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.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Analysis of Variance
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Cell Membrane / metabolism
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Cyclic AMP / metabolism
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Cyclic AMP-Dependent Protein Kinases / biosynthesis*
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Cyclic AMP-Dependent Protein Kinases / physiology
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Dose-Response Relationship, Drug
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Drug Interactions
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Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / pharmacology
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Enzyme Inhibitors / pharmacology
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Flavonoids / pharmacology
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G-Protein-Coupled Receptor Kinase 3
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Humans
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Mitogen-Activated Protein Kinases / physiology
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Morphine / agonists
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Morphine / pharmacology
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Neuroblastoma
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Nociceptin
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Nociceptin Receptor
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Oligodeoxyribonucleotides, Antisense / pharmacology
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Opioid Peptides / pharmacology
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Protein Serine-Threonine Kinases / biosynthesis*
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Protein Serine-Threonine Kinases / physiology
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Receptor Cross-Talk / physiology*
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Receptors, Opioid / agonists
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Receptors, Opioid / physiology*
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Receptors, Opioid, mu / agonists
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Receptors, Opioid, mu / physiology*
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Transcription Factors / drug effects
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Transcription Factors / metabolism
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Tumor Cells, Cultured
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beta-Adrenergic Receptor Kinases
Substances
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Enzyme Inhibitors
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Flavonoids
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Oligodeoxyribonucleotides, Antisense
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Opioid Peptides
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Receptors, Opioid
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Receptors, Opioid, mu
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Transcription Factors
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Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
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Morphine
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Cyclic AMP
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Protein Serine-Threonine Kinases
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Cyclic AMP-Dependent Protein Kinases
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G-Protein-Coupled Receptor Kinase 3
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GRK3 protein, human
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beta-Adrenergic Receptor Kinases
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Mitogen-Activated Protein Kinases
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2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
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Nociceptin Receptor
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OPRL1 protein, human