1351
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Clarke CJP, Hii LL, Bolden JE, Johnstone RW. Inducible activation of IFI 16 results in suppression of telomerase activity, growth suppression and induction of cellular senescence. J Cell Biochem 2010; 109:103-12. [PMID: 19885868 DOI: 10.1002/jcb.22386] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Expression of the human HIN-200 family member IFI 16 has been reported to suppress cell growth and contribute to the onset of cellular senescence. However the molecular events involved in this process have not been fully characterised. We fused IFI 16 to the estrogen receptor ligand-binding domain to establish an inducible model for studying the molecular events that cause these phenomena. In cells induced to express the ER-IFI 16 within the nucleus there was a decrease in cellular proliferation and concomitant growth arrest in the G1 phase of the cell cycle. Unlike previous reports, this did not appear to involve the p53-p21(WAF1/CIP1)-cdk2-pRb pathway. Following nuclear expression of ER-IFI 16 we noted senescence-like morphological changes and expression of senescence-associated beta-galactosidase in growth arrested cells. Importantly, we also found a marked reduction in telomerase activity in arrested cells compared to controls. Moreover, IFI 16 and hTERT co-localised within the nucleus and these two proteins physically interacted in vivo and in vitro. Together, these data suggest that IFI 16 may act as an endogenous regulator of telomerase activity and, through its interaction with hTERT, contributes to the inhibition of proliferation and induces a senescence-like state.
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Affiliation(s)
- Christopher J P Clarke
- Cancer Immunology Program, Peter MacCallum Cancer Centre, East Melbourne, Victoria 3002, Australia
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1352
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Netea MG, Simon A, van de Veerdonk F, Kullberg BJ, Van der Meer JWM, Joosten LAB. IL-1beta processing in host defense: beyond the inflammasomes. PLoS Pathog 2010; 6:e1000661. [PMID: 20195505 PMCID: PMC2829053 DOI: 10.1371/journal.ppat.1000661] [Citation(s) in RCA: 395] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Stimulation and release of proinflammatory cytokines is an essential step for the activation of an effective innate host defense, and subsequently for the modulation of adaptive immune responses. Interleukin-1β (IL-1β) and IL-18 are important proinflammatory cytokines that on the one hand activate monocytes, macropages, and neutrophils, and on the other hand induce Th1 and Th17 adaptive cellular responses. They are secreted as inactive precursors, and the processing of pro-IL-1β and pro-IL-18 depends on cleavage by proteases. One of the most important of these enzymes is caspase-1, which in turn is activated by several protein platforms called the inflammasomes. Inflammasome activation differs in various cell types, and knock-out mice defective in either caspase-1 or inflammasome components have an increased susceptibility to several types of infections. However, in other infections and in models of sterile inflammation, caspase-1 seems to be less important, and alternative mechanisms such as neutrophil-derived serine proteases or proteases released from microbial pathogens can process and activate IL-1β. In conclusion, IL-1β/IL-18 processing during infection is a complex process in which the inflammasomes are only one of several activation mechanisms.
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Affiliation(s)
- Mihai G Netea
- Department of Medicine, Radboud University Nijmegen Medical Center, and Nijmegen Center for Infections, Inflammation and Immunity (N4i), Nijmegen, The Netherlands.
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1353
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Opitz B, van Laak V, Eitel J, Suttorp N. Innate immune recognition in infectious and noninfectious diseases of the lung. Am J Respir Crit Care Med 2010; 181:1294-309. [PMID: 20167850 DOI: 10.1164/rccm.200909-1427so] [Citation(s) in RCA: 194] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Diseases of the respiratory tract are among the leading causes of death in the world population. Increasing evidence points to a key role of the innate immune system with its pattern recognition receptors (PRRs) in both infectious and noninfectious lung diseases, which include pneumonia, chronic obstructive pulmonary disease, acute lung injury, pneumoconioses, and asthma. PRRs are capable of sensing different microbes as well as endogenous molecules that are released after cell damage. This PRR engagement is the prerequisite for the initiation of immune responses to infections and tissue injuries which can be beneficial or detrimental to the host. PRRs include the Toll-like receptors, NOD-like receptors, RIG-I-like receptors, and cytosolic DNA sensors. The PRRs and their signaling pathways represent promising targets for prophylactic and therapeutic interventions in various lung diseases.
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Affiliation(s)
- Bastian Opitz
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin, Germany.
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1354
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Kim YI, Park JE, Brand DD, Fitzpatrick EA, Yi AK. Protein kinase D1 is essential for the proinflammatory response induced by hypersensitivity pneumonitis-causing thermophilic actinomycetes Saccharopolyspora rectivirgula. THE JOURNAL OF IMMUNOLOGY 2010; 184:3145-56. [PMID: 20142359 DOI: 10.4049/jimmunol.0903718] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Hypersensitivity pneumonitis is an interstitial lung disease that results from repeated pulmonary exposure to various organic Ags, including Saccharopolyspora rectivirgula, the causative agent of farmer's lung disease. Although the contributions of proinflammatory mediators to the disease pathogenesis are relatively well documented, the mechanism(s) involved in the initiation of proinflammatory responses against the causative microorganisms and the contribution of signaling molecules involved in the host immune defense have not been fully elucidated. In the current study, we found that S. rectivirgula induces the activation of protein kinase D (PKD)1 in lung cells in vitro and in vivo. Activation of PKD1 by S. rectivirgula was dependent on MyD88. Inhibition of PKD by pharmacological PKD inhibitor Gö6976 and silencing of PKD1 expression by small interfering RNA revealed that PKD1 is indispensable for S. rectivirgula-mediated activation of MAPKs and NF-kappaB and the expression of various proinflammatory cytokines and chemokines. In addition, compared with controls, mice pretreated with Gö6976 showed significantly suppressed alveolitis and neutrophil influx in bronchial alveolar lavage fluid and interstitial lung tissue, as well as substantially decreased myeloperoxidase activity in the lung after pulmonary exposure to S. rectivirgula. These results demonstrate that PKD1 is essential for S. rectivirgula-mediated proinflammatory immune responses and neutrophil influx in the lung. Our findings also imply the possibility that PKD1 is one of the critical factors that play a regulatory role in the development of hypersensitivity pneumonitis caused by microbial Ags and that inhibition of PKD1 activation could be an effective way to control microbial Ag-induced hypersensitivity pneumonitis.
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Affiliation(s)
- Young-In Kim
- Children's Foundation Research Center at Le Bonheur Children's Medical Center, Department of Pediatrics, University of Tennessee Health Science Center, Memphis, TN 38103, USA
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1355
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Amer AO. Modulation of caspases and their non-apoptotic functions byLegionella pneumophila. Cell Microbiol 2010; 12:140-7. [DOI: 10.1111/j.1462-5822.2009.01401.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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1356
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1357
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1358
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Gabhann JN, Higgs R, Brennan K, Thomas W, Damen JE, Ben Larbi N, Krystal G, Jefferies CA. Absence of SHIP-1 results in constitutive phosphorylation of tank-binding kinase 1 and enhanced TLR3-dependent IFN-beta production. THE JOURNAL OF IMMUNOLOGY 2010; 184:2314-20. [PMID: 20100929 DOI: 10.4049/jimmunol.0902589] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis, result from a loss of tolerance to self-antigens and immune-mediated injury precipitated by the overproduction of type I IFN and inflammatory cytokines. We have identified the inositol 5' phosphatase SHIP-1 as a negative regulator of TLR3-induced type I IFN production. SHIP-1-deficient macrophages display enhanced TLR-induced IFN-beta production, and overexpression of SHIP-1 negatively regulates the ability of TLR3 and its adaptor, Toll/IL-1 receptor domain-containing adaptor-inducing IFN-beta, to induce IFN-beta promoter activity, indicating that SHIP-1 negatively regulates TLR-induced IFN-beta production. Further dissection of the IFN-beta pathway implicates TANK-binding kinase 1 (TBK1) as the target for SHIP-1. Critically, in the absence of SHIP-1, TBK1 appears to be hyperphosphorylated both in unstimulated cells and following TLR3 stimulation. In addition, TBK1 appears to be constitutively associated with Toll/IL-1 receptor domain-containing adaptor-inducing IFN-beta and TNFR-associated factor 3 in SHIP-1 deficient cells, whereas in wild-type cells this association is inducible following TLR3 stimulation. In support of a role for SHIP-1 in regulating complex formation, confocal microscopy demonstrates that TBK1 distribution in the cell is significantly altered in SHIP-1-deficient cells, with more prominent endosomal staining observed, compared with wild-type controls. Taken together, our results point to SHIP-1 as a critical negative regulator of IFN-beta production downstream of TLR3 through the regulation of TBK1 localization and activity.
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Affiliation(s)
- Joan Ní Gabhann
- Molecular and Cellular Therapeutics, Royal College of Surgeons, Ireland Research Institute, Dublin 2, Ireland
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1359
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Juliana C, Fernandes-Alnemri T, Wu J, Datta P, Solorzano L, Yu JW, Meng R, Quong AA, Latz E, Scott CP, Alnemri ES. Anti-inflammatory compounds parthenolide and Bay 11-7082 are direct inhibitors of the inflammasome. J Biol Chem 2010; 285:9792-9802. [PMID: 20093358 DOI: 10.1074/jbc.m109.082305] [Citation(s) in RCA: 472] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Activation of the inflammasome generates the pro-inflammatory cytokines interleukin-1 beta and -18, which are important mediators of inflammation. Abnormal activation of the inflammasome leads to many inflammatory diseases, including gout, silicosis, neurodegeneration, and genetically inherited periodic fever syndromes. Therefore, identification of small molecule inhibitors that target the inflammasome is an important step toward developing effective therapeutics for the treatment of inflammation. Here, we show that the herbal NF-kappaB inhibitory compound parthenolide inhibits the activity of multiple inflammasomes in macrophages by directly inhibiting the protease activity of caspase-1. Additional investigations of other NF-kappaB inhibitors revealed that the synthetic I kappaB kinase-beta inhibitor Bay 11-7082 and structurally related vinyl sulfone compounds selectively inhibit NLRP3 inflammasome activity in macrophages independent of their inhibitory effect on NF-kappaB activity. In vitro assays of the effect of parthenolide and Bay 11-7082 on the ATPase activity of NLRP3 demonstrated that both compounds inhibit the ATPase activity of NLRP3, suggesting that the inhibitory effect of these compounds on inflammasome activity could be mediated in part through their effect on the ATPase activity of NLRP3. Our results thus elucidate the molecular mechanism for the therapeutic anti-inflammatory activity of parthenolide and identify vinyl sulfones as a new class of potential therapeutics that target the NLRP3 inflammasome.
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Affiliation(s)
- Christine Juliana
- Departments of Biochemistry and Molecular Biology, Philadelphia, Pennsylvania 19107
| | | | - Jianghong Wu
- Departments of Biochemistry and Molecular Biology, Philadelphia, Pennsylvania 19107
| | - Pinaki Datta
- Departments of Biochemistry and Molecular Biology, Philadelphia, Pennsylvania 19107
| | - Leobaldo Solorzano
- Departments of Biochemistry and Molecular Biology, Philadelphia, Pennsylvania 19107
| | - Je-Wook Yu
- Departments of Biochemistry and Molecular Biology, Philadelphia, Pennsylvania 19107
| | - Rong Meng
- Cancer Biology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Andrew A Quong
- Cancer Biology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Eicke Latz
- Department of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts 01605; Institute of Innate Immunity, University of Bonn, D53012 Bonn, Germany
| | - Charles P Scott
- Departments of Biochemistry and Molecular Biology, Philadelphia, Pennsylvania 19107
| | - Emad S Alnemri
- Departments of Biochemistry and Molecular Biology, Philadelphia, Pennsylvania 19107.
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1360
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Nickerson KM, Christensen SR, Shupe J, Kashgarian M, Kim D, Elkon K, Shlomchik MJ. TLR9 regulates TLR7- and MyD88-dependent autoantibody production and disease in a murine model of lupus. THE JOURNAL OF IMMUNOLOGY 2010; 184:1840-8. [PMID: 20089701 DOI: 10.4049/jimmunol.0902592] [Citation(s) in RCA: 250] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Systemic lupus erythematosus is characterized by the production of autoantibodies against nucleic acid-associated Ags. We previously found that Tlr7 was required for anti-Sm and Tlr9 for anti-chromatin autoantibodies. Yet, although Tlr7 deficiency ameliorated disease, Tlr9 deficiency exacerbated it. Despite the mechanistic and clinical implications of this finding, it has yet to be elucidated. In this study, we characterize MRL/lpr lupus-prone mice genetically deficient in Tlr7, Tlr9, both Tlr7 and Tlr9, or Myd88 to test whether Tlr7 and Tlr9 function independently or instead regulate each other. We find that disease that is regulated by Tlr9 (and hence is worse in its absence) depends on Tlr7 for its manifestation. In addition, although Tlr7 and Tlr9 act in parallel pathways on different subsets of autoantibodies, Tlr9 also suppresses the production of Tlr7-dependent RNA-associated autoantibodies, suggesting previously unrecognized cross-regulation of autoantibody production as well. By comparing disease in mice deficient for Tlr7 and/or Tlr9 to those lacking Myd88, we also identify aspects of disease that have Tlr- and Myd88-independent components. These results suggest new models for how Tlr9 regulates and Tlr7 enhances disease and provide insight into aspects of autoimmune disease that are, and are not, influenced by TLR signals.
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Affiliation(s)
- Kevin M Nickerson
- Department of Laboratory Medicine, Yale University, New Haven, CT 06519, USA
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1361
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Shayakhmetov DM. Virus infection recognition and early innate responses to non-enveloped viral vectors. Viruses 2010; 2:244-261. [PMID: 21994609 PMCID: PMC3185565 DOI: 10.3390/v2010244] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Revised: 01/13/2010] [Accepted: 01/14/2010] [Indexed: 12/25/2022] Open
Abstract
Numerous human genetic and acquired diseases could be corrected or ameliorated if viruses are harnessed to safely and effectively deliver therapeutic genes to diseased cells and tissues in vivo. Innate immune and inflammatory response represents one of the key stumbling blocks during the development of viral-based therapies. In this review, current data on the early innate immune responses to viruses and to the most commonly used gene therapy vectors (using adenovirus and adeno-associated virus) will be discussed. Recent findings in the field may help develop new approaches to moderate these innate immune anti-viral responses and thus improve the safety of viral vectors for human gene therapy applications.
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Affiliation(s)
- Dmitry M Shayakhmetov
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA 98195-7720, USA
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1362
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Wilkins C, Gale M. Recognition of viruses by cytoplasmic sensors. Curr Opin Immunol 2010; 22:41-7. [PMID: 20061127 DOI: 10.1016/j.coi.2009.12.003] [Citation(s) in RCA: 324] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Accepted: 12/13/2009] [Indexed: 12/24/2022]
Abstract
The immune response to virus infection is initiated when pathogen recognition receptors (PRRs) of the host cell recognize specific nonself-motifs within viral products (known as a pathogen-associated molecular pattern or PAMP) to trigger intracellular signaling events that induce innate immunity, the front line of defense against microbial infection. The replication program of all viruses includes a cytosolic phase of genome amplification and/or mRNA metabolism and viral protein expression. Cytosolic recognition of viral infection by specific PRRs takes advantage of the dependence of viruses on the cytosolic component of their replication programs. Such PRR-PAMP interactions lead to PRR-dependent nonself-recognition and the downstream induction of type I interferons and proinflammatory cytokines. These factors serve to induce innate immune programs and drive the maturation of adaptive immunity and inflammation for the control of infection. Recent studies have focused on identifying the particular viral ligands recognized as nonself by cytosolic PRRs, and on defining the nature of the PRRs and their signaling pathways involved in immunity. The RIG-I-like receptors, RIG-I and MDA5, have been defined as essential PRRs for host detection of a variety of RNA viruses. Novel PRRs and their signaling pathways involved in detecting DNA viruses through nonself-recognition of viral DNA are also being elucidated. Moreover, studies to identify the PRRs and signaling factors of the host cell that mediate inflammatory signaling through inflammasome activation following virus infection are currently underway and have already revealed specific NOD-like receptors (NLRs) as inflammatory triggers. This review summarizes recent progress and current areas of focus in pathogen recognition and immune triggering by cytosolic PRRs.
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Affiliation(s)
- Courtney Wilkins
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195, USA
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1363
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APOBEC3 proteins mediate the clearance of foreign DNA from human cells. Nat Struct Mol Biol 2010; 17:222-9. [PMID: 20062055 PMCID: PMC2921484 DOI: 10.1038/nsmb.1744] [Citation(s) in RCA: 263] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2009] [Accepted: 11/09/2009] [Indexed: 12/11/2022]
Abstract
Bacteria evolved restriction endonucleases to prevent interspecies DNA transmission and bacteriophage infection. Here, we show that human cells possess an analogous mechanism. APOBEC3A is induced by interferon following DNA detection, and it deaminates foreign double-stranded DNA cytidines to uridines. These atypical DNA nucleosides are converted by the uracil DNA glycosylase UNG2 to abasic lesions, which lead to foreign DNA degradation. This mechanism is evident in cell lines and primary monocytes, where up to 97% of cytidines in foreign DNA are deaminated. In contrast, cellular genomic DNA appears unaffected. Several other APOBEC3s also restrict foreign gene transfer. Related proteins exist in all vertebrates, indicating that foreign DNA restriction may be a conserved innate immune defense mechanism. The efficiency and fidelity of genetic engineering, gene therapy, and DNA vaccination are likely to be influenced by this anti-DNA defense system.
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1364
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Witkin SS, Bierhals K, Linhares I, Normand N, Dieterle S, Neuer A. Genetic polymorphism in an inflammasome component, cervical mycoplasma detection and female infertility in women undergoing in vitro fertilization. J Reprod Immunol 2010; 84:171-5. [PMID: 20060594 DOI: 10.1016/j.jri.2009.11.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Revised: 10/29/2009] [Accepted: 11/23/2009] [Indexed: 01/11/2023]
Abstract
The inflammasome is an inducible cytoplasmic structure that is responsible for production and release of biologically active interleukin-1 (IL-1). A polymorphism in the inflammasome component NALP3 has been associated with decreased IL-1 levels and increased occurrence of vaginal Candida infection. We hypothesized that this polymorphism-induced variation would influence susceptibility to infertility. DNA was obtained from 243 women who were undergoing in vitro fertilization (IVF) and tested for a length polymorphism in intron 2 of the gene coding for NALP3 (gene symbol CIAS1). At the conclusion of testing the findings were analyzed in relation to clinical parameters and IVF outcome. The frequency of the 12unit repeat allele, associated with maximal inflammasome activity, was 62.3% in cases of female infertility vs. 75.6% in cases where only the male partner had a detectable fertility problem (p=0.0095). Conversely, the frequency of the 7unit repeat allele was 28.9% in those with a female fertility problem, 17.0% in women with infertile males and 18.4% in idiopathic infertility (p=0.0124). Among the women who were cervical culture-positive for mycoplasma the frequency of the 7unit repeat was 53.7% as opposed to 19.5% in those negative for this infection (p<0.0001). We conclude that the CIAS1 7unit repeat polymorphism increases the likelihood of mycoplasma infection-associated female infertility.
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Affiliation(s)
- Steven S Witkin
- Division of Immunology and Infectious Diseases, Department of Obstetrics and Gynecology, Weill Medical College of Cornell University, New York, NY 10065, USA.
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1365
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The IKK Kinases: Operators of Antiviral Signaling. Viruses 2010; 2:55-72. [PMID: 21994600 PMCID: PMC3185564 DOI: 10.3390/v2010055] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 12/30/2009] [Accepted: 01/06/2010] [Indexed: 12/24/2022] Open
Abstract
The ability of a cell to combat an intracellular pathogen requires a mechanism to recognize the threat and elicit a transcriptional response against it. In the context of virus infection, the cell must take measures to inhibit viral replication, meanwhile, convey warning signals to neighboring cells of the imminent threat. This immune response is predominantly mediated by the production of cytokines, notably, interferon beta (IFNβ). IFNβ signaling results in the transcriptional induction of over one hundred antiviral gene products whose timely expression renders infected cells more capable of inhibiting virus replication, while providing the uninfected cells with the reinforcements to generate a less permissive cellular environment. Induction of IFNβ and many aspects of the antiviral response pivot on the function of the IKK and IKK-related kinases. Despite sharing high levels of homology and some degree of functional redundancy, the classic IKK kinases: IKKα and IKKβ, and the IKK-related kinases: TBK1 and IKKɛ, perform distinct roles in regulating the host antiviral defense. These kinases serve as molecular operators in their cooperative ability to integrate incoming cellular cues and act on a range of essential antiviral transcription factors to reshape the cellular transcriptome during infection.
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1366
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Latz E. The inflammasomes: mechanisms of activation and function. Curr Opin Immunol 2010; 22:28-33. [PMID: 20060699 DOI: 10.1016/j.coi.2009.12.004] [Citation(s) in RCA: 344] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 12/16/2009] [Accepted: 12/16/2009] [Indexed: 01/20/2023]
Abstract
In response to injurious or infectious agents caspase-1 activating multiprotein complexes, termed inflammasomes, assemble in the cytoplasm of cells. Activated caspase-1 cleaves the proforms of the interleukin-1 cytokine family members leading to their activation and secretion. The IL-1 family cytokines have multiple proinflammatory activities implicating them in the pathogenesis of many inflammatory diseases. While defined ligands have been identified for the NLRP1, IPAF, and AIM2 inflammasomes, little is known about the activation mechanisms of the NLRP3 inflammasome. Numerous different molecular entities, such as various crystals, pore-forming toxins, or extracellular ATP can trigger the NLRP3 inflammasome. Recent work proposes that NLRP3 is activated indirectly by host factors that are generated in response to NLRP3 triggers.
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Affiliation(s)
- Eicke Latz
- University of Massachusetts Medical School, Department of Infectious Diseases and Immunology, 364 Plantation St, Worcester, MA 01605, USA.
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1367
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Immune Recognition of Nucleic Acids and Their Metabolites. NUCLEIC ACIDS AND MOLECULAR BIOLOGY 2010. [DOI: 10.1007/978-3-642-12617-8_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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1368
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Immunogenicity of Whole-Parasite Vaccines against Plasmodium falciparum Involves Malarial Hemozoin and Host TLR9. Cell Host Microbe 2010; 7:50-61. [DOI: 10.1016/j.chom.2009.12.003] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 10/20/2009] [Accepted: 12/07/2009] [Indexed: 11/22/2022]
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1369
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Yoneyama M, Fujita T. Recognition of viral nucleic acids in innate immunity. Rev Med Virol 2009; 20:4-22. [DOI: 10.1002/rmv.633] [Citation(s) in RCA: 233] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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1370
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Chen G, Pedra JHF. The inflammasome in host defense. SENSORS 2009; 10:97-111. [PMID: 22315529 PMCID: PMC3270830 DOI: 10.3390/s100100097] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 12/17/2009] [Accepted: 12/18/2009] [Indexed: 02/02/2023]
Abstract
Nod-like receptors have emerged as an important family of sensors in host defense. These receptors are expressed in macrophages, dendritic cells and monocytes and play an important role in microbial immunity. Some Nod-like receptors form the inflammasome, a protein complex that activates caspase-1 in response to several stimuli. Caspase-1 activation leads to processing and secretion of pro-inflammatory cytokines such as interleukin (IL)-1β and IL-18. Here, we discuss recent advances in the inflammasome field with an emphasis on host defense. We also compare differential requirements for inflammasome activation in dendritic cells, macrophages and monocytes.
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Affiliation(s)
- Gang Chen
- Center for Disease Vector Research and Department of Entomology, University of California-Riverside, Riverside, CA 92521, USA.
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1371
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Affiliation(s)
- Mohamed Lamkanfi
- Department of Physiological Chemistry, Genentech, South San Francisco, California, United States of America
- VIB Department of Medical Protein Research, and Department of Biochemistry, Ghent University, Ghent, Belgium
| | - Vishva M. Dixit
- Department of Physiological Chemistry, Genentech, South San Francisco, California, United States of America
- * E-mail:
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1372
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Meixenberger K, Pache F, Eitel J, Schmeck B, Hippenstiel S, Slevogt H, N'Guessan P, Witzenrath M, Netea MG, Chakraborty T, Suttorp N, Opitz B. Listeria monocytogenes-infected human peripheral blood mononuclear cells produce IL-1beta, depending on listeriolysin O and NLRP3. THE JOURNAL OF IMMUNOLOGY 2009; 184:922-30. [PMID: 20008285 DOI: 10.4049/jimmunol.0901346] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Different NOD-like receptors, including NLRP1, NLRP3, and NLRC4, as well as the recently identified HIN-200 protein, AIM2, form multiprotein complexes called inflammasomes, which mediate caspase-1-dependent processing of pro-IL-1beta. Listeria monocytogenes is an intracellular pathogen that is actively phagocytosed by monocytes/macrophages and subsequently escapes from the phagosome into the host cell cytosol, depending on its pore-forming toxin listeriolysin O (LLO). In this study, we demonstrate that human PBMCs produced mature IL-1beta when infected with wild-type L. monocytogenes or when treated with purified LLO. L. monocytogenes mutants lacking LLO or expressing a noncytolytic LLO as well as the avirulent Listeria innocua induced strongly impaired IL-1beta production. RNA interference and inhibitor experiments in human PBMCs as well as experiments in Nlrp3 and Rip2 knockout bone marrow-derived macrophages demonstrated that the Listeria-induced IL-1beta release was dependent on ASC, caspase-1, and NLRP3, whereas NOD2, Rip2, NLRP1, NLRP6, NLRP12, NLRC4, and AIM2 appeared to be dispensable. We found that L. monocytogenes-induced IL-1beta production was largely dependent on phagosomal acidification and cathepsin B release, whereas purified LLO activated an IL-1beta production independently of these mechanisms. Our results indicate that L. monocytogenes-infected human PBMCs produced IL-1beta, largely depending on an LLO-mediated phagosomal rupture and cathepsin B release, which is sensed by Nlrp3. In addition, an LLO-dependent but cathepsin B-independent NLRP3 activation might contribute to some extent to the IL-1beta production in L. monocytogenes-infected cells.
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Affiliation(s)
- Karolin Meixenberger
- Department of Internal Medicine/Infectious Diseases and Pulmonary Medicine, Charité Universitätsmedizin Berlin, Berlin, Germany
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1373
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Crow YJ, Rehwinkel J. Aicardi-Goutieres syndrome and related phenotypes: linking nucleic acid metabolism with autoimmunity. Hum Mol Genet 2009; 18:R130-6. [PMID: 19808788 DOI: 10.1093/hmg/ddp293] [Citation(s) in RCA: 237] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Aicardi-Goutières syndrome (AGS) is a genetically determined encephalopathy demonstrating phenotypic overlap both with the sequelae of congenital infection and with systemic lupus erythematosus (SLE). Recent molecular advances have revealed that AGS can be caused by mutations in any one of five genes, most commonly on a recessive basis but occasionally as a dominant trait. Like AGS, SLE is associated with a perturbation of type I interferon metabolism. Interestingly then, heterozygous mutations in the AGS1 gene TREX1 underlie a cutaneous subtype of SLE-called familial chilblain lupus, and mutations in TREX1 represent the single most common cause of monogenic SLE identified to date. Evidence is emerging to show that the nucleases defective in AGS are involved in removing endogenously produced nucleic acid (NA) species, and that a failure of this removal results in activation of the immune system. This hypothesis explains the phenotypic overlap of AGS with congenital infection and some aspects of SLE, where an equivalent type I interferon-mediated innate immune response is triggered by viral and self NAs, respectively. The combined efforts of clinicians, geneticists, immunologists and cell biologists are producing rapid progress in the understanding of AGS and overlapping autoimmune disorders. These studies provide important insights into the pathogenesis of SLE and beg urgent questions about the development and use of immunosuppressive therapies in AGS and related phenotypes.
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Affiliation(s)
- Yanick J Crow
- Academic Unit of Medical Genetics, Manchester Academic Health Science Centre, Central Manchester Foundation Trust, St Mary's Hospital, University of Manchester, Oxford Road, Manchester M13 9WL, UK.
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1374
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Keller M, Sollberger G, Beer HD. Thalidomide inhibits activation of caspase-1. THE JOURNAL OF IMMUNOLOGY 2009; 183:5593-9. [PMID: 19843943 DOI: 10.4049/jimmunol.0900476] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Thalidomide is an efficient anti-inflammatory and anti-angiogenic drug, but its therapeutic use is problematic due to a strong teratogenic activity. Nevertheless, thalidomide was approved for the treatment of inflammatory skin diseases and certain types of cancer, and it is extensively tested for several other indications. Recently, we demonstrated that active caspase-1, whose activation is dependent on inflammasome complexes, is required for unconventional protein secretion of proinflammatory cytokines such as IL-1 and of the proangiogenic fibroblast growth factor 2. In this study, we show that pharmacological doses of thalidomide strongly reduced the secretion of both proteins. Thalidomide-treated cells also released less of other leaderless proteins, which require caspase-1 activity for their secretion. In line with these findings, the drug inhibited activation and activity of caspase-1 in cultured cells but not in vitro. The latter finding suggests that the pharmacological activity is exerted by a metabolite of the drug. The anti-inflammatory activity of thalidomide was also mediated via caspase-1 in mice. These findings represent a novel mechanism by which thalidomide exerts its pharmacological activity and suggest that inhibition of the activity of IL-1 might represent a novel strategy to substitute thalidomide.
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Affiliation(s)
- Martin Keller
- Institute of Cell Biology, Department of Biology, Swiss Federal Institute of Technology Zurich, Switzerland
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1375
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Auerbuch V, Golenbock DT, Isberg RR. Innate immune recognition of Yersinia pseudotuberculosis type III secretion. PLoS Pathog 2009; 5:e1000686. [PMID: 19997504 PMCID: PMC2779593 DOI: 10.1371/journal.ppat.1000686] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Accepted: 11/09/2009] [Indexed: 01/08/2023] Open
Abstract
Specialized protein translocation systems are used by many bacterial pathogens to deliver effector proteins into host cells that interfere with normal cellular functions. How the host immune system recognizes and responds to this intrusive event is not understood. To address these questions, we determined the mammalian cellular response to the virulence-associated type III secretion system (T3SS) of the human pathogen Yersinia pseudotuberculosis. We found that macrophages devoid of Toll-like receptor (TLR) signaling regulate expression of 266 genes following recognition of the Y. pseudotuberculosis T3SS. This analysis revealed two temporally distinct responses that could be separated into activation of NFkappaB- and type I IFN-regulated genes. Extracellular bacteria were capable of triggering these signaling events, as inhibition of bacterial uptake had no effect on the ensuing innate immune response. The cytosolic peptidoglycan sensors Nod1 and Nod2 and the inflammasome component caspase-1 were not involved in NFkappaB activation following recognition of the Y. pseudotuberculosis T3SS. However, caspase-1 was required for secretion of the inflammatory cytokine IL-1beta in response to T3SS-positive Y. pseudotuberculosis. In order to characterize the bacterial requirements for induction of this novel TLR-, Nod1/2-, and caspase-1-independent response, we used Y. pseudotuberculosis strains lacking specific components of the T3SS. Formation of a functional T3SS pore was required, as bacteria expressing a secretion needle, but lacking the pore-forming proteins YopB or YopD, did not trigger these signaling events. However, nonspecific membrane disruption could not recapitulate the NFkappaB signaling triggered by Y. pseudotuberculosis expressing a functional T3SS pore. Although host cell recognition of the T3SS did not require known translocated substrates, the ensuing response could be modulated by effectors such as YopJ and YopT, as YopT amplified the response, while YopJ dampened it. Collectively, these data suggest that combined recognition of the T3SS pore and YopBD-mediated delivery of immune activating ligands into the host cytosol informs the host cell of pathogenic challenge. This leads to a unique, multifactorial response distinct from the canonical immune response to a bacterium lacking a T3SS.
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Affiliation(s)
- Victoria Auerbuch
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail:
| | - Douglas T. Golenbock
- Department of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Ralph R. Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Tufts University School of Medicine, Boston, Massachusetts, United States of America
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1376
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Abstract
Inflammation is the coordinated immune response to harmful stimuli that appear during infections or after tissue damage. Cells of the innate immune system are the central players in mediating inflammatory tissue responses. These cells are equipped with an array of signaling receptors that detect foreign molecular substances or altered endogenous molecules that appear under situations of stress. This review provides an overview of recent progress in elucidating the molecular mechanisms that lead to inflammatory reactions. We discuss the current knowledge of the mechanisms leading to the activation of cytoplasmic, multimolecular protein complexes, termed "inflammasomes," which regulate the activity of caspase-1 and the maturation and release of IL-1beta.
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Affiliation(s)
- Andrea Stutz
- Department of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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1377
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[Inflammasomes in viral infection]. Uirusu 2009; 59:13-21. [PMID: 19927984 DOI: 10.2222/jsv.59.13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The NOD-like receptors (NLRs) are a family of intracellular sensors of microbial motifs and damage-associated signals that have emerged as being a crucial component of the innate immune responses and inflammation. The inflammasome is a multiprotein complex, which include NLRs, their adaptor proteins and pro-caspase-1, that stimulates caspase-1 activation to promote the processing and secretion of proinflammatory cytokines interleukin 1beta (IL-1beta), IL-18 and IL-33, as well as "pyroptosis", a form cell death induced by bacterial pathogens. Among the various inflammasomes, the NLRP3 inflammasome is triggered by diverse set of molecules and signals. Recent reports indicate that infection by certain viruses also results in inflammasome activation. Here, we review our current understanding of the mechanism by which various stimuli activate inflammasomes. Further, we discuss the role of inflammasomes in the induction of adaptive immunity against influenza virus infection.
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1378
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Innate and adaptive immune responses to herpes simplex virus. Viruses 2009; 1:979-1002. [PMID: 21994578 PMCID: PMC3185534 DOI: 10.3390/v1030979] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 11/13/2009] [Accepted: 11/16/2009] [Indexed: 12/19/2022] Open
Abstract
Immune responses against HSV-1 and HSV-2 are complex and involve a delicate interplay between innate signaling pathways and adaptive immune responses. The innate response to HSV involves the induction of type I IFN, whose role in protection against disease is well characterized in vitro and in vivo. Cell types such as NK cells and pDCs contribute to innate anti-HSV responses in vivo. Finally, the adaptive response includes both humoral and cellular components that play important roles in antiviral control and latency. This review summarizes the innate and adaptive effectors that contribute to susceptibility, immune control and pathogenesis of HSV, and highlights the delicate interplay between these two important arms of immunity.
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1379
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Recognition of RNA virus by RIG-I results in activation of CARD9 and inflammasome signaling for interleukin 1 beta production. Nat Immunol 2009; 11:63-9. [PMID: 19915568 DOI: 10.1038/ni.1824] [Citation(s) in RCA: 429] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Accepted: 10/15/2009] [Indexed: 12/18/2022]
Abstract
Interleukin 1 beta (IL-1 beta) is a potent proinflammatory factor during viral infection. Its production is tightly controlled by transcription of Il1b dependent on the transcription factor NF-kappaB and subsequent processing of pro-IL-1 beta by an inflammasome. However, the sensors and mechanisms that facilitate RNA virus-induced production of IL-1 beta are not well defined. Here we report a dual role for the RNA helicase RIG-I in RNA virus-induced proinflammatory responses. Whereas RIG-I-mediated activation of NF-kappaB required the signaling adaptor MAVS and a complex of the adaptors CARD9 and Bcl-10, RIG-I also bound to the adaptor ASC to trigger caspase-1-dependent inflammasome activation by a mechanism independent of MAVS, CARD9 and the Nod-like receptor protein NLRP3. Our results identify the CARD9-Bcl-10 module as an essential component of the RIG-I-dependent proinflammatory response and establish RIG-I as a sensor able to activate the inflammasome in response to certain RNA viruses.
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1380
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Extrachromosomal histone H2B mediates innate antiviral immune responses induced by intracellular double-stranded DNA. J Virol 2009; 84:822-32. [PMID: 19906922 DOI: 10.1128/jvi.01339-09] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Fragments of double-stranded DNA (dsDNA) forming a right-handed helical structure (B-DNA) stimulate cells to produce type I interferons (IFNs). While an adaptor molecule, IFN-beta promoter stimulator 1 (IPS-1), mediates dsDNA-induced cellular signaling in human cells, the underlying molecular mechanism is not fully understood. Here, we demonstrate that the extrachromosomal histone H2B mediates innate antiviral immune responses in human cells. H2B physically interacts with IPS-1 through the association with a newly identified adaptor, CIAO (COOH-terminal importin 9-related adaptor organizing histone H2B and IPS-1), to transmit the cellular signaling for dsDNA but not immunostimulatory RNA. Extrachromosomal histone H2B was biologically crucial for cell-autonomous responses to protect against multiplication of DNA viruses but not an RNA virus. Thus, the present findings provide evidence indicating that the extrachromosomal histone H2B is engaged in the signaling pathway initiated by dsDNA to trigger antiviral innate immune responses.
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1381
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Abdul-Sater AA, Saïd-Sadier N, Ojcius DM, Yilmaz Ö, Kelly KA. Inflammasomes bridge signaling between pathogen identification and the immune response. Drugs Today (Barc) 2009; 45 Suppl B:105-112. [PMID: 20011701 PMCID: PMC2829444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Microbial organisms express pathogen-associated molecular patterns (PAMPs) that can stimulate expression of proinflammatory mediators following ligation of pathogen recognition receptors. However, both commensal organisms and pathogens can express PAMPs. The immune system can distinguish between commensals and pathogens in part through secretion of the key inflammatory cytokines interleukin (IL)-1beta and IL-18. A PAMP such as lipopolysaccharide can induce production of intracellular pro-IL-1beta and pro-IL-18, but not their secretion. A second "danger signal", derived from host-cell molecules that are released from stressed or infected cells, or detected as a PAMP that is present in the cytosol, can stimulate assembly of an inflammasome that activates the protease caspase-1. Caspase-1, in turn, is responsible for processing and secretion of the mature IL-1beta and IL-18. Many diverse ligands leading to inflammasome activation have been identified, but the cell signaling pathways initiated by the ligands tend to converge on a small set of common mechanisms.
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Affiliation(s)
- Ali A. Abdul-Sater
- Health Sciences Research Institute and School of Natural Sciences, University of California, Merced, CA 95343, USA
| | - Najwane Saïd-Sadier
- Health Sciences Research Institute and School of Natural Sciences, University of California, Merced, CA 95343, USA
| | - David M. Ojcius
- Health Sciences Research Institute and School of Natural Sciences, University of California, Merced, CA 95343, USA
| | - Özlem Yilmaz
- Department of Periodontology and Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA
| | - Kathy A. Kelly
- Department of Pathology & Laboratory Medicine, Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
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1382
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McCormack WJ, Parker AE, O'Neill LA. Toll-like receptors and NOD-like receptors in rheumatic diseases. Arthritis Res Ther 2009; 11:243. [PMID: 19835640 PMCID: PMC2787278 DOI: 10.1186/ar2729] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The past 10 years have seen the description of families of receptors that drive proinflammatory cytokine production in infection and tissue injury. Two major classes have been examined in the context of inflammatory joint disease--the Toll-like receptors (TLRs) and NOD-like receptors (NLRs). TLRs such as TLR2 and TLR4 are being implicated in the pathology of rheumatoid arthritis, ankylosing spondylitis, lyme arthritis and osteoarthritis. Nalp3 has been identified as a key NLR for IL-1beta production and has been shown to have a particular role in gout. These findings present new therapeutic opportunities, possibly allowing for the replacement of biologics with small molecule inhibitors.
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Affiliation(s)
- William J McCormack
- OPSONA Therapeutics Ltd, Institute of Molecular Medicine, Trinity Centre for Health Sciences, St James' Hospital, Dublin 8, Ireland.
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1383
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Toll-like receptor 2 on inflammatory monocytes induces type I interferon in response to viral but not bacterial ligands. Nat Immunol 2009; 10:1200-7. [PMID: 19801985 PMCID: PMC2821672 DOI: 10.1038/ni.1792] [Citation(s) in RCA: 338] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Accepted: 08/18/2009] [Indexed: 11/30/2022]
Abstract
Despite the paradigm that the innate immune system uses nucleic acid-specific receptors to detect viruses due to a lack of other conserved features, a number of viruses are recognized by TLR2 and TLR4. The relevance of this recognition for antiviral immunity remains largely unexplained. Here we report that TLR2 activation by viruses leads to production of type I interferon (IFN). TLR2-dependent induction of type I IFN only occurs in response to viral ligands, indicating that TLR2 is capable of discriminating between pathogen classes. We demonstrate that this specialized response is mediated by Ly6Chigh inflammatory monocytes. Thus, the innate immune system can detect certain non-nucleic acid features of viruses and links this recognition to specific antiviral gene induction.
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1384
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Ablasser A, Bauernfeind F, Hartmann G, Latz E, Fitzgerald KA, Hornung V. RIG-I-dependent sensing of poly(dA:dT) through the induction of an RNA polymerase III-transcribed RNA intermediate. Nat Immunol 2009; 10:1065-72. [PMID: 19609254 PMCID: PMC3878616 DOI: 10.1038/ni.1779] [Citation(s) in RCA: 669] [Impact Index Per Article: 44.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2009] [Accepted: 07/13/2009] [Indexed: 12/24/2022]
Abstract
RNA is sensed by Toll-like receptor 7 (TLR7) and TLR8 or by the RNA helicases LGP2, Mda5 and RIG-I to trigger antiviral responses. Much less is known about sensors for DNA. Here we identify a novel DNA-sensing pathway involving RNA polymerase III and RIG-I. In this pathway, AT-rich double-stranded DNA (dsDNA) served as a template for RNA polymerase III and was transcribed into double-stranded RNA (dsRNA) containing a 5'-triphosphate moiety. Activation of RIG-I by this dsRNA induced production of type I interferon and activation of the transcription factor NF-kappaB. This pathway was important in the sensing of Epstein-Barr virus-encoded small RNAs, which were transcribed by RNA polymerase III and then triggered RIG-I activation. Thus, RNA polymerase III and RIG-I are pivotal in sensing viral DNA.
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Affiliation(s)
- Andrea Ablasser
- Institute for Clinical Chemistry and Pharmacology, University of Bonn, 53127 Bonn, Germany
| | - Franz Bauernfeind
- Institute for Clinical Chemistry and Pharmacology, University of Bonn, 53127 Bonn, Germany
| | - Gunther Hartmann
- Institute for Clinical Chemistry and Pharmacology, University of Bonn, 53127 Bonn, Germany
| | - Eicke Latz
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Katherine A. Fitzgerald
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Veit Hornung
- Institute for Clinical Chemistry and Pharmacology, University of Bonn, 53127 Bonn, Germany
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1385
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Kenworthy R, Lambert D, Yang F, Wang N, Chen Z, Zhu H, Zhu F, Liu C, Li K, Tang H. Short-hairpin RNAs delivered by lentiviral vector transduction trigger RIG-I-mediated IFN activation. Nucleic Acids Res 2009; 37:6587-99. [PMID: 19729514 PMCID: PMC2770676 DOI: 10.1093/nar/gkp714] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 08/13/2009] [Accepted: 08/14/2009] [Indexed: 12/25/2022] Open
Abstract
Activation of the type I interferon (IFN) pathway by small interfering RNA (siRNA) is a major contributor to the off-target effects of RNA interference in mammalian cells. While IFN induction complicates gene function studies, immunostimulation by siRNAs may be beneficial in certain therapeutic settings. Various forms of siRNA, meeting different compositional and structural requirements, have been reported to trigger IFN activation. The consensus is that intracellularly expressed short-hairpin RNAs (shRNAs) are less prone to IFN activation because they are not detected by the cell-surface receptors. In particular, lentiviral vector-mediated transduction of shRNAs has been reported to avoid IFN response. Here we identify a shRNA that potently activates the IFN pathway in human cells in a sequence- and 5'-triphosphate-dependent manner. In addition to suppressing its intended mRNA target, expression of the shRNA results in dimerization of interferon regulatory factor-3, activation of IFN promoters and secretion of biologically active IFNs into the extracellular medium. Delivery by lentiviral vector transduction did not avoid IFN activation by this and another, unrelated shRNA. We also demonstrated that retinoic-acid-inducible gene I, and not melanoma differentiation associated gene 5 or toll-like receptor 3, is the cytoplasmic sensor for intracellularly expressed shRNAs that trigger IFN activation.
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Affiliation(s)
- Rachael Kenworthy
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555 and Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Diana Lambert
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555 and Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Feng Yang
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555 and Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Nan Wang
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555 and Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Zihong Chen
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555 and Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Haizhen Zhu
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555 and Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Fanxiu Zhu
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555 and Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Chen Liu
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555 and Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Kui Li
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555 and Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Hengli Tang
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555 and Department of Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, FL 32611, USA
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1386
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STING regulates intracellular DNA-mediated, type I interferon-dependent innate immunity. Nature 2009; 461:788-92. [PMID: 19776740 DOI: 10.1038/nature08476] [Citation(s) in RCA: 1914] [Impact Index Per Article: 127.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2009] [Accepted: 09/03/2009] [Indexed: 11/09/2022]
Abstract
The innate immune system is critical for the early detection of invading pathogens and for initiating cellular host defence countermeasures, which include the production of type I interferon (IFN). However, little is known about how the innate immune system is galvanized to respond to DNA-based microbes. Here we show that STING (stimulator of interferon genes) is critical for the induction of IFN by non-CpG intracellular DNA species produced by various DNA pathogens after infection. Murine embryonic fibroblasts, as well as antigen presenting cells such as macrophages and dendritic cells (exposed to intracellular B-form DNA, the DNA virus herpes simplex virus 1 (HSV-1) or bacteria Listeria monocytogenes), were found to require STING to initiate effective IFN production. Accordingly, Sting-knockout mice were susceptible to lethal infection after exposure to HSV-1. The importance of STING in facilitating DNA-mediated innate immune responses was further evident because cytotoxic T-cell responses induced by plasmid DNA vaccination were reduced in Sting-deficient animals. In the presence of intracellular DNA, STING relocalized with TANK-binding kinase 1 (TBK1) from the endoplasmic reticulum to perinuclear vesicles containing the exocyst component Sec5 (also known as EXOC2). Collectively, our studies indicate that STING is essential for host defence against DNA pathogens such as HSV-1 and facilitates the adjuvant activity of DNA-based vaccines.
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1387
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Karayel E, Bürckstümmer T, Bilban M, Dürnberger G, Weitzer S, Martinez J, Superti-Furga G. The TLR-independent DNA recognition pathway in murine macrophages: Ligand features and molecular signature. Eur J Immunol 2009; 39:1929-36. [PMID: 19551900 DOI: 10.1002/eji.200939344] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Recognition of foreign DNA by cytosolic innate immune receptors triggers the production of IFN-beta. However, it is unclear whether different types of DNA ligands are recognized by similar receptors and whether the resulting response is distinct from the endosomal TLR response. To address these questions, we compared the two most commonly used types of DNA ligands (IFN-stimulatory DNA (ISD) and poly(dAdT)) and assessed the minimal structural requirements for stimulatory capacity in RAW264.7 cells. Gene expression signatures and competition experiments suggest that ISD and poly(dAdT) are qualitatively indistinguishable and differ from the CpG-containing oligonucleotides triggering the TLR9 pathway. Structure - activity relationship analyses revealed that a minimal length of two helical turns is sufficient for ISD-mediated IFN-beta induction, while phosphorylation at the 5'-end is dispensable. Altogether, our data suggest that, in murine macrophages, only one major cytosolic DNA recognition pathway is operational.
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Affiliation(s)
- Evren Karayel
- Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
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1388
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Expression profile of HIN200 in leukocytes and renal biopsy of SLE patients by real-time RT-PCR. Lupus 2009; 18:1066-72. [DOI: 10.1177/0961203309106699] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
HIN200 is a human IFN-inducible gene and homologous to murine IFI202 gene, which was identified as a candidate gene for SLE susceptibility in lupus mouse model. We determined these gene expressions in leukocytes from 20 SLE patients and 10 healthy controls and in renal biopsies from 29 SLE patients and 15 kidney donors using sensitive real-time reverse transcriptase–polymerase chain reaction (RT-PCR). The expressions of MNDA, IFIX, IFI16 and AIM2 genes significantly increased in leukocytes but not in kidney biopsies from SLE patients as compared to the control individuals, with P = 0.0003, P = 0.0056, P = 0.0002 and P < 0.0001, respectively. We also assessed the expression profiles of IFIX and IFI16 isoforms using semi-quantitative RT-PCR. We found up-regulation of B isoform (short product) of IFI16 in SLE patients. In addition, the expression levels were analyzed in correlation with disease activity and clinical characteristics. Interestingly, higher expression of MNDA was observed in patients who were positive for anti-dsDNA antibodies than in patients who were negative ( P = 0.0276). In conclusion, it is suggested that the HIN200 genes have a role in SLE pathogenesis. Our study also observed a possible important role of a specific short isoform of IFI16 as well as a link between MNDA and anti-dsDNA antibody production.
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1389
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Postigo A, Ferrer PE. Viral inhibitors reveal overlapping themes in regulation of cell death and innate immunity. Microbes Infect 2009; 11:1071-8. [PMID: 19733680 PMCID: PMC7110534 DOI: 10.1016/j.micinf.2009.08.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Many viruses regulate a crucial point in the apoptotic pathway by expressing viral Bcl-2 homologues, which have become useful tools to investigate the mechanisms behind the control of the mitochondrial checkpoint of apoptosis. Concurrently, a number of viral inhibitors of innate immune signalling have been instrumental tools in the discovery of key host pathways. Here we discuss how viral inhibitors of the apoptotic and innate signalling pathways have further enhanced the understanding of both research fields and are beginning to shed light on how these two pathways converge.
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Affiliation(s)
- Antonio Postigo
- Cell Motility Laboratory, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, UK.
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1390
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Plumlee CR, Lee C, Beg AA, Decker T, Shuman HA, Schindler C. Interferons direct an effective innate response to Legionella pneumophila infection. J Biol Chem 2009; 284:30058-66. [PMID: 19720834 DOI: 10.1074/jbc.m109.018283] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Legionella pneumophila remains an important opportunistic pathogen of human macrophages. Its more limited ability to replicate in murine macrophages has been attributed to redundant innate sensor systems that detect and effectively respond to this infection. The current studies evaluate the role of one of these innate response systems, the type I interferon (IFN-I) autocrine loop. The ability of L. pneumophila to induce IFN-I expression was found to be dependent on IRF-3, but not NF-kappaB. Secreted IFN-Is then in turn suppress the intracellular replication of L. pneumophila. Surprisingly, this suppression is mediated by a pathway that is independent of Stat1, Stat2, Stat3, but correlates with the polarization of macrophages toward the M1 or classically activated phenotype.
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Affiliation(s)
- Courtney R Plumlee
- Department of Biological Sciences, Columbia University, New York, New York 10032, USA
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1391
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Molecular mechanisms involved in inflammasome activation. Trends Cell Biol 2009; 19:455-64. [PMID: 19716304 DOI: 10.1016/j.tcb.2009.06.002] [Citation(s) in RCA: 266] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 06/20/2009] [Accepted: 06/23/2009] [Indexed: 12/21/2022]
Abstract
Germline-encoded pattern recognition receptors (PRRs) sense microbial or endogenous products released from damaged or dying cells and trigger innate immunity. In most cases, sensing of these signals is coupled to signal transduction pathways that lead to transcription of immune response genes that combat infection or lead to cell death. Members of the NOD-like receptor (NLR) family assemble into large multiprotein complexes, termed inflammasomes. Inflammasomes do not regulate transcription of immune response genes, but activate caspase-1, a proteolytic enzyme that cleaves and activates the secreted cytokines interleukin-1beta and interleukin-18. Inflammasomes also regulate pyroptosis, a caspase-1-dependent form of cell death that is highly inflammatory. Here, we review exciting recent developments on the role of inflammasome complexes in host defense and the discovery of a new DNA sensing inflammasome, and describe important progress made in our understanding of how inflammasomes are activated. Additionally, we highlight how dysregulation of inflammasomes contributes to human disease.
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1392
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Ranjan P, Bowzard JB, Schwerzmann JW, Jeisy-Scott V, Fujita T, Sambhara S. Cytoplasmic nucleic acid sensors in antiviral immunity. Trends Mol Med 2009; 15:359-68. [PMID: 19665430 DOI: 10.1016/j.molmed.2009.06.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 06/10/2009] [Accepted: 06/10/2009] [Indexed: 12/17/2022]
Abstract
The innate immune system uses pattern recognition receptors (PRRs) to sense invading microbes and initiate a rapid protective response. PRRs bind and are activated by structural motifs, such as nucleic acids or bacterial and fungal cell wall components, collectively known as pathogen-associated molecular patterns. PRRs that recognize pathogen-derived nucleic acids are present in vesicular compartments and in the cytosol of most cell types. Here, we review recent studies of these cytosolic sensors, focusing on the nature of the ligands for DNA-dependent activator of interferon (DAI)-regulatory factors, absent in melanoma 2 (AIM2), and the retinoic acid-inducible gene I-like helicase (RLH) family of receptors, the basis of ligand recognition and the signaling pathways triggered by the activation of these receptors. An increased understanding of these molecular aspects of innate immunity will guide the development of novel antiviral therapeutics.
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Affiliation(s)
- Priya Ranjan
- Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
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1393
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Dorhoi A, Kaufmann SHE. Fine-tuning of T cell responses during infection. Curr Opin Immunol 2009; 21:367-77. [PMID: 19646852 DOI: 10.1016/j.coi.2009.07.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Accepted: 07/06/2009] [Indexed: 12/20/2022]
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1394
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Vilaysane A, Muruve DA. The innate immune response to DNA. Semin Immunol 2009; 21:208-14. [DOI: 10.1016/j.smim.2009.05.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Accepted: 05/06/2009] [Indexed: 12/25/2022]
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1395
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Yasuda K, Richez C, Uccellini MB, Richards RJ, Bonegio RG, Akira S, Monestier M, Corley RB, Viglianti GA, Marshak-Rothstein A, Rifkin IR. Requirement for DNA CpG content in TLR9-dependent dendritic cell activation induced by DNA-containing immune complexes. THE JOURNAL OF IMMUNOLOGY 2009; 183:3109-17. [PMID: 19648272 DOI: 10.4049/jimmunol.0900399] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Although TLR9 was originally thought to specifically recognize microbial DNA, it is now evident that mammalian DNA can be an effective TLR9 ligand. However, the DNA sequence required for TLR9 activation is controversial, as studies have shown conflicting results depending on the nature of the DNA backbone, the route of DNA uptake, and the cell type being studied. In systemic lupus erythematosus, a major route whereby DNA gains access to intracellular TLR9, and thereby activates dendritic cells (DCs), is through uptake as a DNA-containing immune complex. In this report, we used defined dsDNA fragments with a natural (phosphodiester) backbone and show that unmethylated CpG dinucleotides within dsDNA are required for murine DC TLR9 activation induced by a DNA-containing immune complex. The strongest activation is seen with dsDNA fragments containing optimal CpG motifs (purine-purine-CpG-pyrimidine-pyrimidine) that are common in microbial DNA but rare in mammalian DNA. Importantly, however, activation can also be induced by CpG-rich DNA fragments that lack these optimal CpG motifs and that we show are plentiful in CpG islands within mammalian DNA. No activation is induced by DNA fragments lacking CpG dinucleotides, although this CpG-free DNA can induce DC activation if internalized by liposomal transfection instead of as an immune complex. Overall, the data suggest that the release of CpG-rich DNA from mammalian DNA may contribute to the pathogenesis of autoimmune diseases such as systemic lupus erythematosus and psoriasis in which activation of TLR9 in DCs by self DNA has been implicated in disease pathogenesis.
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Affiliation(s)
- Kei Yasuda
- Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA.
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1396
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Schroder K, Muruve DA, Tschopp J. Innate immunity: cytoplasmic DNA sensing by the AIM2 inflammasome. Curr Biol 2009; 19:R262-5. [PMID: 19321146 DOI: 10.1016/j.cub.2009.02.011] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Cytoplasmic double-stranded DNA triggers cell death and secretion of the pro-inflammatory cytokine IL-1beta in macrophages. Recent reports now describe the mechanism underlying this observation. Upon sensing of DNA, the HIN-200 family member AIM2 triggers the assembly of the inflammasome, culminating in caspase-1 activation, IL-1beta maturation and pyroptotic cell death.
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Affiliation(s)
- Kate Schroder
- Department of Biochemistry, University of Lausanne, Epalinges, Switzerland
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1397
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Larsen KC, Spencer AJ, Goodman AL, Gilchrist A, Furze J, Rollier CS, Kiss-Toth E, Gilbert SC, Bregu M, Soilleux EJ, Hill AVS, Wyllie DH. Expression of tak1 and tram induces synergistic pro-inflammatory signalling and adjuvants DNA vaccines. Vaccine 2009; 27:5589-98. [PMID: 19646407 DOI: 10.1016/j.vaccine.2009.07.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Revised: 05/21/2009] [Accepted: 07/13/2009] [Indexed: 01/07/2023]
Abstract
Improving vaccine immunogenicity remains a major challenge in the fight against developing country diseases like malaria and AIDS. We describe a novel strategy to identify new DNA vaccine adjuvants. We have screened components of the Toll-like receptor signalling pathways for their ability to activate pro-inflammatory target genes in transient transfection assays and assessed in vivo adjuvant activity by expressing the activators from the DNA backbone of vaccines. We find that a robust increase in the immune response necessitates co-expression of two activators. Accordingly, the combination of tak1 and tram elicits synergistic reporter activation in transient transfection assays. In a mouse model this combination, but not the individual molecules, induced approximately twofold increases in CD8+ T-cell immune responses. These results indicate that optimal immunogenicity may require activation of distinct innate immune signalling pathways. Thus this strategy offers a novel route to the discovery of a new generation of adjuvants.
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1398
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Vance RE, Isberg RR, Portnoy DA. Patterns of pathogenesis: discrimination of pathogenic and nonpathogenic microbes by the innate immune system. Cell Host Microbe 2009; 6:10-21. [PMID: 19616762 PMCID: PMC2777727 DOI: 10.1016/j.chom.2009.06.007] [Citation(s) in RCA: 394] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Revised: 06/19/2009] [Accepted: 06/19/2009] [Indexed: 01/01/2023]
Abstract
The dominant conceptual framework for understanding innate immunity has been that host cells respond to evolutionarily conserved molecular features of pathogens called pathogen-associated molecular patterns (PAMPs). Here, we propose that PAMPs should be understood in the context of how they are naturally presented by pathogens. This can be experimentally challenging, since pathogens, almost by definition, bypass host defense. Nevertheless, in this review, we explore the idea that the immune system responds to PAMPs in the context of additional signals that derive from common "patterns of pathogenesis" employed by pathogens to infect, multiply within, and spread among their hosts.
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Affiliation(s)
- Russell E Vance
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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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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1400
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DAI/ZBP1 recruits RIP1 and RIP3 through RIP homotypic interaction motifs to activate NF-kappaB. EMBO Rep 2009; 10:916-22. [PMID: 19590578 DOI: 10.1038/embor.2009.109] [Citation(s) in RCA: 260] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2008] [Revised: 03/27/2009] [Accepted: 04/20/2009] [Indexed: 12/24/2022] Open
Abstract
Detection of viral nucleic acids is central to antiviral immunity. Recently, DAI/ZBP1 (DNA-dependent activator of IRFs/Z-DNA binding protein 1) was identified as a cytoplasmic DNA sensor and shown to activate the interferon regulatory factor (IRF) and nuclear factor-kappa B (NF-kappaB) transcription factors, leading to type-I interferon production. DAI-induced IRF activation depends on TANK-binding kinase 1 (TBK1), whereas signalling pathways and molecular components involved in NF-kappaB activation remain elusive. Here, we report the identification of two receptor-interacting protein (RIP) homotypic interaction motifs (RHIMs) in the DAI protein sequence, and show that these domains relay DAI-induced NF-kappaB signals through the recruitment of the RHIM-containing kinases RIP1 and RIP3. We show that knockdown of not only RIP1, but also RIP3 affects DAI-induced NF-kappaB activation. Importantly, RIP recruitment to DAI is inhibited by the RHIM-containing murine cytomegalovirus (MCMV) protein M45. These findings delineate the DAI signalling pathway to NF-kappaB and suggest a possible new immune modulation strategy of the MCMV.
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