GPR31 and GPR151 are activated under acidic conditions.

Recent studies have revealed that not only proton-sensing channels, but also one family of G protein-coupled receptors (GPCRs) comprising OGR1, GPR4, G2A and TDAG8 are responsible for the sensing of extracellular protons, or pH. Here, we report that two other GPCRs, GPR31 and GPR151, were also activated in acidic condition. Elevated pH of assay mixtures resulted in a remarkable increase in [35S]GTPγS binding by GPR31-Giα and GPR151-Giα fusion proteins in a narrow range between pH 6 and 5.

A novel partial agonist of GPBA reduces blood glucose level in a murine glucose tolerance test.

GPBA is a G protein-coupled receptor that is activated by bile acids. Because activation of GPBA leads to increased cAMP levels and secretion of incretins and insulin, GPBA has been proposed as a promising drug target for the treatment of metabolic syndrome. Previously, we have developed a ligand-screening system to identify novel agonists of GPBA by means of a fusion protein of GPBA with G protein stimulatory α subunit (Gsα) and by a [S]GTPγS-binding assay.