1
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Vaknin A, Grossman A, Durham ND, Lupovitz I, Goren S, Golani G, Roichman Y, Munro JB, Sorkin R. Ebola Virus Glycoprotein Strongly Binds to Membranes in the Absence of Receptor Engagement. ACS Infect Dis 2024; 10:1590-1601. [PMID: 38684073 PMCID: PMC11091876 DOI: 10.1021/acsinfecdis.3c00622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 04/07/2024] [Accepted: 04/09/2024] [Indexed: 05/02/2024]
Abstract
Ebola virus (EBOV) is an enveloped virus that must fuse with the host cell membrane in order to release its genome and initiate infection. This process requires the action of the EBOV envelope glycoprotein (GP), encoded by the virus, which resides in the viral envelope and consists of a receptor binding subunit, GP1, and a membrane fusion subunit, GP2. Despite extensive research, a mechanistic understanding of the viral fusion process is incomplete. To investigate GP-membrane association, a key step in the fusion process, we used two approaches: high-throughput measurements of single-particle diffusion and single-molecule measurements with optical tweezers. Using these methods, we show that the presence of the endosomal Niemann-Pick C1 (NPC1) receptor is not required for primed GP-membrane binding. In addition, we demonstrate this binding is very strong, likely attributed to the interaction between the GP fusion loop and the membrane's hydrophobic core. Our results also align with previously reported findings, emphasizing the significance of acidic pH in the protein-membrane interaction. Beyond Ebola virus research, our approach provides a powerful toolkit for studying other protein-membrane interactions, opening new avenues for a better understanding of protein-mediated membrane fusion events.
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Affiliation(s)
- Alisa Vaknin
- School
of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
- Center
for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Alon Grossman
- School
of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
- Center
for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Natasha D. Durham
- Department
of Microbiology and Physiological Systems, University of Massachusetts Chan Medical School, Worcester, Massachusetts 01605, United States
| | - Inbal Lupovitz
- School
of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
- Center
for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Shahar Goren
- School
of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
- Center
for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Gonen Golani
- Department
of Physics and Haifa Research Center for Theoretical Physics and Astrophysics, University of Haifa, Haifa 3498838, Israel
| | - Yael Roichman
- School
of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
- Center
for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv 6997801, Israel
- Raymond
and Beverly Sackler School of Physics & Astronomy, Tel Aviv University, Tel Aviv 6997801, Israel
| | - James B. Munro
- Department
of Microbiology and Physiological Systems, University of Massachusetts Chan Medical School, Worcester, Massachusetts 01605, United States
- Department
of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, Massachusetts 01605, United States
| | - Raya Sorkin
- School
of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
- Center
for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv 6997801, Israel
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2
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Pennington H, Birtles D, Shi ZW, Lee J. A Salt Bridge and Disulfide Bond within the Lassa Virus Fusion Domain Are Required for the Initiation of Membrane Fusion. ACS OMEGA 2024; 9:4920-4930. [PMID: 38313535 PMCID: PMC10831964 DOI: 10.1021/acsomega.3c08632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 12/13/2023] [Accepted: 12/28/2023] [Indexed: 02/06/2024]
Abstract
Infection with Lassa virus (LASV), an Old-World arenavirus that is endemic to West Africa, causes Lassa fever, a lethal hemorrhagic fever. Delivery of LASV's genetic material into the host cell is an integral component of its lifecycle. This is accomplished via membrane fusion, a process initiated by a hydrophobic sequence known as the fusion domain (FD). The LASV FD (G260-N295) consists of two structurally distinct regions: an N-terminal fusion peptide (FP: G260-T274) and an internal fusion loop (FL: C279-N295) that is connected by a short linker region (P275-Y278). However, the molecular mechanisms behind how the LASV FD initiates fusion remain unclear. Here, we demonstrate that the LASV FD adopts a fusogenic, helical conformation at a pH akin to that of the lysosomal compartment. Additionally, we identified a conserved disulfide bond (C279 and C292) and salt bridge (R282 and E289) within the FL that are pertinent to fusion. We found that the disulfide bond must be present so that the FD can bind to the lipid bilayer and subsequently initiate fusion. Moreover, the salt bridge is essential for the secondary structure of the FD such that it can associate with the lipid bilayer in the proper orientation for full functionality. In conclusion, our findings indicate that the LASV FD preferentially initiates fusion at a pH akin to that of the lysosome through a mechanism that requires a conserved salt bridge and, to a lesser extent, an intact disulfide bond within the internal FL.
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Affiliation(s)
- Hallie
N. Pennington
- Department of Chemistry and
Biochemistry, College of Computer, Mathematics, and Natural Science, University of Maryland College Park, College Park, Maryland 20740, United States
| | - Daniel Birtles
- Department of Chemistry and
Biochemistry, College of Computer, Mathematics, and Natural Science, University of Maryland College Park, College Park, Maryland 20740, United States
| | - Zoe W. Shi
- Department of Chemistry and
Biochemistry, College of Computer, Mathematics, and Natural Science, University of Maryland College Park, College Park, Maryland 20740, United States
| | - Jinwoo Lee
- Department of Chemistry and
Biochemistry, College of Computer, Mathematics, and Natural Science, University of Maryland College Park, College Park, Maryland 20740, United States
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3
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Jain A, Govindan R, Berkman AR, Luban J, Díaz-Salinas MA, Durham ND, Munro JB. Regulation of Ebola GP conformation and membrane binding by the chemical environment of the late endosome. PLoS Pathog 2023; 19:e1011848. [PMID: 38055723 PMCID: PMC10727438 DOI: 10.1371/journal.ppat.1011848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 12/18/2023] [Accepted: 11/20/2023] [Indexed: 12/08/2023] Open
Abstract
Interaction between the Ebola virus envelope glycoprotein (GP) and the endosomal membrane is an essential step during virus entry into the cell. Acidic pH and Ca2+ have been implicated in mediating the GP-membrane interaction. However, the molecular mechanism by which these environmental factors regulate the conformational changes that enable engagement of GP with the target membrane is unknown. Here, we apply fluorescence correlation spectroscopy (FCS) and single-molecule Förster resonance energy transfer (smFRET) imaging to elucidate how the acidic pH, Ca2+ and anionic phospholipids in the late endosome promote GP-membrane interaction, thereby facilitating virus entry. We find that bis(monoacylglycero)phosphate (BMP), which is specific to the late endosome, is especially critical in determining the Ca2+-dependence of the GP-membrane interaction. Molecular dynamics (MD) simulations suggested residues in GP that sense pH and induce conformational changes that make the fusion loop available for insertion into the membrane. We similarly confirm residues in the fusion loop that mediate GP's interaction with Ca2+, which likely promotes local conformational changes in the fusion loop and mediates electrostatic interactions with the anionic phospholipids. Collectively, our results provide a mechanistic understanding of how the environment of the late endosome regulates the timing and efficiency of virus entry.
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Affiliation(s)
- Aastha Jain
- Department of Microbiology and Physiological Systems, UMass Chan Medical School, Worcester, Massachusetts, United States of America
| | - Ramesh Govindan
- Department of Microbiology and Physiological Systems, UMass Chan Medical School, Worcester, Massachusetts, United States of America
- Medical Scientist Training Program, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Alex R. Berkman
- Department of Microbiology and Physiological Systems, UMass Chan Medical School, Worcester, Massachusetts, United States of America
| | - Jeremy Luban
- Program in Molecular Medicine, UMass Chan Medical School, Worcester, Massachusetts, United States of America
- Department of Biochemistry and Molecular Biotechnology, UMass Chan Medical School, Worcester, Massachusetts, United States of America
| | - Marco A. Díaz-Salinas
- Department of Microbiology and Physiological Systems, UMass Chan Medical School, Worcester, Massachusetts, United States of America
| | - Natasha D. Durham
- Department of Microbiology and Physiological Systems, UMass Chan Medical School, Worcester, Massachusetts, United States of America
| | - James B. Munro
- Department of Microbiology and Physiological Systems, UMass Chan Medical School, Worcester, Massachusetts, United States of America
- Department of Biochemistry and Molecular Biotechnology, UMass Chan Medical School, Worcester, Massachusetts, United States of America
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4
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Abstract
There are at least 21 families of enveloped viruses that infect mammals, and many contain members of high concern for global human health. All enveloped viruses have a dedicated fusion protein or fusion complex that enacts the critical genome-releasing membrane fusion event that is essential before viral replication within the host cell interior can begin. Because all enveloped viruses enter cells by fusion, it behooves us to know how viral fusion proteins function. Viral fusion proteins are also major targets of neutralizing antibodies, and hence they serve as key vaccine immunogens. Here we review current concepts about viral membrane fusion proteins focusing on how they are triggered, structural intermediates between pre- and postfusion forms, and their interplay with the lipid bilayers they engage. We also discuss cellular and therapeutic interventions that thwart virus-cell membrane fusion.
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Affiliation(s)
- Judith M White
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia, USA;
| | - Amanda E Ward
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
| | - Laura Odongo
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
| | - Lukas K Tamm
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
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5
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Odongo L, Habtegebrael BH, Kiessling V, White JM, Tamm LK. A novel in vitro system of supported planar endosomal membranes (SPEMs) reveals an enhancing role for cathepsin B in the final stage of Ebola virus fusion and entry. Microbiol Spectr 2023; 11:e0190823. [PMID: 37728342 PMCID: PMC10581071 DOI: 10.1128/spectrum.01908-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 07/17/2023] [Indexed: 09/21/2023] Open
Abstract
Ebola virus (EBOV) causes a hemorrhagic fever with fatality rates up to 90%. The EBOV entry process is complex and incompletely understood. Following attachment to host cells, EBOV is trafficked to late endosomes/lysosomes where its glycoprotein (GP) is processed to a 19-kDa form, which binds to the EBOV intracellular receptor Niemann-Pick type C1. We previously showed that the cathepsin protease inhibitor, E-64d, blocks infection by pseudovirus particles bearing 19-kDa GP, suggesting that further cathepsin action is needed to trigger fusion. This, however, has not been demonstrated directly. Since 19-kDa Ebola GP fusion occurs in late endosomes, we devised a system in which enriched late endosomes are used to prepare supported planar endosomal membranes (SPEMs), and fusion of fluorescent (pseudo)virus particles is monitored by total internal reflection fluorescence microscopy. We validated the system by demonstrating the pH dependencies of influenza virus hemagglutinin (HA)-mediated and Lassa virus (LASV) GP-mediated fusion. Using SPEMs, we showed that fusion mediated by 19-kDa Ebola GP is dependent on low pH, enhanced by Ca2+, and augmented by the addition of cathepsins. Subsequently, we found that E-64d inhibits full fusion, but not lipid mixing, mediated by 19-kDa GP, which we corroborated with the reversible cathepsin inhibitor VBY-825. Hence, we provide both gain- and loss-of-function evidence that further cathepsin action enhances the fusion activity of 19-kDa Ebola GP. In addition to providing new insights into how Ebola GP mediates fusion, the approach we developed employing SPEMs can now be broadly used for studies of virus and toxin entry through endosomes. IMPORTANCE Ebola virus is the causative agent of Ebola virus disease, which is severe and frequently lethal. EBOV gains entry into cells via late endosomes/lysosomes. The events immediately preceding fusion of the viral and endosomal membranes are incompletely understood. In this study, we report a novel in vitro system for studying virus fusion with endosomal membranes. We validated the system by demonstrating the low pH dependencies of influenza and Lassa virus fusion. Moreover, we show that further cathepsin B action enhances the fusion activity of the primed Ebola virus glycoprotein. Finally, this model endosomal membrane system should be useful in studying the mechanisms of bilayer breaching by other enveloped viruses, by non-enveloped viruses, and by acid-activated bacterial toxins.
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Affiliation(s)
- Laura Odongo
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
| | - Betelihem H. Habtegebrael
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
| | - Volker Kiessling
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
| | - Judith M. White
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia, USA
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia, USA
| | - Lukas K. Tamm
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
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6
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Rayaprolu V, Fulton BO, Rafique A, Arturo E, Williams D, Hariharan C, Callaway H, Parvate A, Schendel SL, Parekh D, Hui S, Shaffer K, Pascal KE, Wloga E, Giordano S, Negron N, Ni M, Copin R, Atwal GS, Franklin M, Boytz RM, Donahue C, Davey R, Baum A, Kyratsous CA, Saphire EO. Structure of the Inmazeb cocktail and resistance to Ebola virus escape. Cell Host Microbe 2023; 31:260-272.e7. [PMID: 36708708 PMCID: PMC10375381 DOI: 10.1016/j.chom.2023.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 12/15/2022] [Accepted: 01/03/2023] [Indexed: 01/28/2023]
Abstract
Monoclonal antibodies can provide important pre- or post-exposure protection against infectious disease for those not yet vaccinated or in individuals that fail to mount a protective immune response after vaccination. Inmazeb (REGN-EB3), a three-antibody cocktail against Ebola virus, lessened disease and improved survival in a controlled trial. Here, we present the cryo-EM structure at 3.1 Å of the Ebola virus glycoprotein, determined without symmetry averaging, in a simultaneous complex with the antibodies in the Inmazeb cocktail. This structure allows the modeling of previously disordered portions of the glycoprotein glycan cap, maps the non-overlapping epitopes of Inmazeb, and illuminates the basis for complementary activities and residues critical for resistance to escape by these and other clinically relevant antibodies. We further provide direct evidence that Inmazeb protects against the rapid emergence of escape mutants, whereas monotherapies even against conserved epitopes do not, supporting the benefit of a cocktail versus a monotherapy approach.
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Affiliation(s)
| | | | | | - Emilia Arturo
- La Jolla Institute for Immunology, La Jolla, CA 92037, USA
| | - Dewight Williams
- Eyring Materials Center, Arizona State University, Tempe, AZ 85281, USA
| | | | | | - Amar Parvate
- La Jolla Institute for Immunology, La Jolla, CA 92037, USA
| | | | | | - Sean Hui
- La Jolla Institute for Immunology, La Jolla, CA 92037, USA
| | - Kelly Shaffer
- La Jolla Institute for Immunology, La Jolla, CA 92037, USA
| | | | | | | | | | - Min Ni
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | | | - Ruth Mabel Boytz
- Department of Microbiology, Boston University of Medicine and NEIDL, Boston University, Boston, MA 02118, USA
| | - Callie Donahue
- Department of Microbiology, Boston University of Medicine and NEIDL, Boston University, Boston, MA 02118, USA
| | - Robert Davey
- Department of Microbiology, Boston University of Medicine and NEIDL, Boston University, Boston, MA 02118, USA
| | - Alina Baum
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | - Erica Ollmann Saphire
- La Jolla Institute for Immunology, La Jolla, CA 92037, USA; Department of Medicine, University of California, San Diego, San Diego, CA 92037, USA.
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7
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Birtles D, Oh AE, Lee J. Exploring the
pH
dependence of the
SARS‐CoV
‐2 complete fusion domain and the role of its unique structural features. Protein Sci 2022. [PMCID: PMC9538437 DOI: 10.1002/pro.4390] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
SARS‐CoV‐2 may enter target cells through the process of membrane fusion at either the plasma (~pH 7.4–7.0) or endosomal (~pH 6.5–5.0) membrane in order to deliver its genetic information. The fusion domain (FD) of the spike glycoprotein is responsible for initiating fusion and is thus integral to the viral life cycle. The FD of SARS‐CoV‐2 is unique in that it consists of two structurally distinctive regions referred to as the fusion peptide (FP) and the fusion loop (FL); yet the molecular mechanisms behind how this FD perturbs the membrane to initiate fusion remains unclear. In this study via solution NMR, we witnessed only a slight conformational change in the FD between pH 7.4 and pH 5.0, resulting in a minor elongation of helix 1. However, we found that the FD's ability to mediate membrane fusion has a large and significant pH dependence, with fusion events being more readily induced at low pH. Interestingly, a biphasic relationship between the environmental pH and fusogenicity was discovered, suggesting a preference for the FD to initiate fusion at the late endosomal membrane. Furthermore, the conserved disulfide bond and hydrophobic motif “LLF” were found to be critical for the function of the complete FD, with minimal activity witnessed when either was perturbed. In conclusion, these findings indicate that the SARS‐CoV‐2 FD preferably initiates fusion at a pH similar to the late endosome through a mechanism that heavily relies on the internal disulfide bond of the FL and hydrophobic LLF motif within the FP.
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Affiliation(s)
- Daniel Birtles
- Department of Chemistry and Biochemistry University of Maryland College Park Maryland USA
| | - Anna E. Oh
- Department of Chemistry and Biochemistry University of Maryland College Park Maryland USA
| | - Jinwoo Lee
- Department of Chemistry and Biochemistry University of Maryland College Park Maryland USA
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8
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Zhang M, Wang X, Hu L, Zhang Y, Zheng H, Wu H, Wang J, Luo L, Xiao H, Qiao C, Li X, Huang W, Wang Y, Feng J, Chen G. TIM-1 Augments Cellular Entry of Ebola Virus Species and Mutants, Which Is Blocked by Recombinant TIM-1 Protein. Microbiol Spectr 2022; 10:e0221221. [PMID: 35384693 PMCID: PMC9241846 DOI: 10.1128/spectrum.02212-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 03/07/2022] [Indexed: 01/12/2023] Open
Abstract
Ebola virus, a member of the Filoviridae family, utilizes the attachment factors on host cells to support its entry and cause severe tissue damage. TIM-1 has been identified as a predominant attachment factor via interaction with phosphatidylserine (PS) localized on the viral envelope and glycoprotein (GP). In this study, we give the first demonstration that TIM-1 enhances the cellular entry of three species of Ebola virus, as well as those harboring GP mutations (A82V, T544I, and A82V T544I). Furthermore, two TIM-1 variants (i.e., TIM-1-359aa and TIM-1-364aa) had comparable effects on promoting Zaire Ebola virus (EBOV) attachment, internalization, and infection. Importantly, recombinant TIM-1 ectodomain (ECD) protein could decrease the infectivity of Ebola virus and display synergistic inhibitory effects with ADI-15946, a monoclonal antibody with broad neutralizing activity to Ebola virus. Of note, EBOV strains harboring GP mutations (K510E and D552N), which were refractory to antibody treatment, were still sensitive to TIM-1 protein-mediated impairment of infectivity, indicating that TIM-1 protein may represent an alternative therapeutic regimen when antibody evasion occurs. IMPORTANCE The viral genome has acquired numerous mutations with the potential to increase transmission during the 2013-to-2016 outbreak of Ebola virus. EBOV strains harboring GP mutations (A82V, T544I, and A82V T544I), which have been identified to increase viral infectivity in humans, have attracted our attention. Herein, we give the first report that polymorphic TIM-1 enhances the infectivity of three species of Ebola virus, as well as those harboring GP mutations (A82V, T544I, and A82V T544I). We show that recombinant TIM-1 ECD protein could decrease the infectivity of Ebola virus with or without a point mutation and displays synergistic inhibitory effects with ADI-15946. Furthermore, TIM-1 protein potently blocked cell entry of antibody-evading Ebola virus species. These findings highlight the role of TIM-1 in Ebola virus infection and indicate that TIM-1 protein represents a potential therapeutic avenue for Ebola virus and its mutated species.
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Affiliation(s)
- Min Zhang
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Beijing, China
| | - Xinwei Wang
- Inner Mongolia Key Lab of Molecular Biology, School of Basic Medical Sciences, Inner Mongolia Medical University, Hohhot, China
| | - Linhan Hu
- Inner Mongolia Key Lab of Molecular Biology, School of Basic Medical Sciences, Inner Mongolia Medical University, Hohhot, China
| | - Yuting Zhang
- Inner Mongolia Key Lab of Molecular Biology, School of Basic Medical Sciences, Inner Mongolia Medical University, Hohhot, China
| | - Hang Zheng
- Inner Mongolia Key Lab of Molecular Biology, School of Basic Medical Sciences, Inner Mongolia Medical University, Hohhot, China
| | - Haiyan Wu
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Beijing, China
| | - Jing Wang
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Beijing, China
| | - Longlong Luo
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Beijing, China
| | - He Xiao
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Beijing, China
| | - Chunxia Qiao
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Beijing, China
| | - Xinying Li
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Beijing, China
| | - Weijin Huang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, China
| | - Youchun Wang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, China
| | - Jiannan Feng
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Beijing, China
| | - Guojiang Chen
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Beijing, China
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9
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Tuerkova A, Kasson PM. Computational methods to study enveloped viral entry. Biochem Soc Trans 2021; 49:2527-2537. [PMID: 34783344 PMCID: PMC10184508 DOI: 10.1042/bst20210190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 10/25/2021] [Accepted: 10/27/2021] [Indexed: 12/15/2022]
Abstract
The protein-membrane interactions that mediate viral infection occur via loosely ordered, transient assemblies, creating challenges for high-resolution structure determination. Computational methods and in particular molecular dynamics simulation have thus become important adjuncts for integrating experimental data, developing mechanistic models, and suggesting testable hypotheses regarding viral function. However, the large molecular scales of virus-host interaction also create challenges for detailed molecular simulation. For this reason, continuum membrane models have played a large historical role, although they have become less favored for high-resolution models of protein assemblies and lipid organization. Here, we review recent progress in the field, with an emphasis on the insight that has been gained using a mixture of coarse-grained and atomic-resolution molecular dynamics simulations. Based on successes and challenges to date, we suggest a multiresolution strategy that should yield the best mixture of computational efficiency and physical fidelity. This strategy may facilitate further simulations of viral entry by a broader range of viruses, helping illuminate the diversity of viral entry strategies and the essential common elements that can be targeted for antiviral therapies.
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Affiliation(s)
- Alzbeta Tuerkova
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
| | - Peter M Kasson
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
- Departments of Molecular Physiology and Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, U.S.A
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10
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Hargreaves A, Brady C, Mellors J, Tipton T, Carroll MW, Longet S. Filovirus Neutralising Antibodies: Mechanisms of Action and Therapeutic Application. Pathogens 2021; 10:pathogens10091201. [PMID: 34578233 PMCID: PMC8468515 DOI: 10.3390/pathogens10091201] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/10/2021] [Accepted: 09/12/2021] [Indexed: 12/02/2022] Open
Abstract
Filoviruses, especially Ebola virus, cause sporadic outbreaks of viral haemorrhagic fever with very high case fatality rates in Africa. The 2013–2016 Ebola epidemic in West Africa provided large survivor cohorts spurring a large number of human studies which showed that specific neutralising antibodies played a key role in protection following a natural Ebola virus infection, as part of the overall humoral response and in conjunction with the cellular adaptive response. This review will discuss the studies in survivors and animal models which described protective neutralising antibody response. Their mechanisms of action will be detailed. Furthermore, the importance of neutralising antibodies in antibody-based therapeutics and in vaccine-induced responses will be explained, as well as the strategies to avoid immune escape from neutralising antibodies. Understanding the neutralising antibody response in the context of filoviruses is crucial to furthering our understanding of virus structure and function, in addition to improving current vaccines & antibody-based therapeutics.
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Affiliation(s)
- Alexander Hargreaves
- Nuffield Department of Medicine, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK; (A.H.); (C.B.); (J.M.); (T.T.); (M.W.C.)
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, UK
| | - Caolann Brady
- Nuffield Department of Medicine, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK; (A.H.); (C.B.); (J.M.); (T.T.); (M.W.C.)
| | - Jack Mellors
- Nuffield Department of Medicine, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK; (A.H.); (C.B.); (J.M.); (T.T.); (M.W.C.)
- National Infection Service, Public Health England, Porton Down, Salisbury SP4 0JG, UK
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Liverpool L69 7ZX, UK
| | - Tom Tipton
- Nuffield Department of Medicine, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK; (A.H.); (C.B.); (J.M.); (T.T.); (M.W.C.)
| | - Miles W. Carroll
- Nuffield Department of Medicine, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK; (A.H.); (C.B.); (J.M.); (T.T.); (M.W.C.)
- National Infection Service, Public Health England, Porton Down, Salisbury SP4 0JG, UK
| | - Stephanie Longet
- Nuffield Department of Medicine, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK; (A.H.); (C.B.); (J.M.); (T.T.); (M.W.C.)
- Correspondence: ; Tel.: +44-18-6561-7892
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11
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Zhao Z, Qin P, Huang YW. Lysosomal ion channels involved in cellular entry and uncoating of enveloped viruses: Implications for therapeutic strategies against SARS-CoV-2. Cell Calcium 2021; 94:102360. [PMID: 33516131 PMCID: PMC7825922 DOI: 10.1016/j.ceca.2021.102360] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 01/13/2021] [Accepted: 01/15/2021] [Indexed: 12/21/2022]
Abstract
Ion channels are necessary for correct lysosomal function including degradation of cargoes originating from endocytosis. Almost all enveloped viruses, including coronaviruses (CoVs), enter host cells via endocytosis, and do not escape endosomal compartments into the cytoplasm (via fusion with the endolysosomal membrane) unless the virus-encoded envelope proteins are cleaved by lysosomal proteases. With the ongoing outbreak of severe acute respiratory syndrome (SARS)-CoV-2, endolysosomal two-pore channels represent an exciting and emerging target for antiviral therapies. This review focuses on the latest knowledge of the effects of lysosomal ion channels on the cellular entry and uncoating of enveloped viruses, which may aid in development of novel therapies against emerging infectious diseases such as SARS-CoV-2.
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Affiliation(s)
- Zhuangzhuang Zhao
- Key Laboratory of Animal Virology of Ministry of Agriculture, Institute of Preventive Veterinary Medicine, Department of Veterinary Medicine, Zhejiang University, Hangzhou 310058, China
| | - Pan Qin
- Key Laboratory of Animal Virology of Ministry of Agriculture, Institute of Preventive Veterinary Medicine, Department of Veterinary Medicine, Zhejiang University, Hangzhou 310058, China
| | - Yao-Wei Huang
- Key Laboratory of Animal Virology of Ministry of Agriculture, Institute of Preventive Veterinary Medicine, Department of Veterinary Medicine, Zhejiang University, Hangzhou 310058, China.
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12
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A Glycoprotein Mutation That Emerged during the 2013-2016 Ebola Virus Epidemic Alters Proteolysis and Accelerates Membrane Fusion. mBio 2021; 12:mBio.03616-20. [PMID: 33593971 PMCID: PMC8545129 DOI: 10.1128/mbio.03616-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genomic surveillance of viral isolates during the 2013–2016 Ebola virus epidemic in Western Africa, the largest and most devastating filovirus outbreak on record, revealed several novel mutations. The responsible strain, named Makona, carries an A-to-V substitution at position 82 (A82V) in the glycoprotein (GP), which is associated with enhanced infectivity in vitro. Here, we investigated the mechanistic basis for this enhancement as well as the interplay between A82V and a T-to-I substitution at residue 544 of GP, which also modulates infectivity in cell culture. We found that both 82V and 544I destabilize GP, with the residue at position 544 impacting overall stability, while 82V specifically destabilizes proteolytically cleaved GP. Both residues also promote faster kinetics of lipid mixing of the viral and host membranes in live cells, individually and in tandem, which correlates with faster times to fusion following colocalization with the viral receptor Niemann-Pick C1 (NPC1). Furthermore, GPs bearing 82V are more sensitive to proteolysis by cathepsin L (CatL), a key host factor for viral entry. Intriguingly, CatL processed 82V variant GPs to a novel product with a molecular weight of approximately 12,000 (12K), which we hypothesize corresponds to a form of GP that is pre-triggered for fusion. We thus propose a model in which 82V promotes more efficient GP processing by CatL, leading to faster viral fusion kinetics and higher levels of infectivity.
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13
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Lee J, Kreutzberger AJB, Odongo L, Nelson EA, Nyenhuis DA, Kiessling V, Liang B, Cafiso DS, White JM, Tamm LK. Ebola virus glycoprotein interacts with cholesterol to enhance membrane fusion and cell entry. Nat Struct Mol Biol 2021; 28:181-189. [PMID: 33462517 PMCID: PMC7992113 DOI: 10.1038/s41594-020-00548-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 12/07/2020] [Indexed: 12/14/2022]
Abstract
Cholesterol serves critical roles in enveloped virus fusion by modulating membrane properties. The glycoprotein (GP) of Ebola virus (EBOV) promotes fusion in the endosome, a process that requires the endosomal cholesterol transporter NPC1. However, the role of cholesterol in EBOV fusion is unclear. Here we show that cholesterol in GP-containing membranes enhances fusion and the membrane-proximal external region and transmembrane (MPER/TM) domain of GP interacts with cholesterol via several glycine residues in the GP2 TM domain, notably G660. Compared to wild-type (WT) counterparts, a G660L mutation caused a more open angle between MPER and TM domains in an MPER/TM construct, higher probability of stalling at hemifusion for GP2 proteoliposomes and lower cell entry of virus-like particles (VLPs). VLPs with depleted cholesterol show reduced cell entry, and VLPs produced under cholesterol-lowering statin conditions show less frequent entry than respective controls. We propose that cholesterol-TM interactions affect structural features of GP2, thereby facilitating fusion and cell entry.
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Affiliation(s)
- Jinwoo Lee
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA
| | - Alex J B Kreutzberger
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| | - Laura Odongo
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| | - Elizabeth A Nelson
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Cell Biology, University of Virginia, Charlottesville, VA, USA
| | - David A Nyenhuis
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
| | - Volker Kiessling
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| | - Binyong Liang
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| | - David S Cafiso
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
| | - Judith M White
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Cell Biology, University of Virginia, Charlottesville, VA, USA
| | - Lukas K Tamm
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA.
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA.
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14
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Barfoot S, Poger D, Mark AE. Understanding the Activated Form of a Class-I Fusion Protein: Modeling the Interaction of the Ebola Virus Glycoprotein 2 with a Lipid Bilayer. Biochemistry 2020; 59:4051-4058. [PMID: 32960042 DOI: 10.1021/acs.biochem.0c00527] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The fusion of the viral and target cell membranes is a key step in the life cycle of all enveloped viruses. Here, a range of structural data is used to generate an evidence-based model of the active conformation of an archetypical type-I fusion protein, the Ebola glycoprotein 2 (GP2). The stability of the trimeric complex is demonstrated using molecular dynamics and validated by simulating the interaction of the complex with a lipid bilayer. In this model, the fusion peptides project away from the central helix bundle parallel to the target membrane. This maximizes contact with the host membrane, enhances lateral stability, and would explain why, when activated, viral fusion proteins are trimeric.
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Affiliation(s)
- Shelley Barfoot
- School of Chemistry & Molecular Biosciences, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - David Poger
- School of Chemistry & Molecular Biosciences, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Alan E Mark
- School of Chemistry & Molecular Biosciences, The University of Queensland, St Lucia, Queensland 4072, Australia
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15
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Liu N, Girvin ME, Brenowitz M, Lai JR. Conformational and lipid bilayer-perturbing properties of Marburg virus GP2 segments containing the fusion loop and membrane-proximal external region/transmembrane domain. Heliyon 2019; 5:e03018. [PMID: 31890962 PMCID: PMC6926192 DOI: 10.1016/j.heliyon.2019.e03018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 11/04/2019] [Accepted: 12/06/2019] [Indexed: 12/13/2022] Open
Abstract
Fusion of host and viral membranes is a crucial step during infection by enveloped viruses. In the structurally-defined "class I″ viral glycoproteins, the formation of a highly stable α-helical bundle by the ectodomain of the fusion subunit (e.g., GP2 for Marburg virus, MARV) is postulated to provide the energetic driving force to overcome barriers associated with membrane fusion. Upon cell binding, the fusion subunit is proposed to form an extended intermediate that bridges both the viral and host membranes, and collapse of this extended intermediate brings the two membranes into proximity. While there is much high-resolution structural data available for prefusion and post-fusion structures of viral glycoproteins, little information is available about intermediate conformations especially in the context of the fusion loop/peptide (FL or FP) and membrane-proximal external region (MPER)/transmembrane (TM) segments. We present structural and functional studies on segments of MARV GP2 that encompass the FL and MPER/TM in detergent micelles and lipid bicelles. A protein that contains most elements of GP2 ("MGP2-full") is α-helical in membrane-mimicking environments and has pH-dependent membrane lytic activity. MGP2-full is monomeric under such conditions, contrasting with the trimeric species that has been described previously for MARV GP2 ectodomain in aqueous buffer. Variants of MARV GP2 containing the N- and C-terminal halves ("MGP2-FNL" and "MGP2-CMT", respectively) have similar properties. This work provides novel insight into conformational and membrane-perturbing properties of the MARV fusion subunit and how they may relate to viral membrane fusion.
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Affiliation(s)
- Nina Liu
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Mark E Girvin
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Michael Brenowitz
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.,Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Jonathan R Lai
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
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16
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Fénéant L, Szymańska-de Wijs KM, Nelson EA, White JM. An exploration of conditions proposed to trigger the Ebola virus glycoprotein for fusion. PLoS One 2019; 14:e0219312. [PMID: 31276481 PMCID: PMC6611598 DOI: 10.1371/journal.pone.0219312] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 06/20/2019] [Indexed: 01/06/2023] Open
Abstract
Ebolaviruses continue to inflict horrific disease and instill fear. The 2013–2016 outbreak in Western Africa caused unfathomable morbidity and mortality (over 11,000 deaths), and the second largest outbreak is on-going in the Democratic Republic of the Congo. The first stage of an Ebolavirus infection is entry, culminating in delivery of the viral genome into the cytoplasm to initiate replication. Among enveloped viruses, Ebolaviruses use a complex entry pathway: they bind to attachment factors on cell surfaces, are engulfed by macropinocytosis, and traffic through the endosomal system. En route, the receptor binding subunit of the glycoprotein (GP) is reduced from ~130 to ~19 kDa by cathepsins. This event allows cleaved GP (GPcl) to bind to Niemann-Pick C1 (NPC1), its endosomal receptor. The virus then fuses with a late endosomal membrane, but how this occurs remains a subject of debate. An early, but standing, observation is that entry of particles bearing GPcl is inhibited by agents that raise endosomal pH or inhibit cysteine proteases, suggesting the need for an additional factor(s). Yet, some have concluded that NPC1 is sufficient to trigger the fusion activity of GPcl. Here, we re-examined this question using sensitive cell-cell and pseudovirus-cell fusion assays. We did not observe detectable GPcl-mediated fusion with NPC1 or its GPcl binding domain at any pH tested, while robust fusion was consistently observed with GP from lymphocytic choriomeningitis virus at low pH. Addition of proposed fusion-enhancing factors—cations (Ca++ and K+), a reducing agent, the anionic lipid Bis(Monoacylglycero)Phosphate, and a mixture of cathepsins B and L—did not induce detectable fusion. Our findings are in line with the earlier proposal that an additional factor is required to trigger the full fusion activity of GPcl after binding to NPC1. We discuss caveats to our study and what the missing factor(s) might be.
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Affiliation(s)
- Lucie Fénéant
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | | | - Elizabeth A. Nelson
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Judith M. White
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia, United States of America
- Department of Microbiology, University of Virginia, Charlottesville, Virginia, United States of America
- * E-mail:
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17
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Structural basis for broad neutralization of ebolaviruses by an antibody targeting the glycoprotein fusion loop. Nat Commun 2018; 9:3934. [PMID: 30258051 PMCID: PMC6158212 DOI: 10.1038/s41467-018-06113-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 08/17/2018] [Indexed: 11/09/2022] Open
Abstract
The severity of the 2014-2016 ebolavirus outbreak in West Africa expedited clinical development of therapeutics and vaccines though the countermeasures on hand were largely monospecific and lacked efficacy against other ebolavirus species that previously emerged. Recent studies indicate that ebolavirus glycoprotein (GP) fusion loops are targets for cross-protective antibodies. Here we report the 3.72 Å resolution crystal structure of one such cross-protective antibody, CA45, bound to the ectodomain of Ebola virus (EBOV) GP. The CA45 epitope spans multiple faces of the fusion loop stem, across both GP1 and GP2 subunits, with ~68% of residues identical across > 99.5% of known ebolavirus isolates. Extensive antibody interactions within a pan-ebolavirus small-molecule inhibitor binding cavity on GP define this cavity as a novel site of immune vulnerability. The structure elucidates broad ebolavirus neutralization through a highly conserved epitope on GP and further enables rational design and development of broadly protective vaccines and therapeutics.
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18
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Growth-Adaptive Mutations in the Ebola Virus Makona Glycoprotein Alter Different Steps in the Virus Entry Pathway. J Virol 2018; 92:JVI.00820-18. [PMID: 30021890 DOI: 10.1128/jvi.00820-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 07/08/2018] [Indexed: 01/01/2023] Open
Abstract
The Zaire ebolavirus (EBOV) glycoprotein (GP) is cleaved into two subunits (GP1 and GP2) that are both required for virus attachment and entry into cells. Sequence changes in the GP have been proposed to increase pathogenesis and to alter virus growth properties. Mutations in GP acquired during EBOV tissue culture passage have also been reported to change virus growth properties. Here, we report the isolation of six amino acid mutations in EBOV GP that spontaneously appeared during recovery and passage of an EBOV-Makona GP-pseudotyped vesicular stomatitis virus (VSV), two of which also occur during passage of EBOV clinical isolates in tissue culture. Each of the six mutations resulted in increased virus growth in monkey and human cell lines. All mutations are located in the GP2 fusion subunit and increase entry kinetics of EBOV virus-like particles (VLPs). The gain-of-entry function mapped to two mechanistic phenotypes. Mutations in heptad repeat 1 (HR1) decreased the requirement for cathepsin B activity for viral infection. Mutations directly within the fusion loop increased entry kinetics without altering the cathepsin B dependence. Several mutations in the fusion loop were substitutions of residues present in other ebolavirus glycoproteins, illustrating the evolutionary paths for maintaining an optimally functioning fusion loop under selection pressure.IMPORTANCEZaire ebolavirus (EBOV) is the causative agent of the highly lethal Ebola virus disease and poses a significant threat to the global health community. Approved antivirals against EBOV are lacking; however, promising therapies targeting the EBOV glycoprotein are being developed. Efficacy testing of these candidate therapeutics relies on EBOV laboratory stocks, which when grown in tissue culture may acquire mutations in the glycoprotein. These mutations can produce inaccurate results in therapeutic testing. Until recently, distinguishing between tissue culture mutations and naturally occurring polymorphisms in EBOV GP was difficult in the absence of consensus clinical GP sequences. Here, we utilize recombinant VSV (rVSV) pseudotyped with the consensus clinical EBOV Makona GP to identify several mutations that have emerged or have potential to emerge in EBOV GP during tissue culture passage. Identifying these mutations informs the EBOV research community as to which mutations may arise during preparation of laboratory virus stocks.
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19
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Hadden JA, Perilla JR. All-atom virus simulations. Curr Opin Virol 2018; 31:82-91. [PMID: 30181049 PMCID: PMC6456034 DOI: 10.1016/j.coviro.2018.08.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 08/04/2018] [Accepted: 08/13/2018] [Indexed: 12/11/2022]
Abstract
The constant threat of viral disease can be combated by the development of novel vaccines and therapeutics designed to disrupt key features of virus structure or infection cycle processes. Such development relies on high-resolution characterization of viruses and their dynamical behaviors, which are often challenging to obtain solely by experiment. In response, all-atom molecular dynamics simulations are widely leveraged to study the structural components of viruses, leading to some of the largest simulation endeavors undertaken to date. The present work reviews exemplary all-atom simulation work on viruses, as well as progress toward simulating entire virions.
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Affiliation(s)
- Jodi A Hadden
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States.
| | - Juan R Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
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20
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Fedewa G, Radoshitzky SR, Chī X, Dǒng L, Zeng X, Spear M, Strauli N, Ng M, Chandran K, Stenglein MD, Hernandez RD, Jahrling PB, Kuhn JH, DeRisi JL. Ebola virus, but not Marburg virus, replicates efficiently and without required adaptation in snake cells. Virus Evol 2018; 4:vey034. [PMID: 30524754 PMCID: PMC6277580 DOI: 10.1093/ve/vey034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Ebola virus (EBOV) disease is a viral hemorrhagic fever with a high case-fatality rate in humans. This disease is caused by four members of the filoviral genus Ebolavirus, including EBOV. The natural hosts reservoirs of ebolaviruses remain to be identified. Glycoprotein 2 of reptarenaviruses, known to infect only boa constrictors and pythons, is similar in sequence and structure to ebolaviral glycoprotein 2, suggesting that EBOV may be able to infect reptilian cells. Therefore, we serially passaged EBOV and a distantly related filovirus, Marburg virus (MARV), in boa constrictor JK cells and characterized viral infection/replication and mutational frequency by confocal imaging and sequencing. We observed that EBOV efficiently infected and replicated in JK cells, but MARV did not. In contrast to most cell lines, EBOV-infected JK cells did not result in an obvious cytopathic effect. Surprisingly, genomic characterization of serial-passaged EBOV in JK cells revealed that genomic adaptation was not required for infection. Deep sequencing coverage (>10,000×) demonstrated the existence of only a single nonsynonymous variant (EBOV glycoprotein precursor pre-GP T544I) of unknown significance within the viral population that exhibited a shift in frequency of at least 10 per cent over six serial passages. In summary, we present the first reptilian cell line that replicates a filovirus at high titers, and for the first time demonstrate a filovirus genus-specific restriction to MARV in a cell line. Our data suggest the possibility that there may be differences between the natural host spectra of ebolaviruses and marburgviruses.
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Affiliation(s)
- Greg Fedewa
- Integrative Program in Quantitative Biology, Bioinformatics, University of California San Francisco, San Francisco, CA, USA
| | - Sheli R Radoshitzky
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD, USA
| | - Xiǎolì Chī
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD, USA
| | - Lián Dǒng
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD, USA
| | - Xiankun Zeng
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD, USA
| | - Melissa Spear
- Biomedical Sciences Graduate Program, University of California San Francisco, San Francisco, CA, USA
| | - Nicolas Strauli
- Biomedical Sciences Graduate Program, University of California San Francisco, San Francisco, CA, USA
| | - Melinda Ng
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Kartik Chandran
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Mark D Stenglein
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
| | - Ryan D Hernandez
- Quantitative Biosciences Institute, University of California San Francisco, San Francisco, CA, USA
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Institute for Computational Health Sciences, University of California San Francisco, San Francisco, CA, USA
| | - Peter B Jahrling
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, MD, USA
| | - Jens H Kuhn
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, MD, USA
| | - Joseph L DeRisi
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
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21
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Kurosaki Y, Ueda MT, Nakano Y, Yasuda J, Koyanagi Y, Sato K, Nakagawa S. Different effects of two mutations on the infectivity of Ebola virus glycoprotein in nine mammalian species. J Gen Virol 2018; 99:181-186. [PMID: 29300152 PMCID: PMC5882082 DOI: 10.1099/jgv.0.000999] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Ebola virus (EBOV), which belongs to the genus Ebolavirus, causes a severe and often fatal infection in primates, including humans, whereas Reston virus (RESTV) only causes lethal disease in non-human primates. Two amino acids (aa) at positions 82 and 544 of the EBOV glycoprotein (GP) are involved in determining viral infectivity. However, it remains unclear how these two aa residues affect the infectivity of Ebolavirus species in various hosts. Here we performed viral pseudotyping experiments with EBOV and RESTV GP derivatives in 10 cell lines from 9 mammalian species. We demonstrated that isoleucine at position 544/545 increases viral infectivity in all host species, whereas valine at position 82/83 modulates viral infectivity, depending on the viral and host species. Structural modelling suggested that the former residue affects viral fusion, whereas the latter residue influences the interaction with the viral entry receptor, Niemann–Pick C1.
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Affiliation(s)
- Yohei Kurosaki
- Department of Emerging Infectious Diseases, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
| | - Mahoko Takahashi Ueda
- Micro/Nano Technology Center, Tokai University, 411 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan
| | - Yusuke Nakano
- Laboratory of Systems Virology, Department of Biosystems Science, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoinkawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
| | - Jiro Yasuda
- Department of Emerging Infectious Diseases, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.,Graduate School of Biomedical Sciences and Program for Nurturing Global Leaders in Tropical and Emerging Communicable Diseases, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
| | - Yoshio Koyanagi
- Laboratory of Systems Virology, Department of Biosystems Science, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoinkawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
| | - Kei Sato
- Laboratory of Systems Virology, Department of Biosystems Science, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoinkawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.,CREST, Japan Science and Technology Agency, Saitama 322-0012, Japan
| | - So Nakagawa
- Department of Molecular Life Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan.,Micro/Nano Technology Center, Tokai University, 411 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan
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22
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Structure of the Ebola virus envelope protein MPER/TM domain and its interaction with the fusion loop explains their fusion activity. Proc Natl Acad Sci U S A 2017; 114:E7987-E7996. [PMID: 28874543 DOI: 10.1073/pnas.1708052114] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Ebolavirus (EBOV), an enveloped filamentous RNA virus causing severe hemorrhagic fever, enters cells by macropinocytosis and membrane fusion in a late endosomal compartment. Fusion is mediated by the EBOV envelope glycoprotein GP, which consists of subunits GP1 and GP2. GP1 binds to cellular receptors, including Niemann-Pick C1 (NPC1) protein, and GP2 is responsible for low pH-induced membrane fusion. Proteolytic cleavage and NPC1 binding at endosomal pH lead to conformational rearrangements of GP2 that include exposing the hydrophobic fusion loop (FL) for insertion into the cellular target membrane and forming a six-helix bundle structure. Although major portions of the GP2 structure have been solved in pre- and postfusion states and although current models place the transmembrane (TM) and FL domains of GP2 in close proximity at critical steps of membrane fusion, their structures in membrane environments, and especially interactions between them, have not yet been characterized. Here, we present the structure of the membrane proximal external region (MPER) connected to the TM domain: i.e., the missing parts of the EBOV GP2 structure. The structure, solved by solution NMR and EPR spectroscopy in membrane-mimetic environments, consists of a helix-turn-helix architecture that is independent of pH. Moreover, the MPER region is shown to interact in the membrane interface with the previously determined structure of the EBOV FL through several critical aromatic residues. Mutation of aromatic and neighboring residues in both binding partners decreases fusion and viral entry, highlighting the functional importance of the MPER/TM-FL interaction in EBOV entry and fusion.
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23
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Ruedas JB, Ladner JT, Ettinger CR, Gummuluru S, Palacios G, Connor JH. Spontaneous Mutation at Amino Acid 544 of the Ebola Virus Glycoprotein Potentiates Virus Entry and Selection in Tissue Culture. J Virol 2017; 91:e00392-17. [PMID: 28539437 PMCID: PMC5651722 DOI: 10.1128/jvi.00392-17] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 05/11/2017] [Indexed: 11/20/2022] Open
Abstract
Ebolaviruses have a surface glycoprotein (GP1,2) that is required for virus attachment and entry into cells. Mutations affecting GP1,2 functions can alter virus growth properties. We generated a recombinant vesicular stomatitis virus encoding Ebola virus Makona variant GP1,2 (rVSV-MAK-GP) and observed emergence of a T544I mutation in the Makona GP1,2 gene during tissue culture passage in certain cell lines. The T544I mutation emerged within two passages when VSV-MAK-GP was grown on Vero E6, Vero, and BS-C-1 cells but not when it was passaged on Huh7 and HepG2 cells. The mutation led to a marked increase in virus growth kinetics and conferred a robust growth advantage over wild-type rVSV-MAK-GP on Vero E6 cells. Analysis of complete viral genomes collected from patients in western Africa indicated that this mutation was not found in Ebola virus clinical samples. However, we observed the emergence of T544I during serial passage of various Ebola Makona isolates on Vero E6 cells. Three independent isolates showed emergence of T544I from undetectable levels in nonpassaged virus or virus passaged once to frequencies of greater than 60% within a single passage, consistent with it being a tissue culture adaptation. Intriguingly, T544I is not found in any Sudan, Bundibugyo, or Tai Forest ebolavirus sequences. Furthermore, T544I did not emerge when we serially passaged recombinant VSV encoding GP1,2 from these ebolaviruses. This report provides experimental evidence that the spontaneous mutation T544I is a tissue culture adaptation in certain cell lines and that it may be unique for the species Zaire ebolavirusIMPORTANCE The Ebola virus (Zaire) species is the most lethal species of all ebolaviruses in terms of mortality rate and number of deaths. Understanding how the Ebola virus surface glycoprotein functions to facilitate entry in cells is an area of intense research. Recently, three groups independently identified a polymorphism in the Ebola glycoprotein (I544) that enhanced virus entry, but they did not agree in their conclusions regarding its impact on pathogenesis. Our findings here address the origins of this polymorphism and provide experimental evidence showing that it is the result of a spontaneous mutation (T544I) specific to tissue culture conditions, suggesting that it has no role in pathogenesis. We further show that this mutation may be unique to the species Zaire ebolavirus, as it does not occur in Sudan, Bundibugyo, and Tai Forest ebolaviruses. Understanding the mechanism behind this mutation can provide insight into functional differences that exist in culture conditions and among ebolavirus glycoproteins.
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Affiliation(s)
- John B Ruedas
- Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts, USA
- National Emerging Infectious Diseases Laboratories, Boston, Massachusetts, USA
| | - Jason T Ladner
- Center for Genome Sciences, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, USA
| | - Chelsea R Ettinger
- Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Suryaram Gummuluru
- Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Gustavo Palacios
- Center for Genome Sciences, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, USA
| | - John H Connor
- Department of Microbiology, Boston University School of Medicine, Boston, Massachusetts, USA
- National Emerging Infectious Diseases Laboratories, Boston, Massachusetts, USA
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25
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A Polymorphism within the Internal Fusion Loop of the Ebola Virus Glycoprotein Modulates Host Cell Entry. J Virol 2017; 91:JVI.00177-17. [PMID: 28228590 DOI: 10.1128/jvi.00177-17] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 02/15/2017] [Indexed: 12/12/2022] Open
Abstract
The large scale of the Ebola virus disease (EVD) outbreak in West Africa in 2013-2016 raised the question whether the host cell interactions of the responsible Ebola virus (EBOV) strain differed from those of other ebolaviruses. We previously reported that the glycoprotein (GP) of the virus circulating in West Africa in 2014 (EBOV2014) exhibited reduced ability to mediate entry into two nonhuman primate (NHP)-derived cell lines relative to the GP of EBOV1976. Here, we investigated the molecular determinants underlying the differential entry efficiency. We found that EBOV2014-GP-driven entry into diverse NHP-derived cell lines, as well as human monocyte-derived macrophages and dendritic cells, was reduced compared to EBOV1976-GP, although entry into most human- and all bat-derived cell lines tested was comparable. Moreover, EBOV2014 replication in NHP but not human cells was diminished relative to EBOV1976, suggesting that reduced cell entry translated into reduced viral spread. Mutagenic analysis of EBOV2014-GP and EBOV1976-GP revealed that an amino acid polymorphism in the receptor-binding domain, A82V, modulated entry efficiency in a cell line-independent manner and did not account for the reduced EBOV2014-GP-driven entry into NHP cells. In contrast, polymorphism T544I, located in the internal fusion loop in the GP2 subunit, was found to be responsible for the entry phenotype. These results suggest that position 544 is an important determinant of EBOV infectivity for both NHP and certain human target cells.IMPORTANCE The Ebola virus disease outbreak in West Africa in 2013 entailed more than 10,000 deaths. The scale of the outbreak and its dramatic impact on human health raised the question whether the responsible virus was particularly adept at infecting human cells. Our study shows that an amino acid exchange, A82V, that was acquired during the epidemic and that was not observed in previously circulating viruses, increases viral entry into diverse target cells. In contrast, the epidemic virus showed a reduced ability to enter cells of nonhuman primates compared to the virus circulating in 1976, and a single amino acid exchange in the internal fusion loop of the viral glycoprotein was found to account for this phenotype.
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26
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Liang J, Jangra RK, Bollinger L, Wada J, Radoshitzky SR, Chandran K, Jahrling PB, Kuhn JH, Jensen KS. Candidate medical countermeasures targeting Ebola virus cell entry. Future Virol 2017. [DOI: 10.2217/fvl-2016-0113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Medical countermeasures (MCMs) against virus infections ideally prevent the adsorption or entry of virions into target cells, thereby circumventing infection. Recent significant advances in elucidating the mechanism of Ebola virus (EBOV) host-cell penetration include the involvement of two-pore channels at the early stage of entry, and identification of cellular proteases for EBOV spike glycoprotein maturation and the intracellular EBOV receptor, Niemann–Pick type C1. This improved understanding of the initial steps of EBOV infection is now increasingly applied to rapid development of candidate MCMs, some of which have already entered the clinic. Candidate MCMs discussed include antibodies, small molecules and peptides that target various stages of the described EBOV cell-entry pathway. In this review, we summarize the currently known spectrum of EBOV cell-entry inhibitors, describe their mechanism of action and evaluate their potential for future development.
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Affiliation(s)
- Janie Liang
- Integrated Research Facility at Fort Detrick, National Institute of Allergy & Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, MD, USA
| | - Rohit K Jangra
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Laura Bollinger
- Integrated Research Facility at Fort Detrick, National Institute of Allergy & Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, MD, USA
| | - Jiro Wada
- Integrated Research Facility at Fort Detrick, National Institute of Allergy & Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, MD, USA
| | - Sheli R Radoshitzky
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD, USA
| | - Kartik Chandran
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Peter B Jahrling
- Integrated Research Facility at Fort Detrick, National Institute of Allergy & Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, MD, USA
| | - Jens H Kuhn
- Integrated Research Facility at Fort Detrick, National Institute of Allergy & Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, MD, USA
| | - Kenneth S Jensen
- Integrated Research Facility at Fort Detrick, National Institute of Allergy & Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, MD, USA
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27
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Wang MK, Lim SY, Lee SM, Cunningham JM. Biochemical Basis for Increased Activity of Ebola Glycoprotein in the 2013-16 Epidemic. Cell Host Microbe 2017; 21:367-375. [PMID: 28238624 DOI: 10.1016/j.chom.2017.02.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 01/12/2017] [Accepted: 02/03/2017] [Indexed: 11/28/2022]
Abstract
Ebola virus (EBOV) infection is characterized by sporadic outbreaks caused by zoonotic transmission. Fixed changes in amino acid sequence, such as A82V in the EBOV glycoprotein (GP) that occurred early in the 2013-16 epidemic, are suspected to confer a selective advantage to the virus. We used biochemical assays of GP function to show that A82V, as well as a polymorphism in residue 544 identified in other outbreaks, enhances infection by decreasing the threshold for activation of membrane fusion activity triggered by the host factors cathepsin B and Niemann-Pick C1. Importantly, the increase in infectivity comes with the cost of decreased virus stability. Thus, emergence of a virus GP with altered properties that can affect transmission and virulence may have contributed to the severity and scope of the 2013-16 EBOV epidemic.
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Affiliation(s)
- May K Wang
- Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA
| | - Sun-Young Lim
- Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Soo Mi Lee
- Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - James M Cunningham
- Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA.
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28
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Ueda MT, Kurosaki Y, Izumi T, Nakano Y, Oloniniyi OK, Yasuda J, Koyanagi Y, Sato K, Nakagawa S. Functional mutations in spike glycoprotein of Zaire ebolavirus associated with an increase in infection efficiency. Genes Cells 2017; 22:148-159. [PMID: 28084671 DOI: 10.1111/gtc.12463] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 11/29/2016] [Indexed: 01/23/2023]
Abstract
Ebola virus (EBOV) is extremely virulent, and its glycoprotein is necessary for viral entry. EBOV may adapt to its new host humans during outbreaks by acquiring mutations especially in glycoprotein, which allows EBOV to spread more efficiently. To identify these evolutionary selected mutations and examine their effects on viral infectivity, we used experimental-phylogenetic-structural interdisciplinary approaches. In evolutionary analysis of all available Zaire ebolavirus glycoprotein sequences, we detected two codon sites under positive selection, which are located near/within the region critical for the host-viral membrane fusion, namely alanine-to-valine and threonine-to-isoleucine mutations at 82 (A82V) and 544 (T544I), respectively. The fine-scale transmission dynamics of EBOV Makona variants that caused the 2014-2015 outbreak showed that A82V mutant was fixed in the population, whereas T544I was not. Furthermore, pseudotype assays for the Makona glycoprotein showed that the A82V mutation caused a small increase in viral infectivity compared with the T544I mutation. These findings suggest that mutation fixation in EBOV glycoprotein may be associated with their increased infectivity levels; the mutant with a moderate increase in infectivity will fix. Our findings showed that a driving force for Ebola virus evolution via glycoprotein may be a balance between costs and benefits of its virulence.
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Affiliation(s)
- Mahoko Takahashi Ueda
- Micro/Nano Technology Center, Tokai University, 411 Kitakaname, Hiratsuka, Kanagawa, 259-1193, Japan
| | - Yohei Kurosaki
- Department of Emerging Infectious Diseases, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan
| | - Taisuke Izumi
- Laboratory of Systems Virology, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoinkawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.,CREST, Japan Science and Technology Agency, Saitama, 322-0012, Japan
| | - Yusuke Nakano
- Laboratory of Systems Virology, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoinkawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Olamide K Oloniniyi
- Department of Emerging Infectious Diseases, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan.,Graduate School of Biomedical Sciences and Program for Nurturing Global Leaders in Tropical and Emerging Communicable Diseases, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan
| | - Jiro Yasuda
- Department of Emerging Infectious Diseases, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan.,Graduate School of Biomedical Sciences and Program for Nurturing Global Leaders in Tropical and Emerging Communicable Diseases, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan
| | - Yoshio Koyanagi
- Laboratory of Systems Virology, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoinkawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan
| | - Kei Sato
- Laboratory of Systems Virology, Institute for Frontier Life and Medical Sciences, Kyoto University, 53 Shogoinkawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.,CREST, Japan Science and Technology Agency, Saitama, 322-0012, Japan
| | - So Nakagawa
- Micro/Nano Technology Center, Tokai University, 411 Kitakaname, Hiratsuka, Kanagawa, 259-1193, Japan.,Department of Molecular Life Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan
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29
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Davey RA, Shtanko O, Anantpadma M, Sakurai Y, Chandran K, Maury W. Mechanisms of Filovirus Entry. Curr Top Microbiol Immunol 2017; 411:323-352. [PMID: 28601947 DOI: 10.1007/82_2017_14] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Filovirus entry into cells is complex, perhaps as complex as any viral entry mechanism identified to date. However, over the past 10 years, the important events required for filoviruses to enter into the endosomal compartment and fuse with vesicular membranes have been elucidated (Fig. 1). Here, we highlight the important steps that are required for productive entry of filoviruses into mammalian cells.
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Affiliation(s)
- R A Davey
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - O Shtanko
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - M Anantpadma
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - Y Sakurai
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - K Chandran
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - W Maury
- Department of Microbiology, The University of Iowa, Iowa City, IA, USA.
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30
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White JM, Whittaker GR. Fusion of Enveloped Viruses in Endosomes. Traffic 2016; 17:593-614. [PMID: 26935856 PMCID: PMC4866878 DOI: 10.1111/tra.12389] [Citation(s) in RCA: 281] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Revised: 02/25/2016] [Accepted: 02/25/2016] [Indexed: 12/12/2022]
Abstract
Ari Helenius launched the field of enveloped virus fusion in endosomes with a seminal paper in the Journal of Cell Biology in 1980. In the intervening years, a great deal has been learned about the structures and mechanisms of viral membrane fusion proteins as well as about the endosomes in which different enveloped viruses fuse and the endosomal cues that trigger fusion. We now recognize three classes of viral membrane fusion proteins based on structural criteria and four mechanisms of fusion triggering. After reviewing general features of viral membrane fusion proteins and viral fusion in endosomes, we delve into three characterized mechanisms for viral fusion triggering in endosomes: by low pH, by receptor binding plus low pH and by receptor binding plus the action of a protease. We end with a discussion of viruses that may employ novel endosomal fusion‐triggering mechanisms. A key take‐home message is that enveloped viruses that enter cells by fusing in endosomes traverse the endocytic pathway until they reach an endosome that has all of the environmental conditions (pH, proteases, ions, intracellular receptors and lipid composition) to (if needed) prime and (in all cases) trigger the fusion protein and to support membrane fusion.
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Affiliation(s)
- Judith M White
- Department of Cell Biology, University of Virginia, Charlottesville, VA, USA
| | - Gary R Whittaker
- Department of Microbiology & Immunology, Cornell University, Ithaca, NY, USA
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31
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Lee J, Gregory SM, Nelson EA, White JM, Tamm LK. The Roles of Histidines and Charged Residues as Potential Triggers of a Conformational Change in the Fusion Loop of Ebola Virus Glycoprotein. PLoS One 2016; 11:e0152527. [PMID: 27023721 PMCID: PMC4811418 DOI: 10.1371/journal.pone.0152527] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 03/15/2016] [Indexed: 11/23/2022] Open
Abstract
Ebola virus (EBOV) enters cells from late endosomes/lysosomes under mildly acidic conditions. Entry by fusion with the endosomal membrane requires the fusion loop (FL, residues 507–560) of the EBOV surface glycoprotein to undergo a pH-dependent conformational change. To find the pH trigger for this reaction we mutated multiple conserved histidines and charged and uncharged hydrophilic residues in the FL and measured their activity by liposome fusion and cell entry of virus-like particles. The FL location in the membrane was assessed by NMR using soluble and lipid-bound paramagnetic relaxation agents. While we could not identify a single residue to be alone responsible for pH triggering, we propose that a distributed pH effect over multiple residues induces the conformational change that enhances membrane insertion and triggers the fusion activity of the EBOV FL.
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Affiliation(s)
- Jinwoo Lee
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia 22908, United States of America.,Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, United States of America
| | - Sonia M Gregory
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia 22908, United States of America.,Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, United States of America
| | - Elizabeth A Nelson
- Department Cell Biology, University of Virginia, Charlottesville, Virginia 22908, United States of America
| | - Judith M White
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia 22908, United States of America.,Department Cell Biology, University of Virginia, Charlottesville, Virginia 22908, United States of America
| | - Lukas K Tamm
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia 22908, United States of America.,Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, United States of America
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32
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Spence JS, Krause TB, Mittler E, Jangra RK, Chandran K. Direct Visualization of Ebola Virus Fusion Triggering in the Endocytic Pathway. mBio 2016; 7:e01857-15. [PMID: 26861015 PMCID: PMC4752599 DOI: 10.1128/mbio.01857-15] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 01/07/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Ebola virus (EBOV) makes extensive and intricate use of host factors in the cellular endosomal/lysosomal pathway to release its genome into the cytoplasm and initiate infection. Following viral internalization into endosomes, host cysteine proteases cleave the EBOV fusion glycoprotein (GP) to unmask the binding site for its intracellular receptor, the cholesterol transporter Niemann-Pick C1 (NPC1). GP-NPC1 interaction is required for viral entry. Despite these and other recent discoveries, late events in EBOV entry following GP-NPC1 binding and culminating in GP-catalyzed fusion between viral and cellular lipid bilayers remain enigmatic. A mechanistic understanding of EBOV membrane fusion has been hampered by the failure of previous efforts to reconstitute fusion in vitro or at the cell surface. This report describes an assay to monitor initial steps directly in EBOV membrane fusion-triggering of GP and virus-cell lipid mixing-by single virions in live cells. Fusogenic triggering of GP occurs predominantly in Rab7-positive (Rab7(+)) endosomes, absolutely requires interaction between proteolytically primed GP and NPC1, and is blocked by key GP-specific neutralizing antibodies with therapeutic potential. Unexpectedly, cysteine protease inhibitors do not inhibit lipid mixing by virions bearing precleaved GP, even though they completely block cytoplasmic entry by these viruses, as shown previously. These results point to distinct cellular requirements for different steps in EBOV membrane fusion and suggest a model in which host cysteine proteases are dispensable for GP fusion triggering after NPC1 binding but are required for the formation of fusion pores that permit genome delivery. IMPORTANCE Ebola virus (EBOV) causes outbreaks of highly lethal disease for which no approved vaccines or treatments exist. Recent work has elucidated key molecular features of the complex EBOV entry process, including stepwise interactions with multiple host factors. However, there is a critical gap in our understanding of events that surround the final membrane fusion step which persists due to the paucity of direct and extensive investigation of EBOV fusion. Here, we report a real-time assay for EBOV glycoprotein fusion triggering and use it to define its cellular location and requirements. We also uncover an unexpected requirement for host proteases at a step after fusion triggering that may reflect their role in formation of fusion pores for genome delivery.
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Affiliation(s)
- Jennifer S Spence
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Tyler B Krause
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Eva Mittler
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Rohit K Jangra
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Kartik Chandran
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA
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33
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Risselada HJ. Simulations move toward a cure for viral diseases. Structure 2015; 23:439-440. [PMID: 25738384 DOI: 10.1016/j.str.2015.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
In this issue of Structure, Reddy and colleagues combined various experimental data to build a realistic near-atomic model of the complete lipidic influenza A virion. Here, we illustrate the advances made by this pioneering simulation study and discuss ongoing challenges.
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Affiliation(s)
- Herre Jelger Risselada
- Department of Chemistry, Leibniz Institute of Surface Modification, 04318 Leipzig, Germany.
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34
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Ebolavirus Glycoprotein Directs Fusion through NPC1+ Endolysosomes. J Virol 2015; 90:605-10. [PMID: 26468524 PMCID: PMC4702577 DOI: 10.1128/jvi.01828-15] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2015] [Accepted: 10/06/2015] [Indexed: 12/31/2022] Open
Abstract
Ebolavirus, a deadly hemorrhagic fever virus, was thought to enter cells through endolysosomes harboring its glycoprotein receptor, Niemann-Pick C1. However, an alternate model was recently proposed in which ebolavirus enters through a later NPC1-negative endosome that contains two-pore Ca(2+) channel 2 (TPC2), a newly identified ebolavirus entry factor. Here, using live cell imaging, we obtained evidence that in contrast to the new model, ebolavirus enters cells through endolysosomes that contain both NPC1 and TPC2.
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35
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Rhein BA, Maury WJ. Ebola virus entry into host cells: identifying therapeutic strategies. CURRENT CLINICAL MICROBIOLOGY REPORTS 2015; 2:115-124. [PMID: 26509109 PMCID: PMC4617201 DOI: 10.1007/s40588-015-0021-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Filoviruses cause severe hemorrhagic fever in humans. The archetypal virus of this group, Ebola virus, is responsible for the current filovirus epidemic in West Africa. Filoviruses infect most mammalian cells, resulting in broad species tropism and likely contributing to rapid spread of virus throughout the body. A thorough understanding of filovirus entry events will facilitate the development of therapeutics against these critical steps in the viral life cycle. This review summarizes the current understanding of filovirus entry and discusses some of the recent advancements in therapeutic strategies that target entry.
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Affiliation(s)
- Bethany A. Rhein
- Department of Microbiology, University of Iowa, 3-701 Bowen Science Building, 51 Newton Rd, Iowa City, IA 52242 USA
| | - Wendy J. Maury
- Department of Microbiology, University of Iowa, 3-701 Bowen Science Building, 51 Newton Rd, Iowa City, IA 52242 USA
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36
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Affiliation(s)
- Sven Moller-Tank
- Department of Microbiology, University of Iowa, Iowa City, Iowa, United States of America
- Gene Therapy Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Wendy Maury
- Gene Therapy Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail:
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37
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Liu N, Tao Y, Brenowitz MD, Girvin ME, Lai JR. Structural and Functional Studies on the Marburg Virus GP2 Fusion Loop. J Infect Dis 2015; 212 Suppl 2:S146-53. [PMID: 25786917 DOI: 10.1093/infdis/jiv030] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Marburg virus (MARV) and the ebolaviruses belong to the family Filoviridae (the members of which are filoviruses) that cause severe hemorrhagic fever. Infection requires fusion of the host and viral membranes, a process that occurs in the host cell endosomal compartment and is facilitated by the envelope glycoprotein fusion subunit, GP2. The N-terminal fusion loop (FL) of GP2 is a hydrophobic disulfide-bonded loop that is postulated to insert and disrupt the host endosomal membrane during fusion. Here, we describe the first structural and functional studies of a protein corresponding to the MARV GP2 FL. We found that this protein undergoes a pH-dependent conformational change, as monitored by circular dichroism and nuclear magnetic resonance. Furthermore, we report that, under low pH conditions, the MARV GP2 FL can induce content leakage from liposomes. The general aspects of this pH-dependent structure and lipid-perturbing behavior are consistent with previous reports on Ebola virus GP2 FL. However, nuclear magnetic resonance studies in lipid bicelles and mutational analysis indicate differences in structure exist between MARV and Ebola virus GP2 FL. These results provide new insight into the mechanism of MARV GP2-mediated cell entry.
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Affiliation(s)
- Nina Liu
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York
| | - Yisong Tao
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York
| | - Michael D Brenowitz
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York
| | - Mark E Girvin
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York
| | - Jonathan R Lai
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York
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38
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Abstract
Ebola virus is an enveloped virus with filamentous structure and causes a severe hemorrhagic fever in human and nonhuman primates. Host cell entry is the first essential step in the viral life cycle, which has been extensively studied as one of the therapeutic targets. A virus factor of cell entry is a surface glycoprotein (GP), which is an only essential viral protein in the step, as well as the unique particle structure. The virus also interacts with a lot of host factors to successfully enter host cells. Ebola virus at first binds to cell surface proteins and internalizes into cells, followed by trafficking through endosomal vesicles to intracellular acidic compartments. There, host proteases process GPs, which can interact with an intracellular receptor. Then, under an appropriate circumstance, viral and endosomal membranes are fused, which is enhanced by major structural changes of GPs, to complete host cell entry. Recently the basic research of Ebola virus infection mechanism has markedly progressed, largely contributed by identification of host factors and detailed structural analyses of GPs. This article highlights the mechanism of Ebola virus host cell entry, including recent findings.
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Mahajan M, Bhattacharjya S. NMR structures and localization of the potential fusion peptides and the pre-transmembrane region of SARS-CoV: Implications in membrane fusion. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:721-30. [PMID: 25475644 PMCID: PMC7094234 DOI: 10.1016/j.bbamem.2014.11.025] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 11/06/2014] [Accepted: 11/10/2014] [Indexed: 12/26/2022]
Abstract
Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) poses a serious public health hazard. The S2 subunit of the S glycoprotein of SARS-CoV carries out fusion between the virus and the host cells. However, the exact mechanism of the cell fusion process is not well understood. Current model suggests that a conformational transition, upon receptor recognition, of the two heptad core regions of S2 may expose the hydrophobic fusogenic peptide or fusion peptide for membrane insertion. Three regions of the S2 subunit have been proposed to be involved in cell-cell fusion. The N-terminal fusion peptide (FP, residues 770-788), an internal fusion peptide (IFP, residues 873-888) and the pre-transmembrane region (PTM, residues 1185-1202) demonstrated interactions with model lipid membranes and potentially involved in the fusion process. Here, we have determined atomic resolution structures of these three peptides in DPC detergent micelles by solution NMR. FP assumes α-helical conformation with significant distortion at the central Gly residues; enabling a close packing among sidechains of aromatic residues including W, Y and F. The 3-D structure of PMT is characterized by a helix-loop-helix with extensive aromatic interactions within the helices. IFP adopts a rather straight α-helical conformation defined by packing among sidechains of aromatic and aliphatic residues. Paramagnetic spin labeled NMR has demonstrated surface localization of PMT whereas FP and IFP inserted into the micelles. Collectively, data presented in this study will aid in understanding fusion mechanism of SARS-CoV.
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Affiliation(s)
- Mukesh Mahajan
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Surajit Bhattacharjya
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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