title: Identification of the GPR55 agonist binding site using a novel set of high-potency GPR55 selective ligands.
abstract: Marijuana is the most widely abused illegal drug, and its spectrum of effects suggests that several receptors are responsible for the activity. Two cannabinoid receptor subtypes, CB1 and CB2, have been identified, but the complex pharmacological properties of exogenous cannabinoids and endocannabinoids are not fully explained by their signaling. The orphan receptor GPR55 binds a subset of CB1 and CB2 ligands and has been proposed as a cannabinoid receptor. This designation, however, is controversial as a result of recent studies in which lysophosphatidylinositol (LPI) was identified as a GPR55 agonist. Defining a biological role for GPR55 requires GPR55 selective ligands that have been unavailable. From a β-arrestin, high-throughput, high-content screen of 300000 compounds run in collaboration with the Molecular Libraries Probe Production Centers Network initiative (PubChem AID1965), we identified potent GPR55 selective agonists. By modeling of the GPR55 activated state, we compared the GPR55 binding conformations of three of the novel agonists obtained from the screen, CID1792197, CID1172084, and CID2440433 (PubChem Compound IDs), with that of LPI. Our modeling indicates the molecular shapes and electrostatic potential distributions of these agonists mimic those of LPI; the GPR55 binding site accommodates ligands that have inverted-L or T shapes with long, thin profiles that can fit vertically deep in the receptor binding pocket while their broad head regions occupy a horizontal binding pocket near the GPR55 extracellular loops. Our results will allow the optimization and design of second-generation GPR55 ligands and provide a means for distinguishing GPR55 selective ligands from those interacting with cannabinoid receptors.
authors.affiliation: Center for Drug Discovery, University of North Carolina, Greensboro, North Carolina 27402, USA.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Kotsikorou
authors.forename: Karla E
authors.initials: KE
authors.lastname: Madrigal
authors.forename: Dow P
authors.initials: DP
authors.lastname: Hurst
authors.forename: Haleli
authors.initials: H
authors.lastname: Sharir
authors.forename: Diane L
authors.initials: DL
authors.lastname: Lynch
authors.forename: Susanne
authors.initials: S
authors.lastname: Heynen-Genel
authors.forename: Loribelle B
authors.initials: LB
authors.lastname: Milan
authors.forename: Thomas D Y
authors.initials: TD
authors.lastname: Chung
authors.forename: Herbert H
authors.initials: HH
authors.lastname: Seltzman
authors.forename: Yushi
authors.initials: Y
authors.lastname: Bai
authors.forename: Marc G
authors.initials: MG
authors.lastname: Caron
authors.forename: Larry
authors.initials: L
authors.lastname: Barak
authors.forename: Mary E
authors.initials: ME
authors.lastname: Abood
authors.forename: Patricia H
authors.initials: PH
authors.lastname: Reggio
mesh_terms: D000595:Amino Acid Sequence; D019390:Arrestins / Q000737:chemistry / Q000235:genetics; D001665:Binding Sites; D045744:Cell Line, Tumor; D018360:Crystallography, X-Ray; D004305:Dose-Response Relationship, Drug; D015195:Drug Design; D057809:HEK293 Cells; D006801:Humans; D008024:Ligands; D008956:Models, Chemical; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000737:chemistry* / Q000378:metabolism; D055672:Static Electricity; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; C524885:GPR55 protein, human; D008024:Ligands; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled; D000071557:beta-Arrestins