proton-sensing G protein-coupled receptor 4, member of the class A family of seven-transmembrane G protein-coupled receptors
G-protein-coupled receptor 4 (GPR4) is a member of the proton-sensing G-protein-coupled receptor (GPCR) family which also includes the G2 accumulation receptor (G2A, also known as GPR132), the T cell death associated gene-8 receptor (TDAG8, GPR65), ovarian cancer G-protein receptor 1 (OGR-1, GPR68), and G-protein-coupled receptor 4 (GPR4). Proton-sensing G-protein coupled receptors sense pH of 7.6 to 6.0 and mediates a variety of biological activities in neutral and mildly acidic pH conditions, whereas the acid-sensing ionotropic ion channels typically sense strong acidic pH. GPR4 overexpression in melanoma cells was shown to reduce cell migration, membrane ruffling, and cell spreading under acidic pH conditions. Activation of GPR4 via extracellular acidosis is coupled to the G(s), G(q), and G(12/13) pathways.