title: Regulation of adenylyl cyclase, ERK1/2, and CREB by Gz following acute and chronic activation of the delta-opioid receptor.
abstract: Opioid tolerance and physical dependence in mammals can be rapidly induced by chronic exposure to opioid agonists. Recently, opioid receptors have been shown to interact with the pertussis toxin (PTX)-insensitive Gz (a member of the Gi subfamily), which inhibits adenylyl cyclase and stimulates mitogen-activated protein kinases (MAPKs). Here, we established stable human embryonic kidney 293 cell lines expressing delta-opioid receptors with or without Gz to examine the role of Gz in opioid receptor-regulated signaling systems. Each cell line was acutely or chronically treated with [D-Pen2,D-Pen5]enkephalin (DPDPE), a delta-selective agonist, in the absence or presence of PTX. Subsequently, the activities of adenylyl cyclase, cyclic AMP (cAMP)-dependent response element-binding proteins (CREBs), and MAPKs were measured by determining cAMP accumulation and phosphorylation of CREBs and the extracellular signal-regulated protein kinases (ERKs) 1 and 2. In cells coexpressing Gz, DPDPE inhibited forskolin-stimulated cAMP accumulation in a PTX-insensitive manner, but Gz could not replace Gi to mediate adenylyl cyclase supersensitization upon chronic opioid treatment. DPDPE-induced adenylyl cyclase supersensitization was not associated with an increase in the phosphorylation of CREBs. Both Gi and Gz mediated DPDPE-induced activation of ERK1/2, but these responses were abolished by chronic opioid treatment. Collectively, our results show that although Gz mediated opioid-induced inhibition of adenylyl cyclase and activation of ERK1/2, Gz alone was insufficient to mediate opioid-induced adenylyl cyclase supersensitization.
authors.affiliation: Department of Biology and Biotechnology Research Institute, Hong Kong University of Science and Technology, China.
authors.forename: P H
authors.initials: PH
authors.lastname: Tso
authors.forename: L Y
authors.initials: LY
authors.lastname: Yung
authors.forename: Y H
authors.initials: YH
authors.lastname: Wong
mesh_terms: D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000701:Analgesics, Opioid / Q000494:pharmacology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D020881:Enkephalin, D-Penicillamine (2,5)- / Q000494:pharmacology; D044385:GTP-Binding Protein alpha Subunits; D015870:Gene Expression / Q000502:physiology; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000166:cytology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D037342:Pertussis Toxin; D010766:Phosphorylation; D017465:Receptors, Opioid, delta / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D037361:Adenylate Cyclase Toxin; D000701:Analgesics, Opioid; D017362:Cyclic AMP Response Element-Binding Protein; C099387:GNAZ protein, human; D044385:GTP-Binding Protein alpha Subunits; D017465:Receptors, Opioid, delta; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D020881:Enkephalin, D-Penicillamine (2,5)-; D037342:Pertussis Toxin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020962:Heterotrimeric GTP-Binding Proteins; D000262:Adenylyl Cyclases