G protein-coupled receptor 20, member of the class A family of seven-transmembrane G protein-coupled receptors
Orphan GPR20 is phylogenetically related to the P2Y family of purinergic G protein-coupled receptors. The P2Y receptor family is composed of eight subtypes, which are activated by naturally occurring extracellular nucleotides such as ATP, ADP, UTP, UDP, and UDP-glucose. GPR20 has been shown to constitutively activate G(i) proteins in the absence of a ligand; however its functional role is not known. GPR20 is a member of the class A G protein-coupled receptor superfamily, which all have a common structural architecture comprising of seven-transmembrane (TM) alpha-helices interconnected by three extracellular and three intracellular loops. A common feature of GPCR signaling is agonist-induced conformational changes in the receptors, which then activate the heterotrimeric G proteins. G-proteins regulate a variety of cellular functions including metabolic enzymes, ion channels, and transporters, among many others.