MOLECULAR-CLONING AND FUNCTIONAL-CHARACTERIZATION OF A HUMAN SECRETINRECEPTOR

Secretin is a gastrointestinal hormone responsible for the regulation of bicarbonate, potassium ion and enzyme secretion from the pancreas. A cDNA encoding the human secretin receptor was isolated from a human pancreatic adenocarcinoma cell-line cDNA library using polymerase chai n reaction and library screening techniques. The cDNA isolated is 1717 bp in length encoding a 440 amino acid long polypeptide. Computer ana lysis of the receptor indicated that it is a member of the glucagon-VI P-secretin receptor family and is a G-protein coupled receptor contain ing seven hydrophobic transmembrane domains. The receptor was subseque ntly expressed in COS-7 cells and was able to bind specifically to hum an secretin with high affinity as indicated by the competitive displac ement assay. The human secretin receptor was found to be functionally coupled to the stimulation of adenylyl cyclase resulting in the accumu lation of intracellular cAMP in a dose-dependent manner. By Northern b lot analysis, a 1.8 Kb mRNA was detected in human pancreas and intesti ne, while weak hybridization signals were detected in human colon, kid ney and lung. Functional characterization of this receptor should enha nce our understanding of the physiology and pathophysiology of human s ecretin, its structure-function, receptor interaction and receptor tis sue distribution. (C) 1995 Academic Press, Inc.