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Müller M, Herrmann A, Fujita S, Uriu K, Kruth C, Strange A, Kolberg JE, Schneider M, Ito J, Müller MA, Drosten C, Ensser A, Sato K, Sauter D. ORF3c is expressed in SARS-CoV-2-infected cells and inhibits innate sensing by targeting MAVS. EMBO Rep 2023; 24:e57137. [PMID: 37870297 DOI: 10.15252/embr.202357137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 10/05/2023] [Accepted: 10/06/2023] [Indexed: 10/24/2023] Open
Abstract
Most SARS-CoV-2 proteins are translated from subgenomic RNAs (sgRNAs). While the majority of these sgRNAs are monocistronic, some viral mRNAs encode more than one protein. One example is the ORF3a sgRNA that also encodes ORF3c, an enigmatic 41-amino-acid peptide. Here, we show that ORF3c is expressed in SARS-CoV-2-infected cells and suppresses RIG-I- and MDA5-mediated IFN-β induction. ORF3c interacts with the signaling adaptor MAVS, induces its C-terminal cleavage, and inhibits the interaction of RIG-I with MAVS. The immunosuppressive activity of ORF3c is conserved among members of the subgenus sarbecovirus, including SARS-CoV and coronaviruses isolated from bats. Notably, however, the SARS-CoV-2 delta and kappa variants harbor premature stop codons in ORF3c, demonstrating that this reading frame is not essential for efficient viral replication in vivo and is likely compensated by other viral proteins. In agreement with this, disruption of ORF3c does not significantly affect SARS-CoV-2 replication in CaCo-2, CaLu-3, or Rhinolophus alcyone cells. In summary, we here identify ORF3c as an immune evasion factor of SARS-CoV-2 that suppresses innate sensing in infected cells.
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Affiliation(s)
- Martin Müller
- Institute for Medical Virology and Epidemiology of Viral Diseases, University Hospital Tübingen, Tübingen, Germany
| | - Alexandra Herrmann
- Institute for Clinical and Molecular Virology, University Hospital, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Shigeru Fujita
- Division of Systems Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
- Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Keiya Uriu
- Division of Systems Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
- Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Carolin Kruth
- Institute for Medical Virology and Epidemiology of Viral Diseases, University Hospital Tübingen, Tübingen, Germany
| | - Adam Strange
- Division of Systems Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Jan E Kolberg
- Institute for Medical Virology and Epidemiology of Viral Diseases, University Hospital Tübingen, Tübingen, Germany
| | - Markus Schneider
- Institute for Medical Virology and Epidemiology of Viral Diseases, University Hospital Tübingen, Tübingen, Germany
| | - Jumpei Ito
- Division of Systems Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Marcel A Müller
- Institute of Virology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Christian Drosten
- Institute of Virology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Armin Ensser
- Institute for Clinical and Molecular Virology, University Hospital, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Kei Sato
- Division of Systems Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
- Institute of Virology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
- International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
- International Vaccine Design Center, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
- Graduate School of Frontier Sciences, The University of Tokyo, Chiba, Japan
- CREST, Japan Science and Technology Agency, Saitama, Japan
| | - Daniel Sauter
- Institute for Medical Virology and Epidemiology of Viral Diseases, University Hospital Tübingen, Tübingen, Germany
- Division of Systems Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
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Cao J, Shi M, Zhu L, Li X, Li A, Wu SY, Chiang CM, Zhang Y. The matrix protein of respiratory syncytial virus suppresses interferon signaling via RACK1 association. J Virol 2023; 97:e0074723. [PMID: 37712706 PMCID: PMC10617408 DOI: 10.1128/jvi.00747-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 07/13/2023] [Indexed: 09/16/2023] Open
Abstract
IMPORTANCE Respiratory syncytial virus (RSV) matrix (M) protein is indispensable for virion assembly and release. It is localized to the nucleus during early infection to perturb host transcription. However, the function of RSV M protein in other cellular activities remains poorly understood. In this study, several interferon response-associated host factors, including RACK1, were identified by proteomic analysis as RSV M interactors. Knockdown of RACK1 attenuates RSV-restricted IFN signaling leading to enhanced host defense against RSV infection, unraveling a role of M protein in antagonizing IFN response via association with RACK1. Our study uncovers a previously unrecognized mechanism of immune evasion by RSV M protein and identifies RACK1 as a novel host factor recruited by RSV, highlighting RACK1 as a potential new target for RSV therapeutics development.
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Affiliation(s)
- Jingjing Cao
- State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong University, Qingdao, Shandong, China
| | - Menghan Shi
- State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong University, Qingdao, Shandong, China
| | - Lina Zhu
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology, School of Life Sciences, Advanced Medical Research Institute, Shandong University, Qingdao, Shandong, China
| | - Xiangzhi Li
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology, School of Life Sciences, Advanced Medical Research Institute, Shandong University, Qingdao, Shandong, China
| | - Aiying Li
- State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong University, Qingdao, Shandong, China
| | - Shwu-Yuan Wu
- Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Cheng-Ming Chiang
- Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Youming Zhang
- State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong University, Qingdao, Shandong, China
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Abstract
Nipah virus (NiV) is an emerging and deadly zoonotic paramyxovirus that is responsible for periodic epidemics of acute respiratory illness and encephalitis in humans. Previous studies have shown that the NiV V protein antagonizes host antiviral immunity, but the molecular mechanism is incompletely understood. To address this gap, we biochemically characterized NiV V binding to the host pattern recognition receptor MDA5. We find that the C-terminal domain of NiV V (VCTD) is sufficient to bind the MDA5SF2 domain when recombinantly co-expressed in bacteria. Analysis by hydrogen-deuterium exchange mass spectrometry (HDX-MS) studies revealed that NiV VCTD is conformationally dynamic, and binding to MDA5 reduces the dynamics of VCTD. Our results also suggest that the β-sheet region in between the MDA5 Hel1, Hel2, and Hel2i domains exhibits rapid HDX. Upon VCTD binding, these β-sheet and adjacent residues show significant protection. Collectively, our findings suggest that NiV V binding disrupts the helicase fold and dynamics of MDA5 to antagonize host antiviral immunity.
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Affiliation(s)
- Nicole D. Wagner
- Division of Infectious Diseases, John T. Milliken Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, United States
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Hejun Liu
- Division of Infectious Diseases, John T. Milliken Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, United States
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, United States
| | - Henry W. Rohrs
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Gaya K. Amarasinghe
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, United States
| | - Michael L. Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Daisy W. Leung
- Division of Infectious Diseases, John T. Milliken Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, United States
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, United States
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Lussi C, de Martin E, Schweizer M. Positively Charged Amino Acids in the Pestiviral E rns Control Cell Entry, Endoribonuclease Activity and Innate Immune Evasion. Viruses 2021; 13:v13081581. [PMID: 34452446 PMCID: PMC8402660 DOI: 10.3390/v13081581] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/04/2021] [Accepted: 08/05/2021] [Indexed: 11/16/2022] Open
Abstract
The genus Pestivirus, family Flaviviridae, includes four economically important viruses of livestock, i.e., bovine viral diarrhea virus-1 (BVDV-1) and -2 (BVDV-2), border disease virus (BDV) and classical swine fever virus (CSFV). Erns and Npro, both expressed uniquely by pestiviruses, counteract the host's innate immune defense by interfering with the induction of interferon (IFN) synthesis. The structural envelope protein Erns also exists in a soluble form and, by its endoribonuclease activity, degrades immunostimulatory RNA prior to their activation of pattern recognition receptors. Here, we show that at least three out of four positively-charged residues in the C-terminal glycosaminoglycan (GAG)-binding site of BVDV-Erns are required for efficient cell entry, and that a positively charged region more upstream is not involved in cell entry but rather in RNA-binding. Moreover, the C-terminal domain on its own determines intracellular targeting, as GFP fused to the C-terminal amino acids of Erns was found at the same compartments as wt Erns. In summary, RNase activity and uptake into cells are both required for Erns to act as an IFN antagonist, and the C-terminal amphipathic helix containing the GAG-binding site determines the efficiency of cell entry and its intracellular localization.
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Affiliation(s)
- Carmela Lussi
- Institute of Virology and Immunology (IVI), CH-3001 Bern, Switzerland; (C.L.); (E.d.M.)
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, CH-3001 Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences (GCB), University of Bern, CH-3012 Bern, Switzerland
| | - Elena de Martin
- Institute of Virology and Immunology (IVI), CH-3001 Bern, Switzerland; (C.L.); (E.d.M.)
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, CH-3001 Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences (GCB), University of Bern, CH-3012 Bern, Switzerland
| | - Matthias Schweizer
- Institute of Virology and Immunology (IVI), CH-3001 Bern, Switzerland; (C.L.); (E.d.M.)
- Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, CH-3001 Bern, Switzerland
- Correspondence:
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5
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Nan FL, Zhang H, Nan WL, Xie CZ, Ha Z, Chen X, Xu XH, Qian J, Qiu XS, Ge JY, Bu ZG, Zhang Y, Lu HJ, Jin NY. Lentogenic NDV V protein inhibits IFN responses and represses cell apoptosis. Vet Microbiol 2021; 261:109181. [PMID: 34399297 DOI: 10.1016/j.vetmic.2021.109181] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 07/01/2021] [Indexed: 01/13/2023]
Abstract
The V protein of Newcastle disease virus (NDV) has been shown to inhibit the secretion of interferon (IFN) during infection, which is responsible for the promotion of NDV pathogenicity. However, the ability of the V protein to suppress host innate immunity is not well understood. In this study, we explored the function of V protein and its relationship with virulence by generating V protein-inserted recombinant (r) NDVs. Using rNDVs as a model, we examined the efficiency of infection, IFN responses, and apoptosis of host cells during infection. We found that viral propagation occurred smoothly when V protein from lentogenic NDV is inserted instead of the V protein from the velogenic strain. The infection of lentogenic V protein-inserted rNDV induced less expression of IFNs and downstream antiviral proteins via efficient degradation of p-STAT1 and MDA5. Moreover, velogenic V protein triggered a higher apoptosis rate during infection thereby restricting the replication of NDV. Conversely, lentogenic V protein inhibits IFN responses efficiently and induces less apoptosis compared to the velogenic strain. Our findings provide a novel understanding of the role of V protein in NDV pathogenicity.
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Affiliation(s)
- Fu Long Nan
- College of Veterinary Medicine, College of Animal Science, Jilin University, Changchun, 130062, China; Institute of Military Veterinary Medicine, Academy of Military Medical Sciences, Changchun, 130122, China
| | - He Zhang
- Institute of Military Veterinary Medicine, Academy of Military Medical Sciences, Changchun, 130122, China
| | - Wen Long Nan
- China Animal Health and Epidemiology Center, Qingdao, 266032, China
| | - Chang Zhan Xie
- Institute of Military Veterinary Medicine, Academy of Military Medical Sciences, Changchun, 130122, China
| | - Zhuo Ha
- Institute of Military Veterinary Medicine, Academy of Military Medical Sciences, Changchun, 130122, China
| | - Xing Chen
- Changchun Institute of Biological Products Co., Ltd. Changchun, 130012, China
| | - Xiao Hong Xu
- College of Veterinary Medicine, College of Animal Science, Jilin University, Changchun, 130062, China
| | - Jing Qian
- Institute of Veterinary Medicine, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, China
| | - Xu Sheng Qiu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, 200241, China
| | - Jin Ying Ge
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, 150001, China
| | - Zhi Gao Bu
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, 150001, China
| | - Ying Zhang
- College of Veterinary Medicine, College of Animal Science, Jilin University, Changchun, 130062, China.
| | - Hui Jun Lu
- Institute of Military Veterinary Medicine, Academy of Military Medical Sciences, Changchun, 130122, China.
| | - Ning Yi Jin
- College of Veterinary Medicine, College of Animal Science, Jilin University, Changchun, 130062, China; Institute of Military Veterinary Medicine, Academy of Military Medical Sciences, Changchun, 130122, China.
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6
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Pei J, Wagner ND, Zou AJ, Chatterjee S, Borek D, Cole AR, Kim PJ, Basler CF, Otwinowski Z, Gross ML, Amarasinghe GK, Leung DW. Structural basis for IFN antagonism by human respiratory syncytial virus nonstructural protein 2. Proc Natl Acad Sci U S A 2021; 118:e2020587118. [PMID: 33649232 PMCID: PMC7958447 DOI: 10.1073/pnas.2020587118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Human respiratory syncytial virus (RSV) nonstructural protein 2 (NS2) inhibits host interferon (IFN) responses stimulated by RSV infection by targeting early steps in the IFN-signaling pathway. But the molecular mechanisms related to how NS2 regulates these processes remain incompletely understood. To address this gap, here we solved the X-ray crystal structure of NS2. This structure revealed a unique fold that is distinct from other known viral IFN antagonists, including RSV NS1. We also show that NS2 directly interacts with an inactive conformation of the RIG-I-like receptors (RLRs) RIG-I and MDA5. NS2 binding prevents RLR ubiquitination, a process critical for prolonged activation of downstream signaling. Structural analysis, including by hydrogen-deuterium exchange coupled to mass spectrometry, revealed that the N terminus of NS2 is essential for binding to the RIG-I caspase activation and recruitment domains. N-terminal mutations significantly diminish RIG-I interactions and result in increased IFNβ messenger RNA levels. Collectively, our studies uncover a previously unappreciated regulatory mechanism by which NS2 further modulates host responses and define an approach for targeting host responses.
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Affiliation(s)
- Jingjing Pei
- John T. Milliken Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, MO 63110
| | - Nicole D Wagner
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63110
| | - Angela J Zou
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
| | - Srirupa Chatterjee
- John T. Milliken Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, MO 63110
| | - Dominika Borek
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Aidan R Cole
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
| | - Preston J Kim
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
| | - Christopher F Basler
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303
| | - Zbyszek Otwinowski
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Michael L Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63110
| | - Gaya K Amarasinghe
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
| | - Daisy W Leung
- John T. Milliken Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, MO 63110;
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
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Lau S, Weber F. Nuclear pore protein Nup98 is involved in replication of Rift Valley fever virus and nuclear import of virulence factor NSs. J Gen Virol 2020; 101:712-716. [PMID: 31671053 PMCID: PMC7660236 DOI: 10.1099/jgv.0.001347] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 10/01/2019] [Indexed: 12/17/2022] Open
Abstract
The non-structural protein NSs is the main virulence factor of Rift Valley fever virus, a major zoonotic pathogen in Africa. NSs forms large aggregates in the nucleus and impairs induction of the antiviral type I IFN system by several mechanisms, including degradation of subunit p62 of the general RNA polymerase II transcription factor TFIIH. Here, we show that depletion of the nuclear pore protein Nup98 affects the nuclear import of NSs. Nonetheless, NSs was still able to degrade TFIIH-p62 under these conditions. Depletion of Nup98, however, had a negative effect on Rift Valley fever virus multiplication. Our data thus indicate that NSs utilizes Nup98 for import into the nucleus, but also plays a general role in the viral replication cycle.
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Affiliation(s)
- Simone Lau
- Institute for Virology, FB10-Veterinary Medicine, Justus-Liebig University, D-35392 Giessen, Germany
- Institute for Virology, Philipps-University Marburg, D-35043 Marburg, Germany
| | - Friedemann Weber
- Institute for Virology, FB10-Veterinary Medicine, Justus-Liebig University, D-35392 Giessen, Germany
- Institute for Virology, Philipps-University Marburg, D-35043 Marburg, Germany
- German Center for Infection Research (DZIF), partner sites Marburg and Giessen, Germany
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8
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Deng X, Chen Y, Mielech AM, Hackbart M, Kesely KR, Mettelman RC, O'Brien A, Chapman ME, Mesecar AD, Baker SC. Structure-Guided Mutagenesis Alters Deubiquitinating Activity and Attenuates Pathogenesis of a Murine Coronavirus. J Virol 2020; 94:e01734-19. [PMID: 32188728 DOI: 10.1128/JVI.01734-19] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 03/09/2020] [Indexed: 12/25/2022] Open
Abstract
Coronaviruses employ a genetic economy by encoding multifunctional proteins that function in viral replication and also modify the host environment to disarm the innate immune response. The coronavirus papain-like protease 2 (PLP2) domain possesses protease activity, which cleaves the viral replicase polyprotein, and also DUB activity (deconjugating ubiquitin/ubiquitin-like molecules from modified substrates) using identical catalytic residues. To separate the DUB activity from the protease activity, we employed a structure-guided mutagenesis approach and identified residues that are important for ubiquitin binding. We found that mutating the ubiquitin-binding residues results in a PLP2 that has reduced DUB activity but retains protease activity. We engineered a recombinant murine coronavirus to express the DUB mutant and showed that the DUB mutant virus activated an earlier type I interferon response in macrophages and exhibited reduced replication in mice. The results of this study demonstrate that PLP2/DUB is an interferon antagonist and a virulence trait of coronaviruses. Coronaviruses express a multifunctional papain-like protease, termed papain-like protease 2 (PLP2). PLP2 acts as a protease that cleaves the viral replicase polyprotein and as a deubiquitinating (DUB) enzyme which removes ubiquitin (Ub) moieties from ubiquitin-conjugated proteins. Previous in vitro studies implicated PLP2/DUB activity as a negative regulator of the host interferon (IFN) response, but the role of DUB activity during virus infection was unknown. Here, we used X-ray structure-guided mutagenesis and functional studies to identify amino acid substitutions within the ubiquitin-binding surface of PLP2 that reduced DUB activity without affecting polyprotein processing activity. We engineered a DUB mutation (Asp1772 to Ala) into a murine coronavirus and evaluated the replication and pathogenesis of the DUB mutant virus (DUBmut) in cultured macrophages and in mice. We found that the DUBmut virus replicates similarly to the wild-type (WT) virus in cultured cells, but the DUBmut virus activates an IFN response at earlier times compared to the wild-type virus infection in macrophages, consistent with DUB activity negatively regulating the IFN response. We compared the pathogenesis of the DUBmut virus to that of the wild-type virus and found that the DUBmut-infected mice had a statistically significant reduction (P < 0.05) in viral titer in liver and spleen at day 5 postinfection (d p.i.), although both wild-type and DUBmut virus infections resulted in similar liver pathology. Overall, this study demonstrates that structure-guided mutagenesis aids the identification of critical determinants of the PLP2-ubiquitin complex and that PLP2/DUB activity plays a role as an interferon antagonist in coronavirus pathogenesis. IMPORTANCE Coronaviruses employ a genetic economy by encoding multifunctional proteins that function in viral replication and also modify the host environment to disarm the innate immune response. The coronavirus papain-like protease 2 (PLP2) domain possesses protease activity, which cleaves the viral replicase polyprotein, and also DUB activity (deconjugating ubiquitin/ubiquitin-like molecules from modified substrates) using identical catalytic residues. To separate the DUB activity from the protease activity, we employed a structure-guided mutagenesis approach and identified residues that are important for ubiquitin binding. We found that mutating the ubiquitin-binding residues results in a PLP2 that has reduced DUB activity but retains protease activity. We engineered a recombinant murine coronavirus to express the DUB mutant and showed that the DUB mutant virus activated an earlier type I interferon response in macrophages and exhibited reduced replication in mice. The results of this study demonstrate that PLP2/DUB is an interferon antagonist and a virulence trait of coronaviruses.
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9
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Volk A, Hackbart M, Deng X, Cruz-Pulido Y, O'Brien A, Baker SC. Coronavirus Endoribonuclease and Deubiquitinating Interferon Antagonists Differentially Modulate the Host Response during Replication in Macrophages. J Virol 2020; 94:e00178-20. [PMID: 32188729 DOI: 10.1128/JVI.00178-20] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 03/09/2020] [Indexed: 12/17/2022] Open
Abstract
Macrophages are an important cell type during coronavirus infections because they “notice” the infection and respond by inducing type I interferons, which limits virus replication. In turn, coronaviruses encode proteins that mitigate the cell’s ability to signal an interferon response. Here, we evaluated the host macrophage response to two independent mutant coronaviruses, one with reduced deubiquitinating activity (DUBmut) and the other containing an inactivated endoribonuclease (EndoUmut). We observed a rapid, robust, and focused response to the EndoUmut virus, which was characterized by enhanced expression of interferon and interferon-related genes. In contrast, wild-type virus and the DUBmut virus elicited a more limited interferon response and ultimately activated over 2,800 genes, including players in the unfolded protein response and proinflammatory pathways associated with progression of significant disease. This study reveals that EndoU activity substantially contributes to the ability of coronaviruses to evade the host innate response and to replicate in macrophages. Coronaviruses (CoVs) encode multiple interferon (IFN) antagonists that modulate the host response to virus replication. Here, we evaluated the host transcriptional response to infection with murine coronaviruses encoding independent mutations in one of two different viral antagonists, the deubiquitinase (DUB) within nonstructural protein 3 or the endoribonuclease (EndoU) within nonstructural protein 15. We used transcriptomics approaches to compare the scope and kinetics of the host response to the wild-type (WT), DUBmut, and EndoUmut viruses in infected macrophages. We found that the EndoUmut virus activates a focused response that predominantly involves type I interferons and interferon-related genes, whereas the WT and DUBmut viruses more broadly stimulate upregulation of over 2,800 genes, including networks associated with activating the unfolded protein response (UPR) and the proinflammatory response associated with viral pathogenesis. This study highlights the role of viral interferon antagonists in shaping the kinetics and magnitude of the host response during virus infection and demonstrates that inactivating a dominant viral antagonist, the coronavirus endoribonuclease, dramatically alters the host response in macrophages. IMPORTANCE Macrophages are an important cell type during coronavirus infections because they “notice” the infection and respond by inducing type I interferons, which limits virus replication. In turn, coronaviruses encode proteins that mitigate the cell’s ability to signal an interferon response. Here, we evaluated the host macrophage response to two independent mutant coronaviruses, one with reduced deubiquitinating activity (DUBmut) and the other containing an inactivated endoribonuclease (EndoUmut). We observed a rapid, robust, and focused response to the EndoUmut virus, which was characterized by enhanced expression of interferon and interferon-related genes. In contrast, wild-type virus and the DUBmut virus elicited a more limited interferon response and ultimately activated over 2,800 genes, including players in the unfolded protein response and proinflammatory pathways associated with progression of significant disease. This study reveals that EndoU activity substantially contributes to the ability of coronaviruses to evade the host innate response and to replicate in macrophages.
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10
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Amatya P, Wagner N, Chen G, Luthra P, Shi L, Borek D, Pavlenco A, Rohrs H, Basler CF, Sidhu SS, Gross ML, Leung DW. Inhibition of Marburg Virus RNA Synthesis by a Synthetic Anti-VP35 Antibody. ACS Infect Dis 2019; 5:1385-1396. [PMID: 31120240 DOI: 10.1021/acsinfecdis.9b00091] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Marburg virus causes sporadic outbreaks of severe hemorrhagic fever with high case fatality rates. Approved, effective, and safe therapeutic or prophylactic countermeasures are lacking. To address this, we used phage display to engineer a synthetic antibody, sFab H3, which binds the Marburg virus VP35 protein (mVP35). mVP35 is a critical cofactor of the viral replication complex and a viral immune antagonist. sFab H3 displayed high specificity for mVP35 and not for the closely related Ebola virus VP35. sFab H3 inhibited viral-RNA synthesis in a minigenome assay, suggesting its potential use as an antiviral. We characterized sFab H3 by a combination of biophysical and biochemical methods, and a crystal structure of the complex solved to 1.7 Å resolution defined the molecular interface between the sFab H3 and mVP35 interferon inhibitory domain. Our study identifies mVP35 as a therapeutic target using an approach that provides a framework for generating engineered Fabs targeting other viral proteins.
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Affiliation(s)
- Parmeshwar Amatya
- Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, United States
- Department of Pathology and Immunology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, United States
| | - Nicole Wagner
- Department of Chemistry, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, United States
| | - Gang Chen
- Donnelly Centre for Cellular and Biomolecular Research, Banting and Best Department of Medical Research, University of Toronto, 816-160 College Street, Toronto, Ontario M5S 3E1, Canada
| | - Priya Luthra
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, 100 Piedmont Avenue, Atlanta, Georgia 30303, United States
| | - Liuqing Shi
- Department of Chemistry, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, United States
| | - Dominika Borek
- Department of Biophysics, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390, United States
| | - Alevtina Pavlenco
- Donnelly Centre for Cellular and Biomolecular Research, Banting and Best Department of Medical Research, University of Toronto, 816-160 College Street, Toronto, Ontario M5S 3E1, Canada
| | - Henry Rohrs
- Department of Chemistry, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, United States
| | - Christopher F. Basler
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, 100 Piedmont Avenue, Atlanta, Georgia 30303, United States
| | - Sachdev S. Sidhu
- Donnelly Centre for Cellular and Biomolecular Research, Banting and Best Department of Medical Research, University of Toronto, 816-160 College Street, Toronto, Ontario M5S 3E1, Canada
| | - Michael L. Gross
- Department of Chemistry, Washington University in St. Louis, 1 Brookings Drive, St. Louis, Missouri 63130, United States
| | - Daisy W. Leung
- Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, United States
- Department of Pathology and Immunology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, United States
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Wong HH, Fung TS, Fang S, Huang M, Le MT, Liu DX. Accessory proteins 8b and 8ab of severe acute respiratory syndrome coronavirus suppress the interferon signaling pathway by mediating ubiquitin-dependent rapid degradation of interferon regulatory factor 3. Virology 2017; 515:165-175. [PMID: 29294448 PMCID: PMC7112132 DOI: 10.1016/j.virol.2017.12.028] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 12/22/2017] [Accepted: 12/25/2017] [Indexed: 12/28/2022]
Abstract
Severe acute respiratory syndrome coronavirus (SARS-CoV) is an inefficient inducer of interferon (IFN) response. It expresses various proteins that effectively circumvent IFN production at different levels via distinct mechanisms. Through the construction of recombinant IBV expressing proteins 8a, 8b and 8ab encoded by SARS-CoV ORF8, we demonstrate that expression of 8b and 8ab enables the corresponding recombinant viruses to partially overcome the inhibitory actions of IFN activation to achieve higher replication efficiencies in cells. We also found that proteins 8b and 8ab could physically interact with IRF3. Overexpression of 8b and 8ab resulted in the reduction of poly (I:C)-induced IRF3 dimerization and inhibition of the IFN-β signaling pathway. This counteracting effect was partially mediated by protein 8b/8ab-induced degradation of IRF3 in a ubiquitin-proteasome-dependent manner. Taken together, we propose that SARS-CoV may exploit the unique functions of proteins 8b and 8ab as novel mechanisms to overcome the effect of IFN response during virus infection. Recombinant IBV expressing SARS-CoV protein 8b or 8ab replicates better than wild type in cells pre-treated with poly(I:C). 8b interacts with the IAD domain of IRF3. Overexpression of 8b or 8ab reduces poly(I:C)-induced IRF3 dimerization and interferon induction. 8b and 8ab induce degradation of IRF3 in a ubiquitin-proteasome-dependent manner. 8b and 8ab suppress interferon response induced by constitutively active IRF3.
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Affiliation(s)
- Hui Hui Wong
- South China Agricultural University, Guangdong Province Key Laboratory Microbial Signals & Disease Co, and Integrative Microbiology Research Centre, Guangzhou 510642, Guangdong, People's Republic of China; Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore
| | - To Sing Fung
- South China Agricultural University, Guangdong Province Key Laboratory Microbial Signals & Disease Co, and Integrative Microbiology Research Centre, Guangzhou 510642, Guangdong, People's Republic of China
| | - Shouguo Fang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore; Agricultural School, Yangtze University, 266 Jingmilu, Jingzhou City, Hubei Province 434025, China
| | - Mei Huang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore
| | - My Tra Le
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore
| | - Ding Xiang Liu
- South China Agricultural University, Guangdong Province Key Laboratory Microbial Signals & Disease Co, and Integrative Microbiology Research Centre, Guangzhou 510642, Guangdong, People's Republic of China; School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore.
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Abstract
In this review, we describe the identification of the PRRs involved in the recognition of pestiviruses, and the mechanisms of these viruses to prevent the activation of host’s innate immune response with special emphasis on viral RNases. Most importantly, we extend these data and present our model of innate immunotolerance requiring continuous prevention of detection of immunostimulatory self nucleic acids, in contrast to the well-known long-term tolerance of the adaptive immune system targeted predominantly against proteins. This hypothesis is very likely relevant beyond the bovine species and might answer more fundamental questions on the discrimination between “self” and “viral nonself RNA”, which are relevant also for the prevention and treatment of chronic IFN induction and autoimmunity induced by “self-RNAs”.
Pestiviruses including bovine viral diarrhea virus (BVDV), border disease virus (BDV) and classical swine fever virus (CSFV), occur worldwide and are important pathogens of livestock. A large part of their success can be attributed to the induction of central immunotolerance including B- and T-cells upon fetal infection leading to the generation of persistently infected (PI) animals. In the past few years, it became evident that evasion of innate immunity is a central element to induce and maintain persistent infection. Hence, the viral non-structural protease Npro heads the transcription factor IRF-3 for proteasomal degradation, whereas an extracellularly secreted, soluble form of the envelope glycoprotein Erns degrades immunostimulatory viral single- and double-stranded RNA, which makes this RNase unique among viral endoribonucleases. We propose that these pestiviral interferon (IFN) antagonists maintain a state of innate immunotolerance mainly pertaining its viral nucleic acids, in contrast to the well-established immunotolerance of the adaptive immune system, which is mainly targeted at proteins. In particular, the unique extension of ‘self’ to include the viral genome by degrading immunostimulatory viral RNA by Erns is reminiscent of various host nucleases that are important to prevent inappropriate IFN activation by the host’s own nucleic acids in autoimmune diseases such as Aicardi-Goutières syndrome or systemic lupus erythematosus. This mechanism of “innate tolerance” might thus provide a new facet to the role of extracellular RNases in the sustained prevention of the body’s own immunostimulatory RNA to act as a danger-associated molecular pattern that is relevant across various species.
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Affiliation(s)
- Carmela Lussi
- Institute of Virology and Immunology, Federal Food Safety and Veterinary Office (FSVO) and Vetsuisse Faculty University of Bern, Laenggass-Str. 122, CH-3001 Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.
| | - Matthias Schweizer
- Institute of Virology and Immunology, Federal Food Safety and Veterinary Office (FSVO) and Vetsuisse Faculty University of Bern, Laenggass-Str. 122, CH-3001 Bern, Switzerland.
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Abstract
Pestiviruses cause economically important diseases among domestic ruminants and pigs, but they may also infect a wide spectrum of wild species of even-toed ungulates (Artiodactyla). Bovine viral diarrhea virus (BVDV) and Border disease virus of sheep infect their hosts either transiently or persistently. Cellular and humoral immunotolerance to the infecting strain is a unique feature of persistent infection (PI) by ruminant pestiviruses. Persistence, caused by transplacental infection early in fetal development, depends on virally encoded interferon antagonists that inactivate the host's innate immune response to the virus without globally interfering with its function against other viruses. At epidemiological equilibrium, approximately 1-2% of animals are PI. Successful BVDV control programs show that removal of PI animals results in viral extinction in the host population. The nucleotide sequences of ruminant pestiviruses change little during persistent infection. Nevertheless, they display large heterogeneity, pointing to a long history of virus-host coevolution in which avirulent strains are more successful.
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Affiliation(s)
- Matthias Schweizer
- Institute of Veterinary Virology, University of Bern, CH-3001 Bern, Switzerland; ,
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Abstract
The Filoviridae family of viruses, which includes the genera Ebolavirus (EBOV) and Marburgvirus (MARV), causes severe and often times lethal hemorrhagic fever in humans. Filoviral infections are associated with ineffective innate antiviral responses as a result of virally encoded immune antagonists, which render the host incapable of mounting effective innate or adaptive immune responses. The Type I interferon (IFN) response is critical for establishing an antiviral state in the host cell and subsequent activation of the adaptive immune responses. Several filoviral encoded components target Type I IFN responses, and this innate immune suppression is important for viral replication and pathogenesis. For example, EBOV VP35 inhibits the phosphorylation of IRF-3/7 by the TBK-1/IKKε kinases in addition to sequestering viral RNA from detection by RIG-I like receptors. MARV VP40 inhibits STAT1/2 phosphorylation by inhibiting the JAK family kinases. EBOV VP24 inhibits nuclear translocation of activated STAT1 by karyopherin-α. The examples also represent distinct mechanisms utilized by filoviral proteins in order to counter immune responses, which results in limited IFN-α/β production and downstream signaling.
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Affiliation(s)
- Parameshwaran Ramanan
- Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
- Biochemistry Graduate Program, Iowa State University, Ames, IA 50011, USA
| | - Reed S. Shabman
- Department of Microbiology, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Craig S. Brown
- Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
- Biochemistry Undergraduate Program, Iowa State University, Ames, IA 50011, USA
| | - Gaya K. Amarasinghe
- Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
- Authors to whom correspondence should be addressed; (G.K.A); (C.F.B); (D.W.L.)
| | - Christopher F. Basler
- Department of Microbiology, Mount Sinai School of Medicine, New York, NY 10029, USA
- Authors to whom correspondence should be addressed; (G.K.A); (C.F.B); (D.W.L.)
| | - Daisy W. Leung
- Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
- Authors to whom correspondence should be addressed; (G.K.A); (C.F.B); (D.W.L.)
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