G protein-coupled receptor 15, member of the class A family of seven-transmembrane G protein-coupled receptors
GPR15, also called as Brother of Bonzo (BOB), is an orphan G-protein coupled receptor that was originally identified as a co-receptor for human immunodeficiency virus. GPR15 is upregulated in patients with rheumatoid arthritis and shares high sequence homology with angiotensin II type AT1 and AT2 receptors; however, its endogenous ligand is unknown. GPR15 controls homing of T cells, especially FOXP3(+) regulatory T cells, to the large intestine mucosa and thereby mediates local immune homeostasis. Moreover, GRP15-deficient mice were shown to be prone to develop more severe large intestine inflammation.