Irreversible photoactivation of a pancreatic secretagogue receptor with cholecystokinin COOH-terminal octapeptides

• Published in: The Journal of biological chemistry 1980-04, Vol.255 (7), p.3148-3155
• Main Authors: Galardy, R E, Hull, B E, Jamieson, J D
• Format: Article
• Language: English
• Subjects: Animals; Calcium - pharmacology; Carbonyl Cyanide m-Chlorophenyl Hydrazone - pharmacology; Cholecystokinin - analogs & derivatives; Cholecystokinin - pharmacology; Guinea Pigs; Kinetics; Male; Pancreas - cytology; Pancreas - metabolism; Pancreas - ultrastructure; Photochemistry; Receptors, Cell Surface - drug effects; Receptors, Cell Surface - metabolism; Sincalide
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)85864-7

The photochemically reactive analog of cholecystokinin octapeptide (CCK-8), 2-nitro-5-azidobenzoyl-Gly-Asp-Tyr-(SO3H)-Met-Gly-Trp-Met-Asp-Phe-NH2 (NAB-Gly-CCK-8), has been used to stimulate irreversibly the receptor for CCK-8 on preparations of dispersed guinea pig pancreatic acini. When continuously present with acini in the dark, NAB-Gly-CCK-8 is a reversible stimulant of secretory protein discharge with an ED50 of 0.4 nM. After six cycles of photolysis of acini with NAB-Gly-CCK-8 followed by extensive washing and assay in peptide-free medium in the dark, the photoactivated label induces irreversible discharge. Irreversible discharge is proportional to the concentration of NAB-Gly-CCK-8 present during photolysis and is nearly equivalent in intrinsic activity to that induced by CCK-8 in the dark. Inclusion of a 5-fold excess of prephotolyzed NAB-Gly-CCK-8 during photolysis partially protects against irreversible discharge, suggesting that the receptor irreversibly stimulated by NAB-Gly-CCK-8 is likely a receptor for peptides in the CCK family. Irreversible discharge requires metabolic energy supplied by oxidative phosphorylation and is dependent on extracellular Ca2+ and, thus, resembles that induced by reversible secretagogues.