51
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XFEL structures of the influenza M2 proton channel: Room temperature water networks and insights into proton conduction. Proc Natl Acad Sci U S A 2017; 114:13357-13362. [PMID: 28835537 DOI: 10.1073/pnas.1705624114] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The M2 proton channel of influenza A is a drug target that is essential for the reproduction of the flu virus. It is also a model system for the study of selective, unidirectional proton transport across a membrane. Ordered water molecules arranged in "wires" inside the channel pore have been proposed to play a role in both the conduction of protons to the four gating His37 residues and the stabilization of multiple positive charges within the channel. To visualize the solvent in the pore of the channel at room temperature while minimizing the effects of radiation damage, data were collected to a resolution of 1.4 Å using an X-ray free-electron laser (XFEL) at three different pH conditions: pH 5.5, pH 6.5, and pH 8.0. Data were collected on the Inwardopen state, which is an intermediate that accumulates at high protonation of the His37 tetrad. At pH 5.5, a continuous hydrogen-bonded network of water molecules spans the vertical length of the channel, consistent with a Grotthuss mechanism model for proton transport to the His37 tetrad. This ordered solvent at pH 5.5 could act to stabilize the positive charges that build up on the gating His37 tetrad during the proton conduction cycle. The number of ordered pore waters decreases at pH 6.5 and 8.0, where the Inwardopen state is less stable. These studies provide a graphical view of the response of water to a change in charge within a restricted channel environment.
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52
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Patch-Clamp Study of Hepatitis C p7 Channels Reveals Genotype-Specific Sensitivity to Inhibitors. Biophys J 2017; 110:2419-2429. [PMID: 27276260 DOI: 10.1016/j.bpj.2016.04.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 04/14/2016] [Indexed: 02/07/2023] Open
Abstract
Hepatitis C is a major worldwide disease and health hazard, affecting ∼3% of the world population. The p7 protein of hepatitis C virus (HCV) is an intracellular ion channel and pH regulator that is involved in the viral replication cycle. It is targeted by various classical ion channel blockers. Here, we generated p7 constructs corresponding to HCV genotypes 1a, 2a, 3a, and 4a for recombinant expression in HEK293 cells, and studied p7 channels using patch-clamp recording techniques. The pH50 values for recombinant p7 channels were between 6.0 and 6.5, as expected for proton-activated channels, and current-voltage dependence did not show any differences between genotypes. Inhibition of p7-mediated currents by amantadine, however, exhibited significant, genotype-specific variation. The IC50 values of p7-1a and p7-4a were 0.7 ± 0.1 nM and 3.2 ± 1.2 nM, whereas p7-2a and p7-3a had 50- to 1000-fold lower sensitivity, with IC50 values of 2402 ± 334 nM and 344 ± 64 nM, respectively. The IC50 values for rimantadine were low across all genotypes, ranging from 0.7 ± 0.1 nM, 1.6 ± 0.6 nM, and 3.0 ± 0.8 nM for p7-1a, p7-3a, and p7-4a, respectively, to 24 ± 4 nM for p7-2a. Results from patch-clamp recordings agreed well with cellular assays of p7 activity, namely, measurements of intracellular pH and hemadsorption assays, which confirmed the much reduced amantadine sensitivity of genotypes 2a and 3a. Thus, our results establish patch-clamp studies of recombinant viroporins as a valid analytical tool that can provide quantitative information about viroporin channel properties, complementing established techniques.
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53
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Abstract
The 97 amino acid bitopic membrane protein M2 of influenza A forms a tetrameric bundle in which two of the monomers are covalently linked via a cysteine bridge. In its tetrameric assembly the protein conducts protons across the viral envelope and within intracellular compartments during the infectivity cycle of the virus. A key residue in the translocation of the protons is His-37 which forms a planar tetrad in the configuration of the bundle accepting and translocating the incoming protons from the N terminal side, exterior of the virus, to the C terminal side, inside the virus. With experimentally available data from NMR spectroscopy of the transmembrane domains of the tetrameric M2 bundle classical MD simulations are conducted with the protein bundle in different protonation stages in respect to His-37. A full correlation analysis (FCA) of the data sets with the His-37 tetrad either in a fully four times unprotonated or protonated state, assumed to mimic high and low pH in vivo, respectively, in both cases reveal asymmetric backbone dynamics. His-37 side chain rotation dynamics is increased at full protonation of the tetrad compared to the dynamics in the fully unprotonated state. The data suggest that proton translocation can be achieved by decoupled side chain or backbone dynamics. Graphical abstract Visualization of the tetrameric bundle of the transmembrane domains of M2 of influenza A after 200 ns of MD simulations (upper left). The four histidine residues 37 are either not protonated as in M20 or fully protonated is in M24+. The asymmetric dynamics of the backbones are shown after a full correlation analysis (FCA) in blue (lower left). The rotational dynamics of the χ2 dihedral angles of the histidines in M20 (upper right) are less than those in M24+ (lower right).
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Affiliation(s)
- Monoj Mon Kalita
- Institute of Biophotonics and Biophotonics & Molecular Imaging Research Center (BMIRC), School of Biomedical Science and Engineering, National Yang-Ming University, 155, Li-Nong St., Sec. 2, Taipei, 112, Taiwan
| | - Wolfgang B Fischer
- Institute of Biophotonics and Biophotonics & Molecular Imaging Research Center (BMIRC), School of Biomedical Science and Engineering, National Yang-Ming University, 155, Li-Nong St., Sec. 2, Taipei, 112, Taiwan.
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54
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Structural Basis for Asymmetric Conductance of the Influenza M2 Proton Channel Investigated by Solid-State NMR Spectroscopy. J Mol Biol 2017; 429:2192-2210. [PMID: 28535993 DOI: 10.1016/j.jmb.2017.05.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 04/21/2017] [Accepted: 05/16/2017] [Indexed: 12/25/2022]
Abstract
The influenza M2 protein forms an acid-activated proton channel that is essential for virus replication. The transmembrane H37 selects for protons under low external pH while W41 ensures proton conduction only from the N terminus to the C terminus and prevents reverse current under low internal pH. Here, we address the molecular basis for this asymmetric conduction by investigating the structure and dynamics of a mutant channel, W41F, which permits reverse current under low internal pH. Solid-state NMR experiments show that W41F M2 retains the pH-dependent α-helical conformations and tetrameric structure of the wild-type (WT) channel but has significantly altered protonation and tautomeric equilibria at H37. At high pH, the H37 structure is shifted toward the π tautomer and less cationic tetrads, consistent with faster forward deprotonation to the C terminus. At low pH, the mutant channel contains more cationic tetrads than the WT channel, consistent with faster reverse protonation from the C terminus. 15N NMR spectra allow the extraction of four H37 pKas and show that the pKas are more clustered in the mutant channel compared to WT M2. Moreover, binding of the antiviral drug, amantadine, at the N-terminal pore at low pH did not convert all histidines to the neutral state, as seen in WT M2, but left half of all histidines cationic, unambiguously demonstrating C-terminal protonation of H37 in the mutant. These results indicate that asymmetric conduction in WT M2 is due to W41 inhibition of C-terminal acid activation by H37. When Trp is replaced by Phe, protons can be transferred to H37 bidirectionally with distinct rate constants.
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55
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Lin CW, Mensa B, Barniol-Xicota M, DeGrado WF, Gai F. Activation pH and Gating Dynamics of Influenza A M2 Proton Channel Revealed by Single-Molecule Spectroscopy. Angew Chem Int Ed Engl 2017; 56:5283-5287. [PMID: 28374543 PMCID: PMC5543805 DOI: 10.1002/anie.201701874] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Indexed: 12/17/2022]
Abstract
Because of its importance in viral replication, the M2 proton channel of the influenza A virus has been the focus of many studies. Although we now know a great deal about the structural architecture underlying its proton conduction function, we know little about its conformational dynamics, especially those controlling the rate of this action. Herein, we employ a single-molecule fluorescence method to assess the dynamics of the inter-helical channel motion of both full-length M2 and the transmembrane domain of M2. The rate of this motion depends not only on the identity of the channel and membrane composition but also on the pH in a sigmoidal manner. For the full-length M2 channel, the rate is increased from approximately 190 μs-1 at high pH to approximately 80 μs-1 at low pH, with a transition midpoint at pH 6.1. Because the latter value is within the range reported for the conducting pKa value of the His37 tetrad, we believe that this inter-helical motion accompanies proton conduction.
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Affiliation(s)
- Chun-Wei Lin
- Ultrafast Optical Processes Laboratory, Department of Chemistry, University of Pennsylvania, Philadelphia, 231 S. 34th Street, Philadelphia, PA, 19104, USA
| | - Bruk Mensa
- Department of Pharmaceutical Chemistry, University of California San Francisco, 600 16th Street, San Francisco, CA, 94158-2517, USA
| | - Marta Barniol-Xicota
- Department of Pharmaceutical Chemistry, University of California San Francisco, 600 16th Street, San Francisco, CA, 94158-2517, USA
| | - William F DeGrado
- Department of Pharmaceutical Chemistry, University of California San Francisco, 600 16th Street, San Francisco, CA, 94158-2517, USA
| | - Feng Gai
- Ultrafast Optical Processes Laboratory, Department of Chemistry, University of Pennsylvania, Philadelphia, 231 S. 34th Street, Philadelphia, PA, 19104, USA
- Department of Chemistry, University of Pennsylvania, Philadelphia, 231 S. 34th Street, Philadelphia, PA, 19104, USA
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56
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Lin CW, Mensa B, Barniol-Xicota M, DeGrado WF, Gai F. Activation pH and Gating Dynamics of Influenza A M2 Proton Channel Revealed by Single-Molecule Spectroscopy. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201701874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Chun-Wei Lin
- Ultrafast Optical Processes Laboratory; Department of Chemistry; University of Pennsylvania, Philadelphia; 231 S. 34th Street Philadelphia PA 19104 USA
| | - Bruk Mensa
- Department of Pharmaceutical Chemistry; University of California San Francisco; 600 16th Street San Francisco CA 94158-2517 USA
| | - Marta Barniol-Xicota
- Department of Pharmaceutical Chemistry; University of California San Francisco; 600 16th Street San Francisco CA 94158-2517 USA
| | - William F. DeGrado
- Department of Pharmaceutical Chemistry; University of California San Francisco; 600 16th Street San Francisco CA 94158-2517 USA
| | - Feng Gai
- Ultrafast Optical Processes Laboratory; Department of Chemistry; University of Pennsylvania, Philadelphia; 231 S. 34th Street Philadelphia PA 19104 USA
- Department of Chemistry; University of Pennsylvania, Philadelphia; 231 S. 34th Street Philadelphia PA 19104 USA
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57
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Tzitzoglaki C, Wright A, Freudenberger K, Hoffmann A, Tietjen I, Stylianakis I, Kolarov F, Fedida D, Schmidtke M, Gauglitz G, Cross TA, Kolocouris A. Binding and Proton Blockage by Amantadine Variants of the Influenza M2WT and M2S31N Explained. J Med Chem 2017; 60:1716-1733. [DOI: 10.1021/acs.jmedchem.6b01115] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Christina Tzitzoglaki
- Section
of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece
| | - Anna Wright
- Institute
of Molecular Biophysics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, United States
| | - Kathrin Freudenberger
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls Universität, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
| | - Anja Hoffmann
- Department
of Virology and Antiviral Therapy, Jena University Hospital, Hans Knoell Strasse 2, D-07745 Jena, Germany
| | - Ian Tietjen
- Department
of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Ioannis Stylianakis
- Section
of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece
| | - Felix Kolarov
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls Universität, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
| | - David Fedida
- Department
of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Michaela Schmidtke
- Department
of Virology and Antiviral Therapy, Jena University Hospital, Hans Knoell Strasse 2, D-07745 Jena, Germany
| | - Günter Gauglitz
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls Universität, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
| | - Timothy A. Cross
- Institute
of Molecular Biophysics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, United States
- Department
of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Antonios Kolocouris
- Section
of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece
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58
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Drakopoulos A, Tzitzoglaki C, Ma C, Freudenberger K, Hoffmann A, Hu Y, Gauglitz G, Schmidtke M, Wang J, Kolocouris A. Affinity of Rimantadine Enantiomers against Influenza A/M2 Protein Revisited. ACS Med Chem Lett 2017; 8:145-150. [PMID: 28217261 DOI: 10.1021/acsmedchemlett.6b00311] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 01/13/2017] [Indexed: 12/28/2022] Open
Abstract
Recent findings from solid state NMR (ssNMR) studies suggested that the (R)-enantiomer of rimantadine binds to the full M2 protein with higher affinity than the (S)-enantiomer. Intrigued by these findings, we applied functional assays, such as antiviral assay and electrophysiology (EP), to evaluate the binding affinity of rimantadine enantiomers to the M2 protein channel. Unexpectedly, no significant difference was found between the two enantiomers. Our experimental data based on the full M2 protein function were further supported by alchemical free energy calculations and isothermal titration calorimetry (ITC) allowing an evaluation of the binding affinity of rimantadine enantiomers to the M2TM pore. Both enantiomers have similar channel blockage, affinity, and antiviral potency.
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Affiliation(s)
- Antonios Drakopoulos
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
| | - Christina Tzitzoglaki
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
| | - Chulong Ma
- Department
of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, United States
| | - Kathrin Freudenberger
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Anja Hoffmann
- Department
of Virology and Antiviral Therapy, Jena University Hospital, Hans Knoell Str. 2, D-07745 Jena, Germany
| | - Yanmei Hu
- Department
of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, United States
| | - Günter Gauglitz
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Michaela Schmidtke
- Department
of Virology and Antiviral Therapy, Jena University Hospital, Hans Knoell Str. 2, D-07745 Jena, Germany
| | - Jun Wang
- Department
of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, United States
| | - Antonios Kolocouris
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
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59
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Abstract
At every step of their replication cycle influenza viruses depend heavily on their host cells. The multifaceted interactions that occur between the virus and its host cell determine the outcome of the infection, including efficiency of progeny virus production, tropism, and pathogenicity. In order to understand viral disease and develop therapies for influenza it is therefore pertinent to study the intricate interplay between influenza viruses and their required host factors. Here, we review the current knowledge on host cell factors required by influenza virus at the different stages of the viral replication cycle. We also discuss the roles of host factors in zoonotic transmission of influenza viruses and their potential for developing novel antivirals.
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60
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Llabrés S, Juárez-Jiménez J, Masetti M, Leiva R, Vázquez S, Gazzarrini S, Moroni A, Cavalli A, Luque FJ. Mechanism of the Pseudoirreversible Binding of Amantadine to the M2 Proton Channel. J Am Chem Soc 2016; 138:15345-15358. [DOI: 10.1021/jacs.6b07096] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Salomé Llabrés
- Department
of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and
Food Sciences, and Institute of Biomedicine (IBUB), University of Barcelona, Avgda. Prat de la Riba 171, 08921 Santa Coloma de Gramenet, Spain
| | - Jordi Juárez-Jiménez
- Department
of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and
Food Sciences, and Institute of Biomedicine (IBUB), University of Barcelona, Avgda. Prat de la Riba 171, 08921 Santa Coloma de Gramenet, Spain
| | - Matteo Masetti
- Department
of Pharmacy and Biotecnology (FaBit), Alma Mater Studiorum, University of Bologna, via Belmeloro 6, 40126 Bologna, Italy
| | - Rosana Leiva
- Laboratori
de Química Farmacèutica (Unitat Associada al CSIC),
Facultat de Farmàcia i Ciències de l’Alimentació,
and Institute of Biomedicine (IBUB), Universitat de Barcelona, Av. Joan
XXIII 27-31, 08028 Barcelona, Spain
| | - Santiago Vázquez
- Laboratori
de Química Farmacèutica (Unitat Associada al CSIC),
Facultat de Farmàcia i Ciències de l’Alimentació,
and Institute of Biomedicine (IBUB), Universitat de Barcelona, Av. Joan
XXIII 27-31, 08028 Barcelona, Spain
| | - Sabrina Gazzarrini
- Department
of Biosciences and National Research Council (CNR) Biophysics Institute
(IBF), University of Milan, Via Celoria 26, 20133 Milan, Italy
| | - Anna Moroni
- Department
of Biosciences and National Research Council (CNR) Biophysics Institute
(IBF), University of Milan, Via Celoria 26, 20133 Milan, Italy
| | - Andrea Cavalli
- Department
of Pharmacy and Biotecnology (FaBit), Alma Mater Studiorum, University of Bologna, via Belmeloro 6, 40126 Bologna, Italy
- CompuNet, Istituto Italiano di Tecnologia (IIT), via Morego 30, 16163 Genova,Italy
| | - F. Javier Luque
- Department
of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and
Food Sciences, and Institute of Biomedicine (IBUB), University of Barcelona, Avgda. Prat de la Riba 171, 08921 Santa Coloma de Gramenet, Spain
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61
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Liang R, Swanson JMJ, Madsen JJ, Hong M, DeGrado WF, Voth GA. Acid activation mechanism of the influenza A M2 proton channel. Proc Natl Acad Sci U S A 2016; 113:E6955-E6964. [PMID: 27791184 PMCID: PMC5111692 DOI: 10.1073/pnas.1615471113] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The homotetrameric influenza A M2 channel (AM2) is an acid-activated proton channel responsible for the acidification of the influenza virus interior, an important step in the viral lifecycle. Four histidine residues (His37) in the center of the channel act as a pH sensor and proton selectivity filter. Despite intense study, the pH-dependent activation mechanism of the AM2 channel has to date not been completely understood at a molecular level. Herein we have used multiscale computer simulations to characterize (with explicit proton transport free energy profiles and their associated calculated conductances) the activation mechanism of AM2. All proton transfer steps involved in proton diffusion through the channel, including the protonation/deprotonation of His37, are explicitly considered using classical, quantum, and reactive molecular dynamics methods. The asymmetry of the proton transport free energy profile under high-pH conditions qualitatively explains the rectification behavior of AM2 (i.e., why the inward proton flux is allowed when the pH is low in viral exterior and high in viral interior, but outward proton flux is prohibited when the pH gradient is reversed). Also, in agreement with electrophysiological results, our simulations indicate that the C-terminal amphipathic helix does not significantly change the proton conduction mechanism in the AM2 transmembrane domain; the four transmembrane helices flanking the channel lumen alone seem to determine the proton conduction mechanism.
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Affiliation(s)
- Ruibin Liang
- Department of Chemistry, The University of Chicago, Chicago, IL 60637
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637
- James Franck Institute, The University of Chicago, Chicago, IL 60637
| | - Jessica M J Swanson
- Department of Chemistry, The University of Chicago, Chicago, IL 60637
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637
- James Franck Institute, The University of Chicago, Chicago, IL 60637
| | - Jesper J Madsen
- Department of Chemistry, The University of Chicago, Chicago, IL 60637
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637
- James Franck Institute, The University of Chicago, Chicago, IL 60637
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - William F DeGrado
- Department of Pharmaceutical Chemistry, University of San Francisco, San Francisco, CA 94158
| | - Gregory A Voth
- Department of Chemistry, The University of Chicago, Chicago, IL 60637;
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637
- James Franck Institute, The University of Chicago, Chicago, IL 60637
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62
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Kolpe A, Schepens B, Fiers W, Saelens X. M2-based influenza vaccines: recent advances and clinical potential. Expert Rev Vaccines 2016; 16:123-136. [DOI: 10.1080/14760584.2017.1240041] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Annasaheb Kolpe
- Medical Biotechnology Center, VIB, Ghent, B-9052, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
| | - Bert Schepens
- Medical Biotechnology Center, VIB, Ghent, B-9052, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
| | - Walter Fiers
- Medical Biotechnology Center, VIB, Ghent, B-9052, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
| | - Xavier Saelens
- Medical Biotechnology Center, VIB, Ghent, B-9052, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
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63
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Dudev T, Grauffel C, Lim C. Influence of the Selectivity Filter Properties on Proton Selectivity in the Influenza A M2 Channel. J Am Chem Soc 2016; 138:13038-13047. [DOI: 10.1021/jacs.6b08041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Todor Dudev
- Faculty
of Chemistry and Pharmacy, Sofia University, Sofia 1164, Bulgaria
- Institute
of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Cédric Grauffel
- Institute
of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Carmay Lim
- Institute
of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
- Department
of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan
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64
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Wang J, Li F, Ma C. Recent progress in designing inhibitors that target the drug-resistant M2 proton channels from the influenza A viruses. Biopolymers 2016; 104:291-309. [PMID: 25663018 DOI: 10.1002/bip.22623] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 01/24/2015] [Indexed: 12/15/2022]
Abstract
Influenza viruses are the causative agents for seasonal influenza, which results in thousands of deaths and millions of hospitalizations each year. Moreover, sporadic transmission of avian or swan influenza viruses to humans often leads to an influenza pandemic, as there is no preimmunity in the human body to fight against such novel strains. The metastable genome of the influenza viruses, coupled with the reassortment of different strains from a wide range of host origins, leads to the continuous evolution of the influenza virus diversity. Such characteristics of influenza viruses present a grand challenge in devising therapeutic strategies to combat influenza virus infection. This review summarizes recent progress in designing small molecule inhibitors that target the drug-resistant influenza A virus M2 proton channels and highlights the contribution of mechanistic studies of proton conductance to drug discovery. The lessons learned throughout the course of M2 drug discovery might provide insights for designing inhibitors that target other therapeutically important ion channels.
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Affiliation(s)
- Jun Wang
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ, 85721.,BIO5 Institute, University of Arizona, Tucson, AZ, 85721
| | - Fang Li
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ, 85721
| | - Chunlong Ma
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, AZ, 85721
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65
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Jalily PH, Eldstrom J, Miller SC, Kwan DC, Tai SSH, Chou D, Niikura M, Tietjen I, Fedida D. Mechanisms of Action of Novel Influenza A/M2 Viroporin Inhibitors Derived from Hexamethylene Amiloride. Mol Pharmacol 2016; 90:80-95. [PMID: 27193582 DOI: 10.1124/mol.115.102731] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 05/12/2016] [Indexed: 01/09/2023] Open
Abstract
The increasing prevalence of influenza viruses with resistance to approved antivirals highlights the need for new anti-influenza therapeutics. Here we describe the functional properties of hexamethylene amiloride (HMA)-derived compounds that inhibit the wild-type and adamantane-resistant forms of the influenza A M2 ion channel. For example, 6-(azepan-1-yl)-N-carbamimidoylnicotinamide ( 9: ) inhibits amantadine-sensitive M2 currents with 3- to 6-fold greater potency than amantadine or HMA (IC50 = 0.2 vs. 0.6 and 1.3 µM, respectively). Compound 9: competes with amantadine for M2 inhibition, and molecular docking simulations suggest that 9: binds at site(s) that overlap with amantadine binding. In addition, tert-butyl 4'-(carbamimidoylcarbamoyl)-2',3-dinitro-[1,1'-biphenyl]-4-carboxylate ( 27: ) acts both on adamantane-sensitive and a resistant M2 variant encoding a serine to asparagine 31 mutation (S31N) with improved efficacy over amantadine and HMA (IC50 = 0.6 µM and 4.4 µM, respectively). Whereas 9: inhibited in vitro replication of influenza virus encoding wild-type M2 (EC50 = 2.3 µM), both 27: and tert-butyl 4'-(carbamimidoylcarbamoyl)-2',3-dinitro-[1,1'-biphenyl]-4-carboxylate ( 26: ) preferentially inhibited viruses encoding M2(S31N) (respective EC50 = 18.0 and 1.5 µM). This finding indicates that HMA derivatives can be designed to inhibit viruses with resistance to amantadine. Our study highlights the potential of HMA derivatives as inhibitors of drug-resistant influenza M2 ion channels.
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Affiliation(s)
- Pouria H Jalily
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Jodene Eldstrom
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Scott C Miller
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Daniel C Kwan
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Sheldon S-H Tai
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Doug Chou
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Masahiro Niikura
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - Ian Tietjen
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver (P.H.J., J.E., S.C.M., D.C.K., D.C., I.T., D.F.), and Faculty of Health Sciences, Simon Fraser University, Burnaby (S.S.-H.T., M.N., I.T.), British Columbia, Canada
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Ioannidis H, Drakopoulos A, Tzitzoglaki C, Homeyer N, Kolarov F, Gkeka P, Freudenberger K, Liolios C, Gauglitz G, Cournia Z, Gohlke H, Kolocouris A. Alchemical Free Energy Calculations and Isothermal Titration Calorimetry Measurements of Aminoadamantanes Bound to the Closed State of Influenza A/M2TM. J Chem Inf Model 2016; 56:862-76. [DOI: 10.1021/acs.jcim.6b00079] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Harris Ioannidis
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, 15771 Athens, Greece
| | - Antonios Drakopoulos
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, 15771 Athens, Greece
| | - Christina Tzitzoglaki
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, 15771 Athens, Greece
| | - Nadine Homeyer
- Mathematisch-Naturwissenschaftliche
Fakultät, Institut für Pharmazeutische und Medizinische
Chemie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Felix Kolarov
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Paraskevi Gkeka
- Biomedical
Research Foundation, Academy of Athens, 11527 Athens, Greece
| | - Kathrin Freudenberger
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Christos Liolios
- Demokritos, National Center for Scientific Research, 15310 Athens, Greece
| | - Günter Gauglitz
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Zoe Cournia
- Biomedical
Research Foundation, Academy of Athens, 11527 Athens, Greece
| | - Holger Gohlke
- Mathematisch-Naturwissenschaftliche
Fakultät, Institut für Pharmazeutische und Medizinische
Chemie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Antonios Kolocouris
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, 15771 Athens, Greece
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67
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High-resolution structures of the M2 channel from influenza A virus reveal dynamic pathways for proton stabilization and transduction. Proc Natl Acad Sci U S A 2015; 112:14260-5. [PMID: 26578770 DOI: 10.1073/pnas.1518493112] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The matrix 2 (M2) protein from influenza A virus is a proton channel that uses His37 as a selectivity filter. Here we report high-resolution (1.10 Å) cryogenic crystallographic structures of the transmembrane domain of M2 at low and high pH. These structures reveal that waters within the pore form hydrogen-bonded networks or "water wires" spanning 17 Å from the channel entrance to His37. Pore-lining carbonyl groups are well situated to stabilize hydronium via second-shell interactions involving bridging water molecules. In addition, room temperature crystallographic structures indicate that water becomes increasingly fluid with increasing temperature and decreasing pH, despite the higher electrostatic field. Complementary molecular dynamics simulations reveal a collective switch of hydrogen bond orientations that can contribute to the directionality of proton flux as His37 is dynamically protonated and deprotonated in the conduction cycle.
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68
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Lee YN, Kim MC, Lee YT, Kim YJ, Kang SM. Mechanisms of Cross-protection by Influenza Virus M2-based Vaccines. Immune Netw 2015; 15:213-21. [PMID: 26557805 PMCID: PMC4637342 DOI: 10.4110/in.2015.15.5.213] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Revised: 08/25/2015] [Accepted: 09/10/2015] [Indexed: 01/06/2023] Open
Abstract
Current influenza virus vaccines are based on strain-specific surface glycoprotein hemagglutinin (HA) antigens and effective only when the predicted vaccine strains and circulating viruses are well-matched. The current strategy of influenza vaccination does not prevent the pandemic outbreaks and protection efficacy is reduced or ineffective if mutant strains emerge. It is of high priority to develop effective vaccines and vaccination strategies conferring a broad range of cross protection. The extracellular domain of M2 (M2e) is highly conserved among human influenza A viruses and has been utilized to develop new vaccines inducing cross protection against different subtypes of influenza A virus. However, immune mechanisms of cross protection by M2e-based vaccines still remain to be fully elucidated. Here, we review immune correlates and mechanisms conferring cross protection by M2e-based vaccines. Molecular and cellular immune components that are known to be involved in M2 immune-mediated protection include antibodies, B cells, T cells, alveolar macrophages, Fc receptors, complements, and natural killer cells. Better understanding of protective mechanisms by immune responses induced by M2e vaccination will help facilitate development of broadly cross protective vaccines against influenza A virus.
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Affiliation(s)
- Yu-Na Lee
- Center for Inflammation, Immunity & Infection, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, USA
| | - Min-Chul Kim
- Center for Inflammation, Immunity & Infection, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, USA. ; Animal and Plant Quarantine Agency, Anyang 14089, Korea
| | - Young-Tae Lee
- Center for Inflammation, Immunity & Infection, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, USA
| | - Yu-Jin Kim
- Center for Inflammation, Immunity & Infection, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, USA
| | - Sang-Moo Kang
- Center for Inflammation, Immunity & Infection, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, USA
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69
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Wei C, Pohorille A. M2 proton channel: toward a model of a primitive proton pump. ORIGINS LIFE EVOL B 2015; 45:241-8. [PMID: 25777465 DOI: 10.1007/s11084-015-9421-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 11/06/2014] [Indexed: 01/23/2023]
Abstract
Transmembrane proton transfer was essential to early cellular systems in order to transduce energy for metabolic functions. The reliable, efficient and controlled generation of proton gradients became possible only with the emergence of active proton pumps. On the basis of features shared by most modern proton pumps we identify the essential mechanistic steps in active proton transport. Further, we discuss the mechanism of action of a small, transmembrane M2 proton channel from influenza A virus as a model for proton transport in protocells. The M2 channel is a 94-residue long, α-helical tetramer that is activated at low pH and exhibits high selectivity and directionality. A shorter construct, built of transmembrane fragments that are only 24 amino acids in length, exhibits very similar proton transport properties. Molecular dynamics simulations on the microsecond time-scale carried out for the M2 channel provided atomic level details on the activation of the channel in response to protonation of the histidine residue, His37. The pathway of proton conduction is mediated by His37, which accepts and donates protons at different interconverting conformation states when pH is lower than 6.5. The Val27 and Trp41 gates and the salt bridge between Asp44 and Arg45 further enhance the directionality of proton transport. It is argued that the architecture and the mechanism of action similar to that found in the M2 channel might have been the perfect starting point for evolution towards the earliest proton pumps, indicating that active proton transport could have readily emerged from simple, passive proton channels.
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Affiliation(s)
- Chenyu Wei
- NASA Ames Research Center, Mail Stop 239-4, Moffett Field, CA, 94035, USA
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70
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Scott C, Griffin S. Viroporins: structure, function and potential as antiviral targets. J Gen Virol 2015; 96:2000-2027. [PMID: 26023149 DOI: 10.1099/vir.0.000201] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The channel-forming activity of a family of small, hydrophobic integral membrane proteins termed 'viroporins' is essential to the life cycles of an increasingly diverse range of RNA and DNA viruses, generating significant interest in targeting these proteins for antiviral development. Viroporins vary greatly in terms of their atomic structure and can perform multiple functions during the virus life cycle, including those distinct from their role as oligomeric membrane channels. Recent progress has seen an explosion in both the identification and understanding of many such proteins encoded by highly significant pathogens, yet the prototypic M2 proton channel of influenza A virus remains the only example of a viroporin with provenance as an antiviral drug target. This review attempts to summarize our current understanding of the channel-forming functions for key members of this growing family, including recent progress in structural studies and drug discovery research, as well as novel insights into the life cycles of many viruses revealed by a requirement for viroporin activity. Ultimately, given the successes of drugs targeting ion channels in other areas of medicine, unlocking the therapeutic potential of viroporins represents a valuable goal for many of the most significant viral challenges to human and animal health.
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Affiliation(s)
- Claire Scott
- Leeds Institute of Cancer & Pathology and Leeds CRUK Clinical Centre, Faculty of Medicine and Health, St James's University Hospital, University of Leeds, Beckett Street, Leeds LS9 7TF, UK
| | - Stephen Griffin
- Leeds Institute of Cancer & Pathology and Leeds CRUK Clinical Centre, Faculty of Medicine and Health, St James's University Hospital, University of Leeds, Beckett Street, Leeds LS9 7TF, UK
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71
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Carrara G, Saraiva N, Parsons M, Byrne B, Prole DL, Taylor CW, Smith GL. Golgi anti-apoptotic proteins are highly conserved ion channels that affect apoptosis and cell migration. J Biol Chem 2015; 290:11785-801. [PMID: 25713081 PMCID: PMC4416878 DOI: 10.1074/jbc.m115.637306] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Indexed: 12/03/2022] Open
Abstract
Golgi anti-apoptotic proteins (GAAPs) are multitransmembrane proteins that are expressed in the Golgi apparatus and are able to homo-oligomerize. They are highly conserved throughout eukaryotes and are present in some prokaryotes and orthopoxviruses. Within eukaryotes, GAAPs regulate the Ca2+ content of intracellular stores, inhibit apoptosis, and promote cell adhesion and migration. Data presented here demonstrate that purified viral GAAPs (vGAAPs) and human Bax inhibitor 1 form ion channels and that vGAAP from camelpox virus is selective for cations. Mutagenesis of vGAAP, including some residues conserved in the recently solved structure of a related bacterial protein, BsYetJ, altered the conductance (E207Q and D219N) and ion selectivity (E207Q) of the channel. Mutation of residue Glu-207 or -178 reduced the effects of GAAP on cell migration and adhesion without affecting protection from apoptosis. In contrast, mutation of Asp-219 abrogated the anti-apoptotic activity of GAAP but not its effects on cell migration and adhesion. These results demonstrate that GAAPs are ion channels and define residues that contribute to the ion-conducting pore and affect apoptosis, cell adhesion, and migration independently.
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Affiliation(s)
- Guia Carrara
- From the Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
| | - Nuno Saraiva
- From the Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
| | - Maddy Parsons
- the Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom
| | - Bernadette Byrne
- the Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, United Kingdom, and
| | - David L Prole
- the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom,
| | - Colin W Taylor
- the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom,
| | - Geoffrey L Smith
- From the Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom,
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72
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Gu R, Liu LA, Wei D. Drug inhibition and proton conduction mechanisms of the influenza a M2 proton channel. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 827:205-26. [PMID: 25387967 DOI: 10.1007/978-94-017-9245-5_13] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The influenza A virus matrix protein 2 (M2 protein) is a pH-regulated proton channel embedded in the viral membrane. Inhibition of the M2 proton channel has been used to treat influenza infections for decades due to the crucial role of this protein in viral infection and replication. However, the widely-used M2 inhibitors, amantadine and rimantadine, have gradually lost their efficiencies because of naturally-occurring drug resistant mutations. Therefore, investigation of the structure and function of the M2 proton channel will not only increase our understanding of this important biological system, but also lead to the design of novel and effective anti-influenza drugs. Despite the simplicity of the M2 molecular structure, the M2 channel is highly flexible and there have been controversies and arguments regarding the channel inhibition mechanism and the proton conduction mechanism. In this book chapter, we will first carefully review the experimental and computational studies of the two possible drug binding sites on the M2 protein and explain the mechanisms regarding how inhibitors prevent proton conduction. Then, we will summarize our recent molecular dynamics simulations of the drug-resistant mutant channels and propose mechanisms for drug resistance. Finally, we will discuss two existing proton conduction mechanisms and talk about the remaining questions regarding the proton-relay process through the channel. The studies reviewed here demonstrate how molecular modeling and simulations have complemented experimental work and helped us understand the M2 channel structure and function.
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Affiliation(s)
- Ruoxu Gu
- State Key Laboratory of Microbial Metabolism, College of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
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73
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Fast Atomic Charge Calculation for Implementation into a Polarizable Force Field and Application to an Ion Channel Protein. J CHEM-NY 2015. [DOI: 10.1155/2015/908204] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Polarization of atoms plays a substantial role in molecular interactions. Class I and II force fields mostly calculate with fixed atomic charges which can cause inadequate descriptions for highly charged molecules, for example, ion channels or metalloproteins. Changes in charge distributions can be included into molecular mechanics calculations by various methods. Here, we present a very fast computational quantum mechanical method, the Bond Polarization Theory (BPT). Atomic charges are obtained via a charge calculation method that depend on the 3D structure of the system in a similar way as atomic charges ofab initiocalculations. Different methods of population analysis and charge calculation methods and their dependence on the basis set were investigated. A refined parameterization yielded excellent correlation ofR=0.9967. The method was implemented in the force field COSMOS-NMR and applied to the histidine-tryptophan-complex of the transmembrane domain of the M2 protein channel of influenza A virus. Our calculations show that moderate changes of side chain torsion angleχ1and small variations ofχ2of Trp-41 are necessary to switch from the inactivated into the activated state; and a rough two-side jump model of His-37 is supported for proton gating in accordance with a flipping mechanism.
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74
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Abstract
Virus encoded ion channels, termed viroporins, are expressed by a diverse set of viruses and have been found to target nearly every host cell membrane and compartment, including endocytic/exocytic vesicles, ER, mitochondria, Golgi, and the plasma membrane. Viroporins are generally very small (<100 amino acids) integral membrane proteins that share common structure motifs (conserved cluster of basic residues adjacent to an amphipathic alpha-helix) but only limited sequence homology between viruses. Ion channel activity of viroporins is either required for replication or greatly enhances replication and pathogenesis. Channel characteristics have been investigated using standard electrophysiological techniques, including planar lipid bilayer, liposome patch clamp or whole-cell voltage clamp. In general, viroporins are voltage-independent non-specific monovalent cation channels, with the exception of the influenza A virus M2 channel that forms a highly specific proton channel due to a conserved HXXXW motif. Viroporin channel currents range between highly variable (‘burst-like’) fluctuations to well resolved unitary (‘square-top’) transitions, and emerging data indicates the quality of channel activity is influenced by many factors, including viroporin synthesis/solubilization, the lipid environment and the ionic composition of the buffers, as well as intrinsic differences between the viroporins themselves. Compounds that block viroporin channel activity are effective antiviral drugs both in vitro and in vivo. Surprisingly distinct viroporins are inhibited by the same compounds (e.g., amantadines and amiloride derivatives), despite wide sequence divergence, raising the possibility of broadly acting antiviral drugs that target viroporins. Electrophysiology of viroporins will continue to play a critical role in elucidating the functional roles viroporins play in pathogenesis and to develop new drugs to combat viroporin-encoding pathogens.
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Affiliation(s)
- Anne H. Delcour
- Dept. of Biology and Biochemistry, University of Houston, Houston, Texas USA
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75
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Dong H, Fiorin G, DeGrado WF, Klein ML. Proton release from the histidine-tetrad in the M2 channel of the influenza A virus. J Phys Chem B 2014; 118:12644-51. [PMID: 25317959 PMCID: PMC4226308 DOI: 10.1021/jp5102225] [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] [Indexed: 12/31/2022]
Abstract
![]()
The activity of the M2 proton channel
of the influenza A virus
is controlled by pH. The tautomeric state and conformation of His37,
a key residue in the M2 transmembrane four-helix bundle, controls
the gating of the channel. Previously, we compared the energetics
and dynamics of two alternative conformations of the doubly protonated
state at neutral pH, namely, a 4-fold symmetric “histidine-box”
and a 2-fold symmetric “dimer-of-dimers”, and proposed
a multiconfiguration model for this charge state. Here, we elaborate
this model by further studying configurations of the His37 tetrad
in the triply protonated state and its subsequent deprotonation via
quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD)
simulations, starting with the aforementioned configurations, to gain
information about proton release in a viral membrane environment.
Interestingly, the two configurations converge under acidic pH conditions.
Protons can be transferred from one charged His37 to a neighboring
water cluster at the C-terminal side of the channel when the Trp41
gate is open transiently. With limited backbone expansion, the free
energy barrier for proton release to the viral interior at low pH
is ∼6.5 kcal/mol in both models, which is much lower than at
either neutral pH or for an isolated His37 cluster without a membrane
environment. Our calculations also suggest that the M2 protein would
seem to exclude the entrance of anions into the central channel through
a special mechanism, due to the latter’s potential inhibitory
effect on proton conduction.
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Affiliation(s)
- Hao Dong
- Institute for Computational Molecular Science, Temple University , 1900 North 12th Street, Philadelphia, Pennsylvania 19122-6078, United States
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76
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DiFrancesco ML, Hansen UP, Thiel G, Moroni A, Schroeder I. Effect of cytosolic pH on inward currents reveals structural characteristics of the proton transport cycle in the influenza A protein M2 in cell-free membrane patches of Xenopus oocytes. PLoS One 2014; 9:e107406. [PMID: 25211283 PMCID: PMC4174909 DOI: 10.1371/journal.pone.0107406] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 08/17/2014] [Indexed: 01/01/2023] Open
Abstract
Transport activity through the mutant D44A of the M2 proton channel from influenza virus A was measured in excised inside-out macro-patches of Xenopus laevis oocytes at cytosolic pH values of 5.5, 7.5 and 8.2. The current-voltage relationships reveal some peculiarities: 1. "Transinhibition", i.e., instead of an increase of unidirectional outward current with increasing cytosolic H(+) concentration, a decrease of unidirectional inward current was found. 2. Strong inward rectification. 3. Exponential rise of current with negative potentials. In order to interpret these findings in molecular terms, different kinetic models have been tested. The transinhibition basically results from a strong binding of H(+) to a site in the pore, presumably His37. This assumption alone already provides inward rectification and exponential rise of the IV curves. However, it results in poor global fits of the IV curves, i.e., good fits were only obtained for cytosolic pH of 8.2, but not for 7.5. Assuming an additional transport step as e.g. caused by a constriction zone at Val27 resulted in a negligible improvement. In contrast, good global fits for cytosolic pH of 7.5 and 8.2 were immediately obtained with a cyclic model. A "recycling step" implies that the protein undergoes conformational changes (assigned to Trp41 and Val27) during transport which have to be reset before the next proton can be transported. The global fit failed at the low currents at pHcyt = 5.5, as expected from the interference of putative transport of other ions besides H(+). Alternatively, a regulatory effect of acidic cytosolic pH may be assumed which strongly modifies the rate constants of the transport cycle.
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Affiliation(s)
| | - Ulf-Peter Hansen
- Department of Structural Biology, University of Kiel, Kiel, Germany
| | - Gerhard Thiel
- Plant Membrane Biophysics, Technical University of Darmstadt, Darmstadt, Germany
| | - Anna Moroni
- Department of Biosciences and CNR-IBF, University of Milan, Milan, Italy
| | - Indra Schroeder
- Plant Membrane Biophysics, Technical University of Darmstadt, Darmstadt, Germany
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A Critical Role for Immune System Response in Mediating Anti-influenza Drug Synergies Assessed by Mechanistic Modeling. CPT-PHARMACOMETRICS & SYSTEMS PHARMACOLOGY 2014; 3:e135. [PMID: 25207611 PMCID: PMC4211263 DOI: 10.1038/psp.2014.32] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 06/10/2014] [Indexed: 11/17/2022]
Abstract
Influenza virus infections represent a serious public health problem worldwide, due to the rapid emergence of drug resistance. One strategy to improve treatment efficacy is to combine drugs that act synergistically. Potentially useful drug combinations are typically identified through empirical testing using in vitro and animal models, but the complexity of the clinical situation warrants the use of more careful analysis and sophisticated approaches. To explore new approaches, we constructed a mechanistic model representing the interaction of antiviral drugs with the viral replication pathway and human immune responses. Simulation of combination therapy using oseltamivir and amantadine predicted significant therapeutic synergy only when immune response was included, in agreement with previous in vitro and in vivo studies using amantadine-resistant strains. Our model can be used to predict the optimal doses for combination therapy, and also raises questions about current drug evaluation methods that do not account for immune system interactions.
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78
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Ghosh A, Wang J, Moroz YS, Korendovych IV, Zanni M, DeGrado WF, Gai F, Hochstrasser RM. 2D IR spectroscopy reveals the role of water in the binding of channel-blocking drugs to the influenza M2 channel. J Chem Phys 2014; 140:235105. [PMID: 24952572 PMCID: PMC4098053 DOI: 10.1063/1.4881188] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 05/21/2014] [Indexed: 12/21/2022] Open
Abstract
Water is an integral part of the homotetrameric M2 proton channel of the influenza A virus, which not only assists proton conduction but could also play an important role in stabilizing channel-blocking drugs. Herein, we employ two dimensional infrared (2D IR) spectroscopy and site-specific IR probes, i.e., the amide I bands arising from isotopically labeled Ala30 and Gly34 residues, to probe how binding of either rimantadine or 7,7-spiran amine affects the water dynamics inside the M2 channel. Our results show, at neutral pH where the channel is non-conducting, that drug binding leads to a significant increase in the mobility of the channel water. A similar trend is also observed at pH 5.0 although the difference becomes smaller. Taken together, these results indicate that the channel water facilitates drug binding by increasing its entropy. Furthermore, the 2D IR spectral signatures obtained for both probes under different conditions collectively support a binding mechanism whereby amantadine-like drugs dock in the channel with their ammonium moiety pointing toward the histidine residues and interacting with a nearby water cluster, as predicted by molecular dynamics simulations. We believe these findings have important implications for designing new anti-influenza drugs.
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Affiliation(s)
- Ayanjeet Ghosh
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Jun Wang
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143, USA
| | - Yurii S Moroz
- Department of Chemistry, Syracuse University, Syracuse, New York 13244, USA
| | - Ivan V Korendovych
- Department of Chemistry, Syracuse University, Syracuse, New York 13244, USA
| | - Martin Zanni
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - William F DeGrado
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143, USA
| | - Feng Gai
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Robin M Hochstrasser
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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79
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Wei C, Pohorille A. Activation and proton transport mechanism in influenza A M2 channel. Biophys J 2014; 105:2036-45. [PMID: 24209848 DOI: 10.1016/j.bpj.2013.08.030] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 07/09/2013] [Accepted: 08/08/2013] [Indexed: 12/23/2022] Open
Abstract
Molecular dynamics trajectories 2 μs in length have been generated for the pH-activated, tetrameric M2 proton channel of the influenza A virus in all protonation states of the pH sensor located at the His(37) tetrad. All simulated structures are in very good agreement with high-resolution structures. Changes in the channel caused by progressive protonation of His(37) provide insight into the mechanism of proton transport. The channel is closed at both His(37) and Trp(41) sites in the singly and doubly protonated states, but it opens at Trp(41) upon further protonation. Anions access the charged His(37) and by doing so stabilize the protonated states of the channel. The narrow opening at the His(37) site, further blocked by anions, is inconsistent with the water-wire mechanism of proton transport. Instead, conformational interconversions of His(37) correlated with hydrogen bonding to water molecules indicate that these residues shuttle protons in high-protonation states. Hydrogen bonds between charged and uncharged histidines are rare. The valve at Val(27) remains on average quite narrow in all protonation states but fluctuates sufficiently to support water and proton transport. A proton transport mechanism in which the channel, depending on pH, opens at either the histidine or valine gate is only partially supported by the simulations.
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Affiliation(s)
- Chenyu Wei
- NASA Ames Research Center, Moffett Field, California; Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California.
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80
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Kolocouris A, Tzitzoglaki C, Johnson FB, Zell R, Wright AK, Cross TA, Tietjen I, Fedida D, Busath DD. Aminoadamantanes with persistent in vitro efficacy against H1N1 (2009) influenza A. J Med Chem 2014; 57:4629-39. [PMID: 24793875 PMCID: PMC4127532 DOI: 10.1021/jm500598u] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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A series of 2-adamantanamines with
alkyl adducts of various lengths
were examined for efficacy against strains of influenza A including
those having an S31N mutation in M2 proton channel that confer resistance
to amantadine and rimantadine. The addition of as little as one CH2 group to the methyl adduct of the amantadine/rimantadine
analogue, 2-methyl-2-aminoadamantane, led to activity in vitro against
two M2 S31N viruses A/Calif/07/2009 (H1N1) and A/PR/8/34 (H1N1) but
not to a third A/WS/33 (H1N1). Solid state NMR of the transmembrane
domain (TMD) with a site mutation corresponding to S31N shows evidence
of drug binding. But electrophysiology using the full length S31N
M2 protein in HEK cells showed no blockade. A wild type strain, A/Hong
Kong/1/68 (H3N2) developed resistance to representative drugs within
one passage with mutations in M2 TMD, but A/Calif/07/2009 S31N was
slow (>8 passages) to develop resistance in vitro, and the resistant
virus had no mutations in M2 TMD. The results indicate that 2-alkyl-2-aminoadamantane
derivatives with sufficient adducts can persistently block p2009 influenza
A in vitro through an alternative mechanism. The observations of an
HA1 mutation, N160D, near the sialic acid binding site in both 6-resistant A/Calif/07/2009(H1N1) and the broadly resistant
A/WS/33(H1N1) and of an HA1 mutation, I325S, in the 6-resistant virus at a cell-culture stable site suggest that the drugs
tested here may block infection by direct binding near these critical
sites for virus entry to the host cell.
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Affiliation(s)
- Antonios Kolocouris
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens , Athens 15771, Greece
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81
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eGFP-pHsens as a highly sensitive fluorophore for cellular pH determination by fluorescence lifetime imaging microscopy (FLIM). BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1581-93. [PMID: 24742974 DOI: 10.1016/j.bbabio.2014.04.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Revised: 04/07/2014] [Accepted: 04/08/2014] [Indexed: 12/11/2022]
Abstract
The determination of pH in the cell cytoplasm or in intracellular organelles is of high relevance in cell biology. Also in plant cells, organelle-specific pH monitoring with high spatial precision is an important issue, since e.g. ΔpH across thylakoid membranes is the driving force for ATP synthesis critically regulating photoprotective mechanisms like non-photochemical quenching (NPQ) of chlorophyll (Chl) fluorescence or the xanthophyll cycle. In animal cells, pH determination can serve to monitor proton permeation across membranes and, therefore, to assay the efficiency of drugs against proton-selective transporters or ion channels. In this work, we demonstrate the applicability of the pH-sensitive GFP derivative (eGFP-pHsens, originally termed deGFP4 by Hanson et al. [1]) for pH measurements using fluorescence lifetime imaging microscopy (FLIM) with excellent precision. eGFP-pHsens was either expressed in the cytoplasm or targeted to the mitochondria of Chinese hamster ovary (CHO-K1) cells and applied here for monitoring activity of the M2 proton channel from influenza A virus. It is shown that the M2 protein confers high proton permeability of the plasma membrane upon expression in CHO-K1 cells resulting in rapid and strong changes of the intracellular pH upon pH changes of the extracellular medium. These pH changes are abolished in the presence of amantadine, a specific blocker of the M2 proton channel. These results were obtained using a novel multi-parameter FLIM setup that permits the simultaneous imaging of the fluorescence amplitude ratios and lifetimes of eGFP-pHsens enabling the quick and accurate pH determination with spatial resolution of 500 nm in two color channels with time resolution of below 100 ps. With FLIM, we also demonstrate the simultaneous determination of pH in the cytoplasm and mitochondria showing that the pH in the mitochondrial matrix is slightly higher (around 7.8) than that in the cytoplasm (about 7.0). The results obtained for CHO-K1 cells without M2 channels in comparison to M2-expressing cells show that the pH dynamics is determined by the specific H⁺ permeability of the membrane, the buffering of protons in the internal cell lumen and/or an outwardly directed proton pump activity that stabilizes the interior pH at a higher level than the external acidic pH. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.
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82
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DeCoursey TE, Hosler J. Philosophy of voltage-gated proton channels. J R Soc Interface 2014; 11:20130799. [PMID: 24352668 PMCID: PMC3899857 DOI: 10.1098/rsif.2013.0799] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 11/22/2013] [Indexed: 02/02/2023] Open
Abstract
In this review, voltage-gated proton channels are considered from a mainly teleological perspective. Why do proton channels exist? What good are they? Why did they go to such lengths to develop several unique hallmark properties such as extreme selectivity and ΔpH-dependent gating? Why is their current so minuscule? How do they manage to be so selective? What is the basis for our belief that they conduct H(+) and not OH(-)? Why do they exist in many species as dimers when the monomeric form seems to work quite well? It is hoped that pondering these questions will provide an introduction to these channels and a way to logically organize their peculiar properties as well as to understand how they are able to carry out some of their better-established biological functions.
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Affiliation(s)
- Thomas E. DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University, 1750 West Harrison, Chicago, IL 60612, USA
| | - Jonathan Hosler
- Department of Biochemistry, University of Mississippi Medical Center, Jackson, MS 39216, USA
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83
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Lee YT, Kim KH, Ko EJ, Lee YN, Kim MC, Kwon YM, Tang Y, Cho MK, Lee YJ, Kang SM. New vaccines against influenza virus. Clin Exp Vaccine Res 2013; 3:12-28. [PMID: 24427759 PMCID: PMC3890446 DOI: 10.7774/cevr.2014.3.1.12] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2013] [Revised: 11/15/2013] [Accepted: 11/20/2013] [Indexed: 12/23/2022] Open
Abstract
Vaccination is one of the most effective and cost-benefit interventions that prevent the mortality and reduce morbidity from infectious pathogens. However, the licensed influenza vaccine induces strain-specific immunity and must be updated annually based on predicted strains that will circulate in the upcoming season. Influenza virus still causes significant health problems worldwide due to the low vaccine efficacy from unexpected outbreaks of next epidemic strains or the emergence of pandemic viruses. Current influenza vaccines are based on immunity to the hemagglutinin antigen that is highly variable among different influenza viruses circulating in humans and animals. Several scientific advances have been endeavored to develop universal vaccines that will induce broad protection. Universal vaccines have been focused on regions of viral proteins that are highly conserved across different virus subtypes. The strategies of universal vaccines include the matrix 2 protein, the hemagglutinin HA2 stalk domain, and T cell-based multivalent antigens. Supplemented and/or adjuvanted vaccination in combination with universal target antigenic vaccines would have much promise. This review summarizes encouraging scientific advances in the field with a focus on novel vaccine designs.
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Affiliation(s)
- Young-Tae Lee
- Center for Inflammation, Immunity & Infection, and Department of Biology, Georgia State University, Atlanta, GA, USA
| | - Ki-Hye Kim
- Center for Inflammation, Immunity & Infection, and Department of Biology, Georgia State University, Atlanta, GA, USA
| | - Eun-Ju Ko
- Center for Inflammation, Immunity & Infection, and Department of Biology, Georgia State University, Atlanta, GA, USA
| | - Yu-Na Lee
- Center for Inflammation, Immunity & Infection, and Department of Biology, Georgia State University, Atlanta, GA, USA
| | - Min-Chul Kim
- Animal and Plant Quarantine Agency, Anyang, Korea
| | - Young-Man Kwon
- Center for Inflammation, Immunity & Infection, and Department of Biology, Georgia State University, Atlanta, GA, USA
| | - Yinghua Tang
- Center for Inflammation, Immunity & Infection, and Department of Biology, Georgia State University, Atlanta, GA, USA
| | - Min-Kyoung Cho
- Center for Inflammation, Immunity & Infection, and Department of Biology, Georgia State University, Atlanta, GA, USA
| | | | - Sang-Moo Kang
- Center for Inflammation, Immunity & Infection, and Department of Biology, Georgia State University, Atlanta, GA, USA
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84
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Polishchuk AL, Cristian L, Pinto LH, Lear JD, DeGrado WF. Mechanistic insights from functional characterization of an unnatural His37 mutant of the influenza A/M2 protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:1082-7. [PMID: 24269540 DOI: 10.1016/j.bbamem.2013.11.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 10/02/2013] [Accepted: 11/12/2013] [Indexed: 11/25/2022]
Abstract
The influenza A/M2 protein is a homotetrameric single-pass integral membrane protein encoded by the influenza A viral genome. Its transmembrane domain represents both a crucial drug target and a minimalistic model system for transmembrane proton transport and charge stabilization. Recent structural and functional studies of M2 have suggested that the proton transport mechanism involves sequential extraviral protonation and intraviral deprotonation of a highly conserved His37 side chain by the transported proton, consistent with a pH-activated proton shuttle mechanism. Multiple tautomeric forms of His can be formed, and it is not known whether they contribute to the mechanism of proton shuttling. Here we present the thermodynamic and functional characterization of an unnatural amino acid mutant at His37, where the imidazole side chain is substituted with a 4-thiazolyl group that is unable to undergo tautomerization and has a significantly lower solution pKa. The mutant construct has a similar stability to the wild-type protein at pH8 in bilayers and is virtually inactive at external pH7.4 in a semiquantitative liposome flux assay as expected from its lower sidechain pKa. However when the external buffer pH is lowered to 4.9 and 2.4, the mutant shows increasing amantadine sensitive flux of a similar magnitude to that of the wild type construct at pH7.4 and 4.9 respectively. These findings are in line with mechanistic hypotheses suggesting that proton flux through M2 is mediated by proton exchange from adjacent water molecules with the His37 sidechain, and that tautomerization is not required for proton translocation. This article is part of a Special Issue entitled: Viral Membrane Proteins - Channels for Cellular Networking.
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Affiliation(s)
- Alexei L Polishchuk
- Department of Biochemistry and Biophysics, The Robert Wood Johnson Foundation, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Lidia Cristian
- Department of Biochemistry and Biophysics, The Robert Wood Johnson Foundation, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Lawrence H Pinto
- Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208, USA
| | - James D Lear
- Department of Biochemistry and Biophysics, The Robert Wood Johnson Foundation, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - William F DeGrado
- Department of Biochemistry and Biophysics, The Robert Wood Johnson Foundation, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA.
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85
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Edinger TO, Pohl MO, Stertz S. Entry of influenza A virus: host factors and antiviral targets. J Gen Virol 2013; 95:263-277. [PMID: 24225499 DOI: 10.1099/vir.0.059477-0] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Influenza virus is a major human pathogen that causes annual epidemics and occasional pandemics. Moreover, the virus causes outbreaks in poultry and other animals, such as pigs, requiring costly and laborious countermeasures. Therefore, influenza virus has a substantial impact on health and the global economy. Here, we review entry of this important pathogen into target cells, an essential process by which viral genomes are delivered from extracellular virions to sites of transcription/replication in the cell nucleus. We summarize current knowledge on the interaction of influenza viruses with their receptor, sialic acid, and highlight the ongoing search for additional receptors. We describe receptor-mediated endocytosis and the recently discovered macropinocytosis as alternative virus uptake pathways, and illustrate the subsequent endosomal trafficking of the virus with advanced live microscopy techniques. Release of virus from the endosome and import of the viral ribonucleoproteins into the host cell nucleus are also outlined. Although a focus has been on viral protein function during entry, recent studies have revealed exciting information on cellular factors required for influenza virus entry. We highlight these, and discuss established entry inhibitors targeting viral and host factors, as well as the latest prospects for designing novel 'anti-entry' compounds. New entry inhibitors are of particular importance for current efforts to develop the next generation of anti-influenza drugs - entry is the first essential step of virus replication and is an ideal target to block infection efficiently.
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Affiliation(s)
- Thomas O Edinger
- Institute of Medical Virology, University of Zurich, 8057 Zurich, Switzerland
| | - Marie O Pohl
- Institute of Medical Virology, University of Zurich, 8057 Zurich, Switzerland
| | - Silke Stertz
- Institute of Medical Virology, University of Zurich, 8057 Zurich, Switzerland
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86
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Gu RX, Liu LA, Wei DQ. Structural and energetic analysis of drug inhibition of the influenza A M2 proton channel. Trends Pharmacol Sci 2013; 34:571-80. [PMID: 24011996 DOI: 10.1016/j.tips.2013.08.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Revised: 08/09/2013] [Accepted: 08/12/2013] [Indexed: 01/07/2023]
Abstract
The type A influenza virus matrix protein 2 (M2) is a highly selective proton channel in the viral envelope. Because of its crucial role in viral infection and replication, the M2 channel has been a target of anti-influenza drugs. Due to the occurrence of drug-resistant mutations in the M2 channel, existing anti-influenza drugs that block the M2 channel, such as amantadine and rimantadine, have lost their efficacy against these mutant channels. Recent experimental and computational efforts have made great progress in understanding the drug resistance mechanisms of these mutations as well as designing novel drug candidates to block the mutant M2 channels. In this review, we briefly summarize the structural characteristics of the M2 channel, and then we discuss these recent studies on drug resistance and drug design of the mutant channels, focusing on the structures and energetics. We show that structural biology experiments and molecular modeling have led to the successful design of novel drugs targeting mutant M2 channels.
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Affiliation(s)
- Ruo-Xu Gu
- State Key Laboratory of Microbial Metabolism, and College of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai Minhang District, 200240, China
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87
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Dong H, Yi M, Cross TA, Zhou HX. Ab initio calculations and validation of the pH-dependent structures of the His37-Trp41 quartet, the heart of acid activation and proton conductance in the M2 protein of Influenza A virus. Chem Sci 2013; 4:2776-2787. [PMID: 23930201 PMCID: PMC3733280 DOI: 10.1039/c3sc50293g] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The M2 protein of Influenza A virus forms a homotetrameric proton channel activated by low pH. The His37-Trp41 quartet is the heart of acid activation and proton conductance, but the functional mechanism is still controversial. We carried out ab initio calculations to model the pH-dependent structures of the His37-Trp41 quartet. In our model at neutral pH, the four His37 residues are configured into a pair of dimers; in each dimer, a proton is shared between Nδ1 on one residue and Nε2 on the other, and, under the restraint of the backbone, the two imidazole rings are nearly parallel, in contrast to a perpendicular arrangement for a free imidazole-imidazolium dimer. Within each dimer the +1 charge is highly delocalized, contributing to its stabilization in a low dielectric environment. The Nδ1-H-Nε2 strong hydrogen bonds result in significantly downfield shifted Nδ1 and Nε2 chemical shifts (at 169.7 and 167.6 ppm, respectively), in good agreement with experiments. In our model at acidic pH (where the channel becomes activated), a third proton binds to an imidazole-imidazolium dimer; the imidazole rings rotate away (each by ~55°) from each other, destroying the dimer structure. The two imidazoliums are stabilized by hydrogen bonds with water molecules and a cation-π interaction with Trp41. The Raman spectra calculated for the His37-Trp41 quartet at neutral and acidic pH are in agreement with experiments. Our calculations support an activation and conductance mechanism in which a hydronium ion from the N-terminal side passes a proton to an imidazole-imidazolium dimer; when the Trp41 gate is open, relaying of a proton onto a water molecule from the C-terminal side then allows the imidazole-imidazolium dimer to reform and be ready for the next round of proton conductance.
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Affiliation(s)
- Hao Dong
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
| | - Myunggi Yi
- Department of Biomedical Engineering, Pukyong National University, Busan 608-737, Korea
| | - Timothy A. Cross
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, and National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, FL 32310, USA
| | - Huan-Xiang Zhou
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
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88
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DeCoursey TE. Voltage-gated proton channels: molecular biology, physiology, and pathophysiology of the H(V) family. Physiol Rev 2013; 93:599-652. [PMID: 23589829 PMCID: PMC3677779 DOI: 10.1152/physrev.00011.2012] [Citation(s) in RCA: 176] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Voltage-gated proton channels (H(V)) are unique, in part because the ion they conduct is unique. H(V) channels are perfectly selective for protons and have a very small unitary conductance, both arguably manifestations of the extremely low H(+) concentration in physiological solutions. They open with membrane depolarization, but their voltage dependence is strongly regulated by the pH gradient across the membrane (ΔpH), with the result that in most species they normally conduct only outward current. The H(V) channel protein is strikingly similar to the voltage-sensing domain (VSD, the first four membrane-spanning segments) of voltage-gated K(+) and Na(+) channels. In higher species, H(V) channels exist as dimers in which each protomer has its own conduction pathway, yet gating is cooperative. H(V) channels are phylogenetically diverse, distributed from humans to unicellular marine life, and perhaps even plants. Correspondingly, H(V) functions vary widely as well, from promoting calcification in coccolithophores and triggering bioluminescent flashes in dinoflagellates to facilitating killing bacteria, airway pH regulation, basophil histamine release, sperm maturation, and B lymphocyte responses in humans. Recent evidence that hH(V)1 may exacerbate breast cancer metastasis and cerebral damage from ischemic stroke highlights the rapidly expanding recognition of the clinical importance of hH(V)1.
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Affiliation(s)
- Thomas E DeCoursey
- Dept. of Molecular Biophysics and Physiology, Rush University Medical Center HOS-036, 1750 West Harrison, Chicago, IL 60612, USA.
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89
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Zhou HX, Cross TA. Modeling the membrane environment has implications for membrane protein structure and function: influenza A M2 protein. Protein Sci 2013; 22:381-94. [PMID: 23389890 DOI: 10.1002/pro.2232] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 01/29/2013] [Accepted: 01/30/2013] [Indexed: 12/13/2022]
Abstract
The M2 protein, a proton channel, from Influenza A has been structurally characterized by X-ray diffraction and by solution and solid-state NMR spectroscopy in a variety of membrane mimetic environments. These structures show substantial backbone differences even though they all present a left-handed tetrameric helical bundle for the transmembrane domain. Variations in the helix tilt influence drug binding and the chemistry of the histidine tetrad responsible for acid activation, proton selectivity and transport. Some of the major structural differences do not arise from the lack of precision, but instead can be traced to the influences of the membrane mimetic environments. The structure in lipid bilayers displays unique chemistry for the histidine tetrad, which binds two protons cooperatively to form a pair of imidazole-imidazolium dimers. The resulting interhistidine hydrogen bonds contribute to a three orders of magnitude enhancement in tetramer stability. Integration with computation has provided detailed understanding of the functional mechanism for proton selectivity, conductance and gating of this important drug target.
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Affiliation(s)
- Huan-Xiang Zhou
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
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90
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Kang SM, Kim MC, Compans RW. Virus-like particles as universal influenza vaccines. Expert Rev Vaccines 2013; 11:995-1007. [PMID: 23002980 DOI: 10.1586/erv.12.70] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Current influenza vaccines are primarily targeted to induce immunity to the influenza virus strain-specific hemagglutinin antigen and are not effective in controlling outbreaks of new pandemic viruses. An approach for developing universal vaccines is to present highly conserved antigenic epitopes in an immunogenic conformation such as virus-like particles (VLPs) together with an adjuvant to enhance the vaccine immunogenicity. In this review, the authors focus on conserved antigenic targets and molecular adjuvants that were presented in VLPs. Conserved antigenic targets that include the hemagglutinin stalk domain, the external domain of influenza M2 and neuraminidase are discussed in addition to molecular adjuvants that are engineered to be incorporated into VLPs in a membrane-anchored form.
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Affiliation(s)
- Sang-Moo Kang
- Center for Inflammation, Immunity & Infection, and Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
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91
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Hong M, DeGrado WF. Structural basis for proton conduction and inhibition by the influenza M2 protein. Protein Sci 2012; 21:1620-33. [PMID: 23001990 DOI: 10.1002/pro.2158] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 09/10/2012] [Accepted: 09/11/2012] [Indexed: 12/20/2022]
Abstract
The influenza M2 protein forms an acid-activated and drug-sensitive proton channel in the virus envelope that is important for the virus lifecycle. The functional properties and high-resolution structures of this proton channel have been extensively studied to understand the mechanisms of proton conduction and drug inhibition. We review biochemical and electrophysiological studies of M2 and discuss how high-resolution structures have transformed our understanding of this proton channel. Comparison of structures obtained in different membrane-mimetic solvents and under different pH using X-ray crystallography, solution NMR, and solid-state NMR spectroscopy revealed how the M2 structure depends on the environment and showed that the pharmacologically relevant drug-binding site lies in the transmembrane (TM) pore. Competing models of proton conduction have been evaluated using biochemical experiments, high-resolution structural methods, and computational modeling. These results are converging to a model in which a histidine residue in the TM domain mediates proton relay with water, aided by microsecond conformational dynamics of the imidazole ring. These mechanistic insights are guiding the design of new inhibitors that target drug-resistant M2 variants and may be relevant for other proton channels.
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Affiliation(s)
- Mei Hong
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
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92
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Affiliation(s)
- Kalyan Das
- Department of Chemistry and Chemical Biology, Center for Advanced Biotechnology and Medicine, Rutgers University, 679 Hoes Lane, Piscataway, NJ 08854, USA.
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93
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Abstract
Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely, the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dimeric architecture with dual conduction pathways, perfect proton selectivity, a single-channel conductance approximately 10(3) times smaller than most ion channels, voltage-dependent gating that is strongly modulated by the pH gradient, ΔpH, and potent inhibition by Zn(2+) (in many species) but an absence of other potent inhibitors. The recent identification of HV1 in three unicellular marine plankton species has dramatically expanded the phylogenetic family tree. Interest in proton channels in their own right has increased as important physiological roles have been identified in many cells. Proton channels trigger the bioluminescent flash of dinoflagellates, facilitate calcification by coccolithophores, regulate pH-dependent processes in eggs and sperm during fertilization, secrete acid to control the pH of airway fluids, facilitate histamine secretion by basophils, and play a signaling role in facilitating B-cell receptor mediated responses in B-lymphocytes. The most elaborate and best-established functions occur in phagocytes, where proton channels optimize the activity of NADPH oxidase, an important producer of reactive oxygen species. Proton efflux mediated by HV1 balances the charge translocated across the membrane by electrons through NADPH oxidase, minimizes changes in cytoplasmic and phagosomal pH, limits osmotic swelling of the phagosome, and provides substrate H(+) for the production of H2O2 and HOCl, reactive oxygen species crucial to killing pathogens.
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Affiliation(s)
- Thomas E Decoursey
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois, USA.
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94
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M2 protein from influenza A: from multiple structures to biophysical and functional insights. Curr Opin Virol 2012; 2:128-33. [PMID: 22482709 DOI: 10.1016/j.coviro.2012.01.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 01/17/2012] [Accepted: 01/18/2012] [Indexed: 11/21/2022]
Abstract
The M2 protein from influenza A is a proton channel as a tetramer, with a single transmembrane helix from each monomer lining the pore. Val27 and Trp41 form gates at either end of the pore and His37 mediates the shuttling of protons across a central barrier between the N-terminal and C-terminal aqueous pore regions. Numerous structures of this transmembrane domain and of a longer construct that includes an amphipathic helix are now in the Protein Data Bank. Many structural differences are apparent from samples obtained in a variety of membrane mimetic environments. High-resolution structural results in lipid bilayers have provided novel insights into the functional mechanism of the unique HxxxW cluster in the M2 proton channel.
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95
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Stewart SM, Pekosz A. The influenza C virus CM2 protein can alter intracellular pH, and its transmembrane domain can substitute for that of the influenza A virus M2 protein and support infectious virus production. J Virol 2012; 86:1277-81. [PMID: 21917958 PMCID: PMC3255851 DOI: 10.1128/jvi.05681-11] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Accepted: 09/03/2011] [Indexed: 12/11/2022] Open
Abstract
The influenza C virus CM2 protein and a chimeric influenza A virus M2 protein (MCM) containing the CM2 transmembrane domain were assessed for their ability to functionally replace the M2 protein. While all three proteins could alter cytosolic pH to various degrees when expressed from cDNA, only M2 and MCM could at least partially restore infectious virus production to M2-deficient influenza A viruses. The data suggest that while the CM2 ion channel activity is similar to that of M2, sequences in the extracellular and/or cytoplasmic domains play important roles in infectious virus production.
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Affiliation(s)
- Shaun M Stewart
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland, USA
- Division of Biology and Biomedical Sciences, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Andrew Pekosz
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland, USA
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96
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Fischer WB, Wang YT, Schindler C, Chen CP. Mechanism of function of viral channel proteins and implications for drug development. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 294:259-321. [PMID: 22364876 PMCID: PMC7149447 DOI: 10.1016/b978-0-12-394305-7.00006-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Viral channel-forming proteins comprise a class of viral proteins which, similar to their host companions, are made to alter electrochemical or substrate gradients across lipid membranes. These proteins are active during all stages of the cellular life cycle of viruses. An increasing number of proteins are identified as channel proteins, but the precise role in the viral life cycle is yet unknown for the majority of them. This review presents an overview about these proteins with an emphasis on those with available structural information. A concept is introduced which aligns the transmembrane domains of viral channel proteins with those of host channels and toxins to give insights into the mechanism of function of the viral proteins from potential sequence identities. A summary of to date investigations on drugs targeting these proteins is given and discussed in respect of their mode of action in vivo.
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Affiliation(s)
- Wolfgang B. Fischer
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Yi-Ting Wang
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Christina Schindler
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
| | - Chin-Pei Chen
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan
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97
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Zhou HX. Mechanistic insight into the h(2)o/d (2)o isotope effect in the proton transport of the influenza virus m2 protein. J Membr Biol 2011; 244:93-6. [PMID: 22041938 PMCID: PMC3237009 DOI: 10.1007/s00232-011-9402-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Accepted: 10/15/2011] [Indexed: 11/27/2022]
Abstract
The M2 proton channel is essential for the replication of the flu virus and is a known drug target. The functional mechanism of channel activation and conductance is key to both the basic biology of viral replication and the design of drugs that can withstand mutations. A quantitative model was previously developed for calculating the rate of proton transport through the M2 channel. The permeant proton was assumed to diffuse to the pore, obligatorily bind to the His37 tetrad, and then dissociate and be released to either side of the tetrad. Here the model is used to calculate the effect of a change in solvent from H(2)O to D(2)O on the rate of proton transport. The solvent substitution affects two parameters in the model: the proton diffusion constant and the pK (a) for proton binding to the His37 tetrad. When the known effects on these two parameters are included, the deuterium isotope effect calculated from the model is in quantitatively agreement with experimental results. This strict test of the theoretical model provides strong support for the hypothesis that the permeant proton obligatorily binds to and then unbinds from the His37 tetrad. This putatively essential role of the His37 tetrad in the functional mechanism of the M2 channel makes it a promising target for designing mutation-tolerant drugs.
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Affiliation(s)
- Huan-Xiang Zhou
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, USA.
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98
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Hu F, Schmidt-Rohr K, Hong M. NMR detection of pH-dependent histidine-water proton exchange reveals the conduction mechanism of a transmembrane proton channel. J Am Chem Soc 2011; 134:3703-13. [PMID: 21974716 DOI: 10.1021/ja2081185] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The acid-activated proton channel formed by the influenza M2 protein is important for the life cycle of the virus. A single histidine, His37, in the M2 transmembrane domain (M2TM) is responsible for pH activation and proton selectivity of the channel. Recent studies suggested three models for how His37 mediates proton transport: a shuttle mechanism involving His37 protonation and deprotonation, a H-bonded imidazole-imidazolium dimer model, and a transporter model involving large protein conformational changes in synchrony with proton conduction. Using magic-angle-spinning (MAS) solid-state NMR spectroscopy, we examined the proton exchange and backbone conformational dynamics of M2TM in a virus-envelope-mimetic membrane. At physiological temperature and pH, (15)N NMR spectra show fast exchange of the imidazole (15)N between protonated and unprotonated states. To quantify the proton exchange rates, we measured the (15)N T(2) relaxation times and simulated them for chemical-shift exchange and fluctuating N-H dipolar fields under (1)H decoupling and MAS. The exchange rate is 4.5 × 10(5) s(-1) for Nδ1 and 1.0 × 10(5) s(-1) for Nε2, which are approximately synchronized with the recently reported imidazole reorientation. Binding of the antiviral drug amantadine suppressed both proton exchange and ring motion, thus interfering with the proton transfer mechanism. By measuring the relative concentrations of neutral and cationic His as a function of pH, we determined the four pK(a) values of the His37 tetrad in the viral membrane. Fitting the proton current curve using the charge-state populations from these pK(a)'s, we obtained the relative conductance of the five charge states, which showed that the +3 channel has the highest time-averaged unitary conductance. At physiologically relevant pH, 2D correlation spectra indicated that the neutral and cationic histidines do not have close contacts, ruling out the H-bonded dimer model. Moreover, a narrowly distributed nonideal helical structure coexists with a broadly distributed ideal helical conformation without interchange on the sub-10 ms time scale, thus excluding the transporter model in the viral membrane. These data support the shuttle mechanism of proton conduction, whose essential steps involve His-water proton exchange facilitated by imidazole ring reorientations.
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Affiliation(s)
- Fanghao Hu
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA
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99
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Grigoryan G, Moore DT, DeGrado WF. Transmembrane communication: general principles and lessons from the structure and function of the M2 proton channel, K⁺ channels, and integrin receptors. Annu Rev Biochem 2011; 80:211-37. [PMID: 21548783 DOI: 10.1146/annurev-biochem-091008-152423] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Signal transduction across biological membranes is central to life. This process generally happens through communication between different domains and hierarchical coupling of information. Here, we review structural and thermodynamic principles behind transmembrane (TM) signal transduction and discuss common themes. Communication between signaling domains can be understood in terms of thermodynamic and kinetic principles, and complex signaling patterns can arise from simple wiring of thermodynamically coupled domains. We relate this to functions of several signal transduction systems: the M2 proton channel from influenza A virus, potassium channels, integrin receptors, and bacterial kinases. We also discuss key features in the structural rearrangements responsible for signal transduction in these systems.
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Affiliation(s)
- Gevorg Grigoryan
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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100
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Mancini N, Solforosi L, Clementi N, De Marco D, Clementi M, Burioni R. A potential role for monoclonal antibodies in prophylactic and therapeutic treatment of influenza. Antiviral Res 2011; 92:15-26. [DOI: 10.1016/j.antiviral.2011.07.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 05/19/2011] [Accepted: 07/12/2011] [Indexed: 10/17/2022]
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