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Recombinant core proteins of Japanese encephalitis virus as activators of the innate immune response. Virus Genes 2008; 38:10-8. [PMID: 19009340 DOI: 10.1007/s11262-008-0299-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Accepted: 10/27/2008] [Indexed: 10/21/2022]
Abstract
Nitric oxide (NO) has been shown to suppress Japanese encephalitis virus (JEV) RNA synthesis, viral protein accumulation, and virus release from infected cells. In this article, the potential viral structural proteins as the activators of NO product were studied at the molecular level. First, the genomic region encoding the JEV structural proteins was cloned into a prokaryotic expression vector pET for high-level expression. After purification, these JEV recombinant proteins were added to macrophages to examine the productions of NO and pro-inflammatory mediators. In this study, the recombinant core protein, but not envelope (E), could trigger NO and pro-inflammatory mediators (TNF-alpha, IL-6, and IL-12) productions on macrophages. And their effects were about 85-95% relative to LPS-stimulated macrophages in a dose-dependent manner. Meanwhile, the rCore-2D could up regulate promoters of IL-8 and TNF-alpha via EGFP expression in reporter plasmid (IL-8p-EGFP and TNF-alphap-EGFP)-transfected cells by flow cytometric analysis. These results suggest that JEV core protein could regulate pro-inflammatory mediators and NO production, and may play a crucial role in the innate immunity for the host to restrict the initial stage of JEV infection.
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52
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Morrey JD, Siddharthan V, Wang H, Hall JO, Skirpstunas RT, Olsen AL, Nordstrom JL, Koenig S, Johnson S, Diamond MS. West Nile virus-induced acute flaccid paralysis is prevented by monoclonal antibody treatment when administered after infection of spinal cord neurons. J Neurovirol 2008; 14:152-63. [PMID: 18444087 DOI: 10.1080/13550280801958930] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Acute flaccid polio-like paralysis occurs during natural West Nile virus (WNV) infection in a subset of cases in animals and humans. To evaluate the pathology and the possibility for therapeutic intervention, the authors developed a model of acute flaccid paralysis by injecting WNV directly into the sciatic nerve or spinal cord of hamsters. By directly injecting selected sites of the nervous system with WNV, the authors mapped the lesions responsible for hind limb paralysis to the lumbar spinal cord. Immunohistochemical analysis of spinal cord sections from paralyzed hamsters revealed that WNV-infected neurons localized primarily to the ventral motor horn of the gray matter, consistent with the polio-like clinical presentation. Neuronal apoptosis and diminished cell function were identified by TUNEL (terminal deoxynucleotidyl transferase-mediated BrdUTP nick end labeling) and choline acetyltransferase staining, respectively. Administration of hE16, a potently neutralizing humanized anti-WNV monoclonal antibody, 2 to 3 days after direct WNV infection of the spinal cord, significantly reduced paralysis and mortality. Additionally, a single injection of hE16 as late as 5 days after WNV inoculation of the sciatic nerve also prevented paralysis. Overall, these experiments establish that WNV-induced acute flaccid paralysis in hamsters is due to neuronal infection and injury in the lumbar spinal cord and that treatment with a therapeutic antibody prevents paralysis when administered after WNV infection of spinal cord neurons.
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Affiliation(s)
- John D Morrey
- Institute for Antiviral Research, Department of Animal, Dairy, and Veterinary Sciences, Utah State University, Logan, Utah 84322-4700, USA.
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53
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Sangiambut S, Keelapang P, Aaskov J, Puttikhunt C, Kasinrerk W, Malasit P, Sittisombut N. Multiple regions in dengue virus capsid protein contribute to nuclear localization during virus infection. J Gen Virol 2008; 89:1254-1264. [PMID: 18420804 DOI: 10.1099/vir.0.83264-0] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
During infection, the capsid (C) protein of many flaviviruses localizes to the nuclei and nucleoli of several infected cell lines; the underlying basis and significance of C protein nuclear localization remain poorly understood. In this study, double alanine-substitution mutations were introduced into three previously proposed nuclear-localization signals (at positions 6-9, 73-76 and 85-100) of dengue virus C protein, and four viable mutants, c(K6A,K7A), c(K73A,K74A), c(R85A,K86A) and c(R97A,R98A), were generated in a mosquito cell line in which C protein nuclear localization was rarely observed. Indirect immunofluorescence analysis revealed that, whilst C protein was present in the nuclei of PS and Vero cells throughout infection with a dengue serotype 2 parent virus, the substitution mutations in c(K73A,K74A) and c(R85A,K86A) resulted in an elimination of nuclear localization in PS cells and marked reduction in Vero cells. Mutants c(K6A,K7A) and c(R97A,R98A) exhibited reduced nuclear localization at the late period of infection in PS cells only. All four mutants displayed reduced replication in PS, Vero and C6/36 cells, but there was a lack of correlation between nuclear localization and viral growth properties. Distinct dibasic residues within dengue virus C protein, many of which were located on the solvent-exposed side of the C protein homodimer, contribute to its ability to localize to nuclei during virus infection.
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Affiliation(s)
- Sutha Sangiambut
- Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 10700, Thailand
| | - Poonsook Keelapang
- Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - John Aaskov
- School of Life Sciences, Queensland University of Technology, 2 George Street, Brisbane 4001, Australia
| | - Chunya Puttikhunt
- Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 10700, Thailand
| | - Watchara Kasinrerk
- Department of Clinical Immunology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand.,Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 10700, Thailand
| | - Prida Malasit
- Medical Molecular Biology Unit, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.,Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 10700, Thailand
| | - Nopporn Sittisombut
- Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.,Medical Biotechnology Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 10700, Thailand
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54
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Urbanowski MD, Ilkow CS, Hobman TC. Modulation of signaling pathways by RNA virus capsid proteins. Cell Signal 2008; 20:1227-36. [PMID: 18258415 PMCID: PMC7127581 DOI: 10.1016/j.cellsig.2007.12.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Accepted: 12/18/2007] [Indexed: 01/16/2023]
Abstract
Capsid proteins are structural components of virus particles. They are nucleic acid-binding proteins whose main recognized function is to package viral genomes into protective structures called nucleocapsids. Research over the last 10 years indicates that in addition to their role as genome guardians, viral capsid proteins modulate host cell signaling networks. Disruption or alteration of intracellular signaling pathways by viral capsids may benefit replication of the virus by affecting innate immunity and in some cases, may underlie disease progression. In this review, we describe how the capsid proteins from medically relevant RNA viruses interact with host cell signaling pathways.
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Affiliation(s)
| | - Carolina S. Ilkow
- Department of Cell Biology, University of Alberta, Edmonton, Canada T6G 2H7
| | - Tom C. Hobman
- Department of Cell Biology, University of Alberta, Edmonton, Canada T6G 2H7
- Department of Medical Microbiology & Immunology, University of Alberta, Edmonton, Canada T6G 2H7
- Corresponding author. Department of Cell Biology, University of Alberta, Edmonton, Canada T6G 2H7. Tel.: +1 780 492 6485; fax: +1 780 492 0450.
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55
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Sirri V, Urcuqui-Inchima S, Roussel P, Hernandez-Verdun D. Nucleolus: the fascinating nuclear body. Histochem Cell Biol 2007; 129:13-31. [PMID: 18046571 PMCID: PMC2137947 DOI: 10.1007/s00418-007-0359-6] [Citation(s) in RCA: 295] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/06/2007] [Indexed: 11/30/2022]
Abstract
Nucleoli are the prominent contrasted structures of the cell nucleus. In the nucleolus, ribosomal RNAs are synthesized, processed and assembled with ribosomal proteins. RNA polymerase I synthesizes the ribosomal RNAs and this activity is cell cycle regulated. The nucleolus reveals the functional organization of the nucleus in which the compartmentation of the different steps of ribosome biogenesis is observed whereas the nucleolar machineries are in permanent exchange with the nucleoplasm and other nuclear bodies. After mitosis, nucleolar assembly is a time and space regulated process controlled by the cell cycle. In addition, by generating a large volume in the nucleus with apparently no RNA polymerase II activity, the nucleolus creates a domain of retention/sequestration of molecules normally active outside the nucleolus. Viruses interact with the nucleolus and recruit nucleolar proteins to facilitate virus replication. The nucleolus is also a sensor of stress due to the redistribution of the ribosomal proteins in the nucleoplasm by nucleolus disruption. The nucleolus plays several crucial functions in the nucleus: in addition to its function as ribosome factory of the cells it is a multifunctional nuclear domain, and nucleolar activity is linked with several pathologies. Perspectives on the evolution of this research area are proposed.
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Affiliation(s)
- Valentina Sirri
- Nuclei and Cell Cycle, CNRS, Université Paris VI, Université Paris VII, Institut Jacques Monod, 2 place Jussieu, 75251 Paris Cedex 05, France
| | - Silvio Urcuqui-Inchima
- Nuclei and Cell Cycle, CNRS, Université Paris VI, Université Paris VII, Institut Jacques Monod, 2 place Jussieu, 75251 Paris Cedex 05, France
- Grupo de Inmunovirología, Biogénesis, Universidad de Antioquia, Calle 62 No. 52-59, Medellin, Colombia
| | - Pascal Roussel
- Nuclei and Cell Cycle, CNRS, Université Paris VI, Université Paris VII, Institut Jacques Monod, 2 place Jussieu, 75251 Paris Cedex 05, France
| | - Danièle Hernandez-Verdun
- Nuclei and Cell Cycle, CNRS, Université Paris VI, Université Paris VII, Institut Jacques Monod, 2 place Jussieu, 75251 Paris Cedex 05, France
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Hunt TA, Urbanowski MD, Kakani K, Law LMJ, Brinton MA, Hobman TC. Interactions between the West Nile virus capsid protein and the host cell-encoded phosphatase inhibitor, I2PP2A. Cell Microbiol 2007; 9:2756-66. [PMID: 17868381 DOI: 10.1111/j.1462-5822.2007.01046.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The West Nile virus (WNV) capsid protein functions in virus assembly to package genomic RNA into nucleocapsid structures. It is becoming clear, that in addition to their structural roles, capsid proteins of RNA viruses have non-structural functions. For example, the WNV capsid protein has been implicated as a pathogenic determinant. Presumably, many, if not all, of the non-structural functions of this protein involve interactions with host cell-encoded proteins. In the present study, we used affinity purification to isolate human proteins that bind to the WNV capsid protein. One of the capsid binding proteins is I(2)(PP2A), a previously characterized inhibitor of the serine/threonine phosphatase PP2A. Mapping studies revealed that capsid binding site overlaps with the region of I(2)(PP2A) that is required for inhibition of PP2A activity. Moreover, expression of the WNV capsid protein resulted in significantly increased PP2A activity and expected downstream events, such as inhibition of AP1-dependent transcription. Infected cells treated with I(2)(PP2A)-specific siRNAs produced less infectious virus than control siRNA-transfected cells, but this difference was minimal. Together, our data indicate that interactions between WNV capsid and I(2)(PP2A) result in increased PP2A activity. Given the central role of this phosphatase in cellular physiology, capsid/I(2)(PP2A) interactions may yet prove to be important for viral pathogenesis.
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Affiliation(s)
- Tracey A Hunt
- Department of Cell Biology, University of Alberta, 5-14 Medical Sciences Building, Edmonton, AB T6G 2H7, Canada
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57
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Yang MR, Lee SR, Oh W, Lee EW, Yeh JY, Nah JJ, Joo YS, Shin J, Lee HW, Pyo S, Song J. West Nile virus capsid protein induces p53-mediated apoptosis via the sequestration of HDM2 to the nucleolus. Cell Microbiol 2007; 10:165-76. [PMID: 17697133 PMCID: PMC7162166 DOI: 10.1111/j.1462-5822.2007.01027.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The capsid protein of the West Nile virus (WNV) functions as an apoptotic agonist via the induction of mitochondrial dysfunction and the activation of caspases-9 and -3. Here, we have determined that the WNV capsid (WNVCp) is capable of binding to and sequestering HDM2 into the nucleolus. WNVCp was shown to interfere with the formation of the HDM2 and p53 complex, thereby causing the stabilization of p53 and the subsequent induction of its target apoptotic protein, Bax. Whereas WNVCp was capable of inducing the p53-dependent apoptotic process in wild-type mouse embryonic fibroblasts (MEF) or SH-SY5Y cells, it exerted no significant effects on p53-null MEF or on p53-knockdown SH-SY5Y cells. This suggests that WNVCp-mediated apoptosis requires p53. Furthermore, when WNV was transfected into cells, endogenous Hdm2 and WNVCp were able to interact physically. WNVCp expressed in wild-type MEF proved able to induce the translocation of the endogenous Hdm2 into the nucleolus. Consistently, WNV was highly pathogenic in the presence of p53, and was less so in the absence of p53. The results of these studies suggest that the apoptotic mechanism mediated by WNV might occur in accordance in a fashion similar to that of the tumour-suppressing mechanism mediated by ARF.
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Affiliation(s)
- Mi-Ran Yang
- Department of Food Science and Biotechnology, Sungkyunkwan University, Suwon 440-746, Korea
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Mori Y, Yamashita T, Tanaka Y, Tsuda Y, Abe T, Moriishi K, Matsuura Y. Processing of capsid protein by cathepsin L plays a crucial role in replication of Japanese encephalitis virus in neural and macrophage cells. J Virol 2007; 81:8477-87. [PMID: 17553875 PMCID: PMC1951360 DOI: 10.1128/jvi.00477-07] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The flavivirus capsid protein not only is a component of nucleocapsids but also plays a role in viral replication. In this study, we found a small capsid protein in cells infected with Japanese encephalitis virus (JEV) but not in the viral particles. The small capsid protein was shown to be generated by processing with host cysteine protease cathepsin L. An in vitro cleavage assay revealed that cathepsin L cleaves the capsid protein between amino acid residues Lys(18) and Arg(19), which are well conserved among the mosquito-borne flaviviruses. A mutant JEV resistant to the cleavage of the capsid protein by cathepsin L was generated from an infectious cDNA clone of JEV by introducing a substitution in the cleavage site. The mutant JEV exhibited growth kinetics similar to those of the wild-type JEV in monkey (Vero), mosquito (C6/36), and porcine (PK15) cell lines, whereas replication of the mutant JEV in mouse macrophage (RAW264.7) and neuroblastoma (N18) cells was impaired. Furthermore, the neurovirulence and neuroinvasiveness of the mutant JEV to mice were lower than those of the wild-type JEV. These results suggest that the processing of the JEV capsid protein by cathepsin L plays a crucial role in the replication of JEV in neural and macrophage cells, which leads to the pathogenesis of JEV infection.
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Affiliation(s)
- Yoshio Mori
- Department of Molecular Virology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan
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