TY - JOUR T1 - A Selective Antagonist Reveals a Potential Role of G Protein–Coupled Receptor 55 in Platelet and Endothelial Cell Function JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 54 LP - 66 DO - 10.1124/jpet.113.204180 VL - 346 IS - 1 AU - Julia Kargl AU - Andrew J. Brown AU - Liisa Andersen AU - Georg Dorn AU - Rudolf Schicho AU - Maria Waldhoer AU - Akos Heinemann Y1 - 2013/07/01 UR - http://jpet.aspetjournals.org/content/346/1/54.abstract N2 - The G protein–coupled receptor 55 (GPR55) is a lysophosphatidylinositol (LPI) receptor that is also responsive to certain cannabinoids. Although GPR55 has been implicated in several (patho)physiologic functions, its role remains enigmatic owing mainly to the lack of selective GPR55 antagonists. Here we show that the compound CID16020046 ((4-[4-(3-hydroxyphenyl)-3-(4-methylphenyl)-6-oxo-1H,4H,5H,6H-pyrrolo[3,4-c]pyrazol-5-yl] benzoic acid) is a selective GPR55 antagonist. In yeast cells expressing human GPR55, CID16020046 antagonized agonist-induced receptor activation. In human embryonic kidney (HEK293) cells stably expressing human GPR55, the compound behaved as an antagonist on LPI-mediated Ca2+ release and extracellular signal-regulated kinases activation, but not in HEK293 cells expressing cannabinoid receptor 1 or 2 (CB1 or CB2). CID16020046 concentration dependently inhibited LPI-induced activation of nuclear factor of activated T-cells (NFAT), nuclear factor κ of activated B cells (NF-κB) and serum response element, translocation of NFAT and NF-κB, and GPR55 internalization. It reduced LPI-induced wound healing in primary human lung microvascular endothelial cells and reversed LPI-inhibited platelet aggregation, suggesting a novel role for GPR55 in platelet and endothelial cell function. CID16020046 is therefore a valuable tool to study GPR55-mediated mechanisms in primary cells and tissues. ER -