title: RGS9-2 is a negative modulator of mu-opioid receptor function.
abstract: Regulators of G-protein signaling (RGS) 9-2 is a striatal enriched protein that controls G protein coupled receptor signaling duration by accelerating Galpha subunit guanosine triphosphate hydrolysis. We have previously demonstrated that mice lacking the RGS9 gene show enhanced morphine analgesia and delayed development of tolerance. Here we extend these studies to understand the mechanism via which RGS9-2 modulates opiate actions. Our data suggest that RGS9-2 prevents several events triggered by mu-opioid receptor (MOR) activation. In transiently transfected PC12 cells, RGS9-2 delays agonist induced internalization of epitope HA-tagged mu-opioid receptor. This action of RGS9-2 requires localization of the protein near the cell membrane. Co-immunoprecipitation studies reveal that RGS9-2 interacts with HA-tagged mu-opioid receptor, and that this interaction is enhanced by morphine treatment. In addition, morphine promotes the association of RGS9-2 with another essential component of MOR desensitization, beta-arrestin-2. We also show that over-expression of RGS9-2 prevents opiate-induced extracellular signal-regulated kinase phosphorylation. Our data indicate that RGS9-2 plays an essential role in opiate actions, by negatively modulating MOR downstream signaling as well as the rate of MOR endocytosis.
authors.affiliation: Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece.
authors.forename: Kassi
authors.initials: K
authors.lastname: Psifogeorgou
authors.forename: Paraskevi
authors.initials: P
authors.lastname: Papakosta
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Russo
authors.forename: Rachael L
authors.initials: RL
authors.lastname: Neve
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kardassis
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Gold
authors.forename: Venetia
authors.initials: V
authors.lastname: Zachariou
mesh_terms: D000818:Animals; D019390:Arrestins / Q000378:metabolism; D001522:Behavior, Animal / Q000502:physiology; D015153:Blotting, Western; D001923:Brain Chemistry / Q000187:drug effects; D002478:Cells, Cultured; D004705:Endocytosis / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology; D010147:Pain Measurement / Q000187:drug effects; D010766:Phosphorylation; D020710:RGS Proteins / Q000502:physiology*; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000502:physiology*; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
chemical_list: C000605258:Arrb2 protein, mouse; D019390:Arrestins; D009294:Narcotics; D020710:RGS Proteins; D017450:Receptors, Opioid, mu; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; C116925:regulator of g-protein signaling 9; D009020:Morphine; D048049:Extracellular Signal-Regulated MAP Kinases