title: Enantiospecific Allosteric Modulation of Cannabinoid 1 Receptor.
abstract: The cannabinoid 1 receptor (CB1R) is one of the most widely expressed metabotropic G protein-coupled receptors in brain, and its participation in various (patho)physiological processes has made CB1R activation a viable therapeutic modality. Adverse psychotropic effects limit the clinical utility of CB1R orthosteric agonists and have promoted the search for CB1R positive allosteric modulators (PAMs) with the promise of improved drug-like pharmacology and enhanced safety over typical CB1R agonists. In this study, we describe the synthesis and in vitro and ex vivo pharmacology of the novel allosteric CB1R modulator GAT211 (racemic) and its resolved enantiomers, GAT228 (R) and GAT229 (S). GAT211 engages CB1R allosteric site(s), enhances the binding of the orthosteric full agonist [3H]CP55,490, and reduces the binding of the orthosteric antagonist/inverse agonist [3H]SR141716A. GAT211 displayed both PAM and agonist activity in HEK293A and Neuro2a cells expressing human recombinant CB1R (hCB1R) and in mouse-brain membranes rich in native CB1R. GAT211 also exhibited a strong PAM effect in isolated vas deferens endogenously expressing CB1R. Each resolved and crystallized GAT211 enantiomer showed a markedly distinctive pharmacology as a CB1R allosteric modulator. In all biological systems examined, GAT211's allosteric agonist activity resided with the R-(+)-enantiomer (GAT228), whereas its PAM activity resided with the S-(-)-enantiomer (GAT229), which lacked intrinsic activity. These results constitute the first demonstration of enantiomer-selective CB1R positive allosteric modulation and set a precedent whereby enantiomeric resolution can decisively define the molecular pharmacology of a CB1R allosteric ligand.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Laprairie
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University , Boston, Massachusetts 02115, United States.
authors.forename: Pushkar M
authors.initials: PM
authors.lastname: Kulkarni
authors.affiliation: Naval Research Laboratory , Code 6930, 4555 Overlook Avenue, Washington, D.C. 20375, United States.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Deschamps
authors.forename: Melanie E M
authors.initials: MEM
authors.lastname: Kelly
authors.affiliation: Center for Drug Discovery; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Department of Chemistry and Chemical Biology, College of Science, and Health Sciences Entrepreneurs; Northeastern University , Boston, Massachusetts 02115, United States.
authors.forename: David R
authors.initials: DR
authors.lastname: Janero
authors.affiliation: School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen , Aberdeen AB25 2ZD, Scotland, U.K.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Cascio
authors.affiliation: School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen , Aberdeen AB25 2ZD, Scotland, U.K.
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Stevenson
authors.affiliation: School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen , Aberdeen AB25 2ZD, Scotland, U.K.
authors.forename: Roger G
authors.initials: RG
authors.lastname: Pertwee
authors.affiliation: Department of Pharmacology, University of North Carolina School of Medicine , Chapel Hill, North Carolina 27599, United States.
authors.forename: Terrence P
authors.initials: TP
authors.lastname: Kenakin
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Denovan-Wright
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University , Boston, Massachusetts 02115, United States.
authors.forename: Ganesh A
authors.identifier: 0000-0002-7468-8819
authors.initials: GA
authors.lastname: Thakur
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects; D000495:Allosteric Site / Q000187:drug effects; D000818:Animals; D063386:Cannabinoid Receptor Agonists / Q000138:chemical synthesis* / Q000737:chemistry* / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry* / Q000494:pharmacology*; D007536:Isomerism; D051379:Mice; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists* / Q000187:drug effects*
chemical_list: C000626905:3-(2-nitro-1-phenylethyl)-2-phenyl-1H-indole; D063386:Cannabinoid Receptor Agonists; D007211:Indoles; D043884:Receptor, Cannabinoid, CB1
keywords: 7-transmembrane receptor; Allosteric regulation; G-protein-coupled receptor; cannabinoid; cellular signaling; central nervous system; ligand bias; molecular pharmacology; probe dependence; receptor activation; therapeutics discovery