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Zhang X, Zhang Y, Wei F. Research progress on the nonstructural protein 1 (NS1) of influenza a virus. Virulence 2024; 15:2359470. [PMID: 38918890 PMCID: PMC11210920 DOI: 10.1080/21505594.2024.2359470] [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: 01/25/2024] [Accepted: 05/19/2024] [Indexed: 06/27/2024] Open
Abstract
Influenza A virus (IAV) is the leading cause of highly contagious respiratory infections, which poses a serious threat to public health. The non-structural protein 1 (NS1) is encoded by segment 8 of IAV genome and is expressed in high levels in host cells upon IAV infection. It is the determinant of virulence and has multiple functions by targeting type Ι interferon (IFN-I) and type III interferon (IFN-III) production, disrupting cell apoptosis and autophagy in IAV-infected cells, and regulating the host fitness of influenza viruses. This review will summarize the current research on the NS1 including the structure and related biological functions of the NS1 as well as the interaction between the NS1 and host cells. It is hoped that this will provide some scientific basis for the prevention and control of the influenza virus.
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Affiliation(s)
- Xiaoyan Zhang
- College of Animal Science and Technology, Ningxia University, Yinchuan, China
| | - Yuying Zhang
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Fanhua Wei
- College of Animal Science and Technology, Ningxia University, Yinchuan, China
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2
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Khalil AM, Nogales A, Martínez-Sobrido L, Mostafa A. Antiviral responses versus virus-induced cellular shutoff: a game of thrones between influenza A virus NS1 and SARS-CoV-2 Nsp1. Front Cell Infect Microbiol 2024; 14:1357866. [PMID: 38375361 PMCID: PMC10875036 DOI: 10.3389/fcimb.2024.1357866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 01/16/2024] [Indexed: 02/21/2024] Open
Abstract
Following virus recognition of host cell receptors and viral particle/genome internalization, viruses replicate in the host via hijacking essential host cell machinery components to evade the provoked antiviral innate immunity against the invading pathogen. Respiratory viral infections are usually acute with the ability to activate pattern recognition receptors (PRRs) in/on host cells, resulting in the production and release of interferons (IFNs), proinflammatory cytokines, chemokines, and IFN-stimulated genes (ISGs) to reduce virus fitness and mitigate infection. Nevertheless, the game between viruses and the host is a complicated and dynamic process, in which they restrict each other via specific factors to maintain their own advantages and win this game. The primary role of the non-structural protein 1 (NS1 and Nsp1) of influenza A viruses (IAV) and the pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respectively, is to control antiviral host-induced innate immune responses. This review provides a comprehensive overview of the genesis, spatial structure, viral and cellular interactors, and the mechanisms underlying the unique biological functions of IAV NS1 and SARS-CoV-2 Nsp1 in infected host cells. We also highlight the role of both non-structural proteins in modulating viral replication and pathogenicity. Eventually, and because of their important role during viral infection, we also describe their promising potential as targets for antiviral therapy and the development of live attenuated vaccines (LAV). Conclusively, both IAV NS1 and SARS-CoV-2 Nsp1 play an important role in virus-host interactions, viral replication, and pathogenesis, and pave the way to develop novel prophylactic and/or therapeutic interventions for the treatment of these important human respiratory viral pathogens.
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Affiliation(s)
- Ahmed Magdy Khalil
- Disease Intervention & Prevention and Host Pathogen Interactions Programs, Texas Biomedical Research Institute, San Antonio, TX, United States
- Department of Zoonotic Diseases, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt
| | - Aitor Nogales
- Center for Animal Health Research, CISA-INIA-CSIC, Madrid, Spain
| | - Luis Martínez-Sobrido
- Disease Intervention & Prevention and Host Pathogen Interactions Programs, Texas Biomedical Research Institute, San Antonio, TX, United States
| | - Ahmed Mostafa
- Disease Intervention & Prevention and Host Pathogen Interactions Programs, Texas Biomedical Research Institute, San Antonio, TX, United States
- Center of Scientific Excellence for Influenza Viruses, National Research Centre, Giza, Egypt
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3
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López-Valiñas Á, Valle M, Wang M, Darji A, Cantero G, Chiapponi C, Segalés J, Ganges L, Núñez JI. Vaccination against swine influenza in pigs causes different drift evolutionary patterns upon swine influenza virus experimental infection and reduces the likelihood of genomic reassortments. Front Cell Infect Microbiol 2023; 13:1111143. [PMID: 36992684 PMCID: PMC10040791 DOI: 10.3389/fcimb.2023.1111143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 02/14/2023] [Indexed: 03/16/2023] Open
Abstract
Influenza A viruses (IAVs) can infect a wide variety of bird and mammal species. Their genome is characterized by 8 RNA single stranded segments. The low proofreading activity of their polymerases and the genomic reassortment between different IAVs subtypes allow them to continuously evolve, constituting a constant threat to human and animal health. In 2009, a pandemic of an IAV highlighted the importance of the swine host in IAVs adaptation between humans and birds. The swine population and the incidence of swine IAV is constantly growing. In previous studies, despite vaccination, swine IAV growth and evolution were proven in vaccinated and challenged animals. However, how vaccination can drive the evolutionary dynamics of swine IAV after coinfection with two subtypes is poorly studied. In the present study, vaccinated and nonvaccinated pigs were challenged by direct contact with H1N1 and H3N2 independent swine IAVs seeder pigs. Nasal swab samples were daily recovered and broncho-alveolar lavage fluid (BALF) was also collected at necropsy day from each pig for swine IAV detection and whole genome sequencing. In total, 39 swine IAV whole genome sequences were obtained by next generation sequencing from samples collected from both experimental groups. Subsequently, genomic, and evolutionary analyses were carried out to detect both, genomic reassortments and single nucleotide variants (SNV). Regarding the segments found per sample, the simultaneous presence of segments from both subtypes was much lower in vaccinated animals, indicating that the vaccine reduced the likelihood of genomic reassortment events. In relation to swine IAV intra-host diversity, a total of 239 and 74 SNV were detected within H1N1 and H3N2 subtypes, respectively. Different proportions of synonymous and nonsynonymous substitutions were found, indicating that vaccine may be influencing the main mechanism that shape swine IAV evolution, detecting natural, neutral, and purifying selection in the different analyzed scenarios. SNV were detected along the whole swine IAV genome with important nonsynonymous substitutions on polymerases, surface glycoproteins and nonstructural proteins, which may have an impact on virus replication, immune system escaping and virulence of virus, respectively. The present study further emphasized the vast evolutionary capacity of swine IAV, under natural infection and vaccination pressure scenarios.
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Affiliation(s)
- Álvaro López-Valiñas
- IRTA, Programa de Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- Unitat mixta d’Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- WOAH Collaborating Centre for the Research and Control of Emerging and Re-Emerging Swine Diseases in Europe (IRTA-CReSA), Barcelona, Spain
- *Correspondence: José I. Núñez, ; Álvaro López-Valiñas,
| | - Marta Valle
- IRTA, Programa de Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- Unitat mixta d’Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- WOAH Collaborating Centre for the Research and Control of Emerging and Re-Emerging Swine Diseases in Europe (IRTA-CReSA), Barcelona, Spain
| | - Miaomiao Wang
- IRTA, Programa de Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- Unitat mixta d’Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- WOAH Collaborating Centre for the Research and Control of Emerging and Re-Emerging Swine Diseases in Europe (IRTA-CReSA), Barcelona, Spain
| | - Ayub Darji
- IRTA, Programa de Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- Unitat mixta d’Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- WOAH Collaborating Centre for the Research and Control of Emerging and Re-Emerging Swine Diseases in Europe (IRTA-CReSA), Barcelona, Spain
| | - Guillermo Cantero
- IRTA, Programa de Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- Unitat mixta d’Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- WOAH Collaborating Centre for the Research and Control of Emerging and Re-Emerging Swine Diseases in Europe (IRTA-CReSA), Barcelona, Spain
| | - Chiara Chiapponi
- WOAH Reference Laboratory for Swine Influenza, Istituto Zooprofilattico Sperimentale della Lombardia ed Emilia-Romagna, Brescia, Italy
| | - Joaquim Segalés
- Unitat mixta d’Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- WOAH Collaborating Centre for the Research and Control of Emerging and Re-Emerging Swine Diseases in Europe (IRTA-CReSA), Barcelona, Spain
- Departament de Sanitat i Anatomia Animals, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Llilianne Ganges
- IRTA, Programa de Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- Unitat mixta d’Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- WOAH Collaborating Centre for the Research and Control of Emerging and Re-Emerging Swine Diseases in Europe (IRTA-CReSA), Barcelona, Spain
- WOAH Reference Laboratory for Classical Swine Fever, IRTA-CReSA, Barcelona, Spain
| | - José I. Núñez
- IRTA, Programa de Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- Unitat mixta d’Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
- WOAH Collaborating Centre for the Research and Control of Emerging and Re-Emerging Swine Diseases in Europe (IRTA-CReSA), Barcelona, Spain
- *Correspondence: José I. Núñez, ; Álvaro López-Valiñas,
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Detection and Characterization of an H9N2 Influenza A Virus in the Egyptian Rousette Bat in Limpopo, South Africa. Viruses 2023; 15:v15020498. [PMID: 36851712 PMCID: PMC9958621 DOI: 10.3390/v15020498] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 02/06/2023] [Accepted: 02/08/2023] [Indexed: 02/15/2023] Open
Abstract
In recent years, bats have been shown to host various novel bat-specific influenza viruses, including H17N10 and H18N11 in the Americas and the H9N2 subtype from Africa. Rousettus aegyptiacus (Egyptian Rousette bat) is recognized as a host species for diverse viral agents. This study focused on the molecular surveillance of a maternal colony in Limpopo, South Africa, between 2017-2018. A pan-influenza hemi-nested RT-PCR assay targeting the PB1 gene was established, and influenza A virus RNA was identified from one fecal sample out of 860 samples. Genome segments were recovered using segment-specific amplification combined with standard Sanger sequencing and Illumina unbiased sequencing. The identified influenza A virus was closely related to the H9N2 bat-influenza virus, confirming the circulation of this subtype among Egyptian fruit bat populations in Southern Africa. This bat H9N2 subtype contained amino acid residues associated with transmission and virulence in either mammalian or avian hosts, though it will likely require additional adaptations before spillover.
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NS2 is a key determinant of compatibility in reassortant avian influenza virus with heterologous H7N9-derived NS segment. Virus Res 2023; 324:199028. [PMID: 36572153 DOI: 10.1016/j.virusres.2022.199028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 11/30/2022] [Accepted: 12/18/2022] [Indexed: 12/24/2022]
Abstract
Influenza A viruses are common pathogens with high prevalence worldwide and potential for pandemic spread. While influenza A infections typically elicit robust cellular innate immune responses, the non-structural protein 1 (NS1) antagonizes host anti-viral responses and is critical for efficient virus replication and virulence. The avian influenza virus (AIV) H7N9 initially emerged in China in 2013 and has since crossed the avian-human barrier, causing severe disease in humans. To investigate the influence of the H7N9 NS gene (NS079) on viral replication and innate immune response, we generated several recombinant AIVs bearing various NS079 segments on the backbone of H6N1 (strain 0702). Intriguingly, the recombinant virus bearing the heterologous NS079 gene was highly attenuated compared with virus carrying the homologous NS gene (NS0702). Furthermore, we generated a NS079-0702R virus that expresses a chimeric NS gene in which part of the NS079 effector domain was replaced with the sequence from NS0702. The NS079-0702R virus exhibited significantly enhanced viral yield, approximately 100-fold more than virus bearing NS079. The high infection rate of NS079-0702R virus was reflected by strong induction of IFN and Mx expression in human A549 cells. Intriguingly, our in vitro comparative analysis suggested that the increased NS079-0702R infection capacity was independent of the ability of NS1 to interact with cellular partners, such as PKR and CPSF30. Since partial substitution of the effector domain from NS0702 altered the coding sequence of NS2, we further generated another recombinant virus with NS2 derived from H7N9. Surprisingly, the virus with H7N9-derived NS2 exhibited growth characteristics similar to NS079. Our data demonstrate that swapping NS2 components changes infection efficiency, suggesting a key role for NS2 as a determinant of viral compatibility upon reassortment. These findings warrant further investigation into the precise mechanisms by which NS2 contributes to viral replication and host immunity.1.
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Nogales A, DeDiego ML, Martínez-Sobrido L. Live attenuated influenza A virus vaccines with modified NS1 proteins for veterinary use. Front Cell Infect Microbiol 2022; 12:954811. [PMID: 35937688 PMCID: PMC9354547 DOI: 10.3389/fcimb.2022.954811] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 06/24/2022] [Indexed: 11/17/2022] Open
Abstract
Influenza A viruses (IAV) spread rapidly and can infect a broad range of avian or mammalian species, having a tremendous impact in human and animal health and the global economy. IAV have evolved to develop efficient mechanisms to counteract innate immune responses, the first host mechanism that restricts IAV infection and replication. One key player in this fight against host-induced innate immune responses is the IAV non-structural 1 (NS1) protein that modulates antiviral responses and virus pathogenicity during infection. In the last decades, the implementation of reverse genetics approaches has allowed to modify the viral genome to design recombinant IAV, providing researchers a powerful platform to develop effective vaccine strategies. Among them, different levels of truncation or deletion of the NS1 protein of multiple IAV strains has resulted in attenuated viruses able to induce robust innate and adaptive immune responses, and high levels of protection against wild-type (WT) forms of IAV in multiple animal species and humans. Moreover, this strategy allows the development of novel assays to distinguish between vaccinated and/or infected animals, also known as Differentiating Infected from Vaccinated Animals (DIVA) strategy. In this review, we briefly discuss the potential of NS1 deficient or truncated IAV as safe, immunogenic and protective live-attenuated influenza vaccines (LAIV) to prevent disease caused by this important animal and human pathogen.
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Affiliation(s)
- Aitor Nogales
- Centro de Investigación en Sanidad Animal (CISA), Centro Nacional Instituto de Investigación y Tecnología Agraria y Alimentaria (INIA, CSIC), Madrid, Spain
- *Correspondence: Aitor Nogales, ; Luis Martínez-Sobrido,
| | - Marta L. DeDiego
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, Madrid, Spain
| | - Luis Martínez-Sobrido
- Department of Disease Intervention and Prevetion, Texas Biomedical Research Institute, San Antonio, TX, United States
- *Correspondence: Aitor Nogales, ; Luis Martínez-Sobrido,
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How Influenza A Virus NS1 Deals with the Ubiquitin System to Evade Innate Immunity. Viruses 2021; 13:v13112309. [PMID: 34835115 PMCID: PMC8619935 DOI: 10.3390/v13112309] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 11/14/2021] [Accepted: 11/18/2021] [Indexed: 12/11/2022] Open
Abstract
Ubiquitination is a post-translational modification regulating critical cellular processes such as protein degradation, trafficking and signaling pathways, including activation of the innate immune response. Therefore, viruses, and particularly influenza A virus (IAV), have evolved different mechanisms to counteract this system to perform proper infection. Among IAV proteins, the non-structural protein NS1 is shown to be one of the main virulence factors involved in these viral hijackings. NS1 is notably able to inhibit the host's antiviral response through the perturbation of ubiquitination in different ways, as discussed in this review.
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Identification and Characterization of Swine Influenza Virus H1N1 Variants Generated in Vaccinated and Nonvaccinated, Challenged Pigs. Viruses 2021; 13:v13102087. [PMID: 34696517 PMCID: PMC8539973 DOI: 10.3390/v13102087] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/08/2021] [Accepted: 10/13/2021] [Indexed: 01/22/2023] Open
Abstract
Influenza viruses represent a continuous threat to both animal and human health. The 2009 H1N1 A influenza pandemic highlighted the importance of a swine host in the adaptation of influenza viruses to humans. Nowadays, one of the most extended strategies used to control swine influenza viruses (SIVs) is the trivalent vaccine application, whose formulation contains the most frequently circulating SIV subtypes H1N1, H1N2, and H3N2. These vaccines do not provide full protection against the virus, allowing its replication, evolution, and adaptation. To better understand the main mechanisms that shape viral evolution, here, the SIV intra-host diversity was analyzed in samples collected from both vaccinated and nonvaccinated animals challenged with the H1N1 influenza A virus. Twenty-eight whole SIV genomes were obtained by next-generation sequencing, and differences in nucleotide variants between groups were established. Substitutions were allocated along all influenza genetic segments, while the most relevant nonsynonymous substitutions were allocated in the NS1 protein on samples collected from vaccinated animals, suggesting that SIV is continuously evolving despite vaccine application. Moreover, new viral variants were found in both vaccinated and nonvaccinated pigs, showing relevant substitutions in the HA, NA, and NP proteins, which may increase viral fitness under field conditions.
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Tseng YY, Kuan CY, Mibayashi M, Chen CJ, Palese P, Albrecht RA, Hsu WL. Interaction between NS1 and Cellular MAVS Contributes to NS1 Mitochondria Targeting. Viruses 2021; 13:1909. [PMID: 34696339 PMCID: PMC8537625 DOI: 10.3390/v13101909] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/16/2021] [Accepted: 09/17/2021] [Indexed: 11/16/2022] Open
Abstract
Influenza A virus nonstructural protein 1 (NS1) plays an important role in evading host innate immunity. NS1 inhibits interferon (IFN) responses via multiple mechanisms, including sequestering dsRNA and suppressing retinoic acid-inducible gene I (RIG-I) signaling by interacting with RIG-I and tripartite motif-containing protein 25 (TRIM25). In the current study, we demonstrated the mitochondrial localization of NS1 at the early stage of influenza virus infection. Since NS1 does not contain mitochondria-targeting signals, we suspected that there is an association between the NS1 and mitochondrial proteins. This hypothesis was tested by demonstrating the interaction of NS1 with mitochondrial antiviral-signaling protein (MAVS) in a RIG-I-independent manner. Importantly, the association with MAVS facilitated the mitochondrial localization of NS1 and thereby significantly impeded MAVS-mediated Type I IFN production.
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Affiliation(s)
- Yeu-Yang Tseng
- Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung 402, Taiwan; (Y.-Y.T.); (C.-Y.K.)
- WHO Collaborating Centre for Reference and Research on Influenza, Royal Melbourne Hospital, Peter Doherty Institute for Infection and Immunity, Melbourne, VIC 3000, Australia
- Department of Infectious Diseases, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC 3000, Australia
| | - Chih-Ying Kuan
- Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung 402, Taiwan; (Y.-Y.T.); (C.-Y.K.)
| | - Masaki Mibayashi
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; (M.M.); (C.-J.C.); (P.P.); (R.A.A.)
| | - Chi-Jene Chen
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; (M.M.); (C.-J.C.); (P.P.); (R.A.A.)
| | - Peter Palese
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; (M.M.); (C.-J.C.); (P.P.); (R.A.A.)
- Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Randy A. Albrecht
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; (M.M.); (C.-J.C.); (P.P.); (R.A.A.)
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Wei-Li Hsu
- Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung 402, Taiwan; (Y.-Y.T.); (C.-Y.K.)
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Plotnikova M, Lozhkov A, Romanovskaya-Romanko E, Baranovskaya I, Sergeeva M, Kаа K, Klotchenko S, Vasin A. IFN-λ1 Displays Various Levels of Antiviral Activity In Vitro in a Select Panel of RNA Viruses. Viruses 2021; 13:1602. [PMID: 34452467 PMCID: PMC8402797 DOI: 10.3390/v13081602] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/05/2021] [Accepted: 08/06/2021] [Indexed: 12/25/2022] Open
Abstract
Type III interferons (lambda IFNs) are a quite new, small family of three closely related cytokines with interferon-like activity. Attention to IFN-λ is mainly focused on direct antiviral activity in which, as with IFN-α, viral genome replication is inhibited without the participation of immune system cells. The heterodimeric receptor for lambda interferons is exposed mainly on epithelial cells, which limits its possible action on other cells, thus reducing the likelihood of developing undesirable side effects compared to type I IFN. In this study, we examined the antiviral potential of exogenous human IFN-λ1 in cellular models of viral infection. To study the protective effects of IFN-λ1, three administration schemes were used: 'preventive' (pretreatment); 'preventive/therapeutic' (pre/post); and 'therapeutic' (post). Three IFN-λ1 concentrations (from 10 to 500 ng/mL) were used. We have shown that human IFN-λ1 restricts SARS-CoV-2 replication in Vero cells with all three treatment schemes. In addition, we have shown a decrease in the viral loads of CHIKV and IVA with the 'preventive' and 'preventive/therapeutic' regimes. No significant antiviral effect of IFN-λ1 against AdV was detected. Our study highlights the potential for using IFN-λ as a broad-spectrum therapeutic agent against respiratory RNA viruses.
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Affiliation(s)
- Marina Plotnikova
- Smorodintsev Research Institute of Influenza, Russian Ministry of Health, 197376 St. Petersburg, Russia; (M.P.); (A.L.); (E.R.-R.); (I.B.); (M.S.); (A.V.)
| | - Alexey Lozhkov
- Smorodintsev Research Institute of Influenza, Russian Ministry of Health, 197376 St. Petersburg, Russia; (M.P.); (A.L.); (E.R.-R.); (I.B.); (M.S.); (A.V.)
- Institute of Biomedical Systems and Biotechnologies, Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia
| | - Ekaterina Romanovskaya-Romanko
- Smorodintsev Research Institute of Influenza, Russian Ministry of Health, 197376 St. Petersburg, Russia; (M.P.); (A.L.); (E.R.-R.); (I.B.); (M.S.); (A.V.)
| | - Irina Baranovskaya
- Smorodintsev Research Institute of Influenza, Russian Ministry of Health, 197376 St. Petersburg, Russia; (M.P.); (A.L.); (E.R.-R.); (I.B.); (M.S.); (A.V.)
- Institute of Biomedical Systems and Biotechnologies, Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia
| | - Mariia Sergeeva
- Smorodintsev Research Institute of Influenza, Russian Ministry of Health, 197376 St. Petersburg, Russia; (M.P.); (A.L.); (E.R.-R.); (I.B.); (M.S.); (A.V.)
- Institute of Biomedical Systems and Biotechnologies, Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia
| | - Konstantin Kаа
- Chumakov Federal Scientific Center for Research and Development of Immune-and-Biological Products RAS, 108819 Moscow, Russia;
| | - Sergey Klotchenko
- Smorodintsev Research Institute of Influenza, Russian Ministry of Health, 197376 St. Petersburg, Russia; (M.P.); (A.L.); (E.R.-R.); (I.B.); (M.S.); (A.V.)
| | - Andrey Vasin
- Smorodintsev Research Institute of Influenza, Russian Ministry of Health, 197376 St. Petersburg, Russia; (M.P.); (A.L.); (E.R.-R.); (I.B.); (M.S.); (A.V.)
- Institute of Biomedical Systems and Biotechnologies, Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia
- Scientific and Educational Center for Biophysical Research in The Field of Pharmaceuticals, Saint Petersburg State Chemical Pharmaceutical University, 197022 St. Petersburg, Russia
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Ji ZX, Wang XQ, Liu XF. NS1: A Key Protein in the "Game" Between Influenza A Virus and Host in Innate Immunity. Front Cell Infect Microbiol 2021; 11:670177. [PMID: 34327148 PMCID: PMC8315046 DOI: 10.3389/fcimb.2021.670177] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Accepted: 06/25/2021] [Indexed: 12/24/2022] Open
Abstract
Since the influenza pandemic occurred in 1918, people have recognized the perniciousness of this virus. It can cause mild to severe infections in animals and humans worldwide, with extremely high morbidity and mortality. Since the first day of human discovery of it, the “game” between the influenza virus and the host has never stopped. NS1 protein is the key protein of the influenza virus against host innate immunity. The interaction between viruses and organisms is a complex and dynamic process, in which they restrict each other, but retain their own advantages. In this review, we start by introducing the structure and biological characteristics of NS1, and then investigate the factors that affect pathogenicity of influenza which determined by NS1. In order to uncover the importance of NS1, we analyze the interaction of NS1 protein with interferon system in innate immunity and the molecular mechanism of host antagonism to NS1 protein, highlight the unique biological function of NS1 protein in cell cycle.
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Affiliation(s)
- Zhu-Xing Ji
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Xiao-Quan Wang
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China.,Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China.,Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Xiu-Fan Liu
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, China.,Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China.,Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
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12
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Structure and Activities of the NS1 Influenza Protein and Progress in the Development of Small-Molecule Drugs. Int J Mol Sci 2021; 22:ijms22084242. [PMID: 33921888 PMCID: PMC8074201 DOI: 10.3390/ijms22084242] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 04/18/2021] [Accepted: 04/18/2021] [Indexed: 11/30/2022] Open
Abstract
The influenza virus causes human disease on a global scale and significant morbidity and mortality. The existing vaccination regime remains vulnerable to antigenic drift, and more seriously, a small number of viral mutations could lead to drug resistance. Therefore, the development of a new additional therapeutic small molecule-based anti-influenza virus is urgently required. The NS1 influenza gene plays a pivotal role in the suppression of host antiviral responses, especially by inhibiting interferon (IFN) production and the activities of antiviral proteins, such as dsRNA-dependent serine/threonine-protein kinase R (PKR) and 2′-5′-oligoadenylate synthetase (OAS)/RNase L. NS1 also modulates important aspects of viral RNA replication, viral protein synthesis, and virus replication cycle. Taken together, small molecules that target NS1 are believed to offer a means of developing new anti-influenza drugs.
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13
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Wang X, Lin L, Yu Y, Yan Y, Ojha NK, Zhou J. The N-terminal residual arginine 19 of influenza A virus NS1 protein is required for its nuclear localization and RNA binding. Vet Microbiol 2020; 251:108895. [PMID: 33126184 DOI: 10.1016/j.vetmic.2020.108895] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Accepted: 10/11/2020] [Indexed: 11/30/2022]
Abstract
RNA binding ability and cellular distribution are important for nonstructural protein 1 (NS1) of influenza A virus to act as a viral regulatory factor to control virus life cycle. In this study, we identified that the N-terminal residues 19-21 of NS1 are a highly conserved motif depending on all the available NS1 full length sequence of H5N1 influenza A virus from NCBI database. Site-directed mutation analysis demonstrated that the R19 residue of NS1 is critical for its RNA binding and nuclear localization. Furthermore, the residue R19 of NS1 was identified to be critical for regulating M1 mRNA splicing and NS1 nuclear export. Biological analysis of the rescued viruses indicated that the R19A mutation of NS1 did not interfere the replication of H5N1 virus during infection and attenuated the virulence of H5N1 virus in mice.
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Affiliation(s)
- Xingbo Wang
- MOA Key Laboratory of Animal Virology, Center for Veterinary Sciences, Zhejiang University, Hangzhou, 310058, PR China
| | - Lulu Lin
- MOA Key Laboratory of Animal Virology, Center for Veterinary Sciences, Zhejiang University, Hangzhou, 310058, PR China
| | - Yang Yu
- MOA Key Laboratory of Animal Virology, Center for Veterinary Sciences, Zhejiang University, Hangzhou, 310058, PR China
| | - Yan Yan
- MOA Key Laboratory of Animal Virology, Center for Veterinary Sciences, Zhejiang University, Hangzhou, 310058, PR China
| | - Nishant Kumar Ojha
- MOA Key Laboratory of Animal Virology, Center for Veterinary Sciences, Zhejiang University, Hangzhou, 310058, PR China
| | - Jiyong Zhou
- MOA Key Laboratory of Animal Virology, Center for Veterinary Sciences, Zhejiang University, Hangzhou, 310058, PR China; State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, Zhejiang University, Hangzhou, 310003, PR China.
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14
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Baumhardt JM, Walker JS, Lee Y, Shakya B, Brautigam CA, Lapalombella R, Grishin N, Chook YM. Recognition of nuclear export signals by CRM1 carrying the oncogenic E571K mutation. Mol Biol Cell 2020; 31:1879-1891. [PMID: 32520643 PMCID: PMC7525811 DOI: 10.1091/mbc.e20-04-0233] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 05/26/2020] [Accepted: 06/04/2020] [Indexed: 12/28/2022] Open
Abstract
The E571K mutation of CRM1 is highly prevalent in some cancers, but its mechanism of tumorigenesis is unclear. Glu571 of CRM1 is located in its nuclear export signal (NES)-binding groove, suggesting that binding of select NESs may be altered. We generated HEK 293 cells with either monoallelic CRM1WT/E571K or biallelic CRM1E571K/E571K using CRISPR/Cas9. We also combined analysis of binding affinities and structures of 27 diverse NESs for wild-type and E571K CRM1 with structure-based bioinformatics. While most NESs bind the two CRM1 similarly, NESs from Mek1, eIF4E-transporter, and RPS2 showed >10-fold affinity differences. These NESs have multiple charged side chains binding close to CRM1 position 571, but this feature alone was not sufficient to predict different binding to CRM1(E571K). Consistent with eIF4E-transporter NES binding weaker to CRM1(E571K), eIF4E-transporter was mislocalized in tumor cells carrying CRM1(E571K). This serves as proof of concept that understanding how CRM1(E571K) affects NES binding provides a platform for identifying cargoes that are mislocalized in cancer upon CRM1 mutation. Finally, we showed that large affinity changes seen with some NES peptides (of Mek1 and RPS2) do not always translate to the full-length cargoes, suggesting limitations with current NES prediction methods. Therefore, comprehensive studies like ours are imperative to identify CRM1 cargoes with real pathogenic potential.
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Affiliation(s)
- Jordan M. Baumhardt
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Janek S. Walker
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210
| | - Yoonji Lee
- Departments of Biophysics and Microbiology and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Binita Shakya
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Chad A. Brautigam
- Departments of Biophysics and Microbiology and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Rosa Lapalombella
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210
| | - Nick Grishin
- Departments of Biophysics and Microbiology and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Yuh Min Chook
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390
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15
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Rosário-Ferreira N, Preto AJ, Melo R, Moreira IS, Brito RMM. The Central Role of Non-Structural Protein 1 (NS1) in Influenza Biology and Infection. Int J Mol Sci 2020; 21:E1511. [PMID: 32098424 PMCID: PMC7073157 DOI: 10.3390/ijms21041511] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 01/23/2020] [Accepted: 01/24/2020] [Indexed: 01/07/2023] Open
Abstract
Influenza (flu) is a contagious viral disease, which targets the human respiratory tract and spreads throughout the world each year. Every year, influenza infects around 10% of the world population and between 290,000 and 650,000 people die from it according to the World Health Organization (WHO). Influenza viruses belong to the Orthomyxoviridae family and have a negative sense eight-segment single-stranded RNA genome that encodes 11 different proteins. The only control over influenza seasonal epidemic outbreaks around the world are vaccines, annually updated according to viral strains in circulation, but, because of high rates of mutation and recurrent genetic assortment, new viral strains of influenza are constantly emerging, increasing the likelihood of pandemics. Vaccination effectiveness is limited, calling for new preventive and therapeutic approaches and a better understanding of the virus-host interactions. In particular, grasping the role of influenza non-structural protein 1 (NS1) and related known interactions in the host cell is pivotal to better understand the mechanisms of virus infection and replication, and thus propose more effective antiviral approaches. In this review, we assess the structure of NS1, its dynamics, and multiple functions and interactions, to highlight the central role of this protein in viral biology and its potential use as an effective therapeutic target to tackle seasonal and pandemic influenza.
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Affiliation(s)
- Nícia Rosário-Ferreira
- Coimbra Chemistry Center, Chemistry Department, Faculty of Science and Technology, University of Coimbra, 3004-535 Coimbra, Portugal
- CNC—Center for Neuroscience and Cell Biology. University of Coimbra, UC Biotech Building, 3060-197 Cantanhede, Portugal
| | - António J. Preto
- CNC—Center for Neuroscience and Cell Biology. University of Coimbra, UC Biotech Building, 3060-197 Cantanhede, Portugal
| | - Rita Melo
- CNC—Center for Neuroscience and Cell Biology. University of Coimbra, UC Biotech Building, 3060-197 Cantanhede, Portugal
- Centro de Ciências e Tecnologias Nucleares and Departamento de Engenharia e Ciências Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela LRS, Portugal
| | - Irina S. Moreira
- CNC—Center for Neuroscience and Cell Biology. University of Coimbra, UC Biotech Building, 3060-197 Cantanhede, Portugal
- Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal
| | - Rui M. M. Brito
- Coimbra Chemistry Center, Chemistry Department, Faculty of Science and Technology, University of Coimbra, 3004-535 Coimbra, Portugal
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16
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Quantifying within-host diversity of H5N1 influenza viruses in humans and poultry in Cambodia. PLoS Pathog 2020; 16:e1008191. [PMID: 31951644 PMCID: PMC6992230 DOI: 10.1371/journal.ppat.1008191] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 01/30/2020] [Accepted: 11/04/2019] [Indexed: 12/31/2022] Open
Abstract
Avian influenza viruses (AIVs) periodically cross species barriers and infect humans. The likelihood that an AIV will evolve mammalian transmissibility depends on acquiring and selecting mutations during spillover, but data from natural infection is limited. We analyze deep sequencing data from infected humans and domestic ducks in Cambodia to examine how H5N1 viruses evolve during spillover. Overall, viral populations in both species are predominated by low-frequency (<10%) variation shaped by purifying selection and genetic drift, and half of the variants detected within-host are never detected on the H5N1 virus phylogeny. However, we do detect a subset of mutations linked to human receptor binding and replication (PB2 E627K, HA A150V, and HA Q238L) that arose in multiple, independent humans. PB2 E627K and HA A150V were also enriched along phylogenetic branches leading to human infections, suggesting that they are likely human-adaptive. Our data show that H5N1 viruses generate putative human-adapting mutations during natural spillover infection, many of which are detected at >5% frequency within-host. However, short infection times, genetic drift, and purifying selection likely restrict their ability to evolve extensively during a single infection. Applying evolutionary methods to sequence data, we reveal a detailed view of H5N1 virus adaptive potential, and develop a foundation for studying host-adaptation in other zoonotic viruses. H5N1 avian influenza viruses can cross species barriers and cause severe disease in humans. H5N1 viruses currently cannot replicate and transmit efficiently among humans, but animal infection studies and modeling experiments have suggested that human adaptation may require only a few mutations. However, data from natural spillover infection has been limited, posing a challenge for risk assessment. Here, we analyze a unique dataset of deep sequence data from H5N1 virus-infected humans and domestic ducks in Cambodia. We find that well-known markers of human receptor binding and replication arise in multiple, independent humans. We also find that 3 mutations detected within-host are enriched along phylogenetic branches leading to human infections, suggesting that they are likely human-adapting. However, we also show that within-host evolution in both humans and ducks are shaped heavily by purifying selection and genetic drift, and that a large fraction of within-host variation is never detected on the H5N1 phylogeny. Taken together, our data show that H5N1 viruses do generate human-adapting mutations during natural infection. However, short infection times, purifying selection, and genetic drift may severely limit how much H5N1 viruses can evolve during the course of a single infection.
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17
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Differential Modulation of Innate Immune Responses in Human Primary Cells by Influenza A Viruses Carrying Human or Avian Nonstructural Protein 1. J Virol 2019; 94:JVI.00999-19. [PMID: 31597767 PMCID: PMC6912104 DOI: 10.1128/jvi.00999-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 09/29/2019] [Indexed: 12/22/2022] Open
Abstract
Influenza A viruses (IAVs) cause seasonal epidemics which result in an important health and economic burden. Wild aquatic birds are the natural host of IAV. However, IAV can infect diverse hosts, including humans, domestic poultry, pigs, and others. IAVs circulating in animals occasionally cross the species barrier, infecting humans, which results in mild to very severe disease. In some cases, these viruses can acquire the ability to be transmitted among humans and initiate a pandemic. The nonstructural 1 (NS1) protein of IAV is an important antagonist of the innate immune response. In this study, using recombinant viruses and primary human cells, we show that NS1 proteins from human and avian hosts show intrinsic differences in the modulation of the innate immunity in human dendritic cells and epithelial cells, as well as different cellular localization dynamics in infected cells. The influenza A virus (IAV) nonstructural protein 1 (NS1) contributes to disease pathogenesis through the inhibition of host innate immune responses. Dendritic cells (DCs) release interferons (IFNs) and proinflammatory cytokines and promote adaptive immunity upon viral infection. In order to characterize the strain-specific effects of IAV NS1 on human DC activation, we infected human DCs with a panel of recombinant viruses with the same backbone (A/Puerto Rico/08/1934) expressing different NS1 proteins from human and avian origin. We found that these viruses induced a clearly distinct phenotype in DCs. Specifically, viruses expressing NS1 from human IAV (either H1N1 or H3N2) induced higher levels of expression of type I (IFN-α and IFN-β) and type III (IFN-λ1 to IFNλ3) IFNs than viruses expressing avian IAV NS1 proteins (H5N1, H7N9, and H7N2), but the differences observed in the expression levels of proinflammatory cytokines like tumor necrosis factor alpha (TNF-α) or interleukin-6 (IL-6) were not significant. In addition, using imaging flow cytometry, we found that human and avian NS1 proteins segregate based on their subcellular trafficking dynamics, which might be associated with the different innate immune profile induced in DCs by viruses expressing those NS1 proteins. Innate immune responses induced by our panel of IAV recombinant viruses were also characterized in normal human bronchial epithelial cells, and the results were consistent with those in DCs. Altogether, our results reveal an increased ability of NS1 from avian viruses to antagonize innate immune responses in human primary cells compared to the ability of NS1 from human viruses, which could contribute to the severe disease induced by avian IAV in humans. IMPORTANCE Influenza A viruses (IAVs) cause seasonal epidemics which result in an important health and economic burden. Wild aquatic birds are the natural host of IAV. However, IAV can infect diverse hosts, including humans, domestic poultry, pigs, and others. IAVs circulating in animals occasionally cross the species barrier, infecting humans, which results in mild to very severe disease. In some cases, these viruses can acquire the ability to be transmitted among humans and initiate a pandemic. The nonstructural 1 (NS1) protein of IAV is an important antagonist of the innate immune response. In this study, using recombinant viruses and primary human cells, we show that NS1 proteins from human and avian hosts show intrinsic differences in the modulation of the innate immunity in human dendritic cells and epithelial cells, as well as different cellular localization dynamics in infected cells.
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18
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Nogales A, Martinez-Sobrido L, Topham DJ, DeDiego ML. Modulation of Innate Immune Responses by the Influenza A NS1 and PA-X Proteins. Viruses 2018; 10:v10120708. [PMID: 30545063 PMCID: PMC6315843 DOI: 10.3390/v10120708] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 12/06/2018] [Accepted: 12/08/2018] [Indexed: 12/14/2022] Open
Abstract
Influenza A viruses (IAV) can infect a broad range of animal hosts, including humans. In humans, IAV causes seasonal annual epidemics and occasional pandemics, representing a serious public health and economic problem, which is most effectively prevented through vaccination. The defense mechanisms that the host innate immune system provides restrict IAV replication and infection. Consequently, to successfully replicate in interferon (IFN)-competent systems, IAV has to counteract host antiviral activities, mainly the production of IFN and the activities of IFN-induced host proteins that inhibit virus replication. The IAV multifunctional proteins PA-X and NS1 are virulence factors that modulate the innate immune response and virus pathogenicity. Notably, these two viral proteins have synergistic effects in the inhibition of host protein synthesis in infected cells, although using different mechanisms of action. Moreover, the control of innate immune responses by the IAV NS1 and PA-X proteins is subject to a balance that can determine virus pathogenesis and fitness, and recent evidence shows co-evolution of these proteins in seasonal viruses, indicating that they should be monitored for enhanced virulence. Importantly, inhibition of host gene expression by the influenza NS1 and/or PA-X proteins could be explored to develop improved live-attenuated influenza vaccines (LAIV) by modulating the ability of the virus to counteract antiviral host responses. Likewise, both viral proteins represent a reasonable target for the development of new antivirals for the control of IAV infections. In this review, we summarize the role of IAV NS1 and PA-X in controlling the antiviral response during viral infection.
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Affiliation(s)
- Aitor Nogales
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- Centro de Investigación en Sanidad Animal (CISA)-INIA, Valdeolmos, 28130 Madrid, Spain.
| | - Luis Martinez-Sobrido
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
| | - David J Topham
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- David H. Smith Center for Vaccine Biology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
| | - Marta L DeDiego
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- David H. Smith Center for Vaccine Biology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain.
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19
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Klemm C, Boergeling Y, Ludwig S, Ehrhardt C. Immunomodulatory Nonstructural Proteins of Influenza A Viruses. Trends Microbiol 2018; 26:624-636. [PMID: 29373257 DOI: 10.1016/j.tim.2017.12.006] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 12/07/2017] [Accepted: 12/15/2017] [Indexed: 12/23/2022]
Abstract
Influenza epidemics and pandemics still represent a severe public health threat and cause significant morbidity and mortality worldwide. As intracellular parasites, influenza viruses are strongly dependent on the host cell machinery. To ensure efficient production of progeny viruses, viral proteins extensively interfere with cellular signalling pathways to inhibit antiviral responses or to activate virus-supportive functions. Here, we review various functions of the influenza virus nonstructural proteins NS1, PB1-F2, and PA-X in infected cells and how post-transcriptional modifications of these proteins affect the viral life cycle. Furthermore, we discuss newly discovered interactions between these proteins and the antiviral interferon response.
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Affiliation(s)
- Carolin Klemm
- Institute of Virology Muenster (IVM), Westfaelische Wilhelms-University Muenster, Von-Esmarch-Str. 56, D-48149 Muenster, Germany
| | - Yvonne Boergeling
- Institute of Virology Muenster (IVM), Westfaelische Wilhelms-University Muenster, Von-Esmarch-Str. 56, D-48149 Muenster, Germany
| | - Stephan Ludwig
- Institute of Virology Muenster (IVM), Westfaelische Wilhelms-University Muenster, Von-Esmarch-Str. 56, D-48149 Muenster, Germany
| | - Christina Ehrhardt
- Institute of Virology Muenster (IVM), Westfaelische Wilhelms-University Muenster, Von-Esmarch-Str. 56, D-48149 Muenster, Germany.
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20
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Vasin AV, Petrova-Brodskaya AV, Plotnikova MA, Tsvetkov VB, Klotchenko SA. EVOLUTIONARY DYNAMICS OF STRUCTURAL AND FUNCTIONAL DOMAINS OF INFLUENZA A VIRUS NS1 PROTEIN. Vopr Virusol 2017; 62:246-258. [PMID: 36494956 DOI: 10.18821/0507-4088-2017-62-6-246-258] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Indexed: 12/13/2022]
Abstract
Influenza A virus (IAV) NS1 protein is one of the key viral factors responsible for virus-host interactions. NS1 counteracts host antiviral defense, participates in the processing and export of cellular mRNAs, regulates the activity of viral RNA polymerase and the expression of viral genes, and influences the cellular signaling systems. Multiple NS1 functions are carried out due to the interactions with cellular factors, the number of which exceeds one hundred. It is noteworthy that only two segments of IAV genome - NS and NP - did not undergo reassortment and evolved in the course of genetic drift, beginning with the pandemic of 1918 to the present. This fact may indicate the importance of NS1 and its numerous interactions with cellular factors in the interspecific adaptation of the virus. The review presents data on the evolution of the human IAV NS1 protein and analysis of the amino acid substitutions in the main structural and functional domains of NS1 protein during evolution.
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Affiliation(s)
- A V Vasin
- Research Institute of Influenza.,Peter the Great St. Petersburg Polytechnic University
| | - A V Petrova-Brodskaya
- Research Institute of Influenza.,Peter the Great St. Petersburg Polytechnic University
| | | | - V B Tsvetkov
- Research Institute of Influenza.,A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences.,Federal Research and Clinical Center of Physical-Chemical Medicine
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21
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Mok BWY, Liu H, Chen P, Liu S, Lau SY, Huang X, Liu YC, Wang P, Yuen KY, Chen H. The role of nuclear NS1 protein in highly pathogenic H5N1 influenza viruses. Microbes Infect 2017; 19:587-596. [PMID: 28903072 DOI: 10.1016/j.micinf.2017.08.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 08/31/2017] [Accepted: 08/31/2017] [Indexed: 11/28/2022]
Abstract
The non-structural protein (NS1) of influenza A viruses (IAV) performs multiple functions during viral infection. NS1 contains two nuclear localization signals (NLS): NLS1 and NLS2. The NS1 protein is located predominantly in the nucleus during the early stages of infection and subsequently exported to the cytoplasm. A nonsense mutation that results in a large deletion in the carboxy-terminal region of the NS1 protein that contains the NLS2 domain was found in some IAV subtypes, including highly pathogenic avian influenza (HPAI) H7N9 and H5N1 viruses. We introduced different mutations into the NLS domains of NS1 proteins in various strains of IAV, and demonstrated that mutation of the NLS2 region in the NS1 protein of HPAI H5N1 viruses severely affects its nuclear localization pattern. H5N1 viruses expressing NS1 protein that is unable to localize to the nucleus are less potent in antagonizing cellular antiviral responses than viruses expressing wild-type NS1. However, no significant difference was observed with respect to viral replication and pathogenesis. In contrast, the replication and antiviral defenses of H1N1 viruses are greatly attenuated when nuclear localization of the NS1 protein is blocked. Our data reveals a novel functional plasticity for NS1 proteins among different IAV subtypes.
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Affiliation(s)
- Bobo Wing-Yee Mok
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Honglian Liu
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Pin Chen
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Siwen Liu
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Siu-Ying Lau
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Xiaofeng Huang
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Yen-Chin Liu
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Pui Wang
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Kwok-Yung Yuen
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - Honglin Chen
- State Key Laboratory for Emerging Infectious Diseases and Department of Microbiology, The University of Hong Kong, Hong Kong, China.
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22
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Huang X, Zheng M, Wang P, Mok BWY, Liu S, Lau SY, Chen P, Liu YC, Liu H, Chen Y, Song W, Yuen KY, Chen H. An NS-segment exonic splicing enhancer regulates influenza A virus replication in mammalian cells. Nat Commun 2017; 8:14751. [PMID: 28323816 PMCID: PMC5364394 DOI: 10.1038/ncomms14751] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 01/26/2017] [Indexed: 01/04/2023] Open
Abstract
Influenza virus utilizes host splicing machinery to process viral mRNAs expressed from both M and NS segments. Through genetic analysis and functional characterization, we here show that the NS segment of H7N9 virus contains a unique G540A substitution, located within a previously undefined exonic splicing enhancer (ESE) motif present in the NEP mRNA of influenza A viruses. G540A supports virus replication in mammalian cells while retaining replication ability in avian cells. Host splicing regulator, SF2, interacts with this ESE to regulate splicing of NEP/NS1 mRNA and G540A substitution affects SF2–ESE interaction. The NS1 protein directly interacts with SF2 in the nucleus and modulates splicing of NS mRNAs during virus replication. We demonstrate that splicing of NEP/NS1 mRNA is regulated through a cis NEP-ESE motif and suggest a unique NEP-ESE may contribute to provide H7N9 virus with the ability to both circulate efficiently in avian hosts and replicate in mammalian cells. Some circulating avian influenza A viruses can infect humans, but the mechanism enabling species jump is poorly understood. Here, Huang et al. identify a nucleotide in NEP of avian H7N9 viruses that affects splicing efficiency of the NS segment and supports virus replication in avian and mammalian cells.
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Affiliation(s)
- Xiaofeng Huang
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong SAR, China
| | - Min Zheng
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong SAR, China
| | - Pui Wang
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong SAR, China
| | - Bobo Wing-Yee Mok
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong SAR, China
| | - Siwen Liu
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong SAR, China
| | - Siu-Ying Lau
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China
| | - Pin Chen
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong SAR, China
| | - Yen-Chin Liu
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong SAR, China
| | - Honglian Liu
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong SAR, China
| | - Yixin Chen
- National Institute of Diagnostics and Vaccine Development in Infectious Diseases, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiamen 361005, China
| | - Wenjun Song
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Department of Biotechnology, College of Life Science and Technology, Jinan University, 601 Huangpu Avenue West, Guangzhou 510632, China
| | - Kwok-Yung Yuen
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Department of Biotechnology, College of Life Science and Technology, Jinan University, 601 Huangpu Avenue West, Guangzhou 510632, China
| | - Honglin Chen
- State Key Laboratory for Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong, Hong Kong SAR, China.,Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The University of Hong Kong, Hong Kong SAR, China.,National Institute of Diagnostics and Vaccine Development in Infectious Diseases, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiamen 361005, China
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23
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Zheng W, Cao S, Chen C, Li J, Zhang S, Jiang J, Niu Y, Fan W, Li Y, Bi Y, Gao GF, Sun L, Liu W. Threonine 80 phosphorylation of non-structural protein 1 regulates the replication of influenza A virus by reducing the binding affinity with RIG-I. Cell Microbiol 2017; 19:e12643. [PMID: 27376632 DOI: 10.1111/cmi.12643] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 06/30/2016] [Accepted: 06/30/2016] [Indexed: 11/29/2022]
Abstract
Influenza A virus evades host antiviral defense through hijacking innate immunity by its non-structural protein 1 (NS1). By using mass spectrometry, threonine 80 (T80) was identified as a novel phosphorylated residue in the NS1 of the influenza virus A/WSN/1933(H1N1). By generating recombinant influenza viruses encoding NS1 T80 mutants, the roles of this phosphorylation site were characterized during viral replication. The T80E (phosphomimetic) mutant attenuated virus replication, whereas the T80A (non-phosphorylatable) mutant did not. Similar phenotypes were observed for these mutants in a mouse model experiment. In further study, the T80E mutant decreased the binding capacity between NS1 and viral nucleoprotein (NP), leading to impaired viral ribonucleoprotein (vRNP)-mediated viral transcription. The T80E mutant was also unable to inhibit interferon (IFN) production by reducing the binding affinity between NS1 and retinoic acid-induced gene 1 protein (RIG-I), causing attenuation of virus replication. Taken together, the present study reveals that T80 phosphorylation of NS1 reduced influenza virus replication through controlling RIG-I-mediated IFN production and vRNP activity.
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Affiliation(s)
- Weinan Zheng
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Shuaishuai Cao
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Can Chen
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jing Li
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Shuang Zhang
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Jingwen Jiang
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Yange Niu
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Wenhui Fan
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Yun Li
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Yuhai Bi
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - George F Gao
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
- Office of Director-General, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Lei Sun
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Wenjun Liu
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
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24
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Barba M, Daly JM. The Influenza NS1 Protein: What Do We Know in Equine Influenza Virus Pathogenesis? Pathogens 2016; 5:pathogens5030057. [PMID: 27589809 PMCID: PMC5039437 DOI: 10.3390/pathogens5030057] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Revised: 08/24/2016] [Accepted: 08/27/2016] [Indexed: 12/22/2022] Open
Abstract
Equine influenza virus remains a serious health and potential economic problem throughout most parts of the world, despite intensive vaccination programs in some horse populations. The influenza non-structural protein 1 (NS1) has multiple functions involved in the regulation of several cellular and viral processes during influenza infection. We review the strategies that NS1 uses to facilitate virus replication and inhibit antiviral responses in the host, including sequestering of double-stranded RNA, direct modulation of protein kinase R activity and inhibition of transcription and translation of host antiviral response genes such as type I interferon. Details are provided regarding what it is known about NS1 in equine influenza, especially concerning C-terminal truncation. Further research is needed to determine the role of NS1 in equine influenza infection, which will help to understand the pathophysiology of complicated cases related to cytokine imbalance and secondary bacterial infection, and to investigate new therapeutic and vaccination strategies.
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Affiliation(s)
- Marta Barba
- Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.
| | - Janet M Daly
- School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington LE12 5RD, UK.
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25
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Zhao X, Tefsen B, Li Y, Qi J, Lu G, Shi Y, Yan J, Xiao H, Gao GF. The NS1 gene from bat-derived influenza-like virus H17N10 can be rescued in influenza A PR8 backbone. J Gen Virol 2016; 97:1797-1806. [DOI: 10.1099/jgv.0.000509] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Affiliation(s)
- Xuejin Zhao
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China
- Center for Influenza Research and Early-warning (CASCIRE), Chinese Academy of Sciences, Beijing 100101, P. R. China
| | - Boris Tefsen
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China
- Center for Influenza Research and Early-warning (CASCIRE), Chinese Academy of Sciences, Beijing 100101, P. R. China
- Department of Biological Sciences, Xi’an Jiaotong-Liverpool University, No 111, Ren Ai Road, Dushu Lake Higher Education Town, Suzhou Industrial Park (SIP), Suzhou 215123, P. R. China
| | - Yan Li
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China
- Center for Influenza Research and Early-warning (CASCIRE), Chinese Academy of Sciences, Beijing 100101, P. R. China
| | - Jianxun Qi
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China
- Center for Influenza Research and Early-warning (CASCIRE), Chinese Academy of Sciences, Beijing 100101, P. R. China
| | - Guangwen Lu
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China
- Center for Influenza Research and Early-warning (CASCIRE), Chinese Academy of Sciences, Beijing 100101, P. R. China
| | - Yi Shi
- Center for Influenza Research and Early-warning (CASCIRE), Chinese Academy of Sciences, Beijing 100101, P. R. China
- Beijing Institute of Life Science, Chinese Academy of Sciences, Beijing 100101, P. R. China
| | - Jinghua Yan
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China
| | - Haixia Xiao
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
- Center for Influenza Research and Early-warning (CASCIRE), Chinese Academy of Sciences, Beijing 100101, P. R. China
| | - George F. Gao
- Beijing Institute of Life Science, Chinese Academy of Sciences, Beijing 100101, P. R. China
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
- Center for Influenza Research and Early-warning (CASCIRE), Chinese Academy of Sciences, Beijing 100101, P. R. China
- Office of Director-General, Chinese Center for Disease Control and Prevention, Beijing 102206, P. R. China
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, P. R. China
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26
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Ylösmäki L, Fagerlund R, Kuisma I, Julkunen I, Saksela K. Nuclear Translocation of Crk Adaptor Proteins by the Influenza A Virus NS1 Protein. Viruses 2016; 8:101. [PMID: 27092521 PMCID: PMC4848595 DOI: 10.3390/v8040101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 03/31/2016] [Accepted: 04/04/2016] [Indexed: 12/18/2022] Open
Abstract
The non-structural protein-1 (NS1) of many influenza A strains, especially those of avian origin, contains an SH3 ligand motif, which binds tightly to the cellular adaptor proteins Crk (Chicken tumor virus number 10 (CT10) regulator of kinase) and Crk-like adapter protein (CrkL). This interaction has been shown to potentiate NS1-induced activation of the phosphatidylinositol 3-kinase (PI3K), but additional effects on the host cell physiology may exist. Here we show that NS1 can induce an efficient translocation of Crk proteins from the cytoplasm into the nucleus, which results in an altered pattern of nuclear protein tyrosine phosphorylation. This was not observed using NS1 proteins deficient in SH3 binding or engineered to be exclusively cytoplasmic, indicating a physical role for NS1 as a carrier in the nuclear translocation of Crk. These data further emphasize the role of Crk proteins as host cell interaction partners of NS1, and highlight the potential for host cell manipulation gained by a viral protein simply via acquiring a short SH3 binding motif.
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Affiliation(s)
- Leena Ylösmäki
- Department of Virology, University of Helsinki and Helsinki University Hospital, 00014 Helsinki, Finland.
| | - Riku Fagerlund
- Department of Virology, University of Helsinki and Helsinki University Hospital, 00014 Helsinki, Finland.
| | - Inka Kuisma
- Department of Virology, University of Helsinki and Helsinki University Hospital, 00014 Helsinki, Finland.
| | - Ilkka Julkunen
- Department of Virology, University of Turku, 20520 Turku, Finland and Virology Unit, Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare (THL), 00300 Helsinki, Finland.
| | - Kalle Saksela
- Department of Virology, University of Helsinki and Helsinki University Hospital, 00014 Helsinki, Finland.
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27
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A high-throughput screening system targeting the nuclear export pathway via the third nuclear export signal of influenza A virus nucleoprotein. Virus Res 2016; 217:23-31. [PMID: 26948263 DOI: 10.1016/j.virusres.2016.02.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Accepted: 02/07/2016] [Indexed: 11/22/2022]
Abstract
Two classes of antiviral drugs, M2 channel inhibitors and neuraminidase (NA) inhibitors, are currently approved for the treatment of influenza; however, the development of resistance against these agents limits their efficacy. Therefore, the identification of new targets and the development of new antiviral drugs against influenza are urgently needed. The third nuclear export signal (NES3) of nucleoprotein (NP) is the most important for viral replication among seven NESs encoded by four viral proteins, NP, M1, NS1, and NS2. NP-NES3 is critical for the nuclear export of NP, and targeting NP-NES3 is therefore a promising strategy that may lead to the development of antiviral drugs. However, a high-throughput screening (HTS) system to identify inhibitors of NP nuclear export has not been established. Here, we developed a novel HTS system to evaluate the inhibitory effects of compounds on the nuclear export pathway mediated by NP-NES3 using a MDCK cell line stably expressing NP-NES3 fused to a green fluorescent protein from aequorea coerulescens (AcGFP-NP-NES3) and a cell imaging analyzer. This HTS system was used to screen a 9600-compound library, leading to the identification of several hit compounds with inhibitory activity against the nuclear export of AcGFP-NP-NES3. The present HTS system provides a useful strategy for the identification of inhibitors targeting the nuclear export of NP via its NES3 sequence.
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28
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Gu J, Wang L, Jin Y, Lin C, Wang H, Zhou N, Xing G, Liao M, Zhou J. Characterization of specific antigenic epitopes and the nuclear export signal of the Porcine circovirus 2 ORF3 protein. Vet Microbiol 2016; 184:40-50. [PMID: 26854343 DOI: 10.1016/j.vetmic.2016.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2015] [Revised: 12/22/2015] [Accepted: 01/05/2016] [Indexed: 12/19/2022]
Abstract
Porcine circovirus 2 (PCV2) is the etiological agent of postweaning multisystemic wasting syndrome. PCV2 ORF3 protein is a nonstructural protein known to induce apoptosis, but little is known about the biological function of ORF3 protein. Therefore, we undertook this study to map ORF3 protein epitopes recognized by a panel of monoclonal antibodies (mAbs) and to characterize putative nuclear localization (NLS) and nuclear export (NES) sequences in ORF3. The linear epitopes targeted by two previously published mAbs 3B1 and 1H3 and a novel mouse mAb 3C3 were defined using overlapping pools of peptides. Here, we find that ORF3 in PCV2 infected cells contains a conformational epitope targeted by the antibody 3C3, which is distinct from linear epitopes recognized by the antibodies 3B1 and 1H3 in recombinant ORF3 protein. These results suggest that the linear epitope recognized by 3B1 and 1H3 is masked in PCV2 infected cells, and that the conformational epitope is unique to PCV2 infection. Furthermore, we find that ORF3 protein expressed in cytoplasm in early stages of PCV2 infection and then accumulated in nucleus over time. Moreover, we localize a NES at the N-terminus (residues 1-35aa) of ORF3 which plays critical role in nuclear export activity. These findings provide a novel insight that deepens our understanding of the biological function of PCV2 ORF3.
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Affiliation(s)
- Jinyan Gu
- Institute of Immunity and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Lun Wang
- Key Laboratory of Animal Virology, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, PR China
| | - Yulan Jin
- Key Laboratory of Animal Virology, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, PR China
| | - Cui Lin
- Key Laboratory of Animal Virology, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, PR China
| | - Huijuan Wang
- Key Laboratory of Animal Virology, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, PR China
| | - Niu Zhou
- Key Laboratory of Animal Virology, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, PR China
| | - Gang Xing
- Institute of Immunity and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Min Liao
- Key Laboratory of Animal Virology, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, PR China.
| | - Jiyong Zhou
- Institute of Immunity and College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, PR China; Key Laboratory of Animal Virology, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, PR China; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, Zhejiang University, Hangzhou 310058, PR China.
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29
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Nucleocytoplasmic shuttling of influenza A virus proteins. Viruses 2015; 7:2668-82. [PMID: 26008706 PMCID: PMC4452925 DOI: 10.3390/v7052668] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Accepted: 05/20/2015] [Indexed: 12/31/2022] Open
Abstract
Influenza viruses transcribe and replicate their genomes in the nuclei of infected host cells. The viral ribonucleoprotein (vRNP) complex of influenza virus is the essential genetic unit of the virus. The viral proteins play important roles in multiple processes, including virus structural maintenance, mediating nucleocytoplasmic shuttling of the vRNP complex, virus particle assembly, and budding. Nucleocytoplasmic shuttling of viral proteins occurs throughout the entire virus life cycle. This review mainly focuses on matrix protein (M1), nucleoprotein (NP), nonstructural protein (NS1), and nuclear export protein (NEP), summarizing the mechanisms of their nucleocytoplasmic shuttling and the regulation of virus replication through their phosphorylation to further understand the regulation of nucleocytoplasmic shuttling in host adaptation of the viruses.
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30
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Cheong WC, Kang HR, Yoon H, Kang SJ, Ting JPY, Song MJ. Influenza A Virus NS1 Protein Inhibits the NLRP3 Inflammasome. PLoS One 2015; 10:e0126456. [PMID: 25978411 PMCID: PMC4433236 DOI: 10.1371/journal.pone.0126456] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 04/02/2015] [Indexed: 12/23/2022] Open
Abstract
The inflammasome is a molecular platform that stimulates the activation of caspase-1 and the processing of pro-interleukin (IL)-1β and pro-IL-18 for secretion. The NOD-like receptor family, pyrin domain containing 3 (NLRP3) protein is activated by diverse molecules and pathogens, leading to the formation of the NLRP3 inflammasome. Recent studies showed that the NLRP3 inflammasome mediates innate immunity against influenza A virus (IAV) infection. In this study, we investigated the function of the IAV non-structural protein 1 (NS1) in the modulation of NLRP3 inflammasome. We found that NS1 proteins derived from both highly pathogenic and low pathogenic strains efficiently decreased secretion of IL-1β and IL-18 from THP-1 cells treated with LPS and ATP. NS1 overexpression significantly impaired the transcription of proinflammatory cytokines by inhibiting transactivation of the nuclear factor-κB (NF-κB), a major transcription activator. Furthermore, NS1 physically interacted with endogenous NLRP3 and activation of the NLRP3 inflammasome was abrogated in NS1-expressing THP-1 cells. These findings suggest that NS1 downregulates NLRP3 inflammasome activation by targeting NLRP3 as well as NF-κB, leading to a reduction in the levels of inflammatory cytokines as a viral immune evasion strategy.
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Affiliation(s)
- Woo-Chang Cheong
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 136–713, Republic of Korea
| | - Hye-Ri Kang
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 136–713, Republic of Korea
| | - Hyunyee Yoon
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 136–713, Republic of Korea
- Laboratory of Protein Immunology, Biomedical Research Institute, Seoul National University Hospital, Seoul, 110–744, Republic of Korea
| | - Suk-Jo Kang
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, 305–701, Republic of Korea
| | - Jenny P.-Y. Ting
- Departments of Genetics, Microbiology and Immunology, Center for Translational Immunology and Inflammatory Disease Institute, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, United States of America
| | - Moon Jung Song
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 136–713, Republic of Korea
- * E-mail:
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31
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Krug RM. Functions of the influenza A virus NS1 protein in antiviral defense. Curr Opin Virol 2015; 12:1-6. [PMID: 25638592 DOI: 10.1016/j.coviro.2015.01.007] [Citation(s) in RCA: 148] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 01/07/2015] [Indexed: 12/17/2022]
Abstract
Influenza A viruses counteract host antiviral activities, especially the production of interferons (IFNs) and the activities of IFN-induced proteins that inhibit virus replication. The viral NS1 protein is largely responsible for countering these IFN antiviral responses, but there are functional differences between the NS1 proteins of different virus strains. The NS1 protein inhibits IFN production by two mechanisms: inhibition of the activation of IRF3 and IFN transcription; and inhibition of the processing of IFN pre-mRNAs. The NS1 proteins of several virus strains do not inhibit IRF3 activation, and the NS1 protein of one virus strain does not inhibit the processing of IFN pre-mRNAs. Many issues remain concerning the mechanisms of action of the various NS1 proteins in countering the IFN response.
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Affiliation(s)
- Robert M Krug
- Department of Molecular Biosciences, Center for Infectious Disease, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, USA.
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32
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Abstract
The non-structural protein 1 of influenza virus (NS1) is a relatively small polypeptide with an outstanding number of ascribed functions. NS1 is the main viral antagonist of the innate immune response during influenza virus infection, chiefly by inhibiting the type I interferon system at multiple steps. As such, its role is critical to overcome the first barrier the host presents to halt the viral infection. However, the pro-viral activities of this well-studied protein go far beyond and include regulation of viral RNA and protein synthesis, and disruption of the host cell homeostasis by dramatically affecting general gene expression while tweaking the PI3K signaling network. Because of all of this, NS1 is a key virulence factor that impacts influenza pathogenesis, and adaptation to new hosts, making it an attractive target for control strategies. Here, we will overview the many roles that have been ascribed to the NS1 protein, and give insights into the sequence features and structural properties that make them possible, highlighting the need to understand how NS1 can actually perform all of these functions during viral infection.
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Affiliation(s)
- Juan Ayllon
- Department of Microbiology, Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
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33
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Marc D. Influenza virus non-structural protein NS1: interferon antagonism and beyond. J Gen Virol 2014; 95:2594-2611. [PMID: 25182164 DOI: 10.1099/vir.0.069542-0] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Most viruses express one or several proteins that counter the antiviral defences of the host cell. This is the task of non-structural protein NS1 in influenza viruses. Absent in the viral particle, but highly expressed in the infected cell, NS1 dramatically inhibits cellular gene expression and prevents the activation of key players in the IFN system. In addition, NS1 selectively enhances the translation of viral mRNAs and may regulate the synthesis of viral RNAs. Our knowledge of the virus and of NS1 has increased dramatically during the last 15 years. The atomic structure of NS1 has been determined, many cellular partners have been identified and its multiple activities have been studied in depth. This review presents our current knowledge, and attempts to establish relationships between the RNA sequence, the structure of the protein, its ligands, its activities and the pathogenicity of the virus. A better understanding of NS1 could help in elaborating novel antiviral strategies, based on either live vaccines with altered NS1 or on small-compound inhibitors of NS1.
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Affiliation(s)
- Daniel Marc
- Université François Rabelais, UMR1282 Infectiologie et Santé Publique, 37000 Tours, France.,Pathologie et Immunologie Aviaire, INRA, UMR1282 Infectiologie et Santé Publique, 37380 Nouzilly, France
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Chutiwitoonchai N, Kakisaka M, Yamada K, Aida Y. Comparative analysis of seven viral nuclear export signals (NESs) reveals the crucial role of nuclear export mediated by the third NES consensus sequence of nucleoprotein (NP) in influenza A virus replication. PLoS One 2014; 9:e105081. [PMID: 25119991 PMCID: PMC4132019 DOI: 10.1371/journal.pone.0105081] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 07/17/2014] [Indexed: 11/19/2022] Open
Abstract
The assembly of influenza virus progeny virions requires machinery that exports viral genomic ribonucleoproteins from the cell nucleus. Currently, seven nuclear export signal (NES) consensus sequences have been identified in different viral proteins, including NS1, NS2, M1, and NP. The present study examined the roles of viral NES consensus sequences and their significance in terms of viral replication and nuclear export. Mutation of the NP-NES3 consensus sequence resulted in a failure to rescue viruses using a reverse genetics approach, whereas mutation of the NS2-NES1 and NS2-NES2 sequences led to a strong reduction in viral replication kinetics compared with the wild-type sequence. While the viral replication kinetics for other NES mutant viruses were also lower than those of the wild-type, the difference was not so marked. Immunofluorescence analysis after transient expression of NP-NES3, NS2-NES1, or NS2-NES2 proteins in host cells showed that they accumulated in the cell nucleus. These results suggest that the NP-NES3 consensus sequence is mostly required for viral replication. Therefore, each of the hydrophobic (Φ) residues within this NES consensus sequence (Φ1, Φ2, Φ3, or Φ4) was mutated, and its viral replication and nuclear export function were analyzed. No viruses harboring NP-NES3 Φ2 or Φ3 mutants could be rescued. Consistent with this, the NP-NES3 Φ2 and Φ3 mutants showed reduced binding affinity with CRM1 in a pull-down assay, and both accumulated in the cell nucleus. Indeed, a nuclear export assay revealed that these mutant proteins showed lower nuclear export activity than the wild-type protein. Moreover, the Φ2 and Φ3 residues (along with other Φ residues) within the NP-NES3 consensus were highly conserved among different influenza A viruses, including human, avian, and swine. Taken together, these results suggest that the Φ2 and Φ3 residues within the NP-NES3 protein are important for its nuclear export function during viral replication.
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Affiliation(s)
| | | | - Kazunori Yamada
- Computational Biology Research Center, National Institute of Advanced Industrial Science and Technology, Koto, Tokyo, Japan
| | - Yoko Aida
- Viral Infectious Diseases Unit, RIKEN, Wako, Saitama, Japan
- * E-mail:
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Tynell J, Melén K, Julkunen I. Mutations within the conserved NS1 nuclear export signal lead to inhibition of influenza A virus replication. Virol J 2014; 11:128. [PMID: 25023993 PMCID: PMC4112715 DOI: 10.1186/1743-422x-11-128] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 07/04/2014] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The influenza A virus NS1 protein is a virulence factor and an antagonist of host cell innate immune responses. During virus infection NS1 protein has several functions both in the nucleus and in the cytoplasm and its intracellular localization is regulated by one or two nuclear localization signals (NLS) and a nuclear export signal (NES). METHODS In order to investigate the role of NS1 NES in intracellular localization, virus life cycle and host interferon responses, we generated recombinant A/Udorn/72 viruses harboring point mutations in the NES sequence. RESULTS NS1 NES was found to be inactivated by several of the mutations resulting in nuclear retention of NS1 at late stages of infection confirming that this sequence is a bona fide functional NES. Some of the mutant viruses showed reduced growth properties in cell culture, inability to antagonize host cell interferon production and increased p-IRF3 levels, but no clear correlation between these phenotypes and NS1 localization could be made. Impaired activation of Akt phosphorylation by the replication-deficient viruses indicates possible disruption of NS1-p85β interaction by mutations in the NES region. CONCLUSION We conclude that mutations within the NS1 NES result in impairment of several NS1 functions which extends further from the NES site being only involved in regulating the nuclear-cytoplasmic trafficking of NS1.
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Affiliation(s)
- Janne Tynell
- Virology Unit, Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare (THL), Mannerheimintie 166, FIN-00300 Helsinki, Finland
| | - Krister Melén
- Virology Unit, Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare (THL), Mannerheimintie 166, FIN-00300 Helsinki, Finland
| | - Ilkka Julkunen
- Virology Unit, Department of Infectious Disease Surveillance and Control, National Institute for Health and Welfare (THL), Mannerheimintie 166, FIN-00300 Helsinki, Finland
- Department of Virology, University of Turku, Turku, Finland
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Lalime EN, Pekosz A. The R35 residue of the influenza A virus NS1 protein has minimal effects on nuclear localization but alters virus replication through disrupting protein dimerization. Virology 2014; 458-459:33-42. [PMID: 24928037 DOI: 10.1016/j.virol.2014.04.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 04/05/2014] [Accepted: 04/09/2014] [Indexed: 10/25/2022]
Abstract
The influenza A virus NS1 protein has a nuclear localization sequence (NLS) in the amino terminal region. This NLS overlaps sequences that are important for RNA binding as well as protein dimerization. To assess the significance of the NS1 NLS on influenza virus replication, the NLS amino acids were individually mutated to alanines and recombinant viruses encoding these mutations were rescued. Viruses containing NS1 proteins with mutations at R37, R38 and K41 displayed minimal changes in replication or NS1 protein nuclear localization. Recombinant viruses encoding NS1 R35A were not recovered but viruses containing second site mutations at position D39 in addition to the R35A mutation were isolated. The mutations at position 39 were shown to partially restore NS1 protein dimerization but had minimal effects on nuclear localization. These data indicate that the amino acids in the NS1 NLS region play a more important role in protein dimerization compared to nuclear localization.
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Affiliation(s)
- Erin N Lalime
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe Street, Suite E5132, Baltimore, MD 21205-2103, USA
| | - Andrew Pekosz
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, 615 North Wolfe Street, Suite E5132, Baltimore, MD 21205-2103, USA.
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Emergence of a highly pathogenic avian influenza virus from a low-pathogenic progenitor. J Virol 2014; 88:4375-88. [PMID: 24501401 DOI: 10.1128/jvi.03181-13] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Avian influenza (AI) viruses of the H7 subtype have the potential to evolve into highly pathogenic (HP) viruses that represent a major economic problem for the poultry industry and a threat to global health. However, the emergence of HPAI viruses from low-pathogenic (LPAI) progenitor viruses currently is poorly understood. To investigate the origin and evolution of one of the most important avian influenza epidemics described in Europe, we investigated the evolutionary and spatial dynamics of the entire genome of 109 H7N1 (46 LPAI and 63 HPAI) viruses collected during Italian H7N1 outbreaks between March 1999 and February 2001. Phylogenetic analysis revealed that the LPAI and HPAI epidemics shared a single ancestor, that the HPAI strains evolved from the LPAI viruses in the absence of reassortment, and that there was a parallel emergence of mutations among HPAI and later LPAI lineages. Notably, an ultradeep-sequencing analysis demonstrated that some of the amino acid changes characterizing the HPAI virus cluster were already present with low frequency within several individual viral populations from the beginning of the LPAI H7N1 epidemic. A Bayesian phylogeographic analysis revealed stronger spatial structure during the LPAI outbreak, reflecting the more rapid spread of the virus following the emergence of HPAI. The data generated in this study provide the most complete evolutionary and phylogeographic analysis of epidemiologically intertwined high- and low-pathogenicity viruses undertaken to date and highlight the importance of implementing prompt eradication measures against LPAI to prevent the appearance of viruses with fitness advantages and unpredictable pathogenic properties. IMPORTANCE The Italian H7 AI epidemic of 1999 to 2001 was one of the most important AI outbreaks described in Europe. H7 viruses have the ability to evolve into HP forms from LP precursors, although the mechanisms underlying this evolutionary transition are only poorly understood. We combined epidemiological information, whole-genome sequence data, and ultradeep sequencing approaches to provide the most complete characterization of the evolution of HPAI from LPAI viruses undertaken to date. Our analysis revealed that the LPAI viruses were the direct ancestors of the HPAI strains and identified low-frequency minority variants with HPAI mutations that were present in the LPAI samples. Spatial analysis provided key information for the design of effective control strategies for AI at both local and global scales. Overall, this work highlights the importance of implementing rapid eradication measures to prevent the emergence of novel influenza viruses with severe pathogenic properties.
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Forbes N, Selman M, Pelchat M, Jia JJ, Stintzi A, Brown EG. Identification of adaptive mutations in the influenza A virus non-structural 1 gene that increase cytoplasmic localization and differentially regulate host gene expression. PLoS One 2013; 8:e84673. [PMID: 24391972 PMCID: PMC3877356 DOI: 10.1371/journal.pone.0084673] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 11/18/2013] [Indexed: 12/22/2022] Open
Abstract
The NS1 protein of influenza A virus (IAV) is a multifunctional virulence factor. We have previously characterized gain-of-function mutations in the NS1 protein arising from the experimental adaptation of the human isolate A/Hong Kong/1/1968(H3N2) (HK) to the mouse. The majority of these mouse adapted NS1 mutations were demonstrated to increase virulence, viral fitness, and interferon antagonism, but differ in binding to the post-transcriptional processing factor cleavage and polyadenylation specificity factor 30 (CPSF30). Because nuclear trafficking is a major genetic determinant of influenza virus host adaptation, we assessed subcellular localization and host gene expression of NS1 adaptive mutations. Recombinant HK viruses with adaptive mutations in the NS1 gene were assessed for NS1 protein subcellular localization in mouse and human cells using confocal microscopy and cellular fractionation. In human cells the HK wild-type (HK-wt) virus NS1 protein partitioned equivalently between the cytoplasm and nucleus but was defective in cytoplasmic localization in mouse cells. Several adaptive mutations increased the proportion of NS1 in the cytoplasm of mouse cells with the greatest effects for mutations M106I and D125G. The host gene expression profile of the adaptive mutants was determined by microarray analysis of infected mouse cells to show either high or low extents of host-gene regulation (HGR or LGR) phenotypes. While host genes were predominantly down regulated for the HGR group of mutants (D2N, V23A, F103L, M106I+L98S, L98S, M106V, and M106V+M124I), the LGR phenotype mutants (D125G, M106I, V180A, V226I, and R227K) were characterized by a predominant up regulation of host genes. CPSF30 binding affinity of NS1 mutants did not predict effects on host gene expression. To our knowledge this is the first report of roles of adaptive NS1 mutations that impact intracellular localization and regulation of host gene expression.
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Affiliation(s)
- Nicole Forbes
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
- Emerging Pathogens Research Centre, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Mohammed Selman
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
- Emerging Pathogens Research Centre, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Martin Pelchat
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Jian Jun Jia
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Alain Stintzi
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Earl G. Brown
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
- Emerging Pathogens Research Centre, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
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hnRNP A2/B1 interacts with influenza A viral protein NS1 and inhibits virus replication potentially through suppressing NS1 RNA/protein levels and NS1 mRNA nuclear export. Virology 2013; 449:53-61. [PMID: 24418537 DOI: 10.1016/j.virol.2013.11.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 08/08/2013] [Accepted: 11/06/2013] [Indexed: 12/19/2022]
Abstract
The NS1 protein of influenza viruses is a major virulence factor and exerts its function through interacting with viral/cellular RNAs and proteins. In this study, we identified heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) as an interacting partner of NS1 proteins by a proteomic method. Knockdown of hnRNP A2/B1 by small interfering RNA (siRNA) resulted in higher levels of NS vRNA, NS1 mRNA, and NS1 protein in the virus-infected cells. In addition, we demonstrated that hnRNP A2/B1 proteins are associated with NS1 and NS2 mRNAs and that knockdown of hnRNP A2/B1 promotes transport of NS1 mRNA from the nucleus to the cytoplasm in the infected cells. Lastly, we showed that knockdown of hnRNP A2/B1 leads to enhanced virus replication. Our results suggest that hnRNP A2/B1 plays an inhibitory role in the replication of influenza A virus in host cells potentially through suppressing NS1 RNA/protein levels and NS1 mRNA nucleocytoplasmic translocation.
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Exploring naphthyl-carbohydrazides as inhibitors of influenza A viruses. Eur J Med Chem 2013; 71:81-90. [PMID: 24287556 DOI: 10.1016/j.ejmech.2013.10.063] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Revised: 10/22/2013] [Accepted: 10/24/2013] [Indexed: 11/21/2022]
Abstract
A library of hydrazide derivatives was synthesized to target non-structural protein 1 of influenza A virus (NS1) as a means to develop anti-influenza drug leads. The lead compound 3-hydroxy-N-[(Z)-1-(5,6,7,8-tetrahydronaphthalen-2-yl)ethylideneamino]naphthalene-2-carboxamide, which we denoted as "HENC", was identified by its ability to increase the melting temperature of the effector domain (ED) of the NS1 protein, as assayed using differential scanning fluorimetry. A library of HENC analogs was tested for inhibitory effect against influenza A virus replication in MDCK cells. A systematic diversification of HENC revealed the identity of the R group attached to the imine carbon atom significantly influenced the antiviral activity. A phenyl or cyclohexyl at this position yielded the most potent antiviral activity. The phenyl containing compound had antiviral activity similar to that of the active form of oseltamivir (Tamiflu), and had no detectable effect on cell viability.
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41
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Targeting cell division cycle 25 homolog B to regulate influenza virus replication. J Virol 2013; 87:13775-84. [PMID: 24109234 DOI: 10.1128/jvi.01509-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Influenza virus is a worldwide global health concern causing seasonal morbidity mortality and economic burden. Chemotherapeutics is available; however, rapid emergence of drug-resistant influenza virus strains has reduced its efficacy. Thus, there is a need to discover novel antiviral agents. In this study, RNA interference (RNAi) was used to screen host genes required for influenza virus replication. One pro-influenza virus host gene identified was dual-specificity phosphatase cell division cycle 25 B (CDC25B). RNAi screening of CDC25B resulted in reduced influenza A virus replication, and a CDC25B small-molecule inhibitor (NSC95397) inhibited influenza A virus replication in a dose-dependent fashion. Viral RNA synthesis was reduced by NSC95397 in favor of increased beta interferon (IFN-β) expression, and NSC95397 was found to interfere with nuclear localization and chromatin association of NS1, an influenza virus protein. As NS1 has been shown to be chromatin associated and to suppress host transcription, it is likely that CDC25B supports NS1 nuclear function to hijack host transcription machinery in favor of viral RNA synthesis, a process that is blocked by NSC95397. Importantly, NSC95397 treatment protects mice against lethal influenza virus challenge. The findings establish CDC25B as a pro-influenza A virus host factor that may be targeted as a novel influenza A therapeutic strategy.
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Dankar SK, Miranda E, Forbes NE, Pelchat M, Tavassoli A, Selman M, Ping J, Jia J, Brown EG. Influenza A/Hong Kong/156/1997(H5N1) virus NS1 gene mutations F103L and M106I both increase IFN antagonism, virulence and cytoplasmic localization but differ in binding to RIG-I and CPSF30. Virol J 2013; 10:243. [PMID: 23886034 PMCID: PMC3733596 DOI: 10.1186/1743-422x-10-243] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 07/23/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The genetic basis for avian to mammalian host switching in influenza A virus is largely unknown. The human A/HK/156/1997 (H5N1) virus that transmitted from poultry possesses NS1 gene mutations F103L + M106I that are virulence determinants in the mouse model of pneumonia; however their individual roles have not been determined. The emergent A/Shanghai/patient1/2013(H7N9)-like viruses also possess these mutations which may contribute to their virulence and ability to switch species. METHODS NS1 mutant viruses were constructed by reverse genetics and site directed mutagenesis on human and mouse-adapted backbones. Mouse infections assessed virulence, virus yield, tissue infection, and IFN induction. NS1 protein properties were assessed for subcellular distribution, IFN antagonism (mouse and human), CPSF30 and RIG-I domain binding, host transcription (microarray); and the natural prevalence of 103L and 106I mutants was assessed. RESULTS Each of the F103L and M106I mutations contributes additively to virulence to reduce the lethal dose by >800 and >3,200 fold respectively by mediating alveolar tissue infection with >100 fold increased infectious yields. The 106I NS1 mutant lost CPSF binding but the 103L mutant maintained binding that correlated with an increased general decrease in host gene expression in human but not mouse cells. Each mutation positively modulated the inhibition of IFN induction in mouse cells and activation of the IFN-β promoter in human cells but not in combination in human cells indicating negative epistasis. Each of the F103L and M106I mutations restored a defect in cytoplasmic localization of H5N1 NS1 in mouse cells. Human H1N1 and H3N2 NS1 proteins bound to the CARD, helicase and RD RIG-I domains, whereas the H5N1 NS1 with the same consensus 103F and 106M mutations did not bind these domains, which was totally or partially restored by the M106I or F103L mutations respectively. CONCLUSIONS The F103L and M106I mutations in the H5N1 NS1 protein each increased IFN antagonism and mediated interstitial pneumonia in mice that was associated with increased cytoplasmic localization and altered host factor binding. These mutations may contribute to the ability of previous HPAI H5N1 and recent LPAI H7N9 and H6N1 (NS1-103L+106M) viruses to switch hosts and cause disease in humans.
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Affiliation(s)
- Samar K Dankar
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, Ontario K1H 8M5, Canada
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SUMOylation affects the interferon blocking activity of the influenza A nonstructural protein NS1 without affecting its stability or cellular localization. J Virol 2013; 87:5602-20. [PMID: 23468495 DOI: 10.1128/jvi.02063-12] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Our pioneering studies on the interplay between the small ubiquitin-like modifier (SUMO) and influenza A virus identified the nonstructural protein NS1 as the first known SUMO target of influenza virus and one of the most abundantly SUMOylated influenza virus proteins. Here, we further characterize the role of SUMOylation for the A/Puerto Rico/8/1934 (PR8) NS1 protein, demonstrating that NS1 is SUMOylated not only by SUMO1 but also by SUMO2/3 and mapping the main SUMOylation sites in NS1 to residues K219 and K70. Furthermore, by using SUMOylatable and non-SUMOylatable forms of NS1 and an NS1-specific artificial SUMO ligase (ASL) that increases NS1 SUMOylation ~4-fold, we demonstrate that SUMOylation does not affect the stability or cellular localization of PR8 NS1. However, NS1's ability to be SUMOylated appears to affect virus multiplication, as indicated by the delayed growth of a virus expressing the non-SUMOylatable form of NS1 in the interferon (IFN)-competent MDCK cell line. Remarkably, while a non-SUMOylatable form of NS1 exhibited a substantially diminished ability to neutralize IFN production, increasing NS1 SUMOylation beyond its normal levels also exerted a negative effect on its IFN-blocking function. This observation indicates the existence of an optimal level of NS1 SUMOylation that allows NS1 to achieve maximal activity and suggests that the limited amount of SUMOylation normally observed for most SUMO targets may correspond to an optimal level that maximizes the contribution of SUMOylation to protein function. Finally, protein cross-linking data suggest that SUMOylation may affect NS1 function by regulating the abundance of NS1 dimers and trimers in the cell.
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Wang S, Wang K, Zheng C. Interspecies heterokaryon assay to characterize the nucleocytoplasmic shuttling of herpesviral proteins. Methods Mol Biol 2013; 1064:131-140. [PMID: 23996254 DOI: 10.1007/978-1-62703-601-6_9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Nucleocytoplasmic trafficking of proteins plays important roles in processes of the viral life cycle. Interspecies heterokaryon assay is one of the most effective methods to investigate the nucleocytoplasmic trafficking properties of a protein. In our lab, the interspecies heterokaryon assay has been applied to identify a few herpesviral proteins with nucleocytoplasmic shuttling property. In this chapter, the detailed information and methods of the heterokaryon assay are presented.
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Affiliation(s)
- Shuai Wang
- Institute of Biology and Medical Sciences, Soochow University, Jiangsu Suzhou, PR China
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Rahim MN, Selman M, Sauder PJ, Forbes NE, Stecho W, Xu W, Lebar M, Brown EG, Coombs KM. Generation and characterization of a new panel of broadly reactive anti-NS1 mAbs for detection of influenza A virus. J Gen Virol 2012; 94:593-605. [PMID: 23223621 DOI: 10.1099/vir.0.046649-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Influenza A virus (IAV) non-structural protein 1 (NS1) has multiple functions, is essential for virus replication and may be a good target for IAV diagnosis. To generate broadly cross-reactive NS1-specific mAbs, mice were immunized with A/Hong Kong/1/1968 (H3N2) 6×His-tagged NS1 and hybridomas were screened with glutathione S-transferase-conjugated NS1 of A/Puerto Rico/8/1934 (H1N1). mAbs were isotyped and numerous IgG-type clones were characterized further. Most clones specifically recognized NS1 from various H1N1 and H3N2 IAV types by both immunoblot and immunofluorescence microscopy in mouse M1, canine Madin-Darby canine kidney and human A549 cells. mAb epitopes were mapped by overlapping peptides and selective reactivity to the newly described viral NS3 protein. These mAbs detected NS1 in both the cytoplasm and nucleus by immunostaining, and some detected NS1 as early as 5 h post-infection, suggesting their potential diagnostic use for tracking productive IAV replication and characterizing NS1 structure and function. It was also demonstrated that the newly identified NS3 protein is localized in the cytoplasm to high levels.
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Affiliation(s)
- Md Niaz Rahim
- Manitoba Centre for Proteomics and Systems Biology, Room 799, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada.,Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, MB R3E 0J6, Canada
| | - Mohammed Selman
- Emerging Pathogens Research Centre, University of Ottawa, Ottawa, ON K1H 8M5, Canada.,Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Patricia J Sauder
- Manitoba Centre for Proteomics and Systems Biology, Room 799, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada
| | - Nicole E Forbes
- Emerging Pathogens Research Centre, University of Ottawa, Ottawa, ON K1H 8M5, Canada.,Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - William Stecho
- Emerging Pathogens Research Centre, University of Ottawa, Ottawa, ON K1H 8M5, Canada.,Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Wanhong Xu
- Manitoba Centre for Proteomics and Systems Biology, Room 799, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada.,Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, MB R3E 0J6, Canada
| | - Mark Lebar
- Manitoba Centre for Proteomics and Systems Biology, Room 799, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada.,Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, MB R3E 0J6, Canada
| | - Earl G Brown
- Emerging Pathogens Research Centre, University of Ottawa, Ottawa, ON K1H 8M5, Canada.,Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Kevin M Coombs
- Manitoba Institute of Child Health, Room 513, John Buhler Research Centre, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada.,Manitoba Centre for Proteomics and Systems Biology, Room 799, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada.,Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, MB R3E 0J6, Canada
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Adaptive mutation in influenza A virus non-structural gene is linked to host switching and induces a novel protein by alternative splicing. Emerg Microbes Infect 2012; 1:e42. [PMID: 26038410 PMCID: PMC3630925 DOI: 10.1038/emi.2012.38] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Revised: 07/23/2012] [Accepted: 09/19/2012] [Indexed: 01/03/2023]
Abstract
Little is known about the processes that enable influenza A viruses to jump into new host species. Here we show that the non-structural protein1 nucleotide substitution, A374G, encoding the D125G(GAT→GGT) mutation, which evolved during the adaptation of a human virus within a mouse host, activates a novel donor splice site in the non-structural gene, hence producing a novel influenza A viral protein, NS3. Using synonymous 125G mutations that do not activate the novel donor splice site, NS3 was shown to provide replicative gain-of-function. The protein sequence of NS3 is similar to NS1 protein but with an internal deletion of a motif comprised of three antiparallel β-strands spanning codons 126 to 168 in NS1. The NS1-125G(GGT) codon was also found in 33 natural influenza A viruses that were strongly associated with switching from avian to mammalian hosts, including human, swine and canine populations. In addition to the experimental human to mouse switch, the NS1-125G(GGT) codon was selected on avian to human transmission of the 1997 H5N1 and 1999 H9N2 lineages, as well as the avian to swine jump of 1979 H1N1 Eurasian swine influenza viruses, linking the NS1 125G(GGT) codon with host adaptation and switching among multiple species.
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Meng J, Zhang Z, Zheng Z, Liu Y, Wang H. Methionine-101 from one strain of H5N1 NS1 protein determines its IFN-antagonizing ability and subcellular distribution pattern. SCIENCE CHINA-LIFE SCIENCES 2012; 55:933-9. [PMID: 23124793 DOI: 10.1007/s11427-012-4393-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2012] [Accepted: 09/20/2012] [Indexed: 11/24/2022]
Abstract
Influenza A virus NS1 protein has developed two main IFN-antagonizing mechanisms by inhibiting retinoic-acid-inducible gene I (RIG-I) signal transduction, or by suppressing cellular pre-mRNA processing through binding to cleavage and polyadenylation specific factor 30 (CPSF30). However, the precise effects of NS1 on suppressing type I IFN induction have not been well characterized. Here we report that compared with PR/8/34 NS1, which is localized partially in the cytoplasm and has strong IFN-antagonizing ability via specifically inhibiting IFN-β promoter activity, H5N1 NS1 has strikingly different characteristics. It mainly accumulates in the nucleus of transfected cells and exerts rather weak IFN-counteracting ability through suppression of the overall gene expression. The M101I mutation of H5N1 NS1, namely H5-M101I, fully reversed its functions. H5-M101I gained the ability to specifically inhibit IFN-β promoter activity, translocate to the cytoplasm, and release CPSF30. The previously reported NES (nuclear export signal) (residues 138-147) was unable to lead H5N1 NS1 to translocate. This suggests that other residues may serve as a potent NES. Findings indicated that together with leucine-100, methionine-101 enhanced the regional NES. In addition, methionine-101 was the key residue for the NS1-CPSF30 interaction. This study reveals the importance of methionine-101 in the influenza A virus life cycle and may provide valuable information for antiviral strategies.
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Affiliation(s)
- Jin Meng
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
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Abstract
Seasonal flu affects 5–20% of the human population each year. Although mortality rates are typically <0.1% and the pandemic 2009 H1N1 influenza strain has been well contained by vaccination and strict hygiene, particularly virulent pandemic forms have emerged three times in the last century, resulting in millions of deaths. Current vaccine and therapeutic strategies are limited by the ability of the virus to generate variants that evade vaccine-induced immune responses and resist the therapeutic effects of antiviral drugs. Host genetic variations affect immune responses and may induce adverse effects during drug treatment or against vaccines. To develop new, first-in-class therapeutics, new antiviral targets and new chemical entities must be identified in the context of the immunogenomic repertoire of the patient. Since influenza and so many other viruses need to escape innate immunity to become pathogenic, the viral proteins responsible for this, as well as the host cell molecular pathways that lead to the antiviral response, are an excellent potential source of new therapeutic targets within a systems approach against influenza infections.
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Affiliation(s)
- Christian V Forst
- University of Texas Southwestern Medical Center, Department of Clinical Sciences, 5323 Harry Hines Boulevard, Dallas, TX 75390-9066, USA
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Contribution of NS1 effector domain dimerization to influenza A virus replication and virulence. J Virol 2012; 86:13095-8. [PMID: 22993153 DOI: 10.1128/jvi.02237-12] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Conserved tryptophan-187 facilitates homodimerization of the influenza A virus NS1 protein effector domain. We generated a mutant influenza virus strain expressing NS1-W187R to destabilize this self-interaction. NS1-W187R protein exhibited lower double-stranded RNA (dsRNA)-binding activity, showed a temporal redistribution during infection, and was minimally compromised for interferon antagonism. The mutant virus replicated similarly to the wild type in vitro, but it was slightly attenuated for replication in mice, causing notably reduced morbidity and mortality. These data suggest biological relevance for the W187-mediated homotypic interaction of NS1.
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The NS1 protein of influenza A virus interacts with cellular processing bodies and stress granules through RNA-associated protein 55 (RAP55) during virus infection. J Virol 2012; 86:12695-707. [PMID: 22973032 DOI: 10.1128/jvi.00647-12] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The nonstructural protein (NS1) of influenza A virus performs multiple functions in the virus life cycle. Proteomic screening for cellular proteins which interact with NS1 identified the cellular protein RAP55, which is one of the components of cellular processing bodies (P-bodies) and stress granules. To verify whether NS1 interacts with cellular P-bodies, interactions between NS1, RAP55, and other P-body-associated proteins (Ago1, Ago2, and DCP1a) were confirmed using coimmunoprecipitation and cellular colocalization assays. Overexpression of RAP55 induced RAP55-associated stress granule formation and suppressed virus replication. Knockdown of RAP55 with small interfering RNA (siRNA) or expression of a dominant-negative mutant RAP55 protein with defective interaction with P-bodies blocked NS1 colocalization to P-bodies in cells. Expression of NS1 inhibited RAP55 expression and formation of RAP55-associated P-bodies/stress granules. The viral nucleoprotein (NP) was found to be targeted to stress granules in the absence of NS1 but localized to P-bodies when NS1 was coexpressed. Restriction of virus replication via P-bodies occurred in the early phases of infection, as the number of RAP55-associated P-bodies in cells diminished over the course of virus infection. NS1 interaction with RAP55-associated P-bodies/stress granules was associated with RNA binding and mediated via a protein kinase R (PKR)-interacting viral element. Mutations introduced into either RNA binding sites (R38 and K41) or PKR interaction sites (I123, M124, K126, and N127) caused NS1 proteins to lose the ability to interact with RAP55 and to inhibit stress granules. These results reveal an interplay between virus and host during virus replication in which NP is targeted to P-bodies/stress granules while NS1 counteracts this host restriction mechanism.
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