Orphan GPCR (孤儿 G 蛋白偶联受体)

Orphan GPCRs (orphan G protein-coupled receptors) are receptors lacking endogenous ligands. GPCRs are th largest family of transmembrane receptors and have over the past decades developed into highly successful drug targets. However, many GPCRs are still orphans and the function is enigmatic. Orphan GPCRs account for ∼30% of the ∼400 non-olfactory human GPCRs. In terms of orphan GPCR ligands, initial efforts focused on identifying novel neuropeptides since orphan GPCR expression was located primarily in the brain. G protein coupling of unliganded orphan GPCRs—GPR22, GPR137b, GPR88, GPR156, GPR158, GPR179, GPRC5D and GPRC6A—with pathophysiological association were accurately detected using luciferase reporter assays^[1][2].