Entry mechanisms of enveloped viruses. Implications for fusion of intracellular membranes

1989 ◽  
Vol 9 (3) ◽  
pp. 273-305 ◽  
Author(s):  
Dick Hoekstra ◽  
Jan Willem Kok
Keyword(s):  
Membrane Fusion ◽  
Membrane Glycoproteins ◽  
Enveloped Viruses ◽  
Viral Membrane ◽  
Intracellular Membranes ◽  
Virus Fusion ◽  
Specific Proteins ◽  
Intracellular Organelles

Enveloped viruses infect cells by a mechanism involving membrane fusion. This process is mediated and triggered by specific viral membrane glycoproteins. Evidence is accumulating that fusion of intracellular membranes, as occurs during endocytosis and transport between intracellular organelles, also requires the presence of specific proteins. The relevance of elucidating the mechanisms of virus fusion for a better understanding of fusion of intracellular membranes is discussed.

scholarly journals Surfactin Inhibits Membrane Fusion during Invasion of Epithelial Cells by Enveloped Viruses

2018 ◽  
Vol 92 (21) ◽  
Author(s):  
Lvfeng Yuan ◽  
Shuai Zhang ◽  
Yongheng Wang ◽  
Yuchen Li ◽  
Xiaoqing Wang ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Oral Administration ◽  
Membrane Fusion ◽  
Lipid Membrane ◽  
Antiviral Drugs ◽  
Fusion Inhibitor ◽  
Enveloped Viruses ◽  
Viral Membrane ◽  
Fusion Inhibitors ◽  
Naturally Occurring

ABSTRACT Because membrane fusion is a crucial step in the process by which enveloped viruses invade host cells, membrane fusion inhibitors can be effective drugs against enveloped viruses. We found that surfactin from Bacillus subtilis can suppress the proliferation of porcine epidemic diarrhea virus (PEDV) and transmissible gastroenteritis virus (TGEV) in epithelial cells at a relatively low concentration range (15 to 50 μg/ml), without cytotoxicity or viral membrane disruption. Membrane fusion inhibition experiments demonstrate that surfactin treatment significantly reduces the rate at which the virus fuses to the cell membrane. Thermodynamic experiments show that the incorporation of small amounts of surfactin hinders the formation of negative curvature by lamellar-phase lipids, suggesting that surfactin acts a membrane fusion inhibitor. A fluorescent lipopeptide similar to surfactin was synthesized, and its ability to insert into the viral membrane was confirmed by spectroscopy. In vivo experiments have shown that oral administration of surfactin to piglets protects against PEDV infection. In conclusion, our study indicates that surfactin is a membrane fusion inhibitor with activity against enveloped viruses. As the first reported naturally occurring wedge lipid membrane fusion inhibitor, surfactin is likely to be a prototype for the development of a broad range of novel antiviral drugs. IMPORTANCE Membrane fusion inhibitors are a rapidly emerging class of antiviral drugs that inhibit the infection process of enveloped viruses. They can be classified, on the basis of the viral components targeted, as fusion protein targeting or membrane lipid targeting. Lipid-targeting membrane fusion inhibitors have a broader antiviral spectrum and are less likely to select for drug-resistant mutations. Here we show that surfactin is a membrane fusion inhibitor and has a strong antiviral effect. The insertion of surfactin into the viral envelope lipids reduces the probability of viral fusion. We also demonstrate that oral administration of surfactin protects piglets from PEDV infection. Surfactin is the first naturally occurring wedge lipid membrane fusion inhibitor that has been identified and may be effective against many viruses beyond the scope of this study. Understanding its mechanism of action provides a foundation for the development of novel antiviral agents.

scholarly journals Precise Triggering and Chemical Control of Single-Virus Fusion within Endosomes

2020 ◽  
Vol 95 (1) ◽  
Author(s):  
Sourav Haldar ◽  
Kenta Okamoto ◽  
Rebecca A. Dunning ◽  
Peter M. Kasson
Keyword(s):  
Influenza Virus ◽  
Membrane Fusion ◽  
Influenza A ◽  
Living Cells ◽  
Membrane Curvature ◽  
Endosomal Trafficking ◽  
Viral Fusion ◽  
Enveloped Viruses ◽  
Endosomal Membrane ◽  
Virus Fusion

ABSTRACT Many enveloped viruses infect cells within endocytic compartments. The pH drop that accompanies endosomal maturation, often in conjunction with proteolysis, triggers viral proteins to insert into the endosomal membrane and drive fusion. Fusion dynamics have been studied by tracking viruses within living cells, which limits the precision with which fusion can be synchronized and controlled, and reconstituting viral fusion to synthetic membranes, which introduces nonphysiological membrane curvature and composition. To overcome these limitations, we report chemically controllable triggering of single-virus fusion within endosomes. We isolated influenza (A/Aichi/68; H3N2) virus:endosome conjugates from cells, immobilized them in a microfluidic flow cell, and rapidly and controllably triggered fusion. Observed lipid-mixing kinetics were surprisingly similar to those of influenza virus fusion with model membranes of opposite curvature: 80% of single-virus events had indistinguishable kinetics. This result suggests that endosomal membrane curvature is not a key permissive feature for viral entry, at least lipid mixing. The assay preserved endosomal membrane asymmetry and protein composition, providing a platform to test how cellular restriction factors and altered endosomal trafficking affect viral membrane fusion. IMPORTANCE Many enveloped viruses infect cells via fusion to endosomes, but controlling this process within living cells has been challenging. We studied the fusion of influenza virus virions to endosomes in a chemically controllable manner. Extracting virus:endosome conjugates from cells and exogenously triggering fusion permits precise study of virus:endosome fusion kinetics. Surprisingly, endosomal curvature does not grossly alter fusion kinetics, although membrane deformability does. This supports a model for influenza virus entry where cells restrict or permit membrane fusion by changing deformability, for instance, using interferon-induced proteins.

scholarly journals Viral membrane fusion

Virology ◽  
2015 ◽  
Vol 479-480 ◽  
pp. 498-507 ◽  
Author(s):  
Stephen C. Harrison
Keyword(s):  
Membrane Fusion ◽  
Viral Membrane ◽  
Viral Membrane Fusion

scholarly journals Characterization of the Early Events in Dengue Virus Cell Entry by Biochemical Assays and Single-Virus Tracking

2007 ◽  
Vol 81 (21) ◽  
pp. 12019-12028 ◽  
Author(s):  
Hilde M. van der Schaar ◽  
Michael J. Rust ◽  
Barry-Lee Waarts ◽  
Heidi van der Ende-Metselaar ◽  
Richard J. Kuhn ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Dengue Virus ◽  
Membrane Fusion ◽  
High Ratio ◽  
Cell Entry ◽  
Viral Membrane ◽  
Virus Particles ◽  
Biochemical Assays ◽  
Particle Ratio ◽  
Infectious Unit

ABSTRACT In this study, we investigated the cell entry characteristics of dengue virus (DENV) type 2 strain S1 on mosquito, BHK-15, and BS-C-1 cells. The concentration of virus particles measured by biochemical assays was found to be substantially higher than the number of infectious particles determined by infectivity assays, leading to an infectious unit-to-particle ratio of approximately 1:2,600 to 1:72,000, depending on the specific assays used. In order to explain this high ratio, we investigated the receptor binding and membrane fusion characteristics of single DENV particles in living cells using real-time fluorescence microscopy. For this purpose, DENV was labeled with the lipophilic fluorescent probe DiD (1,1′-dioctadecyl-3,3,3′,3′-tetramethylindodicarbocyanine, 4-chlorobenzenesulfonate salt). The surface density of the DiD dye in the viral membrane was sufficiently high to largely quench the fluorescence intensity but still allowed clear detection of single virus particles. Fusion of the viral membrane with the cell membrane was evident as fluorescence dequenching. It was observed that DENV binds very inefficiently to the cells used, explaining at least in part the high infectious unit-to-particle ratio. The particles that did bind to the cells showed different types of transport behavior leading to membrane fusion in both the periphery and perinuclear regions of the cell. Membrane fusion was observed in 1 out of 6 bound virus particles, indicating that a substantial fraction of the virus has the capacity to fuse. DiD dequenching was completely inhibited by ammonium chloride, demonstrating that fusion occurs exclusively from within acidic endosomes.

scholarly journals Electron Cryotomography of Tula Hantavirus Suggests a Unique Assembly Paradigm for Enveloped Viruses

2010 ◽  
Vol 84 (10) ◽  
pp. 4889-4897 ◽  
Author(s):  
Juha T. Huiskonen ◽  
Jussi Hepojoki ◽  
Pasi Laurinmäki ◽  
Antti Vaheri ◽  
Hilkka Lankinen ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Hemorrhagic Fever ◽  
Membrane Curvature ◽  
Emerging Viruses ◽  
Enveloped Viruses ◽  
Viral Membrane ◽  
Density Maps ◽  
Virion Structure ◽  
Electron Cryotomography ◽  
Assembly Principles

ABSTRACT Hantaviruses (family Bunyaviridae) are rodent-borne emerging viruses that cause a serious, worldwide threat to human health. Hantavirus diseases include hemorrhagic fever with renal syndrome and hantavirus cardiopulmonary syndrome. Virions are enveloped and contain a tripartite single-stranded negative-sense RNA genome. Two types of glycoproteins, GN and GC, are embedded in the viral membrane and form protrusions, or “spikes.” The membrane encloses a ribonucleoprotein core, which consists of the RNA segments, the nucleocapsid protein, and the RNA-dependent RNA polymerase. Detailed information on hantavirus virion structure and glycoprotein spike composition is scarce. Here, we have studied the structures of Tula hantavirus virions using electron cryomicroscopy and tomography. Three-dimensional density maps show how the hantavirus surface glycoproteins, membrane, and ribonucleoprotein are organized. The structure of the GN-GC spike complex was solved to 3.6-nm resolution by averaging tomographic subvolumes. Each spike complex is a square-shaped assembly with 4-fold symmetry. Spike complexes formed ordered patches on the viral membrane by means of specific lateral interactions. These interactions may be sufficient for creating membrane curvature during virus budding. In conclusion, the structure and assembly principles of Tula hantavirus exemplify a unique assembly paradigm for enveloped viruses.

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