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, but little is known about their regulation by physiological stimuli. Using a novel single-electrode technique, together with dye coupling studies, we show that in cells expressing gap junction protein connexin43, cell–cell communication is rapidly disrupted by G protein–coupled receptor agonists, notably lysophosphatidic acid, thrombin, and neuropeptides. In the continuous presence of agonist, junctional communication fully recovers within 1–2 h of receptor stimulation. In contrast, a desensitization-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 junction closure consistently follows inositol lipid breakdown and membrane depolarization and coincides with Rho-mediated cytoskeletal remodeling. However, we find that gap junction closure is independent of Ca²⁺, protein kinase C, mitogen-activated protein kinase, or membrane potential, and requires neither Rho nor Ras activation. Gap junction closure 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 communication.