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Dimerization of β 2-adrenergic receptor is responsible for the constitutive activity subjected to inverse agonism. Cell Chem Biol 2022; 29:1532-1540.e5. [PMID: 36167077 DOI: 10.1016/j.chembiol.2022.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 07/07/2022] [Accepted: 09/06/2022] [Indexed: 11/22/2022]
Abstract
Dimerization of beta 2-adrenergic receptor (β2-AR) has been observed across various physiologies. However, the function of dimeric β2-AR is still elusive. Here, we revealed that dimerization of β2-AR is responsible for the constitutive activity of β2-AR generating inverse agonism. Using a co-immunoimmobilization assay, we found that transient β2-AR dimers exist in a resting state, and the dimer was disrupted by the inverse agonists. A Gαs preferentially interacts with dimeric β2-AR, but not monomeric β2-AR, in a resting state, resulting in the production of a resting cAMP level. The formation of β2-AR dimers requires cholesterol on the plasma membrane. The cholesterol did not interfere with the agonist-induced activation of monomeric β2-AR, unlike the inverse agonists, implying that the cholesterol is a specific factor regulating the dimerization of β2-AR. Our model not only shows the function of dimeric β2-AR but also provides a molecular insight into the mechanism of the inverse agonism of β2-AR.
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Kremer M, Megat S, Bohren Y, Wurtz X, Nexon L, Ceredig RA, Doridot S, Massotte D, Salvat E, Yalcin I, Barrot M. Delta opioid receptors are essential to the antiallodynic action of Β 2-mimetics in a model of neuropathic pain. Mol Pain 2020; 16:1744806920912931. [PMID: 32208806 PMCID: PMC7097867 DOI: 10.1177/1744806920912931] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The adrenergic system, because of its reported implication in pain mechanisms, may be a potential target for chronic pain treatment. We previously demonstrated that β2-adrenoceptors (β2-ARs) are essential for neuropathic pain treatment by antidepressant drugs, and we showed that agonists of β2-ARs, that is, β2-mimetics, had an antiallodynic effect per se following chronic administration. To further explore the downstream mechanism of this action, we studied here the role of the opioid system. We used behavioral, genetic, and pharmacological approaches to test whether opioid receptors were necessary for the antiallodynic action of a short acting (terbutaline) and a long-acting (formoterol) β2-mimetic. Using the Cuff model of neuropathic pain in mice, we showed that chronic treatments with terbutaline (intraperitoneal) or formoterol (orally) alleviated mechanical hypersensitivity. We observed that these β2-mimetics remained fully effective in μ-opioid and in κ-opioid receptor deficient mice, but lost their antiallodynic action in δ-opioid receptor deficient mice, either female or male. Accordingly, we showed that the δ-opioid receptor antagonist naltrindole induced an acute relapse of allodynia in mice with neuropathic pain chronically treated with the β2-mimetics. Such relapse was also observed following administration of the peripheral opioid receptor antagonist naloxone methiodide. These data demonstrate that the antiallodynic effect of long-term β2-mimetics in a context of neuropathic pain requires the endogenous opioid system, and more specifically peripheral δ-opioid receptors.
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Affiliation(s)
- Mélanie Kremer
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
| | - Salim Megat
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
| | - Yohann Bohren
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
| | - Xavier Wurtz
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
| | - Laurent Nexon
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
| | - Rhian Alice Ceredig
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
| | - Stéphane Doridot
- Centre National de la Recherche Scientifique, Université de Strasbourg, Chronobiotron, Strasbourg, France
| | - Dominique Massotte
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
| | - Eric Salvat
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France.,Hôpitaux Universitaires de Strasbourg, Centre d'Evaluation et de Traitement de la Douleur, Strasbourg, France
| | - Ipek Yalcin
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
| | - Michel Barrot
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
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Jaykumar AB, Caceres PS, Ortiz PA. Single-molecule labeling for studying trafficking of renal transporters. Am J Physiol Renal Physiol 2018; 315:F1243-F1249. [PMID: 30043625 DOI: 10.1152/ajprenal.00082.2017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ability to detect and track single molecules presents the advantage of visualizing the complex behavior of transmembrane proteins with a time and space resolution that would otherwise be lost with traditional labeling and biochemical techniques. Development of new imaging probes has provided a robust method to study their trafficking and surface dynamics. This mini-review focuses on the current technology available for single-molecule labeling of transmembrane proteins, their advantages, and limitations. We also discuss the application of these techniques to the study of renal transporter trafficking in light of recent research.
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Affiliation(s)
- Ankita Bachhawat Jaykumar
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan.,Department of Physiology, Wayne State University School of Medicine , Detroit, Michigan
| | - Paulo S Caceres
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan
| | - Pablo A Ortiz
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital , Detroit, Michigan.,Department of Physiology, Wayne State University School of Medicine , Detroit, Michigan
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4
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Gendron L, Cahill CM, von Zastrow M, Schiller PW, Pineyro G. Molecular Pharmacology of δ-Opioid Receptors. Pharmacol Rev 2017; 68:631-700. [PMID: 27343248 DOI: 10.1124/pr.114.008979] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Opioids are among the most effective analgesics available and are the first choice in the treatment of acute severe pain. However, partial efficacy, a tendency to produce tolerance, and a host of ill-tolerated side effects make clinically available opioids less effective in the management of chronic pain syndromes. Given that most therapeutic opioids produce their actions via µ-opioid receptors (MOPrs), other targets are constantly being explored, among which δ-opioid receptors (DOPrs) are being increasingly considered as promising alternatives. This review addresses DOPrs from the perspective of cellular and molecular determinants of their pharmacological diversity. Thus, DOPr ligands are examined in terms of structural and functional variety, DOPrs' capacity to engage a multiplicity of canonical and noncanonical G protein-dependent responses is surveyed, and evidence supporting ligand-specific signaling and regulation is analyzed. Pharmacological DOPr subtypes are examined in light of the ability of DOPr to organize into multimeric arrays and to adopt multiple active conformations as well as differences in ligand kinetics. Current knowledge on DOPr targeting to the membrane is examined as a means of understanding how these receptors are especially active in chronic pain management. Insight into cellular and molecular mechanisms of pharmacological diversity should guide the rational design of more effective, longer-lasting, and better-tolerated opioid analgesics for chronic pain management.
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Affiliation(s)
- Louis Gendron
- Département de Pharmacologie-Physiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Centre de Recherche du CHU de Sherbrooke, Centre d'excellence en neurosciences de l'Univeristé de Sherbrooke, and Institut de Pharmacologie de Sherbrooke, Sherbrooke, Quebec, Canada (L.G.); Québec Pain Research Network, Sherbrooke, Quebec, Canada (L.G.); Departments of Anesthesiology and Perioperative Care and Pharmacology, University of California, Irvine, California (C.M.C.); Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada (C.M.C.); Departments of Psychiatry and Cellular and Molecular Pharmacology, University of California, San Francisco, California (M.v.Z.); Laboratory of Chemical Biology and Peptide Research, Clinical Research Institute of Montréal, Montreal, Quebec, Canada (P.W.S.); and Departments of Psychiatry, Pharmacology, and Neurosciences, Faculty of Medicine, University of Montréal and Sainte-Justine Hospital Research Center, Montreal, Quebec, Canada (G.P.)
| | - Catherine M Cahill
- Département de Pharmacologie-Physiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Centre de Recherche du CHU de Sherbrooke, Centre d'excellence en neurosciences de l'Univeristé de Sherbrooke, and Institut de Pharmacologie de Sherbrooke, Sherbrooke, Quebec, Canada (L.G.); Québec Pain Research Network, Sherbrooke, Quebec, Canada (L.G.); Departments of Anesthesiology and Perioperative Care and Pharmacology, University of California, Irvine, California (C.M.C.); Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada (C.M.C.); Departments of Psychiatry and Cellular and Molecular Pharmacology, University of California, San Francisco, California (M.v.Z.); Laboratory of Chemical Biology and Peptide Research, Clinical Research Institute of Montréal, Montreal, Quebec, Canada (P.W.S.); and Departments of Psychiatry, Pharmacology, and Neurosciences, Faculty of Medicine, University of Montréal and Sainte-Justine Hospital Research Center, Montreal, Quebec, Canada (G.P.)
| | - Mark von Zastrow
- Département de Pharmacologie-Physiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Centre de Recherche du CHU de Sherbrooke, Centre d'excellence en neurosciences de l'Univeristé de Sherbrooke, and Institut de Pharmacologie de Sherbrooke, Sherbrooke, Quebec, Canada (L.G.); Québec Pain Research Network, Sherbrooke, Quebec, Canada (L.G.); Departments of Anesthesiology and Perioperative Care and Pharmacology, University of California, Irvine, California (C.M.C.); Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada (C.M.C.); Departments of Psychiatry and Cellular and Molecular Pharmacology, University of California, San Francisco, California (M.v.Z.); Laboratory of Chemical Biology and Peptide Research, Clinical Research Institute of Montréal, Montreal, Quebec, Canada (P.W.S.); and Departments of Psychiatry, Pharmacology, and Neurosciences, Faculty of Medicine, University of Montréal and Sainte-Justine Hospital Research Center, Montreal, Quebec, Canada (G.P.)
| | - Peter W Schiller
- Département de Pharmacologie-Physiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Centre de Recherche du CHU de Sherbrooke, Centre d'excellence en neurosciences de l'Univeristé de Sherbrooke, and Institut de Pharmacologie de Sherbrooke, Sherbrooke, Quebec, Canada (L.G.); Québec Pain Research Network, Sherbrooke, Quebec, Canada (L.G.); Departments of Anesthesiology and Perioperative Care and Pharmacology, University of California, Irvine, California (C.M.C.); Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada (C.M.C.); Departments of Psychiatry and Cellular and Molecular Pharmacology, University of California, San Francisco, California (M.v.Z.); Laboratory of Chemical Biology and Peptide Research, Clinical Research Institute of Montréal, Montreal, Quebec, Canada (P.W.S.); and Departments of Psychiatry, Pharmacology, and Neurosciences, Faculty of Medicine, University of Montréal and Sainte-Justine Hospital Research Center, Montreal, Quebec, Canada (G.P.)
| | - Graciela Pineyro
- Département de Pharmacologie-Physiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Centre de Recherche du CHU de Sherbrooke, Centre d'excellence en neurosciences de l'Univeristé de Sherbrooke, and Institut de Pharmacologie de Sherbrooke, Sherbrooke, Quebec, Canada (L.G.); Québec Pain Research Network, Sherbrooke, Quebec, Canada (L.G.); Departments of Anesthesiology and Perioperative Care and Pharmacology, University of California, Irvine, California (C.M.C.); Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada (C.M.C.); Departments of Psychiatry and Cellular and Molecular Pharmacology, University of California, San Francisco, California (M.v.Z.); Laboratory of Chemical Biology and Peptide Research, Clinical Research Institute of Montréal, Montreal, Quebec, Canada (P.W.S.); and Departments of Psychiatry, Pharmacology, and Neurosciences, Faculty of Medicine, University of Montréal and Sainte-Justine Hospital Research Center, Montreal, Quebec, Canada (G.P.)
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5
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Varandas KC, Irannejad R, von Zastrow M. Retromer Endosome Exit Domains Serve Multiple Trafficking Destinations and Regulate Local G Protein Activation by GPCRs. Curr Biol 2016; 26:3129-3142. [PMID: 27839977 DOI: 10.1016/j.cub.2016.09.052] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 09/08/2016] [Accepted: 09/26/2016] [Indexed: 02/01/2023]
Abstract
Retromer mediates sequence-directed cargo exit from endosomes to support both endosome-to-Golgi (retrograde transport) and endosome-to-plasma membrane (recycling) itineraries. It is not known whether these trafficking functions require cargos to exit endosomes separately via distinct transport intermediates or whether the same retromer-coated carriers can support both itineraries. We addressed this question by comparing human Wntless (Wls) and β2 adrenergic receptor (β2AR), which require retromer physiologically for retrograde transport and recycling, respectively. We show here by direct visualization in living cells that both cargos transit primarily the same endosomes and exit via shared transport vesicles generated from a retromer-coated endosome domain. While both Wls and β2AR clearly localize to the same retromer-coated endosome domains, Wls is consistently enriched more strongly. This enrichment difference is determined by distinct motifs present in the cytoplasmic tail of each cargo, with Wls using tandem Φ-X-[L/M] motifs and β2AR using a PDZ motif. Exchanging these determinants reverses the enrichment phenotype of each cargo but does not change cargo itinerary, verifying the multifunctional nature of retromer and implying that additional sorting must occur downstream. Quantitative differences in the degree of cargo enrichment instead underlie a form of kinetic sorting that impacts the rate of cargo delivery via both itineraries and determines the ability of β2AR to activate its cognate G protein transducer locally from endosomes. We propose that mammalian retromer forms a multifunctional membrane coat that supports shared cargo exit for divergent trafficking itineraries and regulates signaling from endosomes.
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Affiliation(s)
- Katherine C Varandas
- Program in Cell Biology, University of California, San Francisco, 16(th) Street, San Francisco, CA 94158, USA
| | - Roshanak Irannejad
- Department of Psychiatry, UCSF School of Medicine, 16(th) Street, San Francisco, CA 94158, USA
| | - Mark von Zastrow
- Program in Cell Biology, University of California, San Francisco, 16(th) Street, San Francisco, CA 94158, USA; Department of Psychiatry, UCSF School of Medicine, 16(th) Street, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, 16(th) Street, San Francisco, CA 94158, USA.
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6
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Latty SL, Felce JH, Weimann L, Lee SF, Davis SJ, Klenerman D. Referenced Single-Molecule Measurements Differentiate between GPCR Oligomerization States. Biophys J 2016; 109:1798-806. [PMID: 26536257 PMCID: PMC4643199 DOI: 10.1016/j.bpj.2015.09.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 08/25/2015] [Accepted: 09/08/2015] [Indexed: 11/24/2022] Open
Abstract
The extent to which Rhodopsin family G-protein-coupled receptors (GPCRs) form invariant oligomers is contentious. Recent single-molecule fluorescence imaging studies mostly argue against the existence of constitutive receptor dimers and instead suggest that GPCRs only dimerize transiently, if at all. However, whether or not even transient dimers exist is not always clear due to difficulties in unambiguously distinguishing genuine interactions from chance colocalizations, particularly with respect to short-lived events. Previous single-molecule studies have depended critically on calculations of chance colocalization rates and/or comparison with unfixed control proteins whose diffusional behavior may or may not differ from that of the test receptor. Here, we describe a single-molecule imaging assay that 1) utilizes comparisons with well-characterized control proteins, i.e., the monomer CD86 and the homodimer CD28, and 2) relies on cell fixation to limit artifacts arising from differences in the distribution and diffusion of test proteins versus these controls. The improved assay reliably reports the stoichiometry of the Glutamate-family GPCR dimer, γ-amino butyric acid receptor b2, whereas two Rhodopsin-family GPCRs, β2-adrenergic receptor and mCannR2, exhibit colocalization levels comparable to those of CD86 monomers, strengthening the case against invariant GPCR oligomerization.
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Affiliation(s)
- Sarah L Latty
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - James H Felce
- Radcliffe Department of Clinical Medicine and Medical Research Council Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Laura Weimann
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Steven F Lee
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Simon J Davis
- Radcliffe Department of Clinical Medicine and Medical Research Council Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom.
| | - David Klenerman
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
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7
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Choucair-Jaafar N, Salvat E, Freund-Mercier MJ, Barrot M. The antiallodynic action of nortriptyline and terbutaline is mediated by β2 adrenoceptors and δ opioid receptors in the ob/ob model of diabetic polyneuropathy. Brain Res 2014; 1546:18-26. [DOI: 10.1016/j.brainres.2013.12.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 12/03/2013] [Accepted: 12/12/2013] [Indexed: 12/15/2022]
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8
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Single-molecule imaging revealed dynamic GPCR dimerization. Curr Opin Cell Biol 2013; 27:78-86. [PMID: 24480089 DOI: 10.1016/j.ceb.2013.11.008] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 11/24/2013] [Indexed: 11/24/2022]
Abstract
Single fluorescent-molecule video imaging and tracking in living cells are revolutionizing our understanding of molecular interactions in the plasma membrane and intracellular membrane systems. They have revealed that molecular interactions occur surprisingly dynamically on much shorter time scales (≪1s) than those expected from the results by conventional techniques, such as pull-down assays (minutes to hours). Single-molecule imaging has unequivocally showed that G-protein-coupled receptors (GPCRs) undergo dynamic equilibrium between monomers and dimers, by enabling the determination of the 2D monomer-dimer equilibrium constant, the dimer dissociation rate constant (typically ∼10s(-1)), and the formation rate constant. Within one second, GPCRs typically undergo several cycles of monomer and homo-dimer formation with different partners.
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9
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Yekkirala AS. Two to tango: GPCR oligomers and GPCR-TRP channel interactions in nociception. Life Sci 2013; 92:438-45. [DOI: 10.1016/j.lfs.2012.06.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 06/15/2012] [Accepted: 06/22/2012] [Indexed: 11/16/2022]
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10
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Single-molecule analysis of fluorescently labeled G-protein-coupled receptors reveals complexes with distinct dynamics and organization. Proc Natl Acad Sci U S A 2012; 110:743-8. [PMID: 23267088 DOI: 10.1073/pnas.1205798110] [Citation(s) in RCA: 329] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) constitute the largest family of receptors and major pharmacological targets. Whereas many GPCRs have been shown to form di-/oligomers, the size and stability of such complexes under physiological conditions are largely unknown. Here, we used direct receptor labeling with SNAP-tags and total internal reflection fluorescence microscopy to dynamically monitor single receptors on intact cells and thus compare the spatial arrangement, mobility, and supramolecular organization of three prototypical GPCRs: the β(1)-adrenergic receptor (β(1)AR), the β(2)-adrenergic receptor (β(2)AR), and the γ-aminobutyric acid (GABA(B)) receptor. These GPCRs showed very different degrees of di-/oligomerization, lowest for β(1)ARs (monomers/dimers) and highest for GABA(B) receptors (prevalently dimers/tetramers of heterodimers). The size of receptor complexes increased with receptor density as a result of transient receptor-receptor interactions. Whereas β(1)-/β(2)ARs were apparently freely diffusing on the cell surface, GABA(B) receptors were prevalently organized into ordered arrays, via interaction with the actin cytoskeleton. Agonist stimulation did not alter receptor di-/oligomerization, but increased the mobility of GABA(B) receptor complexes. These data provide a spatiotemporal characterization of β(1)-/β(2)ARs and GABA(B) receptors at single-molecule resolution. The results suggest that GPCRs are present on the cell surface in a dynamic equilibrium, with constant formation and dissociation of new receptor complexes that can be targeted, in a ligand-regulated manner, to different cell-surface microdomains.
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von Zastrow M, Williams JT. Modulating neuromodulation by receptor membrane traffic in the endocytic pathway. Neuron 2012; 76:22-32. [PMID: 23040804 DOI: 10.1016/j.neuron.2012.09.022] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cellular responsiveness to many neuromodulators is controlled by endocytosis of the transmembrane receptors that transduce their effects. Endocytic membrane trafficking of particular neuromodulator receptors exhibits remarkable diversity and specificity, determined largely by molecular sorting operations that guide receptors at trafficking branchpoints after endocytosis. In this Review, we discuss recent progress in elucidating mechanisms mediating the molecular sorting of neuromodulator receptors in the endocytic pathway. There is emerging evidence that endocytic trafficking of neuromodulator receptors, in addition to influencing longer-term cellular responsiveness under conditions of prolonged or repeated activation, may also affect the acute response. Physiological and pathological consequences of defined receptor trafficking events are only now being elucidated, but it is already apparent that endocytosis of neuromodulator receptors has a significant impact on the actions of therapeutic drugs. The present data also suggest, conversely, that mechanisms of receptor endocytosis and molecular sorting may themselves represent promising targets for therapeutic manipulation.
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Affiliation(s)
- Mark von Zastrow
- Department of Psychiatry, University of California at San Francisco, San Francisco, CA 94158, USA.
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12
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Cotecchia S, Stanasila L, Diviani D. Protein-protein interactions at the adrenergic receptors. Curr Drug Targets 2012; 13:15-27. [PMID: 21777184 PMCID: PMC3290771 DOI: 10.2174/138945012798868489] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 02/12/2011] [Accepted: 02/16/2011] [Indexed: 01/07/2023]
Abstract
The adrenergic receptors are among the best characterized G protein-coupled receptors (GPCRs) and knowledge on this receptor family has provided several important paradigms about GPCR function and regulation. One of the most recent paradigms initially supported by studies on adrenergic receptors is that both βarrestins and G protein-coupled receptors themselves can act as scaffolds binding a variety of proteins and this can result in growing complexity of the receptor-mediated cellular effects. In this review we will briefly summarize the main features of βarrestin binding to the adrenergic receptor subtypes and we will review more in detail the main proteins found to selectively interact with distinct AR subtype. At the end, we will review the main findings on oligomerization of the AR subtypes.
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Affiliation(s)
- Susanna Cotecchia
- Départment de Pharmacologie et de Toxicologie, Université de Lausanne, Switzerland.
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13
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Somvanshi RK, Chaudhari N, Qiu X, Kumar U. Heterodimerization of β2 adrenergic receptor and somatostatin receptor 5: Implications in modulation of signaling pathway. J Mol Signal 2011; 6:9. [PMID: 21838893 PMCID: PMC3166894 DOI: 10.1186/1750-2187-6-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 08/12/2011] [Indexed: 12/17/2022] Open
Abstract
Background In the present study, we describe heterodimerization between human-Somatostatin Receptor 5 (hSSTR5) and β2-Adrenergic Receptor (β2AR) and its impact on the receptor trafficking, coupling to adenylyl cyclase and signaling including mitogen activated protein kinases and calcineurin-NFAT pathways. Methods We used co-immunoprecipitation, photobleaching- fluorescence resonance energy transfer and Fluorescence assisted cell sorting analysis to characterize heterodimerization between SSTR5 and β2AR. Results Our results indicate that hSSTR5/β2AR exist as preformed heterodimers in the basal condition which is enhanced upon co-activation of both receptors. In contrast, the activation of individual receptors leads to the dissociation of heterodimers. Receptor coupling to adenylyl cyclase displayed predominant effect of β2AR, however, somatostatin mediated inhibition of cAMP was enhanced upon blocking β2AR. Our results indicate hSSTR5 mediated significant activation of ERK1/2 and inhibition of phospho-p38. The phospho-NFAT level was enhanced in cotransfected cells indicating the blockade of calcineurin mediated dephosphorylation of NFAT upon receptor heterodimerization. Conclusion These data for the first time unveil a novel insight for the role of hSSTR5/β2AR in the modulation of signaling pathways which has not been addressed earlier.
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Affiliation(s)
- Rishi K Somvanshi
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, BC, Canada.
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14
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Kasai RS, Suzuki KGN, Prossnitz ER, Koyama-Honda I, Nakada C, Fujiwara TK, Kusumi A. Full characterization of GPCR monomer-dimer dynamic equilibrium by single molecule imaging. ACTA ACUST UNITED AC 2011; 192:463-80. [PMID: 21300851 PMCID: PMC3101103 DOI: 10.1083/jcb.201009128] [Citation(s) in RCA: 256] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Receptor dimerization is important for many signaling pathways. However, the monomer-dimer equilibrium has never been fully characterized for any receptor with a 2D equilibrium constant as well as association/dissociation rate constants (termed super-quantification). Here, we determined the dynamic equilibrium for the N-formyl peptide receptor (FPR), a chemoattractant G protein-coupled receptor (GPCR), in live cells at 37°C by developing a single fluorescent-molecule imaging method. Both before and after liganding, the dimer-monomer 2D equilibrium is unchanged, giving an equilibrium constant of 3.6 copies/µm(2), with a dissociation and 2D association rate constant of 11.0 s(-1) and 3.1 copies/µm(2)s(-1), respectively. At physiological expression levels of ∼2.1 receptor copies/µm(2) (∼6,000 copies/cell), monomers continually convert into dimers every 150 ms, dimers dissociate into monomers in 91 ms, and at any moment, 2,500 and 3,500 receptor molecules participate in transient dimers and monomers, respectively. Not only do FPR dimers fall apart rapidly, but FPR monomers also convert into dimers very quickly.
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Affiliation(s)
- Rinshi S Kasai
- Membrane Mechanisms Project, International Cooperative Research Project, Kyoto University, Shougoin, Kyoto 606-8507, Japan
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15
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Lan TH, Kuravi S, Lambert NA. Internalization dissociates β2-adrenergic receptors. PLoS One 2011; 6:e17361. [PMID: 21364942 PMCID: PMC3043075 DOI: 10.1371/journal.pone.0017361] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 01/30/2011] [Indexed: 11/19/2022] Open
Abstract
G protein-coupled receptors (GPCRs) self-associate as dimers or higher-order oligomers in living cells. The stability of associated GPCRs has not been extensively studied, but it is generally thought that these receptors move between the plasma membrane and intracellular compartments as intact dimers or oligomers. Here we show that β(2)-adrenergic receptors (β(2)ARs) that self-associate at the plasma membrane can dissociate during agonist-induced internalization. We use bioluminescence-resonance energy transfer (BRET) to monitor movement of β(2)ARs between subcellular compartments. BRET between β(2)ARs and plasma membrane markers decreases in response to agonist activation, while at the same time BRET between β(2)ARs and endosome markers increases. Energy transfer between β(2)ARs is decreased in a similar manner if either the donor- or acceptor-labeled receptor is mutated to impair agonist binding and internalization. These changes take place over the course of 30 minutes, persist after agonist is removed, and are sensitive to several inhibitors of arrestin- and clathrin-mediated endocytosis. The magnitude of the decrease in BRET between donor- and acceptor-labeled β(2)ARs suggests that at least half of the receptors that contribute to the BRET signal are physically segregated by internalization. These results are consistent with the possibility that β(2)ARs associate transiently with each other in the plasma membrane, or that β(2)AR dimers or oligomers are actively disrupted during internalization.
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Affiliation(s)
- Tien-Hung Lan
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia, United States of America
| | - Sudhakiranmayi Kuravi
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia, United States of America
| | - Nevin A. Lambert
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia, United States of America
- * E-mail:
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16
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Re M, Pampillo M, Savard M, Dubuc C, McArdle CA, Millar RP, Conn PM, Gobeil F, Bhattacharya M, Babwah AV. The human gonadotropin releasing hormone type I receptor is a functional intracellular GPCR expressed on the nuclear membrane. PLoS One 2010; 5:e11489. [PMID: 20628612 PMCID: PMC2900216 DOI: 10.1371/journal.pone.0011489] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 06/11/2010] [Indexed: 12/02/2022] Open
Abstract
The mammalian type I gonadotropin releasing hormone receptor (GnRH-R) is a structurally unique G protein-coupled receptor (GPCR) that lacks cytoplasmic tail sequences and displays inefficient plasma membrane expression (PME). Compared to its murine counterparts, the primate type I receptor is inefficiently folded and retained in the endoplasmic reticulum (ER) leading to a further reduction in PME. The decrease in PME and concomitant increase in intracellular localization of the mammalian GnRH-RI led us to characterize the spatial distribution of the human and mouse GnRH receptors in two human cell lines, HEK 293 and HTR-8/SVneo. In both human cell lines we found the receptors were expressed in the cytoplasm and were associated with the ER and nuclear membrane. A molecular analysis of the receptor protein sequence led us to identify a putative monopartite nuclear localization sequence (NLS) in the first intracellular loop of GnRH-RI. Surprisingly, however, neither the deletion of the NLS nor the addition of the Xenopus GnRH-R cytoplasmic tail sequences to the human receptor altered its spatial distribution. Finally, we demonstrate that GnRH treatment of nuclei isolated from HEK 293 cells expressing exogenous GnRH-RI triggers a significant increase in the acetylation and phosphorylation of histone H3, thereby revealing that the nuclear-localized receptor is functional. Based on our findings, we conclude that the mammalian GnRH-RI is an intracellular GPCR that is expressed on the nuclear membrane. This major and novel discovery causes us to reassess the signaling potential of this physiologically and clinically important receptor.
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Affiliation(s)
- Michelle Re
- The Children's Health Research Institute, London, Canada
- Lawson Health Research Institute, London, Canada
- Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Canada
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Canada
| | - Macarena Pampillo
- The Children's Health Research Institute, London, Canada
- Lawson Health Research Institute, London, Canada
- Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Canada
| | - Martin Savard
- Department of Pharmacology, Université de Sherbrooke, Sherbrooke, Canada
| | - Céléna Dubuc
- Department of Pharmacology, Université de Sherbrooke, Sherbrooke, Canada
| | - Craig A. McArdle
- Laboratories for Integrated Neuroscience and Endocrinology, Department of Clinical Sciences at South Bristol, University of Bristol, Bristol, United Kingdom
| | - Robert P. Millar
- MRC Human Reproductive Sciences Unit, The Queen's Medical Research Institute, Edinburgh, United Kingdom
| | - P. Michael Conn
- Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, Oregon, United States of America
| | - Fernand Gobeil
- Department of Pharmacology, Université de Sherbrooke, Sherbrooke, Canada
| | - Moshmi Bhattacharya
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Canada
| | - Andy V. Babwah
- The Children's Health Research Institute, London, Canada
- Lawson Health Research Institute, London, Canada
- Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Canada
- Department of Physiology and Pharmacology, The University of Western Ontario, London, Canada
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17
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Milligan G. A day in the life of a G protein-coupled receptor: the contribution to function of G protein-coupled receptor dimerization. Br J Pharmacol 2008; 153 Suppl 1:S216-29. [PMID: 17965750 PMCID: PMC2268067 DOI: 10.1038/sj.bjp.0707490] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Revised: 08/21/2007] [Accepted: 09/06/2007] [Indexed: 02/07/2023] Open
Abstract
G protein-coupled receptors are one of the most actively studied families of proteins. However, despite the ubiquity of protein dimerization and oligomerization as a structural and functional motif in biology, until the last decade they were generally considered as monomeric, non-interacting polypeptides. For the metabotropic glutamate-like group of G protein-coupled receptors, it is now firmly established that they exist and function as dimers or, potentially, even within higher-order structures. Despite some evidence continuing to support the view that rhodopsin-like G protein-coupled receptors are predominantly monomers, many recent studies are consistent with the dimerization/oligomerization of such receptors. Key roles suggested for dimerization of G protein-coupled receptors include control of protein maturation and cell surface delivery and providing the correct framework for interactions with both hetero-trimeric G proteins and arrestins to allow signal generation and its termination. As G protein-coupled receptors are the most targeted group of proteins for the development of therapeutic small molecule medicines, recent indications that hetero-dimerization between co-expressed G protein-coupled receptors may be a common process offers the potential for the development of more selective and tissue restricted medicines. However, many of the key experiments have, so far, been limited to model cell systems. Priorities for the future include the generation of tools and reagents able to identify unequivocally potential G protein-coupled receptor hetero-dimers in native tissues and detailed analyses of the influence of hetero-dimerization on receptor function and pharmacology.
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Affiliation(s)
- G Milligan
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, Scotland, UK.
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18
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Dimerization of the thyrotropin-releasing hormone receptor potentiates hormone-dependent receptor phosphorylation. Proc Natl Acad Sci U S A 2007; 104:18303-8. [PMID: 17989235 DOI: 10.1073/pnas.0702857104] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The G protein-coupled thyrotropin (TSH)-releasing hormone (TRH) receptor forms homodimers. Regulated receptor dimerization increases TRH-induced receptor endocytosis. These studies test whether dimerization increases receptor phosphorylation, which could potentiate internalization. Phosphorylation at residues 355-365, which is critical for internalization, was measured with a highly selective phospho-site-specific antibody. Two strategies were used to drive receptor dimerization. Dimerization of a TRH receptor-FK506-binding protein (FKBP) fusion protein was stimulated by a dimeric FKBP ligand. The chemical dimerizer caused a large increase in TRH-dependent phosphorylation within 1 min, whereas a monomeric FKBP ligand had no effect. The dimerizer did not alter phoshorylation of receptors lacking the FKBP domain. Dimerization of receptors containing an N-terminal HA epitope also was induced with anti-HA antibody. Anti-HA IgG strongly increased TRH-induced phosphorylation, whereas monomeric Fab fragments had no effect. Anti-HA antibody did not alter phosphorylation in receptors lacking an HA tag. Furthermore, two phosphorylation-defective TRH receptors functionally complemented one another and permitted phosphorylation. Receptors with a D71A mutation in the second transmembrane domain do not signal, whereas receptors with four Ala mutations in the 355-365 region signal normally but lack phosphorylation sites. When D71A- and 4Ala-TRH receptors were expressed alone, neither underwent TRH-dependent phosphorylation. When they were expressed together, D71A receptor was phosphorylated by G protein-coupled receptor kinases in response to TRH. These results suggest that the TRH receptor is phosphorylated preferentially when it is in dimers or when preexisting receptor dimers are driven into microaggregates. Increased receptor phosphorylation may amplify desensitization.
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19
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Delhaye M, Gravot A, Ayinde D, Niedergang F, Alizon M, Brelot A. Identification of a postendocytic sorting sequence in CCR5. Mol Pharmacol 2007; 72:1497-507. [PMID: 17855654 DOI: 10.1124/mol.107.038422] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The chemokine receptor 5 (CCR5), a member of the G protein-coupled receptor family (GPCR), is used by human immunodeficiency virus type 1 (HIV-1) with a R5 tropism as an entry receptor in addition to CD4. It is a key target for an antiviral action aiming at inhibiting the HIV-1 entry process. Only few data are available today regarding the mechanism involved in the intracellular trafficking process of CCR5. Understanding how CCR5 cell surface expression is regulated is particularly important with regard to HIV-1 entry inhibition. We set out to investigate whether CCR5 molecular determinants were involved in the postendocytic recycling and degradative pathways. We constructed progressive deletion mutants of the C-terminal domain of CCR5 that we stably expressed in HEK293 cells. All of the deletion mutants were expressed at the cell surface and were functional HIV-1 receptors. The deletion mutants were internalized after stimulation, but they lost their ability to recycle to the plasma membrane. They were rerouted toward a lysosomal degradative pathway. We identified here a sequence of four amino acids, present at the extreme C terminus of CCR5, that is necessary for the recycling of the internalized receptor, independently of its phosphorylation. A detailed analysis of this sequence indicated that the four amino acids acted as a postsynaptic density 95/discs-large/zona occludens (PDZ) interacting sequence. These results show that the CCR5 cytoplasmic domain bears a sequence similar to the "recycling signals" previously identified in other GPCRs. Drugs able to disrupt the recycling pathway of CCR5 may constitute promising tools for therapeutic treatment.
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Affiliation(s)
- Maurine Delhaye
- Institut Cochin, Université Paris Descartes, Centre National de la Recherche Scientifique (Unité Mixte de Recherche 8104), Paris, France
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20
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Sartania N, Appelbe S, Pediani JD, Milligan G. Agonist occupancy of a single monomeric element is sufficient to cause internalization of the dimeric beta2-adrenoceptor. Cell Signal 2007; 19:1928-38. [PMID: 17561373 DOI: 10.1016/j.cellsig.2007.05.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Revised: 05/03/2007] [Accepted: 05/09/2007] [Indexed: 11/19/2022]
Abstract
A range of studies have indicated that many rhodopsin-like, family A G protein-coupled receptors, including the beta(2)-adrenoceptor, exist and probably function as dimers. It is less clear if receptors internalize as dimers and if agonist occupancy of only one element of a dimer is sufficient to cause internalization of a receptor dimer into the cell. We have used a chemogenomic approach to demonstrate that this is the case. Following expression of the wild type beta(2)-adrenoceptor, isoprenaline but not 1-(3''4'-dihydroxyphenyl)-3-methyl-1-butanone, which does not have significant affinity for the wild type receptor, caused receptor internalization. By contrast, 1-(3'4'-dihydroxyphenyl)-3-methyl-1-butanone, but not isoprenaline that does not have high affinity for the mutated receptor, caused internalization of Asp(113)Serbeta(2)-adrenoceptor. Following co-expression of wild type and Asp(113)Serbeta(2)-adrenoceptors each of isoprenaline and 1-(3'4'-dihydroxyphenyl)-3-methyl-1-butanone caused the co-internalization of both of these two forms of the receptor. Co-expressed wild type and Asp(113)Serbeta(2)-adrenoceptors were able to be co-immunoprecipitated and 1-(3'4'-dihydroxyphenyl)-3-methyl-1-butanone produced internalization of the wild type receptor that was not prevented by the beta-adrenoceptor antagonist propranolol that binds with high affinity only to the wild type receptor. These results demonstrate that agonist occupancy of either single binding site of the beta(2)-adrenoceptor dimer is sufficient to cause internalization of the dimer and that antagonist occupation of one of the two ligand binding sites is unable to prevent agonist-mediated internalization.
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Affiliation(s)
- Nana Sartania
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
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21
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Milligan G. G protein-coupled receptor dimerisation: Molecular basis and relevance to function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:825-35. [PMID: 17069751 DOI: 10.1016/j.bbamem.2006.09.021] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Revised: 09/25/2006] [Accepted: 09/26/2006] [Indexed: 12/21/2022]
Abstract
The belief that G protein-coupled receptors exist and function as monomeric, non-interacting species has been largely supplanted in recent years by evidence, derived from a range of approaches, that indicate they can form dimers and/or higher-order oligomeric complexes. Key roles for receptor homo-dimerisation include effective quality control of protein folding prior to plasma membrane delivery and interactions with hetero-trimeric G proteins. Growing evidence has also indicated the potential for many co-expressed G protein-coupled receptors to form hetero-dimers/oligomers. The relevance of this to physiology and function is only beginning to be unravelled but may offer great potential for more selective therapeutic intervention.
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Affiliation(s)
- Graeme Milligan
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, Scotland, UK.
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22
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Abstract
This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 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 (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367, USA.
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23
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Milligan G. G-protein-coupled receptor heterodimers: pharmacology, function and relevance to drug discovery. Drug Discov Today 2006; 11:541-9. [PMID: 16713906 DOI: 10.1016/j.drudis.2006.04.007] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Revised: 03/08/2006] [Accepted: 04/04/2006] [Indexed: 11/16/2022]
Abstract
The growing recognition that members of the rhodopsin-like family A G-protein-coupled receptors (GPCRs) exist and function as dimers or higher-order oligomers, and that GPCR hetero-dimers and -oligomers are present in physiological tissues, offers novel opportunities for drug discovery. Differential pharmacology, function and regulation of GPCR hetero-dimers and -oligomers suggest means to selectively target GPCRs in different tissues and hint that the mechanism of function of several pharmacological agents might be different in vivo than anticipated from simple ligand-screening programmes that rely on heterologous expression of a single GPCR.
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Affiliation(s)
- Graeme Milligan
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, Scotland, UK.
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24
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Wilson S, Wilkinson G, Milligan G. The CXCR1 and CXCR2 Receptors Form Constitutive Homo- and Heterodimers Selectively and with Equal Apparent Affinities. J Biol Chem 2005; 280:28663-74. [PMID: 15946947 DOI: 10.1074/jbc.m413475200] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Both homo- and heterodimeric interactions between the CXCR1 and CXCR2 chemokine receptors were observed following co-expression of forms of these receptors in HEK293 cells using assays, including co-immunoprecipitation, single cell imaging of fluorescence resonance energy transfer, cell surface time-resolved fluorescence resonance energy transfer, and bioluminescence resonance energy transfer. These interactions were constitutive and unaffected by the presence of the agonist interleukin 8 and selective as no significant interactions were noted between either the CXCR1 or CXCR2 receptor and the alpha(1A)-adrenoreceptor. Saturation bioluminescence resonance energy transfer indicated that heteromeric interactions between CXCR1 and CXCR2 were of similar affinity as the corresponding homomeric interactions. A novel endoplasmic reticulum trapping strategy demonstrated that these interactions were initiated during protein synthesis and maturation and prior to cell surface delivery. These studies indicated that CXCR1-CXCR2 heterodimers are as likely to form in cells co-expressing these two chemokine receptors as the corresponding homodimers and stand in contrast to previous studies indicating an inability of the CXCR1 receptor to homodimerize or to interact with the CXCR2 receptor (Trettel, F., Di Bartolomeo, S., Lauro, C., Catalano, M., Ciotti, M. T., and Limatola, C. (2003) J. Biol. Chem. 278, 40980-40988).
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Affiliation(s)
- Shirley Wilson
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
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