title: Pharmacology of GPR55 in yeast and identification of GSK494581A as a mixed-activity glycine transporter subtype 1 inhibitor and GPR55 agonist.
abstract: 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 CB(1) and CB(2) 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 (pEC(50) = 6.8) over GlyT1 (pIC(50) = 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.
authors.affiliation: Screening and Compound Profiling, Medicines Research Centre, GlaxoSmithKline, Gunnels Wood Road, Stevenage, Hertfordshire SG1 2NY, UK. andrew.j.brown@gsk.com
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Brown
authors.forename: Dion A
authors.initials: DA
authors.lastname: Daniels
authors.forename: Mumta
authors.initials: M
authors.lastname: Kassim
authors.forename: Sue
authors.initials: S
authors.lastname: Brown
authors.forename: Carl P
authors.initials: CP
authors.lastname: Haslam
authors.forename: Victoria R
authors.initials: VR
authors.lastname: Terrell
authors.forename: Jason
authors.initials: J
authors.lastname: Brown
authors.forename: Paula L
authors.initials: PL
authors.lastname: Nichols
authors.forename: Penny C
authors.initials: PC
authors.lastname: Staton
authors.forename: Alan
authors.initials: A
authors.lastname: Wise
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Dowell
mesh_terms: D004305:Dose-Response Relationship, Drug; D050487:Glycine Plasma Membrane Transport Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D010879:Piperazines / Q000737:chemistry* / Q000494:pharmacology*; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000378:metabolism; D015003:Yeasts
chemical_list: C524885:GPR55 protein, human; D050487:Glycine Plasma Membrane Transport Proteins; D010879:Piperazines; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled