PURIFICATION, MOLECULAR-CLONING, AND FUNCTIONAL EXPRESSION OF THE CHOLECYSTOKININ RECEPTOR FROM RAT PANCREAS

The cholecystokinin (CCK) family of peptides and their receptors are w idely distributed throughout the gastrointestinal and central nervous systems where they regulate secretion, motility, growth, anxiety, and satiety. The CCK receptors can be subdivided into at least two subtype s, CCK(A) and CCK(B) on the basis of pharmacological studies. We repor t here the purification of the CCK(A) receptor to homogeneity from rat pancreas by using ion-exchange and multiple affinity chromatographic separations. This allowed partial peptide sequencing after chemical/en zymatic cleavage and synthesis of degenerate oligonucleotide primers. These primers were used for initial cloning of the cDNA from rat pancr eas by PCR. The predicted protein sequence of the cDNA clone contained the five partial peptide sequences obtained from the purified protein . Seven putative transmembrane domains suggest its membership in the g uanine nucleotide-binding regulatory protein-coupled receptor superfam ily. In vitro transcripts of the cDNA clone were functionally expresse d in Xenopus oocytes and displayed the expected agonist and antagonist specificity.