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Coccia EM, Battistini A. Early IFN type I response: Learning from microbial evasion strategies. Semin Immunol 2015; 27:85-101. [PMID: 25869307 PMCID: PMC7129383 DOI: 10.1016/j.smim.2015.03.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 03/10/2015] [Indexed: 12/12/2022]
Abstract
Type I interferon (IFN) comprises a class of cytokines first discovered more than 50 years ago and initially characterized for their ability to interfere with viral replication and restrict locally viral propagation. As such, their induction downstream of germ-line encoded pattern recognition receptors (PRRs) upon recognition of pathogen-associated molecular patterns (PAMPs) is a hallmark of the host antiviral response. The acknowledgment that several PAMPs, not just of viral origin, may induce IFN, pinpoints at these molecules as a first line of host defense against a number of invading pathogens. Acting in both autocrine and paracrine manner, IFN interferes with viral replication by inducing hundreds of different IFN-stimulated genes with both direct anti-pathogenic as well as immunomodulatory activities, therefore functioning as a bridge between innate and adaptive immunity. On the other hand an inverse interference to escape the IFN system is largely exploited by pathogens through a number of tactics and tricks aimed at evading, inhibiting or manipulating the IFN pathway, that result in progression of infection or establishment of chronic disease. In this review we discuss the interplay between the IFN system and some selected clinically important and challenging viruses and bacteria, highlighting the wide array of pathogen-triggered molecular mechanisms involved in evasion strategies.
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Affiliation(s)
- Eliana M Coccia
- Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena, 299, Rome 00161, Italy
| | - Angela Battistini
- Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena, 299, Rome 00161, Italy.
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52
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Horner SM. Insights into antiviral innate immunity revealed by studying hepatitis C virus. Cytokine 2015; 74:190-7. [PMID: 25819428 DOI: 10.1016/j.cyto.2015.03.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 03/04/2015] [Indexed: 02/07/2023]
Abstract
Experimental studies on the interactions of the positive strand RNA virus hepatitis C virus (HCV) with the host have contributed to several discoveries in the field of antiviral innate immunity. These include revealing the antiviral sensing pathways that lead to the induction of type I interferon (IFN) during HCV infection and also the importance of type III IFNs in the antiviral immune response to HCV. These studies on HCV/host interactions have contributed to our overall understanding of viral sensing and viral evasion of the antiviral intracellular innate immune response. In this review, I will highlight how these studies of HCV/host interactions have led to new insights into antiviral innate immunity. Overall, I hope to emphasize that studying antiviral immunity in the context of virus infection is necessary to fully understand antiviral immunity and how it controls the outcome of viral infection.
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Affiliation(s)
- Stacy M Horner
- Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, NC 27710, United States; Department of Medicine, Duke University Medical Center, Durham, NC 27710, United States.
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Horner SM, Wilkins C, Badil S, Iskarpatyoti J, Gale M. Proteomic analysis of mitochondrial-associated ER membranes (MAM) during RNA virus infection reveals dynamic changes in protein and organelle trafficking. PLoS One 2015; 10:e0117963. [PMID: 25734423 PMCID: PMC4348417 DOI: 10.1371/journal.pone.0117963] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 01/06/2015] [Indexed: 02/07/2023] Open
Abstract
RIG-I pathway signaling of innate immunity against RNA virus infection is organized between the ER and mitochondria on a subdomain of the ER called the mitochondrial-associated ER membrane (MAM). The RIG-I adaptor protein MAVS transmits downstream signaling of antiviral immunity, with signaling complexes assembling on the MAM in association with mitochondria and peroxisomes. To identify components that regulate MAVS signalosome assembly on the MAM, we characterized the proteome of MAM, ER, and cytosol from cells infected with either chronic (hepatitis C) or acute (Sendai) RNA virus infections, as well as mock-infected cells. Comparative analysis of protein trafficking dynamics during both chronic and acute viral infection reveals differential protein profiles in the MAM during RIG-I pathway activation. We identified proteins and biochemical pathways recruited into and out of the MAM in both chronic and acute RNA viral infections, representing proteins that drive immunity and/or regulate viral replication. In addition, by using this comparative proteomics approach, we identified 3 new MAVS-interacting proteins, RAB1B, VTN, and LONP1, and defined LONP1 as a positive regulator of the RIG-I pathway. Our proteomic analysis also reveals a dynamic cross-talk between subcellular compartments during both acute and chronic RNA virus infection, and demonstrates the importance of the MAM as a central platform that coordinates innate immune signaling to initiate immunity against RNA virus infection.
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Affiliation(s)
- Stacy M. Horner
- Department of Immunology, University of Washington, Seattle, Washington, United States of America
- Department of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Courtney Wilkins
- Department of Immunology, University of Washington, Seattle, Washington, United States of America
| | - Samantha Badil
- Department of Immunology, University of Washington, Seattle, Washington, United States of America
| | - Jason Iskarpatyoti
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Michael Gale
- Department of Immunology, University of Washington, Seattle, Washington, United States of America
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Mukherjee S, Weiner WS, Schroeder CE, Simpson DS, Hanson AM, Sweeney NL, Marvin RK, Ndjomou J, Kolli R, Isailovic D, Schoenen FJ, Frick DN. Ebselen inhibits hepatitis C virus NS3 helicase binding to nucleic acid and prevents viral replication. ACS Chem Biol 2014; 9:2393-403. [PMID: 25126694 PMCID: PMC4201343 DOI: 10.1021/cb500512z] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The hepatitis C virus (HCV) nonstructural protein 3 (NS3) is both a protease, which cleaves viral and host proteins, and a helicase that separates nucleic acid strands, using ATP hydrolysis to fuel the reaction. Many antiviral drugs, and compounds in clinical trials, target the NS3 protease, but few helicase inhibitors that function as antivirals have been reported. This study focuses on the analysis of the mechanism by which ebselen (2-phenyl-1,2-benzisoselenazol-3-one), a compound previously shown to be a HCV antiviral agent, inhibits the NS3 helicase. Ebselen inhibited the abilities of NS3 to unwind nucleic acids, to bind nucleic acids, and to hydrolyze ATP, and about 1 μM ebselen was sufficient to inhibit each of these activities by 50%. However, ebselen had no effect on the activity of the NS3 protease, even at 100 times higher ebselen concentrations. At concentrations below 10 μM, the ability of ebselen to inhibit HCV helicase was reversible, but prolonged incubation of HCV helicase with higher ebselen concentrations led to irreversible inhibition and the formation of covalent adducts between ebselen and all 14 cysteines present in HCV helicase. Ebselen analogues with sulfur replacing the selenium were just as potent HCV helicase inhibitors as ebselen, but the length of the linker between the phenyl and benzisoselenazol rings was critical. Modifications of the phenyl ring also affected compound potency over 30-fold, and ebselen was a far more potent helicase inhibitor than other, structurally unrelated, thiol-modifying agents. Ebselen analogues were also more effective antiviral agents, and they were less toxic to hepatocytes than ebselen. Although the above structure-activity relationship studies suggest that ebselen targets a specific site on NS3, we were unable to confirm binding to either the NS3 ATP binding site or nucleic acid binding cleft by examining the effects of ebselen on NS3 proteins lacking key cysteines.
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Affiliation(s)
- Sourav Mukherjee
- Department of Chemistry & Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - Warren S. Weiner
- University
of Kansas Specialized Chemistry Center, University of Kansas, 2034 Becker Drive, Lawrence, Kansas 66047, United States
| | - Chad E. Schroeder
- University
of Kansas Specialized Chemistry Center, University of Kansas, 2034 Becker Drive, Lawrence, Kansas 66047, United States
| | - Denise S. Simpson
- University
of Kansas Specialized Chemistry Center, University of Kansas, 2034 Becker Drive, Lawrence, Kansas 66047, United States
| | - Alicia M. Hanson
- Department of Chemistry & Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - Noreena L. Sweeney
- Department of Chemistry & Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - Rachel K. Marvin
- Department
of Chemistry and Biochemistry, University of Toledo, Toledo, Ohio 43606, United States
| | - Jean Ndjomou
- Department of Chemistry & Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - Rajesh Kolli
- Department of Chemistry & Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53211, United States
| | - Dragan Isailovic
- Department
of Chemistry and Biochemistry, University of Toledo, Toledo, Ohio 43606, United States
| | - Frank J. Schoenen
- University
of Kansas Specialized Chemistry Center, University of Kansas, 2034 Becker Drive, Lawrence, Kansas 66047, United States
| | - David N. Frick
- Department of Chemistry & Biochemistry, University of Wisconsin−Milwaukee, Milwaukee, Wisconsin 53211, United States
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55
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Kwon YC, Ray RB, Ray R. Hepatitis C virus infection: establishment of chronicity and liver disease progression. EXCLI JOURNAL 2014; 13:977-96. [PMID: 26417315 PMCID: PMC4464452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 08/14/2014] [Indexed: 11/16/2022]
Abstract
Hepatitis C virus (HCV) often causes persistent infection, and is an important factor in the etiology of fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). There are no preventive or therapeutic vaccines available against HCV. Treatment strategies of HCV infection are likely to improve with recently discovered direct antiviral agents (DAAs). However, a proportion of patients still progress to liver failure and/or HCC despite having been cured of the infection. Thus, there is a need for early diagnosis and therapeutic modalities for HCV related end stage liver disease prevention. HCV genome does not integrate into its host genome, and has a predominantly cytoplasmic life cycle. Therefore, HCV mediated liver disease progression appears to involve indirect mechanisms from persistent infection of hepatocytes. Studying the underlying mechanisms of HCV mediated evasion of immune responses and liver disease progression is challenging due to the lack of a naturally susceptible small animal model. We and other investigators have used a number of experimental systems to investigate the mechanisms for establishment of chronic HCV infection and liver disease progression. HCV infection modulates immune systems. Further, HCV infection of primary human hepatocytes promotes growth, induces phenotypic changes, modulates epithelial mesenchymal transition (EMT) related genes, and generates tumor initiating stem-like cells (TISCs). HCV infection also modulates microRNAs (miRNAs), and influences growth by overriding normal death progression of primary human hepatocytes for disease pathogenesis. Understanding these ob-servations at the molecular level should aid in developing strategies for additional effective therapies against HCV mediated liver disease progression.
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Affiliation(s)
- Young-Chan Kwon
- Department of Internal Medicine, Saint Louis University, Missouri
| | - Ratna B. Ray
- Department of Pathology, Saint Louis University, Missouri
| | - Ranjit Ray
- Department of Internal Medicine, Saint Louis University, Missouri,Department of Molecular Microbiology & Immunology, Saint Louis University, Missouri,*To whom correspondence should be addressed: Ranjit Ray, Division of Infectious Diseases, Allergy & Immunology, Edward A. Doisy Research Center, 1100 S. Grand Blvd, 8th Floor, St. Louis, MO 63104, USA, E-mail:
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56
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Nazmi A, Dutta K, Hazra B, Basu A. Role of pattern recognition receptors in flavivirus infections. Virus Res 2014; 185:32-40. [PMID: 24657789 DOI: 10.1016/j.virusres.2014.03.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 03/11/2014] [Accepted: 03/11/2014] [Indexed: 12/24/2022]
Abstract
The flaviviral encephalitis has now become a major health concern in global scale. The efficient detection of viral infection and induction of the innate antiviral response by host's innate immune system are crucial to determine the outcome of infection. The intracellular pattern recognition receptors TLRs, RLRs, NLRs and CLRs play a central role in detection and initiation of robust antiviral response against flaviviral infection. Both cytoplasmic RLRs, RIG-I and MDA5 have been shown to be implicated in sensing flaviviral genomic RNA. Similarly among TLRs mainly TLR3 and TLR7 are known to respond in flaviviral infections as they are known to sense dsRNA and ssRNA moiety as their natural cognate ligand. Several studies have also shown the roles of NLRs and CLRs in mounting an innate antiviral response against flavivirus but, it is yet to be completely understood. Until now only few reports have implicated NLRs and CLRs in induction of antiviral and proinflammatory state following flaviviral infection. The current review therefore aims to comprehensively analyze past as well as current understanding on the role of PRRs in flaviviral infections.
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Affiliation(s)
- Arshed Nazmi
- National Brain Research Centre, Manesar, Haryana 122051, India.
| | - Kallol Dutta
- National Brain Research Centre, Manesar, Haryana 122051, India
| | - Bibhabasu Hazra
- National Brain Research Centre, Manesar, Haryana 122051, India
| | - Anirban Basu
- National Brain Research Centre, Manesar, Haryana 122051, India.
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Hantavirus GnT elements mediate TRAF3 binding and inhibit RIG-I/TBK1-directed beta interferon transcription by blocking IRF3 phosphorylation. J Virol 2014; 88:2246-59. [PMID: 24390324 DOI: 10.1128/jvi.02647-13] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Hantaviruses successfully replicate in primary human endothelial cells by restricting the early induction of beta interferon (IFN-β) and interferon-stimulated genes (ISGs). Gn proteins from NY-1V, ANDV, and TULV, but not PHV, harbor elements in their 142-residue cytoplasmic tails (GnTs) that inhibit RIG-I/MAVS/TBK1-TRAF3-directed IFN-β induction. Here, we define GnT interactions and residues required to inhibit TRAF3-TBK1-directed IFN-β induction and IRF3 phosphorylation. We observed that GnTs bind TRAF3 via residues within the TRAF-N domain (residues 392 to 415) and that binding is independent of the MAVS-interactive TRAF-C domain (residues 415 to 568). We determined that GnT binding to TRAF3 is mediated by C-terminal degrons within NY-1V or ANDV GnTs and that mutations that add degrons to TULV or PHV GnTs confer TRAF3 binding. Further analysis of GnT domains revealed that TRAF3 binding is a discrete GnT function, independent of IFN regulation, and that residues 15 to 42 from the NY-1V GnT C terminus are required for inhibiting TBK1-directed IFN-β transcription. Mutagenesis of the NY-1V GnT revealed that altering tyrosine 627 (Y627A/S/F) abolished GnT regulation of RIG-I/TBK1-directed IRF3 phosphorylation and transcriptional responses of ISRE, κB, and IFN-β promoters. Moreover, GnTs from NY-1V, ANDV, and TULV, but not PHV, inhibited RIG-I-directed IRF3 phosphorylation. Collectively, these findings suggest a novel role for GnTs in regulating RIG-I/TBK1 pathway-directed IRF3 phosphorylation and IFN-β induction and define virulence determinants within GnTs that may permit the attenuation of pathogenic hantaviruses. IMPORTANCE These findings provide a mechanism for selected hantavirus GnT interactions to regulate RIG-I/TBK1 signaling responses required for IFN-β induction by inhibiting TBK1 phosphorylation of IRF3. These studies culminate in showing that a single GnT residue, Y627, is required for the NY-1V GnT to inhibit RIG-I/TBK1-directed IRF3 phosphorylation and IFN-β induction. These findings define a potential virulence determinant within the NY-1V GnT that may permit hantavirus attenuation.
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58
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Anti-viral tetris: modulation of the innate anti-viral immune response by A20. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 809:49-64. [PMID: 25302365 DOI: 10.1007/978-1-4939-0398-6_4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The A20 protein has emerged as an important negative regulator of Toll like receptor (TLR) and retinoic acid-inducible gene 1 (RIG-I)-mediated anti-viral signaling. A20 functions both as a RING-type E3 ubiquitin ligase and as a de-ubiquitinating enzyme. Nuclear factor kappa B (NF-kappaB) and interferon regulatory factor (IRF) pathways are targeted by A20 through mechanisms that appear to be both overlapping and distinct, resulting in the downregulation of interferon alpha/beta (IFNalpha/beta) production. This review specifically details the impact of A20 on the cytosolic RIG-I/MDA5 pathway, a process that is less understood than that of NF-kappaB but is essential for the regulation of the innate immune response to viral infection.
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59
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Rustagi A, Gale M. Innate antiviral immune signaling, viral evasion and modulation by HIV-1. J Mol Biol 2013; 426:1161-77. [PMID: 24326250 DOI: 10.1016/j.jmb.2013.12.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Revised: 11/26/2013] [Accepted: 12/02/2013] [Indexed: 02/08/2023]
Abstract
The intracellular innate antiviral response in human cells is an essential component of immunity against virus infection. As obligate intracellular parasites, all viruses must evade the actions of the host cell's innate immune response in order to replicate and persist. Innate immunity is induced when pathogen recognition receptors of the host cell sense viral products including nucleic acid as "non-self". This process induces downstream signaling through adaptor proteins to activate latent transcription factors that drive the expression of genes encoding antiviral and immune modulatory effector proteins that restrict virus replication and regulate adaptive immunity. The interferon regulatory factors (IRFs) are transcription factors that play major roles in innate immunity. In particular, IRF3 is activated in response to infection by a range of viruses including RNA viruses, DNA viruses and retroviruses. Among these viruses, human immunodeficiency virus type 1 (HIV-1) remains a major global health problem mediating chronic infection in millions of people wherein recent studies show that viral persistence is linked with the ability of the virus to dysregulate and evade the innate immune response. In this review, we discuss viral pathogen sensing, innate immune signaling pathways and effectors that respond to viral infection, the role of IRF3 in these processes and how it is regulated by pathogenic viruses. We present a contemporary overview of the interplay between HIV-1 and innate immunity, with a focus on understanding how innate immune control impacts infection outcome and disease.
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Affiliation(s)
- Arjun Rustagi
- Departments of Immunology and Global Health, University of Washington, Seattle, WA 98195-8059, USA
| | - Michael Gale
- Departments of Immunology and Global Health, University of Washington, Seattle, WA 98195-8059, USA.
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60
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Pękalski J, Zuk PJ, Kochańczyk M, Junkin M, Kellogg R, Tay S, Lipniacki T. Spontaneous NF-κB activation by autocrine TNFα signaling: a computational analysis. PLoS One 2013; 8:e78887. [PMID: 24324544 PMCID: PMC3855823 DOI: 10.1371/journal.pone.0078887] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 09/16/2013] [Indexed: 11/18/2022] Open
Abstract
NF-κB is a key transcription factor that regulates innate immune response. Its activity is tightly controlled by numerous feedback loops, including two negative loops mediated by NF-κB inducible inhibitors, IκBα and A20, which assure oscillatory responses, and by positive feedback loops arising due to the paracrine and autocrine regulation via TNFα, IL-1 and other cytokines. We study the NF-κB system of interlinked negative and positive feedback loops, combining bifurcation analysis of the deterministic approximation with stochastic numerical modeling. Positive feedback assures the existence of limit cycle oscillations in unstimulated wild-type cells and introduces bistability in A20-deficient cells. We demonstrated that cells of significant autocrine potential, i.e., cells characterized by high secretion of TNFα and its receptor TNFR1, may exhibit sustained cytoplasmic-nuclear NF-κB oscillations which start spontaneously due to stochastic fluctuations. In A20-deficient cells even a small TNFα expression rate qualitatively influences system kinetics, leading to long-lasting NF-κB activation in response to a short-pulsed TNFα stimulation. As a consequence, cells with impaired A20 expression or increased TNFα secretion rate are expected to have elevated NF-κB activity even in the absence of stimulation. This may lead to chronic inflammation and promote cancer due to the persistent activation of antiapoptotic genes induced by NF-κB. There is growing evidence that A20 mutations correlate with several types of lymphomas and elevated TNFα secretion is characteristic of many cancers. Interestingly, A20 loss or dysfunction also leaves the organism vulnerable to septic shock and massive apoptosis triggered by the uncontrolled TNFα secretion, which at high levels overcomes the antiapoptotic action of NF-κB. It is thus tempting to speculate that some cancers of deregulated NF-κB signaling may be prone to the pathogen-induced apoptosis.
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Affiliation(s)
- Jakub Pękalski
- Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - Pawel J. Zuk
- Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland
| | - Marek Kochańczyk
- Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland
| | - Michael Junkin
- Department of Biosystems Science and Engineering, ETH Zurich, Zurich, Switzerland
| | - Ryan Kellogg
- Department of Biosystems Science and Engineering, ETH Zurich, Zurich, Switzerland
| | - Savaş Tay
- Department of Biosystems Science and Engineering, ETH Zurich, Zurich, Switzerland
| | - Tomasz Lipniacki
- Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland
- Department of Statistics, Rice University, Houston, Texas, United States of America
- * E-mail:
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61
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Activation and evasion of antiviral innate immunity by hepatitis C virus. J Mol Biol 2013; 426:1198-209. [PMID: 24184198 DOI: 10.1016/j.jmb.2013.10.032] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 10/22/2013] [Accepted: 10/23/2013] [Indexed: 02/08/2023]
Abstract
Hepatitis C virus (HCV) chronically infects 130-170 million people worldwide and is a major public health burden. HCV is an RNA virus that infects hepatocytes within liver, and this infection is sensed as non-self by the intracellular innate immune response to program antiviral immunity to HCV. HCV encodes several strategies to evade this antiviral response, and this evasion of innate immunity plays a key role in determining viral persistence. This review discusses the molecular mechanisms of how the intracellular innate immune system detects HCV infection, including how HCV pathogen-associated molecular patterns are generated during infection and where they are recognized as foreign by the innate immune system. Further, this review highlights the key innate immune evasion strategies used by HCV to establish persistent infection within the liver, as well as how host genotype influences the outcome of HCV infection. Understanding these HCV-host interactions is key in understanding how to target HCV during infection and for the design of more effective HCV therapies at the immunological level.
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62
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Herpes simplex virus 1 serine/threonine kinase US3 hyperphosphorylates IRF3 and inhibits beta interferon production. J Virol 2013; 87:12814-27. [PMID: 24049179 DOI: 10.1128/jvi.02355-13] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Viral infection initiates a series of signaling cascades that lead to the transcription of interferons (IFNs), finally inducing interferon-stimulated genes (ISGs) to eliminate viruses. Viruses have evolved a variety of strategies to modulate host IFN-mediated immune responses. Herpes simplex virus 1 (HSV-1) US3, a Ser/Thr kinase conserved in alphaherpesviruses, was previously reported to counteract host innate immunity; however, the molecular mechanism is elusive. In this study, we report that US3 blocks IFN-β production by hyperphosphorylating IFN regulatory factor 3 (IRF3). Ectopic expression of US3 protein significantly inhibited Sendai virus (SeV)-mediated activation of IFN-β and IFN-stimulated response element (ISRE) promoters and the transcription of IFN-β, ISG54, and ISG56. US3 was also shown to block SeV-induced dimerization and nuclear translocation of IRF3. The kinase activity was indispensable for its inhibitory function, as kinase-dead (KD) US3 mutants K220M and D305A could not inhibit IFN-β production. Furthermore, US3 interacted with and hyperphosphorylated IRF3 at Ser175 to prevent IRF3 activation. Finally, the US3 KD mutant viruses were constructed and denoted K220M or D305A HSV-1, respectively. Cells and mice infected with both mutant viruses produced remarkably larger amounts of IFN-β than those infected with wild-type HSV-1. For the first time, these findings provide convincing evidence that US3 hyperphosphorylates IRF3, blocks the production of IFN-β, and subverts host innate immunity.
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63
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Herpes simplex virus 1 ubiquitin-specific protease UL36 inhibits beta interferon production by deubiquitinating TRAF3. J Virol 2013; 87:11851-60. [PMID: 23986588 DOI: 10.1128/jvi.01211-13] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Interferon (IFN)-mediated innate immune defense is a potent antiviral mechanism. Viruses evade innate immunity and limit secretion of beta interferon (IFN-β) to replicate and survive in the host. The largest tegument protein of herpes simplex virus 1 (HSV-1), UL36, contains a novel deubiquitinase (DUB) motif embedded in its N terminus, denoted UL36 ubiquitin-specific protease (UL36USP). In the present study, we demonstrate that HSV-1 UL36USP inhibits Sendai virus (SeV)-induced interferon regulatory factor 3 (IRF3) dimerization, promoter activation, and transcription of IFN-β. The DUB activity of UL36USP is essential to block IFN-β production. UL36USP also inhibited IFN-β promoter activity induced by overexpression of the N terminus of RIG-I (RIG-IN) and MAVS, but not TBK-1, IκB kinase ε (IKKε), and IRF3/5D. UL36USP was subsequently shown to deubiquitinate TRAF3 and prevent the recruitment of the downstream adaptor TBK1. The recombinant HSV-1 lacking UL36USP DUB activity was generated. Cells infected with the mutant virus produced more IFN-β than wild-type (WT) HSV-1-infected cells. These findings demonstrate HSV-1 UL36USP removes polyubiquitin chains on TRAF3 and counteracts the IFN-β pathway.
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64
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Luo H, Zhang Z, Zheng Z, Ke X, Zhang X, Li Q, Liu Y, Bai B, Mao P, Hu Q, Wang H. Human bocavirus VP2 upregulates IFN-β pathway by inhibiting ring finger protein 125-mediated ubiquitination of retinoic acid-inducible gene-I. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2013; 191:660-9. [PMID: 23772026 DOI: 10.4049/jimmunol.1202933] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Precise regulation of innate immunity is crucial for maintaining optimal immune responses against infections. Whereas positive regulation of IFN signaling elicits rapid type I IFNs, negative regulation is equally important in preventing the production of superfluous IFNs that can be hazardous to the host. The positive regulators of IFN pathway are known to be the main targets of viruses to antagonize the innate immune system. Whether viruses target the negative regulators of IFN pathway remains to be fully investigated. In this study, we report that the structural protein VP2 of human Bocavirus modulates IFN pathway by targeting the ring finger protein 125 (RNF125), a negative regulator of type I IFN signaling, which conjugates Lys(48)-linked ubiquitination to retinoic acid-inducible gene-I (RIG-I) and subsequently leads to the proteasome-dependent degradation of RIG-I. VP2 not only upregulated Sendai virus (SeV)-induced IFNB promoter activity, but also enhanced SeV-induced IFN-β production at both mRNA and protein levels. In agreement, the level of Ser(396)-phosphorylated IFN regulatory factor 3 stimulated by SeV was enhanced in the presence of VP2. Furthermore, VP2 was demonstrated to physically interact with RNF125, resulting in the reduction of RNF125-mediated ubiquitination and proteasome-dependent degradation of RIG-I. Additional study indicated that endogenous RIG-I degradation was decreased in VP2-expressing cells. Our study delineates a unique phenomenon for aberrant activation of IFN regulatory factor 3 pathway and may represent a new mechanism underlying viral manipulation of the host immune system.
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Affiliation(s)
- Huanle Luo
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
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Herpes simplex virus 1-encoded tegument protein VP16 abrogates the production of beta interferon (IFN) by inhibiting NF-κB activation and blocking IFN regulatory factor 3 to recruit its coactivator CBP. J Virol 2013; 87:9788-801. [PMID: 23824799 DOI: 10.1128/jvi.01440-13] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Host cells activate innate immune signaling pathways to defend against invading pathogens. To survive within an infected host, viruses have evolved intricate strategies to counteract host immune responses. Herpesviruses, including herpes simplex virus type 1 (HSV-1), have large genomes and therefore have the capacity to encode numerous proteins that modulate host innate immune responses. Here we define the contribution of HSV-1 tegument protein VP16 in the inhibition of beta interferon (IFN-β) production. VP16 was demonstrated to significantly inhibit Sendai virus (SeV)-induced IFN-β production, and its transcriptional activation domain was not responsible for this inhibition activity. Additionally, VP16 blocked the activation of the NF-κB promoter induced by SeV or tumor necrosis factor alpha treatment and expression of NF-κB-dependent genes through interaction with p65. Coexpression analysis revealed that VP16 selectively blocked IFN regulatory factor 3 (IRF-3)-mediated but not IRF-7-mediated transactivation. VP16 was able to bind to IRF-3 but not IRF-7 in vivo, based on coimmunoprecipitation analysis, but it did not affect IRF-3 dimerization, nuclear translocation, or DNA binding activity. Rather, VP16 interacted with the CREB binding protein (CBP) coactivator and efficiently inhibited the formation of the transcriptional complexes IRF-3-CBP in the context of HSV-1 infection. These results illustrate that VP16 is able to block the production of IFN-β by inhibiting NF-κB activation and interfering with IRF-3 to recruit its coactivator CBP, which may be important to the early events leading to HSV-1 infection.
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66
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Horner SM, Gale M. Regulation of hepatic innate immunity by hepatitis C virus. Nat Med 2013; 19:879-88. [PMID: 23836238 PMCID: PMC4251871 DOI: 10.1038/nm.3253] [Citation(s) in RCA: 216] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 05/30/2013] [Indexed: 02/08/2023]
Abstract
Hepatitis C virus (HCV) is a global public health problem involving chronic infection of the liver, which can cause liver disease and is linked with liver cancer. Viral innate immune evasion strategies and human genetic determinants underlie the transition of acute HCV infection to viral persistence and the support of chronic infection. Host genetic factors, such as sequence polymorphisms in IFNL3, a gene in the host interferon system, can influence both the outcome of the infection and the response to antiviral therapy. Recent insights into how HCV regulates innate immune signaling within the liver reveal a complex interaction of patient genetic background with viral and host factors of innate immune triggering and control that imparts the outcome of HCV infection and immunity.
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Affiliation(s)
- Stacy M Horner
- Department of Immunology, University of Washington, Seattle, Washington, USA
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67
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Wang B, Xi X, Lei X, Zhang X, Cui S, Wang J, Jin Q, Zhao Z. Enterovirus 71 protease 2Apro targets MAVS to inhibit anti-viral type I interferon responses. PLoS Pathog 2013; 9:e1003231. [PMID: 23555247 PMCID: PMC3605153 DOI: 10.1371/journal.ppat.1003231] [Citation(s) in RCA: 173] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Accepted: 01/23/2013] [Indexed: 01/26/2023] Open
Abstract
Enterovirus 71 (EV71) is the major causative pathogen of hand, foot, and mouth disease (HFMD). Its pathogenicity is not fully understood, but innate immune evasion is likely a key factor. Strategies to circumvent the initiation and effector phases of anti-viral innate immunity are well known; less well known is whether EV71 evades the signal transduction phase regulated by a sophisticated interplay of cellular and viral proteins. Here, we show that EV71 inhibits anti-viral type I interferon (IFN) responses by targeting the mitochondrial anti-viral signaling (MAVS) protein--a unique adaptor molecule activated upon retinoic acid induced gene-I (RIG-I) and melanoma differentiation associated gene (MDA-5) viral recognition receptor signaling--upstream of type I interferon production. MAVS was cleaved and released from mitochondria during EV71 infection. An in vitro cleavage assay demonstrated that the viral 2A protease (2A(pro)), but not the mutant 2A(pro) (2A(pro)-110) containing an inactivated catalytic site, cleaved MAVS. The Protease-Glo assay revealed that MAVS was cleaved at 3 residues between the proline-rich and transmembrane domains, and the resulting fragmentation effectively inactivated downstream signaling. In addition to MAVS cleavage, we found that EV71 infection also induced morphologic and functional changes to the mitochondria. The EV71 structural protein VP1 was detected on purified mitochondria, suggesting not only a novel role for mitochondria in the EV71 replication cycle but also an explanation of how EV71-derived 2A(pro) could approach MAVS. Taken together, our findings reveal a novel strategy employed by EV71 to escape host anti-viral innate immunity that complements the known EV71-mediated immune-evasion mechanisms.
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Affiliation(s)
- Bei Wang
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China
| | - Xueyan Xi
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China
| | - Xiaobo Lei
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China
| | - Xiaoyan Zhang
- Department of Medical Laboratory Science, Fenyang College Shanxi Medical University, Fenyang, Shanxi, People's Republic of China
| | - Sheng Cui
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China
| | - Jianwei Wang
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China
| | - Qi Jin
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China
| | - Zhendong Zhao
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, People's Republic of China
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68
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Bruni D, Sebastia J, Dunne S, Schröder M, Butler MP. A novel IRAK1-IKKε signaling axis limits the activation of TAK1-IKKβ downstream of TLR3. THE JOURNAL OF IMMUNOLOGY 2013; 190:2844-56. [PMID: 23396947 DOI: 10.4049/jimmunol.1202042] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
IRAK1 is involved in the regulation of type I IFN production downstream of TLR3. Previous work indicated that IRAK1 negatively regulates TRIF-mediated activation of IRF3 and IRF7. We report that IRAK1 limits the activation of the TLR3-NF-κB pathway. Following TLR3 stimulation, IRAK1-deficient macrophages produced increased levels of IL-6 and IFN-β compared with wild type macrophages. Pharmacological inhibition of TAK1 reduced this increase in IFN-β, together with the heightened activation of IRF3 and p65 found in TLR3-ligand stimulated IRAK1-deficient macrophages. Recently, IKKε and TANK-binding kinase 1 (TBK1) were reported to limit activation of the NF-κB pathway downstream of IL-1R, TNFR1, and TLRs. We show that TBK1 has a positive role in the TLR3-NF-κB pathway, because we detected reduced levels of IL-6 and reduced activation of p65 in TBK1-deficient macrophages. In contrast, we show that IKKε limits the activation of the TLR3-NF-κB pathway. Furthermore, we show that IRAK1 is required for the activation of IKKε downstream of TLR3. We report impaired activation of ERK1/2 in IRAK1- and IKKε-deficient macrophages, a novel finding for both kinases. Importantly, this work provides novel mechanistic insight into the regulation of the TLR3-signaling pathway, providing strong evidence that an IRAK1-IKKε-signaling axis acts to limit the production of both type I IFNs and proinflammatory cytokines by regulating TAK1 activity.
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Affiliation(s)
- Daniela Bruni
- Institute of Immunology, National University of Ireland Maynooth, Maynooth, County Kildare, Ireland
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69
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Nitta S, Sakamoto N, Nakagawa M, Kakinuma S, Mishima K, Kusano-Kitazume A, Kiyohashi K, Murakawa M, Nishimura-Sakurai Y, Azuma S, Tasaka-Fujita M, Asahina Y, Yoneyama M, Fujita T, Watanabe M. Hepatitis C virus NS4B protein targets STING and abrogates RIG-I-mediated type I interferon-dependent innate immunity. Hepatology 2013; 57:46-58. [PMID: 22911572 DOI: 10.1002/hep.26017] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Accepted: 07/24/2012] [Indexed: 12/20/2022]
Abstract
UNLABELLED Hepatitis C virus (HCV) infection blocks cellular interferon (IFN)-mediated antiviral signaling through cleavage of Cardif by HCV-NS3/4A serine protease. Like NS3/4A, NS4B protein strongly blocks IFN-β production signaling mediated by retinoic acid-inducible gene I (RIG-I); however, the underlying molecular mechanisms are not well understood. Recently, the stimulator of interferon genes (STING) was identified as an activator of RIG-I signaling. STING possesses a structural homology domain with flaviviral NS4B, which suggests a direct protein-protein interaction. In the present study, we investigated the molecular mechanisms by which NS4B targets RIG-I-induced and STING-mediated IFN-β production signaling. IFN-β promoter reporter assay showed that IFN-β promoter activation induced by RIG-I or Cardif was significantly suppressed by both NS4B and NS3/4A, whereas STING-induced IFN-β activation was suppressed by NS4B but not by NS3/4A, suggesting that NS4B had a distinct point of interaction. Immunostaining showed that STING colocalized with NS4B in the endoplasmic reticulum. Immunoprecipitation and bimolecular fluorescence complementation (BiFC) assays demonstrated that NS4B specifically bound STING. Intriguingly, NS4B expression blocked the protein interaction between STING and Cardif, which is required for robust IFN-β activation. NS4B truncation assays showed that its N terminus, containing the STING homology domain, was necessary for the suppression of IFN-β promoter activation. NS4B suppressed residual IFN-β activation by an NS3/4A-cleaved Cardif (Cardif1-508), suggesting that NS3/4A and NS4B may cooperate in the blockade of IFN-β production. CONCLUSION NS4B suppresses RIG-I-mediated IFN-β production signaling through a direct protein interaction with STING. Disruption of that interaction may restore cellular antiviral responses and may constitute a novel therapeutic strategy for the eradication of HCV.
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Affiliation(s)
- Sayuri Nitta
- Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan
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70
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Zhao G, An B, Zhou H, Wang H, Xu Y, Xiang X, Dong Z, An F, Yu D, Wang W, Bao S, Xie Q. Impairment of the retinoic acid-inducible gene-I-IFN-β signaling pathway in chronic hepatitis B virus infection. Int J Mol Med 2012; 30:1498-504. [PMID: 22992810 DOI: 10.3892/ijmm.2012.1131] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2012] [Accepted: 07/13/2012] [Indexed: 11/05/2022] Open
Abstract
Chronic hepatitis B (CHB) virus infection is caused by compromised host immunity, but the precise underlying mechanism remains unclear. Retinoic acid-inducible gene I (RIG-I) triggers antiviral immunity by inducing interferon-β (IFN-β) production following viral infection. To investigate the role of the RIG-I-IFN-β signaling pathway in monocyte-derived dendritic cells (moDCs) during CHB infection, moDCs were generated by stimulating CD14+ monocytes in vitro. MoDCs from patients with CHB, acute hepatitis B (AHB) and healthy controls (HCs) were challenged with vesicular stomatitis virus (VSV) and the levels of RIG-I, IFN-β promoter stimulator 1 (IPS-1) and IFN-β in the stimulated moDCs were determined. Following 16 h of VSV stimulation, RIG-I expression was reduced by 50% in moDCs from CHB patients and by 70% in moDCs from AHB patients relative to HC moDCs, concomitant with a 20% decrease in IFN-β expression in CHB patients relative to AHB patients and HCs. Additionally, a significant correlation between the RIG-I/IPS-1 ratio and alanine aminotransferase (ALT) level was observed. To further investigate the function of RIG-I in chronic hepatitis B virus (HBV) infection, HepG2 or HepG2.2.15 (HBV-transformed) cell lines were challenged with VSV following RIG-1 transfection. IFN-β induction was suppressed in HepG2.2.15 cells, but was restored following RIG-I transfection. Taken together, these data indicate that compromised moDC function in CHB patients is attributable to an impaired RIG-I-IFN-β signaling pathway, which results in compromised host viral clearance and HBV persistence in a susceptible population.
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Affiliation(s)
- Gangde Zhao
- Department of Infectious Diseases, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200025, P.R. China
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71
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Wang Y, Tong X, Ye X. Ndfip1 negatively regulates RIG-I-dependent immune signaling by enhancing E3 ligase Smurf1-mediated MAVS degradation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2012; 189:5304-13. [PMID: 23087404 DOI: 10.4049/jimmunol.1201445] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Ndfip1 functions as both a recruiter and an activator of multiple HECT domain E3 ubiquitin ligases of the Nedd4 family. In this study, we demonstrate that Ndfip1 is involved in the ubiquitin-mediated degradation of mitochondrial antiviral signaling (MAVS), which is a key adaptor protein in RIG-I-like receptor-mediated immune signaling. We found that overexpression of Ndfip1 severely impaired MAVS and Sendai virus-mediated activation of IFN-stimulated response element, NF-κB, IFN-β promoter, and polyinosinic-polycytidylic acid or influenza virus RNA-stimulated IRF-3 phosphorylation, as well as the transcription of IFN-β. This functional interaction was confirmed by knockdown of Ndfip1, which facilitated MAVS-mediated downstream signaling and elevated MAVS protein levels. Further analysis indicated that Ndfip1 enhances both self-ubiquitination of HECT domain-containing E3 ubiquitin ligase Smurf1 and its interaction with MAVS, and eventually promotes MAVS degradation. In addition, the activation of IFN-β by MAVS, influenza virus RNA, polyinosinic-polycytidylic acid, and Sendai virus was enhanced in Ndfip1 knockdown cells. These results reveal that Ndfip1 is a potent inhibitor of MAVS-mediated antiviral response.
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Affiliation(s)
- Yetao Wang
- Center for Molecular Immunology, Chinese Academy of Sciences Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
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72
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Impairment of interferon regulatory factor-3 activation by hepatitis C virus core protein basic amino acid region 1. Biochem Biophys Res Commun 2012; 428:494-9. [PMID: 23122814 DOI: 10.1016/j.bbrc.2012.10.079] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 10/22/2012] [Indexed: 12/22/2022]
Abstract
Interferon regulatory factor-3 (IRF-3), a key transcriptional factor in the type I interferon system, is frequently impaired by hepatitis C virus (HCV), in order to establish persistent infection. However, the exact mechanism by which the virus establishes persistent infection has not been fully understood yet. The present study aimed to investigate the effects of various HCV proteins on IRF-3 activation, and elucidate the underlying mechanisms. To achieve this, full-length HCV and HCV subgenomic constructs corresponding to structural and each of the nonstructural proteins were transiently transfected into HepG2 cells. IFN-β induction, plaque formation, and IRF-3 dimerization were elicited by Newcastle disease virus (NDV) infection. The expressions of IRF-3 homodimer and its monomer, Ser386-phosphorylated IRF-3, and HCV core protein were detected by immunofluorescence and western blotting. IFN-β mRNA expression was quantified by real-time PCR (RT-PCR), and IRF-3 activity was measured by the levels of IRF-3 dimerization and phosphorylation, induced by NDV infection or polyriboinosinic:polyribocytidylic acid [poly(I:C)]. Switching of the expression of the complete HCV genome as well as the core proteins, E1, E2, and NS2, suppressed IFN-β mRNA levels and IRF-3 dimerization, induced by NDV infection. Our study revealed a crucial region of the HCV core protein, basic amino acid region 1 (BR1), to inhibit IRF-3 dimerization as well as its phosphorylation induced by NDV infection and poly (I:C), thus interfering with IRF-3 activation. Therefore, our study suggests that rescue of the IRF-3 pathway impairment may be an effective treatment for HCV infection.
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Abstract
The double-stranded RNA-dependent protein kinase PKR plays multiple roles in cells, in response to different stress situations. As a member of the interferon (IFN)‑Stimulated Genes, PKR was initially recognized as an actor in the antiviral action of IFN, due to its ability to control translation, through phosphorylation, of the alpha subunit of eukaryotic initiation factor 2 (eIF2α). As such, PKR participates in the generation of stress granules, or autophagy and a number of viruses have designed strategies to inhibit its action. However, PKR deficient mice resist most viral infections, indicating that PKR may play other roles in the cell other than just acting as an antiviral agent. Indeed, PKR regulates several signaling pathways, either as an adapter protein and/or using its kinase activity. Here we review the role of PKR as an eIF2α kinase, its participation in the regulation of the NF-κB, p38MAPK and insulin pathways, and we focus on its role during infection with the hepatitis C virus (HCV). PKR binds the HCV IRES RNA, cooperates with some functions of the HCV core protein and may represent a target for NS5A or E2. Novel data points out for a role of PKR as a pro-HCV agent, both as an adapter protein and as an eIF2α-kinase, and in cooperation with the di-ubiquitin-like protein ISG15. Developing pharmaceutical inhibitors of PKR may help in resolving some viral infections as well as stress-related damages.
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Affiliation(s)
- Stéphanie Dabo
- Unit Hepacivirus and Innate Immunity, Department Virology, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris Cedex 15, France.
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74
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Vaughan R, Li Y, Fan B, Ranjith-Kumar CT, Kao CC. RNA binding by the NS3 protease of the hepatitis C virus. Virus Res 2012; 169:80-90. [PMID: 22814430 DOI: 10.1016/j.virusres.2012.07.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 07/08/2012] [Accepted: 07/09/2012] [Indexed: 12/22/2022]
Abstract
The hepatitis C virus (HCV) nonstructural protein 3 (NS3) is essential for the processing of the HCV polyprotein, the replication of HCV RNA, and to short circuit innate immunity signaling. NS3 contains an N-terminal domain with protease activity and a C-terminal domain with helicase activity. The two domains communicate with each other along with other HCV and cellular proteins. Herein we show that RNAs can bind directly to the active site cleft of the NS3 protease domain (NS3P) and inhibit proteolysis of peptide substrates. RNAs that are less apt to form intramolecular structures have a stronger inhibitory activity than RNAs with more stable base paired regions. Two mutations in the protease domain that resulted in decreased affinity to ssRNA were also defective in RNA-induced ATPase activity from the helicase domain of NS3. The coordinated effects on inhibition of protease activity and stimulation of ATPase activity raise the possibility that RNA serves as a regulatory switch for the two processes.
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Affiliation(s)
- Robert Vaughan
- The Biochemistry Interdisciplinary Program, Indiana University, Bloomington, IN 47405, USA
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75
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Rustagi A, Doehle BP, McElrath MJ, Gale M. Two new monoclonal antibodies for biochemical and flow cytometric analyses of human interferon regulatory factor-3 activation, turnover, and depletion. Methods 2012; 59:225-32. [PMID: 22705311 DOI: 10.1016/j.ymeth.2012.05.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Revised: 05/04/2012] [Accepted: 05/31/2012] [Indexed: 12/28/2022] Open
Abstract
Interferon regulatory factor-3 (IRF-3) is a master transcription factor that drives the host intracellular innate immune response to virus infection. The importance of IRF-3 in innate immune responses is highlighted by the fact that pathogenic viruses have developed strategies for antagonism of IRF-3. Several tools exist for evaluation of viral regulation of IRF-3 activation and function, but high-quality monoclonal antibodies that mark the differential activation states of human IRF-3 are lacking. To study IRF-3 activation, turnover, and depletion in a high-throughput manner in the context of virus infection, we have developed two new monoclonal antibodies to human IRF-3. These antibodies detect IRF-3 in virus-infected cells in a wide variety of assays and provide a new tool to study virus-host interactions and innate immune signaling.
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Affiliation(s)
- Arjun Rustagi
- Department of Global Health, University of Washington School of Medicine, Seattle, WA 98195-7650, USA.
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76
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Influenza virus protein PB1-F2 inhibits the induction of type I interferon by binding to MAVS and decreasing mitochondrial membrane potential. J Virol 2012; 86:8359-66. [PMID: 22674996 DOI: 10.1128/jvi.01122-12] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PB1-F2 is a small, 87- to 90-amino-acid-long protein encoded by the +1 alternate open reading frame of the PB1 gene of most influenza A virus strains. It has been shown to contribute to viral pathogenicity in a host- and strain-dependent manner, and we have previously discovered that a serine at position 66 (66S) in the PB1-F2 protein increases virulence of the 1918 and H5N1 pandemic viruses. Recently, we have shown that PB1-F2 inhibits the induction of type I interferon (IFN) at the level of the MAVS adaptor protein. However, the molecular mechanism for the IFN antagonist function of PB1-F2 has remained unclear. In the present study, we demonstrated that the C-terminal portion of the PB1-F2 protein binds to MAVS in a region that contains the transmembrane domain. Strikingly, PB1-F2 66S was observed to bind to MAVS more efficiently than PB1-F2 66N. We also tested the effect of PB1-F2 on the IFN antagonist functions of the polymerase proteins PB1, PB2, and PA and observed enhanced IFN inhibition by the PB1 and PB2 proteins in combination with PB1-F2 but not by the PA protein. Using a flow cytometry-based assay, we demonstrate that the PB1-F2 protein inhibits MAVS-mediated IFN synthesis by decreasing the mitochondrial membrane potential (MMP). Interestingly, PB1-F2 66S affected the MMP more efficiently than wild-type PB1-F2. In summary, the results of our study identify the molecular mechanism by which the influenza virus PB1-F2 N66S protein increases virulence.
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Abstract
Arenaviruses include several causative agents of hemorrhagic fever (HF) disease in humans that are associated with high morbidity and significant mortality. Morbidity and lethality associated with HF arenaviruses are believed to involve the dysregulation of the host innate immune and inflammatory responses that leads to impaired development of protective and efficient immunity. The molecular mechanisms underlying this dysregulation are not completely understood, but it is suggested that viral infection leads to disruption of early host defenses and contributes to arenavirus pathogenesis in humans. We demonstrate in the accompanying paper that the prototype member in the family, lymphocytic choriomeningitis virus (LCMV), disables the host innate defense by interfering with type I interferon (IFN-I) production through inhibition of the interferon regulatory factor 3 (IRF3) activation pathway and that the viral nucleoprotein (NP) alone is responsible for this inhibitory effect (C. Pythoud, W. W. Rodrigo, G. Pasqual, S. Rothenberger, L. Martínez-Sobrido, J. C. de la Torre, and S. Kunz, J. Virol. 86:7728-7738, 2012). In this report, we show that LCMV-NP, as well as NPs encoded by representative members of both Old World (OW) and New World (NW) arenaviruses, also inhibits the nuclear translocation and transcriptional activity of the nuclear factor kappa B (NF-κB). Similar to the situation previously reported for IRF3, Tacaribe virus NP (TCRV-NP) does not inhibit NF-κB nuclear translocation and transcriptional activity to levels comparable to those seen with other members in the family. Altogether, our findings demonstrate that arenavirus infection inhibits NF-κB-dependent innate immune and inflammatory responses, possibly playing a key role in the pathogenesis and virulence of arenavirus.
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78
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Wang Y, Tong X, Li G, Li J, Deng M, Ye X. Ankrd17 positively regulates RIG-I-like receptor (RLR)-mediated immune signaling. Eur J Immunol 2012; 42:1304-15. [PMID: 22328336 DOI: 10.1002/eji.201142125] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), such as RIG-I, melanoma differentiation-associated gene 5 (MDA5), and virus-induced signaling adaptor (VISA), are intracellular molecules that sense diverse viral RNAs and trigger immune responses. In this study, we demonstrate that the ankyrin repeat protein ankrd17 interacts with RIG-I, MDA5, and VISA and upregulates RLR-mediated immune signaling. Overexpression of ankrd17 enhances RLR-mediated activation of IRF-3 and NF-κB and upregulates the transcription of IFN-β. It also promotes RLR signaling in response to poly (I:C), influenza virus RNA, and Sendai virus. Consistently, knockdown of ankrd17 impairs RLR signaling. Furthermore, we demonstrate that ankrd17 enhances the interaction of RIG-I and MDA5 with VISA; the ankyrin repeat domain of ankrd17 is required for its interaction with RIG-I as well as for its function in regulating the RLR pathway. Taken together, our results indicate that ankrd17 is a positive regulator of the RLR signaling pathway.
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Affiliation(s)
- Yetao Wang
- Center for Molecular Immunology, CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, P R China
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79
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Shiryaev SA, Thomsen ER, Cieplak P, Chudin E, Cheltsov AV, Chee MS, Kozlov IA, Strongin AY. New details of HCV NS3/4A proteinase functionality revealed by a high-throughput cleavage assay. PLoS One 2012; 7:e35759. [PMID: 22558217 PMCID: PMC3338790 DOI: 10.1371/journal.pone.0035759] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 03/20/2012] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND The hepatitis C virus (HCV) genome encodes a long polyprotein, which is processed by host cell and viral proteases to the individual structural and non-structural (NS) proteins. HCV NS3/4A serine proteinase (NS3/4A) is a non-covalent heterodimer of the N-terminal, ∼180-residue portion of the 631-residue NS3 protein with the NS4A co-factor. NS3/4A cleaves the polyprotein sequence at four specific regions. NS3/4A is essential for viral replication and has been considered an attractive drug target. METHODOLOGY/PRINCIPAL FINDINGS Using a novel multiplex cleavage assay and over 2,660 peptide sequences derived from the polyprotein and from introducing mutations into the known NS3/4A cleavage sites, we obtained the first detailed fingerprint of NS3/4A cleavage preferences. Our data identified structural requirements illuminating the importance of both the short-range (P1-P1') and long-range (P6-P5) interactions in defining the NS3/4A substrate cleavage specificity. A newly observed feature of NS3/4A was a high frequency of either Asp or Glu at both P5 and P6 positions in a subset of the most efficient NS3/4A substrates. In turn, aberrations of this negatively charged sequence such as an insertion of a positively charged or hydrophobic residue between the negatively charged residues resulted in inefficient substrates. Because NS5B misincorporates bases at a high rate, HCV constantly mutates as it replicates. Our analysis revealed that mutations do not interfere with polyprotein processing in over 5,000 HCV isolates indicating a pivotal role of NS3/4A proteolysis in the virus life cycle. CONCLUSIONS/SIGNIFICANCE Our multiplex assay technology in light of the growing appreciation of the role of proteolytic processes in human health and disease will likely have widespread applications in the proteolysis research field and provide new therapeutic opportunities.
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Affiliation(s)
- Sergey A. Shiryaev
- Inflammatory and Infectious Disease Center, Sanford-Burnham Medical Research Institute, La Jolla, California, United States of America
| | - Elliot R. Thomsen
- R&D Department, Prognosys Biosciences Inc., La Jolla, California, United States of America
| | - Piotr Cieplak
- Inflammatory and Infectious Disease Center, Sanford-Burnham Medical Research Institute, La Jolla, California, United States of America
| | - Eugene Chudin
- R&D Department, Prognosys Biosciences Inc., La Jolla, California, United States of America
| | - Anton V. Cheltsov
- Inflammatory and Infectious Disease Center, Sanford-Burnham Medical Research Institute, La Jolla, California, United States of America
| | - Mark S. Chee
- R&D Department, Prognosys Biosciences Inc., La Jolla, California, United States of America
| | - Igor A. Kozlov
- R&D Department, Prognosys Biosciences Inc., La Jolla, California, United States of America
| | - Alex Y. Strongin
- Inflammatory and Infectious Disease Center, Sanford-Burnham Medical Research Institute, La Jolla, California, United States of America
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Xing J, Wang S, Lin R, Mossman KL, Zheng C. Herpes simplex virus 1 tegument protein US11 downmodulates the RLR signaling pathway via direct interaction with RIG-I and MDA-5. J Virol 2012; 86:3528-40. [PMID: 22301138 PMCID: PMC3302539 DOI: 10.1128/jvi.06713-11] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Accepted: 01/17/2012] [Indexed: 12/24/2022] Open
Abstract
The interferon (IFN)-mediated antiviral response is a major defense of the host immune system. In order to complete their life cycle, viruses must modulate host IFN-mediated immune responses. Herpes simplex virus 1 (HSV-1) is a large DNA virus containing more than 80 genes, many of which encode proteins that are involved in virus-host interactions and show immune modulatory capabilities. In this study, we demonstrate that the US11 protein, an RNA binding tegument protein of HSV-1, is a novel antagonist of the beta IFN (IFN-β) pathway. US11 significantly inhibited Sendai virus (SeV)-induced IFN-β production, and its double-stranded RNA (dsRNA) binding domain was indispensable for this inhibition activity. Additionally, wild-type HSV-1 coinfection showed stronger inhibition than US11 mutant HSV-1 in SeV-induced IFN-β production. Coimmunoprecipitation analysis demonstrated that the US11 protein in HSV-1-infected cells interacts with endogenous RIG-I and MDA-5 through its C-terminal RNA-binding domain, which was RNA independent. Expression of US11 in both transfected and HSV-1-infected cells interferes with the interaction between MAVS and RIG-I or MDA-5. Finally, US11 dampens SeV-mediated IRF3 activation. Taken together, the combined data indicate that HSV-1 US11 binds to RIG-I and MDA-5 and inhibits their downstream signaling pathway, preventing the production of IFN-β, which may contribute to the pathogenesis of HSV-1 infection.
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Affiliation(s)
- Junji Xing
- Molecular Virology and Viral Immunology Research Group, State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Shuai Wang
- Molecular Virology and Viral Immunology Research Group, State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Rongtuan Lin
- The Terry Fox Molecular Oncology Group, Lady Davis Institute for Medical Research, Department of Medicine, McGill University, Montreal, Quebec, Canada
| | - Karen L. Mossman
- The Department of Pathology and Molecular Medicine, McMaster Immunology Research Centre, Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
| | - Chunfu Zheng
- Molecular Virology and Viral Immunology Research Group, State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
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81
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Li S, Sun F, Zhang YB, Gui JF, Zhang QY. Identification of DreI as an antiviral factor regulated by RLR signaling pathway. PLoS One 2012; 7:e32427. [PMID: 22412872 PMCID: PMC3296712 DOI: 10.1371/journal.pone.0032427] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 01/26/2012] [Indexed: 12/21/2022] Open
Abstract
Background Retinoic acid-inducible gene I (RIG-I)–like receptors (RLRs) had been demonstrated to prime interferon (IFN) response against viral infection via the conserved RLR signaling in fish, and a novel fish-specific gene, the grass carp reovirus (GCRV)-induced gene 2 (Gig2), had been suggested to play important role in host antiviral response. Methodology/Principal Findings In this study, we cloned and characterized zebrafish Gig2 homolog (named Danio rerio Gig2-I, DreI), and revealed its antiviral role and expressional regulation signaling pathway. RT-PCR, Western blot and promoter activity assay indicate that DreI can be induced by poly I:C, spring viremia of carp virus (SVCV) and recombinant IFN (rIFN), showing that DreI is a typical ISG. Using the pivotal signaling molecules of RLR pathway, including RIG-I, MDA5 and IRF3 from crucian carp, it is found that DreI expression is regulated by RLR cascade and IRF3 plays an important role in this regulation. Furthermore, promoter mutation assay confirms that the IFN-stimulated regulatory elements (ISRE) in the 5′ flanking region of DreI is essential for its induction. Finally, overexpression of DreI leads to establish a strong antiviral state against SVCV and Rana grylio virus (RGV) infection in EPC (Epithelioma papulosum cyprinid) cells. Conclusions/Significance These data indicate that DreI is an antiviral protein, which is regulated by RLR signaling pathway.
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Affiliation(s)
| | | | | | | | - Qi-Ya Zhang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Wuhan Center for Developmental Biology, Institute of Hydrobiology, Graduate School of the Chinese Academy of Sciences, Chinese Academy of Sciences, Wuhan, China
- * E-mail:
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Daba A, Koromilas AE, Pantopoulos K. Alternative ferritin mRNA translation via internal initiation. RNA (NEW YORK, N.Y.) 2012; 18:547-556. [PMID: 22271759 PMCID: PMC3285941 DOI: 10.1261/rna.029322.111] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 12/08/2011] [Indexed: 05/31/2023]
Abstract
Ferritin stores and detoxifies an excess of intracellular iron, and thereby plays an important role in the metabolism of this metal. As unshielded iron promotes oxidative stress, ferritin is crucial in maintaining cellular redox balance and may also modulate cell growth, survival, and apoptosis. The expression of ferritin is controlled by transcriptional and post-transcriptional mechanisms. In light of the well-established transcriptional induction of ferritin by inflammatory signals, we examined how ferritin mRNA translation responds to stress conditions. We first used HT1080 fibrosarcoma cells engineered for coumermycin-inducible expression of PKR, a stress kinase that inhibits protein synthesis in virus-infected cells by phosphorylating eIF2α. In this setting, iron triggered partial ferritin mRNA translation despite a PKR-induced global shutdown in protein synthesis. Moreover, iron-mediated ferritin synthesis was evident in cells infected with an attenuated strain of poliovirus; when eIF4GI was cleaved, eIF2α was phosphorylated, and host protein synthesis was inhibited. Under global inhibition of protein synthesis or specific inhibition of ferritin mRNA translation in cells overexpressing PKR or IRP1, respectively, we demonstrate association of ferritin mRNA with heavy polysomes. Further experiments revealed that the 5' untranslated region (5' UTR) of ferritin mRNA contains a bona fide internal ribosomal entry site (IRES). Our data are consistent with the existence of an alternative, noncanonical mechanism for ferritin mRNA translation, which may primarily operate under stress conditions to protect cells from oxidative stress.
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Affiliation(s)
- Alina Daba
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Quebec H2T 1E2, Canada
- Department of Medicine, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Antonis E. Koromilas
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Quebec H2T 1E2, Canada
- Department of Oncology, McGill University, Montreal, Quebec H2W 1S6, Canada
| | - Kostas Pantopoulos
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, Montreal, Quebec H2T 1E2, Canada
- Department of Medicine, McGill University, Montreal, Quebec H3G 1Y6, Canada
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83
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Coronavirus papain-like proteases negatively regulate antiviral innate immune response through disruption of STING-mediated signaling. PLoS One 2012; 7:e30802. [PMID: 22312431 PMCID: PMC3270028 DOI: 10.1371/journal.pone.0030802] [Citation(s) in RCA: 198] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 12/21/2011] [Indexed: 12/20/2022] Open
Abstract
Viruses have evolved elaborate mechanisms to evade or inactivate the complex system of sensors and signaling molecules that make up the host innate immune response. Here we show that human coronavirus (HCoV) NL63 and severe acute respiratory syndrome (SARS) CoV papain-like proteases (PLP) antagonize innate immune signaling mediated by STING (stimulator of interferon genes, also known as MITA/ERIS/MYPS). STING resides in the endoplasmic reticulum and upon activation, forms dimers which assemble with MAVS, TBK-1 and IKKε, leading to IRF-3 activation and subsequent induction of interferon (IFN). We found that expression of the membrane anchored PLP domain from human HCoV-NL63 (PLP2-TM) or SARS-CoV (PLpro-TM) inhibits STING-mediated activation of IRF-3 nuclear translocation and induction of IRF-3 dependent promoters. Both catalytically active and inactive forms of CoV PLPs co-immunoprecipitated with STING, and viral replicase proteins co-localize with STING in HCoV-NL63-infected cells. Ectopic expression of catalytically active PLP2-TM blocks STING dimer formation and negatively regulates assembly of STING-MAVS-TBK1/IKKε complexes required for activation of IRF-3. STING dimerization was also substantially reduced in cells infected with SARS-CoV. Furthermore, the level of ubiquitinated forms of STING, RIG-I, TBK1 and IRF-3 are reduced in cells expressing wild type or catalytic mutants of PLP2-TM, likely contributing to disruption of signaling required for IFN induction. These results describe a new mechanism used by CoVs in which CoV PLPs negatively regulate antiviral defenses by disrupting the STING-mediated IFN induction.
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84
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Williamson CD, DeBiasi RL, Colberg-Poley AM. Viral product trafficking to mitochondria, mechanisms and roles in pathogenesis. Infect Disord Drug Targets 2012; 12:18-37. [PMID: 22034933 PMCID: PMC4435936 DOI: 10.2174/187152612798994948] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 04/21/2011] [Accepted: 05/02/2011] [Indexed: 05/31/2023]
Abstract
A wide variety of viruses cause significant morbidity and mortality in humans. However, targeted antiviral therapies have been developed for only a subset of these viruses, with the majority of currently licensed antiviral drugs targeting viral entry, replication or exit steps during the viral life cycle. Due to increasing emergence of antiviral drug resistant viruses, the isolation of multiple viral subtypes, and toxicities of existing therapies, there remains an urgent need for the timely development of novel antiviral agents, including those targeting host factors essential for viral replication. This review summarizes viral products that target mitochondria and their effects on common mitochondria regulated pathways. These viral products and the mitochondrial pathways affected by them provide potential novel targets for the rational design of antiviral drugs. Viral products alter oxidative balance, mitochondrial permeability transition pore, mitochondrial membrane potential, electron transport and energy production. Moreover, viruses may cause the Warburg Effect, in which metabolism is reprogrammed to aerobic glycolysis as the main source of energy. Finally, viral products affect proapoptotic and antiapoptotic signaling, as well as mitochondrial innate immune signaling. Because of their importance for the generation of metabolic intermediates and energy as well as cell survival, mitochondrial pathways are targeted by multiple independent viral products. Structural modifications of existing drugs targeted to mitochondrial pathways may lead to the development of novel antiviral drugs with improved efficacy and reduced toxicity.
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Affiliation(s)
- Chad D. Williamson
- Center for Cancer and Immunology Research, Children’s National Medical Center, 111 Michigan Avenue, NW, Washington, DC 20010
| | - Roberta L. DeBiasi
- Center for Cancer and Immunology Research, Children’s National Medical Center, 111 Michigan Avenue, NW, Washington, DC 20010
- Division of Pediatric Infectious Diseases, Children’s National Medical Center, 111 Michigan Avenue, NW, Washington, DC 20010
- Department of Pediatrics, George Washington University School of Medicine and Health Sciences, Washington DC 20037 Tel. 202-476-3984 FAX 202-476-3929
| | - Anamaris M. Colberg-Poley
- Center for Cancer and Immunology Research, Children’s National Medical Center, 111 Michigan Avenue, NW, Washington, DC 20010
- Department of Pediatrics, George Washington University School of Medicine and Health Sciences, Washington DC 20037 Tel. 202-476-3984 FAX 202-476-3929
- Department of Biochemistry and Molecular Biology, George Washington University School of Medicine and Health Sciences, Washington DC 20037 Tel. 202-476-3984 FAX 202-476-3929
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85
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Bleiblo F, Michael P, Brabant D, Ramana CV, Tai TC, Saleh M, Parrillo JE, Kumar A, Kumar A. The role of immunostimulatory nucleic acids in septic shock. Int J Clin Exp Med 2012; 5:1-23. [PMID: 22328944 PMCID: PMC3272682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 01/08/2012] [Indexed: 05/31/2023]
Abstract
Sepsis and its associated syndromes represent the systemic host response to severe infection and is manifested by varying degrees of hypotension, coagulopathy, and multiorgan dysfunction. Despite great efforts being made to understand this condition and designing therapies to treat sepsis, mortality rates are still high in septic patients. Characterization of the complex molecular signaling networks between the various components of host-pathogen interactions, highlights the difficulty in identifying a single driving force responsible for sepsis. Although triggering the inflammatory response is generally considered as protective against pathogenic threats, the interplay between the signaling pathways that are induced or suppressed during sepsis may harm the host. Numerous surveillance mechanisms have evolved to discriminate self from foreign agents and accordingly provoke an effective cellular response to target the pathogens. Nucleic acids are not only an essential genetic component, but sensing their molecular signature is also an important quality control mechanism which has evolved to maintain the integrity of the human genome. Evidence that has accumulated recently indicated that distinct pattern recognition receptors sense nucleic acids released from infectious organisms or from damaged host cells, resulting in the modulation of intracellular signalling cascades. Immunoreceptor-mediated detection of these nucleic acids induces antigen-specific immunity, secretion of proinflammatory cytokines and reactive oxygen/nitrogen species and thus are implicated in a range of diseases including septic shock.
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Affiliation(s)
- Farag Bleiblo
- Department of Chemistry and Biochemistry and the Biomolecular Sciences Programme, Laurentian UniversitySudbury, ON, Canada, P3E 2C6
| | - Paul Michael
- Department of Chemistry and Biochemistry and the Biomolecular Sciences Programme, Laurentian UniversitySudbury, ON, Canada, P3E 2C6
| | - Danielle Brabant
- Department of Chemistry and Biochemistry and the Biomolecular Sciences Programme, Laurentian UniversitySudbury, ON, Canada, P3E 2C6
| | | | - TC Tai
- Department of Chemistry and Biochemistry and the Biomolecular Sciences Programme, Laurentian UniversitySudbury, ON, Canada, P3E 2C6
| | - Mazen Saleh
- Department of Chemistry and Biochemistry and the Biomolecular Sciences Programme, Laurentian UniversitySudbury, ON, Canada, P3E 2C6
| | - Joseph E Parrillo
- Division of Cardiovascular Disease and Critical Care Medicine, Cooper University Hospital, Robert Wood Johnson Medical SchoolCamden, New Jersey, USA, 08103
| | - Anand Kumar
- Section of Critical Care Medicine, University of ManitobaWinnipeg, MB, Canada, R3A 1R9
| | - Aseem Kumar
- Department of Chemistry and Biochemistry and the Biomolecular Sciences Programme, Laurentian UniversitySudbury, ON, Canada, P3E 2C6
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Tal MC, Iwasaki A. Mitoxosome: a mitochondrial platform for cross-talk between cellular stress and antiviral signaling. Immunol Rev 2011; 243:215-34. [PMID: 21884179 DOI: 10.1111/j.1600-065x.2011.01038.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Evidence is accumulating that the mitochondria form an integral platform from which innate signaling takes place. Recent studies revealed that the mitochondria are shaping the innate response to intracellular pathogens, and mitochondrial function is modulating and being modulated by innate immune signaling. Further, cell biologic analyses have uncovered the dynamic relocalization of key components involved in cytosolic viral recognition and signaling to the mitochondria, as well as the mobilization of mitochondria to the sites of viral replication. In this review, we provide an integrated view of how cellular stress and signals following cytosolic viral recognition are intimately linked and coordinated at the mitochondria. We incorporate recent findings into our current understanding of the role of mitochondrial function in antiviral immunity and suggest the existence of a 'mitoxosome', a mitochondrial oxidative signalosome where multiple pathways of viral recognition and cellular stress converge on the surface of the mitochondria to facilitate a coordinated antiviral response.
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Affiliation(s)
- Michal Caspi Tal
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
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87
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Poly(C)-binding protein 1 (PCBP1) mediates housekeeping degradation of mitochondrial antiviral signaling (MAVS). Cell Res 2011; 22:717-27. [PMID: 22105485 DOI: 10.1038/cr.2011.184] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mitochondrial antiviral signaling (MAVS) is a key adaptor in cellular antiviral innate immunity. We previously identified poly(C)-binding protein 2 (PCBP2) as a feedback inhibitor of MAVS that facilitates its degradation after viral infection, but little is known about the regulatory potential of poly(C)-binding protein 1 (PCBP1), which highly resembles PCBP2. Here we report that PCBP1 mediates housekeeping degradation of MAVS using the same mechanism as PCBP2 employs. Overexpression of PCBP1 impairs MAVS-mediated antiviral responses, while knockdown of PCBP1 exerts the opposite effect. The suppression is due to PCBP1-induced MAVS degradation. We observe that PCBP1 and PCBP2 show synergy in MAVS inhibition, but their expression patterns are distinct: PCBP1 is stably and abundantly expressed, while PCBP2 shows low basal expression with rapid induction after infection. Individual knockdown and subcellular fractionation analyses reveal that unlike the postinfection inhibitor PCBP2, PCBP1 continuously eliminates cellular MAVS. Our findings unravel a critical role of PCBP1 in regulating MAVS for both fine-tuning the antiviral immunity and preventing inflammation.
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88
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IκB kinase ε-dependent phosphorylation and degradation of X-linked inhibitor of apoptosis sensitizes cells to virus-induced apoptosis. J Virol 2011; 86:726-37. [PMID: 22072751 DOI: 10.1128/jvi.05989-11] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
X-linked inhibitor of apoptosis (XIAP) is a potent antagonist of caspase 3-, 7-, and 9-dependent apoptotic activities that functions as an E3 ubiquitin ligase, and it targets caspases for degradation. In this study, we demonstrate that Sendai virus (SeV) infection results in the IKKε- or TBK1-mediated phosphorylation of XIAP in vivo at Ser430, resulting in Lys(48)-linked autoubiquitination at Lys322/328 residues, followed by the subsequent proteasomal degradation of XIAP. Interestingly, IKKε expression and XIAP turnover increases SeV-triggered mitochondrion-dependent apoptosis via the release of caspase 3, whereas TBK1 expression does not increase apoptosis. Interestingly, phosphorylation also regulates XIAP interaction with the transcription factor IRF3, suggesting a role in IRF3-Bax-mediated apoptosis. Our findings reveal a novel function of IKKε as a regulator of the virus-induced triggering of apoptosis via the phosphorylation-dependent turnover of XIAP.
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89
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Yang D, Liu N, Zuo C, Lei S, Wu X, Zhou F, Liu C, Zhu H. Innate host response in primary human hepatocytes with hepatitis C virus infection. PLoS One 2011; 6:e27552. [PMID: 22087337 PMCID: PMC3210809 DOI: 10.1371/journal.pone.0027552] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2011] [Accepted: 10/19/2011] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND AND AIM The interaction between hepatitis C virus (HCV) and innate antiviral defense systems in primary human hepatocytes is not well understood. The objective of this study is to examine how primary human hepatocytes response to HCV infection. METHODS An infectious HCV isolate JFH1 was used to infect isolated primary human hepatocytes. HCV RNA or NS5A protein in the cells was detected by real-time PCR or immunofluorescence staining respectively. Apoptosis was examined with flow cytometry. Mechanisms of HCV-induced IFN-β expression and apoptosis were determined. RESULTS Primary human hepatocytes were susceptible to JFH1 virus and released infectious virus. IFN-α inhibited viral RNA replication in the cells. IFN-β and interferon-stimulated genes were induced in the cells during acute infection. HCV infection induced apoptosis of primary human hepatocytes through the TRAIL-mediated pathway. Silencing RIG-I expression in primary human hepatocytes inhibited IFN-β and TRAIL expression and blocked apoptosis of the cells, which facilitated viral RNA replication in the cells. Moreover, HCV NS34A protein inhibited viral induced IFN-β expression in primary human hepatocytes. CONCLUSION Innate host response is intact in HCV-infected primary human hepatocytes. RIG-I plays a key role in the induction of IFN and TRAIL by viruses and apoptosis of primary human hepatocytes via activation of the TRAIL-mediated pathway. HCV NS34A protein appears to be capable of disrupting the innate antiviral host responses in primary human hepatocytes. Our study provides a novel mechanism by which primary human hepatocytes respond to natural HCV infection.
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Affiliation(s)
- Darong Yang
- Department of Molecular Medicine, College of Biology of Hunan University, Changsha, China
- State Key Laboratory of Chem/Biosensesing and Chemometrics, Hunan University, Changsha, China
| | - Nianli Liu
- Department of Molecular Medicine, College of Biology of Hunan University, Changsha, China
- State Key Laboratory of Chem/Biosensesing and Chemometrics, Hunan University, Changsha, China
| | - Chaohui Zuo
- Research Center of Cancer Prevention and Treatment of Hunan University and Hunan Provincial Tumor Hospital, Hunan Provincial Tumor Hospital, Changsha, China
| | - Shoahua Lei
- Department of Molecular Medicine, College of Biology of Hunan University, Changsha, China
- State Key Laboratory of Chem/Biosensesing and Chemometrics, Hunan University, Changsha, China
| | - Xinjiao Wu
- Department of Molecular Medicine, College of Biology of Hunan University, Changsha, China
- State Key Laboratory of Chem/Biosensesing and Chemometrics, Hunan University, Changsha, China
| | - Fei Zhou
- Department of Molecular Medicine, College of Biology of Hunan University, Changsha, China
- State Key Laboratory of Chem/Biosensesing and Chemometrics, Hunan University, Changsha, China
| | - Chen Liu
- Department of Pathology, Immunology and Laboratory Medicine, University of Florida College of Medicine, Gainesville, Florida, United States of America
| | - Haizhen Zhu
- Department of Molecular Medicine, College of Biology of Hunan University, Changsha, China
- State Key Laboratory of Chem/Biosensesing and Chemometrics, Hunan University, Changsha, China
- Research Center of Cancer Prevention and Treatment of Hunan University and Hunan Provincial Tumor Hospital, Hunan Provincial Tumor Hospital, Changsha, China
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90
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Horner SM, Liu HM, Park HS, Briley J, Gale M. Mitochondrial-associated endoplasmic reticulum membranes (MAM) form innate immune synapses and are targeted by hepatitis C virus. Proc Natl Acad Sci U S A 2011; 108:14590-5. [PMID: 21844353 PMCID: PMC3167523 DOI: 10.1073/pnas.1110133108] [Citation(s) in RCA: 371] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
RIG-I is a cytosolic pathogen recognition receptor that engages viral RNA in infected cells to trigger innate immune defenses through its adaptor protein MAVS. MAVS resides on mitochondria and peroxisomes, but how its signaling is coordinated among these organelles has not been defined. Here we show that a major site of MAVS signaling is the mitochondrial-associated membrane (MAM), a distinct membrane compartment that links the endoplasmic reticulum to mitochondria. During RNA virus infection, RIG-I is recruited to the MAM to bind MAVS. Dynamic MAM tethering to mitochondria and peroxisomes then coordinates MAVS localization to form a signaling synapse between membranes. Importantly, the hepatitis C virus NS3/4A protease, which cleaves MAVS to support persistent infection, targets this synapse for MAVS proteolysis from the MAM, but not from mitochondria, to ablate RIG-I signaling of immune defenses. Thus, the MAM mediates an intracellular immune synapse that directs antiviral innate immunity.
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Affiliation(s)
- Stacy M. Horner
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195
| | - Helene Minyi Liu
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195
| | - Hae Soo Park
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195
| | - Jessica Briley
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195
| | - Michael Gale
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195
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91
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Varicella-zoster virus immediate-early protein ORF61 abrogates the IRF3-mediated innate immune response through degradation of activated IRF3. J Virol 2011; 85:11079-89. [PMID: 21835786 DOI: 10.1128/jvi.05098-11] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Varicella-zoster virus (VZV) infection of differentiated cells within the host and establishment of latency likely requires evasion of innate immunity and limits secretion of antiviral cytokines. Here we report that its immediate-early protein ORF61 antagonizes the beta interferon (IFN-β) pathway. VZV infection down-modulated the Sendai virus (SeV)-activated IFN-β pathway, including mRNA of IFN-β and its downstream interferon-stimulated genes (ISGs), ISG54 and ISG56. Through a primary screening of VZV genes, we found that ORF61 inhibited SeV-mediated activation of IFN-β and ISRE (IFN-stimulated response element) promoter activities but only slightly affected NF-κB promoter activity, implying that the IFN-β pathway may be blocked in the IRF3 branch. An indirect immunofluorescence assay demonstrated that ectopic expression of ORF61 abrogated the detection of IRF3 in SeV-infected cells; however, it did not affect endogenous dormant IRF3 in noninfected cells. Additionally, ORF61 was shown to be partially colocalized with activated IRF3 in the nucleus upon treatment with MG132, an inhibitor of proteasomes, and the direct interaction between ORF61 and activated IRF3 was confirmed by a coimmunoprecipitation assay. Furthermore, Western blot analysis demonstrated that activated IRF3 was ubiquitinated in the presence of ORF61, suggesting that ORF61 degraded phosphorylated IRF3 via a ubiquitin-proteasome pathway. Semiquantitative reverse transcription-PCR (RT-PCR) analysis demonstrated that the level of ISG54 and ISG56 mRNAs was also downregulated by ORF61. Taken together, our results convincingly demonstrate that ORF61 down-modulates the IRF3-mediated IFN-β pathway by degradation of activated IRF3 via direct interaction, which may contribute to the pathogenesis of VZV infection.
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92
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Liu XY, Chen W, Wei B, Shan YF, Wang C. IFN-induced TPR protein IFIT3 potentiates antiviral signaling by bridging MAVS and TBK1. THE JOURNAL OF IMMUNOLOGY 2011; 187:2559-68. [PMID: 21813773 DOI: 10.4049/jimmunol.1100963] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intracellular RNA viruses are sensed by receptors retinoic acid-inducible gene I/MDA5, which trigger formation of the mitochondrial antiviral signaling (MAVS) complex on mitochondria. Consequently, this leads to the activation of TNFR-associated factor family member-associated NF-κB activator-binding kinase 1 (TBK1) and phosphorylation of IFN regulatory factor 3 (IRF3). It remains to be elucidated how MAVS activates TBK1/IRF3. In this study, we report that IFN-induced protein with tetratricopeptide repeats 3 (IFIT3) is significantly induced upon RNA virus infection. Ectopic expression or knockdown of IFIT3 could, respectively, enhance or impair IRF3-mediated gene expression. Mechanistically, the tetratrico-peptide repeat motif (E164/E165) of IFIT3 interacts with the N terminus (K38) of TBK1, thus bridging TBK1 to MAVS on the mitochondrion. Disruption of this interaction markedly attenuates the activation of TBK1 and IRF3. Furthermore, host antiviral responses are significantly boosted or crippled in the presence or absence of IFIT3. Collectively, our study characterizes IFIT3 as an important modulator in innate immunity, revealing a new function of the IFIT family proteins (IFN-induced protein with tetratricopeptide repeats).
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Affiliation(s)
- Xin-Yi Liu
- Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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Abstract
The RIG-I-like receptors (RLRs) RIG-I, MDA5, and LGP2 play a major role in pathogen sensing of RNA virus infection to initiate and modulate antiviral immunity. The RLRs detect viral RNA ligands or processed self RNA in the cytoplasm to trigger innate immunity and inflammation and to impart gene expression that serves to control infection. Importantly, RLRs cooperate in signaling crosstalk networks with Toll-like receptors and other factors to impart innate immunity and to modulate the adaptive immune response. RLR regulation occurs at a variety of levels ranging from autoregulation to ligand and cofactor interactions and posttranslational modifications. Abberant RLR signaling or dysregulation of RLR expression is now implicated in the development of autoimmune diseases. Understanding the processes of RLR signaling and response will provide insights to guide RLR-targeted therapeutics for antiviral and immune-modifying applications.
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Affiliation(s)
- Yueh-Ming Loo
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195-7650, USA
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94
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Pertel T, Reinhard C, Luban J. Vpx rescues HIV-1 transduction of dendritic cells from the antiviral state established by type 1 interferon. Retrovirology 2011; 8:49. [PMID: 21696578 PMCID: PMC3130655 DOI: 10.1186/1742-4690-8-49] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Accepted: 06/22/2011] [Indexed: 01/08/2023] Open
Abstract
Background Vpx is a virion-associated protein encoded by SIVSM, a lentivirus endemic to the West African sooty mangabey (Cercocebus atys). HIV-2 and SIVMAC, zoonoses resulting from SIVSM transmission to humans or Asian rhesus macaques (Macaca mulatta), also encode Vpx. In myeloid cells, Vpx promotes reverse transcription and transduction by these viruses. This activity correlates with Vpx binding to DCAF1 (VPRBP) and association with the DDB1/RBX1/CUL4A E3 ubiquitin ligase complex. When delivered experimentally to myeloid cells using VSV G-pseudotyped virus-like particles (VLPs), Vpx promotes reverse transcription of retroviruses that do not normally encode Vpx. Results Here we show that Vpx has the extraordinary ability to completely rescue HIV-1 transduction of human monocyte-derived dendritic cells (MDDCs) from the potent antiviral state established by prior treatment with exogenous type 1 interferon (IFN). The magnitude of rescue was up to 1,000-fold, depending on the blood donor, and was also observed after induction of endogenous IFN and IFN-stimulated genes (ISGs) by LPS, poly(I:C), or poly(dA:dT). The effect was relatively specific in that Vpx-associated suppression of soluble IFN-β production, of mRNA levels for ISGs, or of cell surface markers for MDDC differentiation, was not detected. Vpx did not rescue HIV-2 or SIVMAC transduction from the antiviral state, even in the presence of SIVMAC or HIV-2 VLPs bearing additional Vpx, or in the presence of HIV-1 VLPs bearing all accessory genes. In contrast to the effect of Vpx on transduction of untreated MDDCs, HIV-1 rescue from the antiviral state was not dependent upon Vpx interaction with DCAF1 or on the presence of DCAF1 within the MDDC target cells. Additionally, although Vpx increased the level of HIV-1 reverse transcripts in MDDCs to the same extent whether or not MDDCs were treated with IFN or LPS, Vpx rescued a block specific to the antiviral state that occurred after HIV-1 cDNA penetrated the nucleus. Conclusion Vpx provides a tool for the characterization of a potent, new HIV-1 restriction activity, which acts in the nucleus of type 1 IFN-treated dendritic cells.
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Affiliation(s)
- Thomas Pertel
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
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95
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Onomoto K, Onoguchi K, Takahasi K, Fujita T. Type I interferon production induced by RIG-I-like receptors. J Interferon Cytokine Res 2011; 30:875-81. [PMID: 21121861 DOI: 10.1089/jir.2010.0117] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Type I interferon (IFN) is produced in a variety of tissues in the body in response to viral infections. Recent studies have revealed that cytoplasmic receptors for viral (nonself) RNA are responsible for triggering IFN production. Different viruses activate different sensors. Numerous signaling adaptors are reported to participate in the regulation of the IFN gene's activation. In this paper, the role of free polyubiquitine chains in the activation of retinoic acid inducible gene I (RIG-I)-like receptors and the involvement of mitochondria as a signaling platform in the modulation of RIG-I-like receptor signaling is reviewed.
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Affiliation(s)
- Koji Onomoto
- Department of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
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96
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Abstract
The innate immune system has a key role in the mammalian immune response. Recent research has demonstrated that mitochondria participate in a broad range of innate immune pathways, functioning as signalling platforms and contributing to effector responses. In addition to regulating antiviral signalling, mounting evidence suggests that mitochondria facilitate antibacterial immunity by generating reactive oxygen species and contribute to innate immune activation following cellular damage and stress. Therefore, in addition to their well-appreciated roles in cellular metabolism and programmed cell death, mitochondria appear to function as centrally positioned hubs in the innate immune system. Here, we review the emerging knowledge about the roles of mitochondria in innate immunity.
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Affiliation(s)
- A Phillip West
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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97
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Liu F, Gu J. Retinoic acid inducible gene-I, more than a virus sensor. Protein Cell 2011; 2:351-7. [PMID: 21626268 PMCID: PMC4875335 DOI: 10.1007/s13238-011-1045-y] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Accepted: 04/11/2011] [Indexed: 12/24/2022] Open
Abstract
Retinoic acid inducible gene-I (RIG-I) is a caspase recruitment domain (CARD) containing protein that acts as an intracellular RNA receptor and senses virus infection. After binding to double stranded RNA (dsRNA) or 5'-triphosphate single stranded RNA (ssRNA), RIG-I transforms into an open conformation, translocates onto mitochondria, and interacts with the downstream adaptor mitochondrial antiviral signaling (MAVS) to induce the production of type I interferon and inflammatory factors via IRF3/7 and NF-κB pathways, respectively. Recently, accumulating evidence suggests that RIG-I could function in non-viral systems and participate in a series of biological events, such as inflammation and inflammation related diseases, cell proliferation, apoptosis and even senescence. Here we review recent advances in antiviral study of RIG-I as well as the functions of RIG-I in other fields.
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Affiliation(s)
- Feng Liu
- National Key Laboratory of Protein Engineering and Plant Gene Engineering, LSC, Peking University, Beijing, 100871 China
| | - Jun Gu
- National Key Laboratory of Protein Engineering and Plant Gene Engineering, LSC, Peking University, Beijing, 100871 China
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98
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Wang C, Liu X, Wei B. Mitochondrion: an emerging platform critical for host antiviral signaling. Expert Opin Ther Targets 2011; 15:647-65. [PMID: 21476879 DOI: 10.1517/14728222.2011.561321] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Toll-like receptors (TLRs) and cytoplasmic retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) are the two major receptor systems for detecting RNA viruses. RLRs play essential roles within the cytosol of various cell types. The signaling pathways converge at the mitochondrial antiviral signalling protein (MAVS) on the outer membrane of mitochondria. Recent research has surprisingly shown that many mitochondrial intrinsic factors play novel functions in RLR signaling, conferring a new perspective of therapeutic drug design to inhibit viral infection. AREAS COVERED This review covers the literature of the past 6 years and summarizes the components, regulation and mechanisms of RLR signaling, highlighting the function and regulation of mitochondrial proteins, such as MAVS and translocase of outer membrane (Tom)70 in this process. The authors attempt to delineate the complicated cross-talk among subcellular organelles in the context of intracellular antiviral signaling. EXPERT OPINION It is imperative to elucidate the specific roles and mechanisms of post-translational modifications in MAVS signaling. The sub-cellular dynamics of regulatory proteins should be correlated with their multiple functions. Animal models are needed to further probe the integration of mitochondria with innate immunity evolutionarily; they will be instrumental for identifying novel antiviral targets and, ultimately, for developing specific clinical drugs.
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Affiliation(s)
- Chen Wang
- Shanghai Institutes for Biological Sciences-Institute of Biochemistry and Cell Biology, Shanghai, China.
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99
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Solis M, Nakhaei P, Jalalirad M, Lacoste J, Douville R, Arguello M, Zhao T, Laughrea M, Wainberg MA, Hiscott J. RIG-I-mediated antiviral signaling is inhibited in HIV-1 infection by a protease-mediated sequestration of RIG-I. J Virol 2011; 85:1224-36. [PMID: 21084468 PMCID: PMC3020501 DOI: 10.1128/jvi.01635-10] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 11/10/2010] [Indexed: 12/24/2022] Open
Abstract
The rapid induction of type I interferon (IFN) is essential for establishing innate antiviral responses. During infection, cytoplasmic viral RNA is sensed by two DExD/H box RNA helicases, RIG-I and MDA5, ultimately driving IFN production. Here, we demonstrate that purified genomic RNA from HIV-1 induces a RIG-I-dependent type I IFN response. Both the dimeric and monomeric forms of HIV-1 were sensed by RIG-I, but not MDA5, with monomeric RNA, usually found in defective HIV-1 particles, acting as a better inducer of IFN than dimeric RNA. However, despite the presence of HIV-1 RNA in the de novo infection of monocyte-derived macrophages, HIV-1 replication did not lead to a substantial induction of IFN signaling. We demonstrate the existence of an evasion mechanism based on the inhibition of the RIG-I sensor through the action of the HIV-1 protease (PR). Indeed, the ectopic expression of PR resulted in the inhibition of IFN regulatory factor 3 (IRF-3) phosphorylation and decreased expression of IFN and interferon-stimulated genes. A downregulation of cytoplasmic RIG-I levels occurred in cells undergoing a single-cycle infection with wild-type provirus BH10 but not in cells transfected with a protease-deficient provirus, BH10-PR(-). Cellular fractionation and confocal microscopy studies revealed that RIG-I translocated from the cytosol to an insoluble fraction during the de novo HIV-1 infection of monocyte-derived macrophages, in the presence of PR. The loss of cytoplasmic RIG-I was prevented by the lysosomal inhibitor E64, suggesting that PR targets RIG-I to the lysosomes. This study reveals a novel PR-dependent mechanism employed by HIV-1 to counteract the early IFN response to viral RNA in infected cells.
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Affiliation(s)
- Mayra Solis
- Terry Fox Molecular Oncology Group, Lady Davis Institute, Jewish General Hospital, Departments of Microbiology and Immunology and Medicine, McGill University, McGill AIDS Center, Lady Davis Institute, Jewish General Hospital, Department of Biology, McGill University, Montreal, Quebec H3T1E2, Canada
| | - Peyman Nakhaei
- Terry Fox Molecular Oncology Group, Lady Davis Institute, Jewish General Hospital, Departments of Microbiology and Immunology and Medicine, McGill University, McGill AIDS Center, Lady Davis Institute, Jewish General Hospital, Department of Biology, McGill University, Montreal, Quebec H3T1E2, Canada
| | - Mohammad Jalalirad
- Terry Fox Molecular Oncology Group, Lady Davis Institute, Jewish General Hospital, Departments of Microbiology and Immunology and Medicine, McGill University, McGill AIDS Center, Lady Davis Institute, Jewish General Hospital, Department of Biology, McGill University, Montreal, Quebec H3T1E2, Canada
| | - Judith Lacoste
- Terry Fox Molecular Oncology Group, Lady Davis Institute, Jewish General Hospital, Departments of Microbiology and Immunology and Medicine, McGill University, McGill AIDS Center, Lady Davis Institute, Jewish General Hospital, Department of Biology, McGill University, Montreal, Quebec H3T1E2, Canada
| | - Renée Douville
- Terry Fox Molecular Oncology Group, Lady Davis Institute, Jewish General Hospital, Departments of Microbiology and Immunology and Medicine, McGill University, McGill AIDS Center, Lady Davis Institute, Jewish General Hospital, Department of Biology, McGill University, Montreal, Quebec H3T1E2, Canada
| | - Meztli Arguello
- Terry Fox Molecular Oncology Group, Lady Davis Institute, Jewish General Hospital, Departments of Microbiology and Immunology and Medicine, McGill University, McGill AIDS Center, Lady Davis Institute, Jewish General Hospital, Department of Biology, McGill University, Montreal, Quebec H3T1E2, Canada
| | - Tiejun Zhao
- Terry Fox Molecular Oncology Group, Lady Davis Institute, Jewish General Hospital, Departments of Microbiology and Immunology and Medicine, McGill University, McGill AIDS Center, Lady Davis Institute, Jewish General Hospital, Department of Biology, McGill University, Montreal, Quebec H3T1E2, Canada
| | - Michael Laughrea
- Terry Fox Molecular Oncology Group, Lady Davis Institute, Jewish General Hospital, Departments of Microbiology and Immunology and Medicine, McGill University, McGill AIDS Center, Lady Davis Institute, Jewish General Hospital, Department of Biology, McGill University, Montreal, Quebec H3T1E2, Canada
| | - Mark A. Wainberg
- Terry Fox Molecular Oncology Group, Lady Davis Institute, Jewish General Hospital, Departments of Microbiology and Immunology and Medicine, McGill University, McGill AIDS Center, Lady Davis Institute, Jewish General Hospital, Department of Biology, McGill University, Montreal, Quebec H3T1E2, Canada
| | - John Hiscott
- Terry Fox Molecular Oncology Group, Lady Davis Institute, Jewish General Hospital, Departments of Microbiology and Immunology and Medicine, McGill University, McGill AIDS Center, Lady Davis Institute, Jewish General Hospital, Department of Biology, McGill University, Montreal, Quebec H3T1E2, Canada
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Abstract
Antiviral innate immunity is triggered by sensing viral nucleic acids. RIG-I (retinoic acid-inducible gene-I) is an intracellular molecule that responds to viral nucleic acids and activates downstream signaling, resulting in the induction of members of the type I interferon (IFN) family, which are regarded among the most important effectors of the innate immune system. Although RIG-I is expressed ubiquitously in the cytoplasm, its levels are subject to transcriptional and post-transcriptional regulation. RIG-I belongs to the IFN-stimulated gene (ISG) family, but certain cells regulate its expression through IFN-independent mechanisms. Several lines of evidence indicate that deregulated RIG-I signaling is associated with autoimmune disorders. Further studies suggest that RIG-I has functions in addition to those directly related to its role in RNA sensing and host defense. We have much to learn and discover regarding this interesting cytoplasmic sensor so that we can capitalize on its properties for the treatment of viral infections, immune disorders, cancer, and perhaps other conditions.
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Affiliation(s)
- Tomoh Matsumiya
- Department of Vascular Biology, Institute of Brain Science, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
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