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Barreto CAV, Vitorino JNM, Reis PBPS, Machuqueiro M, Moreira IS. p Ka Calculations of GPCRs: Understanding Protonation States in Receptor Activation. J Chem Inf Model 2024; 64:6850-6856. [PMID: 39150719 PMCID: PMC11388449 DOI: 10.1021/acs.jcim.4c01125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
The increase in the available G protein-coupled receptor (GPCR) structures has been pivotal in helping to understand their activation process. However, the role of protonation-conformation coupling in GPCR activation still needs to be clarified. We studied the protonation behavior of the highly conserved Asp2.50 residue in five different class A GPCRs (active and inactive conformations) using a linear response approximation (LRA) pKa calculation protocol. We observed consistent differences (1.3 pK units) for the macroscopic pKa values between the inactive and active states of the A2AR and B2AR receptors, indicating the protonation of Asp2.50 during GPCR activation. This process seems to be specific and not conserved, as no differences were observed in the pKa values of the remaining receptors (CB1R, NT1R, and GHSR).
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Affiliation(s)
- Carlos A V Barreto
- PhD Programme in Experimental Biology and Biomedicine, Institute for Interdisciplinary Research (IIIUC), University of Coimbra, Casa Costa Alemão, 3030-789 Coimbra, Portugal
- CNC─Center for Neuroscience and Cell Biology, Center for Innovative Biomedicine and Biotechnology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - João N M Vitorino
- BioSI─Instituto de Biossistemas e Ciências Integrativas, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Pedro B P S Reis
- BioSI─Instituto de Biossistemas e Ciências Integrativas, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Miguel Machuqueiro
- BioSI─Instituto de Biossistemas e Ciências Integrativas, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Irina S Moreira
- CNC─Center for Neuroscience and Cell Biology, Center for Innovative Biomedicine and Biotechnology, University of Coimbra, 3004-504 Coimbra, Portugal
- Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
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2
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Geng S, Xu T, Sun Y. Genome-wide identification and analysis of chemokine receptor superfamily in miiuy croaker, Miichthys miiuy. FISH & SHELLFISH IMMUNOLOGY 2021; 118:343-353. [PMID: 34555531 DOI: 10.1016/j.fsi.2021.09.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 09/16/2021] [Accepted: 09/16/2021] [Indexed: 06/13/2023]
Abstract
The chemokine receptor (ChemR) superfamily, which is divided into 4 subfamilies (CXCR, CCR, XCR, and CX3CR), is the main receptors of chemokines in innate immune responses. In the current study, we have identified 27 ChemRs in miiuy croaker: 13 CCR genes, 11 CXCR genes, and 3 XCR genes. Multiple characteristics of these genes, including phylogeny, gene structures, conserved motifs, chromosome locations, evolutionary mechanism, and expression levels upon the bacterial challenge were analyzed. Gene structure and location analysis showed that all ChemR genes contain fewer introns (≤4) and they are unevenly distributed on the 12 chromosomes. And the XCR subfamily of miiuy croaker don't have the DRY motif of ChemR. Phylogenetic and synteny analysis showed that these genes experienced tandem and segmental duplication event in several species, and tandem duplication might be the main expansion way in miiuy croaker. The major ChemRs of each orthologous group in vertebrates were selected for molecular evolution analysis, the results of which indicated that compared with vertebrates, ChemRs of teleost fishes may have a relatively high evolutionary dynamic. In addition, a total of 21 positively selected codons were detected in vertebrate ChemRs under Model 8. RNA-Seq analysis and qRT-PCR verification demonstrated that CXCR3.2, CXCR5, and XCR1 genes were up-regulated significantly upon the Vibrio harveyi infection. These results provide valuable information for investigating the evolutionary relationships of chemokine receptor superfamily in miiuy croaker and laid the basis for further functional analysis.
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Affiliation(s)
- Shang Geng
- Laboratory of Fish Molecular Immunology, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China
| | - Tianjun Xu
- Laboratory of Fish Molecular Immunology, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China; Laboratory of Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; National Pathogen Collection Center for Aquatic Animals, Shanghai Ocean University, China
| | - Yuena Sun
- Laboratory of Fish Molecular Immunology, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, China; Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education, China.
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3
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Montpas N, St-Onge G, Nama N, Rhainds D, Benredjem B, Girard M, Hickson G, Pons V, Heveker N. Ligand-specific conformational transitions and intracellular transport are required for atypical chemokine receptor 3-mediated chemokine scavenging. J Biol Chem 2017; 293:893-905. [PMID: 29180449 PMCID: PMC5777261 DOI: 10.1074/jbc.m117.814947] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 11/20/2017] [Indexed: 11/06/2022] Open
Abstract
The atypical chemokine receptor ACKR3 contributes to chemotaxis by binding, internalizing, and degrading the chemokines CXCL11 and CXCL12 to shape and terminate chemotactic gradients during development and immune responses. Although unable to trigger G protein activation, both ligands activate G protein-independent ACKR3 responses and prompt arrestin recruitment. This offers a model to specifically study ligand-specific receptor conformations leading to G protein-independent signaling and to functional parameters such as receptor transport and chemokine degradation. We here show chemokine specificity in arrestin recruitment, by different effects of single amino acid substitutions in ACKR3 on arrestin in response to CXCL12 or CXCL11. Chemokine specificity in receptor transport was also observed, as CXCL11 induced faster receptor internalization, slower recycling, and longer intracellular sojourn of ACKR3 than CXCL12. Internalization and recycling rates of the ACKR3 R1423.50A substitution in response to each chemokine were similar; however, ACKR3 R1423.50A degraded only CXCL12 and not CXCL11. This suggests that ligand-specific intracellular receptor transport is required for chemokine degradation. Remarkably, the failure of ACKR3 R1423.50A to degrade CXCL11 was not caused by the lack of arrestin recruitment; rather, arrestin was entirely dispensable for scavenging of either chemokine. This suggests the involvement of another, yet unidentified, ACKR3 effector in scavenging. In summary, our study correlates ACKR3 ligand-specific conformational transitions with chemokine-dependent receptor transport dynamics and points toward unexpected ligand specificity in the mechanisms of chemokine degradation.
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Affiliation(s)
- Nicolas Montpas
- From the Department of Biochemistry and Molecular Medicine, University of Montréal, Montréal, Quebec H3T 1J4, Canada.,the Research Centre, Saint-Justine Hospital, University of Montréal, Montréal, Quebec H3T 1C5, Canada
| | - Geneviève St-Onge
- the Research Centre, Saint-Justine Hospital, University of Montréal, Montréal, Quebec H3T 1C5, Canada
| | - Nassr Nama
- From the Department of Biochemistry and Molecular Medicine, University of Montréal, Montréal, Quebec H3T 1J4, Canada.,the Research Centre, Saint-Justine Hospital, University of Montréal, Montréal, Quebec H3T 1C5, Canada
| | - David Rhainds
- From the Department of Biochemistry and Molecular Medicine, University of Montréal, Montréal, Quebec H3T 1J4, Canada.,the Research Centre, Saint-Justine Hospital, University of Montréal, Montréal, Quebec H3T 1C5, Canada
| | - Besma Benredjem
- From the Department of Biochemistry and Molecular Medicine, University of Montréal, Montréal, Quebec H3T 1J4, Canada.,the Research Centre, Saint-Justine Hospital, University of Montréal, Montréal, Quebec H3T 1C5, Canada
| | - Mélanie Girard
- From the Department of Biochemistry and Molecular Medicine, University of Montréal, Montréal, Quebec H3T 1J4, Canada.,the Research Centre, Saint-Justine Hospital, University of Montréal, Montréal, Quebec H3T 1C5, Canada
| | - Gilles Hickson
- the Research Centre, Saint-Justine Hospital, University of Montréal, Montréal, Quebec H3T 1C5, Canada.,the Department of Pathology and Cell Biology, University of Montréal, Montréal, Quebec H3T 1J4, Canada, and
| | - Véronique Pons
- INSERM, UMR 1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université de Toulouse, F-31432 Toulouse, France
| | - Nikolaus Heveker
- From the Department of Biochemistry and Molecular Medicine, University of Montréal, Montréal, Quebec H3T 1J4, Canada, .,the Research Centre, Saint-Justine Hospital, University of Montréal, Montréal, Quebec H3T 1C5, Canada
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4
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Castel H, Desrues L, Joubert JE, Tonon MC, Prézeau L, Chabbert M, Morin F, Gandolfo P. The G Protein-Coupled Receptor UT of the Neuropeptide Urotensin II Displays Structural and Functional Chemokine Features. Front Endocrinol (Lausanne) 2017; 8:76. [PMID: 28487672 PMCID: PMC5403833 DOI: 10.3389/fendo.2017.00076] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 03/28/2017] [Indexed: 12/16/2022] Open
Abstract
The urotensinergic system was previously considered as being linked to numerous physiopathological states, including atherosclerosis, heart failure, hypertension, pre-eclampsia, diabetes, renal disease, as well as brain vascular lesions. Thus, it turns out that the actions of the urotensin II (UII)/G protein-coupled receptor UT system in animal models are currently not predictive enough in regard to their effects in human clinical trials and that UII analogs, established to target UT, were not as beneficial as expected in pathological situations. Thus, many questions remain regarding the overall signaling profiles of UT leading to complex involvement in cardiovascular and inflammatory responses as well as cancer. We address the potential UT chemotactic structural and functional definition under an evolutionary angle, by the existence of a common conserved structural feature among chemokine receptorsopioïdergic receptors and UT, i.e., a specific proline position in the transmembrane domain-2 TM2 (P2.58) likely responsible for a kink helical structure that would play a key role in chemokine functions. Even if the last decade was devoted to the elucidation of the cardiovascular control by the urotensinergic system, we also attempt here to discuss the role of UII on inflammation and migration, likely providing a peptide chemokine status for UII. Indeed, our recent work established that activation of UT by a gradient concentration of UII recruits Gαi/o and Gα13 couplings in a spatiotemporal way, controlling key signaling events leading to chemotaxis. We think that this new vision of the urotensinergic system should help considering UT as a chemotactic therapeutic target in pathological situations involving cell chemoattraction.
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Affiliation(s)
- Hélène Castel
- Normandie University, UNIROUEN, INSERM, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine (IRIB), Rouen, France
- *Correspondence: Hélène Castel,
| | - Laurence Desrues
- Normandie University, UNIROUEN, INSERM, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine (IRIB), Rouen, France
| | - Jane-Eileen Joubert
- Normandie University, UNIROUEN, INSERM, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine (IRIB), Rouen, France
| | - Marie-Christine Tonon
- Normandie University, UNIROUEN, INSERM, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine (IRIB), Rouen, France
| | - Laurent Prézeau
- CNRS UMR 5203, INSERM U661, Institute of Functional Genomic (IGF), University of Montpellier 1 and 2, Montpellier, France
| | - Marie Chabbert
- UMR CNRS 6214, INSERM 1083, Faculté de Médecine 3, Angers, France
| | - Fabrice Morin
- Normandie University, UNIROUEN, INSERM, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine (IRIB), Rouen, France
| | - Pierrick Gandolfo
- Normandie University, UNIROUEN, INSERM, DC2N, Rouen, France
- Institute for Research and Innovation in Biomedicine (IRIB), Rouen, France
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5
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Lecointre C, Desrues L, Joubert JE, Perzo N, Guichet PO, Le Joncour V, Brulé C, Chabbert M, Leduc R, Prézeau L, Laquerrière A, Proust F, Gandolfo P, Morin F, Castel H. Signaling switch of the urotensin II vasosactive peptide GPCR: prototypic chemotaxic mechanism in glioma. Oncogene 2015; 34:5080-94. [PMID: 25597409 DOI: 10.1038/onc.2014.433] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 11/25/2014] [Accepted: 11/25/2014] [Indexed: 12/12/2022]
Abstract
Multiform glioblastomas (GBM) are the most frequent and aggressive primary brain tumors in adults. The poor prognosis is due to neo-angiogenesis and cellular invasion, processes that require complex chemotaxic mechanisms involving motility, migration and adhesion. Understanding these different cellular events implies identifying receptors and transduction pathways that lead to and promote either migration or adhesion. Here we establish that glioma express the vasoactive peptide urotensin II (UII) and its receptor UT and that UT-mediated signaling cascades are involved in glioma cell migration and adhesion. Components of the urotensinergic systems, UII and UT, are widely expressed in patient-derived GBM tissue sections, glioma cell lines and fresh biopsy explants. Interestingly, gradient concentrations of UII produced chemoattracting migratory/motility effects in glioma as well as HEK293 cells expressing human UT. These effects mainly involved the G13/Rho/rho kinase pathway while partially requiring Gi/o/PI3K components. In contrast, we observed that homogeneous concentrations of UII drastically blocked cell motility and stimulated cell-matrix adhesions through a UT/Gi/o signaling cascade, partially involving phosphatidylinositol-3 kinase. Finally, we provide evidence that, in glioma cells, homogeneous concentration of UII allowed translocation of Gα13 to the UT receptor at the plasma membrane and increased actin stress fibers, lamellipodia formation and vinculin-stained focal adhesions. UII also provoked a re-localization of UT precoupled to Gαi in filipodia and initiated integrin-stained focal points. Altogether, these findings suggest that UT behaves as a chemotaxic receptor, relaying a signaling switch between directional migration and cell adhesion under gradient or homogeneous concentrations, thereby redefining sequential mechanisms affecting tumor cells during glioma invasion. Taken together, our results allow us to propose a model in order to improve the design of compounds that demonstrate signaling bias for therapies that target specifically the Gi/o signaling pathway.
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Affiliation(s)
- C Lecointre
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - L Desrues
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - J E Joubert
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - N Perzo
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France.,Department of Pharmacology, Institut of Pharmacology, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - P-O Guichet
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - V Le Joncour
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - C Brulé
- Department of Pharmacology, Institut of Pharmacology, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada.,IGF, Institut of Functional Genomic, CNRS UMR 5203, Inserm U661, University of Montpellier 1 and 2, Montpellier, France
| | - M Chabbert
- UMR CNRS 6214, Inserm 1083, Faculté de Médecine 3, Angers, France
| | - R Leduc
- Department of Pharmacology, Institut of Pharmacology, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - L Prézeau
- IGF, Institut of Functional Genomic, CNRS UMR 5203, Inserm U661, University of Montpellier 1 and 2, Montpellier, France
| | - A Laquerrière
- Service of Anatomocytopathology, CHU of Rouen, ERI28 Inserm, IRIB, Rouen, France
| | - F Proust
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France.,Service of Neurosurgery, CHU of Rouen, Rouen, France
| | - P Gandolfo
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - F Morin
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
| | - H Castel
- Inserm U982, Laboratory of Neuronal and Neuroendocrine Communication and Differentiation, DC2N, Astrocyte and Vascular Niche, Biomedical Research Institute (IRIB), TC2N network, University of Rouen, Mont-Saint-Aignan, France
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6
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Ranganathan A, Dror RO, Carlsson J. Insights into the Role of Asp792.50 in β2 Adrenergic Receptor Activation from Molecular Dynamics Simulations. Biochemistry 2014; 53:7283-96. [DOI: 10.1021/bi5008723] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Anirudh Ranganathan
- Science for Life Laboratory, Box 1031, SE-171 21 Solna, Sweden
- Department
of Biochemistry and Biophysics and Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Ron O. Dror
- Department
of Computer Science, Department of Molecular and Cellular Physiology,
and Institute for Computational and Mathematical Engineering, Stanford University, Stanford, California 94305, United States
| | - Jens Carlsson
- Science for Life Laboratory, Box 1031, SE-171 21 Solna, Sweden
- Department
of Biochemistry and Biophysics and Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden
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7
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Sainsily X, Cabana J, Holleran BJ, Escher E, Lavigne P, Leduc R. Identification of transmembrane domain 1 & 2 residues that contribute to the formation of the ligand-binding pocket of the urotensin-II receptor. Biochem Pharmacol 2014; 92:280-8. [DOI: 10.1016/j.bcp.2014.08.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 08/20/2014] [Accepted: 08/21/2014] [Indexed: 11/15/2022]
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8
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Zhang XC, Cao C, Zhou Y, Zhao Y. Proton transfer-mediated GPCR activation. Protein Cell 2014; 6:12-7. [PMID: 25319942 PMCID: PMC4286134 DOI: 10.1007/s13238-014-0106-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 09/28/2014] [Indexed: 12/29/2022] Open
Abstract
G-protein coupled receptors (GPCRs) play essential roles in signal transduction from the environment into the cell. While many structural features have been elucidated in great detail, a common functional mechanism on how the ligand-binding signal is converted into a conformational change on the cytoplasmic face resulting in subsequent activation of downstream effectors remain to be established. Based on available structural and functional data of the activation process in class-A GPCRs, we propose here that a change in protonation status, together with proton transfer via conserved structural elements located in the transmembrane region, are the key elements essential for signal transduction across the membrane.
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Affiliation(s)
- Xuejun C Zhang
- National Laboratory of Macromolecules, National Center of Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China,
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9
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Shang Y, LeRouzic V, Schneider S, Bisignano P, Pasternak G, Filizola M. Mechanistic insights into the allosteric modulation of opioid receptors by sodium ions. Biochemistry 2014; 53:5140-9. [PMID: 25073009 PMCID: PMC4131901 DOI: 10.1021/bi5006915] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 07/21/2014] [Indexed: 01/09/2023]
Abstract
The idea of sodium ions altering G-protein-coupled receptor (GPCR) ligand binding and signaling was first suggested for opioid receptors (ORs) in the 1970s and subsequently extended to other GPCRs. Recently published ultra-high-resolution crystal structures of GPCRs, including that of the δ-OR subtype, have started to shed light on the mechanism underlying sodium control in GPCR signaling by revealing details of the sodium binding site. Whether sodium accesses different receptor subtypes from the extra- or intracellular sides, following similar or different pathways, is still an open question. Earlier experiments in brain homogenates suggested a differential sodium regulation of ligand binding to the three major OR subtypes, in spite of their high degree of sequence similarity. Intrigued by this possibility, we explored the dynamic nature of sodium binding to δ-OR, μ-OR, and κ-OR by means of microsecond-scale, all-atom molecular dynamics (MD) simulations. Rapid sodium permeation was observed exclusively from the extracellular milieu, and following similar binding pathways in all three ligand-free OR systems, notwithstanding extra densities of sodium observed near nonconserved residues of κ-OR and δ-OR, but not in μ-OR. We speculate that these differences may be responsible for the differential increase in antagonist binding affinity of μ-OR by sodium resulting from specific ligand binding experiments in transfected cells. On the other hand, sodium reduced the level of binding of subtype-specific agonists to all OR subtypes. Additional biased and unbiased MD simulations were conducted using the δ-OR ultra-high-resolution crystal structure as a model system to provide a mechanistic explanation for this experimental observation.
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MESH Headings
- Animals
- Binding Sites
- Crystallography, X-Ray
- Humans
- Ligands
- Mice
- Models, Molecular
- Molecular Dynamics Simulation
- Protein Conformation
- Radioligand Assay
- Receptors, Opioid/chemistry
- Receptors, Opioid/metabolism
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/chemistry
- Receptors, Opioid, delta/metabolism
- Receptors, Opioid, kappa/chemistry
- Receptors, Opioid, kappa/metabolism
- Receptors, Opioid, mu/chemistry
- Receptors, Opioid, mu/metabolism
- Sodium/metabolism
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Affiliation(s)
- Yi Shang
- Department
of Structural and Chemical Biology, Icahn
School of Medicine at Mount Sinai, New York, New York 10029, United States
| | - Valerie LeRouzic
- Molecular
Pharmacology and Chemistry Program, Memorial
Sloan-Kettering Cancer Center, New York, New York 10065, United States
| | - Sebastian Schneider
- Department
of Structural and Chemical Biology, Icahn
School of Medicine at Mount Sinai, New York, New York 10029, United States
| | - Paola Bisignano
- Department
of Structural and Chemical Biology, Icahn
School of Medicine at Mount Sinai, New York, New York 10029, United States
| | - Gavril
W. Pasternak
- Molecular
Pharmacology and Chemistry Program, Memorial
Sloan-Kettering Cancer Center, New York, New York 10065, United States
| | - Marta Filizola
- Department
of Structural and Chemical Biology, Icahn
School of Medicine at Mount Sinai, New York, New York 10029, United States
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10
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Desai AJ, Harikumar KG, Miller LJ. A type 1 cholecystokinin receptor mutant that mimics the dysfunction observed for wild type receptor in a high cholesterol environment. J Biol Chem 2014; 289:18314-26. [PMID: 24825903 DOI: 10.1074/jbc.m114.570200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Cholecystokinin (CCK) stimulates the type 1 CCK receptor (CCK1R) to elicit satiety after a meal. Agonists with this activity, although potentially useful for treatment of obesity, can also have side effects and toxicities of concern, making the development of an intrinsically inactive positive allosteric modulator quite attractive. Positive allosteric modulators also have the potential to correct the defective receptor-G protein coupling observed in the high membrane cholesterol environment described in metabolic syndrome. Current model systems to study CCK1R in such an environment are unstable and expensive to maintain. We now report that the Y140A mutation within a cholesterol-binding motif and the conserved, class A G protein-coupled receptor-specific (E/D)RY signature sequence results in ligand binding and activity characteristics similar to wild type CCK1R in a high cholesterol environment. This is true for natural CCK, as well as ligands with distinct chemistries and activity profiles. Additionally, the Y140A construct also behaved like CCK1R in high cholesterol in regard to its internalization, sensitivity to a nonhydrolyzable GTP analog, and anisotropy of a bound fluorescent CCK analog. Chimeric CCK1R/CCK2R constructs that systematically changed the residues in the allosteric ligand-binding pocket were studied in the presence of Y140A. This established increased importance of unique residues within TM3 and reduced the importance of TM2 for binding in the presence of this mutation, with the agonist trigger likely pulled away from its Leu(356) target on TM7. The distinct conformation of this intramembranous pocket within Y140A CCK1R provides an opportunity to normalize this by using a small molecule allosteric ligand, thereby providing safe and effective correction of the coupling defect in metabolic syndrome.
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Affiliation(s)
- Aditya J Desai
- From the Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, Arizona 85259
| | - Kaleeckal G Harikumar
- From the Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, Arizona 85259
| | - Laurence J Miller
- From the Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, Arizona 85259
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11
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Katritch V, Fenalti G, Abola EE, Roth BL, Cherezov V, Stevens RC. Allosteric sodium in class A GPCR signaling. Trends Biochem Sci 2014; 39:233-44. [PMID: 24767681 DOI: 10.1016/j.tibs.2014.03.002] [Citation(s) in RCA: 359] [Impact Index Per Article: 35.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 03/11/2014] [Accepted: 03/12/2014] [Indexed: 01/16/2023]
Abstract
Despite their functional and structural diversity, G-protein-coupled receptors (GPCRs) share a common mechanism of signal transduction via conformational changes in the seven-transmembrane (7TM) helical domain. New major insights into this mechanism come from the recent crystallographic discoveries of a partially hydrated sodium ion that is specifically bound in the middle of the 7TM bundle of multiple class A GPCRs. This review discusses the remarkable structural conservation and distinct features of the Na(+) pocket in this most populous GPCR class, as well as the conformational collapse of the pocket upon receptor activation. New insights help to explain allosteric effects of sodium on GPCR agonist binding and activation, and sodium's role as a potential co-factor in class A GPCR function.
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Affiliation(s)
- Vsevolod Katritch
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
| | - Gustavo Fenalti
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Enrique E Abola
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Bryan L Roth
- National Institute of Mental Health Psychoactive Drug Screening Program, Department of Pharmacology and Division of Chemical Biology and Medicinal Chemistry, University of North Carolina Chapel Hill Medical School, Chapel Hill, NC 27599, USA
| | - Vadim Cherezov
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Raymond C Stevens
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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12
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Miller-Gallacher JL, Nehmé R, Warne T, Edwards PC, Schertler GFX, Leslie AGW, Tate CG. The 2.1 Å resolution structure of cyanopindolol-bound β1-adrenoceptor identifies an intramembrane Na+ ion that stabilises the ligand-free receptor. PLoS One 2014; 9:e92727. [PMID: 24663151 PMCID: PMC3963952 DOI: 10.1371/journal.pone.0092727] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 02/25/2014] [Indexed: 12/30/2022] Open
Abstract
The β1-adrenoceptor (β1AR) is a G protein-coupled receptor (GPCR) that is activated by the endogenous agonists adrenaline and noradrenaline. We have determined the structure of an ultra-thermostable β1AR mutant bound to the weak partial agonist cyanopindolol to 2.1 Å resolution. High-quality crystals (100 μm plates) were grown in lipidic cubic phase without the assistance of a T4 lysozyme or BRIL fusion in cytoplasmic loop 3, which is commonly employed for GPCR crystallisation. An intramembrane Na+ ion was identified co-ordinated to Asp872.50, Ser1283.39 and 3 water molecules, which is part of a more extensive network of water molecules in a cavity formed between transmembrane helices 1, 2, 3, 6 and 7. Remarkably, this water network and Na+ ion is highly conserved between β1AR and the adenosine A2A receptor (rmsd of 0.3 Å), despite an overall rmsd of 2.4 Å for all Cα atoms and only 23% amino acid identity in the transmembrane regions. The affinity of agonist binding and nanobody Nb80 binding to β1AR is unaffected by Na+ ions, but the stability of the receptor is decreased by 7.5°C in the absence of Na+. Mutation of amino acid side chains that are involved in the co-ordination of either Na+ or water molecules in the network decreases the stability of β1AR by 5–10°C. The data suggest that the intramembrane Na+ and associated water network stabilise the ligand-free state of β1AR, but still permits the receptor to form the activated state which involves the collapse of the Na+ binding pocket on agonist binding.
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Affiliation(s)
| | - Rony Nehmé
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Tony Warne
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Patricia C. Edwards
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Gebhard F. X. Schertler
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Andrew G. W. Leslie
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Christopher G. Tate
- Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
- * E-mail:
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13
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Gutiérrez-de-Terán H, Massink A, Rodríguez D, Liu W, Han GW, Joseph JS, Katritch I, Heitman LH, Xia L, Ijzerman AP, Cherezov V, Katritch V, Stevens RC. The role of a sodium ion binding site in the allosteric modulation of the A(2A) adenosine G protein-coupled receptor. Structure 2013; 21:2175-85. [PMID: 24210756 DOI: 10.1016/j.str.2013.09.020] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 09/25/2013] [Accepted: 09/27/2013] [Indexed: 12/14/2022]
Abstract
The function of G protein-coupled receptors (GPCRs) can be modulated by a number of endogenous allosteric molecules. In this study, we used molecular dynamics, radioligand binding, and thermostability experiments to elucidate the role of the recently discovered sodium ion binding site in the allosteric modulation of the human A(2A) adenosine receptor, conserved among class A GPCRs. While the binding of antagonists and sodium ions to the receptor was noncompetitive in nature, the binding of agonists and sodium ions appears to require mutually exclusive conformational states of the receptor. Amiloride analogs can also bind to the sodium binding pocket, showing distinct patterns of agonist and antagonist modulation. These findings suggest that physiological concentrations of sodium ions affect functionally relevant conformational states of GPCRs and can help to design novel synthetic allosteric modulators or bitopic ligands exploiting the sodium ion binding pocket.
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Affiliation(s)
- Hugo Gutiérrez-de-Terán
- Fundación Pública Galega de Medicina Xenómica, Hospital Clínico Universitario de Santiago, E-15706 Santiago de Compostela, Spain; Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA; Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
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14
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Zhang XC, Sun K, Zhang L, Li X, Cao C. GPCR activation: protonation and membrane potential. Protein Cell 2013; 4:747-60. [PMID: 24057762 DOI: 10.1007/s13238-013-3073-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 09/11/2013] [Indexed: 12/22/2022] Open
Abstract
GPCR proteins represent the largest family of signaling membrane proteins in eukaryotic cells. Their importance to basic cell biology, human diseases, and pharmaceutical interventions is well established. Many crystal structures of GPCR proteins have been reported in both active and inactive conformations. These data indicate that agonist binding alone is not sufficient to trigger the conformational change of GPCRs necessary for binding of downstream G-proteins, yet other essential factors remain elusive. Based on analysis of available GPCR crystal structures, we identified a potential conformational switch around the conserved Asp2.50, which consistently shows distinct conformations between inactive and active states. Combining the structural information with the current literature, we propose an energy-coupling mechanism, in which the interaction between a charge change of the GPCR protein and the membrane potential of the living cell plays a key role for GPCR activation.
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Affiliation(s)
- Xuejun C Zhang
- National Laboratory of Macromolecules, National Center for Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China,
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15
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Desai AJ, Miller LJ. Sensitivity of cholecystokinin receptors to membrane cholesterol content. Front Endocrinol (Lausanne) 2012; 3:123. [PMID: 23087674 PMCID: PMC3475150 DOI: 10.3389/fendo.2012.00123] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Accepted: 10/01/2012] [Indexed: 12/18/2022] Open
Abstract
Cholesterol represents a structurally and functionally important component of the eukaryotic cell membrane, where it increases lipid order, affects permeability, and influences the lateral mobility and conformation of membrane proteins. Several G protein-coupled receptors have been shown to be affected by the cholesterol content of the membrane, with functional impact on their ligand binding and signal transduction characteristics. The effects of cholesterol can be mediated directly by specific molecular interactions with the receptor and/or indirectly by altering the physical properties of the membrane. This review focuses on the importance and differential effects of membrane cholesterol on the activity of cholecystokinin (CCK) receptors. The type 1 CCK receptor is quite sensitive to its cholesterol environment, while the type 2 CCK receptor is not. The possible structural basis for this differential impact is explored and the implications of pathological states, such as metabolic syndrome, in which membrane cholesterol may be increased and CCK1R function may be abnormal are discussed. This is believed to have substantial potential importance for the development of drugs targeting the CCK receptor.
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Affiliation(s)
| | - Laurence J. Miller
- *Correspondence: Laurence J. Miller, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 13400 E. Shea Blvd., Scottsdale, AZ 85259, USA. e-mail:
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16
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Potter RM, Harikumar KG, Wu SV, Miller LJ. Differential sensitivity of types 1 and 2 cholecystokinin receptors to membrane cholesterol. J Lipid Res 2011; 53:137-48. [PMID: 22021636 DOI: 10.1194/jlr.m020065] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recent studies indicate that membrane cholesterol can associate with G protein-coupled receptors (GPCRs) and affect their function. Previously, we reported that manipulation of membrane cholesterol affects ligand binding and signal transduction of the type 1 cholecystokinin receptor (CCK1R), a Class A GPCR. We now demonstrate that the closely related type 2 cholecystokinin receptor (CCK2R) does not share this cholesterol sensitivity. The sequences of both receptors reveal almost identical cholesterol interaction motifs in analogous locations in transmembrane segments two, three, four, and five. The disparity in cholesterol sensitivity between these receptors, despite their close structural relationship, provides a unique opportunity to define the possible structural basis of cholesterol sensitivity of CCK1R. To evaluate the relative contributions of different regions of CCK1R to cholesterol sensitivity, we performed ligand binding studies and biological activity assays of wild-type and CCK2R/CCK1R chimeric receptor-bearing Chinese hamster ovary cells after manipulation of membrane cholesterol. We also extended these studies to site-directed mutations within the cholesterol interaction motifs. The results contribute to a better understanding of the structural requirements for cholesterol sensitivity in CCK1R and provides insight into the function of other cholesterol-sensitive Class A GPCRs.
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Affiliation(s)
- Ross M Potter
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, USA
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17
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Singh N, Pydi SP, Upadhyaya J, Chelikani P. Structural basis of activation of bitter taste receptor T2R1 and comparison with Class A G-protein-coupled receptors (GPCRs). J Biol Chem 2011; 286:36032-36041. [PMID: 21852241 DOI: 10.1074/jbc.m111.246983] [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 human bitter taste receptors (T2Rs) are non-Class A members of the G-protein-coupled receptor (GPCR) superfamily, with very limited structural information. Amino acid sequence analysis reveals that most of the important motifs present in the transmembrane helices (TM1-TM7) of the well studied Class A GPCRs are absent in T2Rs, raising fundamental questions regarding the mechanisms of activation and how T2Rs recognize bitter ligands with diverse chemical structures. In this study, the bitter receptor T2R1 was used to systematically investigate the role of 15 transmembrane amino acids in T2Rs, including 13 highly conserved residues, by amino acid replacements guided by molecular modeling. Functional analysis of the mutants by calcium imaging analysis revealed that replacement of Asn-66(2.65) and the highly conserved Asn-24(1.50) resulted in greater than 90% loss of agonist-induced signaling. Our results show that Asn-24(1.50) plays a crucial role in receptor activation by mediating an hydrogen bond network connecting TM1-TM2-TM7, whereas Asn-66(2.65) is essential for binding to the agonist dextromethorphan. The interhelical hydrogen bond between Asn-24(1.50) and Arg-55(2.54) restrains T2R receptor activity because loss of this bond in I27A and R55A mutants results in hyperactive receptor. The conserved amino acids Leu-197(5.50), Ser-200(5.53), and Leu-201(5.54) form a putative LXXSL motif which performs predominantly a structural role by stabilizing the helical conformation of TM5 at the cytoplasmic end. This study provides for the first time mechanistic insights into the roles of the conserved transmembrane residues in T2Rs and allows comparison of the activation mechanisms of T2Rs with the Class A GPCRs.
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Affiliation(s)
- Nisha Singh
- Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba R3E 0W2, Canada
| | - Sai Prasad Pydi
- Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba R3E 0W2, Canada
| | - Jasbir Upadhyaya
- Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba R3E 0W2, Canada
| | - Prashen Chelikani
- Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba R3E 0W2, Canada.
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18
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A conserved protonation-induced switch can trigger "ionic-lock" formation in adrenergic receptors. J Mol Biol 2010; 397:1339-49. [PMID: 20132827 DOI: 10.1016/j.jmb.2010.01.060] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 01/19/2010] [Accepted: 01/25/2010] [Indexed: 11/23/2022]
Abstract
The mechanism of signal transduction in G-protein-coupled receptors (GPCRs) is a crucial step in cell signaling. However, the molecular details of this process are still largely undetermined. Carrying out submicrosecond molecular dynamics simulations of beta-adrenergic receptors, we found that cooperation between a number of highly conserved residues is crucial to alter the equilibrium between the active state and the inactive state of diffusible ligand GPCRs. In particular, "ionic-lock" formation in beta-adrenergic receptors is directly correlated with the protonation state of a highly conserved aspartic acid residue [Asp(2.50)] even though the two sites are located more than 20 A away from each other. Internal polar residues, acting as local microswitches, cooperate to propagate the signal from Asp(2.50) to the G-protein interaction site at the helix III-helix VI interface. Evolutionarily conserved differences between opsin and non-opsin GPCRs in the surrounding of Asp(2.50) influence the acidity of this residue and can thus help in rationalizing the differences in constitutive activity of class A GPCRs.
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19
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Vanni S, Neri M, Tavernelli I, Rothlisberger U. Observation of "ionic lock" formation in molecular dynamics simulations of wild-type beta 1 and beta 2 adrenergic receptors. Biochemistry 2009; 48:4789-97. [PMID: 19378975 DOI: 10.1021/bi900299f] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
G protein coupled receptors (GPCRs) are a large family of integral membrane proteins involved in signal transduction pathways, making them appealing drug targets for a wide spectrum of diseases. The recently crystallized structures of two engineered adrenergic receptors have opened new avenues for the understanding of the molecular mechanisms of action of GPCRs. Taking the two crystal structures as a starting point, we carried out submicrosecond molecular dynamics simulations of wild-type beta(1) and beta(2) adrenergic receptors in a lipid bilayer under physiological conditions. These simulations give access to structural and dynamic properties of the receptors in pseudo in vivo conditions. For both systems the overall fold properties of the transmembrane region as well as the binding pocket remain close to the crystal structure of the engineered systems, thus suggesting that the ligand binding mode is not affected by the introduced modifications. Both simulations indicate the presence of one or two internal water molecules absent in both crystal structures and essential for the stabilization of the binding pocket at the interface between transmembrane helices III, IV, and V. The different interactions arising from the substitution of Tyr308 in beta(2)AR into Phe325 in beta(1)AR induce different conformations of the homologous Asn(6.55) inside the binding pockets of the two receptors, suggesting a possible origin of receptor specificity in agonist binding. The equilibrated structures of both receptors recover all of the previously suggested features of inactive GPCRs including formation of a salt bridge between the cytoplasmatic moieties of helices III and VI ("ionic lock") that is absent in the crystal structures.
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Affiliation(s)
- Stefano Vanni
- Laboratory of Computational Chemistry and Biochemistry, Federal Institute of Technology, EPFL, CH-1015 Lausanne, Switzerland
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20
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Aizaki Y, Maruyama K, Nakano-Tetsuka M, Saito Y. Distinct roles of the DRY motif in rat melanin-concentrating hormone receptor 1 in signaling control. Peptides 2009; 30:974-81. [PMID: 19428776 DOI: 10.1016/j.peptides.2009.01.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2008] [Revised: 01/17/2009] [Accepted: 01/21/2009] [Indexed: 10/21/2022]
Abstract
Rhodopsin family (class A) G protein-coupled receptors possess common key residues or motifs that appear to be important for receptor function. To clarify the roles of the highly conserved amino acid triplet Asp(3.49)-Arg(3.50)-Tyr(3.51) (DRY motif), we examined how single-substitution mutations of the amino acids in the motif influenced specific features of rat melanin-concentrating hormone receptor 1 (MCH1R) activity. Substitution of either Asp140(3.49) or Tyr142(3.51) to Ala resulted in nonfunctional receptors, despite the retention of apparent potencies for agonist binding. These loss-of-function phenotypes may be caused by the lack of stimulation for GDP-GTP exchange observed in GTPgammaS-binding assays. On the other hand, substitution of Arg141(3.50) to Ala caused a 4-fold reduction in the agonist binding affinity and, concomitantly, a rightward shift of the dose-dependency curve for calcium mobilization and inhibition of cyclic AMP production. Although many experimental studies have suggested that the DRY motif is involved in maintaining the receptor in its ground state, none of the DRY motif substitutions to Ala in MCH1R led to constitutive activation, in terms of the basal signaling level for ERK1/2 activation or GTPgammaS binding. These data suggest that the major contribution of the DRY motif in MCH1R is to govern receptor conformation and G protein coupling/recognition.
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Affiliation(s)
- Yoshimi Aizaki
- Department of Pharmacology, Saitama Medical School of Medicine, Iruma-gun, Saitama, Japan
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21
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Domazet I, Holleran BJ, Martin SS, Lavigne P, Leduc R, Escher E, Guillemette G. The second transmembrane domain of the human type 1 angiotensin II receptor participates in the formation of the ligand binding pocket and undergoes integral pivoting movement during the process of receptor activation. J Biol Chem 2009; 284:11922-9. [PMID: 19276075 DOI: 10.1074/jbc.m808113200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The octapeptide hormone angiotensin II (AngII) exerts a wide variety of cardiovascular effects through the activation of the angiotensin II type-1 (AT(1)) receptor, which belongs to the G protein-coupled receptor superfamily. Like other G protein-coupled receptors, the AT(1) receptor possesses seven transmembrane domains that provide structural support for the formation of the ligand-binding pocket. In order to identify those residues in the second transmembrane domain (TMD2) that contribute to the formation of the binding pocket of the AT(1) receptor, we used the substituted cysteine accessibility method. All of the residues within the Leu-70 to Trp-94 region were mutated one at a time to a cysteine, and, after expression in COS-7 cells, the mutant receptors were treated with the sulfhydryl-specific alkylating agent methanethiosulfonate-ethylammonium (MTSEA). MTSEA reacts selectively with water-accessible, free sulfhydryl groups of endogenous or introduced point mutation cysteines. If a cysteine is found in the binding pocket, the covalent modification will affect the binding kinetics of the ligand. MTSEA substantially decreased the binding affinity of D74C-AT(1), L81C-AT(1), A85C-AT(1), T88C-AT(1), and A89C-AT(1) mutant receptors, which suggests that these residues orient themselves within the water-accessible binding pocket of the AT(1) receptor. Interestingly, this pattern of acquired MTSEA sensitivity was altered for TMD2 reporter cysteines engineered in a constitutively active N111G-AT(1) receptor background. Indeed, mutant D74C-N111G-AT(1) became insensitive to MTSEA, whereas mutant L81C-N111G-AT(1) lost some sensitivity and mutant V86C-N111G-AT(1) became sensitive to MTSEA. Our results suggest that constitutive activation of the AT(1) receptor causes TMD2 to pivot, bringing the top of TMD2 closer to the binding pocket and pushing the bottom of TMD2 away from the binding pocket.
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Affiliation(s)
- Ivana Domazet
- Department of Pharmacology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
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