title: Phosphatidylinositol-3 kinase is distinctively required for mu-, but not kappa-opioid receptor-induced activation of c-Jun N-terminal kinase.
abstract: Opioid receptors are the therapeutic targets of narcotic analgesics. All three types of opioid receptors (mu, delta and kappa) are prototypical G(i)-coupled receptors with common signaling characteristics in their regulation of intracellular events. Nevertheless, numerous signaling processes are differentially regulated by the three receptors. We have recently demonstrated that stimulation of delta-opioid receptor can up-regulate the activity of the c-Jun N-terminal kinase (JNK) in a pertussis toxin-sensitive manner (Kam et al. 2003; J. Neurochem. 84, 503-513). The present study revealed that the mu-opioid receptor could stimulate JNK in both SH-SY5Y cells and transfected COS-7 cells. The mechanism by which the mu-opioid receptor stimulated JNK was delineated with the use of specific inhibitors and dominant-negative mutants of signaling intermediates. Activation of JNK by the mu-opioid receptor was mediated through G beta gamma, Src kinase, son-of-sevenless (Sos), Rac and Cdc42. Interestingly, unlike the delta-opioid receptors, the mu-opioid receptor required phosphatidylinositol-3 kinase (PI3K) to activate JNK. The mu-opioid receptor-induced JNK activation was effectively inhibited by wortmannin or the coexpression of a dominant negative mutant of PI3K gamma. Like the delta-opioid receptor, activation of JNK by the kappa-opioid receptor occurred in a PI3K-independent manner. These studies revealed that the mu-opioid receptor utilize a distinct mechanism to regulate JNK.
authors.affiliation: Department of Biochemistry, the Molecular Neuroscience Center, and the Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Angel Y F
authors.initials: AY
authors.lastname: Kam
authors.forename: Anthony S L
authors.initials: AS
authors.lastname: Chan
authors.forename: Yung H
authors.initials: YH
authors.lastname: Wong
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D005799:Genes, Dominant; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017473:Receptors, Opioid, kappa / Q000235:genetics / Q000378:metabolism*; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism*; D020664:Son of Sevenless Proteins / Q000378:metabolism; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D019204:GTP-Binding Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D020664:Son of Sevenless Proteins; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D019061:src-Family Kinases