title: What is the natural ligand of GPR55?
abstract: GPR55 is a seven transmembrane G protein-coupled receptor and was originally identified as a putative third cannabinoid receptor. Recently, lysophosphatidylinositol (LPI) was reported to be a GPR55 ligand. Stimulation of GPR55 by LPI activates G(12/13) and G(q/11) proteins, induces phosphorylation of the extracellular signal-regulated kinase and increases intracellular calcium concentration. Lysophospholipids are molecularly quite diverse across species and tissues. A recent report showed that the predominant fatty acyl moiety of LPI in rat brain is stearic acid followed by arachidonic acid. The biological activity of arachidonic acid-containing LPI species towards GPR55 was shown to be markedly higher than that of LPI species containing other fatty acyl groups, suggesting that 2-arachidonolyl LPI is the most likely natural ligand of GPR55.
authors.affiliation: Department of Medical Biochemistry, Graduate School of Medicine, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-85823, Japan. okuno@biochem1.med.kyushu-u.ac.jp
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Okuno
authors.forename: Takehiko
authors.initials: T
authors.lastname: Yokomizo
mesh_terms: D000818:Animals; D002186:Cannabinoids / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008024:Ligands; D015394:Molecular Structure; D051381:Rats; D043882:Receptors, Cannabinoid / Q000737:chemistry / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry / Q000378:metabolism*
chemical_list: C527491:Adgrg1 protein, rat; D002186:Cannabinoids; C524885:GPR55 protein, human; D008024:Ligands; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled