GPR91 (formerly known as P2U2) is a G protein-coupled, dicarboxylic acid succinate receptor. It has a high level of expression in the kidney, predominantly in the proximal tubules, and localizes to the plasma membrane. It has also been found at low levels in the liver and the spleen. GPR91 functions as a citric acid cycle intermediate succinate receptor. Two signaling pathways result from GPR91 activation, the pertussis-toxin-sensitive Gi/Go pathway and the pertussis-toxin-insensitive Gq pathway. Four amino acid residues are necessary for GPR91 activation by succinate: Arg 99, His 103, Arg 252 and Arg 281. GPR91 plays an important role in the succinate-induced hypertensive effect and may be involved in renovascular hypertension, a disease linked to
diabetes, renal failure and atherosclerosis.