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

AbstractThe neuropeptide substance P and the polyamine compound 4880, both known to activate mast cell secretory processes, increased the rate of GTPγS binding to G-proteins purified from calf brain (Go/Gi mixture). The GTPase activity of G-proteins was also increased by substance P and compound 4880 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 4880 and substance P is not due to a receptor-mediated process but, like mastoparan, results from a direct activation of G-proteins