title: Type 1 cannabinoid receptor ligands display functional selectivity in a cell culture model of striatal medium spiny projection neurons.
abstract: Modulation of type 1 cannabinoid receptor (CB1) activity has been touted as a potential means of treating addiction, anxiety, depression, and neurodegeneration. Different agonists of CB1 are known to evoke varied responses in vivo. Functional selectivity is the ligand-specific activation of certain signal transduction pathways at a receptor that can signal through multiple pathways. To understand cannabinoid-specific functional selectivity, different groups have examined the effect of individual cannabinoids on various signaling pathways in heterologous expression systems. In the current study, we compared the functional selectivity of six cannabinoids, including two endocannabinoids (2-arachidonyl glycerol (2-AG) and anandamide (AEA)), two synthetic cannabinoids (WIN55,212-2 and CP55,940), and two phytocannabinoids (cannabidiol (CBD) and Δ(9)-tetrahydrocannabinol (THC)) on arrestin2-, Gα(i/o)-, Gβγ-, Gα(s)-, and Gα(q)-mediated intracellular signaling in the mouse STHdh(Q7/Q7) cell culture model of striatal medium spiny projection neurons that endogenously express CB1. In this system, 2-AG, THC, and CP55,940 were more potent mediators of arrestin2 recruitment than other cannabinoids tested. 2-AG, AEA, and WIN55,212-2, enhanced Gα(i/o) and Gβγ signaling, with 2-AG and AEA treatment leading to increased total CB1 levels. 2-AG, AEA, THC, and WIN55,212-2 also activated Gα(q)-dependent pathways. CP55,940 and CBD both signaled through Gα(s). CP55,940, but not CBD, activated downstream Gα(s) pathways via CB1 targets. THC and CP55,940 promoted CB1 internalization and decreased CB1 protein levels over an 18-h period. These data demonstrate that individual cannabinoids display functional selectivity at CB1 leading to activation of distinct signaling pathways. To effectively match cannabinoids with therapeutic goals, these compounds must be screened for their signaling bias.
authors.affiliation: From the Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Laprairie
authors.affiliation: From the Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Amina M
authors.initials: AM
authors.lastname: Bagher
authors.affiliation: From the Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Melanie E M
authors.initials: ME
authors.lastname: Kelly
authors.affiliation: From the Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Denis J
authors.initials: DJ
authors.lastname: Dupré
authors.affiliation: From the Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada emdenova@dal.ca.
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Denovan-Wright
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology; D019393:Arrestin / Q000235:genetics / Q000378:metabolism; D048588:Benzoxazines / Q000494:pharmacology; D015153:Blotting, Western; D063386:Cannabinoid Receptor Agonists / Q000494:pharmacology*; D002186:Cannabinoids / Q000494:pharmacology*; D002478:Cells, Cultured; D003342:Corpus Striatum / Q000166:cytology / Q000378:metabolism; D003511:Cyclohexanols / Q000494:pharmacology; D049229:Dendritic Spines / Q000378:metabolism; D013759:Dronabinol / Q000494:pharmacology; D063388:Endocannabinoids / Q000494:pharmacology; D031541:Fluorescence Resonance Energy Transfer; D019204:GTP-Binding Proteins / Q000378:metabolism; D005989:Glycerides / Q000494:pharmacology; D008024:Ligands; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D053284:Polyunsaturated Alkamides / Q000494:pharmacology; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists* / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D001095:Arachidonic Acids; D019393:Arrestin; D048588:Benzoxazines; D063386:Cannabinoid Receptor Agonists; D002186:Cannabinoids; D003511:Cyclohexanols; D063388:Endocannabinoids; D005989:Glycerides; D008024:Ligands; D008164:Luminescent Proteins; D009025:Morpholines; D009281:Naphthalenes; D053284:Polyunsaturated Alkamides; D043884:Receptor, Cannabinoid, CB1; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D013759:Dronabinol; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; C094503:glyceryl 2-arachidonate; D019204:GTP-Binding Proteins; C078814:anandamide
keywords: 2-Arachidonylglycerol; Anandamide (N-Arachidonoylethanolamine) (AEA); Arrestin; Bioluminescence Resonance Energy Transfer (BRET); Cannabidiol; Cannabinoid; Cannabinoid Receptor; Cell Signaling; Neurobiology; Δ9-tetrahydrocannabinol (THC)