PT  - JOURNAL ARTICLE
AU  - Andrew J. Brown
AU  - Dion A. Daniels
AU  - Mumta Kassim
AU  - Sue Brown
AU  - Carl P. Haslam
AU  - Victoria R. Terrell
AU  - Jason Brown
AU  - Paula L. Nichols
AU  - Penny C. Staton
AU  - Alan Wise
AU  - Simon J. Dowell
TI  - Pharmacology of GPR55 in Yeast and Identification of GSK494581A as a Mixed-Activity Glycine Transporter Subtype 1 Inhibitor and GPR55 Agonist
AID  - 10.1124/jpet.110.172650
DP  - 2011 Apr 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 236--246
VI  - 337
IP  - 1
4099  - http://jpet.aspetjournals.org/content/337/1/236.short
4100  - http://jpet.aspetjournals.org/content/337/1/236.full
SO  - J Pharmacol Exp Ther2011 Apr 01; 337
AB  - GPR55 is a G protein-coupled receptor activated by l-α-lysophosphatidylinositol and suggested to have roles in pain signaling, bone morphogenesis, and possibly in vascular endothelial cells. It has affinity for certain cannabinoids (molecules that interact with the cannabinoid CB1 and CB2 receptors), but investigation of its functional role in cell-based systems and in tissue has been limited by a lack of selective pharmacological tools. Here, we present our characterization of GPR55 in the yeast Saccharomyces cerevisiae and in human embryonic kidney (HEK293) cells. We describe GSK494581A (1-{2-fluoro-4-[1-(methyloxy)ethyl]phenyl}-4-{[4′-fluoro-4-(methylsulfonyl)-2-biphenylyl]carbonyl}piperazine), a selective small-molecule ligand of GPR55 identified through diversity screening. GSK494581A is one of a series of benzoylpiperazines originally identified and patented as inhibitors of the glycine transporter subtype 1 (GlyT1). The structure–activity relationship between GPR55 and GlyT1 is divergent across this series. The most GPR55-selective example is GSK575594A (3-fluoro-4-(4-{[4′-fluoro-4-(methylsulfonyl)-2-biphenylyl]carbonyl}-1-piperazinyl)aniline), which is approximately 60-fold selective for GPR55 (pEC50 = 6.8) over GlyT1 (pIC50 = 5.0). Several exemplars with activity at GPR55 and GlyT1 have been profiled at a broad range of other molecular targets and are inactive at cannabinoid receptors and all other targets tested. The benzoylpiperazine agonists activate human GPR55 but not rodent GPR55, suggesting that the relatively low level of sequence identity between these orthologs (75%) translates to important functional differences in the ligand-binding site.