MOLECULAR AND PHARMACOLOGICAL CHARACTERIZATION OF THE HUMAN CCKB RECEPTOR

The human cholecystokinin B (CCKB) receptor has been isolated from a h uman temporal cortex cDNA library. Transient transfection of the recep tor into COS-M6 cells resulted in high specific binding of I-125-sulph ated CCK-8 labelled with Bolton and Hunter Reagent (K-D = 31 pM). Comp etition experiments yielded the expected CCKB receptor ligand binding profile for agonists and antagonists. Similar results were obtained in human small cell lung carcinoma cells, which express an endogenous CC KB receptor. Extensive functional characterization of the receptor was performed in stably transfected HeLa cells using intracellular calciu m imaging and microphysiometry techniques. Molecular analysis of the h uman CCKB receptor using Southern blotting of genomic DNA suggests the presence of a single gene for the CCKB receptor with no closely relat ed homologues. This was confirmed by the polymerase chain reaction clo ning of identical receptor coding sequences from human small cell lung carcinoma cells and human gastric enterochromaffin-like cell-oma (ECL oma) tissue.