Receptor‐regulated formation of GTP[γS] with subsequent persistent Gs‐protein activation in membranes of human platelets

Abstract

Preincubation of human platelet membranes with the ATP analog ATP[γS] led to persistent adenylate cyclase activation. This stimulation was increased by copreincubation with PGE₁ and obliterated by removing endogenous GDP by the NTP-regenerating system, creatine phosphate plus creatine kinase. PGE₁ partially reversed the action of the regenerating system. Control formation of GTP[γS] from ATP[γS] and GDP in platelet membranes was apparently not stimulated by PGE₁. In contrast, in the presence of creatine phosphate plus creatine kinase, which prevented formation of GTP[γS], PGE₁ stimulated formation of this GTP analog, by partially reversing the action of the NTP-regenerating system. The data indicate that GTP[γS] can be formed by a membrane-associated nucleoside diphosphokinase from ATP[γS] and GDP, resulting in persistent G_s-protein activation, and that this process can be stimulated by an agonist-activated receptor.