Direct activation of GTP‐binding regulatory proteins (G‐proteins) by substance P and compound 48/80

Abstract

The neuropeptide substance P and the polyamine compound , both known to activate mast cell secretory processes, increased the rate of GTP_γS binding to G-proteins purified from calf brain (G_o/G_i mixture). The GTPase activity of G-proteins was also increased by substance P and compound in a dose-dependent and Mg²⁺-dependent way. These effects were similar to those of the wasp venom peptide rnastoparan, another histamine releaser of rat peritoneal and human skin mast cells. This suggests that the secretory property of compound and substance P is not due to a receptor-mediated process but, like mastoparan, results from a direct activation of G-proteins.