Special Issue "Molecular Determinants of Enveloped Virus Assembly"

A special issue of Viruses (ISSN 1999-4915). This special issue belongs to the section "Animal Viruses".

Deadline for manuscript submissions: closed (16 April 2021).

Special Issue Editor

Dr. Abdul A. Waheed
E-Mail Website
Guest Editor
Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702, USA
Interests: virology; retroviruses; virus assembly; host restriction factors; cell biology; small-molecule inhibitors

Special Issue Information

Dear Colleagues,

Enveloped viruses assemble at diverse locations within the infected cell and acquire their lipid bilayers during budding through cellular membranes. Although Gag alone is sufficient for the production of retroviral particles, in several other viral systems, co-expression of multiple viral proteins is required for efficient particle assembly and release. In all enveloped viral systems, incorporation of the envelope glycoproteins is an essential step in the formation of infectious particles, and many viruses undergo maturation events during or shortly after assembly and release. In addition to viral components, cellular factors play critical roles at various stages of virus assembly and release.

The main goal of this issue is to present a collection of papers that will offer special insights into the molecular determinants of viral and cellular factors essential for the assembly of enveloped viruses. I hope that this Special Issue will serve as a valuable resource to both new and established researchers in the field.

Dr. Abdul A. Waheed
Guest Editor

Manuscript Submission Information

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Keywords

  • enveloped viruses
  • budding and release
  • viral determinants
  • membrane lipids
  • host proteins
  • restriction factors
  • assembly inhibitors

Published Papers (5 papers)

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Research

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Article
Cysteine Mutations in the Ebolavirus Matrix Protein VP40 Promote Phosphatidylserine Binding by Increasing the Flexibility of a Lipid-Binding Loop
Viruses 2021, 13(7), 1375; https://doi.org/10.3390/v13071375 - 15 Jul 2021
Viewed by 749
Abstract
Ebolavirus (EBOV) is a negative-sense RNA virus that causes severe hemorrhagic fever in humans. The matrix protein VP40 facilitates viral budding by binding to lipids in the host cell plasma membrane and driving the formation of filamentous, pleomorphic virus particles. The C-terminal domain [...] Read more.
Ebolavirus (EBOV) is a negative-sense RNA virus that causes severe hemorrhagic fever in humans. The matrix protein VP40 facilitates viral budding by binding to lipids in the host cell plasma membrane and driving the formation of filamentous, pleomorphic virus particles. The C-terminal domain of VP40 contains two highly-conserved cysteine residues at positions 311 and 314, but their role in the viral life cycle is unknown. We therefore investigated the properties of VP40 mutants in which the conserved cysteine residues were replaced with alanine. The C311A mutation significantly increased the affinity of VP40 for membranes containing phosphatidylserine (PS), resulting in the assembly of longer virus-like particles (VLPs) compared to wild-type VP40. The C314A mutation also increased the affinity of VP40 for membranes containing PS, albeit to a lesser degree than C311A. The double mutant behaved in a similar manner to the individual mutants. Computer modeling revealed that both cysteine residues restrain a loop segment containing lysine residues that interact with the plasma membrane, but Cys311 has the dominant role. Accordingly, the C311A mutation increases the flexibility of this membrane-binding loop, changes the profile of hydrogen bonding within VP40 and therefore binds to PS with greater affinity. This is the first evidence that mutations in VP40 can increase its affinity for biological membranes and modify the length of Ebola VLPs. The Cys311 and Cys314 residues therefore play an important role in dynamic interactions at the plasma membrane by modulating the ability of VP40 to bind PS. Full article
(This article belongs to the Special Issue Molecular Determinants of Enveloped Virus Assembly)
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Article
The Immunomodulatory CEA Cell Adhesion Molecule 6 (CEACAM6/CD66c) Is a Protein Receptor for the Influenza A Virus
Viruses 2021, 13(5), 726; https://doi.org/10.3390/v13050726 - 21 Apr 2021
Viewed by 836
Abstract
To establish a productive infection in host cells, viruses often use one or multiple host membrane glycoproteins as their receptors. For Influenza A virus (IAV) such a glycoprotein receptor has not been described, to date. Here we show that IAV is using the [...] Read more.
To establish a productive infection in host cells, viruses often use one or multiple host membrane glycoproteins as their receptors. For Influenza A virus (IAV) such a glycoprotein receptor has not been described, to date. Here we show that IAV is using the host membrane glycoprotein CD66c as a receptor for entry into human epithelial lung cells. Neuraminidase (NA), a viral spike protein, binds to CD66c on the cell surface during IAV entry into the host cells. Lung cells overexpressing CD66c showed an increase in virus binding and subsequent entry into the cell. Upon comparison, CD66c demonstrated higher binding capacity than other membrane glycoproteins (EGFR and DC-SIGN) reported earlier to facilitate IAV entry into host cells. siRNA mediated knockdown of CD66c from lung cells inhibited virus binding on cell surface and entry into cells. Blocking CD66c by antibody on the cell surface resulted in decreased virus entry. We found that CD66c is a specific glycoprotein receptor for influenza A virus that did not affect entry of non-IAV RNA virus (Hepatitis C virus). Finally, IAV pre-incubated with recombinant CD66c protein when administered intranasally in mice showed decreased cytopathic effects in mice lungs. This publication is the first to report CD66c (Carcinoembryonic cell adhesion molecule 6 or CEACAM6) as a glycoprotein receptor for Influenza A virus. Full article
(This article belongs to the Special Issue Molecular Determinants of Enveloped Virus Assembly)
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Article
Effect of Small Polyanions on In Vitro Assembly of Selected Members of Alpha-, Beta- and Gammaretroviruses
Viruses 2021, 13(1), 129; https://doi.org/10.3390/v13010129 - 18 Jan 2021
Viewed by 599
Abstract
The assembly of a hexameric lattice of retroviral immature particles requires the involvement of cell factors such as proteins and small molecules. A small, negatively charged polyanionic molecule, myo-inositol hexaphosphate (IP6), was identified to stimulate the assembly of immature particles of HIV-1 and [...] Read more.
The assembly of a hexameric lattice of retroviral immature particles requires the involvement of cell factors such as proteins and small molecules. A small, negatively charged polyanionic molecule, myo-inositol hexaphosphate (IP6), was identified to stimulate the assembly of immature particles of HIV-1 and other lentiviruses. Interestingly, cryo-electron tomography analysis of the immature particles of two lentiviruses, HIV-1 and equine infectious anemia virus (EIAV), revealed that the IP6 binding site is similar. Based on this amino acid conservation of the IP6 interacting site, it is presumed that the assembly of immature particles of all lentiviruses is stimulated by IP6. Although this specific region for IP6 binding may be unique for lentiviruses, it is plausible that other retroviral species also recruit some small polyanion to facilitate the assembly of their immature particles. To study whether the assembly of retroviruses other than lentiviruses can be stimulated by polyanionic molecules, we measured the effect of various polyanions on the assembly of immature virus-like particles of Rous sarcoma virus (RSV), a member of alpharetroviruses, Mason-Pfizer monkey virus (M-PMV) representative of betaretroviruses, and murine leukemia virus (MLV), a member of gammaretroviruses. RSV, M-PMV and MLV immature virus-like particles were assembled in vitro from truncated Gag molecules and the effect of selected polyanions, myo-inostol hexaphosphate, myo-inositol, glucose-1,6-bisphosphate, myo-inositol hexasulphate, and mellitic acid, on the particles assembly was quantified. Our results suggest that the assembly of immature particles of RSV and MLV was indeed stimulated by the presence of myo-inostol hexaphosphate and myo-inositol, respectively. In contrast, no effect on the assembly of M-PMV as a betaretrovirus member was observed. Full article
(This article belongs to the Special Issue Molecular Determinants of Enveloped Virus Assembly)
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Review

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Review
The Interplay between ESCRT and Viral Factors in the Enveloped Virus Life Cycle
Viruses 2021, 13(2), 324; https://doi.org/10.3390/v13020324 - 20 Feb 2021
Cited by 4 | Viewed by 622
Abstract
Viruses are obligate parasites that rely on host cellular factors to replicate and spread. The endosomal sorting complexes required for transport (ESCRT) system, which is classically associated with sorting and downgrading surface proteins, is one of the host machineries hijacked by viruses across [...] Read more.
Viruses are obligate parasites that rely on host cellular factors to replicate and spread. The endosomal sorting complexes required for transport (ESCRT) system, which is classically associated with sorting and downgrading surface proteins, is one of the host machineries hijacked by viruses across diverse families. Knowledge gained from research into ESCRT and viruses has, in turn, greatly advanced our understanding of many other cellular functions in which the ESCRT pathway is involved, e.g., cytokinesis. This review highlights the interplay between the ESCRT pathway and the viral factors of enveloped viruses with a special emphasis on retroviruses. Full article
(This article belongs to the Special Issue Molecular Determinants of Enveloped Virus Assembly)
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Review
The Unique, the Known, and the Unknown of Spumaretrovirus Assembly
Viruses 2021, 13(1), 105; https://doi.org/10.3390/v13010105 - 13 Jan 2021
Cited by 1 | Viewed by 671
Abstract
Within the family of Retroviridae, foamy viruses (FVs) are unique and unconventional with respect to many aspects in their molecular biology, including assembly and release of enveloped viral particles. Both components of the minimal assembly and release machinery, Gag and Env, display [...] Read more.
Within the family of Retroviridae, foamy viruses (FVs) are unique and unconventional with respect to many aspects in their molecular biology, including assembly and release of enveloped viral particles. Both components of the minimal assembly and release machinery, Gag and Env, display significant differences in their molecular structures and functions compared to the other retroviruses. This led to the placement of FVs into a separate subfamily, the Spumaretrovirinae. Here, we describe the molecular differences in FV Gag and Env, as well as Pol, which is translated as a separate protein and not in an orthoretroviral manner as a Gag-Pol fusion protein. This feature further complicates FV assembly since a specialized Pol encapsidation strategy via a tripartite Gag-genome–Pol complex is used. We try to relate the different features and specific interaction patterns of the FV Gag, Pol, and Env proteins in order to develop a comprehensive and dynamic picture of particle assembly and release, but also other features that are indirectly affected. Since FVs are at the root of the retrovirus tree, we aim at dissecting the unique/specialized features from those shared among the Spuma- and Orthoretrovirinae. Such analyses may shed light on the evolution and characteristics of virus envelopment since related viruses within the Ortervirales, for instance LTR retrotransposons, are characterized by different levels of envelopment, thus affecting the capacity for intercellular transmission. Full article
(This article belongs to the Special Issue Molecular Determinants of Enveloped Virus Assembly)
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