title: Somatostatin receptors on rat cerebrocortical membranes. Structural characterization of somatostatin-14 and somatostatin-28 receptors and comparison with pancreatic type receptors.
abstract: Somatostatin binding and cross-linking to its receptors on rat cerebrocortical membranes were characterized with [125I-Tyr1]somatostatin-14 and [125I-Leu8, D-Trp22, Tyr25]somatostatin-28. When [125I-Tyr1]somatostatin-14 was cross-linked to its receptors with the photoreactive cross-linker, N-(5-azido-2-nitrobenzoyloxy)succinimide, the hormone was specifically associated with a Mr = 72,000 protein band in the presence or absence of reducing agents. Affinity labeling of the Mr = 72,000 protein band was decreased with increasing concentrations of unlabeled somatostatin-14 and nonhydrolyzable guanine nucleotide analog, guanyl-5'-yl imidodiphosphate (Gpp(NH)p). Pretreatment of cerebrocortical membranes with islet-activating protein resulted in a decrease in subsequent labeled somatostatin-14 binding and affinity-labeling of the protein and abolished an inhibitory effect of somatostatin-14 on vasoactive intestinal peptide-stimulated increase in adenylate cyclase activity. When the affinity-labeled protein was solubilized with Zwittergent 3-12 and adsorbed to wheat germ agglutinin-agarose, it was eluted by N-acetylglucosamine. [125I-Leu8, D-Trp22, Tyr25]somatostatin-28 cross-linking to cerebrocortical and pancreatic membranes with the same photoreactive agent revealed specifically labeled protein bands of a Mr = 74,000 in cerebrocortical membranes and a Mr = 94,000 in pancreatic membranes, respectively. These results suggest that: 1) somatostatin receptor on cerebrocortical membranes is a monomeric glycoprotein with a Mr = 70,000 binding subunit, coupled to guanine nucleotide regulatory protein, and 2) the Mr = 70,000 protein may be a common receptor for somatostatin-28 and somatostatin-14 and is distinct from a common pancreatic type receptor.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D002846:Chromatography, Affinity; D003432:Cross-Linking Reagents / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008970:Molecular Weight; D009928:Organ Specificity; D010179:Pancreas / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D017981:Receptors, Neurotransmitter / Q000302:isolation & purification / Q000378:metabolism*; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000378:metabolism*; D053561:Somatostatin-28
chemical_list: D003432:Cross-Linking Reagents; D017981:Receptors, Neurotransmitter; D017481:Receptors, Somatostatin; D013004:Somatostatin; D053561:Somatostatin-28; D000262:Adenylyl Cyclases