51
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Rondard P, Pin JP. Dynamics and modulation of metabotropic glutamate receptors. Curr Opin Pharmacol 2015; 20:95-101. [DOI: 10.1016/j.coph.2014.12.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 11/29/2014] [Accepted: 12/01/2014] [Indexed: 11/28/2022]
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52
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Opportunities and challenges in the discovery of allosteric modulators of GPCRs for treating CNS disorders. Nat Rev Drug Discov 2014; 13:692-708. [PMID: 25176435 DOI: 10.1038/nrd4308] [Citation(s) in RCA: 203] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Novel allosteric modulators of G protein-coupled receptors (GPCRs) are providing fundamental advances in the development of GPCR ligands with high subtype selectivity and novel modes of efficacy that have not been possible with traditional approaches. As new allosteric modulators are advancing as drug candidates, we are developing an increased understanding of the major advantages and broad range of activities that can be achieved with these agents through selective modulation of specific signalling pathways, differential effects on GPCR homodimers versus heterodimers, and other properties. This understanding creates exciting opportunities, as well as unique challenges, in the optimization of novel therapeutic agents for disorders of the central nervous system.
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53
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Bock A, Kostenis E, Tränkle C, Lohse MJ, Mohr K. Pilot the pulse: controlling the multiplicity of receptor dynamics. Trends Pharmacol Sci 2014; 35:630-8. [PMID: 25455830 DOI: 10.1016/j.tips.2014.10.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 10/07/2014] [Accepted: 10/08/2014] [Indexed: 12/30/2022]
Abstract
G protein-coupled receptors (GPCRs) are involved in almost every (patho)physiological process, which explains their importance as drug targets. GPCRs have long been regarded as on/off-switches, which is reflected by direct activation or blockade of these receptors through the majority of marketed GPCR drugs. In recent years, however, our view of GPCRs has changed dramatically. GPCRs are now appreciated as integrative and highly dynamic signaling machines which can adopt numerous distinct conformations enabling them to initiate a highly ramified signaling network. We argue here that it may be possible to chemically encode distinct signaling profiles into ligands by rational ligand design. We exemplify our hypothesis by fine-tuning partial and biased agonism, thereby exploiting two new principles of GPCR modulation - dynamic and dualsteric ligand binding. We propose that the emerging understanding of the multiplicity of receptor dynamics will eventually lead to rationally designed new drugs which pilot the pulse; in other words, that stabilize distinct receptor states to fine-tune GPCR signaling.
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Affiliation(s)
- Andreas Bock
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany.
| | - Evi Kostenis
- Molecular-, Cellular-, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Christian Tränkle
- Pharmacology and Toxicology Section, Institute of Pharmacy, University of Bonn, Gerhard-Domagk-Strasse 3, 53121 Bonn, Germany
| | - Martin J Lohse
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany; Rudolf Virchow Center, University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
| | - Klaus Mohr
- Pharmacology and Toxicology Section, Institute of Pharmacy, University of Bonn, Gerhard-Domagk-Strasse 3, 53121 Bonn, Germany.
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54
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Techlovská Š, Chambers JN, Dvořáková M, Petralia RS, Wang YX, Hájková A, Nová A, Franková D, Prezeau L, Blahos J. Metabotropic glutamate receptor 1 splice variants mGluR1a and mGluR1b combine in mGluR1a/b dimers in vivo. Neuropharmacology 2014; 86:329-336. [PMID: 25158311 DOI: 10.1016/j.neuropharm.2014.08.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 08/13/2014] [Accepted: 08/14/2014] [Indexed: 02/03/2023]
Abstract
The assembly of two covalently linked monomers into dimeric complexes is a prerequisite for metabotropic glutamate receptor 1 (mGluR1) function. The former concept of a strictly homodimeric subunit contribution in metabotropic glutamate receptor complexes has recently been brought into question. Alternative splicing of the GRM1 gene results in expression of variants that vary within their intracellular C-termini. Here we bring evidence that the short mGluR1b variant is found preferentially in a complex with the long mGluR1a variant in the rodent brain. The mGluR1a and mGluR1b variants distribution overlaps in Purkinje cells and the two variants colocalize in their spines. However mGluR1a and mGluR1b show distinct sub-cellular localization when expressed alone in neurons. We discovered that trafficking of mGluR1b to distal dendrites is reliant on its association with mGluR1a and that the long C-terminus of mGluR1a within the mGluR1a/b dimer is necessary for trafficking of the complex.
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Affiliation(s)
- Šárka Techlovská
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Jayne Nicole Chambers
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Michaela Dvořáková
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Ronald S Petralia
- National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892
| | - Ya-Xian Wang
- National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892
| | - Alena Hájková
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Alice Nová
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Daniela Franková
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Laurent Prezeau
- CNRS UMR5203, Institut de génomique fonctionnelle, Montpellier, France.,INSERM U661, Montpellier, France.,Université Montpellier 1 & 2, Montpellier F-34000, France
| | - Jaroslav Blahos
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
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55
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Sevastyanova TN, Kammermeier PJ. Cooperative signaling between homodimers of metabotropic glutamate receptors 1 and 5. Mol Pharmacol 2014; 86:492-504. [PMID: 25113912 DOI: 10.1124/mol.114.093468] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Metabotropic glutamate receptors (mGluRs) function as dimers. Recent work suggests that mGluR1 and mGluR5 may physically interact, but the nature and functional consequences of this relationship have not been addressed. In this study, the functional and pharmacological consequences of this interaction were investigated. Using heterologous expression of mGluR cDNA in rat sympathetic neurons from the superior cervical ganglion and inhibition of the native calcium currents as an assay for receptor activation, a functional interdependence between mGluR1 and mGluR5 was demonstrated. In neurons coexpressing these receptors, combining a selective mGluR1 competitive antagonist with either an mGluR1- or mGluR5-selective negative allosteric modulator (NAM) BAY36-7620 [(3aS,6aS)-hexahydro-5-methylene-6a-(2-naphthalenylmethyl)-1H-cyclopenta[c]furan-1-one] or MPEP [2-methyl-6-(phenylethynyl)pyridine hydrochloride], respectively, strongly occluded signaling by both receptors to an approximately equal degree. By contrast, in cells coexpressing mGluR1 and mGluR2, combining the same mGluR1 competitive inhibitor with an mGluR1 or mGluR2 NAM yielded partial and full inhibition of the response, respectively, as expected for independently acting receptors. In neurons expressing mGluR1 and mGluR5, the selective NAMs each strongly inhibited the response to glutamate, suggesting that these receptors do not interact as heterodimers, which would not be inhibited by selective NAMs. Finally, evidence for a similar mGluR1/mGluR5 functional dependence is shown in medium spiny striatal neurons. Together, these data demonstrate cooperative signaling between mGluR1 and mGluR5 in a manner inconsistent with heterodimerization, and thus suggest an interaction between homodimers.
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Affiliation(s)
- Tatyana N Sevastyanova
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York
| | - Paul J Kammermeier
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York
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56
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Goupil E, Laporte SA, Hébert TE. A simple method to detect allostery in GPCR dimers. Methods Cell Biol 2014; 117:165-79. [PMID: 24143977 DOI: 10.1016/b978-0-12-408143-7.00009-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
G protein-coupled receptors (GPCRs) represent one of the largest families of cell surface receptors as key targets for pharmacological manipulation. G proteins have long been recognized as allosteric modulators of GPCR ligand binding. More recently, small molecule allosteric modulators have now been widely characterized for a number of GPCRs, and some are now used clinically. Many studies have also underscored the importance of GPCR dimerization or higher-order oligomerization in the control of the physiological responses they modulate. Thus, allosterism can also, between monomer equivalents in the context of a dimer, oligomer, or receptor mosaic, influence signaling pathways downstream. It therefore becomes essential to characterize both small molecule allosteric ligands and allosteric interactions between receptors modulated by canonical orthosteric ligands, in a pathway-specific manner. Here, we describe a simple, radioligand-binding method, which is designed to probe for allosteric modulation mediated by any GPCR interactor, from small molecules to interacting proteins. It can also detect allosteric asymmetries within a GPCR heterodimer, via orthosteric or allosteric ligands. This assay measures time-dependent ligand occupancy of radiolabeled orthosteric or (with adaptations) allosteric ligands as modulated by either small molecules or receptor dimer partners bound or unbound with their own ligands.
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Affiliation(s)
- Eugénie Goupil
- Department of Pharmacology, McGill University, Montréal, Québec, Canada
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57
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Yin S, Niswender CM. Progress toward advanced understanding of metabotropic glutamate receptors: structure, signaling and therapeutic indications. Cell Signal 2014; 26:2284-97. [PMID: 24793301 DOI: 10.1016/j.cellsig.2014.04.022] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 04/27/2014] [Indexed: 12/24/2022]
Abstract
The metabotropic glutamate (mGlu) receptors are a group of Class C seven-transmembrane spanning/G protein-coupled receptors (7TMRs/GPCRs). These receptors are activated by glutamate, one of the standard amino acids and the major excitatory neurotransmitter. By activating G protein-dependent and non-G protein-dependent signaling pathways, mGlus modulate glutamatergic transmission both in the periphery and throughout the central nervous system. Since the discovery of the first mGlu receptor, and especially during the last decade, a great deal of progress has been made in understanding the signaling, structure, pharmacological manipulation and therapeutic indications of the 8 mGlu members.
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Affiliation(s)
- Shen Yin
- Department of Pharmacology, Vanderbilt University Medical School, Nashville, TN 37232, USA; Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical School, Nashville, TN 37232, USA
| | - Colleen M Niswender
- Department of Pharmacology, Vanderbilt University Medical School, Nashville, TN 37232, USA; Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical School, Nashville, TN 37232, USA.
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58
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Jiang X, Fischer D, Chen X, McKenna SD, Liu H, Sriraman V, Yu HN, Goutopoulos A, Arkinstall S, He X. Evidence for Follicle-stimulating Hormone Receptor as a Functional Trimer. J Biol Chem 2014; 289:14273-82. [PMID: 24692546 PMCID: PMC4022893 DOI: 10.1074/jbc.m114.549592] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Follicle-stimulating hormone receptor (FSHR), a G-protein coupled receptor, is an important drug target in the development of novel therapeutics for reproductive indications. The FSHR extracellular domains were observed in the crystal structure as a trimer, which enabled us to propose a novel model for the receptor activation mechanism. The model predicts that FSHR binds Asnα52-deglycosylated FSH at a 3-fold higher capacity than fully glycosylated FSH. It also predicts that, upon dissociation of the FSHR trimer into monomers, the binding of glycosylated FSH, but not deglycosylated FSH, would increase 3-fold, and that the dissociated monomers would in turn enhance FSHR binding and signaling activities by 3-fold. This study presents evidence confirming these predictions and provides crystallographic and mutagenesis data supporting the proposed model. The model also provides a mechanistic explanation to the agonist and antagonist activities of thyroid-stimulating hormone receptor autoantibodies. We conclude that FSHR exists as a functional trimer.
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Affiliation(s)
- Xuliang Jiang
- From the EMD Serono Research and Development Institute, Billerica, Massachusetts 01821 and
| | - David Fischer
- From the EMD Serono Research and Development Institute, Billerica, Massachusetts 01821 and
| | - Xiaoyan Chen
- the Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
| | - Sean D McKenna
- From the EMD Serono Research and Development Institute, Billerica, Massachusetts 01821 and
| | - Heli Liu
- the Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
| | - Venkataraman Sriraman
- From the EMD Serono Research and Development Institute, Billerica, Massachusetts 01821 and
| | - Henry N Yu
- From the EMD Serono Research and Development Institute, Billerica, Massachusetts 01821 and
| | - Andreas Goutopoulos
- From the EMD Serono Research and Development Institute, Billerica, Massachusetts 01821 and
| | - Steve Arkinstall
- From the EMD Serono Research and Development Institute, Billerica, Massachusetts 01821 and
| | - Xiaolin He
- the Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611
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59
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Asymmetric perturbations of signalling oligomers. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 114:153-69. [PMID: 24650570 DOI: 10.1016/j.pbiomolbio.2014.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 02/26/2014] [Accepted: 03/04/2014] [Indexed: 01/06/2023]
Abstract
This review focuses on rapid and reversible noncovalent interactions for symmetric oligomers of signalling proteins. Symmetry mismatch, transient symmetry breaking and asymmetric perturbations via chemical (ligand binding) and physical (electric or mechanic) effects can initiate the signalling events. Advanced biophysical methods can reveal not only structural symmetries of stable membrane-bound signalling proteins but also asymmetric functional transition states. Relevant techniques amenable to distinguish between symmetric and asymmetric architectures are discussed including those with the capability of capturing low-populated transient conformational states. Typical examples of signalling proteins are overviewed for symmetry breaking in dimers (GPCRs, growth factor receptors, transcription factors); trimers (acid-sensing ion channels); tetramers (voltage-gated cation channels, ionotropic glutamate receptor, CNG and CHN channels); pentameric ligand-gated and mechanosensitive channels; higher order oligomers (gap junction channel, chaperonins, proteasome, virus capsid); as well as primary and secondary transporters. In conclusion, asymmetric perturbations seem to play important functional roles in a broad range of communicating networks.
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60
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Ferré S, Casadó V, Devi LA, Filizola M, Jockers R, Lohse MJ, Milligan G, Pin JP, Guitart X. G protein-coupled receptor oligomerization revisited: functional and pharmacological perspectives. Pharmacol Rev 2014; 66:413-34. [PMID: 24515647 DOI: 10.1124/pr.113.008052] [Citation(s) in RCA: 427] [Impact Index Per Article: 42.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Most evidence indicates that, as for family C G protein-coupled receptors (GPCRs), family A GPCRs form homo- and heteromers. Homodimers seem to be a predominant species, with potential dynamic formation of higher-order oligomers, particularly tetramers. Although monomeric GPCRs can activate G proteins, the pentameric structure constituted by one GPCR homodimer and one heterotrimeric G protein may provide a main functional unit, and oligomeric entities can be viewed as multiples of dimers. It still needs to be resolved if GPCR heteromers are preferentially heterodimers or if they are mostly constituted by heteromers of homodimers. Allosteric mechanisms determine a multiplicity of possible unique pharmacological properties of GPCR homomers and heteromers. Some general mechanisms seem to apply, particularly at the level of ligand-binding properties. In the frame of the dimer-cooperativity model, the two-state dimer model provides the most practical method to analyze ligand-GPCR interactions when considering receptor homomers. In addition to ligand-binding properties, unique properties for each GPCR oligomer emerge in relation to different intrinsic efficacy of ligands for different signaling pathways (functional selectivity). This gives a rationale for the use of GPCR oligomers, and particularly heteromers, as novel targets for drug development. Herein, we review the functional and pharmacological properties of GPCR oligomers and provide some guidelines for the application of discrete direct screening and high-throughput screening approaches to the discovery of receptor-heteromer selective compounds.
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Affiliation(s)
- Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Department of Health and Human Services, 333 Cassell Drive, Baltimore, Maryland 21224.
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61
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Roche D, Gil D, Giraldo J. Mathematical modeling of G protein-coupled receptor function: what can we learn from empirical and mechanistic models? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 796:159-81. [PMID: 24158805 DOI: 10.1007/978-94-007-7423-0_8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Empirical and mechanistic models differ in their approaches to the analysis of pharmacological effect. Whereas the parameters of the former are not physical constants those of the latter embody the nature, often complex, of biology. Empirical models are exclusively used for curve fitting, merely to characterize the shape of the E/[A] curves. Mechanistic models, on the contrary, enable the examination of mechanistic hypotheses by parameter simulation. Regretfully, the many parameters that mechanistic models may include can represent a great difficulty for curve fitting, representing, thus, a challenge for computational method development. In the present study some empirical and mechanistic models are shown and the connections, which may appear in a number of cases between them, are analyzed from the curves they yield. It may be concluded that systematic and careful curve shape analysis can be extremely useful for the understanding of receptor function, ligand classification and drug discovery, thus providing a common language for the communication between pharmacologists and medicinal chemists.
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Affiliation(s)
- David Roche
- Laboratory of Systems Pharmacology and Bioinformatics, Institut de Neurociències and Unitat de Bioestadística, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
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62
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Moreira IS. Structural features of the G-protein/GPCR interactions. Biochim Biophys Acta Gen Subj 2013; 1840:16-33. [PMID: 24016604 DOI: 10.1016/j.bbagen.2013.08.027] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 01/07/2023]
Abstract
BACKGROUND The details of the functional interaction between G proteins and the G protein coupled receptors (GPCRs) have long been subjected to extensive investigations with structural and functional assays and a large number of computational studies. SCOPE OF REVIEW The nature and sites of interaction in the G-protein/GPCR complexes, and the specificities of these interactions selecting coupling partners among the large number of families of GPCRs and G protein forms, are still poorly defined. MAJOR CONCLUSIONS Many of the contact sites between the two proteins in specific complexes have been identified, but the three dimensional molecular architecture of a receptor-Gα interface is only known for one pair. Consequently, many fundamental questions regarding this macromolecular assembly and its mechanism remain unanswered. GENERAL SIGNIFICANCE In the context of current structural data we review the structural details of the interfaces and recognition sites in complexes of sub-family A GPCRs with cognate G-proteins, with special emphasis on the consequences of activation on GPCR structure, the prevalence of preassembled GPCR/G-protein complexes, the key structural determinants for selective coupling and the possible involvement of GPCR oligomerization in this process.
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Affiliation(s)
- Irina S Moreira
- REQUIMTE/Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal.
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63
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Mary S, Fehrentz JA, Damian M, Gaibelet G, Orcel H, Verdié P, Mouillac B, Martinez J, Marie J, Banères JL. Heterodimerization with Its splice variant blocks the ghrelin receptor 1a in a non-signaling conformation: a study with a purified heterodimer assembled into lipid discs. J Biol Chem 2013; 288:24656-65. [PMID: 23839942 DOI: 10.1074/jbc.m113.453423] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Heterodimerization of G protein-coupled receptors has an impact on their signaling properties, but the molecular mechanisms underlying heteromer-directed selectivity remain elusive. Using purified monomers and dimers reconstituted into lipid discs, we explored how dimerization impacts the functional and structural behavior of the ghrelin receptor. In particular, we investigated how a naturally occurring truncated splice variant of the ghrelin receptor exerts a dominant negative effect on ghrelin signaling upon dimerization with the full-length receptor. We provide direct evidence that this dominant negative effect is due to the ability of the non-signaling truncated receptor to restrict the conformational landscape of the full-length protein. Indeed, associating both proteins within the same disc blocks all agonist- and signaling protein-induced changes in ghrelin receptor conformation, thus preventing it from activating its cognate G protein and triggering arrestin 2 recruitment. This is an unambiguous demonstration that allosteric conformational events within dimeric assemblies can be directly responsible for modulation of signaling mediated by G protein-coupled receptors.
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Affiliation(s)
- Sophie Mary
- Institut des Biomolécules Max Mousseron (IBMM), CNRS UMR 5247, Université Montpellier 1, Faculté de Pharmacie, 15 avenue Charles Flahault, BP 14491, 34093 Montpellier Cedex 5, France
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64
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Functional significance of serotonin receptor dimerization. Exp Brain Res 2013; 230:375-86. [PMID: 23811735 DOI: 10.1007/s00221-013-3622-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Accepted: 06/10/2013] [Indexed: 01/01/2023]
Abstract
The original model of G-protein activation by a single G-protein-coupled receptor (GPCR) is giving way to a new model, wherein two protomers of a GPCR dimer interact with a single G-protein. This article will review the evidence suggesting that 5-HT receptors form dimers/oligomers and will compare the findings with the results obtained from the studies with other biogenic amine receptors. Topics to be covered include the origin or biogenesis of dimer formation, potential dimer interface(s), and oligomer size (dimer vs. tetramer or higher order). The functional significance will be discussed in terms of G-protein activation following ligand binding to one or two protomers in a dimeric structure, the formation of heterodimers, and the development of bivalent ligands.
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65
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Lavreysen H, Langlois X, Ahnaou A, Drinkenburg W, te Riele P, Biesmans I, Van der Linden I, Peeters L, Megens A, Wintmolders C, Cid JM, Trabanco AA, Andrés JI, Dautzenberg FM, Lütjens R, Macdonald G, Atack JR. Pharmacological characterization of JNJ-40068782, a new potent, selective, and systemically active positive allosteric modulator of the mGlu2 receptor and its radioligand [3H]JNJ-40068782. J Pharmacol Exp Ther 2013; 346:514-27. [PMID: 23766542 DOI: 10.1124/jpet.113.204990] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Modulation of the metabotropic glutamate type 2 (mGlu2) receptor is considered a promising target for the treatment of central nervous system diseases such as schizophrenia. Here, we describe the pharmacological properties of the novel mGlu2 receptor positive allosteric modulator (PAM) 3-cyano-1-cyclopropylmethyl-4-(4-phenyl-piperidin-1-yl)-pyridine-2(1H)-one (JNJ-40068782) and its radioligand [(3)H]JNJ-40068782. In guanosine 5'-O-(3-[(35)S]thio)triphosphate binding, JNJ-40068782 produced a leftward and upward shift in the glutamate concentration-effect curve at human recombinant mGlu2 receptors. The EC50 of JNJ-40068782 for potentiation of an EC20-equivalent concentration of glutamate was 143 nM. Although JNJ-40068782 did not affect binding of the orthosteric antagonist [(3)H]2S-2-amino-2-(1S,2S-2-carboxycyclopropyl-1-yl)-3-(xanth-9-yl)propanoic acid (LY-341495), it did potentiate the binding of the agonist [(3)H](2S,2'R,3'R)-2-(2',3'-dicarboxylcyclopropyl)glycine (DCG-IV), demonstrating that it can allosterically affect binding at the agonist recognition site. The binding of [(3)H]JNJ-40068782 to human recombinant mGlu2 receptors in Chinese hamster ovary cells and rat brain receptors was saturable with a KD of ∼10 nM. In rat brain, the anatomic distribution of [(3)H]JNJ-40068782 was consistent with mGlu2 expression previously described and was most abundant in cortex and hippocampus. The ability of structurally unrelated PAMs to displace [(3)H]JNJ-40068782 suggests that PAMs may bind to common determinants within the same site. It is noteworthy that agonists also increased the binding affinity of [(3)H]JNJ-40068782. JNJ-40068782 influenced rat sleep-wake organization by decreasing rapid eye movement sleep with a lowest active dose of 3 mg/kg PO. In mice, JNJ-40068782 reversed phencyclidine-induced hyperlocomotion with an ED50 of 5.7 mg/kg s.c. Collectively, the present data demonstrate that JNJ-40068782 has utility in investigating the potential of mGlu2 modulation for the treatment of diseases characterized by disturbed glutamatergic signaling and highlight the value of [(3)H]JNJ-40068782 in exploring allosteric binding.
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66
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Giraldo J. Modeling cooperativity effects in dimeric G protein-coupled receptors. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 115:349-73. [PMID: 23415098 DOI: 10.1016/b978-0-12-394587-7.00008-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
G protein-coupled receptors organize into oligomeric arrangements to exert their function. In this chapter, three models of dimeric receptors, the two-state dimer receptor model, the metabotropic glutamate receptor model, and the asymmetric/symmetric three-state dimer receptor model are revisited focusing on the cooperative effects between their binding sites and the subunits they are composed of. The mathematical analysis reveals the complexity of the intra-receptor interactions providing insights on the mechanistic aspects of receptor function.
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Affiliation(s)
- Jesús Giraldo
- Laboratory of Systems Pharmacology and Bioinformatics, Institut de Neurociències and Unitat de Bioestadística, Universitat Autònoma de Barcelona, Bellaterra, Spain
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Lane JR, Canals M. Sequential conformational rearrangements dictate the dynamics of class C GPCR activation. Sci Signal 2012; 5:pe51. [PMID: 23169816 DOI: 10.1126/scisignal.2003503] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Heterotrimeric GTP-binding protein (G protein)-coupled receptors (GPCRs) are the largest family of cell surface receptors; they allow cells to respond to a wide range of endogenous and environmental signals. Class C GPCRs represent a discrete group within the GPCR family, with distinct structural characteristics. Receptors belonging to this class--such as γ-aminobutyric acid type B (GABA(B)) receptors or metabotropic glutamate receptors (mGluRs)--form constitutive dimers. However, the conformational changes within such a dimeric receptor that are associated with agonist activation are still not well understood. A study by Hlavackova et al. investigates the role of dimer formation in mGluR1 activation. Using fluorescence resonance energy transfer approaches to assess inter- and intrasubunit conformational changes, the authors present an elegant study that sheds light on the kinetics of domain rearrangements in a class C GPCR upon ligand binding.
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Affiliation(s)
- J Robert Lane
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, and Department of Pharmacology, Monash University, Parkville, Victoria 3052, Australia
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68
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Distinct roles of metabotropic glutamate receptor dimerization in agonist activation and G-protein coupling. Proc Natl Acad Sci U S A 2012; 109:16342-7. [PMID: 22988116 DOI: 10.1073/pnas.1205838109] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The eight metabotropic glutamate receptors (mGluRs) are key modulators of synaptic transmission and are considered promising targets for the treatment of various brain disorders. Whereas glutamate acts at a large extracellular domain, allosteric modulators have been identified that bind to the seven transmembrane domain (7TM) of these dimeric G-protein-coupled receptors (GPCRs). We show here that the dimeric organization of mGluRs is required for the modulation of active and inactive states of the 7TM by agonists, but is not necessary for G-protein activation. Monomeric mGlu2, either as an isolated 7TM or in full-length, purified and reconstituted into nanodiscs, couples to G proteins upon direct activation by a positive allosteric modulator. However, only a reconstituted full-length dimeric mGlu2 activates G protein upon glutamate binding, suggesting that dimerization is required for glutamate induced activation. These data show that, even for such well characterized GPCR dimers like mGluR2, a single 7TM is sufficient for G-protein coupling. Despite this observation, the necessity of dimeric architecture for signaling induced by the endogenous ligand glutamate confirms that the central core of signaling complex is dimeric.
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69
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Hlavackova V, Zabel U, Frankova D, Bätz J, Hoffmann C, Prezeau L, Pin JP, Blahos J, Lohse MJ. Sequential inter- and intrasubunit rearrangements during activation of dimeric metabotropic glutamate receptor 1. Sci Signal 2012; 5:ra59. [PMID: 22894836 DOI: 10.1126/scisignal.2002720] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The metabotropic glutamate receptor 1 (mGluR1), a class C member of the heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor family, is a constitutive dimer that regulates excitatory neurotransmission. We investigated the role of homodimer formation in mGluR1 activation by examining activation-dependent inter- and intrasubunit conformational changes by fluorescence resonance energy transfer (FRET). We inserted yellow and cyan fluorescent proteins in the second intracellular loop and at the carboxyl terminus of mGluR1 to act as FRET sensors and expressed these proteins in human embryonic kidney 293 cells. Agonist-dependent activation of these mGluR1 chimeras rapidly increased the intersubunit FRET, suggesting rapid movement of the subunits relative to each other. After intersubunit movement, the intrasubunit FRET decreased, reflecting conformational changes within a subunit. Cotransfection of chimeric receptor subunits that were capable or incapable of G protein coupling revealed that only a single subunit assumes an active state in an mGluR1 receptor dimer.
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Affiliation(s)
- Veronika Hlavackova
- Institute of Pharmacology and Toxicology, University of Würzburg, 97078 Würzburg, Germany
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70
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Zoenen M, Urizar E, Swillens S, Vassart G, Costagliola S. Evidence for activity-regulated hormone-binding cooperativity across glycoprotein hormone receptor homomers. Nat Commun 2012; 3:1007. [DOI: 10.1038/ncomms1991] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 07/06/2012] [Indexed: 11/09/2022] Open
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Kammermeier PJ. Functional and pharmacological characteristics of metabotropic glutamate receptors 2/4 heterodimers. Mol Pharmacol 2012; 82:438-47. [PMID: 22653971 DOI: 10.1124/mol.112.078501] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Metabotropic glutamate receptors (mGluRs) were thought until recently to function mainly as stable homodimers, but recent work suggests that heteromerization is possible. Despite the growth in available compounds targeting mGluRs, little is known about the pharmacological profile of mGluR heterodimers. Here, this question was addressed for the mGluR2/4 heterodimer, examined by coexpressing both receptors in isolated sympathetic neurons from the rat superior cervical ganglion (SCG), a native neuronal system with a null mGluR background. Under conditions that favor mGluR2/4 heterodimer formation, activation of the receptor was not evident with the mGluR2-selective agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) or with the mGluR4 selective agonist L-(+)-2-amino-4-phosphonobutyric acid (L-AP4); however, full activation was apparent when both ligands were applied together, confirming that mGluR dimers require ligand binding in both subunits for full activation. Properties of allosteric modulators were also examined, including the findings that negative allosteric modulators (NAMs) have two binding sites per dimer and that positive allosteric modulators (PAMs) have only a single site per dimer. In SCG neurons, mGluR2/4 dimers were not inhibited by the mGluR2-selective NAM (Z)-1-[2-cycloheptyloxy-2-(2,6-dichlorophenyl)ethenyl]-1H-1,2,4-triazole (Ro 64-5229), supporting the two-site model. Furthermore, application of the mGluR4 selective PAMs N-(4-chloro-3-methoxyphenyl)-2-pyridinecarboxamide (VU0361737) or N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxamide (PHCCC) and combined application of mGluR4 PAMs with the mGluR2 selective PAM biphenyl indanone-A failed to potentiate glutamate responses through mGluR2/4, suggesting that mGluR2/4 heterodimers are not modulatable by PAMs that are currently available.
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Affiliation(s)
- Paul J Kammermeier
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York, USA.
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72
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Lundström L, Bissantz C, Beck J, Wettstein JG, Woltering TJ, Wichmann J, Gatti S. Structural determinants of allosteric antagonism at metabotropic glutamate receptor 2: mechanistic studies with new potent negative allosteric modulators. Br J Pharmacol 2012; 164:521-37. [PMID: 21470207 DOI: 10.1111/j.1476-5381.2011.01409.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND AND PURPOSE Altered glutamatergic neurotransmission is linked to several neurological and psychiatric disorders. Metabotropic glutamate receptor 2 (mGlu₂) plays an important role on the presynaptic control of glutamate release and negative allosteric modulators (NAMs) acting on mGlu₂/₃ receptors are under assessment for their potential as antidepressants, neurogenics and cognitive enhancers. Two new potent mGlu₂/₃ NAMs, RO4988546 and RO5488608, are described in this study and the allosteric binding site in the transmembrane (TM) domain of mGlu₂ is characterized. EXPERIMENTAL APPROACH Site directed mutagenesis, functional measurements and β₂-adrenoceptor-based modelling of mGlu₂ were employed to identify important molecular determinants of two new potent mGlu₂/₃ NAMs. KEY RESULTS RO4988546 and RO5488608 affected both [³H]-LY354740 agonist binding at the orthosteric site and the binding of a tritiated positive allosteric modulator (³H-PAM), indicating that NAMs and PAMs could have overlapping binding sites in the mGlu₂ TM domain. We identified eight residues in the allosteric binding pocket that are crucial for non-competitive antagonism of agonist-dependent activation of mGlu₂ and directly interact with the NAMs: Arg³·²⁸, Arg³·²⁹, Phe³·³⁶, His(E2.52) , Leu⁵·⁴³, Trp⁶·⁴⁸, Phe⁶·⁵⁵ and Val⁷·⁴³. The mGlu₂ specific residue His(E2.52) is likely to be involved in selectivity and residues located in the outer part of the binding pocket are more important for [³H]-LY354740 agonist binding inhibition, which is independent of the highly conserved Trp⁶·⁴⁸ residue. CONCLUSIONS AND IMPLICATIONS This is the first complete molecular investigation of the allosteric binding pocket of mGlu₂ and Group II mGluRs and provides new information on what determines mGlu₂ NAMs selective interactions and effects.
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Affiliation(s)
- L Lundström
- Neuroscience Research, F. Hoffmann-La Roche Ltd, Basel, Switzerland
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73
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Zhang M, Guan R, Segaloff DL. Revisiting and questioning functional rescue between dimerized LH receptor mutants. Mol Endocrinol 2012; 26:655-68. [PMID: 22403174 DOI: 10.1210/me.2011-1285] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The glycoprotein hormone receptors are G protein-coupled receptors containing a large extracellular domain fused to a prototypical serpentine domain. cis-activation occurs when binding of hormone to the extracellular domain stabilizes the serpentine domain in an active conformation. Studies by others suggested that these receptors can also signal by trans-activation, where hormone binding to one receptor protomer activates the serpentine domain of an associated protomer, as documented by the partial rescue of hormone-dependent signaling when a binding defective mutant is coexpressed with a signaling defective mutant. However, our characterizations of several LH receptor (LHR) mutants used in previous studies differ markedly from those originally reported. Also, when examining a pair of LHR mutants previously shown to functionally rescue in vitro as well as in vivo, in addition to finding that the properties of the individual mutants differ significantly from those originally described, we determined that when this pair of mutants was coexpressed in vitro, quantitative analyses did not indicate functional rescue. Additional data are presented that provide a plausible alternate explanation for the apparent in vivo trans-activation that was reported. Finally, using LHR mutants that we have documented to be expressed at the cell surface but to lack human chorionic gonadotropin binding activity or to be severely impaired in their ability to activate Gs, we did not observe functional rescue of human chorionic gonadotropin-stimulated cAMP when the mutants were coexpressed, even though bioluminescence resonance energy transfer analyses confirmed that the coexpressed mutants formed dimers. Taken altogether, our data substantively question the concept of functional rescue between LHR mutants.
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Affiliation(s)
- Meilin Zhang
- Department of Molecular Physiology and Biophysics, The Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa 52246, USA
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74
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Lohse MJ, Nuber S, Hoffmann C. Fluorescence/bioluminescence resonance energy transfer techniques to study G-protein-coupled receptor activation and signaling. Pharmacol Rev 2012; 64:299-336. [PMID: 22407612 DOI: 10.1124/pr.110.004309] [Citation(s) in RCA: 251] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Fluorescence and bioluminescence resonance energy transfer (FRET and BRET) techniques allow the sensitive monitoring of distances between two labels at the nanometer scale. Depending on the placement of the labels, this permits the analysis of conformational changes within a single protein (for example of a receptor) or the monitoring of protein-protein interactions (for example, between receptors and G-protein subunits). Over the past decade, numerous such techniques have been developed to monitor the activation and signaling of G-protein-coupled receptors (GPCRs) in both the purified, reconstituted state and in intact cells. These techniques span the entire spectrum from ligand binding to the receptors down to intracellular second messengers. They allow the determination and the visualization of signaling processes with high temporal and spatial resolution. With these techniques, it has been demonstrated that GPCR signals may show spatial and temporal patterning. In particular, evidence has been provided for spatial compartmentalization of GPCRs and their signals in intact cells and for distinct physiological consequences of such spatial patterning. We review here the FRET and BRET technologies that have been developed for G-protein-coupled receptors and their signaling proteins (G-proteins, effectors) and the concepts that result from such experiments.
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Affiliation(s)
- Martin J Lohse
- Institute of Pharmacology and Toxicology, Versbacher Str. 9, 97078 Würzburg, Germany.
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75
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Huang Y, Cavanaugh A, Breitwieser GE. Regulation of stability and trafficking of calcium-sensing receptors by pharmacologic chaperones. ADVANCES IN PHARMACOLOGY 2012; 62:143-73. [PMID: 21907909 DOI: 10.1016/b978-0-12-385952-5.00007-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Gain- or loss-of-function mutations and polymorphisms of the calcium-sensing receptor (CaSR) cause Ca(2+) handling diseases. Altered expression and/or signaling of wild-type CaSR can also contribute to pathology. Recent studies have demonstrated that a significant proportion of mutations cause altered targeting and/or trafficking of CaSR to the plasma membrane. Pharmacological approaches to rescue of CaSR function include treatment with allosteric modulators, which potentiate the effects of the orthosteric agonist Ca(2+). Dissection of the mechanism(s) contributing to allosteric agonist-mediated rescue of loss-of-function CaSR mutants has demonstrated pharmacologic chaperone actions coincident with CaSR biosynthesis. The distinctive responses to the allosteric agonist (NPS R-568), which promotes CaSR stability, and the allosteric antagonist (NPS 2143), which promotes CaSR degradation, have led to a model for a conformational checkpoint during CaSR biosynthesis. The conformational checkpoint would "tune" CaSR biosynthesis to cellular signaling state. Navigation of a distinct checkpoint for endoplasmic release can also be augmented by pharmacologic chaperones. The diverse, post-endoplasmic reticulum quality control site(s) for pharmacologic chaperone modulation of CaSR stability and trafficking redefines the role(s) of allosteric modulators in regulation of overall GPCR function.
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Affiliation(s)
- Ying Huang
- Cancer Drug Research Laboratory, McGill University, Royal Victoria Hospital, Montreal, Quebec, Canada
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76
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Cottet M, Faklaris O, Maurel D, Scholler P, Doumazane E, Trinquet E, Pin JP, Durroux T. BRET and Time-resolved FRET strategy to study GPCR oligomerization: from cell lines toward native tissues. Front Endocrinol (Lausanne) 2012; 3:92. [PMID: 22837753 PMCID: PMC3401989 DOI: 10.3389/fendo.2012.00092] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 07/03/2012] [Indexed: 11/13/2022] Open
Abstract
The concept of oligomerization of G protein-coupled receptor (GPCR) opens new perspectives regarding physiological function regulation. The capacity of one GPCR to modify its binding and coupling properties by interacting with a second one can be at the origin of regulations unsuspected two decades ago. Although the concept is interesting, its validation at a physiological level is challenging and probably explains why receptor oligomerization is still controversial. Demonstrating direct interactions between two proteins is not trivial since few techniques present a spatial resolution allowing this precision. Resonance energy transfer (RET) strategies are actually the most convenient ones. During the last two decades, bioluminescent resonance energy transfer and time-resolved fluorescence resonance energy transfer (TR-FRET) have been widely used since they exhibit high signal-to-noise ratio. Most of the experiments based on GPCR labeling have been performed in cell lines and it has been shown that all GPCRs have the propensity to form homo- or hetero-oligomers. However, whether these data can be extrapolated to GPCRs expressed in native tissues and explain receptor functioning in real life, remains an open question. Native tissues impose different constraints since GPCR sequences cannot be modified. Recently, a fluorescent ligand-based GPCR labeling strategy combined to a TR-FRET approach has been successfully used to prove the existence of GPCR oligomerization in native tissues. Although the RET-based strategies are generally quite simple to implement, precautions have to be taken before concluding to the absence or the existence of specific interactions between receptors. For example, one should exclude the possibility of collision of receptors diffusing throughout the membrane leading to a specific FRET signal. The advantages and the limits of different approaches will be reviewed and the consequent perspectives discussed.
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Affiliation(s)
- Martin Cottet
- Institut de Génomique Fonctionnelle CNRS, UMR 5203,Montpellier, France
- INSERM, U.661, Montpellier and Université Montpellier 1,2,Montpellier, France
| | - Orestis Faklaris
- Institut de Génomique Fonctionnelle CNRS, UMR 5203,Montpellier, France
- INSERM, U.661, Montpellier and Université Montpellier 1,2,Montpellier, France
| | - Damien Maurel
- Institut de Génomique Fonctionnelle CNRS, UMR 5203,Montpellier, France
- INSERM, U.661, Montpellier and Université Montpellier 1,2,Montpellier, France
| | - Pauline Scholler
- Institut de Génomique Fonctionnelle CNRS, UMR 5203,Montpellier, France
- INSERM, U.661, Montpellier and Université Montpellier 1,2,Montpellier, France
| | - Etienne Doumazane
- Institut de Génomique Fonctionnelle CNRS, UMR 5203,Montpellier, France
- INSERM, U.661, Montpellier and Université Montpellier 1,2,Montpellier, France
| | | | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle CNRS, UMR 5203,Montpellier, France
- INSERM, U.661, Montpellier and Université Montpellier 1,2,Montpellier, France
| | - Thierry Durroux
- Institut de Génomique Fonctionnelle CNRS, UMR 5203,Montpellier, France
- INSERM, U.661, Montpellier and Université Montpellier 1,2,Montpellier, France
- *Correspondence: Thierry Durroux, Institut de Génomique Fonctionnelle CNRS, UMR 5203, Montpellier, France; INSERM U661, Montpellier and Université Montpellier 1,2, 141 Rue de la Cardonille, 34094 Montpellier Cedex 5, France. e-mail:
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77
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Prézeau L, Rondard P, Goudet C, Kniazeff J, Pin JP. Class C receptor activation mechanisms illustrated by mGlu and GABAB receptors. A review. FLAVOUR FRAG J 2011. [DOI: 10.1002/ffj.2044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Laurent Prézeau
- CNRS, UMR 5203; Institut de Génomique Fonctionnelle, INSERM, U661, and Université Montpellier 1, 2; Montpellier; F-34000; France
| | - Philippe Rondard
- CNRS, UMR 5203; Institut de Génomique Fonctionnelle, INSERM, U661, and Université Montpellier 1, 2; Montpellier; F-34000; France
| | - Cyril Goudet
- CNRS, UMR 5203; Institut de Génomique Fonctionnelle, INSERM, U661, and Université Montpellier 1, 2; Montpellier; F-34000; France
| | - Julie Kniazeff
- CNRS, UMR 5203; Institut de Génomique Fonctionnelle, INSERM, U661, and Université Montpellier 1, 2; Montpellier; F-34000; France
| | - Jean-Philippe Pin
- CNRS, UMR 5203; Institut de Génomique Fonctionnelle, INSERM, U661, and Université Montpellier 1, 2; Montpellier; F-34000; France
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78
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Maurice P, Kamal M, Jockers R. Asymmetry of GPCR oligomers supports their functional relevance. Trends Pharmacol Sci 2011; 32:514-20. [PMID: 21715028 DOI: 10.1016/j.tips.2011.05.006] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 05/19/2011] [Accepted: 05/20/2011] [Indexed: 01/29/2023]
Abstract
G protein-coupled receptors (GPCRs) can exist as dimers or as larger oligomeric clusters that enable intercommunication between different receptor protomers within the same complex. This phenomenon is observed at three distinct levels: (i) at the level of ligand binding where the activation of one protomer can allosterically inhibit or facilitate ligand binding to the second protomer; (ii) at the level of ligand-induced conformational switches, which occur between transmembrane domains of the two protomers; and (iii) within GPCR-associated protein complexes, either directly at the level of GPCR-interacting proteins or at further downstream levels of the complex. Intercommunication at these different levels introduces asymmetry within GPCR dimers wherein each protomer fulfills its specific task. In this review, we discuss how the asymmetric behavior of GPCRs highlights the advantage of oligomeric receptor organization and supports the functional relevance of GPCR dimerization.
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Affiliation(s)
- Pascal Maurice
- Inserm, U1016, Institut Cochin, 22 rue Méchain, 75014 Paris, France
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79
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Abstract
Over the past 20 years, naturally occurring mutations that affect G protein-coupled receptors (GPCRs) have been identified, mainly in patients with endocrine diseases. The study of loss-of-function or gain-of-function mutations has contributed to our understanding of the pathophysiology of several diseases with classic hypophenotypes or hyperphenotypes of the target endocrine organs, respectively. Simultaneously, study of the mutant receptors ex vivo was instrumental in delineating the relationships between the structure and function of these important physiological and pharmacological molecules. Now that access to the crystallographic structure of a few GPCRs is available, the mechanics of these receptors can be studied at the atomic level. Progress in the fields of cell biology, molecular pharmacology and proteomics has also widened our view of GPCR functions. Initially considered simply as guanine nucleotide exchange factors capable of activating G protein-dependent regulatory cascades, GPCRs are now known to display several additional characteristics, each susceptible to alterations by disease-causing mutations. These characteristics include functionally important basal activity of the receptor; differential activation of various G proteins; differential activation of G protein-dependent and independent effects (biased agonism); interaction with proteins that modify receptor function; dimerization-dependent effects; and interaction with allosteric modulators. This Review attempts to illustrate how natural mutations of GPCR could contribute to our understanding of these novel facets of GPCR biology.
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Affiliation(s)
- Gilbert Vassart
- Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Faculty of Medicine, Université Libre de Bruxelles, 808 Route de Lennik, 1070 Brussels, Belgium.
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80
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Smith NJ, Milligan G. Allostery at G protein-coupled receptor homo- and heteromers: uncharted pharmacological landscapes. Pharmacol Rev 2011; 62:701-25. [PMID: 21079041 DOI: 10.1124/pr.110.002667] [Citation(s) in RCA: 211] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
For many years seven transmembrane domain G protein-coupled receptors (GPCRs) were thought to exist and function exclusively as monomeric units. However, evidence both from native cells and heterologous expression systems has demonstrated that GPCRs can both traffic and signal within higher-order complexes. As for other protein-protein interactions, conformational changes in one polypeptide, including those resulting from binding of pharmacological ligands, have the capacity to alter the conformation and therefore the response of the interacting protein(s), a process known as allosterism. For GPCRs, allosterism across homo- or heteromers, whether dimers or higher-order oligomers, represents an additional topographical landscape that must now be considered pharmacologically. Such effects may offer the opportunity for novel therapeutic approaches. Allosterism at GPCR heteromers is particularly exciting in that it offers additional scope to provide receptor subtype selectivity and tissue specificity as well as fine-tuning of receptor signal strength. Herein, we introduce the concept of allosterism at both GPCR homomers and heteromers and discuss the various questions that must be addressed before significant advances can be made in drug discovery at these GPCR complexes.
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Affiliation(s)
- Nicola J Smith
- Molecular Pharmacology Laboratory,University Avenue, University of Glasgow, Glasgow, Scotland
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81
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Pellissier LP, Barthet G, Gaven F, Cassier E, Trinquet E, Pin JP, Marin P, Dumuis A, Bockaert J, Banères JL, Claeysen S. G protein activation by serotonin type 4 receptor dimers: evidence that turning on two protomers is more efficient. J Biol Chem 2011; 286:9985-97. [PMID: 21247891 DOI: 10.1074/jbc.m110.201939] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The discovery that class C G protein-coupled receptors (GPCRs) function as obligatory dimeric entities has generated major interest in GPCR oligomerization. Oligomerization now appears to be a common feature among all GPCR classes. However, the functional significance of this process remains unclear because, in vitro, some monomeric GPCRs, such as rhodopsin and β(2)-adrenergic receptors, activate G proteins. By using wild type and mutant serotonin type 4 receptors (5-HT(4)Rs) (including a 5-HT(4)-RASSL) expressed in COS-7 cells as models of class A GPCRs, we show that activation of one protomer in a dimer was sufficient to stimulate G proteins. However, coupling efficiency was 2 times higher when both protomers were activated. Expression of combinations of 5-HT(4), in which both protomers were able to bind to agonists but only one could couple to G proteins, suggested that upon agonist occupancy, protomers did not independently couple to G proteins but rather that only one G protein was activated. Coupling of a single heterotrimeric G(s) protein to a receptor dimer was further confirmed in vitro, using the purified recombinant WT RASSL 5-HT(4)R obligatory heterodimer. These results, together with previous findings, demonstrate that, differently from class C GPCR dimers, class A GPCR dimers have pleiotropic activation mechanisms.
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Affiliation(s)
- Lucie P Pellissier
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS UMR5203, F-34094 Montpellier, France
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82
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Urwyler S. Allosteric modulation of family C G-protein-coupled receptors: from molecular insights to therapeutic perspectives. Pharmacol Rev 2011; 63:59-126. [PMID: 21228259 DOI: 10.1124/pr.109.002501] [Citation(s) in RCA: 164] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Allosteric receptor modulation is an attractive concept in drug targeting because it offers important potential advantages over conventional orthosteric agonism or antagonism. Allosteric ligands modulate receptor function by binding to a site distinct from the recognition site for the endogenous agonist. They often have no effect on their own and therefore act only in conjunction with physiological receptor activation. This article reviews the current status of allosteric modulation at family C G-protein coupled receptors in the light of their specific structural features on the one hand and current concepts in receptor theory on the other hand. Family C G-protein-coupled receptors are characterized by a large extracellular domain containing the orthosteric agonist binding site known as the "venus flytrap module" because of its bilobal structure and the dynamics of its activation mechanism. Mutational analysis and chimeric constructs have revealed that allosteric modulators of the calcium-sensing, metabotropic glutamate and GABA(B) receptors bind to the seven transmembrane domain, through which they modify signal transduction after receptor activation. This is in contrast to taste-enhancing molecules, which bind to different parts of sweet and umami receptors. The complexity of interactions between orthosteric and allosteric ligands is revealed by a number of adequate biochemical and electrophysiological assay systems. Many allosteric family C GPCR modulators show in vivo efficacy in behavioral models for a variety of clinical indications. The positive allosteric calcium sensing receptor modulator cinacalcet is the first drug of this type to enter the market and therefore provides proof of principle in humans.
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Affiliation(s)
- Stephan Urwyler
- Department of Chemistry and Biochemistry, University of Berne, P/A Weissensteinweg 3, CH-3303 Jegenstorf, Berne, Switzerland.
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Nicoletti F, Bockaert J, Collingridge GL, Conn PJ, Ferraguti F, Schoepp DD, Wroblewski JT, Pin JP. Metabotropic glutamate receptors: from the workbench to the bedside. Neuropharmacology 2010; 60:1017-41. [PMID: 21036182 DOI: 10.1016/j.neuropharm.2010.10.022] [Citation(s) in RCA: 476] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Revised: 10/15/2010] [Accepted: 10/21/2010] [Indexed: 12/24/2022]
Abstract
Metabotropic glutamate (mGlu) receptors were discovered in the mid 1980s and originally described as glutamate receptors coupled to polyphosphoinositide hydrolysis. Almost 6500 articles have been published since then, and subtype-selective mGlu receptor ligands are now under clinical development for the treatment of a variety of disorders such as Fragile-X syndrome, schizophrenia, Parkinson's disease and L-DOPA-induced dyskinesias, generalized anxiety disorder, chronic pain, and gastroesophageal reflux disorder. Prof. Erminio Costa was linked to the early times of the mGlu receptor history, when a few research groups challenged the general belief that glutamate could only activate ionotropic receptors and all metabolic responses to glutamate were secondary to calcium entry. This review moves from those nostalgic times to the most recent advances in the physiology and pharmacology of mGlu receptors, and highlights the role of individual mGlu receptor subtypes in the pathophysiology of human disorders. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.
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Affiliation(s)
- F Nicoletti
- Department of Physiology and Pharmacology, University of Rome, Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy.
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84
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Doumazane E, Scholler P, Zwier JM, Trinquet E, Rondard P, Pin JP. A new approach to analyze cell surface protein complexes reveals specific heterodimeric metabotropic glutamate receptors. FASEB J 2010; 25:66-77. [PMID: 20826542 DOI: 10.1096/fj.10-163147] [Citation(s) in RCA: 227] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
G-protein-coupled receptors (GPCRs) can form heteromeric complexes. Herein, we describe a new approach to test the heteromerization of 2 receptors, or 2 receptor subunits, and to study the stoichiometry of the resulting complexes. As a proof-of-concept study, we investigated whether metabotropic glutamate receptors (mGluRs), in addition to being well-known homodimers, can form heteromers. To that aim, we combine the benefits of time-resolved fluorescence resonance energy transfer (trFRET) with the specific, cell-surface labeling of SNAP- and CLIP-tagged rat mGluR subunits, expressed in a mammalian cell line. First, we show that mGlu2 and mGlu4 subunits (but not mGlu2 and mGlu1) can heteromerize. Moreover, our trFRET data are consistent with mGluR subunits forming strict homodimeric receptors on single expression, and a combination of strict heterodimeric and strict homodimeric receptors on coexpression. Second, a comprehensive analysis reveals that from the 21 possible pairs of 2 mGluR subunits out of 7 subtypes (mGlu1 to 8, but not 6), only 11 are able to form heterodimers. These findings were further validated by biochemical and functional complementation studies. In addition to describing a new method to analyze cell-surface receptor complexes, our data reveal a new level of complexity within the mGluR family.
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Affiliation(s)
- Etienne Doumazane
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, Montpellier, France
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85
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Rondard P, Goudet C, Kniazeff J, Pin JP, Prézeau L. The complexity of their activation mechanism opens new possibilities for the modulation of mGlu and GABAB class C G protein-coupled receptors. Neuropharmacology 2010; 60:82-92. [PMID: 20713070 DOI: 10.1016/j.neuropharm.2010.08.009] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Revised: 07/30/2010] [Accepted: 08/06/2010] [Indexed: 12/24/2022]
Abstract
In the human genome, 22 genes are coding for the class C G protein-coupled receptors that are receptors for the two main neurotransmitters glutamate and γ-aminobutyric acid, for Ca(2+) and for sweet and amino acid taste compounds. In addition to the GPCR heptahelical transmembrane domain responsible for G-protein activation, class C receptors possess a large extracellular domain that is responsible for ligand recognition. Recent studies had revealed that class C receptors are homo- or heterodimers with unique mechanism of activation. In the present review, we present an up-to-date view of the structures and activation mechanism of these receptors in particular the metabotropic glutamate and GABA(B) receptors. We show how the complexity of functioning of these transmembrane proteins can be used for the development of therapeutics to modulate their activity. We emphasize on the new approaches and drugs that could potentially become important in the future pharmacology of these receptors.
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86
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Albizu L, Cottet M, Kralikova M, Stoev S, Seyer R, Brabet I, Roux T, Bazin H, Bourrier E, Lamarque L, Breton C, Rives ML, Newman A, Javitch J, Trinquet E, Manning M, Pin JP, Mouillac B, Durroux T. Time-resolved FRET between GPCR ligands reveals oligomers in native tissues. Nat Chem Biol 2010; 6:587-94. [PMID: 20622858 DOI: 10.1038/nchembio.396] [Citation(s) in RCA: 261] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Accepted: 05/07/2010] [Indexed: 01/03/2023]
Abstract
G protein-coupled receptor (GPCR) oligomers have been proposed to play critical roles in cell signaling, but confirmation of their existence in a native context remains elusive, as no direct interactions between receptors have been reported. To demonstrate their presence in native tissues, we developed a time-resolved FRET strategy that is based on receptor labeling with selective fluorescent ligands. Specific FRET signals were observed with four different receptors expressed in cell lines, consistent with their dimeric or oligomeric nature in these transfected cells. More notably, the comparison between FRET signals measured with sets of fluorescent agonists and antagonists was consistent with an asymmetric relationship of the two protomers in an activated GPCR dimer. Finally, we applied the strategy to native tissues and succeeded in demonstrating the presence of oxytocin receptor dimers and/or oligomers in mammary gland.
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Affiliation(s)
- Laura Albizu
- Institut de Génomique Fonctionnelle, Centre National de la Recherche Scientifique, Montpellier, France
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87
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Pin JP, Prézeau L. Allosteric modulators of GABA(B) receptors: mechanism of action and therapeutic perspective. Curr Neuropharmacol 2010; 5:195-201. [PMID: 19305802 PMCID: PMC2656813 DOI: 10.2174/157015907781695919] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2007] [Accepted: 04/05/2007] [Indexed: 12/19/2022] Open
Abstract
γ-aminobutyric acid (GABA) plays important roles in the central nervous system, acting as a neurotransmitter on both ionotropic ligand-gated Cl--channels, and metabotropic G-protein coupled receptors (GPCRs). These two types of receptors called GABAA (and C) and GABAB are the targets of major therapeutic drugs such as the anxiolytic benzodiazepines, and antispastic drug baclofen (lioresal®), respectively. Although the multiplicity of GABAA receptors offer a number of possibilities to discover new and more selective drugs, the molecular characterization of the GABAB receptor revealed a unique, though complex, heterodimeric GPCR. High throughput screening strategies carried out in pharmaceutical industries, helped identifying new compounds positively modulating the activity of the GABAB receptor. These molecules, almost devoid of apparent activity when applied alone, greatly enhance both the potency and efficacy of GABAB agonists. As such, in contrast to baclofen that constantly activates the receptor everywhere in the brain, these positive allosteric modulators induce a large increase in GABAB-mediated responses only WHERE and WHEN physiologically needed. Such compounds are then well adapted to help GABA to activate its GABAB receptors, like benzodiazepines favor GABAA receptor activation. In this review, the way of action of these molecules will be presented in light of our actual knowledge of the activation mechanism of the GABAB receptor. We will then show that, as expected, these molecules have more pronounced in vivo responses and less side effects than pure agonists, offering new potential therapeutic applications for this new class of GABAB ligands.
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88
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The asymmetric/symmetric activation of GPCR dimers as a possible mechanistic rationale for multiple signalling pathways. Trends Pharmacol Sci 2010; 31:15-21. [DOI: 10.1016/j.tips.2009.10.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 10/23/2009] [Accepted: 10/26/2009] [Indexed: 11/16/2022]
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89
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Arcemisbéhère L, Sen T, Boudier L, Balestre MN, Gaibelet G, Detouillon E, Orcel H, Mendre C, Rahmeh R, Granier S, Vivès C, Fieschi F, Damian M, Durroux T, Banères JL, Mouillac B. Leukotriene BLT2 receptor monomers activate the G(i2) GTP-binding protein more efficiently than dimers. J Biol Chem 2009; 285:6337-47. [PMID: 20026606 DOI: 10.1074/jbc.m109.083477] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Accumulating evidence indicates that G protein-coupled receptors can assemble as dimers/oligomers but the role of this phenomenon in G protein coupling and signaling is not yet clear. We have used the purified leukotriene B(4) receptor BLT2 as a model to investigate the capacity of receptor monomers and dimers to activate the adenylyl cyclase inhibitory G(i2) protein. For this, we overexpressed the recombinant receptor as inclusion bodies in the Escherichia coli prokaryotic system, using a human alpha(5) integrin as a fusion partner. This strategy allowed the BLT2 as well as several other G protein-coupled receptors from different families to be produced and purified in large amounts. The BLT2 receptor was then successfully refolded to its native state, as measured by high-affinity LTB(4) binding in the presence of the purified G protein G alpha(i2). The receptor dimer, in which the two protomers displayed a well defined parallel orientation as assessed by fluorescence resonance energy transfer, was then separated from the monomer. Using two methods of receptor-catalyzed guanosine 5'-3-O-(thio)triphosphate binding assay, we clearly demonstrated that monomeric BLT2 stimulates the purified G alpha(i2) beta(1) gamma(2) protein more efficiently than the dimer. These data suggest that assembly of two BLT2 protomers into a dimer results in the reduced ability to signal.
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Affiliation(s)
- Laure Arcemisbéhère
- CNRS UMR 5203, Institut de Génomique Fonctionnelle, Département de Pharmacologie Moléculaire, Montpellier, France
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90
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Miller J, Agarwal A, Devi LA, Fontanini K, Hamilton JA, Pin JP, Shields DC, Spek CA, Sakmar TP, Kuliopulos A, Hunt III SW. Insider access: pepducin symposium explores a new approach to GPCR modulation. Ann N Y Acad Sci 2009; 1180 Suppl 1:E1-12. [DOI: 10.1111/j.1749-6632.2009.05326.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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91
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Milan-Lobo L, Gsandtner I, Gaubitzer E, Rünzler D, Buchmayer F, Köhler G, Bonci A, Freissmuth M, Sitte HH. Subtype-specific differences in corticotropin-releasing factor receptor complexes detected by fluorescence spectroscopy. Mol Pharmacol 2009; 76:1196-210. [PMID: 19755522 DOI: 10.1124/mol.109.059139] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G protein-coupled receptors have been proposed to exist in signalosomes subject to agonist-driven shifts in the assembly disassembly equilibrium, affected by stabilizing membrane lipids and/or cortical actin restricting mobility. We investigated the highly homologous corticotropin-releasing factor receptors (CRFRs), CRFR1 and -2, which are different within their hydrophobic core. Agonist stimulation of CRFR1 and CRFR2 gave rise to similar concentration-response curves for cAMP accumulation, but CRFR2 underwent restricted collision coupling. Both CRFR1 and CRFR2 formed constitutive oligomers at the cell surface and recruited beta-arrestin upon agonist activation (as assessed by fluorescence resonance energy transfer microscopy in living cells). However, CRFR2, but not CRFR1, failed to undergo agonist-induced internalization. Likewise, agonist binding accelerated the diffusion rate of CRFR2 only (detected by fluorescence recovery after photobleaching and fluorescence correlation spectroscopy) but reduced the mobile fraction, which is indicative of local confinement. Fluorescence intensity distribution analysis demonstrated that the size of CRFR complexes was not changed. Disruption of the actin cytoskeleton abolished the agonist-dependent increase in CRFR2 mobility, shifted the agonist concentration curve for CRFR2 to the left, and promoted agonist-induced internalization of CRFR2. Our observations are incompatible with an agonist-induced change in monomer-oligomer equilibrium, but they suggest an agonist-induced redistribution of CRFR2 into a membrane microdomain that affords rapid diffusion but restricted mobility and that is stabilized by the actin cytoskeleton. Our data show that membrane anisotropy can determine the shape and duration of receptor-generated signals in a subtype-specific manner.
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Affiliation(s)
- Laura Milan-Lobo
- Medical University of Vienna, Center for Biomolecular Medicine and Pharmacology, Institute of Pharmacology, Waehringerstrasse 13a, A-1090 Vienna, Austria
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92
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Pin JP, Comps-Agrar L, Maurel D, Monnier C, Rives ML, Trinquet E, Kniazeff J, Rondard P, Prézeau L. G-protein-coupled receptor oligomers: two or more for what? Lessons from mGlu and GABAB receptors. J Physiol 2009; 587:5337-44. [PMID: 19723778 DOI: 10.1113/jphysiol.2009.179978] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) are key players in the precise tuning of intercellullar communication. In the brain, both major neurotransmitters, glutamate and GABA, act on specific GPCRs [the metabotropic glutamate (mGlu) and GABA(B) receptors] to modulate synaptic transmission. These receptors are encoded by the largest gene family, and have been found to associate into both homo- and hetero-oligomers, which increases the complexity of this cell communication system. Here we show that dimerization is required for mGlu and GABA(B) receptors to function, since the activation process requires a relative movement between the subunits to occur. We will also show that, in contrast to the mGlu receptors, which form strict dimers, the GABA(B) receptors assemble into larger complexes, both in transfected cells and in the brain, resulting in a decreased G-protein coupling efficacy. We propose that GABA(B) receptor oligomerization offers a way to increase the possibility of modulating receptor signalling and activity, allowing the same receptor protein to have specific properties in neurons at different locations.
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Affiliation(s)
- J-P Pin
- Institut de Genomique Fonctionnelle, Département de Pharmacologie Moléculaire, CNRS UMR5203, INSERM U661, University of Montpellier 1 and 2, Montpellier, France.
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93
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Allosteric communication between protomers of dopamine class A GPCR dimers modulates activation. Nat Chem Biol 2009; 5:688-95. [PMID: 19648932 PMCID: PMC2817978 DOI: 10.1038/nchembio.199] [Citation(s) in RCA: 285] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Accepted: 04/28/2009] [Indexed: 01/09/2023]
Abstract
A major obstacle to understanding the functional importance of dimerization between Class A G protein-coupled receptors (GPCRs) has been the methodological limitation in achieving control of the identity of the components comprising the signaling unit. We have developed a functional complementation assay that enables such control and illustrate it for the human dopamine D2 receptor. The minimal signaling unit, two receptors and a single G protein, is maximally activated by agonist binding to a single protomer, which suggests an asymmetrical activated dimer. Inverse agonist binding to the second protomer enhances signaling, whereas agonist binding to the second protomer blunts signaling. Ligand-independent constitutive activation of the second protomer also inhibits signaling. Thus, GPCR dimer function can be modulated by the activity state of the second protomer, which for a heterodimer may be altered in pathological states. Our novel methodology also makes possible the characterization of signaling from a defined heterodimer unit.
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94
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Abstract
The GABA(B) receptors belong to the family of class C metabotropic receptors. They are inhibitory receptors forming obligatory heterodimers. Their analgesic role in the dorsal horn of the spinal cord is well established since more than 25 years ago. However, Baclofen, the reference agonist of the GABA(B) receptor, proved to have little efficiency in clinics in neuropathic patients. It seems therefore useful to decipher GABA(B) functions in the nociceptive circuitry, and their regulation in conditions of chronic pain. In the present review, we will focus first on the distribution of the GABA(B) subtypes. Then, we will consider their pre- and post-synaptic functions in the dorsal horn of naïve rats. Finally, we will document the mechanisms that may lead to receptor impairment in neuropathic conditions.
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Affiliation(s)
- Marc Landry
- Université Bordeaux 2, INSERM U862, 146 rue Léo Saignat, 33077 Bordeaux Cedex, France.
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95
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Ferraguti F, Crepaldi L, Nicoletti F. Metabotropic glutamate 1 receptor: current concepts and perspectives. Pharmacol Rev 2009; 60:536-81. [PMID: 19112153 DOI: 10.1124/pr.108.000166] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Almost 25 years after the first report that glutamate can activate receptors coupled to heterotrimeric G-proteins, tremendous progress has been made in the field of metabotropic glutamate receptors. Now, eight members of this family of glutamate receptors, encoded by eight different genes that share distinctive structural features have been identified. The first cloned receptor, the metabotropic glutamate (mGlu) receptor mGlu1 has probably been the most extensively studied mGlu receptor, and in many respects it represents a prototypical subtype for this family of receptors. Its biochemical, anatomical, physiological, and pharmacological characteristics have been intensely investigated. Together with subtype 5, mGlu1 receptors constitute a subgroup of receptors that couple to phospholipase C and mobilize Ca(2+) from intracellular stores. Several alternatively spliced variants of mGlu1 receptors, which differ primarily in the length of their C-terminal domain and anatomical localization, have been reported. Use of a number of genetic approaches and the recent development of selective antagonists have provided a means for clarifying the role played by this receptor in a number of neuronal systems. In this article we discuss recent advancements in the pharmacology and concepts about the intracellular transduction and pathophysiological role of mGlu1 receptors and review earlier data in view of these novel findings. The impact that this new and better understanding of the specific role of these receptors may have on novel treatment strategies for a variety of neurological and psychiatric disorders is considered.
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Affiliation(s)
- Francesco Ferraguti
- Department of Pharmacology, Innsbruck Medical University, Peter-Mayr Strasse 1a, Innsbruck A-6020, Austria.
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96
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Abstract
Glutamate and gamma-amino butyric acid (GABA) are respectively two major excitatory and inhibitory neurotransmitters of the adult mammalian central nervous system. These neurotransmitters exert their action through two types of receptors: ionotropic and metabotropic receptors. While ionotropic receptors are ligand gated ion channels involved in fast synaptic transmission, metabotropic receptors belong to the superfamily of G-protein coupled receptors (GPCRs) and are responsible for the neuromodulatory effect of glutamate and GABA. Metabotropic glutamate receptors (mGluRs) and metabotropic GABA receptors (GABA-B) are present at different levels of the pain neuraxis where they regulate nociceptive transmission and pain. The present review will focus on the role of these receptors in the modulation of pain perception.
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97
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Estes A, Wong Y, Parker M, Sallee F, Balasubramaniam A, Parker S. Neuropeptide Y (NPY) Y2 receptors of rabbit kidney cortex are largely dimeric. ACTA ACUST UNITED AC 2008; 150:88-94. [DOI: 10.1016/j.regpep.2008.06.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 04/28/2008] [Accepted: 06/01/2008] [Indexed: 10/22/2022]
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98
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Rabiet MJ, Huet E, Boulay F. Complement component 5a receptor oligomerization and homologous receptor down-regulation. J Biol Chem 2008; 283:31038-46. [PMID: 18772131 DOI: 10.1074/jbc.m805260200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most G-protein-coupled receptors (GPCRs) form di(oligo)-meric structures that constitute signaling and trafficking units and might be essential for receptor functions. Cell responses to complement C5a receptor (C5aR) are tightly controlled by receptor desensitization and internalization. To examine the implication of dimerization in C5aR regulation, we generated an NH(2)-terminally modified C5aR mutant, unable to bind C5a, and a phosphorylation-deficient mutant. Neither an intact NH(2) terminus nor the presence of COOH-terminal phosphorylation sites appeared to be required for the formation of C5aR dimers. Upon C5a stimulation, mutant receptors did not internalize when individually expressed. C5a stimulation of cells that co-expressed wild type C5aR together with either unliganded or phosphorylation-deficient mutant resulted in co-internalization of mutant receptors with C5aR. Unliganded GPCRs can be cross-phosphorylated within a heterologous receptor dimer or by second messenger-activated kinases. C5a stimulation of (32)P-labeled cells that co-expressed the unliganded mutant with either C5aR or the phosphorylation-deficient mutant did not induce phosphorylation of the unliganded mutant. We can thus postulate that, in the case of C5aR, the stimulation and phosphorylation of one monomer is enough to lead to dimer internalization. The existence and functional implication of di(oligo)mer formation may be important for an accurate C5aR down-regulation in pathological conditions.
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Affiliation(s)
- Marie-Josèphe Rabiet
- Laboratoire Biochimie et Biophysique des Systèmes Intégrés, Grenoble F-38054, France.
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99
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Kumpost J, Syrova Z, Kulihova L, Frankova D, Bologna JC, Hlavackova V, Prezeau L, Kralikova M, Hruskova B, Pin JP, Blahos J. Surface expression of metabotropic glutamate receptor variants mGluR1a and mGluR1b in transfected HEK293 cells. Neuropharmacology 2008; 55:409-18. [PMID: 18627772 DOI: 10.1016/j.neuropharm.2008.06.073] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 06/16/2008] [Accepted: 06/18/2008] [Indexed: 12/21/2022]
Abstract
Class C G-protein coupled receptors form obligatory dimers. Metabotropic glutamate receptors (mGluRs) are found commonly as homodimers. Alternative splicing of mGluR1 gene results in vivo in the expression of a long variant mGluR1a and at least two short variants mGluR1b and d. The amino acid sequences diverge within their carboxyl-termini six amino acid residues following RRKK motif. This four basic residue sequence was shown to have pronounced impact on function and trafficking of the short variants, while for mGluR1a the long C-terminus reduces the effects caused by presence of the RRKK motif. Here we investigated consequences of interactions between long mGluR1a and short mGluR1b variants. Our results show that mGluR1a interferes with mGluR1b trafficking to the cell surface in HEK293 transfected cells. Expression of a mGlu1a mutant incapable of activating G-proteins with mGluR1b mutated in the glutamate binding site led to the formation of a functional heterodimer. Moreover, we show that swapping long mGluR1a and/or short mGluR1b C-termini with corresponding regions in chimerical GB1 and GB2 gamma-amino butyric acid b (GABAb) receptor subunits do not exclude heterodimerization. These data reveal that the C-terminal ends of mGluR1 do not control subunit association, such that mGluR1 dimers with two distinct C-termini can form and function properly.
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Affiliation(s)
- Jiri Kumpost
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
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100
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Damian M, Mary S, Martin A, Pin JP, Banères JL. G protein activation by the leukotriene B4 receptor dimer. Evidence for an absence of trans-activation. J Biol Chem 2008; 283:21084-92. [PMID: 18490452 DOI: 10.1074/jbc.m710419200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
There is compelling evidence that G protein-coupled receptors exist as homo- and heterodimers, but the way these assemblies function at the molecular level remains unclear. We used here the purified leukotriene B(4) receptor BLT1 stabilized in its dimeric state to analyze how a receptor dimer activates G proteins. For this, we produced heterodimers between the wild-type BLT1 and a BLT1/ALXR chimera. The latter is no longer activated by leukotriene B(4) but is still activated by ALXR agonists. In this heterodimer, agonist binding to either one of the two protomers induced asymmetric conformational changes within the receptor dimer. Of importance, no G protein activation was observed when using a dimer where the ligand-loaded protomer was not able to trigger GDP/GTP exchange due to specific mutations in its third intracellular loop, establishing that the conformation of the agonist-free protomer is not competent for G protein activation. Taken together, these data indicate that although ligand binding to one protomer in the heterodimer is associated with cross-conformational changes, a trans-activation mechanism where the ligand-free subunit would trigger GDP/GTP exchange cannot be considered in this case for G protein activation. This observation sheds light into the way GPCR dimers, in particular heterodimers, could activate their cognate G proteins.
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Affiliation(s)
- Marjorie Damian
- Institut des Biomolécules Max Mousseron, CNRS UMR5247, Universités Montpellier 1 et 2, Montpellier, France
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