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What is the natural ligand of GPR55?
Toshiaki Okuno1, Takehiko Yokomizo
1Department 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
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.
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