title: The endocannabinoids anandamide and virodhamine modulate the activity of the candidate cannabinoid receptor GPR55.
abstract: The role of cannabinoid receptors in inflammation has been the topic of many research endeavors. Despite this effort, to date the involvement of the endocannabinoid system (ECS) in inflammation remains obscure. The ambiguity of cannabinoid involvement may be explained by the existence of cannabinoid receptors, other than CB(1) and CB(2), or a consequence of interaction of endocannabinoids with other signaling systems. GPR55 has been proposed to be a cannabinoid receptor; however the interaction of the endocannabinoid system with GPR55 remains elusive. Consequently this study set about to examine the effects of the endocannabinoids, anandamide (AEA) and virodhamine, on GPR55 mediated signaling. Specifically, we assessed changes in β-arrestin2 (βarr2) distribution and GPR55 receptor internalization following activation by lysophosphatidylinositol (LPI), the synthetic cannabinoid ligand SR141716A, and new selective synthetic GPR55 agonists. Data obtained from the experiments presented herein demonstrate that AEA and virodhamine modulate agonist-mediated recruitment of βarr2. AEA and virodhamine act as partial agonists; enhancing the agonist effect at low concentrations and inhibiting it at high concentrations. Furthermore, both virodhamine and AEA significantly attenuated agonist-induced internalization of GPR55. These effects are attributed to the expression of GPR55, and not CB(1) and CB(2) receptors, as we have established negligible expression of CB(1) and CB(2) in these GPR55-transfected U2OS cells. The identification of select endocannabinoids as GPR55 modulators will aide in elucidating the function of GPR55 in the ECS.
authors.affiliation: Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
authors.forename: Haleli
authors.initials: H
authors.lastname: Sharir
authors.forename: Linda
authors.initials: L
authors.lastname: Console-Bram
authors.forename: Christina
authors.initials: C
authors.lastname: Mundy
authors.forename: Steven N
authors.initials: SN
authors.lastname: Popoff
authors.forename: Ankur
authors.initials: A
authors.lastname: Kapur
authors.forename: Mary E
authors.initials: ME
authors.lastname: Abood
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology*; D019390:Arrestins / Q000378:metabolism; D016466:CHO Cells; D063386:Cannabinoid Receptor Agonists / Q000494:pharmacology*; D063385:Cannabinoid Receptor Modulators / Q000494:pharmacology*; D002186:Cannabinoids / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D063388:Endocannabinoids / Q000494:pharmacology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007150:Immunohistochemistry; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D018613:Microscopy, Confocal; D053284:Polyunsaturated Alkamides / Q000494:pharmacology*; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D060888:Real-Time Polymerase Chain Reaction; D043884:Receptor, Cannabinoid, CB1 / Q000187:drug effects; D043885:Receptor, Cannabinoid, CB2 / Q000187:drug effects; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors / Q000187:drug effects*; D000071557:beta-Arrestins
chemical_list: D001095:Arachidonic Acids; D019390:Arrestins; D063386:Cannabinoid Receptor Agonists; D063385:Cannabinoid Receptor Modulators; D002186:Cannabinoids; D063388:Endocannabinoids; C524885:GPR55 protein, human; D053284:Polyunsaturated Alkamides; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled; D000071557:beta-Arrestins; C456739:virodhamine; D049452:Green Fluorescent Proteins; D012313:RNA; D007770:L-Lactate Dehydrogenase; C078814:anandamide