title: Differential effects of opioid agonists on G protein expression in CHO cells expressing cloned human opioid receptors.
abstract: Recent evidence indicates that agonist ligands of G protein coupled receptors (GPCR) can activate different signaling systems. Such "agonist-directed" signaling also occurs with opioid receptors. Previous work from our laboratory showed that chronic morphine, but not DAMGO, up-regulates the expression of Galpha12 and that both morphine and DAMGO decreased Galphai3 expression in CHO cells expressing the cloned human mu opioid receptor. In this study, we tested the hypothesis that chronic opioid regulation of G protein expression is agonist-directed. Following a 20h treatment of CHO cells expressing the cloned human mu (hMOR-CHO), delta (hDOR-CHO) or kappa (hKOR-CHO) opioid receptors with various opioid agonists, we determined the expression level of Galpha12 and Galphai3 by Western blots. Among five mu agonists (morphine, etorphine, DADLE, DAMGO, herkinorin) tested with hMOR-CHO cells, only chronic morphine and etorphine up-regulated Galpha12 expression. All five mu agonists decreased Galphai3 expression. Among six delta agonists (SNC80, DPDPE, deltorphin-1, morphine, DADLE, etorphine) tested with hDOR-CHO cells, all six agonists down-regulated Galphai3 expression or moderately up-regulated Galpha12 expression. Among five kappa agonists, ((-)-ethylketocyclazocine, salvinorin A, U69,593, etorphine, (-)-U50,488) tested with hKOR-CHO cells, only chronic (-)-U50,488 and (-)-EKC up-regulated Galpha12 expression. All kappa agonists decreased Galphai3 expression. These data demonstrate that chronic opioid agonist regulation of G protein expression depends not only on the agonist tested, but also on the type of opioid receptor expressed in a common cellular host, providing additional evidence for agonist-directed signaling.
authors.affiliation: Clinical Psychopharmacology Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, DHHS, Baltimore, MD 21224, USA.
authors.forename: Heng
authors.initials: H
authors.lastname: Xu
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Wang
authors.forename: John S
authors.initials: JS
authors.lastname: Partilla
authors.forename: Kristen
authors.initials: K
authors.lastname: Bishop-Mathis
authors.forename: Tova S
authors.initials: TS
authors.lastname: Benaderet
authors.forename: Christina M
authors.initials: CM
authors.lastname: Dersch
authors.forename: Denise S
authors.initials: DS
authors.lastname: Simpson
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Prisinzano
authors.forename: Richard B
authors.initials: RB
authors.lastname: Rothman
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D015153:Blotting, Western; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D045785:Diterpenes, Clerodane / Q000494:pharmacology; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D020881:Enkephalin, D-Penicillamine (2,5)- / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine / Q000494:pharmacology; D016314:Ethylketocyclazocine / Q000494:pharmacology; D005048:Etorphine / Q000494:pharmacology; D005260:Female; D005663:Furans / Q000494:pharmacology; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D009020:Morphine / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011753:Pyrones / Q000494:pharmacology; D011957:Receptors, Opioid / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D017465:Receptors, Opioid, delta / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000235:genetics / Q000378:metabolism
chemical_list: C502982:9-(benzoyloxy)-2-(3-furanyl)dodecahydro-6a,10b-dimethyl-4,10-dioxo-2H-naphtho(2,1-c)pyran-7-carboxylic acid methyl ester; D000701:Analgesics, Opioid; D001549:Benzamides; D045785:Diterpenes, Clerodane; D005663:Furans; D009842:Oligopeptides; D010879:Piperazines; D011753:Pyrones; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C060208:deltorphin I, Ala(2)-; C088464:4-(alpha-(4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl)-N,N-diethylbenzamide; D005048:Etorphine; D016314:Ethylketocyclazocine; D016308:Enkephalin, Leucine-2-Alanine; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D009020:Morphine; D020881:Enkephalin, D-Penicillamine (2,5)-; C498819:GNAI3 protein, human; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; C090499:salvinorin A