title: Induction of G protein-coupled receptor kinases 2 and 3 contributes to the cross-talk between mu and ORL1 receptors following prolonged agonist exposure.
abstract: The molecular mechanism(s) underlying cross-tolerance between mu and opioid receptor-like 1 (ORL1) receptor agonists were investigated using two human neuroblastoma cell lines endogenously expressing these receptors and G protein-coupled receptor kinases (GRKs). Prolonged (24 h) activation of the mu receptor desensitized both mu and ORL1 receptor-mediated inhibition of forskolin-stimulated cAMP accumulation and upregulated GRK2 levels in SH-SY5Y and BE(2)-C cells. Prolonged ORL1 activation increased GRK2 levels and desensitized both receptors in SH-SY5Y cells. Upregulation of GRK2 correlated with increases in levels of transcription factors Sp1 or AP-2. PD98059, an upstream inhibitor of extracellular signal-regulated kinases 1 and 2 (ERK1/2), reversed all these events. Pretreatment with orphanin FQ/nociceptin (OFQ/N) also upregulated GRK3 levels in both cell lines, and desensitized both receptors in BE(2)-C cells. Protein kinase C (PKC), but not ERK1/2, inhibition blocked OFQ/N-mediated GRK3 induction and mu and ORL1 receptor desensitization in BE(2)-C cells. Antisense DNA treatment confirmed the involvement of GRK2/3 in mu and ORL1 desensitization. Here, we demonstrate for the first time a role for ERK1/2-mediated GRK2 induction in the development of tolerance to mu agonists, as well as cross-tolerance to OFQ/N. We also demonstrate that chronic OFQ/N-mediated desensitization of ORL1 and mu receptors occurs via cell-specific pathways, involving ERK1/2-dependent GRK2, or PKC-dependent and ERK1/2-independent GRK3 induction.
authors.affiliation: Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77204-5037, USA.
authors.forename: D R
authors.initials: DR
authors.lastname: Thakker
authors.forename: K M
authors.initials: KM
authors.lastname: Standifer
mesh_terms: D000704:Analysis of Variance; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000096:biosynthesis* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D054770:G-Protein-Coupled Receptor Kinase 3; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D009020:Morphine / Q000819:agonists / Q000494:pharmacology; D009447:Neuroblastoma; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D018847:Opioid Peptides / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis* / Q000502:physiology; D020239:Receptor Cross-Talk / Q000502:physiology*; D011957:Receptors, Opioid / Q000819:agonists / Q000502:physiology*; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000502:physiology*; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured; D051552:beta-Adrenergic Receptor Kinases; D000094942:Nociceptin Receptor; D000097629:Nociceptin
chemical_list: D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004791:Enzyme Inhibitors; D005419:Flavonoids; D054770:G-Protein-Coupled Receptor Kinase 3; D020928:Mitogen-Activated Protein Kinases; D009020:Morphine; D020319:Oligodeoxyribonucleotides, Antisense; D018847:Opioid Peptides; D017346:Protein Serine-Threonine Kinases; D011957:Receptors, Opioid; D017450:Receptors, Opioid, mu; D014157:Transcription Factors; D051552:beta-Adrenergic Receptor Kinases; D000094942:Nociceptin Receptor; D000097629:Nociceptin; C517848:GRK3 protein, human; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; C000722283:OPRL1 protein, human