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Anselmi L, Jaramillo I, Palacios M, Huynh J, Sternini C. Ligand-induced μ opioid receptor internalization in enteric neurons following chronic treatment with the opiate fentanyl. J Neurosci Res 2013; 91:854-60. [PMID: 23553842 DOI: 10.1002/jnr.23214] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 01/11/2013] [Accepted: 01/14/2013] [Indexed: 12/19/2022]
Abstract
Morphine differs from most opiates its poor ability to internalize μ opioid receptors (μORs). However, chronic treatment with morphine produces adaptational changes at the dynamin level, which enhance the efficiency of acute morphine stimulation to promote μOR internalization in enteric neurons. This study tested the effect of chronic treatment with fentanyl, a μOR-internalizing agonist, on ligand-induced endocytosis and the expression of the intracellular trafficking proteins, dynamin and β-arrestin, in enteric neurons using organotypic cultures of the guinea pig ileum. In enteric neurons from guinea pigs chronically treated with fentanyl, μOR immunoreactivity was predominantly at the cell surface after acute exposure to morphine with a low level of μOR translocation, slightly higher than in neurons from naïve animals. This internalization was not due to morphine's direct effect, because it was also observed in neurons exposed to medium alone. By contrast, D-Ala2-N-Me-Phe4-Gly-ol5-enkephalin (DAMGO), a potent μOR-internalizing agonist, induced pronounced and rapid μOR endocytosis in enteric neurons from animals chronically treated with fentanyl or from naïve animals. Chronic fentanyl treatment did not alter dynamin or β-arrestin expression. These findings indicate that prolonged activation of μORs with an internalizing agonist such as fentanyl does not enhance the ability of acute morphine to trigger μOR endocytosis or induce changes in intracellular trafficking proteins, as observed with prolonged activation of μORs with a poorly internalizing agonist such as morphine. Cellular adaptations induced by chronic opiate treatment might be ligand dependent and vary with the agonist efficiency to induce receptor internalization.
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Affiliation(s)
- Laura Anselmi
- CURE Digestive Diseases Research Center, Digestive Diseases Division, Los Angeles, CA 90073, USA
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2
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Patierno S, Anselmi L, Jaramillo I, Scott D, Garcia R, Sternini C. Morphine induces μ opioid receptor endocytosis in guinea pig enteric neurons following prolonged receptor activation. Gastroenterology 2011; 140:618-26. [PMID: 21070774 PMCID: PMC3033567 DOI: 10.1053/j.gastro.2010.11.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2010] [Revised: 10/18/2010] [Accepted: 11/02/2010] [Indexed: 12/11/2022]
Abstract
BACKGROUND & AIMS The μ opioid receptor (μOR) undergoes rapid endocytosis after acute stimulation with opioids and most opiates, but not with morphine. We investigated whether prolonged activation of μOR affects morphine's ability to induce receptor endocytosis in enteric neurons. METHODS We compared the effects of morphine, a poor μOR-internalizing opiate, and (D-Ala2,MePhe4,Gly-ol5) enkephalin (DAMGO), a potent μOR-internalizing agonist, on μOR trafficking in enteric neurons and on the expression of dynamin and β-arrestin immunoreactivity in the ileum of guinea pigs rendered tolerant by chronic administration of morphine. RESULTS Morphine (100 μmol/L) strongly induced endocytosis of μOR in tolerant but not naive neurons (55.7% ± 9.3% vs 24.2% ± 7.3%; P < .001) whereas DAMGO (10 μmol/L) strongly induced internalization of μOR in neurons from tolerant and naive animals (63.6% ± 8.4% and 66.5% ± 3.6%). Morphine- or DAMGO-induced μOR endocytosis resulted from direct interactions between the ligand and the μOR because endocytosis was not affected by tetrodotoxin, a blocker of endogenous neurotransmitter release. Ligand-induced μOR internalization was inhibited by pretreatment with the dynamin inhibitor, dynasore. Chronic morphine administration resulted in a significant increase and translocation of dynamin immunoreactivity from the intracellular pool to the plasma membrane, but did not affect β-arrestin immunoreactivity. CONCLUSIONS Chronic activation of μORs increases the ability of morphine to induce μOR endocytosis in enteric neurons, which depends on the level and cellular localization of dynamin, a regulatory protein that has an important role in receptor-mediated signal transduction in cells.
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Affiliation(s)
- Simona Patierno
- CURE Digestive Diseases Research Center, Veterans Administration Greater Los Angeles Healthcare System, University of California Los Angeles, Los Angeles, California 90095, USA,Department of Medicine, Digestive Diseases Division, University of California Los Angeles, Los Angeles, California 90095, USA
| | - Laura Anselmi
- CURE Digestive Diseases Research Center, Veterans Administration Greater Los Angeles Healthcare System, University of California Los Angeles, Los Angeles, California 90095, USA,Department of Medicine, Digestive Diseases Division, University of California Los Angeles, Los Angeles, California 90095, USA
| | - Ingrid Jaramillo
- Department of Medicine, Digestive Diseases Division, University of California Los Angeles, Los Angeles, California 90095, USA
| | - David Scott
- CURE Digestive Diseases Research Center, Veterans Administration Greater Los Angeles Healthcare System, University of California Los Angeles, Los Angeles, California 90095, USA,Department of Medicine, Digestive Diseases Division, University of California Los Angeles, Los Angeles, California 90095, USA,Department of Physiology, University of California Los Angeles, Los Angeles, California 90095, USA
| | - Rachel Garcia
- CURE Digestive Diseases Research Center, Veterans Administration Greater Los Angeles Healthcare System, University of California Los Angeles, Los Angeles, California 90095, USA
| | - Catia Sternini
- CURE Digestive Diseases Research Center, Veterans Administration Greater Los Angeles Healthcare System, University of California Los Angeles, Los Angeles, California 90095, USA,Department of Medicine, Digestive Diseases Division, University of California Los Angeles, Los Angeles, California 90095, USA,Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California 90095, USA
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3
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Neurokinin 1 receptors regulate morphine-induced endocytosis and desensitization of mu-opioid receptors in CNS neurons. J Neurosci 2009; 29:222-33. [PMID: 19129399 DOI: 10.1523/jneurosci.4315-08.2009] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
mu-Opioid receptors (MORs) are G-protein-coupled receptors (GPCRs) that mediate the physiological effects of endogenous opioid neuropeptides and opiate drugs such as morphine. MORs are coexpressed with neurokinin 1 receptors (NK1Rs) in several regions of the CNS that control opioid dependence and reward. NK1R activation affects opioid reward specifically, however, and the cellular basis for this specificity is unknown. We found that ligand-induced activation of NK1Rs produces a cell-autonomous and nonreciprocal inhibition of MOR endocytosis induced by diverse opioids. Studies using epitope-tagged receptors expressed in cultured striatal neurons and a neuroblastoma cell model indicated that this heterologous regulation is mediated by NK1R-dependent sequestration of arrestins on endosome membranes. First, endocytic inhibition mediated by wild-type NK1Rs was overcome in cells overexpressing beta-arrestin2, a major arrestin isoform expressed in striatum. Second, NK1R activation promoted sequestration of beta-arrestin2 on endosomes, whereas MOR activation did not. Third, heterologous inhibition of MOR endocytosis was prevented by mutational disruption of beta-arrestin2 sequestration by NK1Rs. NK1R-mediated regulation of MOR trafficking was associated with reduced opioid-induced desensitization of adenylyl cyclase signaling in striatal neurons. Furthermore, heterologous regulation of MOR trafficking was observed in both amygdala and locus ceruleus neurons that naturally coexpress these receptors. These results identify a cell-autonomous mechanism that may underlie the highly specific effects of NK1R on opioid signaling and suggest, more generally, that receptor-specific trafficking of arrestins may represent a fundamental mechanism for coordinating distinct GPCR-mediated signals at the level of individual CNS neurons.
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Walwyn W, Evans CJ, Hales TG. Beta-arrestin2 and c-Src regulate the constitutive activity and recycling of mu opioid receptors in dorsal root ganglion neurons. J Neurosci 2007; 27:5092-104. [PMID: 17494695 PMCID: PMC6672367 DOI: 10.1523/jneurosci.1157-07.2007] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Revised: 03/30/2007] [Accepted: 04/01/2007] [Indexed: 11/21/2022] Open
Abstract
Beta-arrestins bind to agonist-activated G-protein-coupled receptors regulating signaling events and initiating endocytosis. In beta-arrestin2-/- (beta arr2-/-) mice, a complex phenotype is observed that includes altered sensitivity to morphine. However, little is known of how beta-arrestin2 affects mu receptor signaling. We investigated the coupling of mu receptors to voltage-gated Ca2+ channels (VGCCs) in beta arr2+/+ and beta arr2-/- dorsal root ganglion neurons. A lack of beta-arrestin2 reduced the maximum inhibition of VGCCs by morphine and DAMGO (D-Ala2-N-Me-Phe4-glycol5-enkephalin) without affecting agonist potency, the onset of receptor desensitization, or the functional contribution of N-type VGCCs. The reduction in inhibition was accompanied by increased naltrexone-sensitive constitutive inhibitory coupling of mu receptors to VGCCs. Agonist-independent mu receptor inhibitory coupling was insensitive to CTAP (Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2), a neutral antagonist that inhibited the inverse agonist action of naltrexone. These functional changes were accompanied by diminished constitutive recycling and increased cell-surface mu receptor expression in beta arr2-/- compared with beta arr2+/+ neurons. Such changes could not be explained by the classical role of beta-arrestins in agonist-induced endocytosis. The localization of the nonreceptor tyrosine kinase c-Src appeared disrupted in beta arr2-/- neurons, and there was reduced activation of c-Src by DAMGO. Using the Src inhibitor PP2 [4-amino-5-(4-chlorophenyl)-(t-butyl)pyrazolo[3,4-d]pyrimidine], we demonstrated that defective Src signaling mimics the beta arr2-/- cellular phenotype of reduced mu agonist efficacy, increased constitutive mu receptor activity, and reduced constitutive recycling. We propose that beta-arrestin2 is required to target c-Src to constitutively active mu receptors, resulting in their internalization, providing another dimension to the complex role of beta-arrestin2 and c-Src in G-protein-coupled receptor function.
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MESH Headings
- Analgesics, Opioid/pharmacology
- Animals
- Arrestins/genetics
- Arrestins/metabolism
- CSK Tyrosine-Protein Kinase
- Calcium Channels/drug effects
- Calcium Channels/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Cells, Cultured
- Endocytosis/drug effects
- Endocytosis/physiology
- Female
- Ganglia, Spinal/metabolism
- Male
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Neurons, Afferent/drug effects
- Neurons, Afferent/metabolism
- Nociceptors/drug effects
- Nociceptors/metabolism
- Pain/metabolism
- Pain/physiopathology
- Patch-Clamp Techniques
- Protein Transport/drug effects
- Protein Transport/physiology
- Protein-Tyrosine Kinases/metabolism
- Receptors, G-Protein-Coupled/drug effects
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- Signal Transduction/drug effects
- Signal Transduction/physiology
- beta-Arrestin 2
- beta-Arrestins
- src-Family Kinases
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Affiliation(s)
- Wendy Walwyn
- Department of Psychiatry and Biobehavioral Sciences, Hatos Center, University of California, Los Angeles, Los Angeles, California 90095, and
| | - Christopher J. Evans
- Department of Psychiatry and Biobehavioral Sciences, Hatos Center, University of California, Los Angeles, Los Angeles, California 90095, and
| | - Tim G. Hales
- Departments of Pharmacology and Physiology, and Anesthesiology and Critical Care Medicine, The George Washington University, Washington, DC 20037
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Doyle GA, Sheng XR, Lin SSJ, Press DM, Grice DE, Buono RJ, Ferraro TN, Berrettini WH. Identification of five mouse mu-opioid receptor (MOR) gene (Oprm1) splice variants containing a newly identified alternatively spliced exon. Gene 2007; 395:98-107. [PMID: 17398041 PMCID: PMC2573390 DOI: 10.1016/j.gene.2007.02.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Revised: 02/02/2007] [Accepted: 02/03/2007] [Indexed: 10/23/2022]
Abstract
The mouse mu-opioid receptor gene, Oprm1, currently contains 18 recognized alternatively spliced exons [Doyle, G.A., Sheng, X.R., Lin, S.S.J., Press, D.M., Grice, D.E., Buono, R.J., Ferraro, T.N., Berrettini, W.H., 2007. Identification of three mouse mu-opioid receptor (MOR) gene (Oprm1) splice variants containing a newly identified alternatively spliced exon. Gene 388 (1-2) 135-147, in press (doi:10.1016/j.gene.2006.10.017). Electronic publication 2006 November 1] that generate 27 splice variants encoding at least 11 morphine-binding isoforms of the receptor. Here, we identify five MOR variants that contain an as yet undescribed exon (exon 19) of the gene, and we provide evidence that these MOR splice variants are expressed in the C57BL/6 and DBA/2 mouse strains. Three splice variants, MOR-1Eii, MOR-1Eiii and MOR-1Eiv, encode the MOR-1E isoform and contain the newly identified exon 19 in their 3' untranslated regions. The fourth splice variant encodes a novel mu-opioid receptor isoform, MOR-1U, and contains exon 19 in its coding region. The cytoplasmic tail of the putative MOR-1U isoform contains a putative nuclear localization signal encoded by the sequence of exon 19. Exon 19 appears to be conserved in the rat, but not in humans. In mouse and rat Oprm1, exon 19 is located between described exons 7 and 8. We also report the cloning of the "full-length" MOR-1T splice variant [Kvam, T.-M., Baar, C., Rakvag, T.T., Kaasa, S., Krokan, H.E., Skorpen, F., 2004. Genetic analysis of the murine mu-opioid receptor: increased complexity of Oprm1 gene splicing, J. Mol. Med. 82 (4) 250-255] that encodes MOR-1 and contains the newly identified exon in its 3' UTR. RT-PCR analysis suggests that splice variants MOR-1Eii, MOR-1Eiii, MOR-1Eiv, MOR-1T and MOR-1U are expressed in all brain regions analyzed (cortex, cerebellum, hypothalamus, thalamus and striatum). These exon 19-containing splice variants add to the growing complexity of the mouse Oprm1 gene.
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MESH Headings
- 3' Untranslated Regions
- Alternative Splicing
- Amino Acid Sequence
- Animals
- Base Sequence
- Brain/metabolism
- Cloning, Molecular
- DNA Primers/genetics
- DNA, Complementary/genetics
- Exons
- Genetic Variation
- Introns
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Molecular Sequence Data
- Protein Biosynthesis
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Opioid, mu/genetics
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
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Affiliation(s)
- Glenn A Doyle
- The Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
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Doyle GA, Rebecca Sheng X, Lin SSJ, Press DM, Grice DE, Buono RJ, Ferraro TN, Berrettini WH. Identification of three mouse mu-opioid receptor (MOR) gene (Oprm1) splice variants containing a newly identified alternatively spliced exon. Gene 2006; 388:135-47. [PMID: 17156941 DOI: 10.1016/j.gene.2006.10.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 10/24/2006] [Accepted: 10/28/2006] [Indexed: 12/01/2022]
Abstract
The mouse mu-opioid receptor gene, Oprm1, is recognized currently to contain 17 alternatively spliced exons that generate 24 splice variants encoding at least 11 morphine-binding isoforms of the receptor. Here, we identify three new MOR splice variants that contain a previously undescribed exon, exon 18, and provide evidence that they are expressed in two mouse strains. The transcripts containing the newly identified exon 18 encode two new putative mu-opioid receptor isoforms, MOR-1V and MOR-1W. In mouse Oprm1, exon 18 is located between the described exons 10 and 6. Exon 18 appears to be conserved in the rat genome between exons 4 and 7. A BLAST search of the non-redundant GenBank database suggests that human OPRM1 may also contain exon 18. Analysis of mouse brain mRNA by RT-PCR suggests that MOR-1Vii transcripts are expressed in all areas of the brain analyzed, whereas expression of MOR-1Vi transcripts was restricted to thalamus and striatum. MOR-1W transcripts are expressed most highly in the hypothalamus, thalamus and striatum. In summary, we have identified three brain expressed, alternatively spliced mouse MOR splice variants containing a novel exon and encoding new putative MOR isoforms, MOR-1V and MOR-1W.
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MESH Headings
- Alternative Splicing
- Amino Acid Sequence
- Animals
- Base Sequence
- Brain/metabolism
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA, Complementary/isolation & purification
- Exons/genetics
- Gene Expression
- Male
- Mice/genetics
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Models, Genetic
- Molecular Sequence Data
- Phosphorylation
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Opioid, mu/genetics
- Receptors, Opioid, mu/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Analysis, DNA
- Sequence Homology, Nucleic Acid
- Species Specificity
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Affiliation(s)
- Glenn A Doyle
- The Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
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7
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Doyle GA, Sheng XR, Schwebel CL, Ferraro TN, Berrettini WH, Buono RJ. Identification and functional significance of polymorphisms in the μ-opioid receptor gene (Oprm) promoter of C57BL/6 and DBA/2 mice. Neurosci Res 2006; 55:244-54. [PMID: 16644048 DOI: 10.1016/j.neures.2006.03.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2005] [Revised: 03/03/2006] [Accepted: 03/13/2006] [Indexed: 11/30/2022]
Abstract
C57BL/6J and DBA/2J mice demonstrate differences in morphine preference when tested in a two-bottle choice paradigm. Quantitative trait loci (QTL) mapping suggested the proximal region of chromosome 10 was responsible for 41% of the observed genetic variance. The mu-opioid receptor (MOR) gene (Oprm) maps to this region and is a prime candidate for explaining the QTL. We hypothesized that variations in Oprm between these strains are responsible for differences in morphine preference. We identify five single nucleotide polymorphisms (SNPs) in the Oprm promoter; three within or near putative transcription factor binding sites. Promoter fragments were amplified from genomic DNA by polymerase chain reaction (PCR) and subcloned into luciferase reporter vectors. A significant difference in basal Oprm promoter activity was seen with C57BL/6 and DBA/2 approximately 1675 constructs in MOR-positive BE(2)-C cells, but not in MOR-negative Neuro-2a cells. In BE(2)-C cells, average DBA/2 approximately 1675 construct activity was 1.3-2.0x greater than average C57BL/6 activity suggesting that the SNPs might alter MOR expression in these two mouse strains. Significant differences in promoter activities between the two cell lines suggest that cell-type-specific transcription factors are involved. No significant differences in construct activity were found between untreated and morphine-treated BE(2)-C or Neuro-2a cells, suggesting that morphine does not regulate transcription of Oprm.
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Affiliation(s)
- Glenn A Doyle
- The Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104, United States.
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Haberstock-Debic H, Kim KA, Yu YJ, von Zastrow M. Morphine promotes rapid, arrestin-dependent endocytosis of mu-opioid receptors in striatal neurons. J Neurosci 2006; 25:7847-57. [PMID: 16120787 PMCID: PMC6725258 DOI: 10.1523/jneurosci.5045-04.2005] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Morphine activates mu-opioid receptors (MORs) without promoting their rapid endocytosis in a number of cell types. A previous study suggested that morphine can drive rapid redistribution of MORs in the nucleus accumbens, but it was not possible in this in vivo study to identify a specific membrane trafficking pathway affected by morphine, to exclude possible indirect actions of morphine via opiate-regulated neural circuitry, or to define the mechanism of this morphine-dependent regulation. In the present study, we addressed these questions using dissociated primary cultures of rat striatal neurons as a model system. Morphine promoted a rapid redistribution of both endogenous and recombinant MORs within 30 min after drug addition to the culture medium. This effect was mediated by rapid endocytosis and occurred in a cell-autonomous manner, as indicated by its detection in cells plated at low density and in cultures in which depolarization was blocked by tetrodotoxin. Morphine-induced endocytosis of MORs was quantitatively similar to that induced by the enkephalin analog D-Ala2-N-Me-Phe4-Glycol5-enkephalin, and endocytosis induced by both ligands was inhibited by a dominant-negative mutant version of arrestin-3 (beta-arrestin-2). These results extend previous in vivo results and indicate that morphine is indeed capable of driving rapid endocytosis of mu-opioid receptors in an important subset of opiate-responsive CNS neurons. They also suggest a cellular mechanism by which beta-arrestins may modulate the physiological effects of morphine in vivo.
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10
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Abstract
The risk of initiating and maintaining the use of opiates up to the point of abuse and dependence is to a large degree genetically transmitted and is separate from genetic risk factors for addiction to other drugs of abuse. Pharmacogenetic studies have so far focused on obvious candidate genes that are expected to be involved either in the pharmacokinetics or in the pharmacodynamics of opioids in the mesolimbic reward system of the brain. The few findings of a positive allelic association rarely withstand replication in independent case-control or less stratification-prone family-based association samples. A pharmacogenomic approach in the best sense of the word, however, involves an unbiased, genome-wide, parallel search for risk genes and gene expression patterns. So far, only quantitative trait loci mapping studies of inbred rodent strains and differential expression studies using high-density DNA microarrays fulfill these requirements. The present state of pharmacogenomic and pharmacogenetic studies in animals and humans with respect to opiate addiction is reviewed in this paper.
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Affiliation(s)
- D Lichtermann
- Department of Psychiatry, University of Bonn, Sigmund-Freud-Str. 25, D-53105, Bonn, Germany.
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