title: A cluster of Ser/Thr residues at the C-terminus of mu-opioid receptor is required for G protein-coupled receptor kinase 2-mediated desensitization.
abstract: To investigate the functional role of G protein-coupled receptor kinases (GRK) in homologous desensitization of the mu-opioid receptor, human embryonic kidney (HEK) 293 cells, which express a significant level of GRK2, were stably transfected with the cDNA encoding the rat mu-opioid receptor. Wild-type mu-opioid receptors developed homologous desensitization after 30 min pretreatment with DAMGO ([D-Ala2,N-methyl-Phe4,Gly-ol5]enkephalin), a specific mu-opioid receptor agonist. The ability of mu-opioid receptors to develop homologous desensitization was greatly impaired following the transfection of a cDNA fragment encoding the GRK2(495-689) polypeptide, which is believed to block Gbetagamma-mediated transduction events including the membrane translocation and activation of GRK2. The mu(Cdelta45) receptor, a deletion mutant that lacks 45 C-terminal amino acids, failed to exhibit homologous desensitization after 30 min pretreatment of DAMGO. The mu(Cdelta41) receptor, which differs from the mu(Cdelta45) receptor by having four more Ser/Thr residues (Thr354Ser355Ser356Thr357), developed GRK2-mediated desensitization. These results suggest that homologous desensitization of rat mu-opioid receptors results from the activation of GRK2 and that a cluster of Ser/Thr residues (Thr354Ser355Ser356Thr357) at the intracellular carboxyl tail plays an important role in GRK2-mediated mu-opioid receptor desensitization.
authors.affiliation: Department of Physiology, Chang Gung University School of Medicine, Tao-Yuan, Taiwan. hlwns@mail.cgu.edu.tw
authors.forename: H L
authors.initials: HL
authors.lastname: Wang
mesh_terms: D000701:Analgesics, Opioid / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D004361:Drug Tolerance; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000378:metabolism / Q000494:pharmacology; D054769:G-Protein-Coupled Receptor Kinase 2; D006801:Humans; D009270:Naloxone / Q000378:metabolism; D009292:Narcotic Antagonists / Q000378:metabolism; D051381:Rats; D017450:Receptors, Opioid, mu / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism*; D014162:Transfection / Q000235:genetics; D051552:beta-Adrenergic Receptor Kinases
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D013912:Threonine; D009270:Naloxone; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases; C496569:Grk2 protein, rat; D051552:beta-Adrenergic Receptor Kinases; D054769:G-Protein-Coupled Receptor Kinase 2