CHARACTERIZATION OF THE MURINE PANCREATIC RECEPTOR FOR GASTRIN RELEASING PEPTIDE AND BOMBESIN

The murine pancreatic receptor for bombesin and gastrin releasing peptide (GRP) has been characterized. Analysis of the binding of I-125-GRP to membranes indicates a single class of sites (10(-13) mol/mg protein) with a K(d) of 43 pM. A 70 kDa membrane protein was cross-linked to I-125-GRP by bis(sulfosuccinimidyl) suberate; labeling was blocked by GRP, GRP (14-27), AcGRP(20-27), GRP(18-27), bombesin and ranatensin, was partially blocked by [Leu13-psi(CH2NH)Leu14]bombesin and was unaffected by GRP(21-27) and GRP(1-16). The IC50 values for the competitive displacement of I-125-GRP from intact membranes by these peptides were similar to those obtained by the cross-linking experiments showing that the 70 kDa protein is the GRP receptor. The GRP receptor is G-protein coupled; divalent cations are required for high-affinity binding and nonhydrolyzable GTP analogs decrease receptor affinity. In minced pancreas, GRP caused a dose-dependent increase in inositol phosphates implicating phospholipase C in signal transduction. We suggest that the murine pancreatic receptor for bombesin/GRP is a 70 kDa membrane protein, is associated with a G-protein and stimulates phosphatidylinositol turnover.