OXGR1

OXGR1, i.e., 2-oxoglutarate receptor 1 (also known as GPR99, cysteinyl leukotriene receptor E, i.e., CysLTE, and cysteinyl leukotriene receptor 3, i.e., CysLT3) is a G protein-coupled receptor located on the surface membranes of certain cells. It functions by binding one of its ligands and thereby becoming active in triggering pre-programmed responses in its parent cells. OXGR1 has been shown to be activated by α-ketoglutarate, itaconate, and three cysteinyl-containing leukotrienes (abbreviated as CysLTs), leukotriene E4 (i.e., LTE4), LTC4, and LTD4. α-Ketoglutarate and itaconate are the dianionic forms of α-ketoglutaric acid and itaconic acid, respectively. α-Ketoglutaric and itaconic acids are short-chain dicarboxylic acids that have two carboxyl groups (notated as -CO2H) both of which are bound to hydrogen (i.e., H+). However, at the basic pH levels (i.e., pH>7) in virtually all animal tissues, α-ketoglutaric acid and itaconic acid exit almost exclusively as α-ketoglutarate and itaconate, i.e., with their carboxy residues being negatively charged (notated as -CO2

−

{\displaystyle ^{-}}

), because they are not bound to H+ (see Conjugate acid-base theory). It is α-ketoglutarate and itaconate, not α-ketoglutaric or itaconic acids, which activate OXGR1.

History

In 2001, a human gene projected to code for a G protein-coupled receptor (i.e., a receptor that stimulates cells by activating G proteins) was identified. Its protein product was classified as an orphan receptor, i.e., a receptor whose activating ligand and function are unknown. The projected amino acid sequence of the protein encoded by this gene bore similarities to the purinergic receptor, P2Y1, and therefore might, like P2Y1, be a receptor for purines.