2351
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Barral PM, Sarkar D, Su ZZ, Barber GN, DeSalle R, Racaniello VR, Fisher PB. Functions of the cytoplasmic RNA sensors RIG-I and MDA-5: key regulators of innate immunity. Pharmacol Ther 2009; 124:219-34. [PMID: 19615405 DOI: 10.1016/j.pharmthera.2009.06.012] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 06/22/2009] [Indexed: 12/13/2022]
Abstract
The innate immune system responds within minutes of infection to produce type I interferons and pro-inflammatory cytokines. Interferons induce the synthesis of cell proteins with antiviral activity, and also shape the adaptive immune response by priming T cells. Despite the discovery of interferons over 50 years ago, only recently have we begun to understand how cells sense the presence of a virus infection. Two families of pattern recognition receptors have been shown to distinguish unique molecules present in pathogens, such as bacterial and fungal cell wall components, viral RNA and DNA, and lipoproteins. The first family includes the membrane-bound toll-like receptors (TLRs). Studies of the signaling pathways that lead from pattern recognition to cytokine induction have revealed extensive and overlapping cascades that involve protein-protein interactions and phosphorylation, and culminate in activation of transcription proteins that control the transcription of genes encoding interferons and other cytokines. A second family of pattern recognition receptors has recently been identified, which comprises the cytoplasmic sensors of viral nucleic acids, including MDA-5, RIG-I, and LGP2. In this review we summarize the discovery of these cytoplasmic sensors, how they recognize nucleic acids, the signaling pathways leading to cytokine synthesis, and viral countermeasures that have evolved to antagonize the functions of these proteins. We also consider the function of these cytoplasmic sensors in apoptosis, development and differentiation, and diabetes.
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Affiliation(s)
- Paola M Barral
- Department of Human and Molecular Genetics, Virginia Commonwealth University, School of Medicine, Richmond, VA, USA.
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2352
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Abstract
The discovery of molecular sensors that enable eukaryotes to recognize microbial pathogens and their products has been a key advance in our understanding of innate immunity. A tripartite sensing apparatus has developed to detect danger signals from infectious agents and damaged tissues, resulting in an immediate but short-lived defense response. This apparatus includes Toll-like receptors, retinoid acid-inducible gene-I-like receptors and other cytosolic nucleic acid sensors, and nucleotide-binding and oligomerization domain-like receptors; adaptors, kinases and other signaling molecules are required to elicit effective responses. Although this sensing is beneficial to the host, excessive activation and/or engagement by self molecules might induce autoimmune and other inflammatory disorders.
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2353
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Endosomal TLR signaling is required for anti-nucleic acid and rheumatoid factor autoantibodies in lupus. Proc Natl Acad Sci U S A 2009; 106:12061-6. [PMID: 19574451 DOI: 10.1073/pnas.0905441106] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Using the Unc93b1 3d mutation that selectively abolishes nucleic acid-binding Toll-like receptor (TLR) (TLR3, -7, -9) signaling, we show these endosomal TLRs are required for optimal production of IgG autoAbs, IgM rheumatoid factor, and other clinical parameters of disease in 2 lupus strains, B6-Fas(lpr) and BXSB. Strikingly, treatment with lipid A, an autoAb-inducing TLR4 agonist, could not overcome this requirement. The 3d mutation slightly reduced complete Freund's adjuvant (CFA)-mediated antigen presentation, but did not affect T-independent type 1 or alum-mediated T-dependent humoral responses or TLR-independent IFN production induced by cytoplasmic nucleic acids. These findings suggest that nucleic acid-sensing TLRs might act as an Achilles' heel in susceptible individuals by providing a critical pathway by which relative tolerance for nucleic acid-containing antigens is breached and systemic autoimmunity ensues. Importantly, this helps provide an explanation for the high frequency of anti-nucleic acid Abs in lupus-like systemic autoimmunity.
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2354
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Scott I. Mitochondrial factors in the regulation of innate immunity. Microbes Infect 2009; 11:729-36. [PMID: 19427399 PMCID: PMC2715439 DOI: 10.1016/j.micinf.2009.04.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Accepted: 04/24/2009] [Indexed: 01/19/2023]
Abstract
Viral infection stimulates multiple signalling pathways in the innate immune system, leading to type 1 interferon production. Recent research has identified the mitochondrial protein MAVS as a key component of one intracellular pathway, definitively linking mitochondria to the mammalian antiviral defence system for the first time.
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Affiliation(s)
- Iain Scott
- Molecular Biology Section, Translational Medicine Branch, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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2355
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Okabe Y, Sano T, Nagata S. Regulation of the innate immune response by threonine-phosphatase of Eyes absent. Nature 2009; 460:520-4. [PMID: 19561593 DOI: 10.1038/nature08138] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 05/08/2009] [Indexed: 11/09/2022]
Abstract
Innate immunity is stimulated not only by viral or bacterial components, but also by non-microbial danger signals (damage-associated molecular patterns). One of the damage-associated molecular patterns is chromosomal DNA that escapes degradation. In programmed cell death and erythropoiesis, DNA from dead cells or nuclei expelled from erythroblasts is digested by DNase II in the macrophages after they are engulfed. DNase II(-/-) (also known as Dnase2a(-/-)) mice suffer from severe anaemia or chronic arthritis due to interferon-beta (IFN-beta) and tumour necrosis factor-alpha (TNF-alpha) produced from the macrophages carrying undigested DNA in a Toll-like receptor (TLR)-independent mechanism. Here we show that Eyes absent 4 (EYA4), originally identified as a co-transcription factor, stimulates the expression of IFN-beta and CXCL10 in response to the undigested DNA of apoptotic cells. EYA4 enhanced the innate immune response against viruses (Newcastle disease virus and vesicular stomatitis virus), and could associate with signalling molecules (IPS-1 (also known as MAVS), STING (TMEM173) and NLRX1). Three groups have previously shown that EYA has phosphatase activity. We found that mouse EYA family members act as a phosphatase for both phosphotyrosine and phosphothreonine. The haloacid dehalogenase domain at the carboxy terminus contained the tyrosine-phosphatase, and the amino-terminal half carried the threonine-phosphatase. Mutations of the threonine-phosphatase, but not the tyrosine-phosphatase, abolished the ability of EYA4 to enhance the innate immune response, suggesting that EYA regulates the innate immune response by modulating the phosphorylation state of signal transducers for the intracellular pathogens.
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Affiliation(s)
- Yasutaka Okabe
- Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Kyoto 606-8501, Japan
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2356
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Nakhaei P, Genin P, Civas A, Hiscott J. RIG-I-like receptors: sensing and responding to RNA virus infection. Semin Immunol 2009; 21:215-22. [PMID: 19539500 DOI: 10.1016/j.smim.2009.05.001] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Accepted: 05/06/2009] [Indexed: 02/08/2023]
Abstract
Viral and microbial pathogens contain specific motifs or pathogen-associated molecular patterns (PAMPs) that are recognized by cell surface- and endosome-associated Toll-like receptors (TLRs). RNA virus infection is also detected through TLR-independent mechanisms. Early viral replicative intermediates are detected by two recently characterized cystolic viral RNA receptors-RIG-I and MDA-5. Both are DExDH/box RNA helicases, and RIG-I specifically recognizes 5'-triphosphate containing viral RNA and transmits signals that induce type I interferon-mediated host immunity against virus infection. In this review, we will focus on RIG-I-like receptor (RLR) signal transduction and the regulatory mechanisms - ubiquitination, deubiquitination, ISGylation - underlying this important host response.
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Affiliation(s)
- Peyman Nakhaei
- The Terry Fox Molecular Oncology Group, Lady Davis Institute for Medical Research, Quebec, Canada
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2357
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The role of mitochondria in cellular defense against microbial infection. Semin Immunol 2009; 21:223-32. [PMID: 19535268 DOI: 10.1016/j.smim.2009.05.009] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Accepted: 05/07/2009] [Indexed: 12/31/2022]
Abstract
Mitochondria have been long recognized for their key role in the modulation of cell death pathways. Thus, it is therefore not surprising that this organelle represents a recurrent target for pathogenic microbes, aiming to manipulate the fate of the infected host cell. More recently, mitochondria have been shown to serve as a crucial platform for innate immune signaling, as illustrated by the identification of MAVS (also known as IPS-1, VISA and Cardif), NLRX1 and STING as mitochondrial proteins. This review discusses the tight interplay between microbial infection, innate immune signaling and mitochondria.
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2358
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Baculovirus induces type I interferon production through toll-like receptor-dependent and -independent pathways in a cell-type-specific manner. J Virol 2009; 83:7629-40. [PMID: 19474102 DOI: 10.1128/jvi.00679-09] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Autographa californica nuclear polyhedrosis virus (AcNPV) is a double-stranded-DNA virus that is pathogenic to insects. AcNPV was shown to induce an innate immune response in mammalian immune cells and to confer protection of mice from lethal viral infection. In this study, we have shown that production of type I interferon (IFN) by AcNPV in murine plasmacytoid dendritic cells (pDCs) and non-pDCs, such as peritoneal macrophages and splenic CD11c+ DCs, was mediated by Toll-like receptor (TLR)-dependent and -independent pathways, respectively. IFN regulatory factor 7 (IRF7) was shown to play a crucial role in the production of type I IFN by AcNPV not only in immune cells in vitro but also in vivo. In mouse embryonic fibroblasts (MEFs), AcNPV produced IFN-beta and IFN-inducible chemokines through TLR-independent and IRF3-dependent pathways, in contrast to the TLR-dependent and IRF3/IRF7-independent production of proinflammatory cytokines. Although production of IFN-beta and IFN-inducible chemokines was severely impaired in IFN promoter-stimulator 1 (IPS-1)-deficient MEFs upon infection with vesicular stomatitis virus, AcNPV produced substantial amounts of the cytokines in IPS-1-deficient MEFs. These results suggest that a novel signaling pathway(s) other than TLR- and IPS-1-dependent pathways participates in the production of type I IFN in response to AcNPV infection.
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2359
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ERIS, an endoplasmic reticulum IFN stimulator, activates innate immune signaling through dimerization. Proc Natl Acad Sci U S A 2009; 106:8653-8. [PMID: 19433799 DOI: 10.1073/pnas.0900850106] [Citation(s) in RCA: 638] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
We report here the identification and characterization of a protein, ERIS, an endoplasmic reticulum (ER) IFN stimulator, which is a strong type I IFN stimulator and plays a pivotal role in response to both non-self-cytosolic RNA and dsDNA. ERIS (also known as STING or MITA) resided exclusively on ER membrane. The ER retention/retrieval sequence RIR was found to be critical to retain the protein on ER membrane and to maintain its integrity. ERIS was dimerized on innate immune challenges. Coumermycin-induced ERIS dimerization led to strong and fast IFN induction, suggesting that dimerization of ERIS was critical for self-activation and subsequent downstream signaling.
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2360
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Trivedi S, Greidinger EL. Endosomal Toll-like receptors in autoimmunity: mechanisms for clinical diversity. ACTA ACUST UNITED AC 2009; 6:433-442. [PMID: 20161373 DOI: 10.2217/thy.09.2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The endosomal Toll-like receptors (TLR3, TLR7 and TLR9) have been implicated in the pathogenesis of autoimmune diseases. Their signaling pathways show remarkable similarities and yet the outcomes following activation of each of these TLRs lead to clinically distinct autoimmune disease phenotypes. This review discusses how differences may arise at a molecular and cellular level to account for this diversity of responses. Understanding the roles of individual TLR pathways and the relationships between them and non-TLR innate immune pathways in the pathogenesis of diseases such as systemic lupus erythematosis highlights potential treatment targets for this spectrum of autoimmune diseases.
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Affiliation(s)
- Sapna Trivedi
- Division of Nephrology & Hypertension, University of Miami Miller School of Medicine, FL, USA
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2361
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ISG56 is a negative-feedback regulator of virus-triggered signaling and cellular antiviral response. Proc Natl Acad Sci U S A 2009; 106:7945-50. [PMID: 19416887 DOI: 10.1073/pnas.0900818106] [Citation(s) in RCA: 157] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
IFN-stimulated gene 56 (ISG56) is one of the first identified proteins induced by viruses and type I IFNs. In this study, we identified ISG56 as a virus-induced protein associated with MITA, an adapter protein involved in virus-triggered induction of type I IFNs. Overexpression of ISG56 inhibited Sendai virus-triggered activation of IRF3, NF-kappaB, and the IFN-beta promoter, whereas knockdown of ISG56 had opposite effects. Consistently, overexpression of ISG56 reversed cytoplasmic poly(I:C)-induced inhibition of vesicular stomatitis virus (VSV) replication, whereas knockdown of ISG56 inhibited VSV replication. Competitive coimmunoprecipitation experiments indicated that ISG56 disrupted the interactions between MITA and VISA or TBK1, two components in the virus-triggered IFN signaling pathways. These results suggest that ISG56 is a mediator of negative-feedback regulation of virus-triggered induction of type I IFNs and cellular antiviral responses.
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2362
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Abstract
Immunity against microbial pathogens primarily depends on the recognition of pathogen components by innate receptors expressed on immune and non-immune cells. Innate receptors are evolutionarily conserved germ-line-encoded proteins and include TLRs (Toll-like receptors), RLRs [RIG-I (retinoic acid-inducible gene-I)-like receptors] and NLRs (Nod-like receptors). These receptors recognize pathogens or pathogen-derived products in different cellular compartments, such as the plasma membrane, the endosomes or the cytoplasm, and induce the expression of cytokines, chemokines and co-stimulatory molecules to eliminate pathogens and instruct pathogen-specific adaptive immune responses. In the present review, we will discuss the recent progress in the study of pathogen recognition by TLRs, RLRs and NLRs and their signalling pathways.
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Affiliation(s)
- Himanshu Kumar
- Laboratory of Host Defense, WPI Immunology Frontier Research Center, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan
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2363
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Ubiquitin-regulated recruitment of IkappaB kinase epsilon to the MAVS interferon signaling adapter. Mol Cell Biol 2009; 29:3401-12. [PMID: 19380491 DOI: 10.1128/mcb.00880-08] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Induction of the antiviral interferon response is initiated upon recognition of viral RNA structures by the RIG-I or Mda-5 DEX(D/H) helicases. A complex signaling cascade then converges at the mitochondrial adapter MAVS, culminating in the activation of the IRF and NF-kappaB transcription factors and the induction of interferon gene expression. We have previously shown that MAVS recruits IkappaB kinase epsilon (IKKepsilon) but not TBK-1 to the mitochondria following viral infection. Here we map the interaction of MAVS and IKKepsilon to the C-terminal region of MAVS and demonstrate that this interaction is ubiquitin dependent. MAVS is ubiquitinated following Sendai virus infection, and K63-linked ubiquitination of lysine 500 (K500) of MAVS mediates recruitment of IKKepsilon to the mitochondria. Real-time PCR analysis reveals that a K500R mutant of MAVS increases the mRNA level of several interferon-stimulated genes and correlates with increased NF-kappaB activation. Thus, recruitment of IKKepsilon to the mitochondria upon MAVS K500 ubiquitination plays a modulatory role in the cascade leading to NF-kappaB activation and expression of inflammatory and antiviral genes. These results provide further support for the differential role of IKKepsilon and TBK-1 in the RIG-I/Mda5 pathway.
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2364
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Kash JC. Applications of high-throughput genomics to antiviral research: evasion of antiviral responses and activation of inflammation during fulminant RNA virus infection. Antiviral Res 2009; 83:10-20. [PMID: 19375457 PMCID: PMC3457704 DOI: 10.1016/j.antiviral.2009.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 04/01/2009] [Accepted: 04/09/2009] [Indexed: 12/18/2022]
Abstract
Host responses can contribute to the severity of viral infection, through the failure of innate antiviral mechanisms to recognize and restrict the pathogen, the development of intense systemic inflammation leading to circulatory failure or through tissue injury resulting from overly exuberant cell-mediated immune responses. High-throughput genomics methods are now being used to identify the biochemical pathways underlying ineffective or damaging host responses in a number of acute and chronic viral infections. This article reviews recent gene expression studies of 1918 H1N1 influenza and Ebola hemorrhagic fever in cell culture and animal models, focusing on how genomics experiments can be used to increase our understanding of the mechanisms that permit those viruses to cause rapidly overwhelming infection. Particular attention is paid to how evasion of type I IFN responses in infected cells might contribute to over-activation of inflammatory responses. Reviewing recent research and describing how future studies might be tailored to understand the relationship between the infected cell and its environment, this article discusses how the rapidly growing field of high-throughput genomics can contribute to a more complete understanding of severe, acute viral infections and identify novel targets for therapeutic intervention.
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Affiliation(s)
- John C Kash
- Viral Pathogenesis and Evolution Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, MD 20892-3203, USA.
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2365
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Kawai T, Akira S. The roles of TLRs, RLRs and NLRs in pathogen recognition. Int Immunol 2009; 21:317-37. [PMID: 19246554 PMCID: PMC2721684 DOI: 10.1093/intimm/dxp017] [Citation(s) in RCA: 1135] [Impact Index Per Article: 75.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Accepted: 01/30/2009] [Indexed: 02/07/2023] Open
Abstract
The mammalian innate immune system detects the presence of microbial infection through germ line-encoded pattern recognition receptors (PRRs). Toll-like receptors, retinoic acid-inducible gene-I-like receptors and nucleotide-binding oligomerization domain-like receptors serve as PRRs that recognize different but overlapping microbial components. They are expressed in different cellular compartments such as the cell surface, endosome, lysosome or cytoplasm and activate specific signaling pathways that lead to expression of genes that tailor immune responses to particular microbes. This review summarizes recent insights into pathogen sensing by these PRRs and their signaling pathways.
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Affiliation(s)
- Taro Kawai
- Laboratory of Host Defense, World Premier International Research Center, Osaka University, Suita, Osaka , Japan
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2366
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Tang ED, Wang CY. MAVS self-association mediates antiviral innate immune signaling. J Virol 2009; 83:3420-8. [PMID: 19193783 PMCID: PMC2663242 DOI: 10.1128/jvi.02623-08] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Accepted: 01/28/2009] [Indexed: 01/12/2023] Open
Abstract
The innate immune system recognizes nucleic acids during viral infection and stimulates cellular antiviral responses. Intracellular detection of RNA virus infection is mediated by the RNA helicases RIG-I (retinoic acid inducible gene I) and MDA-5, which recognize viral RNA and signal through the adaptor molecule MAVS (mitochondrial antiviral signaling) to stimulate the phosphorylation and activation of the transcription factors IRF3 (interferon regulatory factor 3) and IRF7. Once activated, IRF3 and IRF7 turn on the expression of type I interferons, such as beta interferon. Interestingly, unlike other signaling molecules identified in this pathway, MAVS contains a C-terminal transmembrane (TM) domain that is essential for both type I interferon induction and localization of MAVS to the mitochondrial outer membrane. However, the role the MAVS TM domain plays in signaling remains unclear. Here we report the identification of a function for the TM domain in mediating MAVS self-association. The activation of RIG-I/MDA-5 leads to the TM-dependent dimerization of the MAVS N-terminal caspase recruitment domain, thereby providing an interface for direct binding to and activation of the downstream effector TRAF3 (tumor necrosis factor receptor-associated factor 3). Our results reveal a role for MAVS self-association in antiviral innate immunity signaling and provide a molecular mechanism for downstream signal transduction.
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Affiliation(s)
- Eric D Tang
- Laboratory of Molecular Signaling, Division of Oral Biology and Medicine, UCLA School of Dentistry, Los Angeles, California 90095, USA
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2367
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Suthar MS, Gale M, Owen DM. Evasion and disruption of innate immune signalling by hepatitis C and West Nile viruses. Cell Microbiol 2009; 11:880-8. [PMID: 19341437 DOI: 10.1111/j.1462-5822.2009.01311.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Signalling pathways leading to type I interferon production are the first line of defence employed by the host to combat viruses, and represent a barrier that an invading virus must overcome in order to establish infection. In this review we highlight the ability of two members of the Flaviviridae, a globally distributed family of RNA viruses that represent a significant public health concern, to disrupt and evade these defences. Hepatitis C virus is a hepatotropic virus, infecting greater than 170 million people worldwide, while West Nile virus is a neurotropic virus that causes encephalitis in humans and horses. While these viruses cause distinct disease phenotypes, the ability of pathogenic strains to modulate the innate immune response is a key factor in influencing disease outcome. Both viruses have evolved unique strategies to target various aspects of type I interferon induction and signalling in order to prevent viral clearance and to promote virus replication.
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Affiliation(s)
- Mehul S Suthar
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195, USA
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2368
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Abstract
Recent identification of key components in the pattern recognition receptor pathway of retinoic acid-inducible gene-1-like receptors, coupled with characterisation of a new cytoplasmic DNA-sensing molecule, have led to a greater understanding of the role viral nucleic acids play in activating innate immunity. This activation of type I interferon is essential for both limiting viral infection and stimulating activation of the adaptive immune response.
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Affiliation(s)
- Aaron Irving
- Monash Institute of Medical Research, Monash University, P.O. Box 5418, Clayton, Victoria 3168, Australia
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2369
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Zhong B, Zhang L, Lei C, Li Y, Mao AP, Yang Y, Wang YY, Zhang XL, Shu HB. The Ubiquitin Ligase RNF5 Regulates Antiviral Responses by Mediating Degradation of the Adaptor Protein MITA. Immunity 2009; 30:397-407. [DOI: 10.1016/j.immuni.2009.01.008] [Citation(s) in RCA: 279] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Revised: 12/28/2008] [Accepted: 01/20/2009] [Indexed: 02/06/2023]
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2370
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Aresté C, Blackbourn DJ. Modulation of the immune system by Kaposi's sarcoma-associated herpesvirus. Trends Microbiol 2009; 17:119-29. [PMID: 19230674 DOI: 10.1016/j.tim.2008.12.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 12/10/2008] [Accepted: 12/11/2008] [Indexed: 12/24/2022]
Abstract
The most recently identified human herpesvirus is Kaposi's sarcoma-associated herpesvirus (KSHV). It causes Kaposi's sarcoma, a tumour occurring most commonly in untreated AIDS patients and the leading cancer of men in certain parts of Africa. KSHV might also contribute to the pathogenesis of primary effusion lymphoma and multicentric Castleman's disease. The genome of KSHV contains 86 genes, almost a quarter of which encode proteins with either demonstrated or potential immunoregulatory activity. They include homologues of cellular proteins and unique KSHV proteins that can deregulate many aspects of the immune response, including T- and B-cell functions, complement activation, the innate antiviral interferon response and natural killer cell activity. The functions of these proteins and the ways in which they perturb the normal immune response are the subjects of the present review.
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Affiliation(s)
- Cristina Aresté
- Cancer Research UK Institute for Cancer Studies, University of Birmingham, Birmingham B15 2TT, UK
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2371
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Kemp C, Imler JL. Antiviral immunity in drosophila. Curr Opin Immunol 2009; 21:3-9. [PMID: 19223163 DOI: 10.1016/j.coi.2009.01.007] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 01/20/2009] [Indexed: 12/21/2022]
Abstract
Genetic analysis of the drosophila antiviral response indicates that RNA interference plays a major role. This contrasts with the situation in mammals, where interferon-induced responses mediate innate antiviral host-defense. An inducible response also contributes to antiviral immunity in drosophila, and similarities in the sensing and signaling of viral infection are becoming apparent between drosophila and mammals. In particular, DExD/H box helicases appear to play a crucial role in the cytosolic detection of viral RNAs in flies and mammals.
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Affiliation(s)
- Cordula Kemp
- CNRS-UPR, Institut de Biologie Moléculaire et Cellulaire, Strasbourg, France
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2372
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Yanai H, Savitsky D, Tamura T, Taniguchi T. Regulation of the cytosolic DNA-sensing system in innate immunity: a current view. Curr Opin Immunol 2009; 21:17-22. [DOI: 10.1016/j.coi.2009.01.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Revised: 01/15/2009] [Accepted: 01/20/2009] [Indexed: 11/24/2022]
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2373
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Bowzard JB, Ranjan P, Sambhara S, Fujita T. Antiviral defense: RIG-Ing the immune system to STING. Cytokine Growth Factor Rev 2009; 20:1-5. [PMID: 19211297 DOI: 10.1016/j.cytogfr.2009.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A critical component of the innate immune response is the presence of germ line-encoded receptors capable of recognizing a wide variety of pathogen-associated molecules. One group of these receptors, the cytoplasmic RIG-I-like helicases (RLH), is involved in the induction of Type I interferon in response to viral infection. Here we discuss results of recent investigations into the initiation and transmission of signals through the RIG-I pathway.
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2374
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Abstract
Viral infection is detected by cellular sensor molecules as foreign nucleic acids and initiates innate antiviral responses, including the activation of proinflammatory cytokines and type I interferon (IFN). Recent identification of cytoplasmic viral sensors, such as retinoic acid-inducible gene-I-like receptors (RLRs), highlights their significance in the induction of antiviral innate immunity. Moreover, it is intriguing to understand how they can discriminate endogenous RNA from foreign viral RNA and initiate signaling cascades leading to the induction of type I IFNs. This review focuses on the current understanding of the molecular machinery underlying RNA recognition and subsequent signal transduction by RLRs.
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Affiliation(s)
- Mitsutoshi Yoneyama
- Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan
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2375
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Abstract
The innate immune system is essential for the initial detection of invading viruses and subsequent activation of adaptive immunity. Three classes of receptors, designated retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), Toll-like receptors (TLRs), and nucleotide oligomerization domain (NOD)-like receptors (NLRs), sense viral components, such as double-stranded RNA (dsRNA), single-stranded RNA, and DNA. RLRs and TLRs play essential roles in the production of type I interferons (IFNs) and proinflammatory cytokines in cell type-specific manners. While the RLRs play essential roles in the recognition of RNA viruses in various cells, plasmacytoid dendritic cells utilize TLRs for detecting virus invasion. NLRs play a role in the production of mature interleukin-1 beta to dsRNA stimulation. Activation of innate immune cells is critical for mounting adaptive immune responses. In this review, we discuss recent advances in our understanding of the mechanisms of viral RNA recognition by these different types of receptors and its relation to acquired immune responses.
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Affiliation(s)
- Osamu Takeuchi
- Laboratory of Host Defense, WPI Immunology Frontier Research Center, Osaka University, Osaka, Japan
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2376
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Kawane K, Nagata S. Chronic polyarthritis caused by mammalian DNA that escapes from degradation in macrophages. Inflamm Regen 2009. [DOI: 10.2492/inflammregen.29.204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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2377
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Abstract
The expression of pattern-recognition receptors (PRRs) by immune and tissue cells provides the host with the ability to detect and respond to infection by viruses and other microorganisms. Significant progress has been made from studying this area, including the identification of PRRs, such as Toll-like receptors and RIG-I-like receptors, and the description of the molecular basis of their signalling pathways, which lead to the production of interferons and other cytokines. In parallel, common mechanisms used by viruses to evade PRR-mediated responses or to actively subvert these pathways for their own benefit are emerging. Accumulating evidence on how viral infection and PRR signalling pathways intersect is providing further insights into the function of the pathways involved, their constituent proteins and ways in which they could be manipulated therapeutically.
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Affiliation(s)
- Andrew G Bowie
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland.
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2378
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STING: adding to the antiviral arsenal. Nat Rev Immunol 2008. [DOI: 10.1038/nri2424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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