cholecystokinin receptor type B, member of the class A family of seven-transmembrane G protein-coupled receptors
Cholecystokinin receptors (CCK-AR and CCK-BR) are a group of G-protein coupled receptors which bind the peptide hormones cholecystokinin (CCK) or gastrin. CCK, which facilitates digestion in the small intestine, and gastrin, a major regulator of gastric acid secretion, are highly similar peptides. Like gastrin, CCK is a naturally-occurring linear peptide that is synthesized as a preprohormone, then proteolytically cleaved to form a family of peptides with the common C-terminal sequence (Gly-Trp-Met-Asp-Phe-NH2), which is required for full biological activity. CCK-AR (type A, alimentary; also known as CCK1R) is found abundantly on pancreatic acinar cells and binds only sulfated CCK-peptides with very high affinity, whereas CCK-BR (type B, brain; also known as CCK2R), the predominant form in the brain and stomach, binds CCK or gastrin and discriminates poorly between sulfated and non-sulfated peptides. CCK is implicated in regulation of digestion, appetite control, and body weight, and is involved in neurogenesis via CCK-AR. There is some evidence to support that CCK and gastrin, via their receptors, are involved in promoting cancer development and progression, acting as growth and invasion factors.