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Underwood O, Fritzwanker S, Glenn J, Blum NK, Batista-Gondin A, Drube J, Hoffmann C, Briddon SJ, Schulz S, Canals M. Key phosphorylation sites for robust β-arrestin2 binding at the MOR revisited. Commun Biol 2024; 7:933. [PMID: 39095612 PMCID: PMC11297201 DOI: 10.1038/s42003-024-06571-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 07/09/2024] [Indexed: 08/04/2024] Open
Abstract
Desensitisation of the mu-opioid receptor (MOR) is proposed to underlie the initiation of opioid analgesic tolerance and previous work has shown that agonist-induced phosphorylation of the MOR C-tail contributes to this desensitisation. Moreover, phosphorylation is important for β-arrestin recruitment to the receptor, and ligands of different efficacies induce distinct phosphorylation barcodes. The C-tail 370TREHPSTANT379 motif harbours Ser/Thr residues important for these regulatory functions. 375Ser is the primary phosphorylation site of a ligand-dependent, hierarchical, and sequential process, whereby flanking 370Thr, 376Thr and 379Thr get subsequently and rapidly phosphorylated. Here we used GRK KO cells, phosphosite specific antibodies and site-directed mutagenesis to evaluate the contribution of the different GRK subfamilies to ligand-induced phosphorylation barcodes and β-arrestin2 recruitment. We show that both GRK2/3 and GRK5/6 subfamilies promote phosphorylation of 370Thr and 375Ser. Importantly, only GRK2/3 induce phosphorylation of 376Thr and 379Thr, and we identify these residues as key sites to promote robust β-arrestin recruitment to the MOR. These data provide insight into the mechanisms of MOR regulation and suggest that the cellular complement of GRK subfamilies plays an important role in determining the tissue responses of opioid agonists.
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Affiliation(s)
- Owen Underwood
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, Midlands, UK
| | - Sebastian Fritzwanker
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Jaqueline Glenn
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, Midlands, UK
| | - Nina Kathleen Blum
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Arisbel Batista-Gondin
- Drug Discovery Biology Theme, Monash Institute of Pharmaceutical Sciences, Monash University, Victoria, Australia
| | - Julia Drube
- Institut fur Molekulare Zellbiologie, CMB - Center for Molecular Biomedicine, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Carsten Hoffmann
- Institut fur Molekulare Zellbiologie, CMB - Center for Molecular Biomedicine, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Stephen J Briddon
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, Midlands, UK
| | - Stefan Schulz
- Institut für Pharmakologie und Toxikologie, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
- 7TM Antibodies GmbH, Hans-Knöll-Straße 6, D-07745, Jena, Germany
| | - Meritxell Canals
- Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK.
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, Midlands, UK.
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2
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Patocka J, Wu W, Oleksak P, Jelinkova R, Nepovimova E, Spicanova L, Springerova P, Alomar S, Long M, Kuca K. Fentanyl and its derivatives: Pain-killers or man-killers? Heliyon 2024; 10:e28795. [PMID: 38644874 PMCID: PMC11031787 DOI: 10.1016/j.heliyon.2024.e28795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 03/24/2024] [Accepted: 03/25/2024] [Indexed: 04/23/2024] Open
Abstract
Fentanyl is a synthetic μ-opioid receptor agonist approved to treat severe to moderate pain with faster onset of action and about 100 times more potent than morphine. Over last two decades, abuse of fentanyl and its derivatives has an increased trend, globally. Currently, the United States (US) faces the most serious situation related to fentanyl overdose, commonly referred to as the opioid epidemic. Nowadays, fentanyl is considered as the number one cause of death for adults aged 18-45 in the US. Synthesis and derivatization of fentanyl is inexpensive to manufacture and easily achievable. Indeed, more than 1400 fentanyl derivatives have been described in the scientific literature and patents. In addition, accessibility and efficacy of fentanyl and its derivatives can play a potential role in misuse of these compounds as a chemical weapon. In this review, the properties, general pharmacology, and overdose death cases associated with fentanyl and selected derivatives are presented. Moreover, current opioid epidemic in the US, Moscow theatre hostage crisis, and potential misuse of fentanyl and its derivatives as a chemical weapon are disclosed.
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Affiliation(s)
- Jiri Patocka
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, 50003 Hradec Kralove, Czech Republic
| | - Wenda Wu
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, 50003 Hradec Kralove, Czech Republic
- School of Food and Biological Engineering, Hefei University of Technology, Hefei 230009, China
| | - Patrik Oleksak
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, 50003 Hradec Kralove, Czech Republic
| | - Romana Jelinkova
- NBC Defence Institute, University of Defence, 68201 Vyskov, Czech Republic
| | - Eugenie Nepovimova
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, 50003 Hradec Kralove, Czech Republic
| | - Lenka Spicanova
- Philosophical Faculty, University of Hradec Kralove, 50003 Hradec Kralove, Czech Republic
| | - Pavlina Springerova
- Philosophical Faculty, University of Hradec Kralove, 50003 Hradec Kralove, Czech Republic
| | - Suliman Alomar
- Doping Research Chair, Zoology Department, College of Science, King Saud University, Riyadh-11451, Kingdom of Saudi Arabia
| | - Miao Long
- Key Laboratory of Zoonosis of Liaoning Province, College of Animal Science & Veterinary Medicine, Shenyang Agricultural University, Shenyang 110866, China
| | - Kamil Kuca
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, 50003 Hradec Kralove, Czech Republic
- Biomedical Research Centre, University Hospital in Hradec Kralove, Sokolska 581, 50005 Hradec Kralove, Czech Republic
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3
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Coutens B, Ingram SL. Key differences in regulation of opioid receptors localized to presynaptic terminals compared to somas: Relevance for novel therapeutics. Neuropharmacology 2023; 226:109408. [PMID: 36584882 PMCID: PMC9898207 DOI: 10.1016/j.neuropharm.2022.109408] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 12/05/2022] [Accepted: 12/27/2022] [Indexed: 12/29/2022]
Abstract
Opioid receptors are G protein-coupled receptors (GPCRs) that regulate activity within peripheral, subcortical and cortical circuits involved in pain, reward, and aversion processing. Opioid receptors are expressed in both presynaptic terminals where they inhibit neurotransmitter release and postsynaptic locations where they act to hyperpolarize neurons and reduce activity. Agonist activation of postsynaptic receptors at the plasma membrane signal via ion channels or cytoplasmic second messengers. Agonist binding initiates regulatory processes that include phosphorylation by G protein receptor kinases (GRKs) and recruitment of beta-arrestins that desensitize and internalize the receptors. Opioid receptors also couple to effectors from endosomes activating intracellular enzymes and kinases. In contrast to postsynaptic opioid receptors, receptors localized to presynaptic terminals are resistant to desensitization such that there is no loss of signaling in the continuous presence of opioids over the same time scale. Thus, the balance of opioid signaling in circuits expressing pre- and postsynaptic opioid receptors is shifted toward inhibition of presynaptic neurotransmitter release during continuous opioid exposure. The functional implication of this shift is not often acknowledged in behavioral studies. This review covers what is currently understood about regulation of opioid/nociceptin receptors, with an emphasis on opioid receptor signaling in pain and reward circuits. Importantly, the review covers regulation of presynaptic receptors and the critical gaps in understanding this area, as well as the opportunities to further understand opioid signaling in brain circuits. This article is part of the Special Issue on "Opioid-induced changes in addiction and pain circuits".
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Affiliation(s)
- Basile Coutens
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA
| | - Susan L Ingram
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA.
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4
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Gledhill LJ, Babey AM. Synthesis of the Mechanisms of Opioid Tolerance: Do We Still Say NO? Cell Mol Neurobiol 2021; 41:927-948. [PMID: 33704603 DOI: 10.1007/s10571-021-01065-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 02/12/2021] [Indexed: 10/21/2022]
Abstract
The use of morphine as a first-line agent for moderate-to-severe pain is limited by the development of analgesic tolerance. Initially opioid receptor desensitization in response to repeated stimulation, thought to underpin the establishment of tolerance, was linked to a compensatory increase in adenylate cyclase responsiveness. The subsequent demonstration of cross-talk between N-methyl-D-aspartate (NMDA) glutamate receptors and opioid receptors led to the recognition of a role for nitric oxide (NO), wherein blockade of NO synthesis could prevent tolerance developing. Investigations of the link between NO levels and opioid receptor desensitization implicated a number of events including kinase recruitment and peroxynitrite-mediated protein regulation. Recent experimental advances and the identification of new cellular constituents have expanded the potential signaling candidates to include unexpected, intermediary compounds not previously linked to this process such as zinc, histidine triad nucleotide-binding protein 1 (HINT1), micro-ribonucleic acid (mi-RNA) and regulator of G protein signaling Z (RGSZ). A further complication is a lack of consistency in the protocols used to create tolerance, with some using acute methods measured in minutes to hours and others using days. There is also an emphasis on the cellular changes that are extant only after tolerance has been established. Although a review of the literature demonstrates a lack of spatio-temporal detail, there still appears to be a pivotal role for nitric oxide, as well as both intracellular and intercellular cross-talk. The use of more consistent approaches to verify these underlying mechanism(s) could provide an avenue for targeted drug development to rescue opioid efficacy.
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Affiliation(s)
- Laura J Gledhill
- CURA Pharmacy, St. John of God Hospital, Bendigo, VIC, 3550, Australia
| | - Anna-Marie Babey
- Faculty of Medicine and Health, University of New England, Armidale, NSW, 2351, Australia.
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Abreu N, Levitz J. Optogenetic Techniques for Manipulating and Sensing G Protein-Coupled Receptor Signaling. Methods Mol Biol 2021; 2173:21-51. [PMID: 32651908 DOI: 10.1007/978-1-0716-0755-8_2] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
G protein-coupled receptors (GPCRs) form the largest class of membrane receptors in the mammalian genome with nearly 800 human genes encoding for unique subtypes. Accordingly, GPCR signaling is implicated in nearly all physiological processes. However, GPCRs have been difficult to study due in part to the complexity of their function which can lead to a plethora of converging or diverging downstream effects over different time and length scales. Classic techniques such as pharmacological control, genetic knockout and biochemical assays often lack the precision required to probe the functions of specific GPCR subtypes. Here we describe the rapidly growing set of optogenetic tools, ranging from methods for optical control of the receptor itself to optical sensing and manipulation of downstream effectors. These tools permit the quantitative measurements of GPCRs and their downstream signaling with high specificity and spatiotemporal precision.
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Affiliation(s)
- Nohely Abreu
- Biochemistry, Cell and Molecular Biology Graduate Program, Weill Cornell Medicine, New York, NY, USA
| | - Joshua Levitz
- Biochemistry, Cell and Molecular Biology Graduate Program, Weill Cornell Medicine, New York, NY, USA.
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA.
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6
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Lemos Duarte M, Trimbake NA, Gupta A, Tumanut C, Fan X, Woods C, Ram A, Gomes I, Bobeck EN, Schechtman D, Devi LA. High-throughput screening and validation of antibodies against synaptic proteins to explore opioid signaling dynamics. Commun Biol 2021; 4:238. [PMID: 33619305 PMCID: PMC7900253 DOI: 10.1038/s42003-021-01744-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Accepted: 11/13/2020] [Indexed: 12/12/2022] Open
Abstract
Antibodies represent powerful tools to examine signal transduction pathways. Here, we present a strategy integrating multiple state-of-the-art methods to produce, validate, and utilize antibodies. Focusing on understudied synaptic proteins, we generated 137 recombinant antibodies. We used yeast display antibody libraries from the B cells of immunized rabbits, followed by FACS sorting under stringent conditions to identify high affinity antibodies. The antibodies were validated by high-throughput functional screening, and genome editing. Next, we explored the temporal dynamics of signaling in single cells. A subset of antibodies targeting opioid receptors were used to examine the effect of treatment with opiates that have played central roles in the worsening of the 'opioid epidemic.' We show that morphine and fentanyl exhibit differential temporal dynamics of receptor phosphorylation. In summary, high-throughput approaches can lead to the identification of antibody-based tools required for an in-depth understanding of the temporal dynamics of opioid signaling.
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Affiliation(s)
- Mariana Lemos Duarte
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1603, New York City, NY, 10029, USA
| | - Nikita A Trimbake
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1603, New York City, NY, 10029, USA
- Regeneron Pharmaceutical, 777 Old Saw Mill River Rd, Tarrytown, NY, 10591, USA
| | - Achla Gupta
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1603, New York City, NY, 10029, USA
| | | | - Xiaomin Fan
- AvantGen Inc., 6162 Nancy Ridge Dr #150, San Diego, CA, 92121, USA
| | - Catherine Woods
- AvantGen Inc., 6162 Nancy Ridge Dr #150, San Diego, CA, 92121, USA
| | - Akila Ram
- Department of Biology, Utah State University, Logan, UT, 84322, USA
| | - Ivone Gomes
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1603, New York City, NY, 10029, USA
| | - Erin N Bobeck
- Department of Biology, Utah State University, Logan, UT, 84322, USA
| | - Deborah Schechtman
- Department of Biochemistry, University of São Paulo, 748 Av Prof Lineu Prestes, room 1208 Cidade Universitaria, São Paulo, SP, 05508000, Brazil
| | - Lakshmi A Devi
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1603, New York City, NY, 10029, USA.
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7
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Kim D, Castaño M, Lujan LK, Woo JA, Liggett SB. The short third intracellular loop and cytoplasmic tail of bitter taste receptors provide functionally relevant GRK phosphorylation sites in TAS2R14. J Biol Chem 2021; 296:100216. [PMID: 33465377 PMCID: PMC7949105 DOI: 10.1074/jbc.ra120.016056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 12/16/2020] [Accepted: 12/21/2020] [Indexed: 01/12/2023] Open
Abstract
For most G protein–coupled receptors, the third intracellular loop (IL3) and carboxy-terminal tail (CT) are sites for G protein–coupled receptor kinase (GRK)–mediated phosphorylation, leading to β-arrestin binding and agonist-specific desensitization. These regions of bitter taste receptors (TAS2Rs) are extremely short compared with the superfamily, and their function in desensitization is unknown. TAS2R14 expressed on human airway smooth muscle cells relax the cell, suggesting a novel target for bronchodilators. To assess IL3 and CT in agonist-promoted TAS2R14 desensitization (tachyphylaxis), we generated fusion proteins of both the WT sequence and Ala substituted for Ser/Thr in the IL3 and CT sequences. In vitro, activated GRK2 phosphorylated WT IL3 and WT CT proteins but not Ala-substituted forms. TAS2R14s with mutations in IL3 (IL-5A), CT (CT-5A), and in both regions (IL/CT-10A) were expressed in human embryonic kidney 293T cells. IL/CT-10A and CT-5A failed to undergo desensitization of the intracellular calcium response compared with WT, indicating that functional desensitization by GRK phosphorylation is at residues in the CT. Desensitization of TAS2R14 was blocked by GRK2 knockdown in human airway smooth muscle cells. Receptor:β-arrestin binding was absent in IL/CT-10A and CT-5A and reduced in IL-5A, indicating a role for IL3 phosphorylation in the β-arrestin interaction for this function. Agonist-promoted internalization of IL-5A and CT-5A receptors was impaired, and they failed to colocalize with early endosomes. Thus, agonist-promoted functional desensitization of TAS2R14 occurs by GRK phosphorylation of CT residues and β-arrestin binding. However, β-arrestin function in the internalization and trafficking of the receptor also requires GRK phosphorylation of IL3 residues.
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Affiliation(s)
- Donghwa Kim
- Department of Medicine, University of South Florida Morsani College of Medicine, Tampa, Florida, USA
| | - Maria Castaño
- Department of Medicine, University of South Florida Morsani College of Medicine, Tampa, Florida, USA
| | - Lauren K Lujan
- Department of Medicine, University of South Florida Morsani College of Medicine, Tampa, Florida, USA
| | - Jung A Woo
- Department of Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, Florida, USA
| | - Stephen B Liggett
- Departments of Medicine and Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, Florida, USA.
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Gurevich EV, Gurevich VV. GRKs as Modulators of Neurotransmitter Receptors. Cells 2020; 10:cells10010052. [PMID: 33396400 PMCID: PMC7823573 DOI: 10.3390/cells10010052] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 12/23/2020] [Accepted: 12/30/2020] [Indexed: 01/08/2023] Open
Abstract
Many receptors for neurotransmitters, such as dopamine, norepinephrine, acetylcholine, and neuropeptides, belong to the superfamily of G protein-coupled receptors (GPCRs). A general model posits that GPCRs undergo two-step homologous desensitization: the active receptor is phosphorylated by kinases of the G protein-coupled receptor kinase (GRK) family, whereupon arrestin proteins specifically bind active phosphorylated receptors, shutting down G protein-mediated signaling, facilitating receptor internalization, and initiating distinct signaling pathways via arrestin-based scaffolding. Here, we review the mechanisms of GRK-dependent regulation of neurotransmitter receptors, focusing on the diverse modes of GRK-mediated phosphorylation of receptor subtypes. The immediate signaling consequences of GRK-mediated receptor phosphorylation, such as arrestin recruitment, desensitization, and internalization/resensitization, are equally diverse, depending not only on the receptor subtype but also on phosphorylation by GRKs of select receptor residues. We discuss the signaling outcome as well as the biological and behavioral consequences of the GRK-dependent phosphorylation of neurotransmitter receptors where known.
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9
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GRKs as Key Modulators of Opioid Receptor Function. Cells 2020; 9:cells9112400. [PMID: 33147802 PMCID: PMC7692057 DOI: 10.3390/cells9112400] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 10/21/2020] [Accepted: 10/28/2020] [Indexed: 12/21/2022] Open
Abstract
Understanding the link between agonist-induced phosphorylation of the mu-opioid receptor (MOR) and the associated physiological effects is critical for the development of novel analgesic drugs and is particularly important for understanding the mechanisms responsible for opioid-induced tolerance and addiction. The family of G protein receptor kinases (GRKs) play a pivotal role in such processes, mediating phosphorylation of residues at the C-tail of opioid receptors. Numerous strategies, such as phosphosite specific antibodies and mass spectrometry have allowed the detection of phosphorylated residues and the use of mutant knock-in mice have shed light on the role of GRK regulation in opioid receptor physiology. Here we review our current understanding on the role of GRKs in the actions of opioid receptors, with a particular focus on the MOR, the target of most commonly used opioid analgesics such as morphine or fentanyl.
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10
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Lemos Duarte M, Devi LA. Post-translational Modifications of Opioid Receptors. Trends Neurosci 2020; 43:417-432. [PMID: 32459993 PMCID: PMC7323054 DOI: 10.1016/j.tins.2020.03.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 03/26/2020] [Accepted: 03/26/2020] [Indexed: 12/13/2022]
Abstract
Post-translational modifications (PTMs) are key events in signal transduction since they affect protein function by regulating their abundance and/or activity. PTMs involve the covalent attachment of functional groups to specific amino acids. Since they tend to be generally reversible, PTMs serve as regulators of signal transduction pathways. G-protein-coupled receptors (GPCRs) are major signaling proteins that undergo multiple types of PTMs. In this Review, we focus on the opioid receptors, members of GPCR family A, and highlight recent advances in the field that have underscored the importance of PTMs in the functional regulation of these receptors. Since opioid receptor activity plays a central role in the development of tolerance and addiction to morphine and other drugs of abuse, understanding the molecular mechanisms regulating receptor activity is of fundamental importance.
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Affiliation(s)
- Mariana Lemos Duarte
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Lakshmi A Devi
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
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11
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Leff ER, Arttamangkul S, Williams JT. Chronic Treatment with Morphine Disrupts Acute Kinase-Dependent Desensitization of GPCRs. Mol Pharmacol 2020; 98:497-507. [PMID: 32362586 DOI: 10.1124/mol.119.119362] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 04/24/2020] [Indexed: 11/22/2022] Open
Abstract
Based on studies using mutations of the µ-opioid receptor (MOR), phosphorylation of multiple sites on the C-terminus has been recognized as a critical step underlying acute desensitization and the development of cellular tolerance. The aim of this study is to explore which kinases mediate desensitization of MOR in brain slices from drug-naïve and morphine-treated animals. Whole-cell recordings from locus coeruleus neurons were made, and the agonist-induced increase in potassium conductance was measured. In slices from naïve animals, pharmacological inhibition of G-protein receptor kinase (GRK2/3) with compound 101 blocked acute desensitization. Following chronic treatment with morphine, compound 101 was less effective at blocking acute desensitization. Compound 101 blocked receptor internalization in tissue from both naïve and morphine-treated animals, suggesting that GRK2/3 remained active. Kinase inhibitors aimed at blocking protein kinase C and c-Jun N-terminal kinase had no effect on desensitization in tissue taken from naïve animals. However, in slices taken from morphine-treated animals, the combination of these blockers along with compound 101 was required to block acute desensitization. Acute desensitization of the potassium conductance induced by the somatostatin receptor was also blocked by compound 101 in slices from naïve but not morphine-treated animals. As was observed with MOR, it was necessary to use the combination of kinase inhibitors to block desensitization of the somatostatin receptor in slices from morphine-treated animals. The results show that chronic treatment with morphine results in a surprising and heterologous adaptation in kinase-dependent desensitization. SIGNIFICANCE STATEMENT: The results show that chronic treatment with morphine induced heterologous adaptations in kinase regulation of G protein coupled receptor (GPCR) desensitization. Although the canonical mechanism for acute desensitization through phosphorylation by G protein-coupled receptor kinase is supported in tissue taken from naïve animals, following chronic treatment with morphine, the acute kinase-dependent desensitization of GPCRs is disrupted such that additional kinases, including protein kinase C and c-Jun N-terminal kinase, contribute to desensitization.
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Affiliation(s)
- Emily R Leff
- Vollum Institute, Oregon Health and Science University, Portland, Oregon
| | | | - John T Williams
- Vollum Institute, Oregon Health and Science University, Portland, Oregon
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12
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Fernandez TJ, De Maria M, Lobingier BT. A cellular perspective of bias at G protein-coupled receptors. Protein Sci 2020; 29:1345-1354. [PMID: 32297394 DOI: 10.1002/pro.3872] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 04/10/2020] [Accepted: 04/10/2020] [Indexed: 12/17/2022]
Abstract
G protein-coupled receptors (GPCRs) modulate cell function over short- and long-term timescales. GPCR signaling depends on biochemical parameters that define the what, when, and where of receptor function: what proteins mediate and regulate receptor signaling, where within the cell these interactions occur, and how long these interactions persist. These parameters can vary significantly depending on the activating ligand. Collectivity, differential agonist activity at a GPCR is called bias or functional selectivity. Here we review agonist bias at GPCRs with a focus on ligands that show dramatically different cellular responses from their unbiased counterparts.
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Affiliation(s)
- Thomas J Fernandez
- Department of Chemical Physiology and Biochemistry, Oregon Health and Sciences University, Portland, Oregon, USA
| | - Monica De Maria
- Department of Chemical Physiology and Biochemistry, Oregon Health and Sciences University, Portland, Oregon, USA
| | - Braden T Lobingier
- Department of Chemical Physiology and Biochemistry, Oregon Health and Sciences University, Portland, Oregon, USA
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13
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Birdsong WT, Williams JT. Recent Progress in Opioid Research from an Electrophysiological Perspective. Mol Pharmacol 2020; 98:401-409. [PMID: 32198208 PMCID: PMC7562972 DOI: 10.1124/mol.119.119040] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Accepted: 03/12/2020] [Indexed: 02/06/2023] Open
Abstract
Electrophysiological approaches provide powerful tools to further our understanding of how different opioids affect signaling through opioid receptors; how opioid receptors modulate circuitry involved in processes such as pain, respiration, addiction, and feeding; and how receptor signaling and circuits are altered by physiologic challenges, such as injury, stress, and chronic opioid treatment. The use of genetic manipulations to alter or remove μ-opioid receptors (MORs) with anatomic and cell type specificity and the ability to activate or inhibit specific circuits through opto- or chemogenetic approaches are being used in combination with electrophysiological, pharmacological, and systems-level physiology experiments to expand our understanding of the beneficial and maladaptive roles of opioids and opioid receptor signaling. New approaches for studying endogenous opioid peptide signaling and release and the dynamics of these systems in response to chronic opioid use, pain, and stress will add another layer to our understanding of the intricacies of opioid modulation of brain circuits. This understanding may lead to new targets or approaches for drug development or treatment regimens that may affect both acute and long-term effects of manipulating the activity of circuits involved in opioid-mediated physiology and behaviors. This review will discuss recent advancements in our understanding of the role of phosphorylation in regulating MOR signaling, as well as our understanding of circuits and signaling pathways mediating physiologic behaviors such as respiratory control, and discuss how electrophysiological tools combined with new technologies have and will continue to advance the field of opioid research.
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Affiliation(s)
- William T Birdsong
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (W.T.B.) and Vollum Institute, Oregon Health & Science University, Portland, Oregon (J.T.W.)
| | - John T Williams
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan (W.T.B.) and Vollum Institute, Oregon Health & Science University, Portland, Oregon (J.T.W.)
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14
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Arttamangkul S, Leff ER, Koita O, Birdsong WT, Williams JT. Separation of Acute Desensitization and Long-Term Tolerance of µ-Opioid Receptors Is Determined by the Degree of C-Terminal Phosphorylation. Mol Pharmacol 2019; 96:505-514. [PMID: 31383769 DOI: 10.1124/mol.119.117358] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 08/02/2019] [Indexed: 01/22/2023] Open
Abstract
Phosphorylation of sites on the C terminus of the μ-opioid receptor (MOR) results in the induction of acute desensitization that is thought to be a precursor for the development of long-term tolerance. Alanine mutations of all 11 phosphorylation sites on the C terminus of MORs almost completely abolished desensitization and one measure of tolerance in locus coeruleus neurons when these phosphorylation-deficient MORs were virally expressed in MOR knockout rats. In the present work, we identified specific residues that underlie acute desensitization, receptor internalization, and tolerance and examined four MOR variants with different alanine or glutamate mutations in the C terminus. Alanine mutations in the sequence between amino acids 375 and 379 (STANT-3A) and the sequence between amino acids 363 and 394 having four additional alanine substitutions (STANT + 7A) reduced desensitization and two measures of long-term tolerance. After chronic morphine treatment, alanine mutations in the sequence between 354 and 357 (TSST-4A) blocked one measure of long-term tolerance (increased acute desensitization and slowed recovery from desensitization) but did not change a second (decreased sensitivity to morphine). With the expression of receptors having glutamate substitutions in the TSST sequence (TSST-4E), an increase in acute desensitization was present after chronic morphine treatment, but the sensitivity to morphine was not changed. The results show that all 11 phosphorylation sites contribute, in varying degrees, to acute desensitization and long-term tolerance. That acute desensitization and tolerance are not necessarily linked illustrates the complexity of events that are triggered by chronic treatment with morphine. SIGNIFICANCE STATEMENT: In this work, we showed that the degree of phosphorylation on the C terminus of the μ-opioid receptor alters acute desensitization and internalization, and in measures of long-term tolerance to morphine. The primary conclusion is that the degree of phosphorylation on the 11 possible sites of the C terminus has different roles for expression of the multiple adaptive mechanisms that follow acute and long-term agonist activation. Although the idea that acute desensitization and tolerance are intimately linked is generally supported, these results indicate that disruption of one phosphorylation cassette of the C terminus TSST (354-357) distinguishes the two processes.
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Affiliation(s)
| | - Emily R Leff
- Vollum Institute, Oregon Health & Science University, Portland, Oregon
| | - Omar Koita
- Vollum Institute, Oregon Health & Science University, Portland, Oregon
| | | | - John T Williams
- Vollum Institute, Oregon Health & Science University, Portland, Oregon
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15
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Emery MA, Eitan S. Members of the same pharmacological family are not alike: Different opioids, different consequences, hope for the opioid crisis? Prog Neuropsychopharmacol Biol Psychiatry 2019; 92:428-449. [PMID: 30790677 DOI: 10.1016/j.pnpbp.2019.02.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 02/15/2019] [Accepted: 02/15/2019] [Indexed: 01/14/2023]
Abstract
Pain management is the specialized medical practice of modulating pain perception and thus easing the suffering and improving the life quality of individuals suffering from painful conditions. Since this requires the modulation of the activity of endogenous systems involved in pain perception, and given the large role that the opioidergic system plays in pain perception, opioids are currently the most effective pain treatment available and are likely to remain relevant for the foreseeable future. This contributes to the rise in opioid use, misuse, and overdose death, which is currently characterized by public health officials in the United States as an epidemic. Historically, the majority of preclinical rodent studies were focused on morphine. This has resulted in our understanding of opioids in general being highly biased by our knowledge of morphine specifically. However, recent in vitro studies suggest that direct extrapolation of research findings from morphine to other opioids is likely to be flawed. Notably, these studies suggest that different opioid analgesics (opioid agonists) engage different downstream signaling effects within the cell, despite binding to and activating the same receptors. This recognition implies that, in contrast to the historical status quo, different opioids cannot be made equivalent by merely dose adjustment. Notably, even at equianalgesic doses, different opioids could result in different beneficial and risk outcomes. In order to foster further translational research regarding drug-specific differences among opioids, here we review basic research elucidating differences among opioids in pharmacokinetics, pharmacodynamics, their capacity for second messenger pathway activation, and their interactions with the immune system and the dopamine D2 receptors.
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Affiliation(s)
- Michael A Emery
- Behavioral and Cellular Neuroscience, Department of Psychological and Brain Sciences, Texas A&M University, 4235 TAMU, College Station, TX 77843, USA; Interdisciplinary Program in Neuroscience, Texas A&M Institute for Neuroscience (TAMIN), College Station, TX, USA
| | - Shoshana Eitan
- Behavioral and Cellular Neuroscience, Department of Psychological and Brain Sciences, Texas A&M University, 4235 TAMU, College Station, TX 77843, USA; Interdisciplinary Program in Neuroscience, Texas A&M Institute for Neuroscience (TAMIN), College Station, TX, USA.
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16
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Fumagalli A, Zarca A, Neves M, Caspar B, Hill SJ, Mayor F, Smit MJ, Marin P. CXCR4/ACKR3 Phosphorylation and Recruitment of Interacting Proteins: Key Mechanisms Regulating Their Functional Status. Mol Pharmacol 2019; 96:794-808. [PMID: 30837297 DOI: 10.1124/mol.118.115360] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 02/21/2019] [Indexed: 01/14/2023] Open
Abstract
The C-X-C motif chemokine receptor type 4 (CXCR4) and the atypical chemokine receptor 3 (ACKR3/CXCR7) are class A G protein-coupled receptors (GPCRs). Accumulating evidence indicates that GPCR subcellular localization, trafficking, transduction properties, and ultimately their pathophysiological functions are regulated by both interacting proteins and post-translational modifications. This has encouraged the development of novel techniques to characterize the GPCR interactome and to identify residues subjected to post-translational modifications, with a special focus on phosphorylation. This review first describes state-of-the-art methods for the identification of GPCR-interacting proteins and GPCR phosphorylated sites. In addition, we provide an overview of the current knowledge of CXCR4 and ACKR3 post-translational modifications and an exhaustive list of previously identified CXCR4- or ACKR3-interacting proteins. We then describe studies highlighting the importance of the reciprocal influence of CXCR4/ACKR3 interactomes and phosphorylation states. We also discuss their impact on the functional status of each receptor. These studies suggest that deeper knowledge of the CXCR4/ACKR3 interactomes along with their phosphorylation and ubiquitination status would shed new light on their regulation and pathophysiological functions.
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Affiliation(s)
- Amos Fumagalli
- IGF, Université de Montpellier, CNRS, INSERM, Montpellier, France (A.F., P.M.); Division of Medicinal Chemistry, Faculty of Science, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands (A.Z., M.J.S.); Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa" (UAM-CSIC), Madrid, Spain (M.N., F.M.); CIBERCV, Instituto de Salud Carlos III, Madrid, Spain (M.N., F.M.); and Division of Physiology, Pharmacology and Neuroscience, Medical School, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (B.C., S.J.H.)
| | - Aurélien Zarca
- IGF, Université de Montpellier, CNRS, INSERM, Montpellier, France (A.F., P.M.); Division of Medicinal Chemistry, Faculty of Science, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands (A.Z., M.J.S.); Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa" (UAM-CSIC), Madrid, Spain (M.N., F.M.); CIBERCV, Instituto de Salud Carlos III, Madrid, Spain (M.N., F.M.); and Division of Physiology, Pharmacology and Neuroscience, Medical School, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (B.C., S.J.H.)
| | - Maria Neves
- IGF, Université de Montpellier, CNRS, INSERM, Montpellier, France (A.F., P.M.); Division of Medicinal Chemistry, Faculty of Science, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands (A.Z., M.J.S.); Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa" (UAM-CSIC), Madrid, Spain (M.N., F.M.); CIBERCV, Instituto de Salud Carlos III, Madrid, Spain (M.N., F.M.); and Division of Physiology, Pharmacology and Neuroscience, Medical School, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (B.C., S.J.H.)
| | - Birgit Caspar
- IGF, Université de Montpellier, CNRS, INSERM, Montpellier, France (A.F., P.M.); Division of Medicinal Chemistry, Faculty of Science, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands (A.Z., M.J.S.); Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa" (UAM-CSIC), Madrid, Spain (M.N., F.M.); CIBERCV, Instituto de Salud Carlos III, Madrid, Spain (M.N., F.M.); and Division of Physiology, Pharmacology and Neuroscience, Medical School, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (B.C., S.J.H.)
| | - Stephen J Hill
- IGF, Université de Montpellier, CNRS, INSERM, Montpellier, France (A.F., P.M.); Division of Medicinal Chemistry, Faculty of Science, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands (A.Z., M.J.S.); Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa" (UAM-CSIC), Madrid, Spain (M.N., F.M.); CIBERCV, Instituto de Salud Carlos III, Madrid, Spain (M.N., F.M.); and Division of Physiology, Pharmacology and Neuroscience, Medical School, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (B.C., S.J.H.)
| | - Federico Mayor
- IGF, Université de Montpellier, CNRS, INSERM, Montpellier, France (A.F., P.M.); Division of Medicinal Chemistry, Faculty of Science, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands (A.Z., M.J.S.); Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa" (UAM-CSIC), Madrid, Spain (M.N., F.M.); CIBERCV, Instituto de Salud Carlos III, Madrid, Spain (M.N., F.M.); and Division of Physiology, Pharmacology and Neuroscience, Medical School, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (B.C., S.J.H.)
| | - Martine J Smit
- IGF, Université de Montpellier, CNRS, INSERM, Montpellier, France (A.F., P.M.); Division of Medicinal Chemistry, Faculty of Science, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands (A.Z., M.J.S.); Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa" (UAM-CSIC), Madrid, Spain (M.N., F.M.); CIBERCV, Instituto de Salud Carlos III, Madrid, Spain (M.N., F.M.); and Division of Physiology, Pharmacology and Neuroscience, Medical School, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (B.C., S.J.H.)
| | - Philippe Marin
- IGF, Université de Montpellier, CNRS, INSERM, Montpellier, France (A.F., P.M.); Division of Medicinal Chemistry, Faculty of Science, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands (A.Z., M.J.S.); Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa" (UAM-CSIC), Madrid, Spain (M.N., F.M.); CIBERCV, Instituto de Salud Carlos III, Madrid, Spain (M.N., F.M.); and Division of Physiology, Pharmacology and Neuroscience, Medical School, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom (B.C., S.J.H.)
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17
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Kliewer A, Schmiedel F, Sianati S, Bailey A, Bateman JT, Levitt ES, Williams JT, Christie MJ, Schulz S. Phosphorylation-deficient G-protein-biased μ-opioid receptors improve analgesia and diminish tolerance but worsen opioid side effects. Nat Commun 2019; 10:367. [PMID: 30664663 PMCID: PMC6341117 DOI: 10.1038/s41467-018-08162-1] [Citation(s) in RCA: 207] [Impact Index Per Article: 41.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 12/18/2018] [Indexed: 12/12/2022] Open
Abstract
Opioid analgesics are powerful pain relievers; however, over time, pain control diminishes as analgesic tolerance develops. The molecular mechanisms initiating tolerance have remained unresolved to date. We have previously shown that desensitization of the μ-opioid receptor and interaction with β-arrestins is controlled by carboxyl-terminal phosphorylation. Here we created knockin mice with a series of serine- and threonine-to-alanine mutations that render the receptor increasingly unable to recruit β-arrestins. Desensitization is inhibited in locus coeruleus neurons of mutant mice. Opioid-induced analgesia is strongly enhanced and analgesic tolerance is greatly diminished. Surprisingly, respiratory depression, constipation, and opioid withdrawal signs are unchanged or exacerbated, indicating that β-arrestin recruitment does not contribute to the severity of opioid side effects and, hence, predicting that G-protein-biased µ-agonists are still likely to elicit severe adverse effects. In conclusion, our findings identify carboxyl-terminal multisite phosphorylation as key step that drives acute μ-opioid receptor desensitization and long-term tolerance.
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Affiliation(s)
- A Kliewer
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-University, 07747, Jena, Germany
| | - F Schmiedel
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-University, 07747, Jena, Germany
| | - S Sianati
- Discipline of Pharmacology, School of Medical Sciences, University of Sydney, NSW, 2006, Australia
| | - A Bailey
- Institute of Medical and Biomedical Education, St George's University of London, London, SW17 ORE, UK
| | - J T Bateman
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, 32608, USA
| | - E S Levitt
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, 32608, USA
| | - J T Williams
- The Vollum Institute, Oregon Health and Science University, 3181S.W. Sam Jackson Pk. Rd., Portland, OR, 97239, USA
| | - M J Christie
- Discipline of Pharmacology, School of Medical Sciences, University of Sydney, NSW, 2006, Australia
| | - S Schulz
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-University, 07747, Jena, Germany.
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18
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Arttamangkul S, Heinz DA, Bunzow JR, Song X, Williams JT. Cellular tolerance at the µ-opioid receptor is phosphorylation dependent. eLife 2018; 7:34989. [PMID: 29589831 PMCID: PMC5873894 DOI: 10.7554/elife.34989] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 03/12/2018] [Indexed: 12/13/2022] Open
Abstract
Phosphorylation of the μ-opioid receptor (MOR) is known as a key step in desensitization and internalization but the role in the development of long-term tolerance at the cellular level is not known. Viral expression of wild type (exWT) and mutant MORs, where all phosphorylation sites on the C-terminus (Total Phosphorylation Deficient (TPD)) were mutated to alanine, were examined in locus coeruleus neurons in a MOR knockout rat. Both receptors activated potassium conductance similar to endogenous receptors in wild type animals. The exWT receptors, like endogenous receptors, acutely desensitized, internalized and, after chronic morphine treatment, displayed signs of tolerance. However, TPD receptors did not desensitize or internalize with agonist treatment. In addition the TPD receptors did not develop cellular tolerance following chronic morphine treatment. Thus C-terminal phosphorylation is necessary for the expression of acute desensitization, trafficking and one sign of long-term tolerance to morphine at the cellular level.
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Affiliation(s)
- Seksiri Arttamangkul
- The Vollum Institute, Oregon Health and Science University, Oregon, United States
| | - Daniel A Heinz
- The Vollum Institute, Oregon Health and Science University, Oregon, United States
| | - James R Bunzow
- The Vollum Institute, Oregon Health and Science University, Oregon, United States
| | - Xianqiang Song
- The Vollum Institute, Oregon Health and Science University, Oregon, United States
| | - John T Williams
- The Vollum Institute, Oregon Health and Science University, Oregon, United States
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19
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Chiu YT, Chen C, Yu D, Schulz S, Liu-Chen LY. Agonist-Dependent and -Independent κ Opioid Receptor Phosphorylation: Distinct Phosphorylation Patterns and Different Cellular Outcomes. Mol Pharmacol 2017; 92:588-600. [PMID: 28893975 DOI: 10.1124/mol.117.108555] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 08/10/2017] [Indexed: 01/21/2023] Open
Abstract
We reported previously that the selective agonist U50,488H promoted phosphorylation of the mouse κ opioid receptor (KOPR) at residues S356, T357, T363, and S369. Here, we found that agonist (U50,488H)-dependent KOPR phosphorylation at all the residues was mediated by Gi/o α proteins and multiple protein kinases [GRK2, GRK3, GRK5, GRK6 and protein kinase C (PKC)]. In addition, PKC activation by phorbol ester induced agonist-independent KOPR phosphorylation. Compared with U50,488H, PKC activation promoted much higher S356/T357 phosphorylation, much lower T363 phosphorylation, and similar levels of S369 phosphorylation. After U50,488H treatment, GRKs, but not PKC, were involved in agonist-induced KOPR internalization. In contrast, PKC activation caused a lower level of agonist-independent KOPR internalization, compared with U50,488H. U50,488H-induced activation of extracellular signal-regulated kinase 1/2 (ERK1/2) was G protein-, but not β-arrestin-, dependent. After U50,488H treatment, GRK-mediated, but not PKC-mediated, KOPR phosphorylation followed by β-arrestin recruitment desensitized U50,488H-induced ERK1/2 response. Therefore, agonist-dependent (GRK- and PKC-mediated) and agonist-independent (PKC-promoted) KOPR phosphorylations show distinct phosphorylation patterns, leading to diverse cellular outcomes.
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Affiliation(s)
- Yi-Ting Chiu
- Center for Substance Abuse Research and Department of Pharmacology (Y.-T.C., C.C., L.-Y.L.-C.) and Department of Clinical Sciences (D.Y.), Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania; and Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-University, Jena, Germany (S.S.)
| | - Chongguang Chen
- Center for Substance Abuse Research and Department of Pharmacology (Y.-T.C., C.C., L.-Y.L.-C.) and Department of Clinical Sciences (D.Y.), Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania; and Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-University, Jena, Germany (S.S.)
| | - Daohai Yu
- Center for Substance Abuse Research and Department of Pharmacology (Y.-T.C., C.C., L.-Y.L.-C.) and Department of Clinical Sciences (D.Y.), Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania; and Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-University, Jena, Germany (S.S.)
| | - Stefan Schulz
- Center for Substance Abuse Research and Department of Pharmacology (Y.-T.C., C.C., L.-Y.L.-C.) and Department of Clinical Sciences (D.Y.), Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania; and Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-University, Jena, Germany (S.S.)
| | - Lee-Yuan Liu-Chen
- Center for Substance Abuse Research and Department of Pharmacology (Y.-T.C., C.C., L.-Y.L.-C.) and Department of Clinical Sciences (D.Y.), Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania; and Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-University, Jena, Germany (S.S.)
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20
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Yang Z, Yang F, Zhang D, Liu Z, Lin A, Liu C, Xiao P, Yu X, Sun JP. Phosphorylation of G Protein-Coupled Receptors: From the Barcode Hypothesis to the Flute Model. Mol Pharmacol 2017; 92:201-210. [DOI: 10.1124/mol.116.107839] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Accepted: 02/23/2017] [Indexed: 12/21/2022] Open
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21
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Shim JY, Khurana L, Kendall DA. Computational analysis of the CB1 carboxyl-terminus in the receptor-G protein complex. Proteins 2016; 84:532-43. [PMID: 26994549 DOI: 10.1002/prot.24999] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 01/07/2016] [Accepted: 01/19/2016] [Indexed: 01/03/2023]
Abstract
Despite the important role of the carboxyl-terminus (Ct) of the activated brain cannabinoid receptor one (CB1) in the regulation of G protein signaling, a structural understanding of interactions with G proteins is lacking. This is largely due to the highly flexible nature of the CB1 Ct that dynamically adapts its conformation to the presence of G proteins. In the present study, we explored how the CB1 Ct can interact with the G protein by building on our prior modeling of the CB1-Gi complex (Shim, Ahn, and Kendall, The Journal of Biological Chemistry 2013;288:32449-32465) to incorporate a complete CB1 Ct (Glu416(Ct)-Leu472(Ct)). Based on the structural constraints from NMR studies, we employed ROSETTA to predict tertiary folds, ZDOCK to predict docking orientation, and molecular dynamics (MD) simulations to obtain two distinct plausible models of CB1 Ct in the CB1-Gi complex. The resulting models were consistent with the NMR-determined helical structure (H9) in the middle region of the CB1 Ct. The CB1 Ct directly interacted with both Gα and Gβ and stabilized the receptor at the Gi interface. The results of site-directed mutagenesis studies of Glu416(Ct), Asp423(Ct), Asp428(Ct), and Arg444(Ct) of CB1 Ct suggested that the CB1 Ct can influence receptor-G protein coupling by stabilizing the receptor at the Gi interface. This research provided, for the first time, models of the CB1 Ct in contact with the G protein.
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Affiliation(s)
- Joong-Youn Shim
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina, 27514
| | - Leepakshi Khurana
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut, 06269-3092
| | - Debra A Kendall
- Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut, 06269-3092
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22
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Moulédous L, Froment C, Burlet-Schiltz O, Schulz S, Mollereau C. Phosphoproteomic analysis of the mouse brain mu-opioid (MOP) receptor. FEBS Lett 2015; 589:2401-8. [PMID: 26226422 DOI: 10.1016/j.febslet.2015.07.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 07/03/2015] [Accepted: 07/20/2015] [Indexed: 11/19/2022]
Abstract
Many in vitro data have shown that the efficacy of several opioid drugs is correlated with differential mu-opioid (MOP) receptor phosphorylation. Label-free semiquantitative on-line nanoflow liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) analyses were performed to compare the endogenous MOP receptor phosphorylation patterns of mice administered with morphine, etonitazene and fentanyl. The analysis identified S363, T370 and S375 as phosphorylated residues in the carboxy-terminus. Only T370 and S375 were regulated by agonists, with a higher propensity to promote double phosphorylation for high efficacy agonists. Our study provides confirmation that differential agonist-driven multi-site phosphorylation of MOP receptor occurs in vivo and validate the use of MS to study endogenous GPCR phosphorylation.
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Affiliation(s)
- Lionel Moulédous
- Institut de Pharmacologie et Biologie Structurale CNRS/Université de Toulouse, 205 route de Narbonne, 31077 Toulouse, France
| | - Carine Froment
- Institut de Pharmacologie et Biologie Structurale CNRS/Université de Toulouse, 205 route de Narbonne, 31077 Toulouse, France
| | - Odile Burlet-Schiltz
- Institut de Pharmacologie et Biologie Structurale CNRS/Université de Toulouse, 205 route de Narbonne, 31077 Toulouse, France
| | - Stefan Schulz
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich Schiller University Jena, Drackendorfer Strasse 1, 07747 Jena, Germany.
| | - Catherine Mollereau
- Institut de Pharmacologie et Biologie Structurale CNRS/Université de Toulouse, 205 route de Narbonne, 31077 Toulouse, France.
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23
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Inagaki S, Ghirlando R, Vishnivetskiy SA, Homan KT, White JF, Tesmer JJG, Gurevich VV, Grisshammer R. G Protein-Coupled Receptor Kinase 2 (GRK2) and 5 (GRK5) Exhibit Selective Phosphorylation of the Neurotensin Receptor in Vitro. Biochemistry 2015; 54:4320-9. [PMID: 26120872 PMCID: PMC4512254 DOI: 10.1021/acs.biochem.5b00285] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
![]()
G protein-coupled
receptor kinases (GRKs) play an important role
in the desensitization of G protein-mediated signaling of G protein-coupled
receptors (GPCRs). The level of interest in mapping their phosphorylation
sites has increased because recent studies suggest that the differential
pattern of receptor phosphorylation has distinct biological consequences. In vitro phosphorylation experiments using well-controlled
systems are useful for deciphering the complexity of these physiological
reactions and understanding the targeted event. Here, we report on
the phosphorylation of the class A GPCR neurotensin receptor 1 (NTSR1)
by GRKs under defined experimental conditions afforded by nanodisc
technology. Phosphorylation of NTSR1 by GRK2 was agonist-dependent,
whereas phosphorylation by GRK5 occurred in an activation-independent
manner. In addition, the negatively charged lipids in the immediate
vicinity of NTSR1 directly affect phosphorylation by GRKs. Identification
of phosphorylation sites in agonist-activated NTSR1 revealed that
GRK2 and GRK5 target different residues located on the intracellular
receptor elements. GRK2 phosphorylates only the C-terminal Ser residues,
whereas GRK5 phosphorylates Ser and Thr residues located in intracellular
loop 3 and the C-terminus. Interestingly, phosphorylation assays using
a series of NTSR1 mutants show that GRK2 does not require acidic residues
upstream of the phospho-acceptors for site-specific phosphorylation,
in contrast to the β2-adrenergic and μ-opioid
receptors. Differential phosphorylation of GPCRs by GRKs is thought
to encode a particular signaling outcome, and our in vitro study revealed NTSR1 differential phosphorylation by GRK2 and GRK5.
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Affiliation(s)
- Sayaka Inagaki
- †Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - Rodolfo Ghirlando
- ‡Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892, United States
| | - Sergey A Vishnivetskiy
- §Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Kristoff T Homan
- ∥Departments of Pharmacology and Biological Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Jim F White
- †Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
| | - John J G Tesmer
- ∥Departments of Pharmacology and Biological Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Vsevolod V Gurevich
- §Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Reinhard Grisshammer
- †Membrane Protein Structure Function Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland 20852, United States
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Prihandoko R, Bradley SJ, Tobin AB, Butcher AJ. Determination of GPCR Phosphorylation Status: Establishing a Phosphorylation Barcode. ACTA ACUST UNITED AC 2015; 69:2.13.1-2.13.26. [PMID: 26344213 DOI: 10.1002/0471141755.ph0213s69] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
G protein-coupled receptors (GPCRs) are rapidly phosphorylated following agonist occupation in a process that mediates receptor uncoupling from its cognate G protein, a process referred to as desensitization. In addition, this process provides a mechanism by which receptors can engage with arrestin adaptor molecules and couple to downstream signaling pathways. The importance of this regulatory process has been highlighted recently by the understanding that ligands can direct receptor signaling along one pathway in preference to another, the phenomenon of signaling bias that is partly mediated by the phosphorylation status or phosphorylation barcode of the receptor. Methods to determine the phosphorylation status of a GPCR in vitro and in vivo are necessary to understand not only the physiological mechanisms involved in GPCR signaling, but also to fully examine the signaling properties of GPCR ligands. This unit describes detailed methods for determining the overall phosphorylation pattern on a receptor (the phosphorylation barcode), as well as mass spectrometry approaches that can define the precise sites that become phosphorylated. These techniques, coupled with the generation and characterization of receptor phosphorylation-specific antibodies, provide a full palate of techniques necessary to determine the phosphorylation status of any given GPCR subtype.
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Affiliation(s)
- Rudi Prihandoko
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Sophie J Bradley
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Andrew B Tobin
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Adrian J Butcher
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
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Thompson GL, Lane JR, Coudrat T, Sexton PM, Christopoulos A, Canals M. Biased Agonism of Endogenous Opioid Peptides at the μ-Opioid Receptor. Mol Pharmacol 2015; 88:335-46. [PMID: 26013541 DOI: 10.1124/mol.115.098848] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 05/26/2015] [Indexed: 01/14/2023] Open
Abstract
Biased agonism is having a major impact on modern drug discovery, and describes the ability of distinct G protein-coupled receptor (GPCR) ligands to activate different cell signaling pathways, and to result in different physiologic outcomes. To date, most studies of biased agonism have focused on synthetic molecules targeting various GPCRs; however, many of these receptors have multiple endogenous ligands, suggesting that "natural" bias may be an unappreciated feature of these GPCRs. The μ-opioid receptor (MOP) is activated by numerous endogenous opioid peptides, remains an attractive therapeutic target for the treatment of pain, and exhibits biased agonism in response to synthetic opiates. The aim of this study was to rigorously assess the potential for biased agonism in the actions of endogenous opioids at the MOP in a common cellular background, and compare these to the effects of the agonist d-Ala2-N-MePhe4-Gly-ol enkephalin (DAMGO). We investigated activation of G proteins, inhibition of cAMP production, extracellular signal-regulated kinase 1 and 2 phosphorylation, β-arrestin 1/2 recruitment, and MOP trafficking, and applied a novel analytical method to quantify biased agonism. Although many endogenous opioids displayed signaling profiles similar to that of DAMGO, α-neoendorphin, Met-enkephalin-Arg-Phe, and the putatively endogenous peptide endomorphin-1 displayed particularly distinct bias profiles. These may represent examples of natural bias if it can be shown that they have different signaling properties and physiologic effects in vivo compared with other endogenous opioids. Understanding how endogenous opioids control physiologic processes through biased agonism can reveal vital information required to enable the design of biased opioids with improved pharmacological profiles and treat diseases involving dysfunction of the endogenous opioid system.
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Affiliation(s)
- Georgina L Thompson
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (G.L.T., J.R.L., T.C., P.M.S., A.C., M.C.); and Defence Science and Technology Organisation, Department of Defence, Fishermans Bend, Victoria, Australia (G.L.T.)
| | - J Robert Lane
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (G.L.T., J.R.L., T.C., P.M.S., A.C., M.C.); and Defence Science and Technology Organisation, Department of Defence, Fishermans Bend, Victoria, Australia (G.L.T.)
| | - Thomas Coudrat
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (G.L.T., J.R.L., T.C., P.M.S., A.C., M.C.); and Defence Science and Technology Organisation, Department of Defence, Fishermans Bend, Victoria, Australia (G.L.T.)
| | - Patrick M Sexton
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (G.L.T., J.R.L., T.C., P.M.S., A.C., M.C.); and Defence Science and Technology Organisation, Department of Defence, Fishermans Bend, Victoria, Australia (G.L.T.)
| | - Arthur Christopoulos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (G.L.T., J.R.L., T.C., P.M.S., A.C., M.C.); and Defence Science and Technology Organisation, Department of Defence, Fishermans Bend, Victoria, Australia (G.L.T.)
| | - Meritxell Canals
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (G.L.T., J.R.L., T.C., P.M.S., A.C., M.C.); and Defence Science and Technology Organisation, Department of Defence, Fishermans Bend, Victoria, Australia (G.L.T.)
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26
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Lowe JD, Sanderson HS, Cooke AE, Ostovar M, Tsisanova E, Withey SL, Chavkin C, Husbands SM, Kelly E, Henderson G, Bailey CP. Role of G Protein-Coupled Receptor Kinases 2 and 3 in μ-Opioid Receptor Desensitization and Internalization. Mol Pharmacol 2015; 88:347-56. [PMID: 26013542 DOI: 10.1124/mol.115.098293] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 05/26/2015] [Indexed: 01/12/2023] Open
Abstract
There is ongoing debate about the role of G protein-coupled receptor kinases (GRKs) in agonist-induced desensitization of the μ-opioid receptor (MOPr) in brain neurons. In the present paper, we have used a novel membrane-permeable, small-molecule inhibitor of GRK2 and GRK3, Takeda compound 101 (Cmpd101; 3-[[[4-methyl-5-(4-pyridyl)-4H-1,2,4-triazole-3-yl] methyl] amino]-N-[2-(trifuoromethyl) benzyl] benzamidehydrochloride), to study the involvement of GRK2/3 in acute agonist-induced MOPr desensitization. We observed that Cmpd101 inhibits the desensitization of the G protein-activated inwardly-rectifying potassium current evoked by receptor-saturating concentrations of methionine-enkephalin (Met-Enk), [d-Ala(2), N-MePhe(4), Gly-ol(5)]-enkephalin (DAMGO), endomorphin-2, and morphine in rat and mouse locus coeruleus (LC) neurons. In LC neurons from GRK3 knockout mice, Met-Enk-induced desensitization was unaffected, implying a role for GRK2 in MOPr desensitization. Quantitative analysis of the loss of functional MOPrs following acute agonist exposure revealed that Cmpd101 only partially reversed MOPr desensitization. Inhibition of extracellular signal-regulated kinase 1/2, protein kinase C, c-Jun N-terminal kinase, or GRK5 did not inhibit the Cmpd101-insensitive component of desensitization. In HEK 293 cells, Cmpd101 produced almost complete inhibition of DAMGO-induced MOPr phosphorylation at Ser(375), arrestin translocation, and MOPr internalization. Our data demonstrate a role for GRK2 (and potentially also GRK3) in agonist-induced MOPr desensitization in the LC, but leave open the possibility that another, as yet unidentified, mechanism of desensitization also exists.
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Affiliation(s)
- Janet D Lowe
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Helen S Sanderson
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Alexandra E Cooke
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Mehrnoosh Ostovar
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Elena Tsisanova
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Sarah L Withey
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Charles Chavkin
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Stephen M Husbands
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Eamonn Kelly
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Graeme Henderson
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
| | - Chris P Bailey
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (J.D.L., H.S.S., A.E.C., E.T., S.L.W., E.K., G.H.); Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington (C.C.); and Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (M.O., S.M.H., C.P.B.)
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Birdsong WT, Arttamangkul S, Bunzow JR, Williams JT. Agonist Binding and Desensitization of the μ-Opioid Receptor Is Modulated by Phosphorylation of the C-Terminal Tail Domain. Mol Pharmacol 2015; 88:816-24. [PMID: 25934731 DOI: 10.1124/mol.114.097527] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 04/30/2015] [Indexed: 11/22/2022] Open
Abstract
Sustained activation of G protein-coupled receptors can lead to a rapid decline in signaling through acute receptor desensitization. In the case of the μ-opioid receptor (MOPr), this desensitization may play a role in the development of analgesic tolerance. It is understood that phosphorylation of MOPr promotes association with β-arrestin proteins, which then facilitates desensitization and receptor internalization. Agonists that induce acute desensitization have been shown to induce a noncanonical high-affinity agonist binding state in MOPr, conferring a persistent memory of prior receptor activation. In the current study, live-cell confocal imaging was used to investigate the role of receptor phosphorylation in agonist binding to MOPr. A phosphorylation cluster in the C-terminal tail of MOPr was identified as a mediator of agonist-induced affinity changes in MOPr. This site is unique from the primary phosphorylation cluster responsible for β-arrestin binding and internalization. Electrophysiologic measurements of receptor function suggest that both phosphorylation clusters may play a parallel role during acute receptor desensitization. Desensitization was unaffected by alanine mutation of either phosphorylation cluster, but was largely eliminated when both clusters were mutated. Overall, this work suggests that there are multiple effects of MOPr phosphorylation that appear to regulate MOPr function: one affecting β-arrestin binding and a second affecting agonist binding.
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Affiliation(s)
| | | | - James R Bunzow
- Vollum Institute, Oregon Health & Science University, Portland, Oregon
| | - John T Williams
- Vollum Institute, Oregon Health & Science University, Portland, Oregon
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Rodríguez-Muñoz M, Sánchez-Blázquez P, Herrero-Labrador R, Martínez-Murillo R, Merlos M, Vela JM, Garzón J. The σ1 receptor engages the redox-regulated HINT1 protein to bring opioid analgesia under NMDA receptor negative control. Antioxid Redox Signal 2015; 22:799-818. [PMID: 25557043 PMCID: PMC4367239 DOI: 10.1089/ars.2014.5993] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 12/16/2014] [Accepted: 01/01/2015] [Indexed: 12/12/2022]
Abstract
AIMS The in vivo pharmacology of the sigma 1 receptor (σ1R) is certainly complex; however, σ1R antagonists are of therapeutic interest, because they enhance mu-opioid receptor (MOR)-mediated antinociception and reduce neuropathic pain. Thus, we investigated whether the σ1R is involved in the negative control that glutamate N-methyl-d-aspartate acid receptors (NMDARs) exert on opioid antinociception. RESULTS The MOR C terminus carries the histidine triad nucleotide-binding protein 1 (HINT1) coupled to the regulator of G-protein signaling RGSZ2-neural nitric oxide synthase assembly. Activated MORs stimulate the production of nitric oxide (NO), and the redox zinc switch RGSZ2 converts this signal into free zinc ions that are required to recruit the redox sensor PKCγ to HINT1 proteins. Then, PKCγ impairs HINT1-RGSZ2 association and enables σ1R-NR1 interaction with MOR-HINT1 complexes to restrain opioid signaling. The inhibition of NOS or the absence of σ1Rs prevents HINT1-PKCγ interaction, and MOR-NMDAR cross-regulation fails. The σ1R antagonists transitorily remove the binding of σ1Rs to NR1 subunits, facilitate the entrance of negative regulators of NMDARs, likely Ca(2+)-CaM, and prevent NR1 interaction with HINT1, thereby impairing the negative feedback of glutamate on opioid analgesia. INNOVATION A redox-regulated process situates MOR signaling under NMDAR control, and in this context, the σ1R binds to the cytosolic C terminal region of the NMDAR NR1 subunit. CONCLUSION The σ1R antagonists enhance opioid analgesia in naïve mice by releasing MORs from the negative influence of NMDARs, and they also reset antinociception in morphine tolerant animals. Moreover, σ1R antagonists alleviate neuropathic pain, probably by driving the inhibition of up-regulated NMDARs.
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Affiliation(s)
- María Rodríguez-Muñoz
- Neurofarmacología, Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Pilar Sánchez-Blázquez
- Neurofarmacología, Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Raquel Herrero-Labrador
- Neurofarmacología, Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Ricardo Martínez-Murillo
- Neurofarmacología, Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Manuel Merlos
- Drug Discovery & Preclinical Development, Esteve, Barcelona, Spain
| | - José Miguel Vela
- Drug Discovery & Preclinical Development, Esteve, Barcelona, Spain
| | - Javier Garzón
- Neurofarmacología, Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
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29
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Garzón J, Herrero-Labrador R, Rodríguez-Muñoz M, Shah R, Vicente-Sánchez A, Wagner CR, Sánchez-Blázquez P. HINT1 protein: A new therapeutic target to enhance opioid antinociception and block mechanical allodynia. Neuropharmacology 2015; 89:412-23. [DOI: 10.1016/j.neuropharm.2014.10.022] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 10/21/2014] [Accepted: 10/27/2014] [Indexed: 12/17/2022]
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Arttamangkul S, Birdsong W, Williams JT. Does PKC activation increase the homologous desensitization of μ opioid receptors? Br J Pharmacol 2015; 172:583-92. [PMID: 24697621 PMCID: PMC4292970 DOI: 10.1111/bph.12712] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 03/19/2014] [Accepted: 03/23/2014] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND AND PURPOSE This study examined the role of agents known to activate PKC on morphine-induced desensitization of μ-opioid receptors (MOP receptors) in brain slices containing locus coeruleus neurons. EXPERIMENTAL APPROACH Intracellular recordings were obtained from rat locus coeruleus neurons. Two measurements were used to characterize desensitization, the decline in hyperpolarization induced by application of a saturating concentration of agonist (acute desensitization) and the decrease in hyperpolarization induced by a subsaturating concentration of [Met](5) enkephalin (ME) following washout of the saturating concentration (sustained desensitization). Internalization of MOP receptors was studied in brain slices prepared from transgenic mice expressing Flag-MOP receptors. The subcellular distribution of activated PKC was examined using a novel fluorescent sensor of PKC in HEK293 cells. KEY RESULTS The phorbol esters (PMA and PDBu) and muscarine increased acute desensitization induced by a saturating concentration of morphine and ME. These effects were not sensitive to staurosporine. Staurosporine did not block the decline in hyperpolarization induced by muscarine. PDBu and muscarine did not affect sustained desensitization induced by ME nor did phorbol esters or muscarine change the trafficking of MOP receptors induced by morphine or ME. The distribution of activated PKC measured in HEK293 cells differed depending on which phorbol ester was applied. CONCLUSIONS AND IMPLICATIONS This study demonstrates a distinct difference in two measurements that are often used to evaluate desensitization. The measure of decline correlated well with the reduction in peak amplitudes caused by PKC activators implicating the modification of other factors rather than MOP receptors. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Allouche S, Noble F, Marie N. Opioid receptor desensitization: mechanisms and its link to tolerance. Front Pharmacol 2014; 5:280. [PMID: 25566076 PMCID: PMC4270172 DOI: 10.3389/fphar.2014.00280] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 12/02/2014] [Indexed: 02/04/2023] Open
Abstract
Opioid receptors (OR) are part of the class A of G-protein coupled receptors and the target of the opiates, the most powerful analgesic molecules used in clinic. During a protracted use, a tolerance to analgesic effect develops resulting in a reduction of the effectiveness. So understanding mechanisms of tolerance is a great challenge and may help to find new strategies to tackle this side effect. This review will summarize receptor-related mechanisms that could underlie tolerance especially receptor desensitization. We will focus on the latest data obtained on molecular mechanisms involved in opioid receptor desensitization: phosphorylation, receptor uncoupling, internalization, and post-endocytic fate of the receptor.
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Affiliation(s)
- Stéphane Allouche
- Laboratoire de Signalisation, Électrophysiologie et Imagerie des Lésions D'ischémie-Reperfusion Myocardique, Université de Caen, UPRES EA 4650, IFR 146 ICORE Caen, France
| | - Florence Noble
- Centre National de la Recherche Scientifique, ERL 3649 Paris, France ; Institut National de la Santé et de la Recherche Médicale, UMR-S 1124 Paris, France ; Université Paris Descartes, Neuroplasticité et Thérapies des Addictions Paris, France
| | - Nicolas Marie
- Centre National de la Recherche Scientifique, ERL 3649 Paris, France ; Institut National de la Santé et de la Recherche Médicale, UMR-S 1124 Paris, France ; Université Paris Descartes, Neuroplasticité et Thérapies des Addictions Paris, France
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Abstract
This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, United States.
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Illing S, Mann A, Schulz S. Heterologous regulation of agonist-independent μ-opioid receptor phosphorylation by protein kinase C. Br J Pharmacol 2014; 171:1330-40. [PMID: 24308893 DOI: 10.1111/bph.12546] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 11/12/2013] [Accepted: 12/02/2013] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND AND PURPOSE Homologous agonist-induced phosphorylation of the μ-opioid receptor (MOR) is initiated at the carboxyl-terminal S375, followed by phosphorylation of T370, T376 and T379. In HEK293 cells, this sequential and hierarchical multi-site phosphorylation is specifically mediated by G-protein coupled receptor kinases 2 and 3. In the present study, we provide evidence for a selective and dose-dependent phosphorylation of T370 after activation of PKC by phorbol esters. EXPERIMENTAL APPROACH We used a combination of phospho site-specific antibodies, kinase inhibitors and siRNA knockdown screening to identify kinases that mediate agonist-independent phosphorylation of the MOR in HEK293 cells. In addition, we show with phospho site-specific antibodies were also used to study constitutive phosphorylation at S363 of MORs in mouse brain in vivo. KEY RESULTS Activation of PKC by phorbol esters or heterologous activation of substance P receptors co-expressed with MORs in the same cell induced a selective and dose-dependent phosphorylation of T370 that specifically requires the PKCα isoform. Inhibition of PKC activity did not compromise homologous agonist-driven T370 phosphorylation. In addition, S363 was constitutively phosphorylated in both HEK293 cells and mouse brain in vivo. Constitutive S363 phosphorylation required ongoing PKC activity. When basal PKC activity was decreased, S363 was also a substrate for homologous agonist-stimulated phosphorylation. CONCLUSIONS AND IMPLICATIONS Our results have disclosed novel mechanisms of heterologous regulation of MOR phosphorylation by PKC. These findings represent a useful starting point for definitive experiments elucidating the exact contribution of PKC-driven MOR phosphorylation to diminished MOR responsiveness in morphine tolerance and pathological pain.
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Affiliation(s)
- Susann Illing
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich Schiller University Jena, Jena, Germany
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34
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Cooke AE, Oldfield S, Krasel C, Mundell SJ, Henderson G, Kelly E. Morphine-induced internalization of the L83I mutant of the rat μ-opioid receptor. Br J Pharmacol 2014; 172:593-605. [PMID: 24697554 DOI: 10.1111/bph.12709] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 03/17/2014] [Accepted: 03/26/2014] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND AND PURPOSE Naturally occurring single-nucleotide polymorphisms (SNPs) within GPCRs can result in alterations in various pharmacological parameters. Understanding the regulation and function of endocytic trafficking of the μ-opioid receptor (MOP receptor) is of great importance given its implication in the development of opioid tolerance. This study has compared the agonist-dependent trafficking and signalling of L83I, the rat orthologue of a naturally occurring variant of the MOP receptor. EXPERIMENTAL APPROACH Cell surface elisa, confocal microscopy and immunoprecipitation assays were used to characterize the trafficking properties of the MOP-L83I variant in comparison with the wild-type receptor in HEK 293 cells. Functional assays were used to compare the ability of the L83I variant to signal to several downstream pathways. KEY RESULTS Morphine-induced internalization of the L83I MOP receptor was markedly increased in comparison with the wild-type receptor. The altered trafficking of this variant was found to be specific to morphine and was both G-protein receptor kinase- and dynamin-dependent. The enhanced internalization of L83I variant in response to morphine was not due to increased phosphorylation of serine 375, arrestin association or an increased ability to signal. CONCLUSIONS AND IMPLICATIONS These results suggest that morphine promotes a specific conformation of the L83I variant that makes it more liable to internalize in response to morphine, unlike the wild-type receptor that undergoes significantly less morphine-stimulated internalization, providing an example of a ligand-selective biased receptor. The presence of this SNP within an individual may consequently affect the development of tolerance and analgesic responses. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- A E Cooke
- School of Physiology and Pharmacology, University of Bristol, Bristol, BS8 1TD, UK
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Mann A, Illing S, Miess E, Schulz S. Different mechanisms of homologous and heterologous μ-opioid receptor phosphorylation. Br J Pharmacol 2014; 172:311-6. [PMID: 24517854 DOI: 10.1111/bph.12627] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 01/16/2014] [Accepted: 01/19/2014] [Indexed: 01/14/2023] Open
Abstract
UNLABELLED The efficiency of μ-opioid receptor signalling is tightly regulated and ultimately limited by the coordinated phosphorylation of intracellular serine and threonine residues. Here, we review and discuss recent progress in the generation and application of phosphosite-specific μ-opioid receptor antibodies, which have proved to be excellent tools for monitoring the spatial and temporal dynamics of receptor phosphorylation and dephosphorylation. Agonist-induced phosphorylation of μ-opioid receptors occurs at a conserved 10 residue sequence (370) TREHPSTANT(379) in the receptor's carboxyl-terminal cytoplasmic tail. Diverse opioids induce receptor phosphorylation at S375, present in the middle of this sequence, but only high-efficacy opioids have the ability to drive higher order phosphorylation on flanking residues (T370, T376 and T379). S375 is the initiating residue in a hierarchical phosphorylation cascade. In contrast, agonist-independent heterologous μ-opioid receptor phosphorylation occurs primarily at T370. The combination of phosphosite-specific antibodies and siRNA knockdown screening also facilitated the identification of relevant kinases and phosphatases. In fact, morphine induces a selective S375 phosphorylation that is predominantly catalysed by GPCR kinase 5 (GRK5), whereas multisite phosphorylation induced by high-efficacy opioids specifically requires GRK2/3. By contrast, T370 phosphorylation stimulated by phorbol esters or heterologous activation of Gq -coupled receptors is mediated by PKCα. Rapid μ-opioid receptor dephosphorylation occurs at or near the plasma membrane and is catalysed by protein phosphatase 1γ (PP1γ). These findings suggest that there are distinct phosphorylation motifs for homologous and heterologous regulation of μ-opioid receptor phosphorylation. However, it remains to be seen to what extent different μ-opioid receptor phosphorylation patterns contribute to the development of tolerance and dependence in vivo. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
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Affiliation(s)
- Anika Mann
- Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich-Schiller-University, Jena, Germany
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Nickolls SA, Humphreys S, Clark M, McMurray G. Co-expression of GRK2 reveals a novel conformational state of the µ-opioid receptor. PLoS One 2013; 8:e83691. [PMID: 24376730 PMCID: PMC3869807 DOI: 10.1371/journal.pone.0083691] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 11/15/2013] [Indexed: 11/19/2022] Open
Abstract
Agonists at the µ-opioid receptor are known to produce potent analgesic responses in the clinical setting, therefore, an increased understanding of the molecular interactions of ligands at this receptor could lead to improved analgesics. As historically morphine has been shown to be a poor recruiter of β-arrestin in recombinant cell systems and this can be overcome by the co-expression of GRK2, we investigated the effects of GRK2 co-expression, in a recombinant µ-opioid receptor cell line, on ligand affinity and intrinsic activity in both β-arrestin recruitment and [(35)S]GTPγS binding assays. We also investigated the effect of receptor depletion in the β-arrestin assay. GRK2 co-expression increased both agonist Emax and potency in the β-arrestin assay. The increase in agonist potency could not be reversed using receptor depletion, supporting that the effects were due to a novel receptor conformation not system amplification. We also observed a small but significant effect on agonist KL values. Potency values in the [(35)S]GTPγS assay were unchanged; however, inverse agonist activity became evident with GRK2 co-expression. We conclude that this is direct evidence that the µ-opioid receptor is an allosteric protein and the co-expression of signalling molecules elicits changes in its conformation and thus ligand affinity. This has implications when describing how ligands interact with the receptor and how efficacy is determined.
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Affiliation(s)
- Sarah A. Nickolls
- Neusentis, A Pfizer Research Unit, Granta Park, Cambridge, United Kingdom
- * E-mail:
| | - Sian Humphreys
- Neusentis, A Pfizer Research Unit, Granta Park, Cambridge, United Kingdom
| | - Mellissa Clark
- Neusentis, A Pfizer Research Unit, Granta Park, Cambridge, United Kingdom
| | - Gordon McMurray
- Neusentis, A Pfizer Research Unit, Granta Park, Cambridge, United Kingdom
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Li G, Ma F, Gu Y, Huang LYM. Analgesic tolerance of opioid agonists in mutant mu-opioid receptors expressed in sensory neurons following intrathecal plasmid gene delivery. Mol Pain 2013; 9:63. [PMID: 24304623 PMCID: PMC3906983 DOI: 10.1186/1744-8069-9-63] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 11/22/2013] [Indexed: 11/12/2022] Open
Abstract
Background Phosphorylation sites in the C-terminus of mu-opioid receptors (MORs) are known to play critical roles in the receptor functions. Our understanding of their participation in opioid analgesia is mostly based on studies of opioid effects on mutant receptors expressed in in vitro preparations, including cell lines, isolated neurons and brain slices. The behavioral consequences of the mutation have not been fully explored due to the complexity in studies of mutant receptors in vivo. To facilitate the determination of the contribution of phosphorylation sites in MOR to opioid-induced analgesic behaviors, we expressed mutant and wild-type human MORs (hMORs) in sensory dorsal root ganglion (DRG) neurons, a major site for nociceptive (pain) signaling and determined morphine- and the full MOR agonist, DAMGO,-induced effects on heat-induced hyperalgesic behaviors and potassium current (IK) desensitization in these rats. Findings A mutant hMOR DNA with the putative phosphorylation threonine site at position 394 replaced by an alanine (T394A), i.e., hMOR-T, or a plasmid containing wild type hMOR (as a positive control) was intrathecally delivered. The plasmid containing GFP or saline was used as the negative control. To limit the expression of exogenous DNA to neurons of DRGs, a neuron-specific promoter was included in the plasmid. Following a plasmid injection, hMOR-T or hMOR receptors were expressed in small and medium DRG neurons. Compared with saline or GFP rats, the analgesic potency of morphine was increased to a similar extent in hMOR-T and hMOR rats. Morphine induced minimum IK desensitization in both rat groups. In contrast, DAMGO increased analgesic potency and elicited IK desensitization to a significantly less extent in hMOR-T than in hMOR rats. The development and extent of acute and chronic tolerance induced by repeated morphine or DAMGO applications were not altered by the T394A mutation. Conclusions These results indicate that phosphorylation of T394 plays a critical role in determining the potency of DAMGO-induced analgesia and IK desensitization, but has limited effect on morphine-induced responses. On the other hand, the mutation contributes minimally to both DAMGO- and morphine-induced behavioral tolerance. Furthermore, the study shows that plasmid gene delivery of mutant receptors to DRG neurons is a useful strategy to explore nociceptive behavioral consequences of the mutation.
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Affiliation(s)
- Guangwen Li
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1069, USA.
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Abstract
Ligand bias refers to the ability of a drug at a receptor to activate selectively particular cell signalling pathways over others, in a way that cannot be explained by traditional models of receptor theory. For a physiologically and therapeutically important GPCR (G-protein-coupled receptor) such as the MOPr (μ-opioid receptor), the role of ligand bias is currently being explored, not only in order to understand the molecular function of this receptor, but also with a view to developing better analgesic drugs with fewer adverse effects. In this short review, the ways to detect and quantify agonist bias at MOPr are discussed, along with the possible significance of MOPr ligand bias in the therapeutic use of opioid drugs. An important conclusion of this work is that attempts to define ligand bias at any GPCR on the basis of the visual inspection of concentration-response curves or comparison of maximum response (Emax) values can be misleading. Instead, reliable estimations of relative agonist efficacy are needed to calculate bias effectively.
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Llorente J, Withey S, Rivero G, Cunningham M, Cooke A, Saxena K, McPherson J, Oldfield S, Dewey WL, Bailey CP, Kelly E, Henderson G. Ethanol reversal of cellular tolerance to morphine in rat locus coeruleus neurons. Mol Pharmacol 2013; 84:252-60. [PMID: 23716621 DOI: 10.1124/mol.113.085936] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Consumption of ethanol is a considerable risk factor for death in heroin overdose. We sought to determine whether a mildly intoxicating concentration of ethanol could alter morphine tolerance at the cellular level. In rat locus coeruleus (LC) neurons, tolerance to morphine was reversed by acute exposure of the brain slice to ethanol (20 mM). Tolerance to the opioid peptide [d-Ala(2),N-MePhe(4),Gly-ol]-enkephalin was not reversed by ethanol. Previous studies in LC neurons have revealed a role for protein kinase C (PKC)α in μ-opioid receptor (MOPr) desensitization by morphine and in the induction and maintenance of morphine tolerance, but we have been unable to demonstrate that 20 mM ethanol produces significant inhibition of PKCα. The ability of ethanol to reverse cellular tolerance to morphine in LC neurons was absent in the presence of the phosphatase inhibitor okadaic acid, indicating that dephosphorylation is involved. In human embryonic kidney 293 cells expressing the MOPr, ethanol reduced the level of MOPr phosphorylation induced by morphine. Ethanol reversal of tolerance did not appear to result from a direct effect on MOPr since acute exposure to ethanol (20 mM) did not modify the affinity of binding of morphine to the MOPr or the efficacy of morphine for G-protein activation as measured by guanosine 5'-O-(3-[(35)S]thio)triphosphate binding. Similarly, ethanol did not affect MOPr trafficking. We conclude that acute exposure to ethanol enhances the effects of morphine by reversing the processes underlying morphine cellular tolerance.
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Affiliation(s)
- Javier Llorente
- School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
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