G protein-coupled receptor 151, member of the class A family of seven-transmembrane G protein-coupled receptors
G-protein coupled receptor 151 (GRP151) is an orphan receptor of unknown function. Its expression is conserved in habenular axonal projections of vertebrates and may be a promising novel target for psychiatric drug development. GPR151 shows high sequence similarity with galanin receptors (GALR). GPR151 is a member of the class A rhodopsin-like GPCRs, which represent a widespread protein family that includes the light-sensitive rhodopsin as well as receptors for biogenic amines, lipids, nucleotides, odorants, peptide hormones, and a variety of other ligands. All GPCRs have a common structural architecture comprising of seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops. A general feature of GPCR signaling is agonist-induced conformational changes in the receptors, leading to activation of the heterotrimeric G proteins, which consist of the guanine nucleotide-binding G-alpha subunit and the dimeric G-beta-gamma subunits. The activated G proteins then bind to and activate numerous downstream effector proteins, which generate second messengers that mediate a broad range of cellular and physiological processes.