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Garcia G, Irudayam JI, Jeyachandran AV, Dubey S, Chang C, Castillo Cario S, Price N, Arumugam S, Marquez AL, Shah A, Fanaei A, Chakravarty N, Joshi S, Sinha S, French SW, Parcells MS, Ramaiah A, Arumugaswami V. Innate immune pathway modulator screen identifies STING pathway activation as a strategy to inhibit multiple families of arbo and respiratory viruses. Cell Rep Med 2023; 4:101024. [PMID: 37119814 DOI: 10.1016/j.xcrm.2023.101024] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 03/17/2023] [Accepted: 04/07/2023] [Indexed: 05/01/2023]
Abstract
RNA viruses continue to remain a threat for potential pandemics due to their rapid evolution. Potentiating host antiviral pathways to prevent or limit viral infections is a promising strategy. Thus, by testing a library of innate immune agonists targeting pathogen recognition receptors, we observe that Toll-like receptor 3 (TLR3), stimulator of interferon genes (STING), TLR8, and Dectin-1 ligands inhibit arboviruses, Chikungunya virus (CHIKV), West Nile virus, and Zika virus to varying degrees. STING agonists (cAIMP, diABZI, and 2',3'-cGAMP) and Dectin-1 agonist scleroglucan demonstrate the most potent, broad-spectrum antiviral function. Furthermore, STING agonists inhibit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and enterovirus-D68 (EV-D68) infection in cardiomyocytes. Transcriptome analysis reveals that cAIMP treatment rescue cells from CHIKV-induced dysregulation of cell repair, immune, and metabolic pathways. In addition, cAIMP provides protection against CHIKV in a chronic CHIKV-arthritis mouse model. Our study describes innate immune signaling circuits crucial for RNA virus replication and identifies broad-spectrum antivirals effective against multiple families of pandemic potential RNA viruses.
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Affiliation(s)
- Gustavo Garcia
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Joseph Ignatius Irudayam
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Arjit Vijey Jeyachandran
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Swati Dubey
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Christina Chang
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Sebastian Castillo Cario
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Nate Price
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Sathya Arumugam
- Department of Mathematics, Government College Daman, Daman, Dadra and Nagar Haveli and Daman and Diu 396210, India
| | - Angelica L Marquez
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Aayushi Shah
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Amir Fanaei
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Nikhil Chakravarty
- Department of Epidemiology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Shantanu Joshi
- Department of Neurology, University of California, Los Angeles, Los Angeles, CA, USA; Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, USA
| | - Sanjeev Sinha
- All India Institute of Medical Sciences, New Delhi, India
| | - Samuel W French
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA, USA; Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Mark S Parcells
- Department of Animal and Food Sciences, Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Arunachalam Ramaiah
- Tata Institute for Genetics and Society, Center at inStem, Bangalore 560065, India; City of Milwaukee Health Department, Milwaukee, WI 53202, USA.
| | - Vaithilingaraja Arumugaswami
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA, USA; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, USA.
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2
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Garcia G, Irudayam JI, Jeyachandran AV, Dubey S, Chang C, Cario SC, Price N, Arumugam S, Marquez AL, Shah A, Fanaei A, Chakravarty N, Joshi S, Sinha S, French SW, Parcells M, Ramaiah A, Arumugaswami V. Broad-spectrum antiviral inhibitors targeting pandemic potential RNA viruses. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.19.524824. [PMID: 36711787 PMCID: PMC9882367 DOI: 10.1101/2023.01.19.524824] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
RNA viruses continue to remain a clear and present threat for potential pandemics due to their rapid evolution. To mitigate their impact, we urgently require antiviral agents that can inhibit multiple families of disease-causing viruses, such as arthropod-borne and respiratory pathogens. Potentiating host antiviral pathways can prevent or limit viral infections before escalating into a major outbreak. Therefore, it is critical to identify broad-spectrum antiviral agents. We have tested a small library of innate immune agonists targeting pathogen recognition receptors, including TLRs, STING, NOD, Dectin and cytosolic DNA or RNA sensors. We observed that TLR3, STING, TLR8 and Dectin-1 ligands inhibited arboviruses, Chikungunya virus (CHIKV), West Nile virus (WNV) and Zika virus, to varying degrees. Cyclic dinucleotide (CDN) STING agonists, such as cAIMP, diABZI, and 2',3'-cGAMP, and Dectin-1 agonist scleroglucan, demonstrated the most potent, broad-spectrum antiviral function. Comparative transcriptome analysis revealed that CHIKV-infected cells had larger number of differentially expressed genes than of WNV and ZIKV. Furthermore, gene expression analysis showed that cAIMP treatment rescued cells from CHIKV-induced dysregulation of cell repair, immune, and metabolic pathways. In addition, cAIMP provided protection against CHIKV in a CHIKV-arthritis mouse model. Cardioprotective effects of synthetic STING ligands against CHIKV, WNV, SARS-CoV-2 and enterovirus D68 (EV-D68) infections were demonstrated using human cardiomyocytes. Interestingly, the direct-acting antiviral drug remdesivir, a nucleoside analogue, was not effective against CHIKV and WNV, but exhibited potent antiviral effects against SARS-CoV-2, RSV (respiratory syncytial virus), and EV-D68. Our study identifies broad-spectrum antivirals effective against multiple families of pandemic potential RNA viruses, which can be rapidly deployed to prevent or mitigate future pandemics.
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Affiliation(s)
- Gustavo Garcia
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Joseph Ignatius Irudayam
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Arjit Vijay Jeyachandran
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Swati Dubey
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Christina Chang
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Sebastian Castillo Cario
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Nate Price
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Sathya Arumugam
- Department of Mathematics, Government College Daman, U.T of DNH & DD, India
| | - Angelica L. Marquez
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Aayushi Shah
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Amir Fanaei
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Nikhil Chakravarty
- Department of Epidemiology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Shantanu Joshi
- Department of Neurology, University of California, Los Angeles, CA, USA
| | - Sanjeev Sinha
- All India Institute of Medical Sciences, New Delhi, India
| | - Samuel W. French
- Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, CA 90095, USA
| | - Mark Parcells
- Department of Animal and Food Sciences, Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Arunachalam Ramaiah
- Tata Institute for Genetics and Society, Center at inStem, Bangalore 560065, India,City of Milwaukee Health Department, Milwaukee, WI 53202, USA.,To whom correspondence should be addressed: Vaithilingaraja Arumugaswami, DVM, PhD., 10833 Le Conte Ave, CHS B2-049A, Los Angeles, California 90095, Phone: (310) 794-9568, , Arunachalam Ramaiah, MS, PhD., 841 N. Broadway, 2nd Floor, Milwaukee, Wisconsin 53202,
| | - Vaithilingaraja Arumugaswami
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA.,Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA, USA.,California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, USA.,Lead Contact,To whom correspondence should be addressed: Vaithilingaraja Arumugaswami, DVM, PhD., 10833 Le Conte Ave, CHS B2-049A, Los Angeles, California 90095, Phone: (310) 794-9568, , Arunachalam Ramaiah, MS, PhD., 841 N. Broadway, 2nd Floor, Milwaukee, Wisconsin 53202,
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Sathanantham P, Zhao W, He G, Murray A, Fenech E, Diaz A, Schuldiner M, Wang X. A conserved viral amphipathic helix governs the replication site-specific membrane association. PLoS Pathog 2022; 18:e1010752. [PMID: 36048900 PMCID: PMC9473614 DOI: 10.1371/journal.ppat.1010752] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 09/14/2022] [Accepted: 07/19/2022] [Indexed: 11/18/2022] Open
Abstract
Positive-strand RNA viruses assemble their viral replication complexes (VRCs) on specific host organelle membranes, yet it is unclear how viral replication proteins recognize and what motifs or domains in viral replication proteins determine their destinations. We show here that an amphipathic helix, helix B in replication protein 1a of brome mosaic virus (BMV), is necessary for 1a’s localization to the nuclear endoplasmic reticulum (ER) membrane where BMV assembles its VRCs. Helix B is also sufficient to target soluble proteins to the nuclear ER membrane in yeast and plant cells. We further show that an equivalent helix in several plant- and human-infecting viruses of the Alsuviricetes class targets fluorescent proteins to the organelle membranes where they form their VRCs, including ER, vacuole, and Golgi membranes. Our work reveals a conserved helix that governs the localization of VRCs among a group of viruses and points to a possible target for developing broad-spectrum antiviral strategies. Positive-strand RNA viruses [(+)RNA viruses] are the largest viral class that include numerous pathogens causing important diseases in humans, animals, and plants. During their infections, (+)RNA viruses assemble their viral replication complexes (VRCs), where they multiply themselves, at specific organelle membranes. An initial step to form VRCs is to target viral replication proteins to the designated organelle membranes. For brome mosaic virus (BMV), its replication protein 1a is responsible for the VRC formation at the nuclear endoplasmic reticulum (ER) membrane. We show that an amphipathic alpha-helix, helix B, in BMV 1a is necessary for the association of BMV 1a with the nuclear ER membrane and for BMV genome amplification. In addition, Helix B is sufficient to target several soluble proteins to the nuclear ER membrane in yeast and plant cells. BMV belongs to the Alsuviricetes class that includes viruses infecting humans, animals, and plants. We further show that the helix B across members of the Alsuviricetes class is sufficient to target fluorescence proteins to the designated organelle membranes. Our results reveal a conserved feature among a group of viruses in governing the associations with replication site-specific organelle membranes and point to a target to develop broad-spectrum antivirals.
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Affiliation(s)
- Preethi Sathanantham
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Wenhao Zhao
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Nanjing, China
| | - Guijuan He
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Austin Murray
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Emma Fenech
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Arturo Diaz
- Department of Biology, La Sierra University, Riverside, California, United States of America
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Xiaofeng Wang
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
- * E-mail:
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Javaid A, Ijaz A, Ashfaq UA, Arshad M, Irshad S, Saif S. An overview of chikungunya virus molecular biology, epidemiology, pathogenesis, treatment and prevention strategies. Future Virol 2022. [DOI: 10.2217/fvl-2019-0166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The chikungunya virus (CHIKV) causes a devastating musculoskeletal inflammatory disease with symptoms of headache, rash, polyarthralgia, fever and myalgia. CHIKV has appeared intermittently around the world and in different ecological zones of Pakistan. Aedes mosquito species are the main vectors of CHIKV transmission and cause high disease rates in the urban transmission cycle. Even though the CHIKV is responsible for many cases of disease, no authorized antibodies or antiviral treatments are available, and prevention is the primary countermeasure. This review describes an update on CHIKV molecular biology, replication cycle, epidemiology, ecological factors, clinical manifestations and treatment and suggests a way forward to control and prevent this infection strategically in the future.
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Affiliation(s)
- Anam Javaid
- Department of Bioinformatics & Biotechnology, Government College University, Faisalabad, Pakistan
| | - Aroosa Ijaz
- Department of Bioinformatics & Biotechnology, Government College University, Faisalabad, Pakistan
| | - Usman Ali Ashfaq
- Department of Bioinformatics & Biotechnology, Government College University, Faisalabad, Pakistan
| | - Maham Arshad
- Department of Bioinformatics & Biotechnology, Government College University, Faisalabad, Pakistan
| | - Shakeel Irshad
- Department of Bioinformatics & Biotechnology, Government College University, Faisalabad, Pakistan
| | - Saira Saif
- Department of Bioinformatics & Biotechnology, Government College University, Faisalabad, Pakistan
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Constant LEC, Rajsfus BF, Carneiro PH, Sisnande T, Mohana-Borges R, Allonso D. Overview on Chikungunya Virus Infection: From Epidemiology to State-of-the-Art Experimental Models. Front Microbiol 2021; 12:744164. [PMID: 34675908 PMCID: PMC8524093 DOI: 10.3389/fmicb.2021.744164] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/07/2021] [Indexed: 12/27/2022] Open
Abstract
Chikungunya virus (CHIKV) is currently one of the most relevant arboviruses to public health. It is a member of the Togaviridae family and alphavirus genus and causes an arthritogenic disease known as chikungunya fever (CHIKF). It is characterized by a multifaceted disease, which is distinguished from other arbovirus infections by the intense and debilitating arthralgia that can last for months or years in some individuals. Despite the great social and economic burden caused by CHIKV infection, there is no vaccine or specific antiviral drugs currently available. Recent outbreaks have shown a change in the severity profile of the disease in which atypical and severe manifestation lead to hundreds of deaths, reinforcing the necessity to understand the replication and pathogenesis processes. CHIKF is a complex disease resultant from the infection of a plethora of cell types. Although there are several in vivo models for studying CHIKV infection, none of them reproduces integrally the disease signature observed in humans, which is a challenge for vaccine and drug development. Therefore, understanding the potentials and limitations of the state-of-the-art experimental models is imperative to advance in the field. In this context, the present review outlines the present knowledge on CHIKV epidemiology, replication, pathogenesis, and immunity and also brings a critical perspective on the current in vitro and in vivo state-of-the-art experimental models of CHIKF.
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Affiliation(s)
- Larissa E. C. Constant
- Departamento de Biotecnologia Farmacêutica, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Laboratório de Biotecnologia e Bioengenharia Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Bia F. Rajsfus
- Departamento de Biotecnologia Farmacêutica, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Laboratório de Biotecnologia e Bioengenharia Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Pedro H. Carneiro
- Laboratório de Biotecnologia e Bioengenharia Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Tháyna Sisnande
- Laboratório de Biotecnologia e Bioengenharia Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Ronaldo Mohana-Borges
- Laboratório de Biotecnologia e Bioengenharia Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Diego Allonso
- Departamento de Biotecnologia Farmacêutica, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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Silva LR, Rodrigues ÉEDS, Taniele-Silva J, Anderson L, Araújo-Júnior JXD, Bassi ÊJ, Silva-Júnior EFD. Targeting Chikungunya Virus Entry: alternatives for new inhibitors in drug discovery. Curr Med Chem 2021; 29:612-634. [PMID: 34165405 DOI: 10.2174/0929867328666210623165005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 04/06/2021] [Accepted: 05/11/2021] [Indexed: 11/22/2022]
Abstract
Chikungunya virus (CHIKV) is an Alphavirus (Togaviridae) responsible for Chikungunya fever (CHIKF) that is mainly characterized by a severe polyarthralgia, in which it is transmitted by the bite of infected Aedes aegypti and Ae. albopictus mosquitoes. Nowadays, there no licensed vaccines or approved drugs to specifically treat this viral disease. Structural viral proteins participate in key steps of its replication cycle, such as viral entry, membrane fusion, nucleocapsid assembly, and virus budding. In this context, envelope E3-E2-E1 glycoproteins complex could be targeted for designing new drug candidates. In this review, aspects of the CHIKV entry process are discussed to provide insights to assist the drug discovery process. Moreover, several natural, nature-based and synthetic compounds, as well as repurposed drugs and virtual screening, are also explored as alternatives for developing CHIKV entry inhibitors. Finally, we provided a complimentary analysis of studies involving inhibitors that were not explored by in silico methods. Based on this, Phe118, Val179, and Lys181 were found to be the most frequent residues, being present in 89.6, 82.7, and 93.1% of complexes, respectively. Lastly, some chemical aspects associated with interactions of these inhibitors and mature envelope E3-E2-E1 glycoproteins' complex were discussed to provide data for scientists worldwide, supporting their search for new inhibitors against this emerging arbovirus.
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Affiliation(s)
- Leandro Rocha Silva
- Chemistry and Biotechnology Institute, Federal University of Alagoas, Campus A.C. Simões, Lourival Melo Mota Avenue, Maceió 57072-970, Brazil
| | - Érica Erlanny da Silva Rodrigues
- Chemistry and Biotechnology Institute, Federal University of Alagoas, Campus A.C. Simões, Lourival Melo Mota Avenue, Maceió 57072-970, Brazil
| | - Jamile Taniele-Silva
- IMUNOREG - Immunoregulation Research Group, Laboratory of Research in Virology and Immunology, Institute of Biological Sciences and Health, Federal University of Alagoas, Campus AC. Simões, Lourival Melo Mota Avenue, Maceió 57072-970, Brazil
| | - Letícia Anderson
- IMUNOREG - Immunoregulation Research Group, Laboratory of Research in Virology and Immunology, Institute of Biological Sciences and Health, Federal University of Alagoas, Campus AC. Simões, Lourival Melo Mota Avenue, Maceió 57072-970, Brazil
| | - João Xavier de Araújo-Júnior
- Chemistry and Biotechnology Institute, Federal University of Alagoas, Campus A.C. Simões, Lourival Melo Mota Avenue, Maceió 57072-970, Brazil
| | - Ênio José Bassi
- IMUNOREG - Immunoregulation Research Group, Laboratory of Research in Virology and Immunology, Institute of Biological Sciences and Health, Federal University of Alagoas, Campus AC. Simões, Lourival Melo Mota Avenue, Maceió 57072-970, Brazil
| | - Edeildo F da Silva-Júnior
- Chemistry and Biotechnology Institute, Federal University of Alagoas, Campus A.C. Simões, Lourival Melo Mota Avenue, Maceió 57072-970, Brazil
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Structural Insights into the Mechanisms of Action of Functionally Distinct Classes of Chikungunya Virus Nonstructural Protein 1 Inhibitors. Antimicrob Agents Chemother 2021; 65:e0256620. [PMID: 33875421 PMCID: PMC8218635 DOI: 10.1128/aac.02566-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Chikungunya virus (CHIKV) nonstructural protein 1 (nsP1) harbors the methyltransferase (MTase) and guanylyltransferase (GTase) activities needed for viral RNA capping and represents a promising antiviral drug target. We compared the antiviral efficacies of nsP1 inhibitors belonging to the MADTP, CHVB, and FHNA series (6′-fluoro-homoneplanocin A [FHNA], its 3′-keto form, and 6′-β-fluoro-homoaristeromycin). Cell-based phenotypic cross-resistance assays revealed that the CHVB and MADTP series had similar modes of action that differed from that of the FHNA series. In biochemical assays with purified Semliki Forest virus and CHIKV nsP1, CHVB compounds strongly inhibited MTase and GTase activities, while MADTP-372 had a moderate inhibitory effect. FHNA did not directly inhibit the enzymatic activity of CHIKV nsP1. The first-of-their-kind molecular-docking studies with the cryo-electron microscopy (cryo-EM) structure of CHIKV nsP1, which is assembled into a dodecameric ring, revealed that the MADTP and CHVB series bind at the S-adenosylmethionine (SAM)-binding site in the capping domain, where they would function as competitive or noncompetitive inhibitors. The FHNA series was predicted to bind at the secondary binding pocket in the ring-aperture membrane-binding and oligomerization (RAMBO) domain, potentially interfering with the membrane binding and oligomerization of nsP1. Our cell-based and enzymatic assays, in combination with molecular docking and mapping of compound resistance mutations to the nsP1 structure, allowed us to group nsP1 inhibitors into functionally distinct classes. This study identified druggable pockets in the nsP1 dodecameric structure and provides a basis for the rational design, optimization, and combination of inhibitors of this unique and promising antiviral drug target.
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Abdullah N, Ahemad N, Aliazis K, Khairat JE, Lee TC, Abdul Ahmad SA, Adnan NAA, Macha NO, Hassan SS. The Putative Roles and Functions of Indel, Repetition and Duplication Events in Alphavirus Non-Structural Protein 3 Hypervariable Domain (nsP3 HVD) in Evolution, Viability and Re-Emergence. Viruses 2021; 13:v13061021. [PMID: 34071712 PMCID: PMC8228767 DOI: 10.3390/v13061021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 04/30/2021] [Accepted: 05/04/2021] [Indexed: 11/23/2022] Open
Abstract
Alphavirus non-structural proteins 1–4 (nsP1, nsP2, nsP3, and nsP4) are known to be crucial for alphavirus RNA replication and translation. To date, nsP3 has been demonstrated to mediate many virus–host protein–protein interactions in several fundamental alphavirus mechanisms, particularly during the early stages of replication. However, the molecular pathways and proteins networks underlying these mechanisms remain poorly described. This is due to the low genetic sequence homology of the nsP3 protein among the alphavirus species, especially at its 3′ C-terminal domain, the hypervariable domain (HVD). Moreover, the nsP3 HVD is almost or completely intrinsically disordered and has a poor ability to form secondary structures. Evolution in the nsP3 HVD region allows the alphavirus to adapt to vertebrate and insect hosts. This review focuses on the putative roles and functions of indel, repetition, and duplication events that have occurred in the alphavirus nsP3 HVD, including characterization of the differences and their implications for specificity in the context of virus–host interactions in fundamental alphavirus mechanisms, which have thus directly facilitated the evolution, adaptation, viability, and re-emergence of these viruses.
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Affiliation(s)
- Nurshariza Abdullah
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway 47500, Selangor, Malaysia; (N.A.); (N.A.A.A.); (N.O.M.)
| | - Nafees Ahemad
- School of Pharmacy, Monash University Malaysia, Bandar Sunway 47500, Selangor, Malaysia;
- Infectious Diseases and Health Cluster, Tropical Medicine and Biology Platform, Monash University Malaysia, Bandar Sunway 47500, Selangor, Malaysia
| | - Konstantinos Aliazis
- Institute of Immunology and Immunotherapy, Centre for Liver and Gastrointestinal Research, University of Birmingham, Birmingham B15 2TT, UK;
| | - Jasmine Elanie Khairat
- Institute of Biological Sciences, Faculty of Science, University Malaya, Kuala Lumpur 50603, Malaysia;
| | - Thong Chuan Lee
- Faculty of Industrial Sciences & Technology, University Malaysia Pahang, Lebuhraya Tun Razak, Gambang, Kuantan 26300, Pahang, Malaysia;
| | - Siti Aisyah Abdul Ahmad
- Immunogenetic Unit, Allergy and Immunology Research Center, Institute for Medical Research, Ministry of Health Malaysia, Shah Alam 40170, Selangor, Malaysia;
| | - Nur Amelia Azreen Adnan
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway 47500, Selangor, Malaysia; (N.A.); (N.A.A.A.); (N.O.M.)
| | - Nur Omar Macha
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway 47500, Selangor, Malaysia; (N.A.); (N.A.A.A.); (N.O.M.)
| | - Sharifah Syed Hassan
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway 47500, Selangor, Malaysia; (N.A.); (N.A.A.A.); (N.O.M.)
- Infectious Diseases and Health Cluster, Tropical Medicine and Biology Platform, Monash University Malaysia, Bandar Sunway 47500, Selangor, Malaysia
- Correspondence: ; Tel.: +60-3-5514-6340
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Zhang K, Law YS, Law MCY, Tan YB, Wirawan M, Luo D. Structural insights into viral RNA capping and plasma membrane targeting by Chikungunya virus nonstructural protein 1. Cell Host Microbe 2021; 29:757-764.e3. [DOI: 10.1016/j.chom.2021.02.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 02/10/2021] [Accepted: 02/22/2021] [Indexed: 01/30/2023]
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Varkey J, Zhang J, Kim J, George G, He G, Belov G, Langen R, Wang X. An Amphipathic Alpha-Helix Domain from Poliovirus 2C Protein Tubulate Lipid Vesicles. Viruses 2020; 12:v12121466. [PMID: 33353144 PMCID: PMC7766222 DOI: 10.3390/v12121466] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 12/15/2020] [Accepted: 12/15/2020] [Indexed: 02/01/2023] Open
Abstract
Positive-strand RNA viruses universally remodel host intracellular membranes to form membrane-bound viral replication complexes, where viral offspring RNAs are synthesized. In the majority of cases, viral replication proteins are targeted to and play critical roles in the modulation of the designated organelle membranes. Many viral replication proteins do not have transmembrane domains, but contain single or multiple amphipathic alpha-helices. It has been conventionally recognized that these helices serve as an anchor for viral replication protein to be associated with membranes. We report here that a peptide representing the amphipathic α-helix at the N-terminus of the poliovirus 2C protein not only binds to liposomes, but also remodels spherical liposomes into tubules. The membrane remodeling ability of this amphipathic alpha-helix is similar to that recognized in other amphipathic alpha-helices from cellular proteins involved in membrane remodeling, such as BAR domain proteins. Mutations affecting the hydrophobic face of the amphipathic alpha-helix severely compromised membrane remodeling of vesicles with physiologically relevant phospholipid composition. These mutations also affected the ability of poliovirus to form plaques indicative of reduced viral replication, further underscoring the importance of membrane remodeling by the amphipathic alpha-helix in possible relation to the formation of viral replication complexes.
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Affiliation(s)
- Jobin Varkey
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA; (J.V.); (G.G.)
| | - Jiantao Zhang
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA 24061, USA; (J.Z.); (G.H.)
| | - Junghyun Kim
- Virginia-Maryland College of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA; (J.K.); (G.B.)
| | - Gincy George
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA; (J.V.); (G.G.)
| | - Guijuan He
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA 24061, USA; (J.Z.); (G.H.)
| | - George Belov
- Virginia-Maryland College of Veterinary Medicine, University of Maryland, College Park, MD 20742, USA; (J.K.); (G.B.)
| | - Ralf Langen
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA; (J.V.); (G.G.)
- Correspondence: (R.L.); (X.W.); Tel.: +1-323-442-1323 (R.L.); +1-540-231-1868 (X.W.)
| | - Xiaofeng Wang
- School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA 24061, USA; (J.Z.); (G.H.)
- Correspondence: (R.L.); (X.W.); Tel.: +1-323-442-1323 (R.L.); +1-540-231-1868 (X.W.)
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11
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Hucke FIL, Bugert JJ. Current and Promising Antivirals Against Chikungunya Virus. Front Public Health 2020; 8:618624. [PMID: 33384981 PMCID: PMC7769948 DOI: 10.3389/fpubh.2020.618624] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 11/19/2020] [Indexed: 12/21/2022] Open
Abstract
Chikungunya virus (CHIKV) is the causative agent of chikungunya fever (CHIKF) and is categorized as a(n) (re)emerging arbovirus. CHIKV has repeatedly been responsible for outbreaks that caused serious economic and public health problems in the affected countries. To date, no vaccine or specific antiviral therapies are available. This review gives a summary on current antivirals that have been investigated as potential therapeutics against CHIKF. The mode of action as well as possible compound targets (viral and host targets) are being addressed. This review hopes to provide critical information on the in vitro efficacies of various compounds and might help researchers in their considerations for future experiments.
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12
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Webb LG, Veloz J, Pintado-Silva J, Zhu T, Rangel MV, Mutetwa T, Zhang L, Bernal-Rubio D, Figueroa D, Carrau L, Fenutria R, Potla U, Reid SP, Yount JS, Stapleford KA, Aguirre S, Fernandez-Sesma A. Chikungunya virus antagonizes cGAS-STING mediated type-I interferon responses by degrading cGAS. PLoS Pathog 2020; 16:e1008999. [PMID: 33057424 PMCID: PMC7591055 DOI: 10.1371/journal.ppat.1008999] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 10/27/2020] [Accepted: 09/21/2020] [Indexed: 12/24/2022] Open
Abstract
Chikungunya virus (CHIKV) is a mosquito-borne alphavirus known to cause epidemics resulting in predominantly symptomatic infections, which in rare cases cause long term debilitating arthritis and arthralgia. Significant progress has been made in understanding the roles of canonical RNA sensing pathways in the host recognition of CHIKV; however, less is known regarding antagonism of CHIKV by cytosolic DNA sensing pathways like that of cyclic GMP-AMP synthase (cGAS) and Stimulator of Interferon Genes (STING). With the use of cGAS or STING null cells we demonstrate that the pathway restricts CHIKV replication in fibroblasts and immune cells. We show that DNA accumulates in the cytoplasm of infected cells and that CHIKV blocks DNA dependent IFN-β transcription. This antagonism of DNA sensing is via an early autophagy-mediated degradation of cGAS and expression of the CHIKV capsid protein is sufficient to induce cGAS degradation. Furthermore, we identify an interaction of CHIKV nsP1 with STING and map the interaction to 23 residues in the cytosolic loop of the adaptor protein. This interaction stabilizes the viral protein and increases the level of palmitoylated nsP1 in cells. Together, this work supports previous publications highlighting the relevance of the cGAS-STING pathway in the early detection of (+)ssRNA viruses and provides direct evidence that CHIKV interacts with and antagonizes cGAS-STING signaling.
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Affiliation(s)
- L. G. Webb
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
- The Graduate School of Biomedical Sciences at Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - J. Veloz
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
- The Graduate School of Biomedical Sciences at Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - J. Pintado-Silva
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
- The Graduate School of Biomedical Sciences at Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - T. Zhu
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
- The Graduate School of Biomedical Sciences at Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - M. V. Rangel
- Department of Microbiology, New York University School of Medicine, New York, NY, United States of America
| | - T. Mutetwa
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
- The Graduate School of Biomedical Sciences at Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - L. Zhang
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States of America
- Infectious Diseases Institute, The Ohio State University, Columbus, OH, United States of America
| | - D. Bernal-Rubio
- The Graduate School of Biomedical Sciences at Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - D. Figueroa
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
- The Graduate School of Biomedical Sciences at Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - L. Carrau
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - R. Fenutria
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - U. Potla
- The Graduate School of Biomedical Sciences at Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - St. P. Reid
- Department of Pathology & Microbiology, University of Nebraska Medical Center, Omaha, NE, United States of America
| | - J. S. Yount
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States of America
- Infectious Diseases Institute, The Ohio State University, Columbus, OH, United States of America
| | - K. A. Stapleford
- Department of Microbiology, New York University School of Medicine, New York, NY, United States of America
| | - S. Aguirre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | - A. Fernandez-Sesma
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
- The Graduate School of Biomedical Sciences at Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
- Department of Medicine, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
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Palmitoylated Cysteines in Chikungunya Virus nsP1 Are Critical for Targeting to Cholesterol-Rich Plasma Membrane Microdomains with Functional Consequences for Viral Genome Replication. J Virol 2020; 94:JVI.02183-19. [PMID: 32132240 DOI: 10.1128/jvi.02183-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Accepted: 02/28/2020] [Indexed: 12/16/2022] Open
Abstract
In mammalian cells, alphavirus replication complexes are anchored to the plasma membrane. This interaction with lipid bilayers is mediated through the viral methyl/guanylyltransferase nsP1 and reinforced by palmitoylation of cysteine residue(s) in the C-terminal region of this protein. Lipid content of membranes supporting nsP1 anchoring remains poorly studied. Here, we explore the membrane binding capacity of nsP1 with regard to cholesterol. Using the medically important chikungunya virus (CHIKV) as a model, we report that nsP1 cosegregates with cholesterol-rich detergent-resistant membrane microdomains (DRMs), also called lipid rafts. In search for the critical factor for cholesterol partitioning, we identify nsP1 palmitoylated cysteines as major players in this process. In cells infected with CHIKV or transfected with CHIKV trans-replicase plasmids, nsP1, together with the other nonstructural proteins, are detected in DRMs. While the functional importance of CHIKV nsP1 preference for cholesterol-rich membrane domains remains to be determined, we observed that U18666A- and imipramine-induced sequestration of cholesterol in late endosomes redirected nsP1 to these compartments and simultaneously dramatically decreased CHIKV genome replication. A parallel study of Sindbis virus (SINV) revealed that nsP1 from this divergent alphavirus displays a low affinity for cholesterol and only moderately segregates with DRMs. Behaviors of CHIKV and SINV with regard to cholesterol, therefore, match with the previously reported differences in the requirement for nsP1 palmitoylation, which is dispensable for SINV but strictly required for CHIKV replication. Altogether, this study highlights the functional importance of nsP1 segregation with DRMs and provides new insight into the functional role of nsP1 palmitoylated cysteines during alphavirus replication.IMPORTANCE Functional alphavirus replication complexes are anchored to the host cell membranes through the interaction of nsP1 with the lipid bilayers. In this work, we investigate the importance of cholesterol for such an association. We show that nsP1 has affinity for cholesterol-rich membrane microdomains formed at the plasma membrane and identify conserved palmitoylated cysteine(s) in nsP1 as the key determinant for cholesterol affinity. We demonstrate that drug-induced cholesterol sequestration in late endosomes not only redirects nsP1 to this compartment but also dramatically decreases genome replication, suggesting the functional importance of nsP1 targeting to cholesterol-rich plasma membrane microdomains. Finally, we show evidence that nsP1 from chikungunya and Sindbis viruses displays different sensitivity to cholesterol sequestering agents that parallel with their difference in the requirement for nsP1 palmitoylation for replication. This research, therefore, gives new insight into the functional role of palmitoylated cysteines in nsP1 for the assembly of functional alphavirus replication complexes in their mammalian host.
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14
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Gottipati K, Woodson M, Choi KH. Membrane binding and rearrangement by chikungunya virus capping enzyme nsP1. Virology 2020; 544:31-41. [PMID: 32174512 PMCID: PMC7103501 DOI: 10.1016/j.virol.2020.02.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 02/17/2020] [Accepted: 02/23/2020] [Indexed: 01/20/2023]
Abstract
Alphavirus genome replication is carried out by the viral replication complex inside modified membrane structures called spherules. The viral nonstructural protein 1 (nsP1) is the only membrane-associated protein that anchors the replication complex to the cellular membranes. Although an internal amphipathic helix of nsP1 is critical for membrane association, the mechanism of nsP1 interaction with membranes and subsequent membrane reorganization is not well understood. We studied the membrane interaction of chikungunya virus (CHIKV) nsP1 and show that both the CHIKV nsP1 protein and the amphipathic peptide specifically bind to negatively charged phospholipid vesicles. Using cryo-electron microscopy, we further show that nsP1 forms a contiguous coat on lipid vesicles and induces structural reorganization, while the amphipathic peptide alone failed to deform the membrane bilayer. This suggests that although amphipathic helix of nsP1 is required for initial membrane binding, the remaining cytoplasmic domain of nsP1 is involved in the subsequent membrane reorganization.
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Affiliation(s)
- Keerthi Gottipati
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, USA.
| | - Michael Woodson
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, USA
| | - Kyung H Choi
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, USA.
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6'-β-Fluoro-Homoaristeromycin and 6'-Fluoro-Homoneplanocin A Are Potent Inhibitors of Chikungunya Virus Replication through Their Direct Effect on Viral Nonstructural Protein 1. Antimicrob Agents Chemother 2020; 64:AAC.02532-19. [PMID: 31964798 PMCID: PMC7179274 DOI: 10.1128/aac.02532-19] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 01/17/2020] [Indexed: 12/23/2022] Open
Abstract
Alphaviruses are arthropod-borne, positive-stranded RNA viruses capable of causing severe disease with high morbidity. Chikungunya virus (CHIKV) is an alphavirus that causes a febrile illness which can progress into chronic arthralgia. The current lack of vaccines and specific treatment for CHIKV infection underscores the need to develop new therapeutic interventions. To discover new antiviral agents, we performed a compound screen in cell culture-based infection models and identified two carbocyclic adenosine analogues, 6′-β-fluoro-homoaristeromycin (FHA) and 6′-fluoro-homoneplanocin A (FHNA), that displayed potent activity against CHIKV and Semliki Forest virus (SFV) with 50% effective concentrations in the nanomolar range at nontoxic concentrations. Alphaviruses are arthropod-borne, positive-stranded RNA viruses capable of causing severe disease with high morbidity. Chikungunya virus (CHIKV) is an alphavirus that causes a febrile illness which can progress into chronic arthralgia. The current lack of vaccines and specific treatment for CHIKV infection underscores the need to develop new therapeutic interventions. To discover new antiviral agents, we performed a compound screen in cell culture-based infection models and identified two carbocyclic adenosine analogues, 6′-β-fluoro-homoaristeromycin (FHA) and 6′-fluoro-homoneplanocin A (FHNA), that displayed potent activity against CHIKV and Semliki Forest virus (SFV) with 50% effective concentrations in the nanomolar range at nontoxic concentrations. The compounds, designed as inhibitors of the host enzyme S-adenosylhomocysteine (SAH) hydrolase, impeded postentry steps in CHIKV and SFV replication. Selection of FHNA-resistant mutants and reverse genetics studies demonstrated that the combination of mutations G230R and K299E in CHIKV nonstructural protein 1 (nsP1) conferred resistance to the compounds. Enzymatic assays with purified wild-type (wt) SFV nsP1 suggested that an oxidized (3′-keto) form, rather than FHNA itself, directly inhibited the MTase activity, while a mutant protein with the K231R and K299E substitutions was insensitive to the compound. Both wt nsP1 and the resistant mutant were equally sensitive to the inhibitory effect of SAH. Our combined data suggest that FHA and FHNA inhibit CHIKV and SFV replication by directly targeting the MTase activity of nsP1, rather than through an indirect effect on host SAH hydrolase. The high potency and selectivity of these novel alphavirus mRNA capping inhibitors warrant further preclinical investigation of these compounds.
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16
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Newase P, More A, Patil J, Patil P, Jadhav S, Alagarasu K, Shah P, Parashar D, Cherian SS. Chikungunya phylogeography reveals persistent global transmissions of the Indian Ocean Lineage from India in association with mutational fitness. INFECTION GENETICS AND EVOLUTION 2020; 82:104289. [PMID: 32198074 DOI: 10.1016/j.meegid.2020.104289] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 02/13/2020] [Accepted: 03/13/2020] [Indexed: 11/25/2022]
Abstract
Since the resurgence of chikungunya virus (CHIKV) in India in 2005, the Indian subcontinent sublineage of the Indian Ocean lineage (IOL) has continued transmission in India and also radiation from India causing additional outbreaks in surrounding countries. This study was undertaken for an in-depth understanding of the evolutionary dynamics of the IOL, the global transmission routes in the Indian context and possible association with mutational fitness. The whole genome sequencing of Indian isolates representing CHIKV outbreaks (2014-2018) from selected States of India was carried out, followed by phylogeography analysis of the IOL using the Bayesian Markov chain Monte Carlo method and selection pressure analysis. Phylogeography analysis of IOL strains revealed indigenous evolution in India at least at three time points, with specific mutations that conferred viral fitness in the Aedes vector species. Further dispersal of the strains from India was noted to neighbouring and distant countries with multiple exportations to Sri Lanka, Bangladesh and China. The study reveals India as an endemic reservoir for CHIKV and persistent global transmissions from India. Though natural selection does not appear to play a major role in establishment of the IOL, sustainable efforts towards vector control can help address the issues.
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Affiliation(s)
- Priyanka Newase
- Dengue & Chikungunya Group, ICMR-National Institute of Virology, Dr. Ambedkar Road, Pune 411001, India; Bioinformatics & Data Management Group, ICMR-National Institute of Virology, Dr. Ambedkar Road, Pune 411001, India
| | - Ashwini More
- Dengue & Chikungunya Group, ICMR-National Institute of Virology, Dr. Ambedkar Road, Pune 411001, India
| | - Jayashri Patil
- Dengue & Chikungunya Group, ICMR-National Institute of Virology, Dr. Ambedkar Road, Pune 411001, India
| | - Poonam Patil
- Dengue & Chikungunya Group, ICMR-National Institute of Virology, Dr. Ambedkar Road, Pune 411001, India
| | - Santosh Jadhav
- Bioinformatics & Data Management Group, ICMR-National Institute of Virology, Dr. Ambedkar Road, Pune 411001, India
| | - Kalichamy Alagarasu
- Dengue & Chikungunya Group, ICMR-National Institute of Virology, Dr. Ambedkar Road, Pune 411001, India
| | - Paresh Shah
- Dengue & Chikungunya Group, ICMR-National Institute of Virology, Dr. Ambedkar Road, Pune 411001, India
| | - Deepti Parashar
- Dengue & Chikungunya Group, ICMR-National Institute of Virology, Dr. Ambedkar Road, Pune 411001, India
| | - Sarah S Cherian
- Bioinformatics & Data Management Group, ICMR-National Institute of Virology, Dr. Ambedkar Road, Pune 411001, India.
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Tomar S, Mahajan S, Kumar R. Advances in structure-assisted antiviral discovery for animal viral diseases. GENOMICS AND BIOTECHNOLOGICAL ADVANCES IN VETERINARY, POULTRY, AND FISHERIES 2020. [PMCID: PMC7149589 DOI: 10.1016/b978-0-12-816352-8.00019-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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18
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Design and Use of Chikungunya Virus Replication Templates Utilizing Mammalian and Mosquito RNA Polymerase I-Mediated Transcription. J Virol 2019; 93:JVI.00794-19. [PMID: 31217251 DOI: 10.1128/jvi.00794-19] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 06/18/2019] [Indexed: 01/20/2023] Open
Abstract
Chikungunya virus (CHIKV) is a mosquito-borne alphavirus. It has a positive-sense RNA genome that also serves as the mRNA for four nonstructural proteins (nsPs) representing subunits of the viral replicase. Coupling of nsP and RNA synthesis complicates analysis of viral RNA replication. We developed trans-replication systems, where production of replication-competent RNA and expression of viral replicase are uncoupled. Mammalian and mosquito RNA polymerase I promoters were used to produce noncapped RNA templates, which are poorly translated relative to CHIKV replicase-generated capped RNAs. It was found that, in human cells, constructs driven by RNA polymerase I promoters of human and Chinese hamster origin performed equally well. In contrast, RNA polymerase I promoters from Aedes mosquitoes exhibited strong species specificity. In both mammalian and mosquito cells, novel trans-replicase assays had exceptional sensitivity, with up to 105-fold higher reporter expression in the presence of replicase relative to background. Using this highly sensitive assay to analyze CHIKV nsP1 functionality, several mutations that severely reduced, but did not completely block, CHIKV replicase activity were identified: (i) nsP1 tagged at its N terminus with enhanced green fluorescent protein; (ii) mutations D63A and Y248A, blocking the RNA capping; and (iii) mutation R252E, affecting nsP1 membrane anchoring. In contrast, a mutation in the nsP1 palmitoylation site completely inactivated CHIKV replicase in both human and mosquito cells and was lethal for the virus. Our data confirm that this novel system provides a valuable tool to study CHIKV replicase, RNA replication, and virus-host interactions.IMPORTANCE Chikungunya virus (CHIKV) is a medically important pathogen responsible for recent large-scale epidemics. The development of efficient therapies against CHIKV has been hampered by gaps in our understanding of how nonstructural proteins (nsPs) function to form the viral replicase and replicate virus RNA. Here we describe an extremely sensitive assay to analyze the effects of mutations on the virus RNA synthesis machinery in cells of both mammalian (host) and mosquito (vector) origin. Using this system, several lethal mutations in CHIKV nsP1 were shown to reduce but not completely block the ability of its replicase to synthesize viral RNAs. However, in contrast to related alphaviruses, CHIKV replicase was completely inactivated by mutations preventing palmitoylation of nsP1. These data can be used to develop novel, virus-specific antiviral treatments.
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19
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The Host DHX9 DExH-Box Helicase Is Recruited to Chikungunya Virus Replication Complexes for Optimal Genomic RNA Translation. J Virol 2019; 93:JVI.01764-18. [PMID: 30463980 DOI: 10.1128/jvi.01764-18] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 11/19/2018] [Indexed: 12/19/2022] Open
Abstract
Beyond their role in cellular RNA metabolism, DExD/H-box RNA helicases are hijacked by various RNA viruses in order to assist replication of the viral genome. Here, we identify the DExH-box RNA helicase 9 (DHX9) as a binding partner of chikungunya virus (CHIKV) nsP3 mainly interacting with the C-terminal hypervariable domain. We show that during early CHIKV infection, DHX9 is recruited to the plasma membrane, where it associates with replication complexes. At a later stage of infection, DHX9 is, however, degraded through a proteasome-dependent mechanism. Using silencing experiments, we demonstrate that while DHX9 negatively controls viral RNA synthesis, it is also required for optimal mature nonstructural protein translation. Altogether, this study identifies DHX9 as a novel cofactor for CHIKV replication in human cells that differently regulates the various steps of CHIKV life cycle and may therefore mediate a switch in RNA usage from translation to replication during the earliest steps of CHIKV replication.IMPORTANCE The reemergence of chikungunya virus (CHIKV), an alphavirus that is transmitted to humans by Aedes mosquitoes, is a serious global health threat. In the absence of effective antiviral drugs, CHIKV infection has a significant impact on human health, with chronic arthritis being one of the most serious complications. The molecular understanding of host-virus interactions is a prerequisite to the development of targeted therapeutics capable to interrupt viral replication and transmission. Here, we identify the host cell DHX9 DExH-Box helicase as an essential cofactor for early CHIKV genome translation. We demonstrate that CHIKV nsP3 protein acts as a key factor for DHX9 recruitment to replication complexes. Finally, we establish that DHX9 behaves as a switch that regulates the progression of the viral cycle from translation to genome replication. This study might therefore have a significant impact on the development of antiviral strategies.
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20
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Bartholomeeusen K, Utt A, Coppens S, Rausalu K, Vereecken K, Ariën KK, Merits A. A Chikungunya Virus trans-Replicase System Reveals the Importance of Delayed Nonstructural Polyprotein Processing for Efficient Replication Complex Formation in Mosquito Cells. J Virol 2018; 92:e00152-18. [PMID: 29695432 PMCID: PMC6026725 DOI: 10.1128/jvi.00152-18] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 04/23/2018] [Indexed: 12/16/2022] Open
Abstract
Chikungunya virus (CHIKV) is a medically important alphavirus that is transmitted by Aedes aegypti and Aedes albopictus mosquitoes. The viral replicase complex consists of four nonstructural proteins (nsPs) expressed as a polyprotein precursor and encompasses all enzymatic activities required for viral RNA replication. nsPs interact with host components of which most are still poorly understood, especially in mosquitos. A CHIKV trans-replicase system that allows the uncoupling of RNA replication and nsP expression was adapted to mosquito cells and subsequently used for analysis of universal and host-specific effects of 17 different nonstructural polyprotein (ns-polyprotein) mutations. It was found that mutations blocking nsP enzymatic activities as well as insertions of enhanced green fluorescent protein (EGFP) into different nsPs had similar effects on trans-replicase activity regardless of the host (i.e., mammalian or mosquito). Mutations that slow down or accelerate ns-polyprotein processing generally had no effect or reduced trans-replicase activity in mammalian cells, while in mosquito cells most of them increased trans-replicase activity prominently. Increased RNA replication in mosquito cells was counteracted by an antiviral RNA interference (RNAi) response. Substitution of the W258 residue in the membrane binding peptide of nsP1 resulted in a temperature-sensitive defect, in the context of both the trans-replicase and infectious CHIKV. The defect was compensated for by secondary mutations selected during passaging of mutant CHIKV. These findings demonstrate the value of alphavirus trans-replicase systems for studies of viral RNA replication and virus-host interactions.IMPORTANCE Chikungunya virus is an important mosquito-transmitted human pathogen. This virus actively replicates in mosquitoes, but the underlying molecular mechanisms and interactions of viral and host components are poorly understood. This is partly due to the lack of reliable systems for functional analysis of viral nonstructural polyproteins (ns-polyproteins) and nonstructural proteins (nsPs) in mosquito cells. Adaption of a CHIKV trans-replicase system allowed study of the effects of mutations in the ns-polyprotein on RNA replication in cells derived from mammalian and mosquito hosts. We found that a slowdown of ns-polyprotein processing facilitates replication complex formation and/or functioning in mosquito cells and that this process is antagonized by the natural RNAi defense system present in mosquito cells. The mosquito-adapted CHIKV trans-replicase system represents a valuable tool to study alphavirus-mosquito interactions at the molecular level and to develop advanced antiviral strategies.
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Affiliation(s)
- Koen Bartholomeeusen
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Age Utt
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Sandra Coppens
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Kai Rausalu
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Katleen Vereecken
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Kevin K Ariën
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
- Department of Biomedical Sciences, University of Antwerp, Wilrijk, Belgium
| | - Andres Merits
- Institute of Technology, University of Tartu, Tartu, Estonia
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21
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Kaur R, Mudgal R, Narwal M, Tomar S. Development of an ELISA assay for screening inhibitors against divalent metal ion dependent alphavirus capping enzyme. Virus Res 2018; 256:209-218. [PMID: 29958924 DOI: 10.1016/j.virusres.2018.06.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Revised: 06/21/2018] [Accepted: 06/26/2018] [Indexed: 11/24/2022]
Abstract
Alphavirus non-structural protein, nsP1 has a distinct molecular mechanism of capping the viral RNAs than the conventional capping mechanism of host. Thus, alphavirus capping enzyme nsP1 is a potential drug target. nsP1 catalyzes the methylation of guanosine triphosphate (GTP) by transferring the methyl group from S-adenosylmethionine (SAM) to a GTP molecule at its N7 position with the help of nsP1 methyltransferase (MTase) followed by guanylylation (GT) reaction which involves the formation of m7GMP-nsP1 covalent complex by nsP1 guanylyltransferase (GTase). In subsequent reactions, m7GMP moiety is added to the 5' end of the viral ppRNA by nsP1 GTase resulting in the formation of cap0 structure. In the present study, chikungunya virus (CHIKV) nsP1 MTase and GT reactions were confirmed by an indirect non-radioactive colorimetric assay and western blot assay using an antibody specific for the m7G cap, respectively. The purified recombinant CHIKV nsP1 has been used for the development of a rapid and sensitive non-radioactive enzyme linked immunosorbent assay (ELISA) to identify the inhibitors of CHIKV nsP1. The MTase reaction is followed by GT reaction and resulted in m7GMP-nsP1 covalent complex formation. The developed ELISA nsP1 assay measures this m7GMP-nsP1 complex by utilizing anti-m7G cap monoclonal antibody. The mutation of a conserved residue Asp63 to Ala revealed its role in nsP1 enzyme reaction. Inductively coupled plasma mass spectroscopy (ICP-MS) was used to determine the presence of magnesium ions (Mg2+) in the purified nsP1 protein. The divalent metal ion selectivity and investigation show preference for Mg2+ ion by CHIKV nsP1. Additionally, using the developed ELISA nsP1 assay, the inhibitory effects of sinefungin, aurintricarboxylic acid (ATA) and ribavirin were determined and the IC50 values were estimated to be 2.69 μM, 5.72 μM and 1.18 mM, respectively.
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Affiliation(s)
- Ramanjit Kaur
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India
| | - Rajat Mudgal
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India
| | - Manju Narwal
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India
| | - Shailly Tomar
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India.
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22
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Wong KZ, Chu JJH. The Interplay of Viral and Host Factors in Chikungunya Virus Infection: Targets for Antiviral Strategies. Viruses 2018; 10:E294. [PMID: 29849008 PMCID: PMC6024654 DOI: 10.3390/v10060294] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 05/13/2018] [Accepted: 05/28/2018] [Indexed: 12/14/2022] Open
Abstract
Chikungunya virus (CHIKV) has re-emerged as one of the many medically important arboviruses that have spread rampantly across the world in the past decade. Infected patients come down with acute fever and rashes, and a portion of them suffer from both acute and chronic arthralgia. Currently, there are no targeted therapeutics against this debilitating virus. One approach to develop potential therapeutics is by understanding the viral-host interactions. However, to date, there has been limited research undertaken in this area. In this review, we attempt to briefly describe and update the functions of the different CHIKV proteins and their respective interacting host partners. In addition, we also survey the literature for other reported host factors and pathways involved during CHIKV infection. There is a pressing need for an in-depth understanding of the interaction between the host environment and CHIKV in order to generate potential therapeutics.
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Affiliation(s)
- Kai Zhi Wong
- Laboratory of Molecular RNA Virology & Antiviral Strategies, Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University Health System, 5 Science Drive 2, National University of Singapore, Singapore 117597, Singapore.
| | - Justin Jang Hann Chu
- Laboratory of Molecular RNA Virology & Antiviral Strategies, Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University Health System, 5 Science Drive 2, National University of Singapore, Singapore 117597, Singapore.
- Institute of Molecular & Cell Biology, Agency for Science, Technology & Research (A*STAR), 61 Biopolis Drive, Proteos #06-05, Singapore 138673, Singapore.
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23
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Feibelman KM, Fuller BP, Li L, LaBarbera DV, Geiss BJ. Identification of small molecule inhibitors of the Chikungunya virus nsP1 RNA capping enzyme. Antiviral Res 2018; 154:124-131. [PMID: 29680670 DOI: 10.1016/j.antiviral.2018.03.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 03/16/2018] [Accepted: 03/31/2018] [Indexed: 01/09/2023]
Abstract
Chikungunya virus (CHIKV) is an arthropod-borne alphavirus. Alphaviruses are positive strand RNA viruses that require a 5' cap structure to direct translation of the viral polyprotein and prevent degradation of the viral RNA genome by host cell nucleases. Formation of the 5' RNA cap is orchestrated by the viral protein nsP1, which binds GTP and provides the N-7 methyltransferase and guanylyltransferase activities that are necessary for cap formation. Viruses with aberrant nsP1 activity are unable to replicate effectively suggesting that nsP1 is a promising target for antiviral drug discovery. Given the absence of commercially available antiviral therapies for CHIKV, it is imperative to identify compounds that could be developed as potential therapeutics. This study details a high-throughput screen of 3051 compounds from libraries containing FDA-approved drugs, natural products, and known bioactives against CHIKV nsP1 using a fluorescence polarization-based GTP competition assay. Several small molecule hits from this screen were able to compete with GTP for the CHIKV nsP1 GTP binding site at low molar concentrations. Compounds were also evaluated with an orthogonal assay that measured the ability of nsP1 to perform the guanylation step of the capping reaction in the presence of inhibitor. In addition, live virus assays with CHIKV and closely related alphavirus, Sindbis virus, were used in conjunction with cell toxicity assays to determine the antiviral activity of compounds in cell culture. The naturally derived compound lobaric acid was found to inhibit CHIKV nsP1 GTP binding and guanylation as well as attenuate viral growth in vitro at both 24 hpi and 48 hpi in hamster BHK21 and human Huh 7 cell lines. These data indicate that development of lobaric acid and further exploration of CHIKV nsP1 as a drug target may aid in the progress of anti-alphaviral drug development strategies.
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Affiliation(s)
- Kristen M Feibelman
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
| | - Benjamin P Fuller
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
| | - Linfeng Li
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Daniel V LaBarbera
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Brian J Geiss
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA; School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA.
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24
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Nonstructural Proteins of Alphavirus-Potential Targets for Drug Development. Viruses 2018; 10:v10020071. [PMID: 29425115 PMCID: PMC5850378 DOI: 10.3390/v10020071] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Revised: 02/02/2018] [Accepted: 02/06/2018] [Indexed: 12/31/2022] Open
Abstract
Alphaviruses are enveloped, positive single-stranded RNA viruses, typically transmitted by arthropods. They often cause arthralgia or encephalitic diseases in infected humans and there is currently no targeted antiviral treatment available. The re-emergence of alphaviruses in Asia, Europe, and the Americas over the last decade, including chikungunya and o'nyong'nyong viruses, have intensified the search for selective inhibitors. In this review, we highlight key molecular determinants within the alphavirus replication complex that have been identified as viral targets, focusing on their structure and functionality in viral dissemination. We also summarize recent structural data of these viral targets and discuss how these could serve as templates to facilitate structure-based drug design and development of small molecule inhibitors.
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25
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Kumar S, Kumar A, Mamidi P, Tiwari A, Kumar S, Mayavannan A, Mudulli S, Singh AK, Subudhi BB, Chattopadhyay S. Chikungunya virus nsP1 interacts directly with nsP2 and modulates its ATPase activity. Sci Rep 2018; 8:1045. [PMID: 29348627 PMCID: PMC5773547 DOI: 10.1038/s41598-018-19295-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 12/27/2017] [Indexed: 01/29/2023] Open
Abstract
Chikungunya virus (CHIKV) is a mosquito-borne virus, which has created an alarming threat in the world due to unavailability of vaccine and antiviral compounds. The CHIKV nsP2 contains ATPase, RTPase, helicase and protease activities, whereas, nsP1 is a viral capping enzyme. In alphaviruses, the four non-structural proteins form the replication complex in the cytoplasm and this study characterizes the interaction between CHIKV nsP1 and nsP2. It was observed that, both the proteins co-localize in the cytoplasm and interact in the CHIKV infected cells by confocal microscopy and immunoprecipitation assay. Further, it was demonstrated through mutational analysis that, the amino acids 1-95 of nsP2 and 170-288 of nsP1 are responsible for their direct interaction. Additionally, it was noticed that, the ATPase activity of nsP2 is enhanced in the presence of nsP1, indicating the functional significance of this interaction. In silico analysis showed close (≤1.7 Å) polar interaction (hydrogen bond) between Glu4, Arg7, 96, 225 of nsP2 with Lys256, 206, Val367 and Phe312 of nsP1 respectively. Hence, this investigation provides molecular characterization of CHIKV nsP1-nsP2 interaction which might be a useful target for rational designing of antiviral drugs.
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Affiliation(s)
| | | | | | - Atul Tiwari
- Banaras Hindu University, Varanasi, U.P., India
| | | | | | | | | | - Bharat Bhusan Subudhi
- School of Pharmaceutical Sciences, Siksha O Anusandhan University, Bhubaneswar, India
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26
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Chikungunya Virus Overcomes Polyamine Depletion by Mutation of nsP1 and the Opal Stop Codon To Confer Enhanced Replication and Fitness. J Virol 2017; 91:JVI.00344-17. [PMID: 28539441 PMCID: PMC5512238 DOI: 10.1128/jvi.00344-17] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 05/10/2017] [Indexed: 11/23/2022] Open
Abstract
Polyamines, which are small positively charge molecules present in all cells, play important roles in the replication of DNA and RNA viruses. Chikungunya virus (CHIKV) relies on polyamines for translation of the viral genome upon viral entry, and pharmacological depletion of polyamines limits viral replication. However, the potential development of antiviral resistance necessitates a better understanding of how polyamines function and can be targeted via compounds that alter polyamine levels. We have isolated CHIKV that is resistant to polyamine depletion and contains two mutations in the nonstructural protein 1 (nsP1)-coding region in combination with a mutation to the opal stop codon preceding nsP4. These mutations, in addition to promoting viral replication in polyamine-depleted cells, confer enhanced viral replication in vitro and in vivo. The nsP1 mutations enhance membrane binding and methyltransferase activities, while the stop codon mutation allows increased downstream translation. These mutations, when combined, enhance viral fitness, but individual mutants are attenuated in mosquitoes. Together, our results suggest that CHIKV can evolve resistance to polyamine depletion and that pharmaceuticals targeting the polyamine biosynthetic pathway may be best used in combination with other established antivirals to mitigate the development of resistance. IMPORTANCE Chikungunya virus is a mosquito-borne virus that has infected millions worldwide. Its expansion into the Americas and rapid adaptation to new mosquito hosts present a serious threat to human health, which we can combat with the development of antiviral therapies as well as understanding how these viruses will mutate when exposed to antiviral therapies. Targeting polyamines, small positively charged molecules in the cell, may be a potential strategy against RNA viruses, including chikungunya virus. Here, we have described a virus that is resistant to polyamine depletion and has increased fitness in cells and in full organisms. Mutations in viral genome capping machinery, membrane binding activity, and a stop codon arise, and their altered activities enhance replication in the absence of polyamines. These results highlight strategies by which chikungunya virus can overcome polyamine depletion and emphasize continued research on developing improved antiviral therapies.
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27
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Abstract
Hepatitis E virus (HEV) is a globally important pathogen of acute and chronic hepatitis in humans. The HEV ORF1 gene encodes a nonstructural polyprotein, essential for RNA replication and virus infectivity. Expression and processing of ORF1 polyprotein are shown in prokaryotic and eukaryotic systems, however, its proteolysis into individual proteins is still debated. While molecular or biochemical characterization of methyltransferase, protease, hypervariable region, helicase and RNA polymerase domains in ORF1 has been achieved, the role of the X and Y domains in the HEV life cycle has only been demonstrated very recently. Clinically, detection of a number of ORF1 mutants in infected patients is implicated in disease severity, mortality and drug nonresponse. Moreover, several artificial lethal mutations in ORF1 offer a potential basis for developing live-attenuated vaccines for HEV. This article intends to present the molecular and clinical updates on the HEV ORF1 polyprotein.
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Affiliation(s)
- Mohammad Khalid Parvez
- Department of Pharmacognosy, King Saud University College of Pharmacy, Riyadh 11451, Saudi Arabia
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28
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Pietilä MK, Hellström K, Ahola T. Alphavirus polymerase and RNA replication. Virus Res 2017; 234:44-57. [DOI: 10.1016/j.virusres.2017.01.007] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 01/05/2017] [Accepted: 01/09/2017] [Indexed: 10/20/2022]
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29
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Parvez MK. Mutational analysis of hepatitis E virus ORF1 "Y-domain": Effects on RNA replication and virion infectivity. World J Gastroenterol 2017; 23:590-602. [PMID: 28216965 PMCID: PMC5292332 DOI: 10.3748/wjg.v23.i4.590] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 12/05/2016] [Accepted: 01/04/2017] [Indexed: 02/06/2023] Open
Abstract
AIM To investigate the role of non-structural open reading frame 1 “Y-domain” sequences in the hepatitis E virus (HEV) life cycle.
METHODS Sequences of human HEV Y-domain (amino acid sequences 216-442) and closely-related viruses were analyzed in silico. Site-directed mutagenesis of the Y-domain (HEV SAR55) was carried out and studied in the replicon-baculovirus-hepatoma cell model. In vitro transcribed mRNA (pSK-GFP) constructs were transfected into S10-3 cells and viral RNA replicating GFP-positive cells were scored by flow cytometry. Mutant virions’ infectivity was assayed on naïve HepG2/C3A cells.
RESULTS In silico analysis identified a potential palmitoylation-site (C336C337) and an α-helix segment (L410Y411S412W413L414F415E416) in the HEV Y-domain. Molecular characterization of C336A, C337A and W413A mutants of the three universally conserved residues showed non-viability. Further, of the 10 consecutive saturation mutants covering the entire Y-domain nucleotide sequences (nts 650-1339), three constructs (nts 788-994) severely affected virus replication. This revealed the indispensability of the internal sequences but not of the up- or downstream sequences at the transcriptional level. Interestingly, the three mutated residues corresponded to the downstream codons that tolerated saturation mutation, indicating their post-translational functional/structural essentiality. In addition, RNA secondary structure prediction revealed formation of stable hairpins (nts 788-994) where saturation mutation drastically inhibited virion infectivity.
CONCLUSION This is the first demonstration of the critical role of Y-domain sequences in HEV life cycle, which may involve gene regulation and/or membrane binding in intracellular replication complexes.
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30
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Delgui LR, Colombo MI. A Novel Mechanism Underlying the Innate Immune Response Induction upon Viral-Dependent Replication of Host Cell mRNA: A Mistake of +sRNA Viruses' Replicases. Front Cell Infect Microbiol 2017; 7:5. [PMID: 28164038 PMCID: PMC5247633 DOI: 10.3389/fcimb.2017.00005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 01/04/2017] [Indexed: 12/25/2022] Open
Abstract
Viruses are lifeless particles designed for setting virus-host interactome assuring a new generation of virions for dissemination. This interactome generates a pressure on host organisms evolving mechanisms to neutralize viral infection, which places the pressure back onto virus, a process known as virus-host cell co-evolution. Positive-single stranded RNA (+sRNA) viruses are an important group of viral agents illustrating this interesting phenomenon. During replication, their genomic +sRNA is employed as template for translation of viral proteins; among them the RNA-dependent RNA polymerase (RdRp) is responsible of viral genome replication originating double-strand RNA molecules (dsRNA) as intermediates, which accumulate representing a potent threat for cellular dsRNA receptors to initiate an antiviral response. A common feature shared by these viruses is their ability to rearrange cellular membranes to serve as platforms for genome replication and assembly of new virions, supporting replication efficiency increase by concentrating critical factors and protecting the viral genome from host anti-viral systems. This review summarizes current knowledge regarding cellular dsRNA receptors and describes prototype viruses developing replication niches inside rearranged membranes. However, for several viral agents it's been observed both, a complex rearrangement of cellular membranes and a strong innate immune antiviral response induction. So, we have included recent data explaining the mechanism by, even though viruses have evolved elegant hideouts, host cells are still able to develop dsRNA receptors-dependent antiviral response.
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Affiliation(s)
- Laura R Delgui
- Consejo Nacional de Investigaciones Científicas y Tecnológicas, Facultad de Ciencias Médicas, Instituto de Histología y Embriología de Mendoza, Universidad Nacional de CuyoMendoza, Argentina; Facultad de Ciencias Exactas y Naturales, Universidad Nacional de CuyoMendoza, Argentina
| | - María I Colombo
- Consejo Nacional de Investigaciones Científicas y Tecnológicas, Facultad de Ciencias Médicas, Instituto de Histología y Embriología de Mendoza, Universidad Nacional de Cuyo Mendoza, Argentina
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31
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Moriceau L, Jomat L, Bressanelli S, Alcaide-Loridan C, Jupin I. Identification and Molecular Characterization of the Chloroplast Targeting Domain of Turnip yellow mosaic virus Replication Proteins. FRONTIERS IN PLANT SCIENCE 2017; 8:2138. [PMID: 29312393 PMCID: PMC5742235 DOI: 10.3389/fpls.2017.02138] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 12/04/2017] [Indexed: 05/20/2023]
Abstract
Turnip yellow mosaic virus (TYMV) is a positive-strand RNA virus infecting plants. The TYMV 140K replication protein is a key organizer of viral replication complex (VRC) assembly, being responsible for recruitment of the viral polymerase and for targeting the VRCs to the chloroplast envelope where viral replication takes place. However, the structural requirements determining the subcellular localization and membrane association of this essential viral protein have not yet been defined. In this study, we investigated determinants for the in vivo chloroplast targeting of the TYMV 140K replication protein. Subcellular localization studies of deletion mutants identified a 41-residue internal sequence as the chloroplast targeting domain (CTD) of TYMV 140K; this sequence is sufficient to target GFP to the chloroplast envelope. The CTD appears to be located in the C-terminal extension of the methyltransferase domain-a region shared by 140K and its mature cleavage product 98K, which behaves as an integral membrane protein during infection. We predicted the CTD to fold into two amphipathic α-helices-a folding that was confirmed in vitro by circular dichroism spectroscopy analyses of a synthetic peptide. The importance for subcellular localization of the integrity of these amphipathic helices, and the function of 140K/98K, was demonstrated by performing amino acid substitutions that affected chloroplast targeting, membrane association and viral replication. These results establish a short internal α-helical peptide as an unusual signal for targeting proteins to the chloroplast envelope membrane, and provide new insights into membrane targeting of viral replication proteins-a universal feature of positive-strand RNA viruses.
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Affiliation(s)
- Lucille Moriceau
- Laboratory of Molecular Virology, Institut Jacques Monod, CNRS, Université Paris-Diderot, Paris, France
- Université Paris-Sud – Université Paris-Saclay, Orsay, France
| | - Lucile Jomat
- Laboratory of Molecular Virology, Institut Jacques Monod, CNRS, Université Paris-Diderot, Paris, France
| | - Stéphane Bressanelli
- Institute for Integrative Biology of the Cell, CEA, CNRS, Université Paris-Sud – Université Paris-Saclay, Gif-sur-Yvette, France
| | - Catherine Alcaide-Loridan
- Laboratory of Molecular Virology, Institut Jacques Monod, CNRS, Université Paris-Diderot, Paris, France
| | - Isabelle Jupin
- Laboratory of Molecular Virology, Institut Jacques Monod, CNRS, Université Paris-Diderot, Paris, France
- *Correspondence: Isabelle Jupin,
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32
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Ahola T, Merits A. Functions of Chikungunya Virus Nonstructural Proteins. CHIKUNGUNYA VIRUS 2016. [PMCID: PMC7121661 DOI: 10.1007/978-3-319-42958-8_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The nonstructural proteins (nsPs) of chikungunya virus (CHIKV) are expressed as one or two polyprotein precursors, which are translated directly from the viral genomic RNA. Mature nsPs are generated by precise processing of these polyproteins. Both the precursors and mature nsPs are essential for CHIKV replication. Similar to other alphaviruses, CHIKV nsPs not only perform virus RNA replication but are also crucial for other activities essential for virus infection and pathogenesis. Thus far the best-studied CHIKV ns-protein is nsP2, for which protease, NTPase, RNA triphosphatase, and RNA helicase activities have been demonstrated. In addition, nsP2 is crucial for shut-off of host cell transcription and translation and it counteracts cellular antiviral responses. Compared to their homologues from the well-studied Sindbis and Semliki Forest viruses, CHIKV nsP1, nsP3, and nsP4 have been subjected to only few studies. Nevertheless, there are strong indirect pieces of evidence indicating that these CHIKV proteins have the same enzymatic activities as their counterparts in the other alphaviruses. Information concerning the specific interaction of CHIKV nsPs with host components is beginning to emerge. All the nsPs are involved in the functioning of membrane-bound replication complexes also called spherules, but the finer details of the structure and assembly of these complexes are currently poorly understood.
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33
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Aberle D, Oetter KM, Meyers G. Lipid Binding of the Amphipathic Helix Serving as Membrane Anchor of Pestivirus Glycoprotein Erns. PLoS One 2015; 10:e0135680. [PMID: 26270479 PMCID: PMC4536213 DOI: 10.1371/journal.pone.0135680] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 07/26/2015] [Indexed: 01/30/2023] Open
Abstract
Pestiviruses express a peculiar protein named Erns representing envelope glycoprotein and RNase, which is important for control of the innate immune response and persistent infection. The latter functions are connected with secretion of a certain amount of Erns from the infected cell. Retention/secretion of Erns is most likely controlled by its unusual membrane anchor, a long amphipathic helix attached in plane to the membrane. Here we present results of experiments conducted with a lipid vesicle sedimentation assay able to separate lipid-bound from unbound protein dissolved in the water phase. Using this technique we show that a protein composed of tag sequences and the carboxyterminal 65 residues of Erns binds specifically to membrane vesicles with a clear preference for compositions containing negatively charged lipids. Mutations disturbing the helical folding and/or amphipathic character of the anchor as well as diverse truncations and exchange of amino acids important for intracellular retention of Erns had no or only small effects on the proteins membrane binding. This result contrasts the dramatically increased secretion rates observed for Erns proteins with equivalent mutations within cells. Accordingly, the ratio of secreted versus cell retained Erns is not determined by the lipid affinity of the membrane anchor.
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Affiliation(s)
- Daniel Aberle
- Institut für Immunologie, Friedrich-Loeffler-Institut, Greifswald—Insel Riems, Germany
| | - Kay-Marcus Oetter
- Institut für Immunologie, Friedrich-Loeffler-Institut, Greifswald—Insel Riems, Germany
| | - Gregor Meyers
- Institut für Immunologie, Friedrich-Loeffler-Institut, Greifswald—Insel Riems, Germany
- * E-mail:
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34
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Rupp JC, Sokoloski KJ, Gebhart NN, Hardy RW. Alphavirus RNA synthesis and non-structural protein functions. J Gen Virol 2015. [PMID: 26219641 DOI: 10.1099/jgv.0.000249] [Citation(s) in RCA: 162] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The members of the genus Alphavirus are positive-sense RNA viruses, which are predominantly transmitted to vertebrates by a mosquito vector. Alphavirus disease in humans can be severely debilitating, and depending on the particular viral species, infection may result in encephalitis and possibly death. In recent years, alphaviruses have received significant attention from public health authorities as a consequence of the dramatic emergence of chikungunya virus in the Indian Ocean islands and the Caribbean. Currently, no safe, approved or effective vaccine or antiviral intervention exists for human alphavirus infection. The molecular biology of alphavirus RNA synthesis has been well studied in a few species of the genus and represents a general target for antiviral drug development. This review describes what is currently understood about the regulation of alphavirus RNA synthesis, the roles of the viral non-structural proteins in this process and the functions of cis-acting RNA elements in replication, and points to open questions within the field.
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Affiliation(s)
- Jonathan C Rupp
- Department of Biology, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405, USA
| | - Kevin J Sokoloski
- Department of Biology, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405, USA
| | - Natasha N Gebhart
- Department of Biology, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405, USA
| | - Richard W Hardy
- Department of Biology, Indiana University, 212 South Hawthorne Drive, Bloomington, IN 47405, USA
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35
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mRNA Capping by Venezuelan Equine Encephalitis Virus nsP1: Functional Characterization and Implications for Antiviral Research. J Virol 2015; 89:8292-303. [PMID: 26041283 DOI: 10.1128/jvi.00599-15] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 05/19/2015] [Indexed: 12/26/2022] Open
Abstract
UNLABELLED Alphaviruses are known to possess a unique viral mRNA capping mechanism involving the viral nonstructural protein nsP1. This enzyme harbors methyltransferase (MTase) and nsP1 guanylylation (GT) activities catalyzing the transfer of the methyl group from S-adenosylmethionine (AdoMet) to the N7 position of a GTP molecule followed by the formation of an m(7)GMP-nsP1 adduct. Subsequent transfer of m(7)GMP onto the 5' end of the viral mRNA has not been demonstrated in vitro yet. Here we report the biochemical characterization of Venezuelan equine encephalitis virus (VEEV) nsP1. We have developed enzymatic assays uncoupling the different reactions steps catalyzed by nsP1. The MTase and GT reaction activities were followed using a nonhydrolyzable GTP (GIDP) substrate and an original Western blot assay using anti-m3G/m(7)G-cap monoclonal antibody, respectively. The GT reaction is stimulated by S-adenosyl-l-homocysteine (Ado-Hcy), the product of the preceding MTase reaction, and metallic ions. The covalent linking between nsP1 and m(7)GMP involves a phosphamide bond between the nucleotide and a histidine residue. Final guanylyltransfer onto RNA was observed for the first time with an alphavirus nsP1 using a 5'-diphosphate RNA oligonucleotide whose sequence corresponds to the 5' end of the viral genome. Alanine scanning mutagenesis of residues H37, H45, D63, E118, Y285, D354, R365, N369, and N375 revealed their respective roles in MT and GT reactions. Finally, the inhibitory effects of sinefungin, aurintricarboxylic acid (ATA), and ribavirin triphosphate on MTase and capping reactions were investigated, providing possible avenues for antiviral research. IMPORTANCE Emergence or reemergence of alphaviruses represents a serious health concern, and the elucidation of their replication mechanisms is a prerequisite for the development of specific inhibitors targeting viral enzymes. In particular, alphaviruses are able, through an original reaction sequence, to add to their mRNA a cap required for their protection against cellular nucleases and initiation of viral proteins translation. In this study, the capping of a 5' diphosphate synthetic RNA mimicking the 5' end of an alphavirus mRNA was observed in vitro for the first time. The different steps for this capping are performed by the nonstructural protein 1 (nsP1). Reference compounds known to target the viral capping inhibited nsP1 enzymatic functions, highlighting the value of this enzyme in antiviral development.
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Ahola T, Karlin DG. Sequence analysis reveals a conserved extension in the capping enzyme of the alphavirus supergroup, and a homologous domain in nodaviruses. Biol Direct 2015; 10:16. [PMID: 25886938 PMCID: PMC4392871 DOI: 10.1186/s13062-015-0050-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 03/24/2015] [Indexed: 12/16/2022] Open
Abstract
Background Members of the alphavirus supergroup include human pathogens such as chikungunya virus, hepatitis E virus and rubella virus. They encode a capping enzyme with methyltransferase-guanylyltransferase (MTase-GTase) activity, which is an attractive drug target owing to its unique mechanism. However, its experimental study has proven very difficult. Results We examined over 50 genera of viruses by sequence analyses. Earlier studies showed that the MTase-GTase contains a “Core” region conserved in sequence. We show that it is followed by a long extension, which we termed “Iceberg” region, whose secondary structure, but not sequence, is strikingly conserved throughout the alphavirus supergroup. Sequence analyses strongly suggest that the minimal capping domain corresponds to the Core and Iceberg regions combined, which is supported by earlier experimental data. The Iceberg region contains all known membrane association sites that contribute to the assembly of viral replication factories. We predict that it may also contain an overlooked, widely conserved membrane-binding amphipathic helix. Unexpectedly, we detected a sequence homolog of the alphavirus MTase-GTase in taxa related to nodaviruses and to chronic bee paralysis virus. The presence of a capping enzyme in nodaviruses is biologically consistent, since they have capped genomes but replicate in the cytoplasm, where no cellular capping enzyme is present. The putative MTase-GTase domain of nodaviruses also contains membrane-binding sites that may drive the assembly of viral replication factories, revealing an unsuspected parallel with the alphavirus supergroup. Conclusions Our work will guide the functional analysis of the alphaviral MTase-GTase and the production of domains for structure determination. The identification of a homologous domain in a simple model system, nodaviruses, which replicate in numerous eukaryotic cell systems (yeast, flies, worms, mammals, and plants), can further help crack the function and structure of the enzyme. Reviewers This article was reviewed by Valerian Dolja, Eugene Koonin and Sebastian Maurer-Stroh. Electronic supplementary material The online version of this article (doi:10.1186/s13062-015-0050-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Tero Ahola
- Department of Food and Environmental Sciences, University of Helsinki, 00014, Helsinki, Finland.
| | - David G Karlin
- Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK. .,The Division of Structural Biology, Henry Wellcome Building, Roosevelt Drive, Oxford, OX3 7BN, UK.
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Harak C, Lohmann V. Ultrastructure of the replication sites of positive-strand RNA viruses. Virology 2015; 479-480:418-33. [PMID: 25746936 PMCID: PMC7111692 DOI: 10.1016/j.virol.2015.02.029] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 01/06/2015] [Accepted: 02/16/2015] [Indexed: 12/13/2022]
Abstract
Positive strand RNA viruses replicate in the cytoplasm of infected cells and induce intracellular membranous compartments harboring the sites of viral RNA synthesis. These replication factories are supposed to concentrate the components of the replicase and to shield replication intermediates from the host cell innate immune defense. Virus induced membrane alterations are often generated in coordination with host factors and can be grouped into different morphotypes. Recent advances in conventional and electron microscopy have contributed greatly to our understanding of their biogenesis, but still many questions remain how viral proteins capture membranes and subvert host factors for their need. In this review, we will discuss different representatives of positive strand RNA viruses and their ways of hijacking cellular membranes to establish replication complexes. We will further focus on host cell factors that are critically involved in formation of these membranes and how they contribute to viral replication.
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Affiliation(s)
- Christian Harak
- Department of Infectious Diseases, Molecular Virology, University of Heidelberg, Im Neuenheimer Feld 345, D-69120 Heidelberg, Germany
| | - Volker Lohmann
- Department of Infectious Diseases, Molecular Virology, University of Heidelberg, Im Neuenheimer Feld 345, D-69120 Heidelberg, Germany.
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Membranous replication factories induced by plus-strand RNA viruses. Viruses 2014; 6:2826-57. [PMID: 25054883 PMCID: PMC4113795 DOI: 10.3390/v6072826] [Citation(s) in RCA: 200] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 06/02/2014] [Accepted: 06/24/2014] [Indexed: 12/13/2022] Open
Abstract
In this review, we summarize the current knowledge about the membranous replication factories of members of plus-strand (+) RNA viruses. We discuss primarily the architecture of these complex membrane rearrangements, because this topic emerged in the last few years as electron tomography has become more widely available. A general denominator is that two “morphotypes” of membrane alterations can be found that are exemplified by flaviviruses and hepaciviruses: membrane invaginations towards the lumen of the endoplasmatic reticulum (ER) and double membrane vesicles, representing extrusions also originating from the ER, respectively. We hypothesize that either morphotype might reflect common pathways and principles that are used by these viruses to form their membranous replication compartments.
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Das PK, Merits A, Lulla A. Functional cross-talk between distant domains of chikungunya virus non-structural protein 2 is decisive for its RNA-modulating activity. J Biol Chem 2014; 289:5635-53. [PMID: 24407286 DOI: 10.1074/jbc.m113.503433] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Chikungunya virus (CHIKV) non-structural protein 2 (nsP2) is a multifunctional protein that is considered a master regulator of the viral life cycle and a main viral factor responsible for cytopathic effects and subversion of antiviral defense. The C-terminal part of nsP2 possesses protease activity, whereas the N-terminal part exhibits NTPase and RNA triphosphatase activity and is proposed to have helicase activity. Bioinformatics analysis classified CHIKV nsP2 into helicase superfamily 1. However, the biochemical significance of a coexistence of two functionally unrelated modules in this single protein remains unknown. In this study, recombinant nsP2 demonstrated unwinding of double-stranded RNA in a 5'-3' directionally biased manner and RNA strand annealing activity. Comparative analysis of NTPase and helicase activities of wild type nsP2 with enzymatic capabilities of different truncated or N-terminally extended variants of nsP2 revealed that the C-terminal part of the protein is indispensable for helicase functionality and presumably provides a platform for RNA binding, whereas the N-terminal-most region is apparently involved in obtaining a conformation of nsP2 that allows for its maximal enzymatic activities. The establishment of the protocols for the production of biochemically active CHIKV nsP2 and optimization of the parameters for helicase and NTPase assays are expected to provide the starting point for a further search of possibilities for therapeutic interventions to suppress alphaviral infections.
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Affiliation(s)
- Pratyush Kumar Das
- From the Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia
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Thiberville SD, Moyen N, Dupuis-Maguiraga L, Nougairede A, Gould EA, Roques P, de Lamballerie X. Chikungunya fever: epidemiology, clinical syndrome, pathogenesis and therapy. Antiviral Res 2013; 99:345-70. [PMID: 23811281 PMCID: PMC7114207 DOI: 10.1016/j.antiviral.2013.06.009] [Citation(s) in RCA: 304] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Revised: 05/21/2013] [Accepted: 06/18/2013] [Indexed: 12/11/2022]
Abstract
Chikungunya fever is caused by a mosquito-borne alphavirus originating in East Africa. During the past 7 years, the disease has spread to islands of the Indian Ocean, Asia and Europe. Its spread has been facilitated by a mutation favouring replication in the mosquito Ae. albopictus. No vaccines or antiviral drugs are available to prevent or treat chikungunya fever. This paper provides an extensive review of the virus and disease, including Supplementary Tables.
Chikungunya virus (CHIKV) is the aetiological agent of the mosquito-borne disease chikungunya fever, a debilitating arthritic disease that, during the past 7 years, has caused immeasurable morbidity and some mortality in humans, including newborn babies, following its emergence and dispersal out of Africa to the Indian Ocean islands and Asia. Since the first reports of its existence in Africa in the 1950s, more than 1500 scientific publications on the different aspects of the disease and its causative agent have been produced. Analysis of these publications shows that, following a number of studies in the 1960s and 1970s, and in the absence of autochthonous cases in developed countries, the interest of the scientific community remained low. However, in 2005 chikungunya fever unexpectedly re-emerged in the form of devastating epidemics in and around the Indian Ocean. These outbreaks were associated with mutations in the viral genome that facilitated the replication of the virus in Aedes albopictus mosquitoes. Since then, nearly 1000 publications on chikungunya fever have been referenced in the PubMed database. This article provides a comprehensive review of chikungunya fever and CHIKV, including clinical data, epidemiological reports, therapeutic aspects and data relating to animal models for in vivo laboratory studies. It includes Supplementary Tables of all WHO outbreak bulletins, ProMED Mail alerts, viral sequences available on GenBank, and PubMed reports of clinical cases and seroprevalence studies.
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Affiliation(s)
- Simon-Djamel Thiberville
- UMR_D 190 "Emergence des Pathologies Virales" (Aix-Marseille Univ. IRD French Institute of Research for Development EHESP French School of Public Health), Marseille, France; University Hospital Institute for Infectious Disease and Tropical Medicine, Marseille, France.
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Hypervariable domain of nonstructural protein nsP3 of Venezuelan equine encephalitis virus determines cell-specific mode of virus replication. J Virol 2013; 87:7569-84. [PMID: 23637407 DOI: 10.1128/jvi.00720-13] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Venezuelan equine encephalitis virus (VEEV) is one of the most pathogenic members of the Alphavirus genus in the Togaviridae family. This genus is divided into the Old World and New World alphaviruses, which demonstrate profound differences in pathogenesis, replication, and virus-host interactions. VEEV is a representative member of the New World alphaviruses. The biology of this virus is still insufficiently understood, particularly the function of its nonstructural proteins in RNA replication and modification of the intracellular environment. One of these nonstructural proteins, nsP3, contains a hypervariable domain (HVD), which demonstrates very low overall similarity between different alphaviruses, suggesting the possibility of its function in virus adaptation to different hosts and vectors. The results of our study demonstrate the following. (i) Phosphorylation of the VEEV nsP3-specific HVD does not play a critical role in virus replication in cells of vertebrate origin but is important for virus replication in mosquito cells. (ii) The VEEV HVD is not required for viral RNA replication in the highly permissive BHK-21 cell line. In fact, it can be either completely deleted or replaced by a heterologous protein sequence. These variants require only one or two additional adaptive mutations in nsP3 and/or nsP2 proteins to achieve an efficiently replicating phenotype. (iii) However, the carboxy-terminal repeat in the VEEV HVD is indispensable for VEEV replication in the cell lines other than BHK-21 and plays a critical role in formation of VEEV-specific cytoplasmic protein complexes. Natural VEEV variants retain at least one of the repeated elements in their nsP3 HVDs.
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Host acyl coenzyme A binding protein regulates replication complex assembly and activity of a positive-strand RNA virus. J Virol 2012; 86:5110-21. [PMID: 22345450 DOI: 10.1128/jvi.06701-11] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
All positive-strand RNA viruses reorganize host intracellular membranes to assemble their replication complexes. Similarly, brome mosaic virus (BMV) induces two alternate forms of membrane-bound RNA replication complexes: vesicular spherules and stacks of appressed double-membrane layers. The mechanisms by which these membrane rearrangements are induced, however, remain unclear. We report here that host ACB1-encoded acyl coenzyme A (acyl-CoA) binding protein (ACBP) is required for the assembly and activity of both BMV RNA replication complexes. ACBP is highly conserved among eukaryotes, specifically binds to long-chain fatty acyl-CoA, and promotes general lipid synthesis. Deleting ACB1 inhibited BMV RNA replication up to 30-fold and resulted in formation of spherules that were ∼50% smaller but ∼4-fold more abundant than those in wild-type (wt) cells, consistent with the idea that BMV 1a invaginates and maintains viral spherules by coating the inner spherule membrane. Furthermore, smaller and more frequent spherules were preferentially formed under conditions that induce layer formation in wt cells. Conversely, cellular karmella structures, which are arrays of endoplasmic reticulum (ER) membranes formed upon overexpression of certain cellular ER membrane proteins, were formed normally, indicating a selective inhibition of 1a-induced membrane rearrangements. Restoring altered lipid composition largely complemented the BMV RNA replication defect, suggesting that ACBP was required for maintaining lipid homeostasis. Smaller and more frequent spherules are also induced by 1a mutants with specific substitutions in a membrane-anchoring amphipathic α-helix, implying that the 1a-lipid interactions play critical roles in viral replication complex assembly.
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Nishikiori M, Mori M, Dohi K, Okamura H, Katoh E, Naito S, Meshi T, Ishikawa M. A host small GTP-binding protein ARL8 plays crucial roles in tobamovirus RNA replication. PLoS Pathog 2011; 7:e1002409. [PMID: 22174675 PMCID: PMC3234234 DOI: 10.1371/journal.ppat.1002409] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Accepted: 10/14/2011] [Indexed: 12/16/2022] Open
Abstract
Tomato mosaic virus (ToMV), like other eukaryotic positive-strand RNA viruses, replicates its genomic RNA in replication complexes formed on intracellular membranes. Previous studies showed that a host seven-pass transmembrane protein TOM1 is necessary for efficient ToMV multiplication. Here, we show that a small GTP-binding protein ARL8, along with TOM1, is co-purified with a FLAG epitope-tagged ToMV 180K replication protein from solubilized membranes of ToMV-infected tobacco (Nicotiana tabacum) cells. When solubilized membranes of ToMV-infected tobacco cells that expressed FLAG-tagged ARL8 were subjected to immunopurification with anti-FLAG antibody, ToMV 130K and 180K replication proteins and TOM1 were co-purified and the purified fraction showed RNA-dependent RNA polymerase activity that transcribed ToMV RNA. From uninfected cells, TOM1 co-purified with FLAG-tagged ARL8 less efficiently, suggesting that a complex containing ToMV replication proteins, TOM1, and ARL8 are formed on membranes in infected cells. In Arabidopsis thaliana, ARL8 consists of four family members. Simultaneous mutations in two specific ARL8 genes completely inhibited tobamovirus multiplication. In an in vitro ToMV RNA translation-replication system, the lack of either TOM1 or ARL8 proteins inhibited the production of replicative-form RNA, indicating that TOM1 and ARL8 are required for efficient negative-strand RNA synthesis. When ToMV 130K protein was co-expressed with TOM1 and ARL8 in yeast, RNA 5'-capping activity was detected in the membrane fraction. This activity was undetectable or very weak when the 130K protein was expressed alone or with either TOM1 or ARL8. Taken together, these results suggest that TOM1 and ARL8 are components of ToMV RNA replication complexes and play crucial roles in a process toward activation of the replication proteins' RNA synthesizing and capping functions.
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Affiliation(s)
- Masaki Nishikiori
- Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
| | - Masashi Mori
- Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, Nonoichi, Ishikawa, Japan
| | - Koji Dohi
- Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, Nonoichi, Ishikawa, Japan
| | - Hideyasu Okamura
- Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
| | - Etsuko Katoh
- Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
| | - Satoshi Naito
- Graduate School of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Tetsuo Meshi
- Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
| | - Masayuki Ishikawa
- Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
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Heterologous production, purification and characterization of enzymatically active Sindbis virus nonstructural protein nsP1. Protein Expr Purif 2011; 79:277-84. [PMID: 21693190 DOI: 10.1016/j.pep.2011.05.022] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 05/27/2011] [Accepted: 05/31/2011] [Indexed: 11/22/2022]
Abstract
Alphavirus nonstructural protein nsP1 possesses distinct methyltransferase (MTase) and guanylyltransferase (GTase) activities involved in the capping of viral RNAs. In alphaviruses, the methylation of GTP occurs before RNA transguanylation and nsP1 forms a covalent complex with m(7)GMP unlike the host mRNA guanylyltransferase which forms GMP-enzyme complex. In this study, full length SINV nsP1 was expressed in a soluble form with an N-terminal histidine tag in Escherichia coli and purified to homogeneity. The purified protein is enzymatically active and contains both MTase and GTase activity indicating that SINV nsP1 does not require membrane association for its enzymatic function. Biochemical analysis shows that detergents abolish nsP1 GTase activity, whereas nonionic detergents do not affect MTase activity. Furthermore, SINV nsP1 contains the metal-ion dependent GTase, whereas MTase does not require a metal ion. Circular dichroism spectroscopic analysis of purified protein indicate that nsP1 has a mixed α/β structure and is in the folded native conformation.
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Takai E, Hirano A, Shiraki K. Effects of alkyl chain length of gallate on self-association and membrane binding. J Biochem 2011; 150:165-71. [PMID: 21508039 PMCID: PMC6327286 DOI: 10.1093/jb/mvr048] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Alkyl gallates are anticipated for their use as anti-bacterial and anti-viral agents. Although their pharmacological activities depend on their alkyl chain length, no mechanism has yet been clarified. As described herein, we investigated the membrane binding properties of a series of alkyl gallates using fluorescence measurement to elucidate their different pharmacological activities. Membrane binding of the alkyl gallates increased concomitantly with increasing alkyl chain length, except for cetyl gallate and stearyl gallate. Dynamic light scattering revealed that alkyl gallates with a long alkyl chain are prone to self-association in the solution. Membrane binding abilities of the alkyl gallates are correlated with anti-bacterial and anti-virus activities, as described in previous reports. The partition constants of the alkyl gallates to lipid membranes depend on the membrane components and the membrane phase. Self-association and lipid binding of the alkyl gallates might be primary biophysical factors associated with their pharmacological activities.
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Affiliation(s)
- Eisuke Takai
- Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan
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Phosphatidylinositol 3-kinase-, actin-, and microtubule-dependent transport of Semliki Forest Virus replication complexes from the plasma membrane to modified lysosomes. J Virol 2010; 84:7543-57. [PMID: 20484502 DOI: 10.1128/jvi.00477-10] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Like other positive-strand RNA viruses, alphaviruses replicate their genomes in association with modified intracellular membranes. Alphavirus replication sites consist of numerous bulb-shaped membrane invaginations (spherules), which contain the double-stranded replication intermediates. Time course studies with Semliki Forest virus (SFV)-infected cells were combined with live-cell imaging and electron microscopy to reveal that the replication complex spherules of SFV undergo an unprecedented large-scale movement between cellular compartments. The spherules first accumulated at the plasma membrane and were then internalized using an endocytic process that required a functional actin-myosin network, as shown by blebbistatin treatment. Wortmannin and other inhibitors indicated that the internalization of spherules also required the activity of phosphatidylinositol 3-kinase. The spherules therefore represent an unusual type of endocytic cargo. After endocytosis, spherule-containing vesicles were highly dynamic and had a neutral pH. These primary carriers fused with acidic endosomes and moved long distances on microtubules, in a manner prevented by nocodazole. The result of the large-scale migration was the formation of a very stable compartment, where the spherules were accumulated on the outer surfaces of unusually large and static acidic vacuoles localized in the pericentriolar region. Our work highlights both fundamental similarities and important differences in the processes that lead to the modified membrane compartments in cells infected by distinct groups of positive-sense RNA viruses.
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Gould EA, Coutard B, Malet H, Morin B, Jamal S, Weaver S, Gorbalenya A, Moureau G, Baronti C, Delogu I, Forrester N, Khasnatinov M, Gritsun T, de Lamballerie X, Canard B. Understanding the alphaviruses: recent research on important emerging pathogens and progress towards their control. Antiviral Res 2009; 87:111-24. [PMID: 19616028 PMCID: PMC7114216 DOI: 10.1016/j.antiviral.2009.07.007] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2009] [Revised: 07/07/2009] [Accepted: 07/11/2009] [Indexed: 11/28/2022]
Abstract
The alphaviruses were amongst the first arboviruses to be isolated, characterized and assigned a taxonomic status. They are globally very widespread, infecting a large variety of terrestrial animals, insects and even fish, and circulate both in the sylvatic and urban/peri-urban environment, causing considerable human morbidity and mortality. Nevertheless, despite their obvious importance as pathogens, there are currently no effective antiviral drugs with which to treat humans or animals infected by any of these viruses. The EU-supported project-VIZIER (Comparative Structural Genomics of Viral Enzymes Involved in Replication, FP6 PROJECT: 2004-511960) was instigated with an ultimate view of contributing to the development of antiviral therapies for RNA viruses, including the alphaviruses [Coutard, B., Gorbalenya, A.E., Snijder, E.J., Leontovich, A.M., Poupon, A., De Lamballerie, X., Charrel, R., Gould, E.A., Gunther, S., Norder, H., Klempa, B., Bourhy, H., Rohayemj, J., L'hermite, E., Nordlund, P., Stuart, D.I., Owens, R.J., Grimes, J.M., Tuckerm, P.A., Bolognesi, M., Mattevi, A., Coll, M., Jones, T.A., Aqvist, J., Unger, T., Hilgenfeld, R., Bricogne, G., Neyts, J., La Colla, P., Puerstinger, G., Gonzalez, J.P., Leroy, E., Cambillau, C., Romette, J.L., Canard, B., 2008. The VIZIER project: preparedness against pathogenic RNA viruses. Antiviral Res. 78, 37-46]. This review highlights some of the major features of alphaviruses that have been investigated during recent years. After describing their classification, epidemiology and evolutionary history and the expanding geographic distribution of Chikungunya virus, we review progress in understanding the structure and function of alphavirus replicative enzymes achieved under the VIZIER programme and the development of new disease control strategies.
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Affiliation(s)
- E A Gould
- Institut de Recherche pour le Développement UMR190/Unité des Virus Emergents, Université de la Méditerranée, Marseille, France.
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Kiiver K, Tagen I, Žusinaite E, Tamberg N, Fazakerley JK, Merits A. Properties of non-structural protein 1 of Semliki Forest virus and its interference with virus replication. J Gen Virol 2008; 89:1457-1466. [PMID: 18474562 PMCID: PMC2430273 DOI: 10.1099/vir.0.2008/000299-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Semliki Forest virus (SFV) non-structural protein 1 (nsP1) is a major component of the virus replicase complex. It has previously been studied in cells infected with virus or using transient or stable expression systems. To extend these studies, tetracycline-inducible stable cell lines expressing SFV nsP1 or its palmitoylation-negative mutant (nsP16D) were constructed. The levels of protein expression and the subcellular localization of nsP1 in induced cells were similar to those in virus-infected cells. The nsP1 expressed by stable, inducible cell lines or by SFV-infected HEK293 T-REx cells was a stable protein with a half-life of approximately 5 h. In contrast to SFV infection, induction of nsP1 expression had no detectable effect on cellular transcription, translation or viability. Induction of expression of nsP1 or nsP16D interfered with multiplication of SFV, typically resulting in a 5–10-fold reduction in virus yields. This reduction was not due to a decrease in the number of infected cells, indicating that nsP1 expression does not block virus entry or initiation of replication. Expression of nsP1 interfered with virus genomic RNA synthesis and delayed accumulation of viral subgenomic RNA translation products. Expression of nsP1 with a mutation in the palmitoylation site reduced synthesis of genomic and subgenomic RNAs and their products of translation, and this effect did not resolve with time. These results are in agreement with data published previously, suggesting a role for nsP1 in genomic RNA synthesis.
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Affiliation(s)
- Kaja Kiiver
- Estonian Biocentre, Tartu, Estonia.,Institute of Technology, University of Tartu, Tartu, Estonia
| | - Ingrid Tagen
- Estonian Biocentre, Tartu, Estonia.,Institute of Technology, University of Tartu, Tartu, Estonia
| | - Eva Žusinaite
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Nele Tamberg
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - John K Fazakerley
- Centre for Infectious Diseases, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK
| | - Andres Merits
- Estonian Biocentre, Tartu, Estonia.,Institute of Technology, University of Tartu, Tartu, Estonia
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Tews BA, Meyers G. The pestivirus glycoprotein Erns is anchored in plane in the membrane via an amphipathic helix. J Biol Chem 2007; 282:32730-41. [PMID: 17848558 DOI: 10.1074/jbc.m706803200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
E(rns) is a structural glycoprotein of pestiviruses found to be attached to the virion and to membranes within infected cells via its COOH terminus, although it lacks a hydrophobic anchor sequence. The COOH-terminal sequence was hypothesized to fold into an amphipathic alpha-helix. Alanine insertion scanning revealed that the ability of the E(rns) COOH terminus to bind membranes is considerably reduced by the insertion of a single amino acid at a wide variety of positions. Mutations decreasing the hydrophobicity of the apolar face of the putative helix led to reduction of membrane association. Proteinase K protection assays showed that E(rns) translated in vitro in the presence of microsomal membranes was protected, whereas a mutant with an artificial transmembrane region and a short cytosolic tag was shortened by the protease treatment. A tag fused to the COOH terminus of wild type E(rns) was not accessible for antibodies within digitonin-permeabilized cells, but the variant with the tag located downstream of the artificial transmembrane region was detected under the same conditions. These results are in accordance with the model that the COOH-terminal membrane anchor of E(rns) represents an amphipathic helix embedded in plane into the membrane. The integrity of the membrane anchor was found to be important for recovery of infectious virus.
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Balistreri G, Caldentey J, Kääriäinen L, Ahola T. Enzymatic defects of the nsP2 proteins of Semliki Forest virus temperature-sensitive mutants. J Virol 2007; 81:2849-60. [PMID: 17202213 PMCID: PMC1866018 DOI: 10.1128/jvi.02078-06] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
We have analyzed the biochemical consequences of mutations that affect viral RNA synthesis in Semliki Forest virus temperature-sensitive (ts) mutants. Of the six mutations mapping in the multifunctional replicase protein nsP2, three were located in the N-terminal helicase region and three were in the C-terminal protease domain. Wild-type and mutant nsP2s were expressed, purified, and assayed for nucleotide triphosphatase (NTPase), RNA triphosphatase (RTPase), and protease activities in vitro at 24 degrees C and 35 degrees C. The protease domain mutants (ts4, ts6, and ts11) had reduced protease activity at 35 degrees C but displayed normal NTPase and RTPase. The helicase domain mutation ts1 did not have enzymatic consequences, whereas ts13a and ts9 reduced both NTPase and protease activities but in different and mutant-specific ways. The effects of these helicase domain mutants on protease function suggest interdomain interactions within nsP2. NTPase activity was not directly required for protease activity. The similarities of the NTPase and RTPase results, as well as competition experiments, suggest that these two reactions utilize the same active site. The mutations were also studied in recombinant viruses first cultivated at the permissive temperature and then shifted up to the restrictive temperature. Processing of the nonstructural polyprotein was generally retarded in cells infected with viruses carrying the ts4, ts6, ts11, and ts13a mutations, and a specific defect appeared in ts9. All mutations except ts13a were associated with a large reduction in the production of the subgenomic 26S mRNA, indicating that both protease and helicase domains influence the recognition of the subgenomic promoter during virus replication.
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Affiliation(s)
- Giuseppe Balistreri
- Institute of Biotechnology, P.O. Box 56, University of Helsinki, FIN-00014 Helsinki, Finland
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