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Metibemu DS, Adeyinka OS, Falode J, Crown O, Ogungbe IV. Inhibitors of the Structural and Nonstructural Proteins of Alphaviruses. ACS Infect Dis 2024; 10:2507-2524. [PMID: 38992989 DOI: 10.1021/acsinfecdis.4c00254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/13/2024]
Abstract
The Alphavirus genus includes viruses that cause encephalitis due to neuroinvasion and viruses that cause arthritis due to acute and chronic inflammation. There is no approved therapeutic for alphavirus infections, but significant efforts are ongoing, more so in recent years, to develop vaccines and therapeutics for alphavirus infections. This review article highlights some of the major advances made so far to identify small molecules that can selectively target the structural and the nonstructural proteins in alphaviruses with the expectation that persistent investigation of an increasingly expanding chemical space through a variety of structure-based design and high-throughput screening strategies will yield candidate drugs for clinical studies. While most of the works discussed are still in the early discovery to lead optimization stages, promising avenues remain for drug development against this family of viruses.
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Affiliation(s)
- Damilohun Samuel Metibemu
- Chemistry and Biotechnology Science and Engineering Programs, The University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, Alabama 35899, United States
| | - Olawale Samuel Adeyinka
- Chemistry and Biotechnology Science and Engineering Programs, The University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, Alabama 35899, United States
| | - John Falode
- Chemistry and Biotechnology Science and Engineering Programs, The University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, Alabama 35899, United States
| | - Olamide Crown
- Chemistry and Biotechnology Science and Engineering Programs, The University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, Alabama 35899, United States
| | - Ifedayo Victor Ogungbe
- Chemistry and Biotechnology Science and Engineering Programs, The University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, Alabama 35899, United States
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2
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Yıldız A, Răileanu C, Beissert T. Trans-Amplifying RNA: A Journey from Alphavirus Research to Future Vaccines. Viruses 2024; 16:503. [PMID: 38675846 PMCID: PMC11055088 DOI: 10.3390/v16040503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 03/19/2024] [Accepted: 03/21/2024] [Indexed: 04/28/2024] Open
Abstract
Replicating RNA, including self-amplifying RNA (saRNA) and trans-amplifying RNA (taRNA), holds great potential for advancing the next generation of RNA-based vaccines. Unlike in vitro transcribed mRNA found in most current RNA vaccines, saRNA or taRNA can be massively replicated within cells in the presence of RNA-amplifying enzymes known as replicases. We recently demonstrated that this property could enhance immune responses with minimal injected RNA amounts. In saRNA-based vaccines, replicase and antigens are encoded on the same mRNA molecule, resulting in very long RNA sequences, which poses significant challenges in production, delivery, and stability. In taRNA-based vaccines, these challenges can be overcome by splitting the replication system into two parts: one that encodes replicase and the other that encodes a short antigen-encoding RNA called transreplicon. Here, we review the identification and use of transreplicon RNA in alphavirus research, with a focus on the development of novel taRNA technology as a state-of-the art vaccine platform. Additionally, we discuss remaining challenges essential to the clinical application and highlight the potential benefits related to the unique properties of this future vaccine platform.
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Affiliation(s)
| | | | - Tim Beissert
- TRON—Translational Oncology at the University Medical Center of the Johannes Gutenberg University Mainz, 55131 Mainz, Germany; (A.Y.); (C.R.)
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3
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Cao V, Loeanurit N, Hengphasatporn K, Hairani R, Wacharachaisurapol N, Prompila N, Wittayalertpanya S, Shigeta Y, Khotavivattana T, Chavasiri W, Boonyasuppayakorn S. The 8-bromobaicalein alleviated chikungunya-induced musculoskeletal inflammation and reduced the viral load in healthy adult mice. Emerg Microbes Infect 2023; 12:2270074. [PMID: 37842770 PMCID: PMC10653753 DOI: 10.1080/22221751.2023.2270074] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Accepted: 10/05/2023] [Indexed: 10/17/2023]
Abstract
Chikungunya virus is a re-emerging arbovirus that has caused epidemic outbreaks in recent decades. Patients in older age groups with high viral load and severe immunologic response during acute infection are likely to develop chronic arthritis and severe joint pain. Currently, no antiviral drug is available. Previous studies suggested that a flavone derivative, 8-bromobaicalein, was a potential dengue and Zika replication inhibitor in a cell-based system targeting flaviviral polymerase. Here we characterized that 8-bromobaicalein inhibited chikungunya virus replication with EC50 of 0.49 ± 0.11 µM in Vero cells. The molecular target predicted at viral nsP1 methyltransferase using molecular binding and fragment molecular orbital calculation. Additionally, oral administration of 250 mg/kg twice daily treatment alleviated chikungunya-induced musculoskeletal inflammation and reduced viral load in healthy adult mice. Pharmacokinetic analysis indicated that the 250 mg/kg administration maintained the compound level above EC99.9 for 12 h. Therefore, 8-bromobaicalein should be a potential candidate for further development as a pan-arboviral drug.
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Affiliation(s)
- Van Cao
- Center of Excellence in Applied Medical Virology, Department of Microbiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
- Interdisciplinary Program in Microbiology, Graduate School, Chulalongkorn University, Bangkok, Thailand
- DaNang University of Medical Technology and Pharmacy, DaNang, Vietnam
| | - Naphat Loeanurit
- Center of Excellence in Applied Medical Virology, Department of Microbiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | | | - Rita Hairani
- Center of Excellence in Natural Products Chemistry, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Noppadol Wacharachaisurapol
- Clinical Pharmakokinetics and Pharmacogenomics Research Unit, Department of Pharmacology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Nantaporn Prompila
- Chula Pharmacokinetic Research Center, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Supeecha Wittayalertpanya
- Clinical Pharmakokinetics and Pharmacogenomics Research Unit, Department of Pharmacology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
- Chula Pharmacokinetic Research Center, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Yasuteru Shigeta
- Center for Computational Sciences, University of Tsukuba, Tsukuba, Japan
| | - Tanatorn Khotavivattana
- Center of Excellence in Natural Products Chemistry, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Warinthorn Chavasiri
- Center of Excellence in Natural Products Chemistry, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Siwaporn Boonyasuppayakorn
- Center of Excellence in Applied Medical Virology, Department of Microbiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
- Center of Excellence in Vaccine Research and Development, Chulalongkorn University (Chula-VRC), Bangkok, Thailand
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4
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Komori M, Morey AL, Quiñones-Molina AA, Fofana J, Romero L, Peters E, Matsuda K, Gummuluru S, Smith JF, Akahata W, Akiyama H. Incorporation of 5 methylcytidine alleviates innate immune response to self-amplifying RNA vaccine. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.01.565056. [PMID: 37961509 PMCID: PMC10634970 DOI: 10.1101/2023.11.01.565056] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
In order to improve vaccine effectiveness and safety profile of existing synthetic RNA-based vaccines, we have developed a self-amplifying RNA (saRNA)-based vaccine expressing membrane-anchored receptor binding domain (RBD) of SARS-CoV-2 S protein (S-RBD) and have demonstrated that a minimal dose of this saRNA vaccine elicits robust immune responses. Results from a recent clinical trial with 5-methylcytidine (5mC) incorporating saRNA vaccine demonstrated reduced vaccine-induced adverse effects while maintaining robust humoral responses. In this study, we investigate the mechanisms accounting for induction of efficient innate and adaptive immune responses and attenuated adverse effects induced by the 5mC-incorporated saRNA. We show that the 5mC-incorporating saRNA platform leads to prolonged and robust expression of antigen, while induction of type-I interferon (IFN-I), a key driver of reactogenicity, is attenuated in peripheral blood mononuclear cells (PBMCs), but not in macrophages and dendritic cells. Interestingly, we find that the major cellular source of IFN-I production in PBMCs is plasmacytoid dendritic cells (pDCs), which is attenuated upon 5mC incorporation in saRNA. In addition, we demonstrate that monocytes also play an important role in amplifying proinflammatory responses. Furthermore, we show that the detection of saRNA is mediated by a host cytosolic RNA sensor, RIG-I. Importantly, 5mC-incorporating saRNA vaccine candidate produced robust IgG responses against S-RBD upon injection in mice, thus providing strong support for the potential clinical use of 5mC-incorporating saRNA vaccines.
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Hu C, Liu J, Cheng F, Bai Y, Mao Q, Xu M, Liang Z. Amplifying mRNA vaccines: potential versatile magicians for oncotherapy. Front Immunol 2023; 14:1261243. [PMID: 37936701 PMCID: PMC10626473 DOI: 10.3389/fimmu.2023.1261243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 10/10/2023] [Indexed: 11/09/2023] Open
Abstract
Cancer vaccines drive the activation and proliferation of tumor-reactive immune cells, thereby eliciting tumor-specific immunity that kills tumor cells. Accordingly, they possess immense potential in cancer treatment. However, such vaccines are also faced with challenges related to their design and considerable differences among individual tumors. The success of messenger RNA (mRNA) vaccines against coronavirus disease 2019 has prompted the application of mRNA vaccine technology platforms to the field of oncotherapy. These platforms include linear, circular, and amplifying mRNA vaccines. In particular, amplifying mRNA vaccines are characterized by high-level and prolonged antigen gene expression at low doses. They can also stimulate specific cellular immunity, making them highly promising in cancer vaccine research. In this review, we summarize the research progress in amplifying mRNA vaccines and provide an outlook of their prospects and future directions in oncotherapy.
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Affiliation(s)
- Chaoying Hu
- Division of Hepatitis and Enterovirus Vaccines, National Institutes for Food and Drug Control, Beijing, China
- National Health Commission (NHC), Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing, China
- National Medical Products Administration (NMPA), Key Laboratory for Quality Research and Evaluation of Biological Products, Institute of Biological Products, National Institutes for Food and Drug Control, Beijing, China
| | - Jianyang Liu
- Division of Hepatitis and Enterovirus Vaccines, National Institutes for Food and Drug Control, Beijing, China
- National Health Commission (NHC), Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing, China
- National Medical Products Administration (NMPA), Key Laboratory for Quality Research and Evaluation of Biological Products, Institute of Biological Products, National Institutes for Food and Drug Control, Beijing, China
| | - Feiran Cheng
- Division of Hepatitis and Enterovirus Vaccines, National Institutes for Food and Drug Control, Beijing, China
- National Health Commission (NHC), Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing, China
- National Medical Products Administration (NMPA), Key Laboratory for Quality Research and Evaluation of Biological Products, Institute of Biological Products, National Institutes for Food and Drug Control, Beijing, China
| | - Yu Bai
- Division of Hepatitis and Enterovirus Vaccines, National Institutes for Food and Drug Control, Beijing, China
- National Health Commission (NHC), Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing, China
- National Medical Products Administration (NMPA), Key Laboratory for Quality Research and Evaluation of Biological Products, Institute of Biological Products, National Institutes for Food and Drug Control, Beijing, China
| | - Qunying Mao
- Division of Hepatitis and Enterovirus Vaccines, National Institutes for Food and Drug Control, Beijing, China
- National Health Commission (NHC), Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing, China
- National Medical Products Administration (NMPA), Key Laboratory for Quality Research and Evaluation of Biological Products, Institute of Biological Products, National Institutes for Food and Drug Control, Beijing, China
| | - Miao Xu
- Division of Hepatitis and Enterovirus Vaccines, National Institutes for Food and Drug Control, Beijing, China
- National Health Commission (NHC), Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing, China
- National Medical Products Administration (NMPA), Key Laboratory for Quality Research and Evaluation of Biological Products, Institute of Biological Products, National Institutes for Food and Drug Control, Beijing, China
| | - Zhenglun Liang
- Division of Hepatitis and Enterovirus Vaccines, National Institutes for Food and Drug Control, Beijing, China
- National Health Commission (NHC), Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing, China
- National Medical Products Administration (NMPA), Key Laboratory for Quality Research and Evaluation of Biological Products, Institute of Biological Products, National Institutes for Food and Drug Control, Beijing, China
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Mono-ADP-ribosylation by PARP10 inhibits Chikungunya virus nsP2 proteolytic activity and viral replication. Cell Mol Life Sci 2023; 80:72. [PMID: 36840772 PMCID: PMC9959937 DOI: 10.1007/s00018-023-04717-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 01/28/2023] [Accepted: 01/31/2023] [Indexed: 02/26/2023]
Abstract
Replication of viruses requires interaction with host cell factors and repression of innate immunity. Recent findings suggest that a subset of intracellular mono-ADP-ribosylating PARPs, which are induced by type I interferons, possess antiviral activity. Moreover, certain RNA viruses, including Chikungunya virus (CHIKV), encode mono-ADP-ribosylhydrolases. Together, this suggests a role for mono-ADP-ribosylation (MARylation) in host-virus conflicts, but the relevant substrates have not been identified. We addressed which PARP restricts CHIKV replication and identified PARP10 and PARP12. For PARP10, this restriction was dependent on catalytic activity. Replication requires processing of the non-structural polyprotein nsP1-4 by the protease located in nsP2 and the assembly of the four individual nsP1-nsP4 into a functional replication complex. PARP10 and PARP12 inhibited the production of nsP3, indicating a defect in polyprotein processing. The nsP3 protein encodes a macrodomain with de-MARylation activity, which is essential for replication. In support for MARylation affecting polyprotein processing, de-MARylation defective CHIKV replicons revealed reduced production of nsP2 and nsP3. We hypothesized that MARylation regulates the proteolytic function of nsP2. Indeed, we found that nsP2 is MARylated by PARP10 and, as a consequence, its proteolytic activity was inhibited. NsP3-dependent de-MARylation reactivated the protease. Hence, we propose that PARP10-mediated MARylation prevents polyprotein processing and consequently virus replication. Together, our findings provide a mechanistic explanation for the role of the viral MAR hydrolase in CHIKV replication.
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7
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Ogorek TJ, Golden JE. Advances in the Development of Small Molecule Antivirals against Equine Encephalitic Viruses. Viruses 2023; 15:413. [PMID: 36851628 PMCID: PMC9958955 DOI: 10.3390/v15020413] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/29/2023] [Accepted: 01/30/2023] [Indexed: 02/04/2023] Open
Abstract
Venezuelan, western, and eastern equine encephalitic alphaviruses (VEEV, WEEV, and EEEV, respectively) are arboviruses that are highly pathogenic to equines and cause significant harm to infected humans. Currently, human alphavirus infection and the resulting diseases caused by them are unmitigated due to the absence of approved vaccines or therapeutics for general use. These circumstances, combined with the unpredictability of outbreaks-as exemplified by a 2019 EEE surge in the United States that claimed 19 patient lives-emphasize the risks posed by these viruses, especially for aerosolized VEEV and EEEV which are potential biothreats. Herein, small molecule inhibitors of VEEV, WEEV, and EEEV are reviewed that have been identified or advanced in the last five years since a comprehensive review was last performed. We organize structures according to host- versus virus-targeted mechanisms, highlight cellular and animal data that are milestones in the development pipeline, and provide a perspective on key considerations for the progression of compounds at early and later stages of advancement.
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Affiliation(s)
- Tyler J. Ogorek
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jennifer E. Golden
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705, USA
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8
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Schmidt C, Schnierle BS. Self-Amplifying RNA Vaccine Candidates: Alternative Platforms for mRNA Vaccine Development. Pathogens 2023; 12:138. [PMID: 36678486 PMCID: PMC9863218 DOI: 10.3390/pathogens12010138] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 01/11/2023] [Accepted: 01/12/2023] [Indexed: 01/18/2023] Open
Abstract
The present use of mRNA vaccines against COVID-19 has shown for the first time the potential of mRNA vaccines for infectious diseases. Here we will summarize the current knowledge about improved mRNA vaccines, i.e., the self-amplifying mRNA (saRNA) vaccines. This approach may enhance antigen expression by amplification of the antigen-encoding RNA. RNA design, RNA delivery, and the innate immune responses induced by RNA will be reviewed.
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Affiliation(s)
- Christin Schmidt
- Section AIDS and Newly Emerging Pathogens, Department of Virology, Paul-Ehrlich-Institut, 63225 Langen, Germany
| | - Barbara S. Schnierle
- Section AIDS and Newly Emerging Pathogens, Department of Virology, Paul-Ehrlich-Institut, 63225 Langen, Germany
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9
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Skidmore AM, Bradfute SB. The life cycle of the alphaviruses: From an antiviral perspective. Antiviral Res 2023; 209:105476. [PMID: 36436722 PMCID: PMC9840710 DOI: 10.1016/j.antiviral.2022.105476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 11/18/2022] [Accepted: 11/21/2022] [Indexed: 11/27/2022]
Abstract
The alphaviruses are a widely distributed group of positive-sense, single stranded, RNA viruses. These viruses are largely arthropod-borne and can be found on all populated continents. These viruses cause significant human disease, and recently have begun to spread into new populations, such as the expansion of Chikungunya virus into southern Europe and the Caribbean, where it has established itself as endemic. The study of alphaviruses is an active and expanding field, due to their impacts on human health, their effects on agriculture, and the threat that some pose as potential agents of biological warfare and terrorism. In this systematic review we will summarize both historic knowledge in the field as well as recently published data that has potential to shift current theories in how alphaviruses are able to function. This review is comprehensive, covering all parts of the alphaviral life cycle as well as a brief overview of their pathology and the current state of research in regards to vaccines and therapeutics for alphaviral disease.
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Affiliation(s)
- Andrew M Skidmore
- Center for Global Health, Department of Internal Medicine, University of New Mexico Health Sciences Center, 915 Camino de Salud, IDTC Room 3245, Albuquerque, NM, 87131, USA.
| | - Steven B Bradfute
- Center for Global Health, Department of Internal Medicine, University of New Mexico Health Sciences Center, 915 Camino de Salud, IDTC Room 3330A, Albuquerque, NM, 87131, USA.
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10
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G3BP/Rin-Binding Motifs Inserted into Flexible Regions of nsP2 Support RNA Replication of Chikungunya Virus. J Virol 2022; 96:e0127822. [PMID: 36226983 PMCID: PMC9645214 DOI: 10.1128/jvi.01278-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus. In infected cells, its positive-sense RNA genome is translated into polyproteins that are subsequently processed into four nonstructural proteins (nsP1 to 4), the virus-encoded subunits of the RNA replicase. However, for RNA replication, interactions between nsPs and host proteins are also needed. These interactions are mostly mediated through the intrinsically disordered C-terminal hypervariable domain (HVD) in nsP3. Duplicate FGDF motifs in the HVD are required for interaction with mammalian RasGAP SH3-binding proteins (G3BPs) and their mosquito homolog Rin; these interactions are crucial for CHIKV RNA replication. In this study, we inactivated G3BP/Rin-binding motifs in the HVD and inserted peptides containing either native or inactivated G3BP/Rin-binding motifs into flexible regions of nsP1, nsP2, or nsP4. Insertion of native motifs into nsP1 or nsP2 but not into the C terminus of nsP4 activated CHIKV RNA replication in human cells in a G3BP-dependent manner. In mosquito cells, activation also resulted from the insertion of inactive motifs after residue 8 or 466 in nsP2; however, the effect was significantly larger when the inserted sequence contained native motifs. Nonetheless, CHIKV mutants harboring mutations in the HVD and containing insertions of native motifs in nsP2 were not viable in mosquito cells. In contrast, mutant genomes containing native motifs after residue 466 or 618 in nsP2 replicated in BHK-21 cells, with the latter mutant forming infectious progeny. Thus, the binding of G3BPs to nsP2 can support CHIKV RNA replication and restore the infectivity of viruses lacking G3BP-binding motifs in the HVD of nsP3. IMPORTANCE CHIKV is a reemerging alphavirus that has spread throughout more than 60 countries and is the causative agent of chikungunya fever. No approved drugs or vaccines are available for the treatment or prevention of CHIKV infection. CHIKV replication depends on the ability of its replicase proteins to interact with host cell factors, and a better understanding of host cell factor roles in viral infection will increase our understanding of CHIKV RNA replication and provide new strategies for viral infection attenuation. Here, we demonstrate that the motifs required for the binding of host G3BP/Rin proteins remain functional when transferred from their natural location in nsP3 to different replicase proteins and may enable mutant viruses to complete a full replication cycle. To our knowledge, this is the first demonstration of interaction motifs for crucial host factors being successfully transferred from one replicase protein to another subunit of alphavirus replicase.
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Cherkashchenko L, Rausalu K, Basu S, Alphey L, Merits A. Expression of Alphavirus Nonstructural Protein 2 (nsP2) in Mosquito Cells Inhibits Viral RNA Replication in Both a Protease Activity-Dependent and -Independent Manner. Viruses 2022; 14:v14061327. [PMID: 35746799 PMCID: PMC9228716 DOI: 10.3390/v14061327] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/12/2022] [Accepted: 06/15/2022] [Indexed: 01/02/2023] Open
Abstract
Alphaviruses are positive-strand RNA viruses, mostly being mosquito-transmitted. Cells infected by an alphavirus become resistant to superinfection due to a block that occurs at the level of RNA replication. Alphavirus replication proteins, called nsP1-4, are produced from nonstructural polyprotein precursors, processed by the protease activity of nsP2. Trans-replicase systems and replicon vectors were used to study effects of nsP2 of chikungunya virus and Sindbis virus on alphavirus RNA replication in mosquito cells. Co-expressed wild-type nsP2 reduced RNA replicase activity of homologous virus; this effect was reduced but typically not abolished by mutation in the protease active site of nsP2. Mutations in the replicase polyprotein that blocked its cleavage by nsP2 reduced the negative effect of nsP2 co-expression, confirming that nsP2-mediated inhibition of RNA replicase activity is largely due to nsP2-mediated processing of the nonstructural polyprotein. Co-expression of nsP2 also suppressed the activity of replicases of heterologous alphaviruses. Thus, the presence of nsP2 inhibits formation and activity of alphavirus RNA replicase in protease activity-dependent and -independent manners. This knowledge improves our understanding about mechanisms of superinfection exclusion for alphaviruses and may aid the development of anti-alphavirus approaches.
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Affiliation(s)
- Liubov Cherkashchenko
- Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia; (L.C.); (K.R.)
| | - Kai Rausalu
- Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia; (L.C.); (K.R.)
| | - Sanjay Basu
- The Pirbright Institute, Ash Road, Pirbright GU24 ONF, UK; (S.B.); (L.A.)
| | - Luke Alphey
- The Pirbright Institute, Ash Road, Pirbright GU24 ONF, UK; (S.B.); (L.A.)
| | - Andres Merits
- Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia; (L.C.); (K.R.)
- Correspondence:
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12
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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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13
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da Silva MK, Azevedo AAC, Campos DMDO, de Souto JT, Fulco UL, Oliveira JIN. Computational vaccinology guided design of multi-epitope subunit vaccine against a neglected arbovirus of the Americas. J Biomol Struct Dyn 2022; 41:3321-3338. [PMID: 35285772 DOI: 10.1080/07391102.2022.2050301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Mayaro virus (MAYV) is an arbovirus found in the Americas that can cause debilitating arthritogenic disease. Although it is an emerging virus, the only current approach is vector control, as there are no approved vaccines to prevent MAYV infection nor therapeutics to treat it. In search of an effective vaccine candidate against MAYV, we used immunoinformatics and molecular modeling to attempt to identify promiscuous T-cell epitopes of the nonstructural polyproteins (nsP1, nsP2, nsP3, and nsP4) from 127 MAYV genomes sequenced in the Americas (08 Bolivia, 72 Brazil, 04 French Guiana, 05 Haiti, 20 Peru, 04 Trinidad and Tobago, and 14 Venezuela). For this purpose, consensus sequences of 360 proteins were used to identify short protein sequences that can bind to MHC I class (MHC II). Our analysis revealed 56 potential MHC-I/TCD8+ (29 MHC-II/TCD4+) epitopes, but only 6 (16) TCD8+ (TCD4+) epitopes showed high antigenicity and conservation, non-allergenicity, non-toxicity, and excellent population coverage. Finally, classical and quantum mechanical calculations (QM:MM) were used to improve the quality of the docking calculations, with the QM part of the simulations performed using the density functional theory formalism (DFT). These results provide insights for the advancement of diagnostic platforms, vaccine development, and immunotherapeutic interventions.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Maria Karolaynne da Silva
- Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil
| | | | | | - Janeusa Trindade de Souto
- Departamento de Microbiologia e Parasitologia, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil
| | - Umberto Laino Fulco
- Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil
| | - Jonas Ivan Nobre Oliveira
- Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil
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Ciota AT. Eastern Equine Encephalitis Virus Taxonomy, Genomics, and Evolution. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:14-19. [PMID: 34734630 DOI: 10.1093/jme/tjab079] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Indexed: 06/13/2023]
Abstract
Eastern equine encephalitis virus (EEEV; Togaviridae, Alphavirus) is an arthropod-borne virus (arbovirus) primarily maintained in an enzootic cycle between Culiseta melanura (Coquillett) and passerine birds. EEEV, which has the highest reported case- fatality rate among arbovirus in the Americas, is responsible for sporadic outbreaks in the Eastern and Midwest United States. Infection is associated with severe neurologic disease and mortality in horses, humans, and other vertebrate hosts. Here, we review what is known about EEEV taxonomy, functional genomics, and evolution, and identify gaps in knowledge regarding the role of EEEV genetic diversity in transmission and disease.
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Affiliation(s)
- Alexander T Ciota
- The Arbovirus Laboratory, Wadsworth Center, New York State Department of Health, Slingerlands, NY
- Department of Biomedical Sciences, State University of New York at Albany School of Public Health, Rensselaer, NY
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15
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Teppor M, Žusinaite E, Karo-Astover L, Omler A, Rausalu K, Lulla V, Lulla A, Merits A. Semliki Forest Virus Chimeras with Functional Replicase Modules from Related Alphaviruses Survive by Adaptive Mutations in Functionally Important Hot Spots. J Virol 2021; 95:e0097321. [PMID: 34319778 PMCID: PMC8475518 DOI: 10.1128/jvi.00973-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 07/19/2021] [Indexed: 11/20/2022] Open
Abstract
Alphaviruses (family Togaviridae) include both human pathogens such as chikungunya virus (CHIKV) and Sindbis virus (SINV) and model viruses such as Semliki Forest virus (SFV). The alphavirus positive-strand RNA genome is translated into nonstructural (ns) polyprotein(s) that are precursors for four nonstructural proteins (nsPs). The three-dimensional structures of nsP2 and the N-terminal 2/3 of nsP3 reveal that these proteins consist of several domains. Cleavage of the ns-polyprotein is performed by the strictly regulated protease activity of the nsP2 region. Processing results in the formation of a replicase complex that can be considered a network of functional modules. These modules work cooperatively and should perform the same task for each alphavirus. To investigate functional interactions between replicase components, we generated chimeras using the SFV genome as a backbone. The functional modules corresponding to different parts of nsP2 and nsP3 were swapped with their counterparts from CHIKV and SINV. Although some chimeras were nonfunctional, viruses harboring the CHIKV N-terminal domain of nsP2 or any domain of nsP3 were viable. Viruses harboring the protease part of nsP2, the full-length nsP2 of CHIKV, or the nsP3 macrodomain of SINV required adaptive mutations for functionality. Seven mutations that considerably improved the infectivity of the corresponding chimeric genomes affected functionally important hot spots recurrently highlighted in previous alphavirus studies. These data indicate that alphaviruses utilize a rather limited set of strategies to survive and adapt. Furthermore, functional analysis revealed that the disturbance of processing was the main defect resulting from chimeric alterations within the ns-polyprotein. IMPORTANCE Alphaviruses cause debilitating symptoms and have caused massive outbreaks. There are currently no approved antivirals or vaccines for treating these infections. Understanding the functions of alphavirus replicase proteins (nsPs) provides valuable information for both antiviral drug and vaccine development. The nsPs of all alphaviruses consist of similar functional modules; however, to what extent these are independent in functionality and thus interchangeable among homologous viruses is largely unknown. Homologous domain swapping was used to study the functioning of modules from nsP2 and nsP3 of other alphaviruses in the context of Semliki Forest virus. Most of the introduced substitutions resulted in defects in the processing of replicase precursors that were typically compensated by adaptive mutations that mapped to determinants of polyprotein processing. Understanding the principles of virus survival strategies and identifying hot spot mutations that permit virus adaptation highlight a route to the rapid development of attenuated viruses as potential live vaccine candidates.
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Affiliation(s)
- Mona Teppor
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Eva Žusinaite
- Institute of Technology, University of Tartu, Tartu, Estonia
| | | | - Ailar Omler
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Kai Rausalu
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Valeria Lulla
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Aleksei Lulla
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Andres Merits
- Institute of Technology, University of Tartu, Tartu, Estonia
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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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Small-Molecule Inhibitors of Chikungunya Virus: Mechanisms of Action and Antiviral Drug Resistance. Antimicrob Agents Chemother 2020; 64:AAC.01788-20. [PMID: 32928738 PMCID: PMC7674028 DOI: 10.1128/aac.01788-20] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has spread to more than 60 countries worldwide. CHIKV infection leads to a febrile illness known as chikungunya fever (CHIKF), which is characterized by long-lasting and debilitating joint and muscle pain. CHIKV can cause large-scale epidemics with high attack rates, which substantiates the need for development of effective therapeutics suitable for outbreak containment. In this review, we highlight the different strategies used for developing CHIKV small-molecule inhibitors, ranging from high-throughput cell-based screening to in silico screens and enzymatic assays with purified viral proteins. Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has spread to more than 60 countries worldwide. CHIKV infection leads to a febrile illness known as chikungunya fever (CHIKF), which is characterized by long-lasting and debilitating joint and muscle pain. CHIKV can cause large-scale epidemics with high attack rates, which substantiates the need for development of effective therapeutics suitable for outbreak containment. In this review, we highlight the different strategies used for developing CHIKV small-molecule inhibitors, ranging from high-throughput cell-based screening to in silico screens and enzymatic assays with purified viral proteins. We further discuss the current status of the most promising molecules, including in vitro and in vivo findings. In particular, we focus on describing host and/or viral targets, mode of action, and mechanisms of antiviral drug resistance and associated mutations. Knowledge of the key molecular determinants of drug resistance will aid selection of the most promising antiviral agent(s) for clinical use. For these reasons, we also summarize the available information about drug-resistant phenotypes in Aedes mosquito vectors. From this review, it is evident that more of the active molecules need to be evaluated in preclinical and clinical models to address the current lack of antiviral treatment for CHIKF.
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Bozóki B, Mótyán JA, Hoffka G, Waugh DS, Tőzsér J. Specificity Studies of the Venezuelan Equine Encephalitis Virus Non-Structural Protein 2 Protease Using Recombinant Fluorescent Substrates. Int J Mol Sci 2020; 21:E7686. [PMID: 33081394 PMCID: PMC7593941 DOI: 10.3390/ijms21207686] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 10/13/2020] [Accepted: 10/14/2020] [Indexed: 11/16/2022] Open
Abstract
The non-structural protein 2 (nsP2) of alphavirus Venezuelan equine encephalitis virus (VEEV) is a cysteine protease that is responsible for processing of the viral non-structural polyprotein and is an important drug target owing to the clinical relevance of VEEV. In this study we designed two recombinant VEEV nsP2 constructs to study the effects of an N-terminal extension on the protease activity and to investigate the specificity of the elongated enzyme in vitro. The N-terminal extension was found to have no substantial effect on the protease activity. The amino acid preferences of the VEEV nsP2 protease were investigated on substrates representing wild-type and P5, P4, P2, P1, P1', and P2' variants of Semliki forest virus nsP1/nsP2 cleavage site, using a His6-MBP-mEYFP recombinant substrate-based protease assay which has been adapted for a 96-well plate-based format. The structural basis of enzyme specificity was also investigated in silico by analyzing a modeled structure of VEEV nsP2 complexed with oligopeptide substrate. To our knowledge, in vitro screening of P1' amino acid preferences of VEEV nsP2 protease remains undetermined to date, thus, our results may provide valuable information for studies and inhibitor design of different alphaviruses or other Group IV viruses.
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Affiliation(s)
- Beáta Bozóki
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (B.B.); (G.H.)
- Doctoral School of Molecular Cell and Immune Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - János András Mótyán
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (B.B.); (G.H.)
| | - Gyula Hoffka
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (B.B.); (G.H.)
- Doctoral School of Molecular Cell and Immune Biology, University of Debrecen, 4032 Debrecen, Hungary
- MTA-DE Laboratory of Protein Dynamics, Department of Biochemistry and Molecular Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - David S. Waugh
- Macromolecular Crystallography Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA;
| | - József Tőzsér
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (B.B.); (G.H.)
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19
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Sensitivity of Alphaviruses to G3BP Deletion Correlates with Efficiency of Replicase Polyprotein Processing. J Virol 2020; 94:JVI.01681-19. [PMID: 31941782 DOI: 10.1128/jvi.01681-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 01/02/2020] [Indexed: 11/20/2022] Open
Abstract
We present a comprehensive overview of the dependency of several Old World alphaviruses for the host protein G3BP. Based on their replication ability in G3BP-deleted cells, Old World alphaviruses can be categorized into two groups, being either resistant or sensitive to G3BP deletion. We observed that all sensitive viruses have an Arg residue at the P4 position of the cleavage site between the nonstructural protein P1 (nsP1) and nsP2 regions of the replicase precursor polyprotein (1/2 site), while a different residue is found at this site in viruses resistant to G3BP deletion. Swapping this residue between resistant and sensitive viruses also switches the G3BP deletion sensitivity. In the absence of G3BP, chikungunya virus (CHIKV) replication is at the limit of detection. The P4 Arg-to-His substitution partially rescues this defect. The P4 residue of the 1/2 site is known to play a regulatory role during processing at this site, and we found that if processing is blocked, the influence of the P4 residue on the sensitivity to G3BP deletion is abolished. Immunofluorescence experiments with CHIKV replicase with manipulated processing indicate that the synthesis of double-stranded RNA is defective in the absence of G3BP and suggest a role of G3BP during negative-strand RNA synthesis. This study provides a functional link between the host protein G3BP and the P4 residue of the 1/2 site for viral RNA replication of Old World alphaviruses. While this suggests a link between G3BP proteins and viral replicase polyprotein processing, we propose that G3BP proteins do not have a regulatory role during polyprotein processing.IMPORTANCE Old World alphaviruses comprise several medically relevant viruses, including chikungunya virus and Ross River virus. Recurrent outbreaks and the lack of antivirals and vaccines demand ongoing research to fight the emergence of these infectious diseases. In this context, a thorough investigation of virus-host interactions is critical. Here, we highlight the importance of the host protein G3BP for several Old World alphaviruses. Our data strongly suggest that G3BP plays a crucial role for the activity of the viral replicase and, thus, the amplification of the viral RNA genome. To our knowledge, the present work is the first to provide a functional link between the regulation of viral polyprotein processing and RNA replication and a host factor for alphaviruses. Moreover, the results of this study raise several questions about the fundamental regulatory mechanisms that dictate the activity of the viral replicase, thereby paving the way for future studies.
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20
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Skidmore AM, Adcock RS, Jonsson CB, Golden JE, Chung DH. Benzamidine ML336 inhibits plus and minus strand RNA synthesis of Venezuelan equine encephalitis virus without affecting host RNA production. Antiviral Res 2020; 174:104674. [PMID: 31816348 PMCID: PMC6935354 DOI: 10.1016/j.antiviral.2019.104674] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 11/27/2019] [Accepted: 12/03/2019] [Indexed: 12/13/2022]
Abstract
Venezuelan equine encephalitis virus (VEEV) is an alphavirus that is endemic to the Americas. VEEV outbreaks occur periodically and cause encephalitis in both humans and equids. There are currently no therapeutics or vaccines for treatment of VEEV in humans. Our group has previously reported on the development of a benzamidine VEEV inhibitor, ML336, which shows potent antiviral activity in both in vitro and in vivo models of infection. In cell culture experiments, ML336 inhibits viral RNA synthesis when added 2-4 h post-infection, and mutations conferring resistance occur within the viral nonstructural proteins (nsP2 and nsP4). We hypothesized that ML336 targets an activity of the viral replicase complex and inhibits viral RNA synthesis. To test this hypothesis, we employed various biochemical and cellular assays. Using structural analogues of ML336, we demonstrate that the cellular antiviral activity of these compounds correlates with their inhibition of viral RNA synthesis. For instance, the IC50 of ML336 for VEEV RNA synthesis inhibition was determined as 1.1 nM, indicating potent anti-RNA synthesis activity in the low nanomolar range. While ML336 efficiently inhibited VEEV RNA synthesis, a much weaker effect was observed against the Old World alphavirus Chikungunya virus (IC50 > 4 μM), agreeing with previous data from a cell based assay. Using a tritium incorporation assay, we demonstrated that there was no significant inhibition of cellular transcription. With a combination of fluorography, strand-specific qRT-PCR, and tritium incorporation, we demonstrated that ML336 inhibits the synthesis of the positive sense genomic, negative sense template, and subgenomic RNAs of VEEV. Based on these results, we propose that the mechanism of action for this class of antiviral compounds is inhibition of viral RNA synthesis through interaction with the viral replicase complex.
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Affiliation(s)
- Andrew M Skidmore
- Department of Microbiology and Immunology, University of Louisville, 505 South Hancock St, Room 642 C, Louisville, KY, USA.
| | - Robert S Adcock
- Center of Predictive Medicine, University of Louisville, 505 South Hancock St, Room 617, Louisville, KY, USA.
| | - Colleen B Jonsson
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, 858 Madison Ave, Room 810 B, Memphis, TN, USA.
| | - Jennifer E Golden
- School of Pharmacy, University of Wisconsin-Madison, 777 Highland Dr, Room 7123, Madison, WI, USA.
| | - Dong-Hoon Chung
- Department of Microbiology and Immunology, University of Louisville, 505 South Hancock St, Room 642 C, Louisville, KY, USA; Center of Predictive Medicine, University of Louisville, 505 South Hancock St, Room 617, Louisville, KY, USA.
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21
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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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22
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Chikungunya virus inhibition by peptidomimetic inhibitors targeting virus-specific cysteine protease. Biochimie 2018; 149:51-61. [DOI: 10.1016/j.biochi.2018.04.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 04/03/2018] [Indexed: 11/19/2022]
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23
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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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Narwal M, Singh H, Pratap S, Malik A, Kuhn RJ, Kumar P, Tomar S. Crystal structure of chikungunya virus nsP2 cysteine protease reveals a putative flexible loop blocking its active site. Int J Biol Macromol 2018; 116:451-462. [PMID: 29730006 DOI: 10.1016/j.ijbiomac.2018.05.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2018] [Revised: 05/01/2018] [Accepted: 05/02/2018] [Indexed: 12/30/2022]
Abstract
Chikungunya virus (CHIKV), a mosquito-borne pathogenic alphavirus is a growing public health threat. No vaccines or antiviral drug is currently available in the market for chikungunya treatment. nsP2pro, the viral cysteine protease, carries out an essential function of nonstructural polyprotein processing and forms four nonstructural proteins (nsPs) that makes the replication complex, hence constitute a promising drug target. In this study, crystal structure of nsP2pro has been determined at 2.59 Å, which reveals that the protein consists of two subdomains: an N-terminal protease subdomain and a C-terminal methyltransferase subdomain. Structural comparison of CHIKV nsP2pro with structures of other alphavirus nsP2 advances that the substrate binding cleft is present at the interface of two subdomains. Additionally, structure insights revealed that access to the active site and substrate binding cleft is blocked by a flexible interdomain loop in CHIKV nsP2pro. This loop contains His548, the catalytic residue, and Trp549 and Asn547, the residues predicted to bind substrate. Interestingly, mutation of Asn547 leads to three-fold increase in Km confirming that Asn547 plays important role in substrate binding and recognition. This study presents the detailed molecular analysis and signifies the substrate specificity residues of CHIKV nsP2pro, which will be beneficial for structure-based drug design and optimization of CHIKV protease inhibitors.
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Affiliation(s)
- Manju Narwal
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India
| | - Harvijay Singh
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India
| | - Shivendra Pratap
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India
| | - Anjali Malik
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India
| | - Richard J Kuhn
- Markey Center for Structural Biology and Purdue Institute for Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN 47907, USA
| | - Pravindra Kumar
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India
| | - Shailly Tomar
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India.
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Singh A, Kumar A, Yadav R, Uversky VN, Giri R. Deciphering the dark proteome of Chikungunya virus. Sci Rep 2018; 8:5822. [PMID: 29643398 PMCID: PMC5895634 DOI: 10.1038/s41598-018-23969-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 03/21/2018] [Indexed: 12/24/2022] Open
Abstract
Chikungunya virus (CHIKV) is a mosquito-borne alphavirus. The outbreak of CHIKV infection has been seen in many tropical and subtropical regions of the biosphere. Current reports evidenced that after outbreaks in 2005-06, the fitness of this virus propagating in Aedes albopictus enhanced due to the epistatic mutational changes in its envelope protein. In our study, we evaluated the prevalence of intrinsically disordered proteins (IDPs) and IDP regions (IDPRs) in CHIKV proteome. IDPs/IDPRs are known as members of a 'Dark Proteome' that defined as a set of polypeptide segments or whole protein without unique three-dimensional structure within the cellular milieu but with significant biological functions, such as cell cycle regulation, control of signaling pathways, and maintenance of viral proteomes. However, the intrinsically disordered aspects of CHIKV proteome and roles of IDPs/IDPRs in the pathogenic mechanism of this important virus have not been evaluated as of yet. There are no existing reports on the analysis of intrinsic disorder status of CHIKV. To fulfil this goal, we have analyzed the abundance and functionality of IDPs/IDPRs in CHIKV proteins, involved in the replication and maturation. It is likely that these IDPs/IDPRs can serve as novel targets for disorder based drug design.
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Affiliation(s)
- Ankur Singh
- School of Basic Sciences, Indian Institute of Technology Mandi, Himachal Pradesh, 175005, India
| | - Ankur Kumar
- School of Basic Sciences, Indian Institute of Technology Mandi, Himachal Pradesh, 175005, India
| | - Rakhi Yadav
- School of Basic Sciences, Indian Institute of Technology Mandi, Himachal Pradesh, 175005, India
| | - Vladimir N Uversky
- Department of Molecular Medicine and Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
- Laboratory of New Methods in Biology, Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
| | - Rajanish Giri
- School of Basic Sciences, Indian Institute of Technology Mandi, Himachal Pradesh, 175005, India.
- BioX Centre, Indian Institute of Technology Mandi, VPO Kamand, 175005, India.
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The Enigmatic Alphavirus Non-Structural Protein 3 (nsP3) Revealing Its Secrets at Last. Viruses 2018; 10:v10030105. [PMID: 29495654 PMCID: PMC5869498 DOI: 10.3390/v10030105] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 02/20/2018] [Accepted: 02/22/2018] [Indexed: 12/21/2022] Open
Abstract
Alphaviruses encode 4 non-structural proteins (nsPs), most of which have well-understood functions in capping and membrane association (nsP1), polyprotein processing and RNA helicase activity (nsP2) and as RNA-dependent RNA polymerase (nsP4). The function of nsP3 has been more difficult to pin down and it has long been referred to as the more enigmatic of the nsPs. The protein comprises three domains, an N-terminal macro domain, a central zinc-binding domain and a C-terminal hypervariable domain (HVD). In this article, we review old and new literature about the functions of the three domains. Much progress in recent years has contributed to a picture of nsP3, particularly through its HVD as a hub for interactions with host cell molecules, with multiple effects on the biology of the host cell at early points in infection. These and many future discoveries will provide targets for anti-viral therapies as well as strategies for modification of vectors for vaccine and oncolytic interventions.
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27
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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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Dhindwal S, Kesari P, Singh H, Kumar P, Tomar S. Conformer and pharmacophore based identification of peptidomimetic inhibitors of chikungunya virus nsP2 protease. J Biomol Struct Dyn 2016; 35:3522-3539. [DOI: 10.1080/07391102.2016.1261046] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Sonali Dhindwal
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India
| | - Pooja Kesari
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India
| | - Harvijay Singh
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, India
| | - Pravindra Kumar
- 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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Mathur K, Anand A, Dubey SK, Sanan-Mishra N, Bhatnagar RK, Sunil S. Analysis of chikungunya virus proteins reveals that non-structural proteins nsP2 and nsP3 exhibit RNA interference (RNAi) suppressor activity. Sci Rep 2016; 6:38065. [PMID: 27901124 PMCID: PMC5128919 DOI: 10.1038/srep38065] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 09/21/2016] [Indexed: 12/16/2022] Open
Abstract
RNAi pathway is an antiviral defence mechanism employed by insects that result in degradation of viral RNA thereby curbing infection. Several viruses including flaviviruses encode viral suppressors of RNAi (VSRs) to counteract the antiviral RNAi pathway. Till date, no VSR has been reported in alphaviruses. The present study was undertaken to evaluate chikungunya virus (CHIKV) proteins for RNAi suppressor activity. We systematically analyzed all nine CHIKV proteins for RNAi suppressor activity using Sf21 RNAi sensor cell line based assay. Two non-structural proteins, namely, nsP2 and nsP3 were found to exhibit RNAi suppressor activity. We further validated the findings in natural hosts, namely in Aedes and in mammalian cell lines and further through EMSA and Agrobacterium infiltration in GFP silenced transgenic tobacco plants. Domains responsible for maximum RNAi suppressor activity were also identified within these proteins. RNA binding motifs in these domains were identified and their participation in RNAi suppression evaluated using site directed mutagenesis. Sequence alignment of these motifs across all species of known alphaviruses revealed conservation of these motifs emphasizing on a similar role of action in other species of alphaviruses as well. Further validation of RNAi suppressor activity of these proteins awaits establishment of specific virus infection models.
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Affiliation(s)
- Kalika Mathur
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Abhishek Anand
- Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Sunil Kumar Dubey
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Neeti Sanan-Mishra
- Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Raj K Bhatnagar
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Sujatha Sunil
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
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Chikungunya virus infectivity, RNA replication and non-structural polyprotein processing depend on the nsP2 protease's active site cysteine residue. Sci Rep 2016; 6:37124. [PMID: 27845418 PMCID: PMC5109220 DOI: 10.1038/srep37124] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 10/24/2016] [Indexed: 11/23/2022] Open
Abstract
Chikungunya virus (CHIKV), genus Alphavirus, family Togaviridae, has a positive-stand RNA genome approximately 12 kb in length. In infected cells, the genome is translated into non-structural polyprotein P1234, an inactive precursor of the viral replicase, which is activated by cleavages carried out by the non-structural protease, nsP2. We have characterized CHIKV nsP2 using both cell-free and cell-based assays. First, we show that Cys478 residue in the active site of CHIKV nsP2 is indispensable for P1234 processing. Second, the substrate requirements of CHIKV nsP2 are quite similar to those of nsP2 of related Semliki Forest virus (SFV). Third, substitution of Ser482 residue, recently reported to contribute to the protease activity of nsP2, with Ala has almost no negative effect on the protease activity of CHIKV nsP2. Fourth, Cys478 to Ala as well as Trp479 to Ala mutations in nsP2 completely abolished RNA replication in CHIKV and SFV trans-replication systems. In contrast, trans-replicases with Ser482 to Ala mutation were similar to wild type counterparts. Fifth, Cys478 to Ala as well as Trp479 to Ala mutations in nsP2 abolished the rescue of infectious virus from CHIKV RNA transcripts while Ser482 to Ala mutation had no effect. Thus, CHIKV nsP2 is a cysteine protease.
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Campos-Gomez J, Ahmad F, Rodriguez E, Saeed MF. A novel cell-based assay to measure activity of Venezuelan equine encephalitis virus nsP2 protease. Virology 2016; 496:77-89. [PMID: 27261892 DOI: 10.1016/j.virol.2016.05.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 04/06/2016] [Accepted: 05/16/2016] [Indexed: 11/26/2022]
Abstract
The encephalitic alphaviruses encode nsP2 protease (nsP2pro), which because of its vital role in virus replication, represents an attractive target for therapeutic intervention. To facilitate the discovery of nsP2 inhibitors we have developed a novel assay for quantitative measurement of nsP2pro activity in a cell-based format. The assay is based on a substrate fusion protein consisting of eGFP and Gaussia luciferase (Gluc) linked together by a small peptide containing a VEEV nsp2pro cleavage sequence. The expression of the substrate protein in cells along with recombinant nsP2pro results in cleavage of the substrate protein resulting in extracellular release of free Gluc. The Gluc activity in supernatants corresponds to intracellular nsP2pro-mediated substrate cleavage; thus, providing a simple and convenient way to quantify nsP2pro activity. Here, we demonstrate potential utility of the assay in identification of nsP2pro inhibitors, as well as in investigations related to molecular characterization of nsP2pro.
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Affiliation(s)
- Javier Campos-Gomez
- Department of Infectious Diseases, Drug Discovery Division, Southern Research, Birmingham, AL 35205, United States
| | - Fahim Ahmad
- Department of Infectious Diseases, Drug Discovery Division, Southern Research, Birmingham, AL 35205, United States
| | - Efrain Rodriguez
- Department of Infectious Diseases, Drug Discovery Division, Southern Research, Birmingham, AL 35205, United States
| | - Mohammad F Saeed
- Department of Infectious Diseases, Drug Discovery Division, Southern Research, Birmingham, AL 35205, United States.
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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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Chikungunya nsP2 protease is not a papain-like cysteine protease and the catalytic dyad cysteine is interchangeable with a proximal serine. Sci Rep 2015; 5:17125. [PMID: 26597768 PMCID: PMC4657084 DOI: 10.1038/srep17125] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 10/26/2015] [Indexed: 12/20/2022] Open
Abstract
Chikungunya virus is the pathogenic alphavirus that causes chikungunya fever in humans. In the last decade millions of cases have been reported around the world from Africa to Asia to the Americas. The alphavirus nsP2 protein is multifunctional and is considered to be pivotal to viral replication, as the nsP2 protease activity is critical for proteolytic processing of the viral polyprotein during replication. Classically the alphavirus nsP2 protease is thought to be papain-like with the enzyme reaction proceeding through a cysteine/histidine catalytic dyad. We performed structure-function studies on the chikungunya nsP2 protease and show that the enzyme is not papain-like. Characterization of the catalytic dyad cysteine residue enabled us to identify a nearby serine that is catalytically interchangeable with the dyad cysteine residue. The enzyme retains activity upon alanine replacement of either residue but a replacement of both cysteine and serine residues results in no detectable activity. Protein dynamics appears to allow the use of either the cysteine or the serine residue in catalysis. This switchable dyad residue has not been previously reported for alphavirus nsP2 proteases and would have a major impact on the nsP2 protease as an anti-viral target.
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34
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Mota MTDO, Ribeiro MR, Vedovello D, Nogueira ML. Mayaro virus: a neglected arbovirus of the Americas. Future Virol 2015. [DOI: 10.2217/fvl.15.76] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Mayaro virus is a neglected tropical arbovirus that causes a mild, self-limited febrile syndrome, sometimes accompanied by a highly incapacitating arthralgia. First isolated in Trinidad and Tobago in 1954, it was reported in several countries within the tropical regions of South and Central America. Human infections are accidental spillover of the enzootic cycle. Little epidemiological data are available due to inadequate surveillance and the generic nature of clinical manifestations resulting in the misdiagnosis with other viral fevers. Despite its restricted distribution, Mayaro fever may become a public health issue due to their urbanization potential. Accurate epidemiological data are urgently needed to access the real distribution of this virus guiding public health policies better.
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Affiliation(s)
- Mânlio Tasso de Oliveira Mota
- Faculty of Medicine of São José do Rio Preto (FAMERP),5416 Brigadeiro Faria Lima Avenue, São José do Rio Preto, SP, Brazil, 15090-000
| | - Milene Rocha Ribeiro
- Faculty of Medicine of São José do Rio Preto (FAMERP),5416 Brigadeiro Faria Lima Avenue, São José do Rio Preto, SP, Brazil, 15090-000
| | - Danila Vedovello
- Faculty of Medicine of São José do Rio Preto (FAMERP),5416 Brigadeiro Faria Lima Avenue, São José do Rio Preto, SP, Brazil, 15090-000
| | - Maurício Lacerda Nogueira
- Faculty of Medicine of São José do Rio Preto (FAMERP),5416 Brigadeiro Faria Lima Avenue, São José do Rio Preto, SP, Brazil, 15090-000
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35
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El-labbad EM, Ismail MAH, Abou Ei Ella DA, Ahmed M, Wang F, Barakat KH, Abouzid KAM. Discovery of Novel Peptidomimetics as Irreversible CHIKV NsP2 Protease Inhibitors Using Quantum Mechanical-Based Ligand Descriptors. Chem Biol Drug Des 2015. [DOI: 10.1111/cbdd.12621] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Eman M. El-labbad
- Department of Pharmaceutical Chemistry; Faculty of Pharmacy; Ain Shams University; Abbassia Cairo 11566 Egypt
| | - Mohammed A. H. Ismail
- Department of Pharmaceutical Chemistry; Faculty of Pharmacy; Ain Shams University; Abbassia Cairo 11566 Egypt
| | - Dalal A. Abou Ei Ella
- Department of Pharmaceutical Chemistry; Faculty of Pharmacy; Ain Shams University; Abbassia Cairo 11566 Egypt
| | - Marawan Ahmed
- Faculty of Pharmacy and Pharmaceutical Sciences; University of Alberta; Edmonton AB Canada
| | - Feng Wang
- Molecular Model Discovery Laboratory; Department of Chemistry and Biotechnology; Faculty of Science, Engineering and Technology; Swinburne University of Technology; Melbourne Vic. 3122 Australia
| | - Khaled H. Barakat
- Faculty of Pharmacy and Pharmaceutical Sciences; University of Alberta; Edmonton AB Canada
- LiKaShing Institute of Virology; University of Alberta; Edmonton AB Canada
- LiKaShing Applied Virology Institute; University of Alberta; Edmonton AB Canada
| | - Khaled A. M. Abouzid
- Department of Pharmaceutical Chemistry; Faculty of Pharmacy; Ain Shams University; Abbassia Cairo 11566 Egypt
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36
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Full length and protease domain activity of chikungunya virus nsP2 differ from other alphavirus nsP2 proteases in recognition of small peptide substrates. Biosci Rep 2015; 35:BSR20150086. [PMID: 26182358 PMCID: PMC4445351 DOI: 10.1042/bsr20150086] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 04/13/2015] [Indexed: 02/06/2023] Open
Abstract
Alphavirus nsP2 proteins are multifunctional and essential for viral replication. The protease role of nsP2 is critical for virus replication as only the virus protease activity is used for processing of the viral non-structural polypeptide. Chikungunya virus is an emerging disease problem that is becoming a world-wide health issue. We have generated purified recombinant chikungunya virus nsP2 proteins, both full length and a truncated protease domain from the C-terminus of the nsP2 protein. Enzyme characterization shows that the protease domain alone has different properties compared with the full length nsP2 protease. We also show chikungunya nsP2 protease possesses different substrate specificity to the canonical alphavirus nsP2 polyprotein cleavage specificity. Moreover, the chikungunya nsP2 also appears to differ from other alphavirus nsP2 in its distinctive ability to recognize small peptide substrates. The protease role of alphavirus nsP2 is critical for virus replication as only the virus protease processes the viral non-structural polypeptide. We show chikungunya nsP2 protease possesses different substrate specificity to the canonical alphavirus nsP2 polyprotein cleavage specificity.
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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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38
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Rashad AA, Mahalingam S, Keller PA. Chikungunya virus: emerging targets and new opportunities for medicinal chemistry. J Med Chem 2013; 57:1147-66. [PMID: 24079775 DOI: 10.1021/jm400460d] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Chikungunya virus is an emerging arbovirus that is widespread in tropical regions and is spreading quickly to temperate climates with recent epidemics in Africa and Asia and documented outbreaks in Europe and the Americas. It is having an increasingly major impact on humankind, with potentially life-threatening and debilitating arthritis. There is no treatment available, and only in the past 24 months have lead compounds for development as potential therapeutics been reported. This Perspective discusses the chikungunya virus as a significant, new emerging topic for medicinal chemistry, highlighting the key viral target proteins and their molecular functions that can be used in drug design, as well as the most important ongoing developments for anti-chikungunya virus research. It represents a complete picture of the current medicinal chemistry of chikungunya, supporting the development of chemotherapeutics through drug discovery and design targeting this virus.
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Affiliation(s)
- Adel A Rashad
- Centre for Medicinal Chemistry, School of Chemistry, University of Wollongong , Wollongong, 2522, Australia
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39
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Presentation overrides specificity: probing the plasticity of alphaviral proteolytic activity through mutational analysis. J Virol 2013; 87:10207-20. [PMID: 23864614 DOI: 10.1128/jvi.01485-13] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Semliki Forest virus (genus Alphavirus) is an important model for studying regulated nonstructural (ns) polyprotein processing. In this study, we evaluated the strictness of the previously outlined cleavage rules, accounting for the timing and outcome of each of three cleavages within the ns polyprotein P1234, and assessed the significance of residues P6 to P4 within the cleavage sites using an alanine scanning approach. The processing of the 1/2 and 3/4 sites was most strongly affected following changes in residues P5 and P4, respectively. However, none of the mutations had a detectable effect on the processing of the 2/3 site. An analysis of recombinant viruses bearing combinations of mutations in cleavage sites revealed tolerance toward the cooccurrence of native and mutated cleavage sites within the same polyprotein, suggesting a remarkable plasticity of the protease recognition pocket. Even in a virus in which all of the cleavage sequences were replaced with alanines in the P6, P5, and P4 positions, the processing pattern was largely preserved, without leading to reversion of cleavage site mutations. Instead, the emergence of second-site mutations was identified, among which Q706R/L in nsP2 was confirmed to be associated with the recognition of the P4 position within the modified cleavage sites. Our results imply that the spatial arrangement of the viral replication complex inherently contributes to scissile-site presentation for the protease, alleviating stringent sequence recognition requirements yet ensuring the precision and the correct order of processing events. Obtaining a proper understanding of the consequences of cleavage site manipulations may provide new tools for taming alphaviruses.
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40
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Chen KC, Kam YW, Lin RTP, Ng MML, Ng LFP, Chu JJH. Comparative analysis of the genome sequences and replication profiles of chikungunya virus isolates within the East, Central and South African (ECSA) lineage. Virol J 2013; 10:169. [PMID: 23721429 PMCID: PMC3679931 DOI: 10.1186/1743-422x-10-169] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 05/28/2013] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND A comparative analysis of the genomic and replication profiles of different geographical chikungunya virus (CHIKV) isolates of the East, Central and South African (ECSA) lineage was performed. FINDINGS Analysis of the data revealed the different growth kinetics for the different isolates. Deep genome sequencing analysis further revealed specific amino acid mutations in the viral nsP1, nsP3, nsP4, E1 and E2 proteins in the different isolates. Despite the difference in viral genomic profiles, the virus-induced ultrastructural changes within infected cells remained highly conserved among the different chikungunya virus isolates. CONCLUSIONS These findings provide insights into the genomic and replication profiles of the re-emerging chikungunya virus isolates of the ECSA lineage.
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Affiliation(s)
- Karen Caiyun Chen
- Department of Microbiology, Laboratory of Molecular RNA Virology and Antiviral Strategies, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, MD4, 5 Science Drive 2, Singapore 117597, Singapore
| | - Yiu-Wing Kam
- Singapore Immunology Network, Agency for Science, Technology and Research (A* STAR), 8A Biomedical Grove, #04-06, Immunos, Singapore 138648, Singapore
| | - Raymond Tzer Pin Lin
- National Public Health Laboratory, Communicable Disease Division, Ministry of Health, College of Medicine Building, 16 College Road, Singapore 169854, Singapore
| | - Mary Mah-Lee Ng
- Department of Microbiology, Flavivirology Laboratory, Yong Loo Lin School of Medicine, National University Health System, MD4, 5 Science Drive 2, National University of Singapore, Singapore 117597, Singapore
| | - Lisa FP Ng
- Singapore Immunology Network, Agency for Science, Technology and Research (A* STAR), 8A Biomedical Grove, #04-06, Immunos, Singapore 138648, Singapore
| | - Justin Jang Hann Chu
- Department of Microbiology, Laboratory of Molecular RNA Virology and Antiviral Strategies, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, MD4, 5 Science Drive 2, Singapore 117597, Singapore
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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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Hypervariable domains of nsP3 proteins of New World and Old World alphaviruses mediate formation of distinct, virus-specific protein complexes. J Virol 2012; 87:1997-2010. [PMID: 23221551 DOI: 10.1128/jvi.02853-12] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alphaviruses are a group of single-stranded RNA viruses with genomes of positive polarity. They are divided into two geographically isolated groups: the Old World and the New World alphaviruses. Despite their similar genome organizations and virion structures, they differ in many aspects of pathogenesis and interaction with the host cell. Here we present new data highlighting previously unknown differences between these two groups. We found that nsP3 proteins of Sindbis virus (SINV) and Venezuelan equine encephalitis virus (VEEV) form cytoplasmic complexes with different morphologies and protein compositions. Unlike the amorphous aggregates formed by SINV nsP3 and other Old World alphavirus-specific nsP3s, VEEV nsP3 forms unique, large spherical structures with striking symmetry. Moreover, VEEV nsP3 does not interact with proteins previously identified as major components of SINV nsP3 complexes, such as G3BP1 and G3BP2. Importantly, the morphology of the complexes and the specificity of the interaction with cellular proteins are largely determined by the hypervariable domain (HVD) of nsP3. Replacement of the VEEV nsP3 HVD with the corresponding domain of SINV nsP3 rendered this protein capable of interaction with G3BPs. Conversely, replacement of the SINV nsP3 HVD with that of VEEV abolished SINV nsP3's interaction with G3BPs. The replacement of natural HVDs with those from heterologous viruses did not abrogate virus replication, despite these fragments demonstrating very low levels of sequence identity. Our data suggest that in spite of the differences in morphology and composition of the SINV- and VEEV-specific nsP3 complexes, it is likely that they have similar functions in virus replication and modification of the cellular environment.
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Evasion of the innate immune response: the Old World alphavirus nsP2 protein induces rapid degradation of Rpb1, a catalytic subunit of RNA polymerase II. J Virol 2012; 86:7180-91. [PMID: 22514352 DOI: 10.1128/jvi.00541-12] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The Old World alphaviruses are emerging human pathogens with an ability to cause widespread epidemics. The latest epidemic of Chikungunya virus, from 2005 to 2007, affected over 40 countries in Africa, Asia, and Europe. The Old World alphaviruses are highly cytopathic and known to evade the cellular antiviral response by inducing global inhibition of transcription in vertebrate cells. This function was shown to be mediated by their nonstructural nsP2 protein; however, the detailed mechanism of this phenomenon has remained unknown. Here, we report that nsP2 proteins of Sindbis, Semliki Forest, and Chikungunya viruses inhibit cellular transcription by inducing rapid degradation of Rpb1, a catalytic subunit of the RNAPII complex. This degradation of Rpb1 is independent of the nsP2-associated protease activity, but, instead, it proceeds through nsP2-mediated Rpb1 ubiquitination. This function of nsP2 depends on the integrity of the helicase and S-adenosylmethionine (SAM)-dependent methyltransferase-like domains, and point mutations in either of these domains abolish Rpb1 degradation. We go on to show that complete degradation of Rpb1 in alphavirus-infected cells occurs within 6 h postinfection, before other previously described virus-induced changes in cell physiology, such as apoptosis, autophagy, and inhibition of STAT1 phosphorylation, are detected. Since Rpb1 is a subunit that catalyzes the polymerase reaction during RNA transcription, degradation of Rpb1 plays an indispensable role in blocking the activation of cellular genes and downregulating cellular antiviral response. This indicates that the nsP2-induced degradation of Rpb1 is a critical mechanism utilized by the Old World alphaviruses to subvert the cellular antiviral response.
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Macromolecular assembly-driven processing of the 2/3 cleavage site in the alphavirus replicase polyprotein. J Virol 2011; 86:553-65. [PMID: 22031949 DOI: 10.1128/jvi.05195-11] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Semliki Forest virus (SFV) is a member of the Alphavirus genus, which produces its replicase proteins in the form of a nonstructural (ns) polyprotein precursor P1234. The maturation of the replicase occurs in a temporally controlled manner by protease activity of nsP2. The template preference and enzymatic capabilities of the alphaviral replication complex have a very important connection with its composition, which is irreversibly altered by proteolysis. The final cleavage of the 2/3 site in the ns polyprotein apparently leads to significant rearrangements within the replication complex and thus denotes the "point of no return" for viral replication progression. Numerous studies have devised rules for when and how ns protease acts, but how the alphaviral 2/3 site is recognized remained largely unexplained. In contrast to the other two cleavage sites within the ns polyprotein, the 2/3 site evidently lacks primary sequence elements in the vicinity of the scissile bond sufficient for specific protease recognition. In this study, we sought to investigate the molecular details of the regulation of the 2/3 site processing in the SFV ns polyprotein. We present evidence that correct macromolecular assembly, presumably strengthened by exosite interactions rather than the functionality of the individual nsP2 protease, is the driving force for specific substrate targeting. We conclude that structural elements within the macrodomain of nsP3 are used for precise positioning of a substrate recognition sequence at the catalytic center of the protease and that this process is coordinated by the exact N-terminal end of nsP2, thus representing a unique regulation mechanism used by alphaviruses.
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45
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NTPase and 5'-RNA triphosphatase activities of Chikungunya virus nsP2 protein. PLoS One 2011; 6:e22336. [PMID: 21811589 PMCID: PMC3139623 DOI: 10.1371/journal.pone.0022336] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 06/24/2011] [Indexed: 01/11/2023] Open
Abstract
Chikungunya virus (CHIKV) is an insect borne virus (genus: Alphavirus) which causes acute febrile illness in humans followed by a prolonged arthralgic disease that affects the joints of the extremities. Re-emergence of the virus in the form of outbreaks in last 6-7 years has posed a serious public health problem. CHIKV has a positive sense single stranded RNA genome of about 12,000 nt. Open reading frame 1 of the viral genome encodes a polyprotein precursor, nsP1234, which is processed further into different non structural proteins (nsP1, nsP2, nsP3 and nsP4). Sequence based analyses have shown helicase domain at the N-terminus and protease domain at C-terminus of nsP2. A detailed biochemical analysis of NTPase/RNA helicase and 5'-RNA phosphatase activities of recombinant CHIKV-nsP2T protein (containing conserved NTPase/helicase motifs in the N-terminus and partial papain like protease domain at the C-terminus) was carried out. The protein could hydrolyze all NTPs except dTTP and showed better efficiency for ATP, dATP, GTP and dGTP hydrolysis. ATP was the most preferred substrate by the enzyme. CHIKV-nsP2T also showed 5'-triphosphatase (RTPase) activity that specifically removes the γ-phosphate from the 5' end of RNA. Both NTPase and RTPase activities of the protein were completely dependent on Mg(2+) ions. RTPase activity was inhibited by ATP showing sharing of the binding motif by NTP and RNA. Both enzymatic activities were drastically reduced by mutations in the NTP binding motif (GKT) and co-factor, Mg(2+) ion binding motif (DEXX) suggesting that they have a common catalytic site.
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46
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Russo AT, Malmstrom RD, White MA, Watowich SJ. Structural basis for substrate specificity of alphavirus nsP2 proteases. J Mol Graph Model 2010; 29:46-53. [PMID: 20483643 DOI: 10.1016/j.jmgm.2010.04.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Accepted: 04/18/2010] [Indexed: 11/25/2022]
Abstract
The alphavirus nsP2 protease is essential for correct processing of the alphavirus nonstructural polyprotein (nsP1234) and replication of the viral genome. We have combined molecular dynamics simulations with our structural studies to reveal features of the nsP2 protease catalytic site and S1'-S4 subsites that regulate the specificity of the protease. The catalytic mechanism of the nsP2 protease appears similar to the papain-like cysteine proteases, with the conserved catalytic dyad forming a thiolate-imidazolium ion pair in the nsP2-activated state. Substrate binding likely stabilizes this ion pair. Analysis of bimolecular complexes of Venezuelan equine encephalitis virus (VEEV) nsP2 protease with each of the nsP1234 cleavage sites identified protease residues His(510), Ser(511), His(546) and Lys(706) as critical for cleavage site recognition. Homology modelling and molecular dynamics simulations of diverse alphaviruses and their cognate cleavage site sequences revealed general features of substrate recognition that operate across alphavirus strains as well as strain specific covariance between binding site and cleavage site residues. For instance, compensatory changes occurred in the P3 and S3 subsite residues to maintain energetically favourable complementary binding surfaces. These results help explain how alphavirus nsP2 proteases recognize different cleavage sites within the nonstructural polyprotein and discriminate between closely related cleavage targets.
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Affiliation(s)
- Andrew T Russo
- Department of Biochemistry and Molecular Biology and the Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555-0647, USA
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47
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Jose J, Snyder JE, Kuhn RJ. A structural and functional perspective of alphavirus replication and assembly. Future Microbiol 2009; 4:837-56. [PMID: 19722838 DOI: 10.2217/fmb.09.59] [Citation(s) in RCA: 234] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Alphaviruses are small, spherical, enveloped, positive-sense ssRNA viruses responsible for a considerable number of human and animal diseases. Alphavirus members include Chikungunya virus, Sindbis virus, Semliki Forest virus, the western, eastern and Venezuelan equine encephalitis viruses, and the Ross River virus. Alphaviruses can cause arthritic diseases and encephalitis in humans and animals and continue to be a worldwide threat. The viruses are transmitted by blood-sucking arthropods, and replicate in both arthropod and vertebrate hosts. Alphaviruses form spherical particles (65-70 nm in diameter) with icosahedral symmetry and a triangulation number of four. The icosahedral structures of alphaviruses have been defined to very high resolutions by cryo-electron microscopy and crystallographic studies. In this review, we summarize the major events in alphavirus infection: entry, replication, assembly and budding. We focus on data acquired from structural and functional studies of the alphaviruses. These structural and functional data provide a broader perspective of the virus lifecycle and structure, and allow additional insight into these important viruses.
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Affiliation(s)
- Joyce Jose
- Department of Biological Sciences, Bindley Bioscience Center, Lilly Hall of Life Sciences, 915 West State St., Purdue University, West Lafayette, IN 47907, USA.
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48
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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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Fate of minus-strand templates and replication complexes produced by a p23-cleavage-defective mutant of Sindbis virus. J Virol 2009; 83:8553-64. [PMID: 19515769 DOI: 10.1128/jvi.00056-09] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
SIN2V is an engineered mutant Sindbis virus (SIN) that is unable to process the P23 cleavage site in polyproteins P123 and P1234 that are translated from the genome after its entry into cells. Unlike wild-type (wt) SIN, it caused minus strands to be made continuously and replication-transcription complex (RTC) activity to be unstable (R. Gorchakov, E. Frolova, S. Sawicki, S. Atasheva, D. Sawicki, and I. Frolov, J. Virol. 82:6218-6231, 2008). We examined further the effects of P23 on SIN RNA replication and RTC activity. Continuous minus-strand synthesis by SIN2V produced 250% of wt levels of minus strands but accumulated only 110% of wt levels (0.39 pg, or 2.7 x 10(4) molecules of double-stranded RNA per cell). Because SIN2V-infected cells accumulated only 40% of the minus strands that were made, cells must possess some process to limit RTC accumulation. The loss of activity by SIN2V RTC after translation was inhibited was stochastic and not due to their inherent instability, based on finding that activity was lost without the degradation of the minus-strand templates. In addition to their normal functions, P23 RTCs exhibited the novel phenotype of being unable to switch from making less to making more genomes than subgenomic 26S mRNA at late times during infections. Our results lend credence to the hypothesis that nsP2 (and possibly nsP3) possesses functions other than those needed solely for RTC activity and that it may also act with the host to regulate minus-strand synthesis and the stability of the RTC.
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Peng W, Peltier DC, Larsen MJ, Kirchhoff PD, Larsen SD, Neubig RR, Miller DJ. Identification of thieno[3,2-b]pyrrole derivatives as novel small molecule inhibitors of neurotropic alphaviruses. J Infect Dis 2009; 199:950-7. [PMID: 19239364 DOI: 10.1086/597275] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Neurotropic alphaviruses such as western, eastern, and Venezuelan equine encephalitis viruses cause serious and potentially fatal central nervous system infections in humans and are high-priority potential bioterrorism agents. There are currently no widely available vaccines or licensed therapies for these virulent pathogens. To identify potential novel antiviral drugs, we developed a cell-based assay with a western equine encephalitis virus replicon that expresses a luciferase reporter gene and screened a small molecule diversity library of 51,028 compounds. We identified and validated a thieno[3,2-b]pyrrole compound with a half maximal inhibitory concentration of <10 micromol/L, a selectivity index>20, and potent activity against live virus in cultured neuronal cells. Furthermore, a structure-activity relationship analysis with 20 related compounds identified several with enhanced activity profiles, including 6 with submicromolar half maximal inhibitory concentrations. In conclusion, we have identified a novel class of promising inhibitors with potent activity against virulent neurotropic alphaviruses.
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Affiliation(s)
- Weiping Peng
- Department of Internal Medicine, Center for Chemical Genomics, Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan 48109-5688, USA
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