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Li Z, Chan KC, Nickels JD, Cheng X. Molecular Dynamics Refinement of Open State Serotonin 5-HT 3A Receptor Structures. J Chem Inf Model 2023; 63:1196-1207. [PMID: 36757760 DOI: 10.1021/acs.jcim.2c01441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Pentameric ligand-gated ion channels play an important role in mediating fast neurotransmissions. As a member of this receptor family, cation-selective 5-HT3 receptors are a clinical target for treating nausea and vomiting associated with chemotherapy and radiation therapy (Thompson and Lummis, 2006). Multiple cryo-electron microscopy (cryo-EM) structures of 5-HT3 receptors have been determined in distinct functional states (e.g., open, closed, etc.) (Basak et al., 2018; Basak et al., 2018; Polovinkin et al., 2018; Zhang et al., 2015). However, recent work has shown that the transmembrane pores of the open 5-HT3 receptor structures rapidly collapse and become artificially asymmetric in molecular dynamics (MD) simulations. To avoid this hydrophobic collapse, Dämgen and Biggin developed an equilibration protocol that led to a stable open state structure of the glycine receptor in MD simulations (Dämgen and Biggin, 2020). However, the protocol failed to yield open-like structures of the 5-HT3 receptor in our simulations. Here, we present a refined equilibration protocol that involves the rearrangement of the transmembrane helices to achieve stable open state structures of the 5-HT3 receptor that allow both water and ion permeation through the channel. Notably, channel gating is mediated through collective movement of the transmembrane helices, involving not only pore lining M2 helices but also their cross-talk with the adjacent M1 and M3 helices. Thus, the successful application of our refined equilibration protocol underscores the importance of the conformational coupling between the transmembrane helices in stabilizing open-like structures of the 5-HT3 receptor.
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Affiliation(s)
- Zoe Li
- Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy at The Ohio State University, Columbus, Ohio 43210, United States
| | - Kevin C Chan
- Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy at The Ohio State University, Columbus, Ohio 43210, United States
| | - Jonathan D Nickels
- Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Xiaolin Cheng
- Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy at The Ohio State University, Columbus, Ohio 43210, United States.,Translational Data Analytics Institute (TDAI) at The Ohio State University, Columbus, Ohio 43210, United States
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2
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Chen G, Shi Y, Shen X, Zhang Y, Lu X, Li Y, Jin C, Wang J, Wu J. Guard cell anion channel PbrSLAC1 regulates stomatal closure through PbrSnRK2.3 protein kinases. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2022; 325:111487. [PMID: 36209939 DOI: 10.1016/j.plantsci.2022.111487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 09/06/2022] [Accepted: 10/02/2022] [Indexed: 06/16/2023]
Abstract
Stomatal pores on the leaf surface are the gateways for gas exchange between plants and the atmosphere, which is regulated mainly by the S-type anion channel SLAC1. However, the gene encoding the main S-type anion channel SLAC1 in pear and its genetic characteristics remain unknown. In this study, Pbr015894.1 was identified as the candidate for PbrSLAC1 in pear, and it was found to be expressed abundantly in leaves, particularly in the guard cells. Virus-induced gene silencing experiments indicated that stomatal closure was achieved by a change in cell turgor instigated by PbrSLAC1 channel transport of NO3- in pear leaves and induced by abscisic acid. Furthermore, the expression of PbrSLAC1 in Arabidopsis slac1-3 and slac1-4 rescued the defective NO3- transport seen in these mutants, pointing to its role in anion transport. Fluorescence microscopy suggested that PbrSLAC1 was localized in the plasma membrane, and a dual-luciferase assay system demonstrated an interaction between PbrSLAC1 and PbrSnRK2.3/2.8. Moreover, anion conductance mediated by PbrSLAC1 was activated by PbrSnRK2.3 in Xenopus laevis oocytes and the channel showed greater permeability for nitrate than chloride, sulfate, or malate ions. Taken together, these results demonstrate that PbrSLAC1, an anion channel regulated by PbrSnRK2.3, is involved in stomatal closure by mediating the efflux of NO3- in pear leaf.
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Affiliation(s)
- Guodong Chen
- College of Life Science and Food Engineering, Huaiyin Institute of Technology, Huai'an 223003, China; Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China.
| | - Yunyong Shi
- College of Life Science and Food Engineering, Huaiyin Institute of Technology, Huai'an 223003, China
| | - Xue Shen
- College of Life Science and Food Engineering, Huaiyin Institute of Technology, Huai'an 223003, China
| | - Yanan Zhang
- College of Life Science and Food Engineering, Huaiyin Institute of Technology, Huai'an 223003, China
| | - Xiangyu Lu
- College of Life Science and Food Engineering, Huaiyin Institute of Technology, Huai'an 223003, China
| | - Yang Li
- College of Life Science and Food Engineering, Huaiyin Institute of Technology, Huai'an 223003, China
| | - Cong Jin
- College of Life Science and Food Engineering, Huaiyin Institute of Technology, Huai'an 223003, China
| | - Jizhong Wang
- College of Life Science and Food Engineering, Huaiyin Institute of Technology, Huai'an 223003, China
| | - Juyou Wu
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China.
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3
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Orädd F, Andersson M. Tracking Membrane Protein Dynamics in Real Time. J Membr Biol 2021; 254:51-64. [PMID: 33409541 PMCID: PMC7936944 DOI: 10.1007/s00232-020-00165-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 12/11/2020] [Indexed: 12/14/2022]
Abstract
Abstract Membrane proteins govern critical cellular processes and are central to human health and associated disease. Understanding of membrane protein function is obscured by the vast ranges of structural dynamics—both in the spatial and time regime—displayed in the protein and surrounding membrane. The membrane lipids have emerged as allosteric modulators of membrane protein function, which further adds to the complexity. In this review, we discuss several examples of membrane dependency. A particular focus is on how molecular dynamics (MD) simulation have aided to map membrane protein dynamics and how enhanced sampling methods can enable observing the otherwise inaccessible biological time scale. Also, time-resolved X-ray scattering in solution is highlighted as a powerful tool to track membrane protein dynamics, in particular when combined with MD simulation to identify transient intermediate states. Finally, we discuss future directions of how to further develop this promising approach to determine structural dynamics of both the protein and the surrounding lipids. Graphic Abstract ![]()
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Affiliation(s)
- Fredrik Orädd
- Department of Chemistry, Umeå University, Umeå, Sweden
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4
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Brodzki M, Michałowski MA, Gos M, Mozrzymas JW. Mutations of α 1F45 residue of GABA A receptor loop G reveal its involvement in agonist binding and channel opening/closing transitions. Biochem Pharmacol 2020; 177:113917. [PMID: 32194055 DOI: 10.1016/j.bcp.2020.113917] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 03/12/2020] [Indexed: 10/24/2022]
Abstract
GABAA receptors (GABAARs) mediate inhibitory neurotransmission in the mammalian brain. Recently, numerous GABAAR static structures have been published, but the molecular mechanisms of receptor activation remain elusive. Loop G is a rigid β-strand belonging to an extensive β-sheet that spans the regions involved in GABA binding and the interdomain interface which is important in receptor gating. It has been reported that loop G participates in ligand binding and gating of GABAARs, however, it remains unclear which specific gating transitions are controlled by this loop. Analysis of macroscopic responses revealed that mutation at the α1F45 residue (loop G midpoint) resulted in slower macroscopic desensitization and accelerated deactivation. Single-channel analysis revealed that these mutations also affected open and closed times distributions and reduced open probability. Kinetic modeling demonstrated that mutations affected primarily channel opening/closing and ligand binding with a minor effect on preactivation. Thus, α1F45 residue, in spite of its localization close to binding site, affects late gating transitions. In silico structural analysis suggested an important role of α1F45 residue in loop G stability and rigidity as well as in general structure of the binding site. We propose that the rigid β-sheet comprising loop G is well suited for long range communication within GABAAR but this mechanism becomes impaired when α1F45 is mutated. In conclusion, we demonstrate that loop G is crucial in controlling both binding and gating of GABAARs. These data shed new light on GABAAR activation mechanism and may also be helpful in designing clinically relevant modulators.
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Affiliation(s)
- Marek Brodzki
- University of Wrocław, Department of Molecular Physiology and Neurobiology, ul. Sienkiewicza 21, 50-335 Wrocław, Poland; Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland.
| | - Michał A Michałowski
- University of Wrocław, Department of Molecular Physiology and Neurobiology, ul. Sienkiewicza 21, 50-335 Wrocław, Poland; Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland.
| | - Michalina Gos
- University of Wrocław, Department of Molecular Physiology and Neurobiology, ul. Sienkiewicza 21, 50-335 Wrocław, Poland; Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Jerzy W Mozrzymas
- Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland.
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5
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Lev B, Allen TW. Simulating ion channel activation mechanisms using swarms of trajectories. J Comput Chem 2020; 41:387-401. [PMID: 31743478 DOI: 10.1002/jcc.26102] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 10/16/2019] [Accepted: 10/17/2019] [Indexed: 12/14/2022]
Abstract
Atomic-level studies of protein activity represent a significant challenge as a result of the complexity of conformational changes occurring on wide-ranging timescales, often greatly exceeding that of even the longest simulations. A prime example is the elucidation of protein allosteric mechanisms, where localized perturbations transmit throughout a large macromolecule to generate a response signal. For example, the conversion of chemical to electrical signals during synaptic neurotransmission in the brain is achieved by specialized membrane proteins called pentameric ligand-gated ion channels. Here, the binding of a neurotransmitter results in a global conformational change to open an ion-conducting pore across the nerve cell membrane. X-ray crystallography has produced static structures of the open and closed states of the proton-gated GLIC pentameric ligand-gated ion channel protein, allowing for atomistic simulations that can uncover changes related to activation. We discuss a range of enhanced sampling approaches that could be used to explore activation mechanisms. In particular, we describe recent application of an atomistic string method, based on Roux's "swarms of trajectories" approach, to elucidate the sequence and interdependence of conformational changes during activation. We illustrate how this can be combined with transition analysis and Brownian dynamics to extract thermodynamic and kinetic information, leading to understanding of what controls ion channel function. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Bogdan Lev
- School of Science, RMIT University, Melbourne, Victoria, 3000, Australia
| | - Toby W Allen
- School of Science, RMIT University, Melbourne, Victoria, 3000, Australia
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6
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Dämgen MA, Biggin PC. A Refined Open State of the Glycine Receptor Obtained via Molecular Dynamics Simulations. Structure 2020; 28:130-139.e2. [PMID: 31753620 PMCID: PMC6945115 DOI: 10.1016/j.str.2019.10.019] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 10/11/2019] [Accepted: 10/30/2019] [Indexed: 01/22/2023]
Abstract
Pentameric ligand-gated ion channels are key players in mediating fast neurotransmission. Glycine receptors are chloride-selective members of this receptor family that mediate inhibitory synaptic transmission and are implicated in neurological disorders including autism and hyperekplexia. They have been structurally characterized by both X-ray crystallography and cryoelectron microscopy (cryo-EM) studies, with the latter giving rise to what was proposed as a possible open state. However, recent work has questioned the physiological relevance of this open state structure, since it rapidly collapses in molecular dynamics simulations. Here, we show that the collapse can be avoided by a careful equilibration protocol that reconciles the more problematic regions of the original density map and gives a stable open state that shows frequent selective chloride permeation. The protocol developed in this work provides a means to refine open-like structures of the whole pentameric ligand-gated ion channel superfamily and reconciles the previous issues with the cryo-EM structure.
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Affiliation(s)
- Marc A Dämgen
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Philip C Biggin
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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7
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Oliveira ASF, Shoemark DK, Campello HR, Wonnacott S, Gallagher T, Sessions RB, Mulholland AJ. Identification of the Initial Steps in Signal Transduction in the α4β2 Nicotinic Receptor: Insights from Equilibrium and Nonequilibrium Simulations. Structure 2019; 27:1171-1183.e3. [PMID: 31130483 DOI: 10.1016/j.str.2019.04.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 01/28/2019] [Accepted: 04/10/2019] [Indexed: 02/02/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) modulate synaptic transmission in the nervous system. These receptors have emerged as therapeutic targets in drug discovery for treating several conditions, including Alzheimer's disease, pain, and nicotine addiction. In this in silico study, we use a combination of equilibrium and nonequilibrium molecular dynamics simulations to map dynamic and structural changes induced by nicotine in the human α4β2 nAChR. They reveal a striking pattern of communication between the extracellular binding pockets and the transmembrane domains (TMDs) and show the sequence of conformational changes associated with the initial steps in this process. We propose a general mechanism for signal transduction for Cys-loop receptors: the mechanistic steps for communication proceed firstly through loop C in the principal subunit, and are subsequently transmitted, gradually and cumulatively, to loop F of the complementary subunit, and then to the TMDs through the M2-M3 linker.
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Affiliation(s)
- A Sofia F Oliveira
- School of Biochemistry, University of Bristol, Bristol BS8 1DT, UK; Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
| | | | - Hugo Rego Campello
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
| | - Susan Wonnacott
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK
| | - Timothy Gallagher
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
| | | | - Adrian J Mulholland
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
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8
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Flood E, Boiteux C, Lev B, Vorobyov I, Allen TW. Atomistic Simulations of Membrane Ion Channel Conduction, Gating, and Modulation. Chem Rev 2019; 119:7737-7832. [DOI: 10.1021/acs.chemrev.8b00630] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Emelie Flood
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Céline Boiteux
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Bogdan Lev
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Igor Vorobyov
- Department of Physiology & Membrane Biology/Department of Pharmacology, University of California, Davis, 95616, United States
| | - Toby W. Allen
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
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9
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Wodak SJ, Paci E, Dokholyan NV, Berezovsky IN, Horovitz A, Li J, Hilser VJ, Bahar I, Karanicolas J, Stock G, Hamm P, Stote RH, Eberhardt J, Chebaro Y, Dejaegere A, Cecchini M, Changeux JP, Bolhuis PG, Vreede J, Faccioli P, Orioli S, Ravasio R, Yan L, Brito C, Wyart M, Gkeka P, Rivalta I, Palermo G, McCammon JA, Panecka-Hofman J, Wade RC, Di Pizio A, Niv MY, Nussinov R, Tsai CJ, Jang H, Padhorny D, Kozakov D, McLeish T. Allostery in Its Many Disguises: From Theory to Applications. Structure 2019; 27:566-578. [PMID: 30744993 PMCID: PMC6688844 DOI: 10.1016/j.str.2019.01.003] [Citation(s) in RCA: 234] [Impact Index Per Article: 46.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 11/29/2018] [Accepted: 01/02/2019] [Indexed: 12/19/2022]
Abstract
Allosteric regulation plays an important role in many biological processes, such as signal transduction, transcriptional regulation, and metabolism. Allostery is rooted in the fundamental physical properties of macromolecular systems, but its underlying mechanisms are still poorly understood. A collection of contributions to a recent interdisciplinary CECAM (Center Européen de Calcul Atomique et Moléculaire) workshop is used here to provide an overview of the progress and remaining limitations in the understanding of the mechanistic foundations of allostery gained from computational and experimental analyses of real protein systems and model systems. The main conceptual frameworks instrumental in driving the field are discussed. We illustrate the role of these frameworks in illuminating molecular mechanisms and explaining cellular processes, and describe some of their promising practical applications in engineering molecular sensors and informing drug design efforts.
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Affiliation(s)
| | | | - Nikolay V Dokholyan
- Department of Biochemistry & Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Departments of Pharmacology and Biochemistry & Molecular Biology, Penn State Medical Center, Hershey, PA, USA
| | - Igor N Berezovsky
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A(∗)STAR), and Department of Biological Sciences, National University of Singapore, Singapore, Singapore
| | - Amnon Horovitz
- Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Jing Li
- Departments of Biology and T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, USA
| | - Vincent J Hilser
- Departments of Biology and T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, USA
| | - Ivet Bahar
- School of Medicine, University of Pittsburgh, Pittsburgh, USA
| | | | - Gerhard Stock
- Biomolecular Dynamics, Institute of Physics, Albert Ludwigs University, Freiburg, Germany
| | - Peter Hamm
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Roland H Stote
- Department of Integrative Structural Biology, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
| | - Jerome Eberhardt
- Department of Integrative Structural Biology, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
| | - Yassmine Chebaro
- Department of Integrative Structural Biology, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
| | - Annick Dejaegere
- Department of Integrative Structural Biology, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
| | - Marco Cecchini
- Institut de Chimie de Strasbourg, UMR7177 CNRS & Université de Strasbourg, Strasbourg, France
| | | | - Peter G Bolhuis
- van 't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Amsterdam, Netherlands
| | - Jocelyne Vreede
- van 't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Amsterdam, Netherlands
| | - Pietro Faccioli
- Physics Department, Università di Trento and INFN-TIFPA, Trento, Italy
| | - Simone Orioli
- Physics Department, Università di Trento and INFN-TIFPA, Trento, Italy
| | - Riccardo Ravasio
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Le Yan
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA
| | - Carolina Brito
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS 91501-970, Brazil
| | - Matthieu Wyart
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Paraskevi Gkeka
- Structure Design and Informatics, Sanofi R&D, Chilly-Mazarin, France
| | - Ivan Rivalta
- École Normale Supérieure de Lyon, Université de Lyon, CNRS, Université Claude Bernard Lyon 1, Lyon, France
| | - Giulia Palermo
- Department of Chemistry and Biochemistry, University of California, San Diego, USA; Department of Bioengineering, University of California Riverside, CA 92507, USA
| | - J Andrew McCammon
- Department of Chemistry and Biochemistry, University of California, San Diego, USA
| | - Joanna Panecka-Hofman
- Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland
| | - Rebecca C Wade
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS) and Center for Molecular Biology (ZMBH), DKFZ-ZMBH Alliance, Heidelberg University, Heidelberg, Germany; Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, Heidelberg, Germany
| | - Antonella Di Pizio
- Leibniz-Institute for Food Systems Biology, Technical University of Munich, Munich, Germany
| | - Masha Y Niv
- Institute of Biochemistry, Food Science and Nutrition, Robert H Smith Faculty of Agriculture Food and Environment, The Hebrew University, Jerusalem, Israel
| | - Ruth Nussinov
- Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, USA; Sackler Institute of Molecular Medicine, Department of Human Genetics and Molecular Medicine Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Chung-Jung Tsai
- Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, USA
| | - Hyunbum Jang
- Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, USA
| | - Dzmitry Padhorny
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA
| | - Dima Kozakov
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA
| | - Tom McLeish
- Department of Physics, University of York, York, UK
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Wang Y, Bugge K, Kragelund BB, Lindorff-Larsen K. Role of protein dynamics in transmembrane receptor signalling. Curr Opin Struct Biol 2018; 48:74-82. [DOI: 10.1016/j.sbi.2017.10.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/16/2017] [Accepted: 10/19/2017] [Indexed: 10/18/2022]
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11
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Conformational landscapes of membrane proteins delineated by enhanced sampling molecular dynamics simulations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:909-926. [PMID: 29113819 DOI: 10.1016/j.bbamem.2017.10.033] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 10/24/2017] [Accepted: 10/28/2017] [Indexed: 11/22/2022]
Abstract
The expansion of computational power, better parameterization of force fields, and the development of novel algorithms to enhance the sampling of the free energy landscapes of proteins have allowed molecular dynamics (MD) simulations to become an indispensable tool to understand the function of biomolecules. The temporal and spatial resolution of MD simulations allows for the study of a vast number of processes of interest. Here, we review the computational efforts to uncover the conformational free energy landscapes of a subset of membrane proteins: ion channels, transporters and G-protein coupled receptors. We focus on the various enhanced sampling techniques used to study these questions, how the conclusions come together to build a coherent picture, and the relationship between simulation outcomes and experimental observables.
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12
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Un-gating and allosteric modulation of a pentameric ligand-gated ion channel captured by molecular dynamics. PLoS Comput Biol 2017; 13:e1005784. [PMID: 29069080 PMCID: PMC5673239 DOI: 10.1371/journal.pcbi.1005784] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 11/06/2017] [Accepted: 09/14/2017] [Indexed: 11/19/2022] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs) mediate intercellular communication at synapses through the opening of an ion pore in response to the binding of a neurotransmitter. Despite the increasing availability of high-resolution structures of pLGICs, a detailed understanding of the functional isomerization from closed to open (gating) and back is currently missing. Here, we provide the first atomistic description of the transition from open to closed (un-gating) in the glutamate-gated chloride channel (GluCl) from Caenorhabditis Elegans. Starting with the active-state structure solved in complex with the neurotransmitter L-glutamate and the positive allosteric modulator (PAM) ivermectin, we analyze the spontaneous relaxation of the channel upon removal of ivermectin by explicit solvent/membrane Molecular Dynamics (MD) simulations. The μs-long trajectories support the conclusion that ion-channel deactivation is mediated by two distinct quaternary transitions, i.e. a global receptor twisting followed by the radial expansion (or blooming) of the extracellular domain. At variance with previous models, we show that pore closing is exclusively regulated by the global twisting, which controls the position of the β1-β2 loop relative to the M2-M3 loop at the EC/TM domain interface. Additional simulations with L-glutamate restrained to the crystallographic binding mode and ivermectin removed indicate that the same twisting isomerization is regulated by agonist binding at the orthosteric site. These results provide a structural model for gating in pLGICs and suggest a plausible mechanism for the pharmacological action of PAMs in this neurotransmitter receptor family. The simulated un-gating converges to the X-ray structure of GluCl resting state both globally and locally, demonstrating the predictive character of state-of-art MD simulations.
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13
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Lev B, Murail S, Poitevin F, Cromer BA, Baaden M, Delarue M, Allen TW. String method solution of the gating pathways for a pentameric ligand-gated ion channel. Proc Natl Acad Sci U S A 2017; 114:E4158-E4167. [PMID: 28487483 PMCID: PMC5448215 DOI: 10.1073/pnas.1617567114] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Pentameric ligand-gated ion channels control synaptic neurotransmission by converting chemical signals into electrical signals. Agonist binding leads to rapid signal transduction via an allosteric mechanism, where global protein conformational changes open a pore across the nerve cell membrane. We use all-atom molecular dynamics with a swarm-based string method to solve for the minimum free-energy gating pathways of the proton-activated bacterial GLIC channel. We describe stable wetted/open and dewetted/closed states, and uncover conformational changes in the agonist-binding extracellular domain, ion-conducting transmembrane domain, and gating interface that control communication between these domains. Transition analysis is used to compute free-energy surfaces that suggest allosteric pathways; stabilization with pH; and intermediates, including states that facilitate channel closing in the presence of an agonist. We describe a switching mechanism that senses proton binding by marked reorganization of subunit interface, altering the packing of β-sheets to induce changes that lead to asynchronous pore-lining M2 helix movements. These results provide molecular details of GLIC gating and insight into the allosteric mechanisms for the superfamily of pentameric ligand-gated channels.
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Affiliation(s)
- Bogdan Lev
- School of Science, RMIT University, Melbourne, VIC 3001, Australia
| | - Samuel Murail
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Université Paris Diderot, Sorbonne Paris Cité, F-75005 Paris, France
| | - Frédéric Poitevin
- Department of Structural Biology, Stanford University, Stanford, CA 94305
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA 94025
| | - Brett A Cromer
- School of Science, RMIT University, Melbourne, VIC 3001, Australia
- School of Health and Biomedical Sciences, RMIT University, Bundoora, VIC 3083, Australia
| | - Marc Baaden
- Laboratoire de Biochimie Théorique, CNRS, UPR9080, Université Paris Diderot, Sorbonne Paris Cité, F-75005 Paris, France
| | - Marc Delarue
- Department of Structural Biology and Chemistry, Institut Pasteur and UMR 3528 du CNRS, F-75015 Paris, France
| | - Toby W Allen
- School of Science, RMIT University, Melbourne, VIC 3001, Australia;
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14
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Trick JL, Chelvaniththilan S, Klesse G, Aryal P, Wallace EJ, Tucker SJ, Sansom MSP. Functional Annotation of Ion Channel Structures by Molecular Simulation. Structure 2016; 24:2207-2216. [PMID: 27866853 PMCID: PMC5145807 DOI: 10.1016/j.str.2016.10.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2016] [Revised: 08/12/2016] [Accepted: 10/12/2016] [Indexed: 01/30/2023]
Abstract
Ion channels play key roles in cell membranes, and recent advances are yielding an increasing number of structures. However, their functional relevance is often unclear and better tools are required for their functional annotation. In sub-nanometer pores such as ion channels, hydrophobic gating has been shown to promote dewetting to produce a functionally closed (i.e., non-conductive) state. Using the serotonin receptor (5-HT3R) structure as an example, we demonstrate the use of molecular dynamics to aid the functional annotation of channel structures via simulation of the behavior of water within the pore. Three increasingly complex simulation analyses are described: water equilibrium densities; single-ion free-energy profiles; and computational electrophysiology. All three approaches correctly predict the 5-HT3R crystal structure to represent a functionally closed (i.e., non-conductive) state. We also illustrate the application of water equilibrium density simulations to annotate different conformational states of a glycine receptor.
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Affiliation(s)
- Jemma L Trick
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Sivapalan Chelvaniththilan
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Gianni Klesse
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Prafulla Aryal
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, UK
| | | | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, UK.
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15
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McCracken ML, Gorini G, McCracken LM, Mayfield RD, Harris RA, Trudell JR. Inter- and Intra-Subunit Butanol/Isoflurane Sites of Action in the Human Glycine Receptor. Front Mol Neurosci 2016; 9:45. [PMID: 27378846 PMCID: PMC4906044 DOI: 10.3389/fnmol.2016.00045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 05/26/2016] [Indexed: 11/24/2022] Open
Abstract
Glycine receptors (GlyRs) mediate inhibitory neurotransmission and are targets for alcohols and anesthetics in brain. GlyR transmembrane (TM) domains contain critical residues for alcohol/anesthetic action: amino acid A288 in TM3 forms crosslinks with TM1 (I229) in the adjacent subunit as well as TM2 (S267) and TM4 (Y406, W407, I409, Y410) in the same subunit. We hypothesized that these residues may participate in intra-subunit and inter-subunit sites of alcohol/anesthetic action. The following double and triple mutants of GLRA1 cDNA (encoding human glycine receptor alpha 1 subunit) were injected into Xenopus laevis oocytes: I229C/A288C, I229C/A288C/C290S, A288C/Y406C, A288C/W407C, A288C/I409C, and A288C/Y410C along with the corresponding single mutants and wild-type GLRA1. Butanol (22 mM) or isoflurane (0.6 mM) potentiation of GlyR-mediated currents before and after application of the cysteine crosslinking agent HgCl2 (10 μM) was measured using two-electrode voltage clamp electrophysiology. Crosslinking nearly abolished butanol and isoflurane potentiation in the I229C/A288C and I229C/A288C/C290S mutants but had no effect in single mutants or wild-type. Crosslinking also inhibited butanol and isoflurane potentiation in the TM3-4 mutants (A288C/Y406C, A288C/W407C, A288C/I409C, A288C/Y410C) with no effect in single mutants or wild-type. We extracted proteins from oocytes expressing I229C/288C, A288C/Y410C, or wild-type GlyRs, used mass spectrometry to verify their expression and possible inter-subunit dimerization, plus immunoblotting to investigate the biochemical features of proposed crosslinks. Wild-type GlyR subunits measured about 50 kDa; after crosslinking, the dimeric/monomeric 100:50 kDa band ratio was significantly increased in I229C/288C but not A288C/Y410C mutants or wild-type, providing support for TM1-3 inter-subunit and TM3-4 intra-subunit crosslinking. A GlyR homology model based on the GluCl template provides further evidence for a multi-site model for alcohol/anesthetic interaction with human GLRA1.
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Affiliation(s)
- Mandy L McCracken
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at AustinAustin, TX, USA; Integrative Neuroscience Research Branch, Neurobiology of Addiction Section, National Institute on Drug Abuse, National Institutes of HealthBaltimore, MD, USA
| | - Giorgio Gorini
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin Austin, TX, USA
| | - Lindsay M McCracken
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin Austin, TX, USA
| | - R Dayne Mayfield
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin Austin, TX, USA
| | - R Adron Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin Austin, TX, USA
| | - James R Trudell
- Department of Anesthesia and Beckman Program for Molecular and Genetic Medicine, Stanford School of Medicine Stanford, CA, USA
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16
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Heusser SA, Yoluk Ö, Klement G, Riederer EA, Lindahl E, Howard RJ. Functional characterization of neurotransmitter activation and modulation in a nematode model ligand-gated ion channel. J Neurochem 2016; 138:243-53. [PMID: 27102368 DOI: 10.1111/jnc.13644] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 03/21/2016] [Accepted: 04/07/2016] [Indexed: 11/29/2022]
Abstract
The superfamily of pentameric ligand-gated ion channels includes neurotransmitter receptors that mediate fast synaptic transmission in vertebrates, and are targets for drugs including alcohols, anesthetics, benzodiazepines, and anticonvulsants. However, the mechanisms of ion channel opening, gating, and modulation in these receptors leave many open questions, despite their pharmacological importance. Subtle conformational changes in both the extracellular and transmembrane domains are likely to influence channel opening, but have been difficult to characterize given the limited structural data available for human membrane proteins. Recent crystal structures of a modified Caenorhabditis elegans glutamate-gated chloride channel (GluCl) in multiple states offer an appealing model system for structure-function studies. However, the pharmacology of the crystallographic GluCl construct is not well established. To establish the functional relevance of this system, we used two-electrode voltage-clamp electrophysiology in Xenopus oocytes to characterize activation of crystallographic and native-like GluCl constructs by L-glutamate and ivermectin. We also tested modulation by ethanol and other anesthetic agents, and used site-directed mutagenesis to explore the role of a region of Loop F which was implicated in ligand gating by molecular dynamics simulations. Our findings indicate that the crystallographic construct functionally models concentration-dependent agonism and allosteric modulation of pharmacologically relevant receptors. Specific substitutions at residue Leu174 in loop F altered direct L-glutamate activation, consistent with computational evidence for this region's role in ligand binding. These insights demonstrate conservation of activation and modulation properties in this receptor family, and establish a framework for GluCl as a model system, including new possibilities for drug discovery. In this study, we elucidate the validity of a modified glutamate-gated chloride channel (GluClcryst ) as a structurally accessible model for GABAA receptors. In contrast to native-like controls, GluClcryst exhibits classical activation by its neurotransmitter ligand L-glutamate. The modified channel is also sensitive to allosteric modulators associated with human GABAA receptors, and to site-directed mutations predicted to alter channel opening.
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Affiliation(s)
- Stephanie A Heusser
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Özge Yoluk
- Swedish e-Science Research Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Göran Klement
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Erika A Riederer
- Department of Chemistry, Skidmore College, Saratoga Springs, NY, USA
| | - Erik Lindahl
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Stockholm, Sweden.,Swedish e-Science Research Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Rebecca J Howard
- Department of Chemistry, Skidmore College, Saratoga Springs, NY, USA
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