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Denker L, Dixon AM. The cell edit: Looking at and beyond non-structural proteins to understand membrane rearrangement in coronaviruses. Arch Biochem Biophys 2024; 752:109856. [PMID: 38104958 DOI: 10.1016/j.abb.2023.109856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 11/24/2023] [Accepted: 12/08/2023] [Indexed: 12/19/2023]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a positive-stranded RNA virus that sits at the centre of the recent global pandemic. As a member of the coronaviridae family of viruses, it shares features such as a very large genome (>30 kb) that is replicated in a purpose-built replication organelle. Biogenesis of the replication organelle requires significant and concerted rearrangement of the endoplasmic reticulum membrane, a job that is carried out by a group of integral membrane non-structural proteins (NSP3, 4 and 6) expressed by the virus along with a host of viral replication enzymes and other factors that support transcription and replication. The primary sites for RNA replication within the replication organelle are double membrane vesicles (DMVs). The small size of DMVs requires generation of high membrane curvature, as well as stabilization of a double-membrane arrangement, but the mechanisms that underlie DMV formation remain elusive. In this review, we discuss recent breakthroughs in our understanding of the molecular basis for membrane rearrangements by coronaviruses. We incorporate established models of NSP3-4 protein-protein interactions to drive double membrane formation, and recent data highlighting the roles of lipid composition and host factor proteins (e.g. reticulons) that influence membrane curvature, to propose a revised model for DMV formation in SARS-CoV-2.
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Affiliation(s)
- Lea Denker
- Warwick Medical School, Biomedical Sciences, University of Warwick, Coventry, CV4 7AL, UK.
| | - Ann M Dixon
- Department of Chemistry, University of Warwick, Coventry, CV4 7SH, UK.
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2
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Chai P, Lebedenko CG, Flynn RA. RNA Crossing Membranes: Systems and Mechanisms Contextualizing Extracellular RNA and Cell Surface GlycoRNAs. Annu Rev Genomics Hum Genet 2023; 24:85-107. [PMID: 37068783 DOI: 10.1146/annurev-genom-101722-101224] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/19/2023]
Abstract
The subcellular localization of a biopolymer often informs its function. RNA is traditionally confined to the cytosolic and nuclear spaces, where it plays critical and conserved roles across nearly all biochemical processes. Our recent observation of cell surface glycoRNAs may further explain the extracellular role of RNA. While cellular membranes are efficient gatekeepers of charged polymers such as RNAs, a large body of research has demonstrated the accumulation of specific RNA species outside of the cell, termed extracellular RNAs (exRNAs). Across various species and forms of life, protein pores have evolved to transport RNA across membranes, thus providing a mechanistic path for exRNAs to achieve their extracellular topology. Here, we review types of exRNAs and the pores capable of RNA transport to provide a logical and testable path toward understanding the biogenesis and regulation of cell surface glycoRNAs.
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Affiliation(s)
- Peiyuan Chai
- Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital, Boston, Massachusetts, USA;
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Charlotta G Lebedenko
- Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital, Boston, Massachusetts, USA;
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Ryan A Flynn
- Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital, Boston, Massachusetts, USA;
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, Massachusetts, USA
- Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts, USA
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3
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Kratzel A, Thiel V. RTN3 and RTN4: Architects of SARS-CoV-2 replication organelles. J Cell Biol 2023; 222:e202306020. [PMID: 37318453 PMCID: PMC10274048 DOI: 10.1083/jcb.202306020] [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] [Indexed: 06/16/2023] Open
Abstract
SARS-CoV-2 depends on host proteins for successful replication. In this issue, Williams et al. (2023. J. Cell Biol.https://doi.org/10.1083/jcb.202203060) report that the ER membrane-modulating proteins RTN3 and RTN4 are required for the formation of SARS-CoV-2 replication organelles via direct interaction with viral proteins NSP3 and NSP4.
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Affiliation(s)
- Annika Kratzel
- Institute of Virology and Immunology (IVI), Bern, Switzerland
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Volker Thiel
- Institute of Virology and Immunology (IVI), Bern, Switzerland
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Multidisciplinary Center for Infectious Diseases (MCID), University of Bern, Bern, Switzerland
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4
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Williams JM, Chen YJ, Cho WJ, Tai AW, Tsai B. Reticulons promote formation of ER-derived double-membrane vesicles that facilitate SARS-CoV-2 replication. J Cell Biol 2023; 222:e202203060. [PMID: 37093123 PMCID: PMC10130743 DOI: 10.1083/jcb.202203060] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 08/24/2022] [Accepted: 04/06/2023] [Indexed: 04/25/2023] Open
Abstract
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the etiologic agent for the global COVID-19 pandemic, triggers the formation of endoplasmic reticulum (ER)-derived replication organelles, including double-membrane vesicles (DMVs), in the host cell to support viral replication. Here, we clarify how SARS-CoV-2 hijacks host factors to construct the DMVs. We show that the ER morphogenic proteins reticulon-3 (RTN3) and RTN4 help drive DMV formation, enabling viral replication, which leads to productive infection. Different SARS-CoV-2 variants, including the delta variant, use the RTN-dependent pathway to promote infection. Mechanistically, our results reveal that the membrane-embedded reticulon homology domain (RHD) of the RTNs is sufficient to functionally support viral replication and physically engage NSP3 and NSP4, two viral non-structural membrane proteins known to induce DMV formation. Our findings thus identify the ER morphogenic RTN3 and RTN4 membrane proteins as host factors that help promote the biogenesis of SARS-CoV-2-induced DMVs, which can act as viral replication platforms.
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Affiliation(s)
- Jeffrey M. Williams
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Yu-Jie Chen
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Woo Jung Cho
- Biomedical Research Core Facilities, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Andrew W. Tai
- Department of Internal Medicine and Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
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5
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Ávila-Pérez G, Rejas MT, Chichón FJ, Guerra M, Fernández JJ, Rodríguez D. Architecture of torovirus replicative organelles. Mol Microbiol 2021; 117:837-850. [PMID: 34967475 DOI: 10.1111/mmi.14875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 12/20/2021] [Accepted: 12/22/2021] [Indexed: 11/29/2022]
Abstract
Plus-stranded RNA viruses replicate in the cytosol of infected cells, in membrane-bound replication complexes. We previously identified double membrane vesicles (DMVs) in the cytoplasm of cells infected with Berne virus (BEV), the prototype member of Torovirus genus (Nidovirales Order). Our previous analysis by transmission electron microscopy suggested that the DMVs form a reticulovesicular network (RVN) analogous those described for the related severe acute respiratory syndrome coronavirus (SARS-CoV-1). Here, we used serial sectioning and electron tomography to characterize the architecture of torovirus replication organelles, and to learn about their biogenesis and dynamics during the infection. The formation of a RVN in BEV infected cells was confirmed, where the outer membranes of the DMVs are interconnected with each other and with the ER. Paired or zippered ER membranes connected with the DMVs were also observed, and likely represent early structures that evolve to give rise to DMVs. Also, paired membranes forming small spherule-like invaginations were observed at late time post-infection. Although resembling in size, the tomographic analysis show that these structures are clearly different from the true spherules described previously for coronaviruses. Hence, BEV shows important similarities, but also some differences, in the architecture of the replication organelles with other nidoviruses.
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Affiliation(s)
- Ginés Ávila-Pérez
- Department of Molecular and Cellular Biology, Centro de Biología Molecular Severo Ochoa, CSIC, C/Nicolás Cabrera 1, 28049, Madrid, Spain
| | - María Teresa Rejas
- Servicio de Microscopía Electrónica, Centro de Biología Molecular Severo Ochoa, CSIC, C/Nicolás Cabrera 1, 28049, Madrid, Spain
| | - Francisco Javier Chichón
- Servicio de Criomicroscopía Electrónica (cryoEM-CSIC) and Department of Macromolecular Structures, Centro Nacional de Biotecnología, CSIC, C/Darwin 3, 28049, Madrid, Spain
| | - Milagros Guerra
- Servicio de Microscopía Electrónica, Centro de Biología Molecular Severo Ochoa, CSIC, C/Nicolás Cabrera 1, 28049, Madrid, Spain
| | - José Jesús Fernández
- Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), CINN-CSIC, Av Hospital Universitario s/n, 33011, Oviedo, Spain
| | - Dolores Rodríguez
- Department of Molecular and Cellular Biology, Centro de Biología Molecular Severo Ochoa, CSIC, C/Nicolás Cabrera 1, 28049, Madrid, Spain
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6
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Alketbi EH, Hamdy R, El-Kabalawy A, Juric V, Pignitter M, A Mosa K, Almehdi AM, El-Keblawy AA, Soliman SSM. Lipid-based therapies against SARS-CoV-2 infection. Rev Med Virol 2021; 31:1-13. [PMID: 34546604 PMCID: PMC8013851 DOI: 10.1002/rmv.2214] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 12/20/2020] [Accepted: 12/21/2020] [Indexed: 12/12/2022]
Abstract
Viruses have evolved to manipulate host lipid metabolism to benefit their replication cycle. Enveloped viruses, including coronaviruses, use host lipids in various stages of the viral life cycle, particularly in the formation of replication compartments and envelopes. Host lipids are utilised by the virus in receptor binding, viral fusion and entry, as well as viral replication. Association of dyslipidaemia with the pathological development of Covid‐19 raises the possibility that exploitation of host lipid metabolism might have therapeutic benefit against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). In this review, promising host lipid targets are discussed along with potential inhibitors. In addition, specific host lipids are involved in the inflammatory responses due to viral infection, so lipid supplementation represents another potential strategy to counteract the severity of viral infection. Furthermore, switching the lipid metabolism through a ketogenic diet is another potential way of limiting the effects of viral infection. Taken together, restricting the access of host lipids to the virus, either by using lipid inhibitors or supplementation with exogenous lipids, might significantly limit SARS‐CoV‐2 infection and/or severity.
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Affiliation(s)
- Eman Humaid Alketbi
- Department of Applied Biology, College of Sciences, University of Sharjah, Sharjah, United Arab Emirates
| | - Rania Hamdy
- Research Institute for Medical and Health Sciences, University of Sharjah, Sharjah, United Arab Emirates.,Faculty of Pharmacy, Zagazig University, Zagazig, Egypt
| | | | - Viktorija Juric
- Department of Physiological Chemistry, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Marc Pignitter
- Department of Physiological Chemistry, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Kareem A Mosa
- Department of Applied Biology, College of Sciences, University of Sharjah, Sharjah, United Arab Emirates.,Research Institute of Science and Engineering, University of Sharjah, Sharjah, United Arab Emirates.,Department of Biotechnology, Faculty of Agriculture, Al-Azhar University, Cairo, Egypt
| | - Ahmed M Almehdi
- Department of Chemistry, College of Sciences, University of Sharjah, Sharjah, United Arab Emirates
| | - Ali A El-Keblawy
- Department of Applied Biology, College of Sciences, University of Sharjah, Sharjah, United Arab Emirates.,Research Institute of Science and Engineering, University of Sharjah, Sharjah, United Arab Emirates
| | - Sameh S M Soliman
- Research Institute for Medical and Health Sciences, University of Sharjah, Sharjah, United Arab Emirates.,Faculty of Pharmacy, Zagazig University, Zagazig, Egypt.,Department of Medicinal Chemistry, College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates
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7
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A Comprehensive Insight into the Role of Exosomes in Viral Infection: Dual Faces Bearing Different Functions. Pharmaceutics 2021; 13:pharmaceutics13091405. [PMID: 34575480 PMCID: PMC8466084 DOI: 10.3390/pharmaceutics13091405] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 08/31/2021] [Accepted: 09/02/2021] [Indexed: 12/13/2022] Open
Abstract
Extracellular vesicles (EVs) subtype, exosome is an extracellular nano-vesicle that sheds from cells’ surface and originates as intraluminal vesicles during endocytosis. Firstly, it was thought to be a way for the cell to get rid of unwanted materials as it loaded selectively with a variety of cellular molecules, including RNAs, proteins, and lipids. However, it has been found to play a crucial role in several biological processes such as immune modulation, cellular communication, and their role as vehicles to transport biologically active molecules. The latest discoveries have revealed that many viruses export their viral elements within cellular factors using exosomes. Hijacking the exosomal pathway by viruses influences downstream processes such as viral propagation and cellular immunity and modulates the cellular microenvironment. In this manuscript, we reviewed exosomes biogenesis and their role in the immune response to viral infection. In addition, we provided a summary of how some pathogenic viruses hijacked this normal physiological process. Viral components are harbored in exosomes and the role of these exosomes in viral infection is discussed. Understanding the nature of exosomes and their role in viral infections is fundamental for future development for them to be used as a vaccine or as a non-classical therapeutic strategy to control several viral infections.
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8
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Markiewicz L, Drazkowska K, Sikorski PJ. Tricks and threats of RNA viruses - towards understanding the fate of viral RNA. RNA Biol 2021; 18:669-687. [PMID: 33618611 PMCID: PMC8078519 DOI: 10.1080/15476286.2021.1875680] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 12/22/2020] [Accepted: 01/09/2021] [Indexed: 12/24/2022] Open
Abstract
Human innate cellular defence pathways have evolved to sense and eliminate pathogens, of which, viruses are considered one of the most dangerous. Their relatively simple structure makes the identification of viral invasion a difficult task for cells. In the course of evolution, viral nucleic acids have become one of the strongest and most reliable early identifiers of infection. When considering RNA virus recognition, RNA sensing is the central mechanism in human innate immunity, and effectiveness of this sensing is crucial for triggering an appropriate antiviral response. Although human cells are armed with a variety of highly specialized receptors designed to respond only to pathogenic viral RNA, RNA viruses have developed an array of mechanisms to avoid being recognized by human interferon-mediated cellular defence systems. The repertoire of viral evasion strategies is extremely wide, ranging from masking pathogenic RNA through end modification, to utilizing sophisticated techniques to deceive host cellular RNA degrading enzymes, and hijacking the most basic metabolic pathways in host cells. In this review, we aim to dissect human RNA sensing mechanisms crucial for antiviral immune defences, as well as the strategies adopted by RNA viruses to avoid detection and degradation by host cells. We believe that understanding the fate of viral RNA upon infection, and detailing the molecular mechanisms behind virus-host interactions, may be helpful for developing more effective antiviral strategies; which are urgently needed to prevent the far-reaching consequences of widespread, highly pathogenic viral infections.
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9
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V'kovski P, Kratzel A, Steiner S, Stalder H, Thiel V. Coronavirus biology and replication: implications for SARS-CoV-2. Nat Rev Microbiol 2021; 19:155-170. [PMID: 33116300 PMCID: PMC7592455 DOI: 10.1038/s41579-020-00468-6] [Citation(s) in RCA: 1689] [Impact Index Per Article: 563.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/25/2020] [Indexed: 02/06/2023]
Abstract
The SARS-CoV-2 pandemic and its unprecedented global societal and economic disruptive impact has marked the third zoonotic introduction of a highly pathogenic coronavirus into the human population. Although the previous coronavirus SARS-CoV and MERS-CoV epidemics raised awareness of the need for clinically available therapeutic or preventive interventions, to date, no treatments with proven efficacy are available. The development of effective intervention strategies relies on the knowledge of molecular and cellular mechanisms of coronavirus infections, which highlights the significance of studying virus-host interactions at the molecular level to identify targets for antiviral intervention and to elucidate critical viral and host determinants that are decisive for the development of severe disease. In this Review, we summarize the first discoveries that shape our current understanding of SARS-CoV-2 infection throughout the intracellular viral life cycle and relate that to our knowledge of coronavirus biology. The elucidation of similarities and differences between SARS-CoV-2 and other coronaviruses will support future preparedness and strategies to combat coronavirus infections.
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Affiliation(s)
- Philip V'kovski
- Institute of Virology and Immunology (IVI), Bern, Switzerland
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Annika Kratzel
- Institute of Virology and Immunology (IVI), Bern, Switzerland
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Silvio Steiner
- Institute of Virology and Immunology (IVI), Bern, Switzerland
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Hanspeter Stalder
- Institute of Virology and Immunology (IVI), Bern, Switzerland
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Volker Thiel
- Institute of Virology and Immunology (IVI), Bern, Switzerland.
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
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10
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Amini Pouya M, Afshani SM, Maghsoudi AS, Hassani S, Mirnia K. Classification of the present pharmaceutical agents based on the possible effective mechanism on the COVID-19 infection. Daru 2020; 28:745-764. [PMID: 32734518 PMCID: PMC7391927 DOI: 10.1007/s40199-020-00359-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 07/14/2020] [Indexed: 12/15/2022] Open
Abstract
OBJECTIVES There are several types of research on the COVID-19 disease which have been conducting. It seems that prevailing over the pandemic would be achieved only by mastering over the virus pathophysiology. We tried to categorize the massive amount of available information for useful interpretation. EVIDENCE ACQUISITION We searched databases with different keywords and search strategies that focus on virulence and pathophysiology of COVID-19. The present review has aimed to gather and categorize all implemented drugs based on the susceptible virulence mechanisms, and the pathophysiological events in the host cells, discussing and suggesting treatments. RESULTS As a result, the COVID-19 lifecycle were categorized as following steps: "Host Cell Attachment" which is mainly conducted with ACE2 receptors and TMPRSS2 from the host cell and Spike (S) protein, "Endocytosis Pathway" which is performed mainly by clathrin-mediated endocytosis, and "Viral Replication" which contains translation and replication of RNA viral genome. The virus pathogenicity is continued by "Inflammatory Reactions" which mainly caused moderate to severe COVID-19 disease. Besides, the possible effective therapeutics' mechanism and the pharmaceutical agents that had at least one experience as a preclinical or clinical study on COVID-19 were clearly defined. CONCLUSION The treatment protocol would be occasional based on the stage of the infection and the patient situation. The cocktail of medicines, which could affect almost all mentioned stages of COVID-19 disease, might be vital for patients with severe phenomena. The classification of the possible mechanism of medicines based on COVID-19 pathogenicity.
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Affiliation(s)
- Maryam Amini Pouya
- Department of Pharmaceutics, School of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
| | - Seyyedeh Maryam Afshani
- Department of Pharmacoeconomics, School of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
| | - Armin Salek Maghsoudi
- Department of Toxicology and Pharmacology, School of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
| | - Shokoufeh Hassani
- Department of Toxicology and Pharmacology, School of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran.
- Toxicology and Diseases Group (TDG), Pharmaceutical Sciences Research Center (PSRC), the Institute of Pharmaceutical Sciences (TIPS), Tehran University of Medical Sciences, Tehran, Iran.
| | - Kayvan Mirnia
- Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran.
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11
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Zhang J, Lan Y, Sanyal S. Membrane heist: Coronavirus host membrane remodeling during replication. Biochimie 2020; 179:229-236. [PMID: 33115667 PMCID: PMC7585727 DOI: 10.1016/j.biochi.2020.10.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 09/28/2020] [Accepted: 10/22/2020] [Indexed: 02/06/2023]
Abstract
The ongoing pandemic of COVID-19 (Coronavirus Disease-2019), a respiratory disease caused by the novel coronavirus strain, SARS-CoV-2, has affected more than 42 million people already, with more than one million deaths worldwide (as of October 25, 2020). We are in urgent need of therapeutic interventions that target the host-virus interface, which requires a molecular understanding of the SARS-CoV-2 life-cycle. Like other positive-sense RNA viruses, coronaviruses remodel intracellular membranes to form specialized viral replication compartments, including double-membrane vesicles (DMVs), where viral RNA genome replication takes place. Here we review the current knowledge of the structure, lipid composition, function, and biogenesis of coronavirus-induced DMVs, highlighting the druggable viral and cellular factors that are involved in the formation and function of DMVs.
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Affiliation(s)
- Jingshu Zhang
- Artemis One Health Research Foundation, Delft, the Netherlands
| | - Yun Lan
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Sumana Sanyal
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK; HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
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12
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Structural and functional insights into non-structural proteins of coronaviruses. Microb Pathog 2020; 150:104641. [PMID: 33242646 PMCID: PMC7682334 DOI: 10.1016/j.micpath.2020.104641] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 11/15/2020] [Accepted: 11/16/2020] [Indexed: 12/15/2022]
Abstract
Coronaviruses (CoVs) are causing a number of human and animal diseases because of their zoonotic nature such as Middle East respiratory syndrome (MERS), severe acute respiratory syndrome (SARS) and coronavirus disease 2019 (COVID-19). These viruses can infect respiratory, gastrointestinal, hepatic and central nervous systems of human, livestock, birds, bat, mouse, and many wild animals. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a newly emerging respiratory virus and is causing CoVID-19 with high morbidity and considerable mortality. All CoVs belong to the order Nidovirales, family Coronaviridae, are enveloped positive-sense RNA viruses, characterised by club-like spikes on their surfaces and large RNA genome with a distinctive replication strategy. Coronavirus have the largest RNA genomes (~26–32 kilobases) and their expansion was likely enabled by acquiring enzyme functions that counter the commonly high error frequency of viral RNA polymerases. Non-structural proteins (nsp) 7–16 are cleaved from two large replicase polyproteins and guide the replication and processing of coronavirus RNA. Coronavirus replicase has more or less universal activities, such as RNA polymerase (nsp 12) and helicase (nsp 13), as well as a variety of unusual or even special mRNA capping (nsp 14, nsp 16) and fidelity regulation (nsp 14) domains. Besides that, several smaller subunits (nsp 7– nsp 10) serve as essential cofactors for these enzymes and contribute to the emerging “nsp interactome.” In spite of the significant progress in studying coronaviruses structural and functional properties, there is an urgent need to understand the coronaviruses evolutionary success that will be helpful to develop enhanced control strategies. Therefore, it is crucial to understand the structure, function, and interactions of coronaviruses RNA synthesizing machinery and their replication strategies.
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13
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Elrashdy F, Aljaddawi AA, Redwan EM, Uversky VN. On the potential role of exosomes in the COVID-19 reinfection/reactivation opportunity. J Biomol Struct Dyn 2020; 39:5831-5842. [PMID: 32643586 PMCID: PMC7441802 DOI: 10.1080/07391102.2020.1790426] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We propose here that one of the potential mechanisms for the relapse of the COVID-19 infection could be a cellular transport pathway associated with the release of the SARS-CoV-2-loaded exosomes and other extracellular vesicles. It is possible that this “Trojan horse” strategy represents possible explanation for the re-appearance of the viral RNA in the recovered COVID-19 patients 7–14 day post discharge, suggesting that viral material was hidden within such exosomes or extracellular vesicles during this “silence” time period and then started to re-spread again. Communicated by Ramaswamy H. Sarma
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Affiliation(s)
- Fatma Elrashdy
- Department of Endemic Medicine and Hepatogastroenterology, Kasr Alainy School of Medicine, Cairo University, Cairo, Egypt
| | - Abdullah A Aljaddawi
- Biological Science Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Elrashdy M Redwan
- Biological Science Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Vladimir N Uversky
- Biological Science Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia.,Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, USA.,Institute for Biological Instrumentation of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", Pushchino, Russia
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14
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Snijder EJ, Limpens RWAL, de Wilde AH, de Jong AWM, Zevenhoven-Dobbe JC, Maier HJ, Faas FFGA, Koster AJ, Bárcena M. A unifying structural and functional model of the coronavirus replication organelle: Tracking down RNA synthesis. PLoS Biol 2020; 18:e3000715. [PMID: 32511245 PMCID: PMC7302735 DOI: 10.1371/journal.pbio.3000715] [Citation(s) in RCA: 304] [Impact Index Per Article: 76.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/18/2020] [Accepted: 05/14/2020] [Indexed: 12/12/2022] Open
Abstract
Zoonotic coronavirus (CoV) infections, such as those responsible for the current severe acute respiratory syndrome-CoV 2 (SARS-CoV-2) pandemic, cause grave international public health concern. In infected cells, the CoV RNA-synthesizing machinery associates with modified endoplasmic reticulum membranes that are transformed into the viral replication organelle (RO). Although double-membrane vesicles (DMVs) appear to be a pan-CoV RO element, studies to date describe an assortment of additional CoV-induced membrane structures. Despite much speculation, it remains unclear which RO element(s) accommodate viral RNA synthesis. Here we provide detailed 2D and 3D analyses of CoV ROs and show that diverse CoVs essentially induce the same membrane modifications, including the small open double-membrane spherules (DMSs) previously thought to be restricted to gamma- and delta-CoV infections and proposed as sites of replication. Metabolic labeling of newly synthesized viral RNA followed by quantitative electron microscopy (EM) autoradiography revealed abundant viral RNA synthesis associated with DMVs in cells infected with the beta-CoVs Middle East respiratory syndrome-CoV (MERS-CoV) and SARS-CoV and the gamma-CoV infectious bronchitis virus. RNA synthesis could not be linked to DMSs or any other cellular or virus-induced structure. Our results provide a unifying model of the CoV RO and clearly establish DMVs as the central hub for viral RNA synthesis and a potential drug target in CoV infection.
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Affiliation(s)
- Eric J. Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Ronald W. A. L. Limpens
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Adriaan H. de Wilde
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Anja W. M. de Jong
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Jessika C. Zevenhoven-Dobbe
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, the Netherlands
| | | | - Frank F. G. A. Faas
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Abraham J. Koster
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Montserrat Bárcena
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands
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15
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Kikkert M. Innate Immune Evasion by Human Respiratory RNA Viruses. J Innate Immun 2019; 12:4-20. [PMID: 31610541 PMCID: PMC6959104 DOI: 10.1159/000503030] [Citation(s) in RCA: 238] [Impact Index Per Article: 47.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 08/07/2019] [Indexed: 02/06/2023] Open
Abstract
The impact of respiratory virus infections on the health of children and adults can be very significant. Yet, in contrast to most other childhood infections as well as other viral and bacterial diseases, prophylactic vaccines or effective antiviral treatments against viral respiratory infections are either still not available, or provide only limited protection. Given the widespread prevalence, a general lack of natural sterilizing immunity, and/or high morbidity and lethality rates of diseases caused by influenza, respiratory syncytial virus, coronaviruses, and rhinoviruses, this difficult situation is a genuine societal challenge. A thorough understanding of the virus-host interactions during these respiratory infections will most probably be pivotal to ultimately meet these challenges. This review attempts to provide a comparative overview of the knowledge about an important part of the interaction between respiratory viruses and their host: the arms race between host innate immunity and viral innate immune evasion. Many, if not all, viruses, including the respiratory viruses listed above, suppress innate immune responses to gain a window of opportunity for efficient virus replication and setting-up of the infection. The consequences for the host's immune response are that it is often incomplete, delayed or diminished, or displays overly strong induction (after the delay) that may cause tissue damage. The affected innate immune response also impacts subsequent adaptive responses, and therefore viral innate immune evasion often undermines fully protective immunity. In this review, innate immune responses relevant for respiratory viruses with an RNA genome will briefly be summarized, and viral innate immune evasion based on shielding viral RNA species away from cellular innate immune sensors will be discussed from different angles. Subsequently, viral enzymatic activities that suppress innate immune responses will be discussed, including activities causing host shut-off and manipulation of stress granule formation. Furthermore, viral protease-mediated immune evasion and viral manipulation of the ubiquitin system will be addressed. Finally, perspectives for use of the reviewed knowledge for the development of novel antiviral strategies will be sketched.
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Affiliation(s)
- Marjolein Kikkert
- Department of Medical Microbiology, Leiden University Medical Center, Molecular Virology Laboratory, Leiden, The Netherlands,
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16
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J Alsaadi EA, Jones IM. Membrane binding proteins of coronaviruses. Future Virol 2019; 14:275-286. [PMID: 32201500 PMCID: PMC7079996 DOI: 10.2217/fvl-2018-0144] [Citation(s) in RCA: 133] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 02/19/2019] [Indexed: 12/12/2022]
Abstract
Coronaviruses (CoVs) infect many species causing a variety of diseases with a range of severities. Their members include zoonotic viruses with pandemic potential where therapeutic options are currently limited. Despite this diversity CoVs share some common features including the production, in infected cells, of elaborate membrane structures. Membranes represent both an obstacle and aid to CoV replication - and in consequence - virus-encoded structural and nonstructural proteins have membrane-binding properties. The structural proteins encounter cellular membranes at both entry and exit of the virus while the nonstructural proteins reorganize cellular membranes to benefit virus replication. Here, the role of each protein in membrane binding is described to provide a comprehensive picture of their role in the CoV replication cycle.
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Affiliation(s)
- Entedar A J Alsaadi
- Biomedical Sciences, School of Biological Sciences, University of Reading, Reading RG6 6AJ, UK.,Department of Microbiology, College of Medicine, Thiqar University, Thiqar, Iraq.,Biomedical Sciences, School of Biological Sciences, University of Reading, Reading RG6 6AJ, UK.,Department of Microbiology, College of Medicine, Thiqar University, Thiqar, Iraq
| | - Ian M Jones
- Biomedical Sciences, School of Biological Sciences, University of Reading, Reading RG6 6AJ, UK.,Biomedical Sciences, School of Biological Sciences, University of Reading, Reading RG6 6AJ, UK
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17
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Scutigliani EM, Kikkert M. Interaction of the innate immune system with positive-strand RNA virus replication organelles. Cytokine Growth Factor Rev 2017; 37:17-27. [PMID: 28709747 PMCID: PMC7108334 DOI: 10.1016/j.cytogfr.2017.05.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 05/15/2017] [Indexed: 02/08/2023]
Abstract
All +RNA viruses induce replication organelles to shield viral RNA from innate immune surveillance. Recent literature suggests that non-self or aberrant-self membrane structures can be tagged with LC3 or ubiquitin. Interferon-induced GTPases then recognize these tags and destroy the membrane structures, thereby exposing PAMPs. More research will have to indicate whether this is a general antiviral mechanism affecting +RNA virus infections.
The potential health risks associated with (re-)emerging positive-strand RNA (+RNA) viruses emphasizes the need for understanding host-pathogen interactions for these viruses. The innate immune system forms the first line of defense against pathogenic organisms like these and is responsible for detecting pathogen-associated molecular patterns (PAMPs). Viral RNA is a potent inducer of antiviral innate immune signaling, provoking an antiviral state by directing expression of interferons (IFNs) and pro-inflammatory cytokines. However, +RNA viruses developed various methods to avoid detection and downstream signaling, including isolation of viral RNA replication in membranous viral replication organelles (ROs). These structures therefore play a central role in infection, and consequently, loss of RO integrity might simultaneously result in impaired viral replication and enhanced antiviral signaling. This review summarizes the first indications that the innate immune system indeed has tools to disrupt viral ROs and other non- or aberrant-self membrane structures, and may do this by marking these membranes with proteins such as microtubule-associated protein 1A/1B-light chain 3 (LC3) and ubiquitin, resulting in the recruitment of IFN-inducible GTPases. Further studies should evaluate whether this process forms a general effector mechanism in +RNA virus infection, thereby creating the opportunity for development of novel antiviral therapies.
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Affiliation(s)
- Enzo Maxim Scutigliani
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Marjolein Kikkert
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands.
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18
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Antiviral Innate Immune Response Interferes with the Formation of Replication-Associated Membrane Structures Induced by a Positive-Strand RNA Virus. mBio 2016; 7:mBio.01991-16. [PMID: 27923923 PMCID: PMC5142621 DOI: 10.1128/mbio.01991-16] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Infection with nidoviruses like corona- and arteriviruses induces a reticulovesicular network of interconnected endoplasmic reticulum (ER)-derived double-membrane vesicles (DMVs) and other membrane structures. This network is thought to accommodate the viral replication machinery and protect it from innate immune detection. We hypothesized that the innate immune response has tools to counteract the formation of these virus-induced replication organelles in order to inhibit virus replication. Here we have investigated the effect of type I interferon (IFN) treatment on the formation of arterivirus-induced membrane structures. Our approach involved ectopic expression of arterivirus nonstructural proteins nsp2 and nsp3, which induce DMV formation in the absence of other viral triggers of the interferon response, such as replicating viral RNA. Thus, this setup can be used to identify immune effectors that specifically target the (formation of) virus-induced membrane structures. Using large-scale electron microscopy mosaic maps, we found that IFN-β treatment significantly reduced the formation of the membrane structures. Strikingly, we also observed abundant stretches of double-membrane sheets (a proposed intermediate of DMV formation) in IFN-β-treated samples, suggesting the disruption of DMV biogenesis. Three interferon-stimulated gene products, two of which have been reported to target the hepatitis C virus replication structures, were tested for their possible involvement, but none of them affected membrane structure formation. Our study reveals the existence of a previously unknown innate immune mechanism that antagonizes the viral hijacking of host membranes. It also provides a solid basis for further research into the poorly understood interactions between the innate immune system and virus-induced replication structures. IMPORTANCE Viruses with a positive-strand RNA genome establish a membrane-associated replication organelle by hijacking and remodeling intracellular host membranes, a process deemed essential for their efficient replication. It is unknown whether the cellular innate immune system can detect and/or inhibit the formation of these membrane structures, which could be an effective mechanism to delay viral RNA replication. In this study, using an expression system that closely mimics the formation of arterivirus replication structures, we show for the first time that IFN-β treatment clearly reduces the amount of induced membrane structures. Moreover, drastic morphological changes were observed among the remaining structures, suggesting that their biogenesis was impaired. Follow-up experiments suggested that host cells contain a hitherto unknown innate antiviral mechanism, which targets this common feature of positive-strand RNA virus replication. Our study provides a strong basis for further research into the interaction of the innate immune system with membranous viral replication organelles.
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19
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Neuman BW. Bioinformatics and functional analyses of coronavirus nonstructural proteins involved in the formation of replicative organelles. Antiviral Res 2016; 135:97-107. [PMID: 27743916 PMCID: PMC7113682 DOI: 10.1016/j.antiviral.2016.10.005] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 08/23/2016] [Accepted: 10/12/2016] [Indexed: 12/13/2022]
Abstract
Replication of eukaryotic positive-stranded RNA viruses is usually linked to the presence of membrane-associated replicative organelles. The purpose of this review is to discuss the function of proteins responsible for formation of the coronavirus replicative organelle. This will be done by identifying domains that are conserved across the order Nidovirales, and by summarizing what is known about function and structure at the level of protein domains. Bioinformatics reveals a new domain-level map of coronavirus nsp3-nsp6. Domain-level protein variability is a tool for functional annotation. Ten nsp3 domains are conserved in all known coronaviruses. Review of the role of the nsp5 main protease in RNA synthesis.
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Affiliation(s)
- Benjamin W Neuman
- University of Reading, School of Biological Sciences, RG6 6AH, United Kingdom; College of STEM, Texas A&M University-Texarkana, Texarkana, TX 75503, USA.
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20
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Maier HJ, Neuman BW, Bickerton E, Keep SM, Alrashedi H, Hall R, Britton P. Extensive coronavirus-induced membrane rearrangements are not a determinant of pathogenicity. Sci Rep 2016; 6:27126. [PMID: 27255716 PMCID: PMC4891661 DOI: 10.1038/srep27126] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 05/12/2016] [Indexed: 12/16/2022] Open
Abstract
Positive-strand RNA (+RNA) viruses rearrange cellular membranes during replication, possibly in order to concentrate and arrange viral replication machinery for efficient viral RNA synthesis. Our previous work showed that in addition to the conserved coronavirus double membrane vesicles (DMVs), Beau-R, an apathogenic strain of avian Gammacoronavirus infectious bronchitis virus (IBV), induces regions of ER that are zippered together and tethered open-necked double membrane spherules that resemble replication organelles induced by other +RNA viruses. Here we compared structures induced by Beau-R with the pathogenic lab strain M41 to determine whether membrane rearrangements are strain dependent. Interestingly, M41 was found to have a low spherule phenotype. We then compared a panel of pathogenic, mild and attenuated IBV strains in ex vivo tracheal organ culture (TOC). Although the low spherule phenotype of M41 was conserved in TOCs, each of the other tested IBV strains produced DMVs, zippered ER and spherules. Furthermore, there was a significant correlation for the presence of DMVs with spherules, suggesting that these structures are spatially and temporally linked. Our data indicate that virus induced membrane rearrangements are fundamentally linked to the viral replicative machinery. However, coronavirus replicative apparatus clearly has the plasticity to function in different structural contexts.
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Affiliation(s)
| | - Benjamin W. Neuman
- School of Biological Sciences, University of Reading, Reading, Berkshire, UK
| | | | | | - Hasan Alrashedi
- School of Biological Sciences, University of Reading, Reading, Berkshire, UK
| | - Ross Hall
- The Pirbright Institute, Pirbright, Surrey, UK
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21
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van der Hoeven B, Oudshoorn D, Koster AJ, Snijder EJ, Kikkert M, Bárcena M. Biogenesis and architecture of arterivirus replication organelles. Virus Res 2016; 220:70-90. [PMID: 27071852 PMCID: PMC7111217 DOI: 10.1016/j.virusres.2016.04.001] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 04/01/2016] [Indexed: 02/06/2023]
Abstract
Arterivirus RNA synthesis presumably is associated with double-membrane vesicles (DMVs). Putative intermediates in DMV formation were detected in infected cells. Arterivirus-induced DMVs form a highly interconnected reticulovesicular network (RVN). Expression of the nsp2-3 replicase polyprotein fragment induces a comparable RVN. Nsp2-7 expression results in smaller DMVs, closer in size to DMVs found in infection.
All eukaryotic positive-stranded RNA (+RNA) viruses appropriate host cell membranes and transform them into replication organelles, specialized micro-environments that are thought to support viral RNA synthesis. Arteriviruses (order Nidovirales) belong to the subset of +RNA viruses that induce double-membrane vesicles (DMVs), similar to the structures induced by e.g. coronaviruses, picornaviruses and hepatitis C virus. In the last years, electron tomography has revealed substantial differences between the structures induced by these different virus groups. Arterivirus-induced DMVs appear to be closed compartments that are continuous with endoplasmic reticulum membranes, thus forming an extensive reticulovesicular network (RVN) of intriguing complexity. This RVN is remarkably similar to that described for the distantly related coronaviruses (also order Nidovirales) and sets them apart from other DMV-inducing viruses analysed to date. We review here the current knowledge and open questions on arterivirus replication organelles and discuss them in the light of the latest studies on other DMV-inducing viruses, particularly coronaviruses. Using the equine arteritis virus (EAV) model system and electron tomography, we present new data regarding the biogenesis of arterivirus-induced DMVs and uncover numerous putative intermediates in DMV formation. We generated cell lines that can be induced to express specific EAV replicase proteins and showed that DMVs induced by the transmembrane proteins nsp2 and nsp3 form an RVN and are comparable in topology and architecture to those formed during viral infection. Co-expression of the third EAV transmembrane protein (nsp5), expressed as part of a self-cleaving polypeptide that mimics viral polyprotein processing in infected cells, led to the formation of DMVs whose size was more homogenous and closer to what is observed upon EAV infection, suggesting a regulatory role for nsp5 in modulating membrane curvature and DMV formation.
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Affiliation(s)
- Barbara van der Hoeven
- Electron Microscopy Section, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Diede Oudshoorn
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Abraham J Koster
- Electron Microscopy Section, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Eric J Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Marjolein Kikkert
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands.
| | - Montserrat Bárcena
- Electron Microscopy Section, Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands.
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22
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Dissection of amino-terminal functional domains of murine coronavirus nonstructural protein 3. J Virol 2015; 89:6033-47. [PMID: 25810552 DOI: 10.1128/jvi.00197-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 03/19/2015] [Indexed: 01/08/2023] Open
Abstract
UNLABELLED Coronaviruses, the largest RNA viruses, have a complex program of RNA synthesis that entails genome replication and transcription of subgenomic mRNAs. RNA synthesis by the prototype coronavirus mouse hepatitis virus (MHV) is carried out by a replicase-transcriptase composed of 16 nonstructural protein (nsp) subunits. Among these, nsp3 is the largest and the first to be inserted into the endoplasmic reticulum. nsp3 comprises multiple structural domains, including two papain-like proteases (PLPs) and a highly conserved ADP-ribose-1″-phosphatase (ADRP) macrodomain. We have previously shown that the ubiquitin-like domain at the amino terminus of nsp3 is essential and participates in a critical interaction with the viral nucleocapsid protein early in infection. In the current study, we exploited atypical expression schemes to uncouple PLP1 from the processing of nsp1 and nsp2 in order to investigate the requirements of nsp3 domains for viral RNA synthesis. In the first strategy, a mutant was created in which replicase polyprotein translation initiated with nsp3, thereby establishing that complete elimination of nsp1 and nsp2 does not abolish MHV viability. In the second strategy, a picornavirus autoprocessing element was used to separate a truncated nsp1 from nsp3. This provided a platform for further dissection of amino-terminal domains of nsp3. From this, we found that catalytic mutation of PLP1 or complete deletion of PLP1 and the adjacent ADRP domain was tolerated by the virus. These results showed that neither the PLP1 domain nor the ADRP domain of nsp3 provides integral activities essential for coronavirus genomic or subgenomic RNA synthesis. IMPORTANCE The largest component of the coronavirus replicase-transcriptase complex, nsp3, contains multiple modules, many of which do not have clearly defined functions in genome replication or transcription. These domains may play direct roles in RNA synthesis, or they may have evolved for other purposes, such as to combat host innate immunity. We initiated a dissection of MHV nsp3 aimed at identifying those activities or structures in this huge molecule that are essential to replicase activity. We found that both PLP1 and ADRP could be entirely deleted, provided that the requirement for proteolytic processing by PLP1 was offset by an alternative mechanism. This demonstrated that neither PLP1 nor ADRP plays an essential role in coronavirus RNA synthesis.
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23
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V'kovski P, Al-Mulla H, Thiel V, Neuman BW. New insights on the role of paired membrane structures in coronavirus replication. Virus Res 2014; 202:33-40. [PMID: 25550072 PMCID: PMC7114427 DOI: 10.1016/j.virusres.2014.12.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 12/16/2014] [Accepted: 12/18/2014] [Indexed: 12/22/2022]
Abstract
Coronavirus replication is tied to formation of double-membrane organelles (DMOs). DMO-making genes are conserved across the Nidovirales. Here, we interpret recent experiments on the role and importance of coronavirus DMOs.
The replication of coronaviruses, as in other positive-strand RNA viruses, is closely tied to the formation of membrane-bound replicative organelles inside infected cells. The proteins responsible for rearranging cellular membranes to form the organelles are conserved not just among the Coronaviridae family members, but across the order Nidovirales. Taken together, these observations suggest that the coronavirus replicative organelle plays an important role in viral replication, perhaps facilitating the production or protection of viral RNA. However, the exact nature of this role, and the specific contexts under which it is important have not been fully elucidated. Here, we collect and interpret the recent experimental evidence about the role and importance of membrane-bound organelles in coronavirus replication.
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Affiliation(s)
- Philip V'kovski
- Federal Institute of Virology and Immunology, Mittelhäusern, Bern, Switzerland; Graduate School for Biomedical Sciences, University of Bern, Switzerland
| | - Hawaa Al-Mulla
- School of Biological Sciences, University of Reading, Reading, Berkshire, United Kingdom; University of Baghdad, College of Science, Baghdad, Iraq
| | - Volker Thiel
- Federal Institute of Virology and Immunology, Mittelhäusern, Bern, Switzerland; Vetsuisse Faculty, University of Bern, Bern, Switzerland.
| | - Benjamin W Neuman
- School of Biological Sciences, University of Reading, Reading, Berkshire, United Kingdom.
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24
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Mutations across murine hepatitis virus nsp4 alter virus fitness and membrane modifications. J Virol 2014; 89:2080-9. [PMID: 25473044 DOI: 10.1128/jvi.02776-14] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
UNLABELLED A common feature of infection by positive-sense RNA virus is the modification of host cell cytoplasmic membranes that serve as sites of viral RNA synthesis. Coronaviruses induce double-membrane vesicles (DMVs), but the role of DMVs in replication and virus fitness remains unclear. Coronaviruses encode 16 nonstructural proteins (nsps), three of which, nsp3, nsp4, and nsp6, are necessary and sufficient for DMV formation. It has been shown previously that mutations in murine hepatitis virus (MHV) nsp4 loop 1 that alter nsp4 glycosylation are associated with disrupted DMV formation and result in changes in virus replication and RNA synthesis. However, it is not known whether DMV morphology or another function of nsp4 glycosylation is responsible for effects on virus replication. In this study, we tested whether mutations across nsp4, both alone and in combination with mutations that abolish nsp4 glycosylation, affected DMV formation, replication, and fitness. Residues in nsp4 distinct from glycosylation sites, particularly in the endoplasmic reticulum (ER) luminal loop 1, independently disrupted both the number and morphology of DMVs and exacerbated DMV changes associated with loss of glycosylation. Mutations that altered DMV morphology but not glycosylation did not affect virus fitness while viruses lacking nsp4 glycosylation exhibited a loss in fitness. The results support the hypothesis that DMV morphology and numbers are not key determinants of virus fitness. The results also suggest that nsp4 glycosylation serves roles in replication in addition to the organization and stability of MHV-induced double-membrane vesicles. IMPORTANCE All positive-sense RNA viruses modify host cytoplasmic membranes for viral replication complex formation. Thus, defining the mechanisms of virus-induced membrane modifications is essential for both understanding virus replication and development of novel approaches to virus inhibition. Coronavirus-induced membrane changes include double-membrane vesicles (DMVs) and convoluted membranes. Three viral nonstructural proteins (nsps), nsp3, nsp4, and nsp6, are known to be required for DMV formation. It is unknown how these proteins induce membrane modification or which regions of the proteins are involved in DMV formation and stability. In this study, we show that mutations across nsp4 delay virus replication and disrupt DMV formation and that loss of nsp4 glycosylation is associated with a substantial fitness cost. These results support a critical role for nsp4 in DMV formation and virus fitness.
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25
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Neuman BW, Angelini MM, Buchmeier MJ. Does form meet function in the coronavirus replicative organelle? Trends Microbiol 2014; 22:642-7. [PMID: 25037114 PMCID: PMC7127430 DOI: 10.1016/j.tim.2014.06.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 06/10/2014] [Accepted: 06/13/2014] [Indexed: 12/14/2022]
Abstract
If we use the analogy of a virus as a living entity, then the replicative organelle is the part of the body where its metabolic and reproductive activities are concentrated. Recent studies have illuminated the intricately complex replicative organelles of coronaviruses, a group that includes the largest known RNA virus genomes. This review takes a virus-centric look at the coronavirus replication transcription complex organelle in the context of the wider world of positive sense RNA viruses, examining how the mechanisms of protein expression and function act to produce the factories that power the viral replication cycle.
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Affiliation(s)
- Benjamin W Neuman
- School of Biological Sciences, University of Reading, Reading, Berkshire, UK.
| | - Megan M Angelini
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA, USA
| | - Michael J Buchmeier
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA, USA; Department of Medicine, Division of Infectious Disease, University of California Irvine, Irvine, CA, USA
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26
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Blanchard E, Roingeard P. Virus-induced double-membrane vesicles. Cell Microbiol 2014; 17:45-50. [PMID: 25287059 PMCID: PMC5640787 DOI: 10.1111/cmi.12372] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 09/25/2014] [Accepted: 09/29/2014] [Indexed: 12/27/2022]
Abstract
Many viruses that replicate in the cytoplasm compartmentalize their genome replication and transcription in specific subcellular microenvironments or organelle‐like structures, to increase replication efficiency and protect against host cell defences. Recent studies have investigated the complex membrane rearrangements induced by diverse positive‐strand RNA viruses, which are of two morphotypes : membrane invagination towards the lumen of the endoplasmic reticulum (ER) or other specifically targeted organelles and double‐membrane vesicles (DMVs) formed by extrusion of the ER membrane. DMVs resemble small autophagosomes and the viruses inducing these intriguing organelles are known to promote autophagy, suggesting a potential link between DMVs and the autophagic pathway. In this review, we summarize recent findings concerning the biogenesis, architecture and role of DMVs in the life cycle of viruses from different families and discuss their possible connection to autophagy or other related pathways.
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Affiliation(s)
- Emmanuelle Blanchard
- INSERM U966, Université François Rabelais and CHRU de Tours, Tours, Cedex 37032, France
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27
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Maier HJ, Hawes PC, Keep SM, Britton P. Spherules and IBV. Bioengineered 2014; 5:288-92. [PMID: 25482229 PMCID: PMC4156489 DOI: 10.4161/bioe.29323] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 05/21/2014] [Accepted: 05/22/2014] [Indexed: 01/29/2023] Open
Abstract
Infectious bronchitis virus (IBV) is an economically important virus infecting chickens, causing large losses to the poultry industry globally. While vaccines are available, there is a requirement for novel vaccine strategies due to high strain variation and poor cross-protection. This requires a more detailed understanding of virus-host cell interactions to identify candidates for targeted virus attenuation. One key area of research in the positive sense RNA virus field, due to its central role in virus replication, is the induction of cellular membrane rearrangements by this class of viruses for the assembly of virus replication complexes. In our recent work, we identified the structures induced by IBV during infection of cultured cells, as well as primary cells and ex vivo organ culture. We identified structures novel to the coronavirus family, which strongly resemble replication sites of other positive sense RNA viruses. We have begun to extend this work using recombinant IBVs, which are chimera of different virus strains to study the role of viral proteins in the induction of membrane rearrangements.
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Affiliation(s)
- Helena J Maier
- The Pirbright Institute; Compton Laboratory; Compton, UK
| | | | - Sarah M Keep
- The Pirbright Institute; Compton Laboratory; Compton, UK
| | - Paul Britton
- The Pirbright Institute; Compton Laboratory; Compton, UK
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