agonist-induced gap jun ction closure consistently follows inositol lipid breakdown and membra ne depolarization and coincides with Rho-mediated cytoskeletal remodel ing. However, we find that gap junction closure is independent of Ca2, protein kinase C, mitogen-activated protein kinase, or membrane pote ntial, and requires neither Rho nor Ras activation. Gap junction closu re is prevented by tyrphostins, by dominant-negative c-Src, and in Src -deficient cells. Thus, G protein-coupled receptors use a Src tyrosine kinase pathway to transiently inhibit connexin43-based cell-cell comm unication.