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Harak C, Lohmann V. Ultrastructure of the replication sites of positive-strand RNA viruses. Virology 2015; 479-480:418-33. [PMID: 25746936 PMCID: PMC7111692 DOI: 10.1016/j.virol.2015.02.029] [Citation(s) in RCA: 114] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 01/06/2015] [Accepted: 02/16/2015] [Indexed: 12/13/2022]
Abstract
Positive strand RNA viruses replicate in the cytoplasm of infected cells and induce intracellular membranous compartments harboring the sites of viral RNA synthesis. These replication factories are supposed to concentrate the components of the replicase and to shield replication intermediates from the host cell innate immune defense. Virus induced membrane alterations are often generated in coordination with host factors and can be grouped into different morphotypes. Recent advances in conventional and electron microscopy have contributed greatly to our understanding of their biogenesis, but still many questions remain how viral proteins capture membranes and subvert host factors for their need. In this review, we will discuss different representatives of positive strand RNA viruses and their ways of hijacking cellular membranes to establish replication complexes. We will further focus on host cell factors that are critically involved in formation of these membranes and how they contribute to viral replication.
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Affiliation(s)
- Christian Harak
- Department of Infectious Diseases, Molecular Virology, University of Heidelberg, Im Neuenheimer Feld 345, D-69120 Heidelberg, Germany
| | - Volker Lohmann
- Department of Infectious Diseases, Molecular Virology, University of Heidelberg, Im Neuenheimer Feld 345, D-69120 Heidelberg, Germany.
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Barroso-González J, García-Expósito L, Puigdomènech I, de Armas-Rillo L, Machado JD, Blanco J, Valenzuela-Fernández A. Viral infection. Commun Integr Biol 2014. [DOI: 10.4161/cib.16716] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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53
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Lin CC, Tsai P, Sun HY, Hsu MC, Lee JC, Wu IC, Tsao CW, Chang TT, Young KC. Apolipoprotein J, a glucose-upregulated molecular chaperone, stabilizes core and NS5A to promote infectious hepatitis C virus virion production. J Hepatol 2014; 61:984-93. [PMID: 24996046 DOI: 10.1016/j.jhep.2014.06.026] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 06/11/2014] [Accepted: 06/19/2014] [Indexed: 12/18/2022]
Abstract
BACKGROUND & AIMS Hepatitis C virus (HCV) infection leads to glucose abnormality. HCV depends on lipid droplets (LDs) and very-low density lipoproteins for assembly/releasing; however, the components and locations for this process remain unidentified. Apolipoprotein J (ApoJ), upregulated by glucose, functions as Golgi chaperone of secreted proteins and resides abundantly in very-low density lipoproteins. This study investigates the interplay between glucose, ApoJ and HCV virion production. METHODS The effects of high glucose on ApoJ expression and HCV production were evaluated with cultivated HuH7.5, primary human hepatocytes, and in treatment naive chronic hepatitis C patients. How ApoJ affects HCV lifecycle was assessed using siRNA knockdown strategy in JFH1 infected and subgenomic replicon cells. The interactions and locations of ApoJ with viral and host components were examined by immunoprecipitation, immunofluorescence and subcellular fractionation experiments. RESULTS HCV infection increased ApoJ expression, which in parallel with HCV infectivity was additionally elevated with high glucose treatment. Serum ApoJ correlated positively with fasting blood glucose concentration and HCV-RNA titre in patients. ApoJ silencing reduced intracellular and extracellular HCV infectivity and extracellular HCV-RNA, but accumulated intracellular HCV-RNA in HCV-infected cells. ApoJ interacted with HCV core and NS5A and stabilized the dual protein complex. HCV infection dispersed cytoplasmic ApoJ from the compact zones of the Golgi to encircle LDs, where co-localization of the core, NS5A, HCV-RNA, subcellular markers for LDs, endoplasmic reticulum (ER), Golgi, and membrane contact sites occurred. CONCLUSIONS ApoJ facilitates infectious HCV particle production via stabilization of core/NS5A, which might surround LDs at the ER-Golgi membrane contact site.
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Affiliation(s)
- Chun-Chieh Lin
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Peiju Tsai
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Hung-Yu Sun
- Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Mei-Chi Hsu
- Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Jin-Ching Lee
- Department of Biotechnology, College of Life Science, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - I-Chin Wu
- Department of Internal Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chiung-Wen Tsao
- Department of Nursing, Chung Hwa University of Medical Technology, Tainan, Taiwan
| | - Ting-Tsung Chang
- Department of Internal Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan; Center of Infectious Disease and Signaling Research, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Kung-Chia Young
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan; Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan; Center of Infectious Disease and Signaling Research, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
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Phosphorylation of hepatitis C virus RNA polymerases ser29 and ser42 by protein kinase C-related kinase 2 regulates viral RNA replication. J Virol 2014; 88:11240-52. [PMID: 25031343 DOI: 10.1128/jvi.01826-14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
UNLABELLED Hepatitis C virus (HCV) nonstructural protein 5B (NS5B), an RNA-dependent RNA polymerase (RdRp), is the key enzyme for HCV RNA replication. We previously showed that HCV RdRp is phosphorylated by protein kinase C-related kinase 2 (PRK2). In the present study, we used biochemical and reverse-genetics approaches to demonstrate that HCV NS5B phosphorylation is crucial for viral RNA replication in cell culture. Two-dimensional phosphoamino acid analysis revealed that PRK2 phosphorylates NS5B exclusively at its serine residues in vitro and in vivo. Using in vitro kinase assays and mass spectrometry, we identified two phosphorylation sites, Ser29 and Ser42, in the Δ1 finger loop region that interacts with the thumb subdomain of NS5B. Colony-forming assays using drug-selectable HCV subgenomic RNA replicons revealed that preventing phosphorylation by Ala substitution at either Ser29 or Ser42 impairs HCV RNA replication. Furthermore, reverse-genetics studies using HCV infectious clones encoding phosphorylation-defective NS5B confirmed the crucial role of these PRK2 phosphorylation sites in viral RNA replication. Molecular-modeling studies predicted that the phosphorylation of NS5B stabilizes the interactions between its Δ1 loop and thumb subdomain, which are required for the formation of the closed conformation of NS5B known to be important for de novo RNA synthesis. Collectively, our results provide evidence that HCV NS5B phosphorylation has a positive regulatory role in HCV RNA replication. IMPORTANCE While the role of RNA-dependent RNA polymerases (RdRps) in viral RNA replication is clear, little is known about their functional regulation by phosphorylation. In this study, we addressed several important questions about the function and structure of phosphorylated hepatitis C virus (HCV) nonstructural protein 5B (NS5B). Reverse-genetics studies with HCV replicons encoding phosphorylation-defective NS5B mutants and analysis of their RdRp activities revealed previously unidentified NS5B protein features related to HCV replication and NS5B phosphorylation. These attributes most likely reflect potential structural changes induced by phosphorylation in the Δ1 finger loop region of NS5B with two identified phosphate acceptor sites, Ser29 and Ser42, which may transiently affect the closed conformation of NS5B. Elucidating the effects of dynamic changes in NS5B phosphorylation status during viral replication and their impacts on RNA synthesis will improve our understanding of the molecular mechanisms of NS5B phosphorylation-mediated regulation of HCV replication.
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Ke PY, Chen SSL. Autophagy in hepatitis C virus-host interactions: potential roles and therapeutic targets for liver-associated diseases. World J Gastroenterol 2014; 20:5773-93. [PMID: 24914338 PMCID: PMC4024787 DOI: 10.3748/wjg.v20.i19.5773] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 01/14/2014] [Accepted: 03/04/2014] [Indexed: 02/06/2023] Open
Abstract
Autophagy is a lysosome-associated, degradative process that catabolizes cytosolic components to recycle nutrients for further use and maintain cell homeostasis. Hepatitis C virus (HCV) is a major cause of chronic hepatitis, which often leads to end-stage liver-associated diseases and is a significant burden on worldwide public health. Emerging lines of evidence indicate that autophagy plays an important role in promoting the HCV life cycle in host cells. Moreover, the diverse impacts of autophagy on a variety of signaling pathways in HCV-infected cells suggest that the autophagic process is required for balancing HCV-host cell interactions and involved in the pathogenesis of HCV-related liver diseases. However, the detailed molecular mechanism underlying how HCV activates autophagy to benefit viral growth is still enigmatic. Additionally, how the autophagic response contributes to disease progression in HCV-infected cells remains largely unknown. Hence, in this review, we overview the interplay between autophagy and the HCV life cycle and propose possible mechanisms by which autophagy may promote the pathogenesis of HCV-associated chronic liver diseases. Moreover, we outline the related studies on how autophagy interplays with HCV replication and discuss the possible implications of autophagy and viral replication in the progression of HCV-induced liver diseases, e.g., steatosis and hepatocellular carcinoma. Finally, we explore the potential therapeutics that target autophagy to cure HCV infection and its related liver diseases.
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WANG HONGLIANG, PERRY JEFFREYW, LAURING ADAMS, NEDDERMANN PETRA, DE FRANCESCO RAFFAELE, TAI ANDREWW. Oxysterol-binding protein is a phosphatidylinositol 4-kinase effector required for HCV replication membrane integrity and cholesterol trafficking. Gastroenterology 2014; 146:1373-85.e1-11. [PMID: 24512803 PMCID: PMC3992183 DOI: 10.1053/j.gastro.2014.02.002] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2013] [Revised: 01/15/2014] [Accepted: 02/03/2014] [Indexed: 01/12/2023]
Abstract
BACKGROUND & AIMS Positive-sense RNA viruses remodel intracellular membranes to generate specialized membrane compartments for viral replication. Several RNA viruses, including poliovirus and hepatitis C virus (HCV), require phosphatidylinositol (PI) 4-kinases for their replication. However, it is not known how PI 4-kinases and their product, PI(4)P, facilitate host membrane reorganization and viral replication. In addition, although the HCV replication compartment, known as the membranous web, is believed to be cholesterol enriched, the mechanisms by which this occurs have not been elucidated. We aimed to identify and characterize a PI 4-kinase effector in HCV replication. METHODS We used a combination of microscopic and biochemical methods to study HCV replication, web morphology, the distribution of intracellular protein and PI(4)P, along with cholesterol trafficking in HCV-infected cells. PI 4-kinase and oxysterol-binding protein (OSBP) were inhibited using RNA interference or small molecules in cells expressing a full-length genotype 1b replicon or infected with the JFH-1 strain of HCV. RESULTS OSBP was required for HCV replication and membranous web integrity. OSBP was recruited to membranous webs in a PI 4-kinase-dependent manner, and both these factors were found to regulate cholesterol trafficking to the web. We also found OSBP to be required for poliovirus infection but dispensable for dengue virus. CONCLUSIONS OSBP is a PI 4-kinase effector in HCV infection, and contributes to the integrity and cholesterol enrichment of the membranous web. OSBP might also be a PI 4-kinase effector in poliovirus infection and could be involved in replication of other viruses that require PI 4-kinases.
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Affiliation(s)
- HONGLIANG WANG
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI
| | - JEFFREY W. PERRY
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI
| | - ADAM S. LAURING
- Division of Infectious Diseases, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI,Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI
| | - PETRA NEDDERMANN
- Virology Program, Istituto Nazionale di Genetica Molecolare (INGM), Milano, Italy
| | | | - ANDREW W. TAI
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI,Division of Gastroenterology, Department of Internal Medicine, Ann Arbor Veterans Administration Health System, Ann Arbor, MI
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Fan X, Xue B, Dolan PT, LaCount DJ, Kurgan L, Uversky VN. The intrinsic disorder status of the human hepatitis C virus proteome. MOLECULAR BIOSYSTEMS 2014; 10:1345-63. [PMID: 24752801 DOI: 10.1039/c4mb00027g] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Many viral proteins or their biologically important regions are disordered as a whole, or contain long disordered regions. These intrinsically disordered proteins/regions do not possess unique structures and possess functions that complement the functional repertoire of "normal" ordered proteins and domains, with many protein functional classes being heavily dependent on the intrinsic disorder. Viruses commonly use these highly flexible regions to invade the host organisms and to hijack various host systems. These disordered regions also help viruses in adapting to their hostile habitats and to manage their economic usage of genetic material. In this article, we focus on the structural peculiarities of proteins from human hepatitis C virus (HCV) and use a wide spectrum of bioinformatics techniques to evaluate the abundance of intrinsic disorder in the completed proteomes of several human HCV genotypes, to analyze the peculiarities of disorder distribution within the individual HCV proteins, and to establish potential roles of the structural disorder in functions of ten HCV proteins. We show that the intrinsic disorder or increased flexibility is not only abundant in these proteins, but is also absolutely necessary for their functions, playing a crucial role in the proteolytic processing of the HCV polyprotein, the maturation of the individual HCV proteins, and being related to the posttranslational modifications of these proteins and their interactions with DNA, RNA, and various host proteins.
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Affiliation(s)
- Xiao Fan
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta AB T6G 2V4, Canada.
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Amini-Bavil-Olyaee S, Choi YJ, Lee JH, Shi M, Huang IC, Farzan M, Jung JU. The antiviral effector IFITM3 disrupts intracellular cholesterol homeostasis to block viral entry. Cell Host Microbe 2014; 13:452-64. [PMID: 23601107 PMCID: PMC3646482 DOI: 10.1016/j.chom.2013.03.006] [Citation(s) in RCA: 267] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 12/04/2012] [Accepted: 03/19/2013] [Indexed: 12/21/2022]
Abstract
Vesicle-membrane-protein-associated protein A (VAPA) and oxysterol-binding protein (OSBP) regulate intracellular cholesterol homeostasis, which is required for many virus infections. During entry, viruses or virus-containing vesicles can fuse with endosomal membranes to mediate the cytosolic release of virions, and alterations in endosomal cholesterol can inhibit this invasion step. We show that the antiviral effector protein interferon-inducible transmembrane protein 3 (IFITM3) interacts with VAPA and prevents its association with OSBP, thereby disrupting intracellular cholesterol homeostasis and inhibiting viral entry. By altering VAPA-OSBP function, IFITM3 induces a marked accumulation of cholesterol in multivesicular bodies and late endosomes, which inhibits the fusion of intraluminal virion-containing vesicles with endosomal membranes and thereby blocks virus release into the cytosol. Consequently, ectopic expression or depletion of the VAPA gene profoundly affects IFITM3-mediated inhibition of viral entry. Thus, IFITM3 disrupts intracellular cholesterol homeostasis to block viral entry, further underscoring the importance of cholesterol in virus infection.
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Affiliation(s)
- Samad Amini-Bavil-Olyaee
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Harlyne J. Norris Cancer Research Tower, 1450 Biggy Street, Los Angeles, CA 90033, USA
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Belema M, Lopez OD, Bender JA, Romine JL, St Laurent DR, Langley DR, Lemm JA, O'Boyle DR, Sun JH, Wang C, Fridell RA, Meanwell NA. Discovery and development of hepatitis C virus NS5A replication complex inhibitors. J Med Chem 2014; 57:1643-72. [PMID: 24621191 DOI: 10.1021/jm401793m] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Lead inhibitors that target the function of the hepatitis C virus (HCV) nonstructural 5A (NS5A) protein have been identified by phenotypic screening campaigns using HCV subgenomic replicons. The demonstration of antiviral activity in HCV-infected subjects by the HCV NS5A replication complex inhibitor (RCI) daclatasvir (1) spawned considerable interest in this mechanistic approach. In this Perspective, we summarize the medicinal chemistry studies that led to the discovery of 1 and other chemotypes for which resistance maps to the NS5A protein and provide synopses of the profiles of many of the compounds currently in clinical trials. We also summarize what is currently known about the NS5A protein and the studies using NS5A RCIs and labeled analogues that are helping to illuminate aspects of both protein function and inhibitor interaction. We conclude with a synopsis of the results of notable clinical trials with HCV NS5A RCIs.
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Affiliation(s)
- Makonen Belema
- Department of Discovery Chemistry, ‡Department of Virology Discovery, and §Department of Computer-Assisted Drug Design, Bristol-Myers Squibb Research and Development , 5 Research Parkway, Wallingford, Connecticut 06492, United States
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60
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Xu G, Xin X, Zheng C. GPS2 is required for the association of NS5A with VAP-A and hepatitis C virus replication. PLoS One 2013; 8:e78195. [PMID: 24223774 PMCID: PMC3817200 DOI: 10.1371/journal.pone.0078195] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 09/09/2013] [Indexed: 01/30/2023] Open
Abstract
Hepatitis C virus (HCV) nonstructural protein 5A (NS5A) is a component of the replication complex associated with various cellular proteins. It has been reported that G protein pathway suppressor 2 (GPS2) is a potential NS5A-binding factor, as identified in a yeast two-hybrid screens of human cDNA library using viral proteins as baits [1]. In this study, we demonstrated the interaction between GPS2 and NS5A in mammalian cells by coimmunoprecipitation analysis and found that both exogenously and endogenously expressed GPS2 interacted with NS5A of genotype 1b and 2a. Mutagenesis study demonstrated that Domain I of NS5A and coiled-coil domain of GPS2 are responsible for the interaction. Knockdown of GPS2 in hepatoma cell lines suppressed the replication of HCV RNA, which can be rescued by the expression of an RNAi-resistant GPS2. Furthermore, overexpression of GPS2 enhanced the association of NS5A with a proviral cellular factor, human vesicle-associated membrane protein-associated protein A (VAP-A), while knockdown of GPS2 disrupted interaction between VAP-A and NS5A. Taken together, our results suggest that GPS2 acts as a bridge between NS5A and VAP-A and is required for efficient HCV replication.
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Affiliation(s)
- Guodong Xu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Xiu Xin
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Congyi Zheng
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
- China Center for Type Culture Collection, Wuhan University, Wuhan, China
- * E-mail:
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Germain MA, Chatel-Chaix L, Gagné B, Bonneil É, Thibault P, Pradezynski F, de Chassey B, Meyniel-Schicklin L, Lotteau V, Baril M, Lamarre D. Elucidating novel hepatitis C virus-host interactions using combined mass spectrometry and functional genomics approaches. Mol Cell Proteomics 2013; 13:184-203. [PMID: 24169621 DOI: 10.1074/mcp.m113.030155] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
More than 170 million people worldwide are infected with the hepatitis C virus (HCV), for which future therapies are expected to rely upon a combination of oral antivirals. For a rapidly evolving virus like HCV, host-targeting antivirals are an attractive option. To decipher the role of novel HCV-host interactions, we used a proteomics approach combining immunoprecipitation of viral-host protein complexes coupled to mass spectrometry identification and functional genomics RNA interference screening of HCV partners. Here, we report the proteomics analyses of protein complexes associated with Core, NS2, NS3/4A, NS4B, NS5A, and NS5B proteins. We identified a stringent set of 98 human proteins interacting specifically with one of the viral proteins. The overlap with previous virus-host interaction studies demonstrates 24.5% shared HCV interactors overall (24/98), illustrating the reliability of the approach. The identified human proteins show enriched Gene Ontology terms associated with the endoplasmic reticulum, transport proteins with a major contribution of NS3/4A interactors, and transmembrane proteins for Core interactors. The interaction network emphasizes a high degree distribution, a high betweenness distribution, and high interconnectivity of targeted human proteins, in agreement with previous virus-host interactome studies. The set of HCV interactors also shows extensive enrichment for known targets of other viruses. The combined proteomic and gene silencing study revealed strong enrichment in modulators of HCV RNA replication, with the identification of 11 novel cofactors among our set of specific HCV partners. Finally, we report a novel immune evasion mechanism of NS3/4A protein based on its ability to affect nucleocytoplasmic transport of type I interferon-mediated signal transducer and activator of transcription 1 nuclear translocation. The study revealed highly stringent association between HCV interactors and their functional contribution to the viral replication cycle and pathogenesis.
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Affiliation(s)
- Marie-Anne Germain
- Institut de Recherche en Immunologie et en Cancérologie (IRIC), Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, Québec H3C 3J7, Canada
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Park IW, Ndjomou J, Wen Y, Liu Z, Ridgway ND, Kao CC, He JJ. Inhibition of HCV replication by oxysterol-binding protein-related protein 4 (ORP4) through interaction with HCV NS5B and alteration of lipid droplet formation. PLoS One 2013; 8:e75648. [PMID: 24069433 PMCID: PMC3775767 DOI: 10.1371/journal.pone.0075648] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 08/20/2013] [Indexed: 12/21/2022] Open
Abstract
Hepatitis C virus (HCV) RNA replication involves complex interactions among the 3’x RNA element within the HCV 3’ untranslated region, viral and host proteins. However, many of the host proteins remain unknown. In this study, we devised an RNA affinity chromatography /2D/MASS proteomics strategy and identified nine putative 3’ X-associated host proteins; among them is oxysterol-binding protein-related protein 4 (ORP4), a cytoplasmic receptor for oxysterols. We determined the relationship between ORP4 expression and HCV replication. A very low level of constitutive ORP4 expression was detected in hepatocytes. Ectopically expressed ORP4 was detected in the endoplasmic reticulum and inhibited luciferase reporter gene expression in HCV subgenomic replicon cells and HCV core expression in JFH-1-infected cells. Expression of ORP4S, an ORP4 variant that lacked the N-terminal pleckstrin-homology domain but contained the C-terminal oxysterol-binding domain also inhibited HCV replication, pointing to an important role of the oxysterol-binding domain in ORP4-mediated inhibition of HCV replication. ORP4 was found to associate with HCV NS5B and its expression led to inhibition of the NS5B activity. ORP4 expression had little effect on intracellular lipid synthesis and secretion, but it induced lipid droplet formation in the context of HCV replication. Taken together, these results demonstrate that ORP4 is a negative regulator of HCV replication, likely via interaction with HCV NS5B in the replication complex and regulation of intracellular lipid homeostasis. This work supports the important role of lipids and their metabolism in HCV replication and pathogenesis.
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Affiliation(s)
- In-Woo Park
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- Center for AIDS Research, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- University of North Texas Health Science Center, Fort Worth, Texas, United States of America
| | - Jean Ndjomou
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Yahong Wen
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, United States of America
| | - Ziqing Liu
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Neale D. Ridgway
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - C. Cheng Kao
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, United States of America
| | - Johnny J. He
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- Center for AIDS Research, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- University of North Texas Health Science Center, Fort Worth, Texas, United States of America
- * E-mail:
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Abstract
Genome replication is a crucial step in the life cycle of any virus. HCV is a positive strand RNA virus and requires a set of nonstructural proteins (NS3, 4A, 4B, 5A, and 5B) as well as cis-acting replication elements at the genome termini for amplification of the viral RNA. All nonstructural proteins are tightly associated with membranes derived from the endoplasmic reticulum and induce vesicular membrane alterations designated the membranous web, harboring the viral replication sites. The viral RNA-dependent RNA polymerase NS5B is the key enzyme of RNA synthesis. Structural, biochemical, and reverse genetic studies have revealed important insights into the mode of action of NS5B and the mechanism governing RNA replication. Although a comprehensive understanding of the regulation of RNA synthesis is still missing, a number of important viral and host determinants have been defined. This chapter summarizes our current knowledge on the role of viral and host cell proteins as well as cis-acting replication elements involved in the biogenesis of the membranous web and in viral RNA synthesis.
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Affiliation(s)
- Volker Lohmann
- Department of Infectious Diseases, University of Heidelberg, Heidelberg, Germany.
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Salloum S, Wang H, Ferguson C, Parton RG, Tai AW. Rab18 binds to hepatitis C virus NS5A and promotes interaction between sites of viral replication and lipid droplets. PLoS Pathog 2013; 9:e1003513. [PMID: 23935497 PMCID: PMC3731246 DOI: 10.1371/journal.ppat.1003513] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 06/07/2013] [Indexed: 12/12/2022] Open
Abstract
Hepatitis C virus (HCV) is a single-stranded RNA virus that replicates on endoplasmic reticulum-derived membranes. HCV particle assembly is dependent on the association of core protein with cellular lipid droplets (LDs). However, it remains uncertain whether HCV assembly occurs at the LD membrane itself or at closely associated ER membranes. Furthermore, it is not known how the HCV replication complex and progeny genomes physically associate with the presumed sites of virion assembly at or near LDs. Using an unbiased proteomic strategy, we have found that Rab18 interacts with the HCV nonstructural protein NS5A. Rab18 associates with LDs and is believed to promote physical interaction between LDs and ER membranes. Active (GTP-bound) forms of Rab18 bind more strongly to NS5A than a constitutively GDP-bound mutant. NS5A colocalizes with Rab18-positive LDs in HCV-infected cells, and Rab18 appears to promote the physical association of NS5A and other replicase components with LDs. Modulation of Rab18 affects genome replication and possibly also the production of infectious virions. Our results support a model in which specific interactions between viral and cellular proteins may promote the physical interaction between membranous HCV replication foci and lipid droplets. Hepatitis C virus (HCV) chronically infects about 170 million people worldwide and can ultimately lead to liver failure and liver cancer. HCV, like other RNA viruses, exploits cellular proteins and membranes to promote their own replication and virion production. In particular, HCV replication occurs at membranes derived from the endoplasmic reticulum, while HCV virion assembly is believed to occur at or near cellular lipid droplets. In this work, we report that Rab18, a lipid droplet-associated cellular protein, binds to the viral protein NS5A, and that the silencing of Rab18 reduces the association of other HCV replication complex components with lipid droplets. These data are consistent with a model in which Rab18 promotes the physical interaction between sites of viral replication to lipid droplets. We also speculate that Rab18 may help to link sites of viral replication to sites of virion assembly. Understanding how viruses exploit cellular proteins may result in new methods of disrupting viral infection.
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Affiliation(s)
- Shadi Salloum
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Hongliang Wang
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Charles Ferguson
- The University of Queensland, Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, Brisbane, Queensland, Australia
| | - Robert G. Parton
- The University of Queensland, Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, Brisbane, Queensland, Australia
| | - Andrew W. Tai
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, United States of America
- Division of Gastroenterology, Department of Internal Medicine, Ann Arbor Veterans Administration Health System, Ann Arbor, Michigan, United States of America
- * E-mail:
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Tani J, Shimamoto S, Mori K, Kato N, Moriishi K, Matsuura Y, Tokumitsu H, Tsuchiya M, Fujimoto T, Kato K, Miyoshi H, Masaki T, Kobayashi R. Ca(2+) /S100 proteins regulate HCV virus NS5A-FKBP8/FKBP38 interaction and HCV virus RNA replication. Liver Int 2013; 33:1008-18. [PMID: 23522085 DOI: 10.1111/liv.12151] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Accepted: 02/22/2013] [Indexed: 12/14/2022]
Abstract
BACKGROUND & AIM FKBP8/FKBP38 is a unique FK506-binding protein with a C-terminal membrane anchor and localizes at the outer membranes of mitochondria and the endoplasmic reticulum. Similar to some immunophilins, such as FKBP51, FKBP52 and Cyclophilin 40, FKBP8/FKBP38 contain a putative Calmodulin-binding domain and a tetratricopeptide-repeat (TPR) domain for the binding of Hsp90. Both Hsp90 and the non-structural protein 5A (NS5A) of the hepatitis C virus (HCV) interact specifically with FKBP8/FKBP38 through its TPR domain, and the ternary complex formation plays a critical role in HCV RNA replication. The goal of this study is to evaluate that the host factor inhibits the ternary complex formation and the replication of HCV in vitro and in vivo. METHODS S100 proteins, FKBP38, FKBP8, HCV NS5A, Hsp90, and calmodulin were expressed in E.coli and purified. In vitro binding studies were performed by GST pull-down, S-tag pull-down and surface plasmon resonance analyses. The effect of S100 proteins on HCV replication was analysed by Western blotting using an HCV NS3 antibody following transfection of S100 proteins into the HCV replicon harbouring cell line (sO cells). RESULTS In vitro binding studies showed that S100A1, S100A2, S100A6, S100B and S100P directly interacted with FKBP8/FKBP38 in a Ca(2+) -dependent manner and inhibited the FKBP8/FKBP38-Hsp90 and FKBP8/FKBP38-NS5A interactions. Furthermore, overexpression of S100A1, S100A2 and S100A6 in sO cells resulted in the efficient inhibition of HCV replication. CONCLUSION The association of the S100 proteins with FKBP8/FKBP38 provides a novel Ca(2+) -dependent regulatory role in HCV replication through the NS5A-host protein interaction.
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Affiliation(s)
- Joji Tani
- Department of Gastroenterology and Neurology, Kagawa University Faculty of Medicine, Kagawa, Japan
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66
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Morphological and biochemical characterization of the membranous hepatitis C virus replication compartment. J Virol 2013; 87:10612-27. [PMID: 23885072 DOI: 10.1128/jvi.01370-13] [Citation(s) in RCA: 199] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Like all other positive-strand RNA viruses, hepatitis C virus (HCV) induces rearrangements of intracellular membranes that are thought to serve as a scaffold for the assembly of the viral replicase machinery. The most prominent membranous structures present in HCV-infected cells are double-membrane vesicles (DMVs). However, their composition and role in the HCV replication cycle are poorly understood. To gain further insights into the biochemcial properties of HCV-induced membrane alterations, we generated a functional replicon containing a hemagglutinin (HA) affinity tag in nonstructural protein 4B (NS4B), the supposed scaffold protein of the viral replication complex. By using HA-specific affinity purification we isolated NS4B-containing membranes from stable replicon cells. Complementing biochemical and electron microscopy analyses of purified membranes revealed predominantly DMVs, which contained viral proteins NS3 and NS5A as well as enzymatically active viral replicase capable of de novo synthesis of HCV RNA. In addition to viral factors, co-opted cellular proteins, such as vesicle-associated membrane protein-associated protein A (VAP-A) and VAP-B, that are crucial for viral RNA replication, as well as cholesterol, a major structural lipid of detergent-resistant membranes, are highly enriched in DMVs. Here we describe the first isolation and biochemical characterization of HCV-induced DMVs. The results obtained underline their central role in the HCV replication cycle and suggest that DMVs are sites of viral RNA replication. The experimental approach described here is a powerful tool to more precisely define the molecular composition of membranous replication factories induced by other positive-strand RNA viruses, such as picorna-, arteri- and coronaviruses.
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67
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Sato A, Saito Y, Sugiyama K, Sakasegawa N, Muramatsu T, Fukuda S, Yoneya M, Kimura M, Ebinuma H, Hibi T, Ikeda M, Kato N, Saito H. Suppressive effect of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) on hepatitis C virus replication. J Cell Biochem 2013; 114:1987-96. [DOI: 10.1002/jcb.24541] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 03/05/2013] [Indexed: 01/16/2023]
Affiliation(s)
- Ayami Sato
- Division of Pharmacotherapeutics; Keio University Faculty of Pharmacy; Tokyo; 1058512; Japan
| | | | - Kazuo Sugiyama
- Department of Internal Medicine; Keio University School of Medicine; Tokyo; 1608582; Japan
| | - Noriko Sakasegawa
- Division of Pharmacotherapeutics; Keio University Faculty of Pharmacy; Tokyo; 1058512; Japan
| | - Toshihide Muramatsu
- Division of Pharmacotherapeutics; Keio University Faculty of Pharmacy; Tokyo; 1058512; Japan
| | - Shinya Fukuda
- Division of Pharmacotherapeutics; Keio University Faculty of Pharmacy; Tokyo; 1058512; Japan
| | - Mikiko Yoneya
- Division of Pharmacotherapeutics; Keio University Faculty of Pharmacy; Tokyo; 1058512; Japan
| | - Masaki Kimura
- Division of Pharmacotherapeutics; Keio University Faculty of Pharmacy; Tokyo; 1058512; Japan
| | - Hirotoshi Ebinuma
- Department of Internal Medicine; Keio University School of Medicine; Tokyo; 1608582; Japan
| | - Toshifumi Hibi
- Department of Internal Medicine; Keio University School of Medicine; Tokyo; 1608582; Japan
| | - Masanori Ikeda
- Department of Molecular Biology; Okayama University Graduate School of Medicine and Dentistry; Okayama; 7008558; Japan
| | - Nobuyuki Kato
- Department of Molecular Biology; Okayama University Graduate School of Medicine and Dentistry; Okayama; 7008558; Japan
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68
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Tripathi LP, Kambara H, Chen YA, Nishimura Y, Moriishi K, Okamoto T, Morita E, Abe T, Mori Y, Matsuura Y, Mizuguchi K. Understanding the Biological Context of NS5A–Host Interactions in HCV Infection: A Network-Based Approach. J Proteome Res 2013; 12:2537-51. [DOI: 10.1021/pr3011217] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Lokesh P. Tripathi
- National Institute of Biomedical Innovation, 7-6-8 Saito Asagi, Ibaraki,
Osaka, 567-0085, Japan
| | - Hiroto Kambara
- Department of Molecular Virology,
Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Yi-An Chen
- National Institute of Biomedical Innovation, 7-6-8 Saito Asagi, Ibaraki,
Osaka, 567-0085, Japan
| | - Yorihiro Nishimura
- Department of Molecular Virology,
Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Kohji Moriishi
- Department of Molecular Virology,
Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Toru Okamoto
- Department of Molecular Virology,
Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Eiji Morita
- Department of Molecular Virology,
Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Takayuki Abe
- Department of Molecular Virology,
Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Yoshio Mori
- Department of Molecular Virology,
Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Yoshiharu Matsuura
- Department of Molecular Virology,
Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-Oka, Suita, Osaka, 565-0871, Japan
| | - Kenji Mizuguchi
- National Institute of Biomedical Innovation, 7-6-8 Saito Asagi, Ibaraki,
Osaka, 567-0085, Japan
- Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamada-Oka, Suita, Osaka, 565-0871,
Japan
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69
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Abstract
Hepatitis C virus (HCV) exhibits a narrow host range and a specific tissue tropism. Studies on HCV life cycle have been progressed by the developments of in vitro replication and infection systems and an HCV laboratory strain (HCVcc) capable of propagating in human hepatoma cell line, Huh7 cells. Mice expressing four human entry receptor candidates for HCV permit entry of HCVcc, therefore tissue tropism of HCV was believed to be rely on the expression of the entry receptors. However, HCV infection is often associated with extra-hepatic manifestations and the determinants for cell tropism of HCV remain elusive. Recently, we have shown that several nonhepatic cell lines permit HCV-RNA replication through an expression of a liver-specific microRNA, miR-122, upon infection with HCVcc, while no infectious particle was produced. In the nonhepatic cells, only small numbers of lipid droplets and low levels of VLDL-associated proteins were observed in compared with Huh7 cells, suggesting that expression of miR-122 and functional lipid metabolism participates in the replication and assembly of HCVcc, respectively In this review, we would like to discuss about involvement of miR-122 and functional lipid metabolism in the determination of HCV cell tropism.
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70
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Regulation of hepatitis C virus replication by nuclear translocation of nonstructural 5A protein and transcriptional activation of host genes. J Virol 2013; 87:5523-39. [PMID: 23468497 DOI: 10.1128/jvi.00585-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Hepatitis C virus (HCV) nonstructural protein 5A (NS5A) is involved in regulating viral replication through its direct interaction with the HCV RNA-dependent RNA polymerase. NS5A also alters infected cell metabolism through complex interactions with numerous host cell proteins. NS5A has furthermore been suggested to act as a transcriptional activator, although the impact on viral replication is unclear. To study this, HCV NS5A variants were amplified from hepatic tissue from an HCV-infected patient, and their abilities to activate gene transcription were analyzed in a single-hybrid yeast (Saccharomyces cerevisiae) model. Different variants isolated from the same patient displayed different transactivational activities. When these variants were inserted into the HCV subgenomic replicon system, they demonstrated various levels of RNA replication, which correlated with their transactivational activities. We showed that the C-terminal fragment of NS5A was localized to the nucleus and that a functional NS5A nuclear localization signal and cellular caspase activity were required for this process. Furthermore, nuclear localization of NS5A was necessary for viral replication. Finally, we demonstrate that nuclear NS5A binds to host cell promoters of several genes previously identified as important for efficient HCV RNA replication, inducing their transcription. Taken together, these results demonstrate a new mechanism by which HCV modulates its cellular environment, thereby enhancing viral replication.
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71
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Abstract
Hepatitis C virus (HCV) exhibits a narrow host range and a specific tissue tropism. Mice expressing major entry receptors for HCV permit viral entry, and therefore the species tropism of HCV infection is considered to be reliant on the expression of the entry receptors. However, HCV receptor candidates are expressed and replication of HCV-RNA can be detected in several nonhepatic cell lines, suggesting that nonhepatic cells are also susceptible to HCV infection. Recently it was shown that the exogenous expression of a liver-specific microRNA, miR-122, facilitated the efficient replication of HCV not only in hepatic cell lines, including Hep3B and HepG2 cells, but also in nonhepatic cell lines, including Hec1B and HEK-293T cells, suggesting that miR-122 is required for the efficient replication of HCV in cultured cells. However, no infectious particle was detected in the nonhepatic cell lines, in spite of the efficient replication of HCV-RNA. In the nonhepatic cells, only small numbers of lipid droplets and low levels of very-low-density lipoprotein-associated proteins were observed compared with findings in the hepatic cell lines, suggesting that functional lipid metabolism participates in the assembly of HCV. Taken together, these findings indicate that miR-122 and functional lipid metabolism are involved in the tissue tropism of HCV infection. In this review, we would like to focus on the role of miR-122 and lipid metabolism in the cell tropism of HCV.
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72
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Xu S, Pei R, Guo M, Han Q, Lai J, Wang Y, Wu C, Zhou Y, Lu M, Chen X. Cytosolic phospholipase A2 gamma is involved in hepatitis C virus replication and assembly. J Virol 2012; 86:13025-37. [PMID: 23015700 PMCID: PMC3497680 DOI: 10.1128/jvi.01785-12] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Similar to other positive-sense, single-stranded RNA viruses, hepatitis C virus (HCV) replicates its genome in a remodeled intracellular membranous structure known as the membranous web (MW). To date, the process of MW formation remains unclear. It is generally acknowledged that HCV nonstructural protein 4B (NS4B) can induce MW formation through interaction with the cytosolic endoplasmic reticulum (ER) membrane. Many host proteins, such as phosphatidylinositol 4-kinase IIIα (PI4KIIIα), have been identified as critical factors required for this process. We now report a new factor, the cytosolic phospholipase A2 gamma (PLA2G4C), which contributes to MW formation, HCV replication, and assembly. The PLA2G4C gene was identified as a host gene with upregulated expression upon HCV infection. Knockdown of PLA2G4C in HCV-infected cells or HCV replicon-containing cells by small interfering RNA (siRNA) significantly suppressed HCV replication and assembly. In addition, the chemical inhibitor methyl arachidonyl fluorophosphonate (MAFP), which specifically inhibits PLA2, reduced HCV replication and assembly. Electron microscopy demonstrated that MW structure formation was defective after PLA2G4C knockdown in HCV replicon-containing cells. Further analysis by immunostaining and immunoprecipitation assays indicated that PLA2G4C colocalized with the HCV proteins NS4B and NS5A in cells infected with JFH-1 and interacted with NS4B. In addition, PLA2G4C was able to transport the HCV nonstructural proteins from replication sites to lipid droplets, the site for HCV assembly. These data suggest that PLA2G4C plays an important role in the HCV life cycle and might represent a potential target for anti-HCV therapy.
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Affiliation(s)
- Song Xu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
- Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Rongjuan Pei
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Min Guo
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
- Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Qingxia Han
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Juan Lai
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
- Graduate School of the Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Yun Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Chunchen Wu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Yuan Zhou
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Mengji Lu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
- Institute of Virology, University Hospital of Essen, Essen, Germany
| | - Xinwen Chen
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China
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Rosnoblet C, Fritzinger B, Legrand D, Launay H, Wieruszeski JM, Lippens G, Hanoulle X. Hepatitis C virus NS5B and host cyclophilin A share a common binding site on NS5A. J Biol Chem 2012; 287:44249-60. [PMID: 23152499 DOI: 10.1074/jbc.m112.392209] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Nonstructural protein 5B (NS5B) is essential for hepatitis C virus (HCV) replication as it carries the viral RNA-dependent RNA polymerase enzymatic activity. HCV replication occurs in a membrane-associated multiprotein complex in which HCV NS5A and host cyclophilin A (CypA) have been shown to be present together with the viral polymerase. We used NMR spectroscopy to perform a per residue level characterization of the molecular interactions between the unfolded domains 2 and 3 of NS5A (NS5A-D2 and NS5A-D3), CypA, and NS5B(Δ21). We show that three regions of NS5A-D2 (residues 250-262 (region A), 274-287 (region B), and 306-333 (region C)) interact with NS5B(Δ21), whereas NS5A-D3 does not. We show that both NS5B(Δ21) and CypA share a common binding site on NS5A that contains residues Pro-306 to Glu-323. No direct molecular interaction has been detected by NMR spectroscopy between HCV NS5B(Δ21) and host CypA. We show that cyclosporine A added to a sample containing NS5B(Δ21), NS5A-D2, and CypA specifically inhibits the interaction between CypA and NS5A-D2 without altering the one between NS5A-D2 and NS5B(Δ21). A high quality heteronuclear NMR spectrum of HCV NS5B(Δ21) has been obtained and was used to characterize the binding site on the polymerase of NS5A-D2. Moreover these data highlight the potential of using NMR of NS5B(Δ21) as a powerful tool to characterize in solution the interactions of the HCV polymerase with all kinds of molecules (proteins, inhibitors, RNA). This work brings new insights into the comprehension of the molecular interplay between NS5B, NS5A, and CypA, three essentials proteins for HCV replication.
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74
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Japanese encephalitis virus core protein inhibits stress granule formation through an interaction with Caprin-1 and facilitates viral propagation. J Virol 2012; 87:489-502. [PMID: 23097442 DOI: 10.1128/jvi.02186-12] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Stress granules (SGs) are cytoplasmic foci composed of stalled translation preinitiation complexes induced by environmental stress stimuli, including viral infection. Since viral propagation completely depends on the host translational machinery, many viruses have evolved to circumvent the induction of SGs or co-opt SG components. In this study, we found that expression of Japanese encephalitis virus (JEV) core protein inhibits SG formation. Caprin-1 was identified as a binding partner of the core protein by an affinity capture mass spectrometry analysis. Alanine scanning mutagenesis revealed that Lys(97) and Arg(98) in the α-helix of the JEV core protein play a crucial role in the interaction with Caprin-1. In cells infected with a mutant JEV in which Lys(97) and Arg(98) were replaced with alanines in the core protein, the inhibition of SG formation was abrogated, and viral propagation was impaired. Furthermore, the mutant JEV exhibited attenuated virulence in mice. These results suggest that the JEV core protein circumvents translational shutoff by inhibiting SG formation through an interaction with Caprin-1 and facilitates viral propagation in vitro and in vivo.
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75
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Small molecule inhibitors of the hepatitis C virus-encoded NS5A protein. Virus Res 2012; 170:1-14. [PMID: 23009750 DOI: 10.1016/j.virusres.2012.09.007] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 09/13/2012] [Accepted: 09/13/2012] [Indexed: 12/20/2022]
Abstract
Hepatitis C virus (HCV) is a modern-day pandemic; 2-3% of the world's population are thought to be infected with the virus and are subsequently at risk of developing end-stage liver diseases. The traditional standard of care (SOC) for HCV-infected patients has been limited to a regimen of pegylated-interferon alpha (pegIFN) and ribavirin; displaying low cure rates in a majority of patients and severe side effects. However, in 2011 the first direct-acting antivirals (DAA) were licensed to treat HCV-infected patients in combination with SOC, which served to elevate treatment response rates. The HCV drug development pipeline is currently populated with many additional and improved DAAs; primarily molecules that target the virus-encoded protease or polymerase enzymes. These molecules are being evaluated both in combination with the traditional SOC and together with other DAAs as all-oral pegIFN-free regimens with the ultimate goal of developing multiple DAA-containing HCV therapies that do not rely on an pegIFN backbone. A recent addition to the arsenal of HCV inhibitors in development is represented by an entirely new DAA class; molecules that target the HCV-encoded non-enzymatic NS5A protein. NS5A is essential for HCV propagation and, although its actual functions are largely unknown, it is likely a key regulator of viral genome replication and virion assembly. The protein is exquisitely sensitive to small molecule-mediated inhibition; NS5A-targeting molecules are probably the most potent antiviral molecules ever discovered and exhibit a number of other attractive drug-like properties, including activity against many HCV genotypes/subtypes and once-daily dosing potential. Although their mechanism of action is unclear, NS5A-targeting molecules are already proving their utility in clinical evaluation; particularly as components of pegIFN-sparring DAA combination regimens. This review will aim to amalgamate our current understanding and knowledge of NS5A-targeting molecules; their discovery, properties, applications, and insight into their future impact as components of all-oral pegIFN-free DAA combination therapies to combat HCV infection.
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76
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Chatel-Chaix L, Germain MA, Götte M, Lamarre D. Direct-acting and host-targeting HCV inhibitors: current and future directions. Curr Opin Virol 2012; 2:588-98. [PMID: 22959589 DOI: 10.1016/j.coviro.2012.08.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 08/07/2012] [Indexed: 02/07/2023]
Abstract
The inclusion of NS3 protease inhibitors to the interferon-containing standard of care improved sustained viral response rates in hepatitis C virus (HCV) infected patients. However, there is still an unmet medical need as this drug regimen is poorly tolerated and lacks efficacy, especially in difficult-to-treat patients. Intense drug discovery and development efforts have focused on direct-acting antivirals (DAA) that target NS3 protease, NS5B polymerase and the NS5A protein. DAA combinations are currently assessed in clinical trials. Alternative antivirals have emerged that target host machineries co-opted by HCV. Finally, continuous and better understanding of HCV biology allows speculating on the value of novel classes of DAA required in future personalized all-oral interferon-free combination therapy and for supporting global disease eradication.
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Affiliation(s)
- Laurent Chatel-Chaix
- Institut de Recherche en Immunologie et en Cancérologie (IRIC), Montréal, Québec H3T 1J4, Canada
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77
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Liu HM, Aizaki H, Machida K, Ou JHJ, Lai MMC. Hepatitis C virus translation preferentially depends on active RNA replication. PLoS One 2012; 7:e43600. [PMID: 22937067 PMCID: PMC3427374 DOI: 10.1371/journal.pone.0043600] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 07/26/2012] [Indexed: 12/19/2022] Open
Abstract
Hepatitis C virus (HCV) RNA initiates its replication on a detergent-resistant membrane structure derived from the endoplasmic reticulum (ER) in the HCV replicon cells. By performing a pulse-chase study of BrU-labeled HCV RNA, we found that the newly-synthesized HCV RNA traveled along the anterograde-membrane traffic and moved away from the ER. Presumably, the RNA moved to the site of translation or virion assembly in the later steps of viral life cycle. In this study, we further addressed how HCV RNA translation was regulated by HCV RNA trafficking. When the movement of HCV RNA from the site of RNA synthesis to the Golgi complex was blocked by nocodazole, an inhibitor of ER-Golgi transport, HCV protein translation was surprisingly enhanced, suggesting that the translation of viral proteins occurred near the site of RNA synthesis. We also found that the translation of HCV proteins was dependent on active RNA synthesis: inhibition of viral RNA synthesis by an NS5B inhibitor resulted in decreased HCV viral protein synthesis even when the total amount of intracellular HCV RNA remained unchanged. Furthermore, the translation activity of the replication-defective HCV replicons or viral RNA with an NS5B mutation was greatly reduced as compared to that of the corresponding wildtype RNA. By performing live cell labeling of newly synthesized HCV RNA and proteins, we further showed that the newly synthesized HCV proteins colocalized with the newly synthesized viral RNA, suggesting that HCV RNA replication and protein translation take place at or near the same site. Our findings together indicate that the translation of HCV RNA is coupled to RNA replication and that the both processes may occur at the same subcellular membrane compartments, which we term the replicasome.
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Affiliation(s)
- Helene Minyi Liu
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America.
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78
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Goyal S, Gupta G, Qin H, Upadya MH, Tan YJ, Chow VTK, Song J. VAPC, an human endogenous inhibitor for hepatitis C virus (HCV) infection, is intrinsically unstructured but forms a "fuzzy complex" with HCV NS5B. PLoS One 2012; 7:e40341. [PMID: 22815741 PMCID: PMC3398895 DOI: 10.1371/journal.pone.0040341] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 06/04/2012] [Indexed: 01/11/2023] Open
Abstract
Nearly 200 million people are infected by hepatitis C virus (HCV) worldwide. For replicating the HCV genome, the membrane-associated machinery needs to be formed by both HCV non-structural proteins (including NS5B) and human host factors such as VAPB. Recently, the 99-residue VAPC, a splicing variant of VAPB, was demonstrated to inhibit HCV replication via binding to NS5B, thus acting as an endogenous inhibitor of HCV infection. So far, the structure of VAPC remains unknown, and its interaction with NS5B has not been biophysically characterized. In this study, we conducted extensive CD and NMR investigations on VAPC which led to several striking findings: 1) although the N-terminal 70 residues are identical in VAPC and VAPB, they constitute the characteristic β-barrel MSP fold in VAPB, while VAPC is entirely unstructured in solution, only with helical-like conformations weakly populated. 2) VAPC is indeed capable of binding to NS5B, with an average dissociation constant (Kd) of ∼20 µM. Intriguingly, VAPC remains dynamic even in the complex, suggesting that the VAPC-NS5B is a “fuzzy complex”. 3) NMR mapping revealed that the major binding region for NS5B is located over the C-terminal half of VAPC, which is composed of three discrete clusters, of which only the first contains the region identical in VAPC and VAPB. The second region containing ∼12 residues appears to play a key role in binding since mutation of 4 residues within this region leads to almost complete loss of the binding activity. 4) A 14-residue mimetic, VAPC-14 containing the second region, only has a ∼3-fold reduction of the affinity. Our study not only provides critical insights into how a human factor mediates the formation of the HCV replication machinery, but also leads to design of VAPC-14 which may be further used to explore the function of VAPC and to develop anti-HCV molecules.
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Affiliation(s)
- Shaveta Goyal
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore
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Gupta G, Qin H, Song J. Intrinsically unstructured domain 3 of hepatitis C Virus NS5A forms a "fuzzy complex" with VAPB-MSP domain which carries ALS-causing mutations. PLoS One 2012; 7:e39261. [PMID: 22720086 PMCID: PMC3374797 DOI: 10.1371/journal.pone.0039261] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 05/22/2012] [Indexed: 01/26/2023] Open
Abstract
Hepatitis C virus (HCV) affects nearly 200 million people worldwide and is a leading factor for serious chronic liver diseases. For replicating HCV genome, the membrane-associated replication machinery needs to be formed by both HCV non-structural proteins including NS5A and human host factors. Recently NS5A has been identified to bind ER-anchored human VAP proteins and consequently this interaction may serve as a novel target for design of anti-HCV drugs. So far no biophysical characterization of this interaction has been reported. Here, we dissected the 243-residue VAPB into 4 and 447-residue NS5A into 10 fragments, followed by CD and NMR characterization of their structural properties. Subsequently, binding interactions between these fragments have been extensively assessed by NMR HSQC titration which is very powerful in detecting even very weak binding. The studies lead to three important findings: 1). a "fuzzy complex" is formed between the intrinsically-unstructured third domain (D3) of NS5A and the well-structured MSP domain of VAPB, with an average dissociation constant (Kd) of ~5 µM. 2). The binding-important residues on both NS5A-D3 and VAPB-MSP have been successfully mapped out, which provided experimental constraints for constructing the complex structure. In the complex, unstructured D3 binds to three surface pockets on one side of the MSP structure. Interestingly, two ALS-causing mutations T46I and P56S are also located on the D3-MSP interface. Moreover, NS5A-D3, FFAT-containing proteins and EphA4 appear to have overlapped binding interfaces on the MSP domain. 3). NS5A-D3 has been experimentally confirmed to competes with EphA4 in binding to the MSP domain, and T46I mutation of MSP dramatically abolishes its binding ability to D3. Our study not only provides essential foundation for further deciphering structure and function of the HCV replication machinery, but may also shed light on rationalizing a recent observation that a chronic HCV patient surprisingly developed ALS-like syndrome.
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Affiliation(s)
- Garvita Gupta
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Republic of Singapore
| | - Haina Qin
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Republic of Singapore
| | - Jianxing Song
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Republic of Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore
- * E-mail:
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80
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Treating hepatitis C infection by targeting the host. Transl Res 2012; 159:421-9. [PMID: 22633094 PMCID: PMC3361678 DOI: 10.1016/j.trsl.2011.12.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 12/15/2011] [Accepted: 12/20/2011] [Indexed: 12/11/2022]
Abstract
More than 130 million people worldwide are chronically infected with the hepatitis C virus (HCV), which can lead to cirrhosis, liver failure, and hepatocellular carcinoma. Although recently approved HCV NS3-4A protease inhibitors significantly improve treatment response rates, current HCV treatment is still frequently limited by side effects and by the low genetic barrier to viral resistance against direct-acting antiviral agents. A complementary strategy is to target the host cellular factors that support the HCV life cycle. Several studies, including RNA interference screens, demonstrated that HCV depends on dozens, if not hundreds, of cellular proteins to complete its life cycle. A better understanding of the interactions between HCV proteins and host factors may help to identify host targets for antiviral therapy. In this review, we highlight some of the host factors that are particularly attractive targets for the treatment of HCV.
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81
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Bianco A, Reghellin V, Donnici L, Fenu S, Alvarez R, Baruffa C, Peri F, Pagani M, Abrignani S, Neddermann P, De Francesco R. Metabolism of phosphatidylinositol 4-kinase IIIα-dependent PI4P Is subverted by HCV and is targeted by a 4-anilino quinazoline with antiviral activity. PLoS Pathog 2012; 8:e1002576. [PMID: 22412376 PMCID: PMC3297592 DOI: 10.1371/journal.ppat.1002576] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 01/26/2012] [Indexed: 12/13/2022] Open
Abstract
4-anilino quinazolines have been identified as inhibitors of HCV replication. The target of this class of compounds was proposed to be the viral protein NS5A, although unequivocal proof has never been presented. A 4-anilino quinazoline moiety is often found in kinase inhibitors, leading us to formulate the hypothesis that the anti-HCV activity displayed by these compounds might be due to inhibition of a cellular kinase. Type III phosphatidylinositol 4-kinase α (PI4KIIIα) has recently been identified as a host factor for HCV replication. We therefore evaluated AL-9, a compound prototypical of the 4-anilino quinazoline class, on selected phosphatidylinositol kinases. AL-9 inhibited purified PI4KIIIα and, to a lesser extent, PI4KIIIβ. In Huh7.5 cells, PI4KIIIα is responsible for the phosphatidylinositol-4 phosphate (PI4P) pool present in the plasma membrane. Accordingly, we observed a gradual decrease of PI4P in the plasma membrane upon incubation with AL-9, indicating that this agent inhibits PI4KIIIα also in living cells. Conversely, AL-9 did not affect the level of PI4P in the Golgi membrane, suggesting that the PI4KIIIβ isoform was not significantly inhibited under our experimental conditions. Incubation of cells expressing HCV proteins with AL-9 induced abnormally large clusters of NS5A, a phenomenon previously observed upon silencing PI4KIIIα by RNA interference. In light of our findings, we propose that the antiviral effect of 4-anilino quinazoline compounds is mediated by the inhibition of PI4KIIIα and the consequent depletion of PI4P required for the HCV membranous web. In addition, we noted that HCV has a profound effect on cellular PI4P distribution, causing significant enrichment of PI4P in the HCV-membranous web and a concomitant depletion of PI4P in the plasma membrane. This observation implies that HCV – by recruiting PI4KIIIα in the RNA replication complex – hijacks PI4P metabolism, ultimately resulting in a markedly altered subcellular distribution of the PI4KIIIα product. It is estimated that 3% of the world's population are chronically infected by the hepatitis C virus (HCV). Most infections become chronic and eventually evolve into cirrhosis and hepatocellular carcinoma. Host factors are interesting targets for anti-HCV therapies due to their inherent high genetic barrier to resistance. Recently, phosphatidylinositol 4-kinase α (PI4KIIIα) has been identified as a crucial host factor for HCV replication. Many different pathogens, including HCV, subvert components of the phosphatidylinositol-4 phosphate (PI4P) pathway to function in favor of their own life cycle. In this paper, we show that HCV dramatically alters cellular PI4P metabolism and distribution, resulting in the enrichment of PI4P in the membranous web required for viral replication with a concomitant decrease of PI4P in the plasma-membrane. Moreover, we demonstrate that 4-anilino quinazolines, antiviral agents previously believed to target HCV NS5A, do in fact inhibit PI4P formation by inhibition of PI4KIIIα. This compound class is a promising lead for the development of a novel antiviral therapy based on PI4KIIIα inhibition. Specific PI4KIIIα inhibitors would also be important research tools required for a deeper understanding of the functions and regulation of PI4P.
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Affiliation(s)
- Annalisa Bianco
- Department of Genomics and Molecular Biology, Virology Program, Istituto Nazionale Genetica Molecolare (INGM), Milano, Italy
| | - Veronica Reghellin
- Department of Genomics and Molecular Biology, Virology Program, Istituto Nazionale Genetica Molecolare (INGM), Milano, Italy
| | - Lorena Donnici
- Department of Genomics and Molecular Biology, Virology Program, Istituto Nazionale Genetica Molecolare (INGM), Milano, Italy
| | - Simone Fenu
- Department of Genomics and Molecular Biology, Virology Program, Istituto Nazionale Genetica Molecolare (INGM), Milano, Italy
| | - Reinaldo Alvarez
- Department of Genomics and Molecular Biology, Virology Program, Istituto Nazionale Genetica Molecolare (INGM), Milano, Italy
| | - Chiara Baruffa
- Department of Biotechnology and Biosciences, University of Milano Bicocca, Milano, Italy
| | - Francesco Peri
- Department of Biotechnology and Biosciences, University of Milano Bicocca, Milano, Italy
| | - Massimiliano Pagani
- Department of Genomics and Molecular Biology, Virology Program, Istituto Nazionale Genetica Molecolare (INGM), Milano, Italy
| | - Sergio Abrignani
- Department of Genomics and Molecular Biology, Virology Program, Istituto Nazionale Genetica Molecolare (INGM), Milano, Italy
| | - Petra Neddermann
- Department of Genomics and Molecular Biology, Virology Program, Istituto Nazionale Genetica Molecolare (INGM), Milano, Italy
- * E-mail: (PN) (PN); (RDF) (RD)
| | - Raffaele De Francesco
- Department of Genomics and Molecular Biology, Virology Program, Istituto Nazionale Genetica Molecolare (INGM), Milano, Italy
- * E-mail: (PN) (PN); (RDF) (RD)
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82
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Gene expression profiling of HCV genotype 3a initial liver fibrosis and cirrhosis patients using microarray. J Transl Med 2012; 10:41. [PMID: 22397681 PMCID: PMC3348056 DOI: 10.1186/1479-5876-10-41] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Accepted: 03/07/2012] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Hepatitis C virus (HCV) causes liver fibrosis that may lead to liver cirrhosis or hepatocellular carcinoma (HCC), and may partially depend on infecting viral genotype. HCV genotype 3a is being more common in Asian population, especially Pakistan; the detail mechanism of infection still needs to be explored. In this study, we investigated and compared the gene expression profile between initial fibrosis stage and cirrhotic 3a genotype patients. METHODS Gene expression profiling of human liver tissues was performed containing more than 22000 known genes. Using Oparray protocol, preparation and hybridization of slides was carried out and followed by scanning with GeneTAC integrator 4.0 software. Normalization of the data was obtained using MIDAS software and Significant Microarray Analysis (SAM) was performed to obtain differentially expressed candidate genes. RESULTS Out of 22000 genes studied, 219 differentially regulated genes found with P ≤ 0.05 between both groups; 107 among those were up-regulated and 112 were down-regulated. These genes were classified into 31 categories according to their biological functions. The main categories included: apoptosis, immune response, cell signaling, kinase activity, lipid metabolism, protein metabolism, protein modulation, metabolism, vision, cell structure, cytoskeleton, nervous system, protein metabolism, protein modulation, signal transduction, transcriptional regulation and transport activity. CONCLUSION This is the first study on gene expression profiling in patients associated with genotype 3a using microarray analysis. These findings represent a broad portrait of genomic changes in early HCV associated fibrosis and cirrhosis. We hope that identified genes in this study will help in future to act as prognostic and diagnostic markers to differentiate fibrotic patients from cirrhotic ones.
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83
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Moriishi K, Matsuura Y. Exploitation of lipid components by viral and host proteins for hepatitis C virus infection. Front Microbiol 2012; 3:54. [PMID: 22347882 PMCID: PMC3278987 DOI: 10.3389/fmicb.2012.00054] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 01/31/2012] [Indexed: 12/13/2022] Open
Abstract
Hepatitis C virus (HCV), which is a major causative agent of blood-borne hepatitis, has chronically infected about 170 million individuals worldwide and leads to chronic infection, resulting in development of steatosis, cirrhosis, and eventually hepatocellular carcinoma. Hepatocellular carcinoma associated with HCV infection is not only caused by chronic inflammation, but also by the biological activity of HCV proteins. HCV core protein is known as a main component of the viral nucleocapsid. It cooperates with host factors and possesses biological activity causing lipid alteration, oxidative stress, and progression of cell growth, while other viral proteins also interact with host proteins including molecular chaperones, membrane-anchoring proteins, and enzymes associated with lipid metabolism to maintain the efficiency of viral replication and production. HCV core protein is localized on the surface of lipid droplets in infected cells. However, the role of lipid droplets in HCV infection has not yet been elucidated. Several groups recently reported that other viral proteins also support viral infection by regulation of lipid droplets and core localization in infected cells. Furthermore, lipid components are required for modification of host factors and the intracellular membrane to maintain or up-regulate viral replication. In this review, we summarize the current status of knowledge regarding the exploitation of lipid components by viral and host proteins in HCV infection.
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Affiliation(s)
- Kohji Moriishi
- Department of Microbiology, Faculty of Medicine, University of Yamanashi Chuo-shi, Yamanashi, Japan
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84
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Abstract
The reality of hepatitis C is inescapable for the estimated 130 million people worldwide chronically infected with the virus. Yet this pathogen has been notoriously difficult to move from the infected individual into experimental systems, and each advance--from the identification of the infectious agent to its culture and study--has been a significant challenge. As a result of unrelenting technical hurdles, preventative and therapeutic options have been slow to reach hepatitis C patients. More than 35 years since the recognition of the disease, there is no vaccine available, and the only approved treatment, a combination of pegylated interferon-alpha (IFN-α) and ribavirin, is frequently ineffective. Decades of research, however, have resulted in systematic progress and much is now known about this once elusive pathogen. Most importantly, key breakthroughs have stimulated drug discovery, and the first generation of specifically targeted antiviral inhibitors is poised to enter the market. This review provides a look back at progress in developing tractable model systems for this important agent of chronic hepatitis.
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Affiliation(s)
- Catherine L Murray
- The Center for the Study of Hepatitis C, The Rockefeller University, New York, New York 10065, USA.
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85
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Virus factories, double membrane vesicles and viroplasm generated in animal cells. Curr Opin Virol 2011; 1:381-7. [PMID: 22440839 PMCID: PMC7102809 DOI: 10.1016/j.coviro.2011.09.008] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 09/23/2011] [Accepted: 09/23/2011] [Indexed: 12/16/2022]
Abstract
Many viruses reorganise cellular membrane compartments and the cytoskeleton to generate subcellular microenvironments called virus factories or 'viroplasm'. These create a platform to concentrate replicase proteins, virus genomes and host proteins required for replication and also protect against antiviral defences. There is growing interest in understanding how viruses induce such large changes in cellular organisation, and recent studies are beginning to reveal the relationship between virus factories and viroplasm and the cellular structures that house them. In this review, we discuss how three supergroups of (+)RNA viruses generate replication sites from membrane-bound organelles and highlight research on perinuclear factories induced by the nucleocytoplasmic large DNA viruses.
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86
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Cordek DG, Bechtel JT, Maynard AT, Kazmierski WM, Cameron CE. TARGETING THE NS5A PROTEIN OF HCV: AN EMERGING OPTION. DRUG FUTURE 2011; 36:691-711. [PMID: 23378700 PMCID: PMC3558953 DOI: 10.1358/dof.2011.036.09.1641618] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Hepatitis C virus (HCV) infects more than 3% of the world's population, leading to an increased risk of cirrhosis and hepatocellular carcinoma. The current standard of care, a combination of pegylated interferon alfa and ribavirin, is poorly tolerated and often ineffective against the most prevalent genotype of the virus, genotype 1. The very recent approval of boceprevir and telaprevir, two HCV protease inhibitors, promises to significantly improve treatment options and outcomes. In addition to the viral protease NS3 and the viral polymerase NS5B, direct-acting antivirals are now in development against NS5A. A multifunctional phosphoprotein, NS5A is essential to HCV genome replication, but has no known enzymatic function. Here we report how the design of small-molecule inhibitors against NS5A has evolved from promising monomers to highly potent dimeric compounds effective against many HCV genotypes. We also highlight recent clinical data and how the inhibitors may bind to NS5A, itself capable of forming dimers.
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Affiliation(s)
- D G Cordek
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
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87
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Heterogeneous nuclear ribonucleoprotein A2 participates in the replication of Japanese encephalitis virus through an interaction with viral proteins and RNA. J Virol 2011; 85:10976-88. [PMID: 21865391 DOI: 10.1128/jvi.00846-11] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that is kept in a zoonotic transmission cycle between pigs and mosquitoes. JEV causes infection of the central nervous system with a high mortality rate in dead-end hosts, including humans. Many studies have suggested that the flavivirus core protein is not only a component of nucleocapsids but also an important pathogenic determinant. In this study, we identified heterogeneous nuclear ribonucleoprotein A2 (hnRNP A2) as a binding partner of the JEV core protein by pulldown purification and mass spectrometry. Reciprocal coimmunoprecipitation analyses in transfected and infected cells confirmed a specific interaction between the JEV core protein and hnRNP A2. Expression of the JEV core protein induced cytoplasmic retention of hnRNP A2 in JEV subgenomic replicon cells. Small interfering RNA (siRNA)-mediated knockdown of hnRNP A2 resulted in a 90% reduction of viral RNA replication in cells infected with JEV, and the reduction was cancelled by the expression of an siRNA-resistant hnRNP A2 mutant. In addition to the core protein, hnRNP A2 also associated with JEV nonstructural protein 5, which has both methyltransferase and RNA-dependent RNA polymerase activities, and with the 5'-untranslated region of the negative-sense JEV RNA. During one-step growth, synthesis of both positive- and negative-strand JEV RNAs was delayed by the knockdown of hnRNP A2. These results suggest that hnRNP A2 plays an important role in the replication of JEV RNA through the interaction with viral proteins and RNA.
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88
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Barroso-González J, García-Expósito L, Puigdomènech I, de Armas-Rillo L, Machado JD, Blanco J, Valenzuela-Fernández A. Viral infection: Moving through complex and dynamic cell-membrane structures. Commun Integr Biol 2011; 4:398-408. [PMID: 21966556 DOI: 10.4161/cib.4.4.16716] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 05/31/2011] [Indexed: 01/19/2023] Open
Abstract
Viruses have developed different survival strategies in host cells by crossing cell-membrane compartments, during different steps of their viral life cycle. In fact, the non-regenerative viral membrane of enveloped viruses needs to encounter the dynamic cell-host membrane, during early steps of the infection process, in which both membranes fuse, either at cell-surface or in an endocytic compartment, to promote viral entry and infection. Once inside the cell, many viruses accomplish their replication process through exploiting or modulating membrane traffic, and generating specialized compartments to assure viral replication, viral budding and spreading, which also serve to evade the immune responses against the pathogen. In this review, we have attempted to present some data that highlight the importance of membrane dynamics during viral entry and replicative processes, in order to understand how viruses use and move through different complex and dynamic cell-membrane structures and how they use them to persist.
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Affiliation(s)
- Jonathan Barroso-González
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - Laura García-Expósito
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - Isabel Puigdomènech
- Fundació irsiCaixa-HIVACAT; Institut de Recerca en Ciències de la Salut Germans Trias i Pujol (IGTP); Hospital Germans Trias i Pujol; Universitat Autònoma de Barcelona; Barcelona, Catalonia Spain
| | - Laura de Armas-Rillo
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - José-David Machado
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - Julià Blanco
- Fundació irsiCaixa-HIVACAT; Institut de Recerca en Ciències de la Salut Germans Trias i Pujol (IGTP); Hospital Germans Trias i Pujol; Universitat Autònoma de Barcelona; Barcelona, Catalonia Spain
| | - Agustín Valenzuela-Fernández
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
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89
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Poly(C)-binding protein 2 interacts with sequences required for viral replication in the hepatitis C virus (HCV) 5' untranslated region and directs HCV RNA replication through circularizing the viral genome. J Virol 2011; 85:7954-64. [PMID: 21632751 DOI: 10.1128/jvi.00339-11] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Sequences in the 5' untranslated region (5'UTR) of hepatitis C virus (HCV) RNA is important for modulating both translation and RNA replication. The translation of the HCV genome depends on an internal ribosome entry site (IRES) located within the 341-nucleotide 5'UTR, while RNA replication requires a smaller region. A question arises whether the replication and translation functions require different regions of the 5'UTR and different sets of RNA-binding proteins. Here, we showed that the 5'-most 157 nucleotides of HCV RNA is the minimum 5'UTR for RNA replication, and it partially overlaps with the IRES. Stem-loops 1 and 2 of the 5'UTR are essential for RNA replication, whereas stem-loop 1 is not required for translation. We also found that poly(C)-binding protein 2 (PCBP2) bound to the replication region of the 5'UTR and associated with detergent-resistant membrane fractions, which are the sites of the HCV replication complex. The knockdown of PCBP2 by short hairpin RNA decreased the amounts of HCV RNA and nonstructural proteins. Antibody-mediated blocking of PCBP2 reduced HCV RNA replication in vitro, indicating that PCBP2 is directly involved in HCV RNA replication. Furthermore, PCBP2 knockdown reduced IRES-dependent translation preferentially from a dual reporter plasmid, suggesting that PCBP2 also regulated IRES activity. These findings indicate that PCBP2 participates in both HCV RNA replication and translation. Moreover, PCBP2 interacts with HCV 5'- and 3'UTR RNA fragments to form an RNA-protein complex and induces the circularization of HCV RNA, as revealed by electron microscopy. This study thus demonstrates the mechanism of the participation of PCBP2 in HCV translation and replication and provides physical evidence for HCV RNA circularization through 5'- and 3'UTR interaction.
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90
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Hepatitis C virus co-opts Ras-GTPase-activating protein-binding protein 1 for its genome replication. J Virol 2011; 85:6996-7004. [PMID: 21561913 DOI: 10.1128/jvi.00013-11] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
We recently reported that Ras-GTPase-activating protein-binding protein 1 (G3BP1) interacts with hepatitis C virus (HCV) nonstructural protein (NS)5B and the 5' end of the HCV minus-strand RNA. In the current study we confirmed these observations using immunoprecipitation and RNA pulldown assays, suggesting that G3BP1 might be an HCV replication complex (RC) component. In replicon cells, transfected G3BP1 interacts with multiple HCV nonstructural proteins. Using immunostaining and confocal microscopy, we demonstrate that G3BP1 is colocalized with HCV RCs in replicon cells. Small interfering RNA (siRNA)-mediated knockdown of G3BP1 moderately reduces established HCV RNA replication in HCV replicon cells and dramatically reduces HCV replication-dependent colony formation and cell-culture-produced HCV (HCVcc) infection. In contrast, knockdown of G3BP2 has no effect on HCVcc infection. Transient replication experiments show that G3BP1 is involved in HCV genome amplification. Thus, G3BP1 is associated with HCV RCs and may be co-opted as a functional RC component for viral replication. These findings may facilitate understanding of the molecular mechanisms of HCV genome replication.
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91
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Augustin R, Lichtenthaler SF, Greeff M, Hansen J, Wurst W, Trümbach D. Bioinformatics identification of modules of transcription factor binding sites in Alzheimer's disease-related genes by in silico promoter analysis and microarrays. Int J Alzheimers Dis 2011; 2011:154325. [PMID: 21559189 PMCID: PMC3090009 DOI: 10.4061/2011/154325] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Accepted: 02/15/2011] [Indexed: 11/21/2022] Open
Abstract
The molecular mechanisms and genetic risk factors underlying Alzheimer's disease (AD) pathogenesis are only partly understood. To identify new factors, which may contribute to AD, different approaches are taken including proteomics, genetics, and functional genomics. Here, we used a bioinformatics approach and found that distinct AD-related genes share modules of transcription factor binding sites, suggesting a transcriptional coregulation. To detect additional coregulated genes, which may potentially contribute to AD, we established a new bioinformatics workflow with known multivariate methods like support vector machines, biclustering, and predicted transcription factor binding site modules by using in silico analysis and over 400 expression arrays from human and mouse. Two significant modules are composed of three transcription factor families: CTCF, SP1F, and EGRF/ZBPF, which are conserved between human and mouse APP promoter sequences. The specific combination of in silico promoter and multivariate analysis can identify regulation mechanisms of genes involved in multifactorial diseases.
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Affiliation(s)
- Regina Augustin
- Institute of Developmental Genetics, Helmholtz Centre Munich, German Research Centre for Environmental Health (GmbH), Technical University Munich, Ingolstädter Landstraße 1, Munich 85764, Neuherberg, Germany
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92
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Small molecules targeting hepatitis C virus-encoded NS5A cause subcellular redistribution of their target: insights into compound modes of action. J Virol 2011; 85:6353-68. [PMID: 21507963 DOI: 10.1128/jvi.00215-11] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The current standard of care for hepatitis C virus (HCV)-infected patients consists of lengthy treatment with interferon and ribavirin. To increase the effectiveness of HCV therapy, future regimens will incorporate multiple direct-acting antiviral (DAA) drugs. Recently, the HCV-encoded NS5A protein has emerged as a promising DAA target. Compounds targeting NS5A exhibit remarkable potency in vitro and demonstrate early clinical promise, suggesting that NS5A inhibitors could feature in future DAA combination therapies. Since the mechanisms through which these molecules operate are unknown, we have used NS5A inhibitors as tools to investigate their modes of action. Analysis of replicon-containing cells revealed dramatic phenotypic alterations in NS5A localization following treatment with NS5A inhibitors; NS5A was redistributed from the endoplasmic reticulum to lipid droplets. The NS5A relocalization did not occur in cells treated with other classes of HCV inhibitors, and NS5A-targeting molecules did not cause similar alterations in the localization of other HCV-encoded proteins. Time course analysis of the redistribution of NS5A revealed that the transfer of protein to lipid droplets was concomitant with the onset of inhibition, as judged by the kinetic profiles for these compounds. Furthermore, analysis of the kinetic profile of inhibition for a panel of test molecules permitted the separation of compounds into different kinetic classes based on their modes of action. Results from this approach suggested that NS5A inhibitors perturbed the function of new replication complexes, rather than acting on preformed complexes. Taken together, our data reveal novel biological consequences of NS5A inhibition, which may help enable the development of future assay platforms for the identification of new and/or different NS5A inhibitors.
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93
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Morita K, Taketomi A, Shirabe K, Umeda K, Kayashima H, Ninomiya M, Uchiyama H, Soejima Y, Maehara Y. Clinical significance and potential of hepatic microRNA-122 expression in hepatitis C. Liver Int 2011; 31:474-84. [PMID: 21199296 DOI: 10.1111/j.1478-3231.2010.02433.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND AND AIMS MicroRNAs are small non-coding RNA molecules that post-transcriptionally regulate gene expression. Liver-specific microRNA-122 (miR-122) has been shown to facilitate the replication of hepatitis C virus (HCV) in human hepatoma cells in vitro. However, the clinical significance of hepatic miR-122 on HCV in human body is unclear. METHODS Hepatic miR-122 expression was quantified using quantitative reverse-transcription polymerase chain reaction. We investigated the correlation between miR-122 expression and HCV load in liver samples from 185 patients seropositive for HCV antibody, including 151 patients seropositive for HCV RNA, and 31 patients seronegative for HCV RNA. RESULTS Although hepatic miR-122 expression was weakly and positively correlated with the serum HCV load (ρ=0.19, P<0.05), it was not correlated with the hepatic HCV load (ρ=-0.14, P=0.08). The absence of a correlation between miR-122 expression and hepatic HCV load was also confirmed after stratification of histopathological liver damage (inflammatory activity grades and fibrosis stages). Furthermore, hepatic miR-122 expression in patients seronegative for HCV RNA was significantly higher than that in patients seropositive for HCV RNA (P<0.0001). The level of hepatic miR-122 expression was inversely correlated with the severity of functional and histopathological liver damage (P<0.0001), serum transaminase levels (P<0.0005). CONCLUSIONS Compared with in vitro findings, hepatic miR-122 expression is not correlated with HCV load in the human liver. Therefore, miR-122, by itself, is not a critical molecular target for HCV therapy. MiR-122 expression is inversely correlated with both functional and histopathological liver damage.
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Affiliation(s)
- Kazutoyo Morita
- Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
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94
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Inoue Y, Aizaki H, Hara H, Matsuda M, Ando T, Shimoji T, Murakami K, Masaki T, Shoji I, Homma S, Matsuura Y, Miyamura T, Wakita T, Suzuki T. Chaperonin TRiC/CCT participates in replication of hepatitis C virus genome via interaction with the viral NS5B protein. Virology 2010; 410:38-47. [PMID: 21093005 DOI: 10.1016/j.virol.2010.10.026] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2010] [Revised: 07/18/2010] [Accepted: 10/15/2010] [Indexed: 12/12/2022]
Abstract
To identify the host factors implicated in the regulation of hepatitis C virus (HCV) genome replication, we performed comparative proteome analyses of HCV replication complex (RC)-rich membrane fractions prepared from cells harboring genome-length bicistronic HCV RNA at the exponential and stationary growth phases. We found that the eukaryotic chaperonin T-complex polypeptide 1 (TCP1)-ring complex/chaperonin-containing TCP1 (TRiC/CCT) plays a role in the replication possibly through an interaction between subunit CCT5 and the viral RNA polymerase NS5B. siRNA-mediated knockdown of CCT5 suppressed RNA replication and production of the infectious virus. Gain-of-function activity was shown following co-transfection with whole eight TRiC/CCT subunits. HCV RNA synthesis was inhibited by an anti-CCT5 antibody in a cell-free assay. These suggest that recruitment of the chaperonin by the viral nonstructural proteins to the RC, which potentially facilitate folding of the RC component(s) into the mature active form, may be important for efficient replication of the HCV genome.
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Affiliation(s)
- Yasushi Inoue
- Department of Virology II, National Institute of Infectious Diseases, Tokyo 162-8640, Japan
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95
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Abstract
Hepatitis C virus (HCV) establishes a persistent infection and is recognized as a major cause of chronic liver diseases worldwide. Although much work remains to be done regarding the viral life cycle, significant progress has been made with respect to the molecular biology of HCV, especially the viral genome replication and virion formation. A variety of host cell factors, which play roles in replication of the viral genome RNA, have been identified. Involvement of lipid droplet, lipid metabolism and the viral nonstructural proteins in the production of the infectious particles has also been revealed.
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96
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Pezacki JP, Singaravelu R, Lyn RK. Host-virus interactions during hepatitis C virus infection: a complex and dynamic molecular biosystem. MOLECULAR BIOSYSTEMS 2010; 6:1131-42. [PMID: 20549003 DOI: 10.1039/b924668c] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The hepatitis C virus (HCV) is a global health issue with no vaccine available and limited clinical treatment options. Like other obligate parasites, HCV requires host cellular components of an infected individual to propagate. These host-virus interactions during HCV infection are complex and dynamic and involve the hijacking of host cell environments, enzymes and pathways. Understanding this unique molecular biosystem has the potential to yield new and exciting strategies for therapeutic intervention. Advances in genomics and proteomics have opened up new possibilities for the rapid measurement of global changes at the transcriptional and translational levels during infection. However, these techniques only yield snapshots of host-virus interactions during HCV infection. Other new methods that involve the imaging of biomolecular interactions during HCV infection are required to identify key interactions that may be transient and dynamic. Herein we highlight systems biology based strategies that have helped to identify key host-virus interactions during HCV replication and infection. Novel biophysical tools are also highlighted for identification and visualization of activities and interactions between HCV and its host hepatocyte. As some of these methods mature, we expect them to pave the way forward for further exploration of this complex biosystem and elucidation of mechanisms for HCV pathogenesis and carcinogenesis.
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Affiliation(s)
- John Paul Pezacki
- Steacie Institute for Molecular Sciences, National Research Council of Canada, 100 Sussex Dr., Ottawa, Ontario, Canada.
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97
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Tanaka Y, Mori Y, Tani H, Abe T, Moriishi K, Kojima H, Nagano T, Okabe T, Suzuki T, Tatsumi M, Matsuura Y. Establishment of an indicator cell system for hepatitis C virus. Microbiol Immunol 2010; 54:206-20. [PMID: 20377749 DOI: 10.1111/j.1348-0421.2010.00209.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Although a cell culture system for HCV JFH-1 strain has been developed, no robust cell culture system for serum-derived HCV is available. In this study, we have established systems capable of monitoring infection with JFH-1 virus based on specific reporter gene expression through proteolysis of chimeric transcription factors by HCV NS3/4A protease. We utilized a transcriptional factor Gal4-TBP that synergistically enhances transcription of the GAL4UAS and HIV-1 LTR tandem promoter with the Tat protein. We constructed chimeric Tat and Gal4-TBP transcription factors containing the HCV NS3/4A cleavage sequence of a mitochondria-resident IPS-1, but not those of the HCV polyprotein, and manipulated them to localize in the ER. Upon infection with JFH-1 virus, the transcription factors were efficiently cleaved by HCV protease, migrated into the nucleus and activated the reporter gene under the tandem promoter. Upon infection with JFH-1 virus, the Huh7OK1/TG-Luc cell line carrying the transcription factors and a luciferase gene under the promoter expressed luciferase in a dose-dependent manner in close correlation with HCV RNA replication. Huh7OK1/TG-LNGFR cells carrying the transcription factors and a cDNA of human low affinity nerve growth factor receptor under the promoter were selectively concentrated by immunomagnetic cell sorting upon infection with JFH-1 virus. These results indicate that the chimeric constructs bearing the ER-resident IPS-1 sequence are specifically recognized and efficiently cleaved by HCV protease and are harnessed for detection of HCV replication and for recovery of HCV-infected cells. This strategy may be applicable for the establishment of cell culture systems for the isolation of serum-derived HCV.
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Affiliation(s)
- Yoshinori Tanaka
- Department of Molecular Virology, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
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98
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Bellón-Echeverría I, López-Jiménez AJ, Clemente-Casares P, Mas A. Monitoring hepatitis C virus (HCV) RNA-dependent RNA polymerase oligomerization by a FRET-based in vitro system. Antiviral Res 2010; 87:57-66. [DOI: 10.1016/j.antiviral.2010.04.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Revised: 04/15/2010] [Accepted: 04/19/2010] [Indexed: 12/23/2022]
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99
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Jangra RK, Yi M, Lemon SM. DDX6 (Rck/p54) is required for efficient hepatitis C virus replication but not for internal ribosome entry site-directed translation. J Virol 2010; 84:6810-24. [PMID: 20392846 PMCID: PMC2903299 DOI: 10.1128/jvi.00397-10] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Accepted: 04/01/2010] [Indexed: 12/22/2022] Open
Abstract
DDX6 (Rck/p54) is an evolutionarily conserved member of the SF2 DEAD-box RNA helicase family that contributes to the regulation of translation and storage and the degradation of cellular mRNAs. It interacts with multiple proteins and is a component of the micro-RNA (miRNA)-induced silencing complex (miRISC). Since miRNA-122 (miR-122) is essential for efficient hepatitis C virus (HCV) replication, we investigated the requirement for DDX6 in HCV replication in cultured hepatoma cells. Small interfering RNA (siRNA)-mediated knockdown of DDX6 and rescue with an siRNA-resistant mutant demonstrated that DDX6 expression is indeed required for optimal HCV replication. However, DDX6 knockdown did not impair miR-122 biogenesis or alter HCV responsiveness to miR-122 supplementation. Overexpression of DDX6 fused to EYFP (EYFP-DDX6) enhanced replication, whereas a helicase-deficient mutant with a substitution in the conserved DEAD-box motif II (DQAD) had a dominant-negative effect, reducing HCV yields. Coimmunoprecipitation experiments revealed an intracellular complex containing DDX6, HCV core protein, and both viral and cellular RNAs, the formation of which was dependent upon the C-terminal domain of DDX6 but not DDX6 helicase activity. However, since DDX6 abundance influenced the replication of subgenomic HCV RNAs lacking core sequence, the relevance of this complex is uncertain. Importantly, DDX6 knockdown caused minimal reductions in cellular proliferation, generally stimulated cellular translation ([(35)S]Met incorporation), and did not impair translation directed by the HCV internal ribosome entry site. Thus, DDX6 helicase activity is essential for efficient HCV replication, reflecting essential roles for DDX6 in HCV genome amplification and/or maintenance of cellular homeostasis.
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Affiliation(s)
- Rohit K Jangra
- Center for Hepatitis Research, Institute for Human Infections and Immunity, and Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas 77555-0610, USA
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100
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Functional implications of sterol transport by the oxysterol-binding protein gene family. Biochem J 2010; 429:13-24. [PMID: 20545625 DOI: 10.1042/bj20100263] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Cholesterol and its numerous oxygenated derivatives (oxysterols) profoundly affect the biophysical properties of membranes, and positively and negatively regulate sterol homoeostasis through interaction with effector proteins. As the bulk of cellular sterols are segregated from the sensory machinery that controls homoeostatic responses, an important regulatory step involves sterol transport or signalling between membrane compartments. Evidence for rapid, energy-independent transport between organelles has implicated transport proteins, such as the eukaryotic family of OSBP (oxysterol-binding protein)/ORPs (OSBP-related proteins). Since the founding member of this family was identified more than 25 years ago, accumulated evidence has implicated OSBP/ORPs in sterol signalling and/or sterol transport functions. However, recent evidence of sterol transfer activity by OSBP/ORPs suggests that other seemingly disparate functions could be the result of alterations in membrane sterol distribution or ancillary to this primary activity.
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