title: N-Methyl-D-aspartate attenuates opioid receptor-mediated G protein activation and this process involves protein kinase C.
abstract: The effects of N-methyl-D-aspartate (NMDA) on opioid receptor-mediated G protein activation were explored in neuroblastoma X glioma hybrid (NG108-15) cells. Treatment of the cells with NMDA resulted in a remarkable attenuation of [35S]guanosine-5'-O-(3-thio)triphosphate binding stimulated by [D-Pen2,D-Pen5]-enkephalin (DPDPE), a delta-opioid receptor agonist. The effects of NMDA were dose and time dependent with an IC50 value of 5 nM and could be blocked by NMDA receptor antagonists. After NMDA treatment, the DPDPE dose-response curve shifted to the right (EC50 value increased approximately 7-fold, from 6 to 40 nM), and the maximal response induced by DPDPE was reduced by approximately 60%. The effects of NMDA were reversible, and the DPDPE response could recover within 60 min. The functional responses of delta-, mu-, and kappa-opioid receptors in primarily cultured neurons also were attenuated significantly by NMDA treatment. The inhibitory effects of NMDA on opioid receptor-mediated G protein activation could be blocked by coadministration of the protein kinase C (PKC) inhibitors or by elimination of the extracellular Ca2+. Correspondingly, NMDA treatment of NG108 cells significantly elevated cellular PKC activity and stimulated Gialpha2 phosphorylation. Transient transfection into NG108-15 cells of the wild-type Gialpha2 and a mutated Gialpha2 (Ser144Ala) resulted in a 2-fold increase in DPDPE-stimulated G protein activation. The DPDPE responses were greatly inhibited by NMDA treatment in the wild-type Gialpha2-transfected cells but much less affected in the mutant Gialpha2-transfected cells. In summary, NMDA attenuates opioid receptor/G protein coupling, and this process requires activation of PKC.
authors.affiliation: Shanghai Institute of Cell Biology, Chinese Academy of Sciences, People's Republic of China.
authors.forename: G H
authors.initials: GH
authors.lastname: Fan
authors.forename: J
authors.initials: J
authors.lastname: Zhao
authors.forename: Y L
authors.initials: YL
authors.lastname: Wu
authors.forename: L G
authors.initials: LG
authors.lastname: Lou
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.forename: Q
authors.initials: Q
authors.lastname: Jing
authors.forename: L
authors.initials: L
authors.lastname: Ma
authors.forename: G
authors.initials: G
authors.lastname: Pei
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D016297:Mutagenesis, Site-Directed; D016202:N-Methylaspartate / Q000494:pharmacology*; D009447:Neuroblastoma / Q000201:enzymology / Q000378:metabolism; D009474:Neurons / Q000378:metabolism / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000502:physiology*; D011957:Receptors, Opioid / Q000819:agonists / Q000187:drug effects / Q000502:physiology*; D017465:Receptors, Opioid, delta / Q000187:drug effects / Q000502:physiology; D017473:Receptors, Opioid, kappa / Q000187:drug effects / Q000502:physiology; D017450:Receptors, Opioid, mu / Q000187:drug effects / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D004745:Enkephalins; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D016202:N-Methylaspartate; D020881:Enkephalin, D-Penicillamine (2,5)-; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate