1
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Madsen JJ, Rossman JS. Cholesterol and M2 Rendezvous in Budding and Scission of Influenza A Virus. Subcell Biochem 2023; 106:441-459. [PMID: 38159237 DOI: 10.1007/978-3-031-40086-5_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
The cholesterol of the host cell plasma membrane and viral M2 protein plays a crucial role in multiple stages of infection and replication of the influenza A virus. Cholesterol is required for the formation of heterogeneous membrane microdomains (or rafts) in the budozone of the host cell that serves as assembly sites for the viral components. The raft microstructures act as scaffolds for several proteins. Cholesterol may further contribute to the mechanical forces necessary for membrane scission in the last stage of budding and help to maintain the stability of the virus envelope. The M2 protein has been shown to cause membrane scission in model systems by promoting the formation of curved lipid bilayer structures that, in turn, can lead to membrane vesicles budding off or scission intermediates. Membrane remodeling by M2 is intimately linked with cholesterol as it affects local lipid composition, fluidity, and stability of the membrane. Thus, both cholesterol and M2 protein contribute to the efficient and proper release of newly formed influenza viruses from the virus-infected cells.
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Affiliation(s)
- Jesper J Madsen
- Global and Planetary Health, Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, FL, USA.
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA.
| | - Jeremy S Rossman
- School of Biosciences, University of Kent, Canterbury, Kent, UK
- Research-Aid Networks, Chicago, IL, USA
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2
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Thomaston JL, Konstantinidi A, Liu L, Lambrinidis G, Tan J, Caffrey M, Wang J, DeGrado WF, Kolocouris A. X-ray Crystal Structures of the Influenza M2 Proton Channel Drug-Resistant V27A Mutant Bound to a Spiro-Adamantyl Amine Inhibitor Reveal the Mechanism of Adamantane Resistance. Biochemistry 2020; 59:627-634. [PMID: 31894969 PMCID: PMC7224692 DOI: 10.1021/acs.biochem.9b00971] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The V27A mutation confers adamantane resistance on the influenza A matrix 2 (M2) proton channel and is becoming more prevalent in circulating populations of influenza A virus. We have used X-ray crystallography to determine structures of a spiro-adamantyl amine inhibitor bound to M2(22-46) V27A and also to M2(21-61) V27A in the Inwardclosed conformation. The spiro-adamantyl amine binding site is nearly identical for the two crystal structures. Compared to the M2 "wild type" (WT) with valine at position 27, we observe that the channel pore is wider at its N-terminus as a result of the V27A mutation and that this removes V27 side chain hydrophobic interactions that are important for binding of amantadine and rimantadine. The spiro-adamantyl amine inhibitor blocks proton conductance in the WT and V27A mutant channels by shifting its binding site in the pore depending on which residue is present at position 27. Additionally, in the structure of the M2(21-61) V27A construct, the C-terminus of the channel is tightly packed relative to that of the M2(22-46) construct. We observe that residues Asp44, Arg45, and Phe48 face the center of the channel pore and would be well-positioned to interact with protons exiting the M2 channel after passing through the His37 gate. A 300 ns molecular dynamics simulation of the M2(22-46) V27A-spiro-adamantyl amine complex predicts with accuracy the position of the ligands and waters inside the pore in the X-ray crystal structure of the M2(22-46) V27A complex.
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Affiliation(s)
- Jessica L. Thomaston
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA
- Membrane Structural and Functional Biology (MS&FB) Group, School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin D02 R590, Ireland
| | - Athina Konstantinidi
- Department of Pharmaceutical Chemistry, National and Kapodistrian University of Athens, 15771 Athens, Greece
| | - Lijun Liu
- State Key Laboratory of Chemical Oncogenomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen 518055, China
- DLX Scientific, Lawrence, KS 66049, USA
| | - George Lambrinidis
- Department of Pharmaceutical Chemistry, National and Kapodistrian University of Athens, 15771 Athens, Greece
| | - Jingquan Tan
- Membrane Structural and Functional Biology (MS&FB) Group, School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin D02 R590, Ireland
| | - Martin Caffrey
- Membrane Structural and Functional Biology (MS&FB) Group, School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin D02 R590, Ireland
| | - Jun Wang
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, USA
| | - William F. DeGrado
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA
| | - Antonios Kolocouris
- Department of Pharmaceutical Chemistry, National and Kapodistrian University of Athens, 15771 Athens, Greece
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3
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Kim G, Raymond HE, Herneisen AL, Wong-Rolle A, Howard KP. The distal cytoplasmic tail of the influenza A M2 protein dynamically extends from the membrane. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2019; 1861:1421-1427. [PMID: 31153909 PMCID: PMC6625909 DOI: 10.1016/j.bbamem.2019.05.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 05/24/2019] [Accepted: 05/28/2019] [Indexed: 12/19/2022]
Abstract
The influenza A M2 protein is a multifunctional membrane-associated homotetramer that orchestrates several essential events in the viral infection cycle. The monomeric subunits of the M2 homotetramer consist of an N-terminal ectodomain, a transmembrane domain, and a C-terminal cytoplasmic domain. The transmembrane domain forms a four-helix proton channel that promotes uncoating of virions upon host cell entry. The membrane-proximal region of the C-terminal domain forms a surface-associated amphipathic helix necessary for viral budding. The structure of the remaining ~34 residues of the distal cytoplasmic tail has yet to be fully characterized despite the functional significance of this region for influenza infectivity. Here, we extend structural and dynamic studies of the poorly characterized M2 cytoplasmic tail. We used SDSL-EPR to collect site-specific information on the mobility, solvent accessibility, and conformational properties of residues 61-70 of the full-length, cell-expressed M2 protein reconstituted into liposomes. Our analysis is consistent with the predominant population of the C-terminal tail dynamically extending away from the membranes surface into the aqueous medium. These findings provide insight into the hypothesis that the C-terminal domain serves as a sensor that regulates how M2 protein participates in critical events in the viral infection cycle.
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Affiliation(s)
- Grace Kim
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Hayley E Raymond
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Alice L Herneisen
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Abigail Wong-Rolle
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Kathleen P Howard
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America.
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4
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Thomaston JL, Wu Y, Polizzi N, Liu L, Wang J, DeGrado WF. X-ray Crystal Structure of the Influenza A M2 Proton Channel S31N Mutant in Two Conformational States: An Open and Shut Case. J Am Chem Soc 2019; 141:11481-11488. [PMID: 31184871 DOI: 10.1021/jacs.9b02196] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The amantadine-resistant S31N mutant of the influenza A M2 proton channel has become prevalent in currently circulating viruses. Here, we have solved an X-ray crystal structure of M2(22-46) S31N that contains two distinct conformational states within its asymmetric unit. This structure reveals the mechanism of adamantane resistance in both conformational states of the M2 channel. In the Inwardopen conformation, the mutant Asn31 side chain faces the channel pore and sterically blocks the adamantane binding site. In the Inwardclosed conformation, Asn31 forms hydrogen bonds with carbonyls at the monomer-monomer interface, which twists the monomer helices and constricts the channel pore at the drug binding site. We also examine M2(19-49) WT and S31N using solution NMR spectroscopy and show that distribution of the two conformational states is dependent on both detergent choice and experimental pH.
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Affiliation(s)
- Jessica L Thomaston
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
| | - Yibing Wu
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
| | - Nicholas Polizzi
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
| | - Lijun Liu
- State Key Laboratory of Chemical Oncogenomics , Peking University Shenzhen Graduate School , Shenzhen 518055 , China.,DLX Scientific , Lawrence , Kansas 66049 , United States
| | - Jun Wang
- Department of Pharmacology and Toxicology, College of Pharmacy , University of Arizona , Tucson , Arizona 85721 , United States
| | - William F DeGrado
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
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5
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Tauroursodeoxycholic acid (TUDCA) inhibits influenza A viral infection by disrupting viral proton channel M2. Sci Bull (Beijing) 2019; 64:180-188. [PMID: 32288967 PMCID: PMC7104969 DOI: 10.1016/j.scib.2018.08.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 06/22/2018] [Accepted: 07/22/2018] [Indexed: 01/20/2023]
Abstract
Influenza is a persistent threat to human health and there is a continuing requirement for updating anti-influenza strategies. Initiated by observations of different endoplasmic reticulum (ER) responses of host to seasonal H1N1 and highly pathogenic avian influenza (HPAI) A H5N1 infections, we identified an alternative antiviral role of tauroursodeoxycholic acid (TUDCA), a clinically available ER stress inhibitor, both in vitro and in vivo. Rather than modulating ER stress in host cells, TUDCA abolished the proton conductivity of viral M2 by disrupting its oligomeric states, which induces inefficient viral infection. We also showed that M2 penetrated cells, whose intracellular uptake depended on its proton channel activity, an effect observed in both TUDCA and M2 inhibitor amantadine. The identification and application of TUDCA as an inhibitor of M2 proton channel will expand our understanding of IAV biology and complement current anti-IAV arsenals.
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6
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Hameed S, Bhattarai P, Dai Z. Cerasomes and Bicelles: Hybrid Bilayered Nanostructures With Silica-Like Surface in Cancer Theranostics. Front Chem 2018; 6:127. [PMID: 29721494 PMCID: PMC5915561 DOI: 10.3389/fchem.2018.00127] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 04/03/2018] [Indexed: 01/10/2023] Open
Abstract
Over years, theranostic nanoplatforms have provided a new avenue for the diagnosis and treatment of various cancer types. To this end, a myriad of nanocarriers such as polymeric micelles, liposomes, and inorganic nanoparticles (NPs) with distinct physiochemical and biological properties are routinely investigated for preclinical and clinical studies. So far, liposomes have received great attention for various biomedical applications, however, it still suffers from insufficient morphological stability. On the other hand, inorganic NPs depicting excellent therapeutic ability have failed to address biocompatibility issues. This has raised a serious concern about the clinical approval of multifunctional organic or inorganic-based theranostic agents. Recently, partially silica coated nanohybrids such as cerasomes and bicelles demonstrating both diagnostic and therapeutic ability in a single system, have drawn profound attention as a fascinating novel drug delivery system. Compared with traditional liposomal or inorganic-based nanoformulations, this new and highly stable nanocarriers integrates the functional attributes of biomimetic liposomes and silica NPs, therefore, synergize strengths and functions, or even surpass weaknesses of individual components. This review at its best enlightens the emerging concept of such partially silica coated nanohybrids, fabrication strategies, and theranostic opportunities to combat cancer and related diseases.
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Affiliation(s)
- Sadaf Hameed
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, China
| | - Pravin Bhattarai
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, China
| | - Zhifei Dai
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, China
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7
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Herneisen AL, Sahu ID, McCarrick RM, Feix JB, Lorigan GA, Howard KP. A Budding-Defective M2 Mutant Exhibits Reduced Membrane Interaction, Insensitivity to Cholesterol, and Perturbed Interdomain Coupling. Biochemistry 2017; 56:5955-5963. [PMID: 29034683 PMCID: PMC6112238 DOI: 10.1021/acs.biochem.7b00924] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Influenza A M2 is a membrane-associated protein with a C-terminal amphipathic helix that plays a cholesterol-dependent role in viral budding. An M2 mutant with alanine substitutions in the C-terminal amphipathic helix is deficient in viral scission. With the goal of providing atomic-level understanding of how the wild-type protein functions, we used a multipronged site-directed spin labeling electron paramagnetic resonance spectroscopy (SDSL-EPR) approach to characterize the conformational properties of the alanine mutant. We spin-labeled sites in the transmembrane (TM) domain and the C-terminal amphipathic helix (AH) of wild-type (WT) and mutant M2, and collected information on line shapes, relaxation rates, membrane topology, and distances within the homotetramer in membranes with and without cholesterol. Our results identify marked differences in the conformation and dynamics between the WT and the alanine mutant. Compared to WT, the dominant population of the mutant AH is more dynamic, shallower in the membrane, and has altered quaternary arrangement of the C-terminal domain. While the AH becomes more dynamic, the dominant population of the TM domain of the mutant is immobilized. The presence of cholesterol changes the conformation and dynamics of the WT protein, while the alanine mutant is insensitive to cholesterol. These findings provide new insight into how M2 may facilitate budding. We propose the AH-membrane interaction modulates the arrangement of the TM helices, effectively stabilizing a conformational state that enables M2 to facilitate viral budding. Antagonizing the properties of the AH that enable interdomain coupling within M2 may therefore present a novel strategy for anti-influenza drug design.
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Affiliation(s)
- Alice L. Herneisen
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, Pennsylvania 19081, United States
| | - Indra D. Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Robert M. McCarrick
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Jimmy B. Feix
- Department of Biophysics, National Biomedical EPR Center, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, United States
| | - Gary A. Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Kathleen P. Howard
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, Pennsylvania 19081, United States
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8
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Jeong BS, Dyer RB. Proton Transport Mechanism of M2 Proton Channel Studied by Laser-Induced pH Jump. J Am Chem Soc 2017; 139:6621-6628. [PMID: 28467842 DOI: 10.1021/jacs.7b00617] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The M2 proton transport channel of the influenza virus A is an important model system because it conducts protons with high selectivity and unidirectionally when activated at low pH, despite the relative simplicity of its structure. Although it has been studied extensively, the molecular details of the pH-dependent gating and proton conductance mechanisms are incompletely understood. We report direct observation of the M2 proton channel activation process using a laser-induced pH jump coupled with tryptophan fluorescence as a probe. Biphasic kinetics is observed, with the fast phase corresponding to the His37 protonation, and the slow phase associated with the subsequent conformation change. Unusually fast His37 protonation was observed (2.0 × 1010 M-1 s-1), implying the existence of proton collecting antennae for expedited proton transport. The conformation change (4 × 103 s-1) was about 2 orders of magnitude slower than protonation at endosomal pH, suggesting that a transporter model is likely not feasible.
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Affiliation(s)
- Ban-Seok Jeong
- Department of Chemistry, Emory University , Atlanta, Georgia 30322, United States
| | - R Brian Dyer
- Department of Chemistry, Emory University , Atlanta, Georgia 30322, United States
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9
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Xu L, Xia M, Guo J, Sun X, Li H, Xu C, Gu X, Zhang H, Yi J, Fang Y, Xie H, Wang J, Shen Z, Xue B, Sun Y, Meckel T, Chen YH, Hu Z, Li Z, Xu C, Gong H, Liu W. Impairment on the lateral mobility induced by structural changes underlies the functional deficiency of the lupus-associated polymorphism FcγRIIB-T232. J Exp Med 2016; 213:2707-2727. [PMID: 27799621 PMCID: PMC5110019 DOI: 10.1084/jem.20160528] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 08/08/2016] [Accepted: 09/28/2016] [Indexed: 12/18/2022] Open
Abstract
Xu et al. show that the lupus-associated polymorphism FcγRIIB-T232 has structural changes of the TM domain that reduces lateral mobility and inhibitory functions. FcγRIIB functions to suppress the activation of immune cells. A single-nucleotide polymorphism in the transmembrane (TM) domain of FcγRIIB, FcγRIIB-T232, is associated with lupus. In this study, we investigated the pathogenic mechanism of FcγRIIB-T232 at both functional and structural levels. Our results showed that FcγRIIB-T232 exhibited significantly reduced lateral mobility compared with FcγRIIB-I232 and was significantly less enriched into the microclusters of immune complexes (ICs) after stimulation. However, if sufficient responding time is given for FcγRIIB-T232 to diffuse and interact with the ICs, FcγRIIB-T232 can restore its inhibitory function. Moreover, substituting the FcγRIIB-T232 TM domain with that of a fast floating CD86 molecule restored both the rapid mobility and the inhibitory function, which further corroborated the importance of fast mobility for FcγRIIB to function. Mechanistically, the crippled lateral mobility of FcγRIIB-T232 can be explained by the structural changes of the TM domain. Both atomistic simulations and nuclear magnetic resonance measurement indicated that the TM helix of FcγRIIB-T232 exhibited a more inclined orientation than that of FcγRIIB-I232, thus resulting in a longer region embedded in the membrane. Therefore, we conclude that the single-residue polymorphism T232 enforces the inclination of the TM domain and thereby reduces the lateral mobility and inhibitory functions of FcγRIIB.
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Affiliation(s)
- Liling Xu
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Mengdie Xia
- Ministry of Education Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jun Guo
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Xiaolin Sun
- Department of Rheumatology and Immunology, Clinical Immunology Center, Peking University People's Hospital, Beijing 100044, China
| | - Hua Li
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Chenguang Xu
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xiaomei Gu
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Haowen Zhang
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Junyang Yi
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yan Fang
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Hengyi Xie
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jing Wang
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Zhixun Shen
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Boxin Xue
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Biodynamic Optical Imaging Center, School of Life Sciences, Peking University, Beijing 100871, China
| | - Yujie Sun
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Biodynamic Optical Imaging Center, School of Life Sciences, Peking University, Beijing 100871, China
| | - Tobias Meckel
- Membrane Dynamics, Department of Biology, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| | - Ying-Hua Chen
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Zhibin Hu
- Department of Epidemiology, School of Public Health, Nanjing Medical University, Nanjing 211166, China
| | - Zhanguo Li
- Department of Rheumatology and Immunology, Clinical Immunology Center, Peking University People's Hospital, Beijing 100044, China
| | - Chenqi Xu
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China .,School of Life Science and Technology, ShanghaiTech University, Shanghai 200031, China
| | - Haipeng Gong
- Ministry of Education Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Wanli Liu
- Ministry of Education Key Laboratory of Protein Sciences, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Institute for Immunology, School of Life Sciences, Tsinghua University, Beijing 100084, China
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10
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Saotome K, Duong-Ly KC, Howard KP. Influenza A M2 protein conformation depends on choice of model membrane. Biopolymers 2016; 104:405-11. [PMID: 25652904 DOI: 10.1002/bip.22617] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 01/17/2015] [Accepted: 01/24/2015] [Indexed: 11/08/2022]
Abstract
While crystal and NMR structures exist of the influenza A M2 protein, there is disagreement between models. Depending on the requirements of the technique employed, M2 has been studied in a range of membrane mimetics including detergent micelles and membrane bilayers differing in lipid composition. The use of different model membranes complicates the integration of results from published studies necessary for an overall understanding of the M2 protein. Here we show using site-directed spin-label EPR spectroscopy (SDSL-EPR) that the conformations of M2 peptides in membrane bilayers are clearly influenced by the lipid composition of the bilayers. Altering the bilayer thickness or the lateral pressure profile within the bilayer membrane changes the M2 conformation observed. The multiple M2 peptide conformations observed here, and in other published studies, optimistically may be considered conformations that are sampled by the protein at various stages during influenza infectivity. However, care should be taken that the heterogeneity observed in published structures is not simply an artifact of the choice of the model membrane.
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Affiliation(s)
- Kei Saotome
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081
| | - Krisna C Duong-Ly
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081
| | - Kathleen P Howard
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081
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11
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Kim SS, Upshur MA, Saotome K, Sahu ID, McCarrick RM, Feix JB, Lorigan GA, Howard KP. Cholesterol-Dependent Conformational Exchange of the C-Terminal Domain of the Influenza A M2 Protein. Biochemistry 2015; 54:7157-67. [PMID: 26569023 PMCID: PMC4734095 DOI: 10.1021/acs.biochem.5b01065] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The C-terminal amphipathic helix of the influenza A M2 protein plays a critical cholesterol-dependent role in viral budding. To provide atomic-level detail on the impact cholesterol has on the conformation of M2 protein, we spin-labeled sites right before and within the C-terminal amphipathic helix of the M2 protein. We studied the spin-labeled M2 proteins in membranes both with and without cholesterol. We used a multipronged site-directed spin-label electron paramagnetic resonance (SDSL-EPR) approach and collected data on line shapes, relaxation rates, accessibility of sites to the membrane, and distances between symmetry-related sites within the tetrameric protein. We demonstrate that the C-terminal amphipathic helix of M2 populates at least two conformations in POPC/POPG 4:1 bilayers. Furthermore, we show that the conformational state that becomes more populated in the presence of cholesterol is less dynamic, less membrane buried, and more tightly packed than the other state. Cholesterol-dependent changes in M2 could be attributed to the changes cholesterol induces in bilayer properties and/or direct binding of cholesterol to the protein. We propose a model consistent with all of our experimental data that suggests that the predominant conformation we observe in the presence of cholesterol is relevant for the understanding of viral budding.
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Affiliation(s)
- Sangwoo S. Kim
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081
| | - Mary Alice Upshur
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081
| | - Kei Saotome
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081
| | - Indra D. Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056
| | - Robert M. McCarrick
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056
| | - Jimmy B. Feix
- Department of Biophysics, National Biomedical EPR Center, Medical College of Wisconsin, Milwaukee, WI 53226
| | - Gary A. Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056
| | - Kathleen P. Howard
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081
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12
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Huang S, Green B, Thompson M, Chen R, Thomaston J, DeGrado WF, Howard KP. C-terminal juxtamembrane region of full-length M2 protein forms a membrane surface associated amphipathic helix. Protein Sci 2015; 24:426-9. [PMID: 25545360 DOI: 10.1002/pro.2631] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 12/22/2014] [Accepted: 12/22/2014] [Indexed: 02/01/2023]
Abstract
The influenza A M2 protein is a 97-residue integral membrane protein involved in viral budding and proton conductance. Although crystal and NMR structures exist of truncated constructs of the protein, there is disagreement between models and only limited structural data are available for the full-length protein. Here, the structure of the C-terminal juxtamembrane region (sites 50-60) is investigated in the full-length M2 protein using site-directed spin-labeling electron paramagnetic resonance (EPR) spectroscopy in lipid bilayers. Sites 50-60 were chosen for study because this region has been shown to be critical to the role the M2 protein plays in viral budding. Continuous wave EPR spectra and power saturation data in the presence of paramagnetic membrane soluble oxygen are consistent with a membrane surface associated amphipathic helix. Comparison between data from the C-terminal juxtamembrane region in full-length M2 protein with data from a truncated M2 construct demonstrates that the line shapes and oxygen accessibilities are remarkably similar between the full-length and truncated form of the protein.
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Affiliation(s)
- Shenstone Huang
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, Pennsylvania, 19081
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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
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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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Rouse SL, Sansom MSP. Interactions of lipids and detergents with a viral ion channel protein: molecular dynamics simulation studies. J Phys Chem B 2014; 119:764-72. [PMID: 25286030 PMCID: PMC4306293 DOI: 10.1021/jp505127y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
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Structural
studies of membrane proteins have highlighted the likely
influence of membrane mimetic environments (i.e., lipid bilayers versus
detergent micelles) on the conformation and dynamics of small α-helical
membrane proteins. We have used molecular dynamics simulations to
compare the conformational dynamics of BM2 (a small α-helical
protein from the membrane of influenza B) in a model phospholipid
bilayer environment with its behavior in protein–detergent
complexes with either the zwitterionic detergent dihexanoylphosphatidylcholine
(DHPC) or the nonionic detergent dodecylmaltoside (DDM). We find that
DDM more closely resembles the lipid bilayer in terms of its interaction
with the protein, while the short-tailed DHPC molecule forms “nonphysiological”
interactions with the protein termini. We find that the intrinsic
micelle properties of each detergent are conserved upon formation
of the protein–detergent complex. This implies that simulations
of detergent micelles may be used to help select optimal conditions
for experimental studies of membrane proteins.
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Affiliation(s)
- Sarah L Rouse
- Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
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