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Decio L. Eizirik - One of the best experts on this subject based on the ideXlab platform.

  • MDA5 and ptpn2 two candidate genes for type 1 diabetes modify pancreatic β cell responses to the viral by product double stranded rna
    Human Molecular Genetics, 2010
    Co-Authors: Maikel L. Colli, Fabrice Moore, Esteban N. Gurzov, F Ortis, Decio L. Eizirik
    Abstract:

    β-Cell destruction in type 1 diabetes (T1D) is at least in part consequence of a ‘dialog’ between β-cells and immune system. This dialog may be affected by the individual's genetic background. We presently evaluated whether modulation of MDA5 and PTPN2, two candidate genes for T1D, affects β-cell responses to double-stranded RNA (dsRNA), a by-product of viral replication. These genes were selected following comparison between known candidate genes for T1D and genes expressed in pancreatic β-cells, as identified in previous array analysis. INS-1E cells and primary fluorescence-activated cell sorting-purified rat β-cells were transfected with small interference RNAs (siRNAs) targeting MDA5 or PTPN2 and subsequently exposed to intracellular synthetic dsRNA (polyinosinic–polycitidilic acid—PIC). Real-time RT–PCR, western blot and viability assays were performed to characterize gene/protein expression and viability. PIC increased MDA5 and PTPN2 mRNA expression, which was inhibited by the specific siRNAs. PIC triggered apoptosis in INS-1E and primary β-cells and this was augmented by PTPN2 knockdown (KD), although inhibition of MDA5 did not modify PIC-induced apoptosis. In contrast, MDA5 silencing decreased PIC-induced cytokine and chemokine expression, although inhibition of PTPN2 induced minor or no changes in these inflammatory mediators. These findings indicate that changes in MDA5 and PTPN2 expression modify β-cell responses to dsRNA. MDA5 regulates inflammatory signals, whereas PTPN2 may function as a defence mechanism against pro-apoptotic signals generated by dsRNA. These two candidate genes for T1D may thus modulate β-cell apoptosis and/or local release of inflammatory mediators in the course of a viral infection by acting, at least in part, at the pancreatic β-cell level.

  • MDA5 and PTPN2, two candidate genes for type 1 diabetes, modify pancreatic β-cell responses to the viral by-product double-stranded RNA
    Human Molecular Genetics, 2009
    Co-Authors: Maikel L. Colli, Fabrice Moore, Esteban N. Gurzov, F Ortis, Decio L. Eizirik
    Abstract:

    beta-Cell destruction in type 1 diabetes (T1D) is at least in part consequence of a 'dialog' between beta-cells and immune system. This dialog may be affected by the individual's genetic background. We presently evaluated whether modulation of MDA5 and PTPN2, two candidate genes for T1D, affects beta-cell responses to double-stranded RNA (dsRNA), a by-product of viral replication. These genes were selected following comparison between known candidate genes for T1D and genes expressed in pancreatic beta-cells, as identified in previous array analysis. INS-1E cells and primary fluorescence-activated cell sorting-purified rat beta-cells were transfected with small interference RNAs (siRNAs) targeting MDA5 or PTPN2 and subsequently exposed to intracellular synthetic dsRNA (polyinosinic-polycitidilic acid-PIC). Real-time RT-PCR, western blot and viability assays were performed to characterize gene/protein expression and viability. PIC increased MDA5 and PTPN2 mRNA expression, which was inhibited by the specific siRNAs. PIC triggered apoptosis in INS-1E and primary beta-cells and this was augmented by PTPN2 knockdown (KD), although inhibition of MDA5 did not modify PIC-induced apoptosis. In contrast, MDA5 silencing decreased PIC-induced cytokine and chemokine expression, although inhibition of PTPN2 induced minor or no changes in these inflammatory mediators. These findings indicate that changes in MDA5 and PTPN2 expression modify beta-cell responses to dsRNA. MDA5 regulates inflammatory signals, whereas PTPN2 may function as a defence mechanism against pro-apoptotic signals generated by dsRNA. These two candidate genes for T1D may thus modulate beta-cell apoptosis and/or local release of inflammatory mediators in the course of a viral infection by acting, at least in part, at the pancreatic beta-cell level.

Taro Kawai - One of the best experts on this subject based on the ideXlab platform.

  • negative regulation of melanoma differentiation associated gene 5 MDA5 dependent antiviral innate immune responses by arf like protein 5b
    Journal of Biological Chemistry, 2015
    Co-Authors: Yuichi Kitai, Osamu Takeuchi, Takumi Kawasaki, Takuya Sueyoshi, Motoya Murase, Shizuo Akira, Taro Kawai
    Abstract:

    Abstract RIG-I-like receptors (RLRs), including retinoic acid-inducible gene-I (RIG-I) and MDA5, constitute a family of cytoplasmic RNA helicases that senses viral RNA and mounts antiviral innate immunity by producing type I interferons and inflammatory cytokines. Despite their essential roles in antiviral host defense, RLR signaling is negatively regulated to protect the host from excessive inflammation and autoimmunity. Here, we identified ADP-ribosylation factor-like protein 5B (Arl5B), an Arl family small GTPase, as a regulator of RLR signaling through MDA5 but not RIG-I. Overexpression of Arl5B repressed interferon β promoter activation by MDA5 but not RIG-I, and its knockdown enhanced MDA5-mediated responses. Furthermore, Arl5B-deficient mouse embryonic fibroblast cells exhibited increased type I interferon expression in response to MDA5 agonists such as poly(I:C) and encephalomyocarditis virus. Arl5B-mediated negative regulation of MDA5 signaling does not require its GTP binding ability but requires Arl5B binding to the C-terminal domain of MDA5, which prevents interaction between MDA5 and poly(I:C). Our results, therefore, suggest that Arl5B is a negative regulator for MDA5.

  • negative regulation of MDA5 dependent antiviral innate immune responses by arl like protein 5b
    Journal of Biological Chemistry, 2014
    Co-Authors: Yuichi Kitai, Osamu Takeuchi, Takumi Kawasaki, Takuya Sueyoshi, Motoya Murase, Shizuo Akira, Taro Kawai
    Abstract:

    Abstract RIG-I-like receptors (RLRs), including RIG-I and MDA5, constitute a family of cytoplasmic RNA helicases that sense viral RNA and mount antiviral innate immunity by producing type I interferons and inflammatory cytokines. Despite their essential roles in antiviral host defense, RLR signaling is negatively regulated to protect the host from excessive inflammation and autoimmunity. Here, we identified Arl5B, an Arl family small GTPase, as a regulator of RLR signaling through MDA5 but not RIG-I. Overexpression of Arl5B repressed interferon β promoter activation by MDA5 but not RIG-I, and its knockdown enhanced MDA5-mediated responses. Furthermore, Arl5B-deficient mouse embryonic fibroblast cells exhibited increased type I interferon expression in response to MDA5 agonists such as polyI:C and encephalomyocarditis virus. Arl5B-mediated negative regulation of MDA5 signaling does not require its GTP-binding ability, but requires Arl5B binding to the C-terminal domain of MDA5, which prevents interaction between MDA5 and polyI:C. Our results therefore suggest that Arl5B is a negative regulator for MDA5.

  • differential roles of MDA5 and rig i helicases in the recognition of rna viruses
    Nature, 2006
    Co-Authors: Hiroki Kato, Osamu Takeuchi, Taro Kawai, Shintaro Sato, Mitsutoshi Yoneyama, Masahiro Yamamoto, Kosuke Matsui, Satoshi Uematsu, Andreas Jung, Ken J Ishii
    Abstract:

    The innate immune system senses viral infection by recognizing a variety of viral components (including double-stranded (ds)RNA) and triggers antiviral responses1,2. The cytoplasmic helicase proteins RIG-I (retinoic-acid-inducible protein I, also known as Ddx58) and MDA5 (melanoma-differentiation-associated gene 5, also known as Ifih1 or Helicard) have been implicated in viral dsRNA recognition3,4,5,6,7. In vitro studies suggest that both RIG-I and MDA5 detect RNA viruses and polyinosine-polycytidylic acid (poly(I:C)), a synthetic dsRNA analogue3. Although a critical role for RIG-I in the recognition of several RNA viruses has been clarified8, the functional role of MDA5 and the relationship between these dsRNA detectors in vivo are yet to be determined. Here we use mice deficient in MDA5 (MDA5-/-) to show that MDA5 and RIG-I recognize different types of dsRNAs: MDA5 recognizes poly(I:C), and RIG-I detects in vitro transcribed dsRNAs. RNA viruses are also differentially recognized by RIG-I and MDA5. We find that RIG-I is essential for the production of interferons in response to RNA viruses including paramyxoviruses, influenza virus and Japanese encephalitis virus, whereas MDA5 is critical for picornavirus detection. Furthermore, RIG-I-/- and MDA5-/- mice are highly susceptible to infection with these respective RNA viruses compared to control mice. Together, our data show that RIG-I and MDA5 distinguish different RNA viruses and are critical for host antiviral responses.

Maikel L. Colli - One of the best experts on this subject based on the ideXlab platform.

  • MDA5 and ptpn2 two candidate genes for type 1 diabetes modify pancreatic β cell responses to the viral by product double stranded rna
    Human Molecular Genetics, 2010
    Co-Authors: Maikel L. Colli, Fabrice Moore, Esteban N. Gurzov, F Ortis, Decio L. Eizirik
    Abstract:

    β-Cell destruction in type 1 diabetes (T1D) is at least in part consequence of a ‘dialog’ between β-cells and immune system. This dialog may be affected by the individual's genetic background. We presently evaluated whether modulation of MDA5 and PTPN2, two candidate genes for T1D, affects β-cell responses to double-stranded RNA (dsRNA), a by-product of viral replication. These genes were selected following comparison between known candidate genes for T1D and genes expressed in pancreatic β-cells, as identified in previous array analysis. INS-1E cells and primary fluorescence-activated cell sorting-purified rat β-cells were transfected with small interference RNAs (siRNAs) targeting MDA5 or PTPN2 and subsequently exposed to intracellular synthetic dsRNA (polyinosinic–polycitidilic acid—PIC). Real-time RT–PCR, western blot and viability assays were performed to characterize gene/protein expression and viability. PIC increased MDA5 and PTPN2 mRNA expression, which was inhibited by the specific siRNAs. PIC triggered apoptosis in INS-1E and primary β-cells and this was augmented by PTPN2 knockdown (KD), although inhibition of MDA5 did not modify PIC-induced apoptosis. In contrast, MDA5 silencing decreased PIC-induced cytokine and chemokine expression, although inhibition of PTPN2 induced minor or no changes in these inflammatory mediators. These findings indicate that changes in MDA5 and PTPN2 expression modify β-cell responses to dsRNA. MDA5 regulates inflammatory signals, whereas PTPN2 may function as a defence mechanism against pro-apoptotic signals generated by dsRNA. These two candidate genes for T1D may thus modulate β-cell apoptosis and/or local release of inflammatory mediators in the course of a viral infection by acting, at least in part, at the pancreatic β-cell level.

  • MDA5 and PTPN2, two candidate genes for type 1 diabetes, modify pancreatic β-cell responses to the viral by-product double-stranded RNA
    Human Molecular Genetics, 2009
    Co-Authors: Maikel L. Colli, Fabrice Moore, Esteban N. Gurzov, F Ortis, Decio L. Eizirik
    Abstract:

    beta-Cell destruction in type 1 diabetes (T1D) is at least in part consequence of a 'dialog' between beta-cells and immune system. This dialog may be affected by the individual's genetic background. We presently evaluated whether modulation of MDA5 and PTPN2, two candidate genes for T1D, affects beta-cell responses to double-stranded RNA (dsRNA), a by-product of viral replication. These genes were selected following comparison between known candidate genes for T1D and genes expressed in pancreatic beta-cells, as identified in previous array analysis. INS-1E cells and primary fluorescence-activated cell sorting-purified rat beta-cells were transfected with small interference RNAs (siRNAs) targeting MDA5 or PTPN2 and subsequently exposed to intracellular synthetic dsRNA (polyinosinic-polycitidilic acid-PIC). Real-time RT-PCR, western blot and viability assays were performed to characterize gene/protein expression and viability. PIC increased MDA5 and PTPN2 mRNA expression, which was inhibited by the specific siRNAs. PIC triggered apoptosis in INS-1E and primary beta-cells and this was augmented by PTPN2 knockdown (KD), although inhibition of MDA5 did not modify PIC-induced apoptosis. In contrast, MDA5 silencing decreased PIC-induced cytokine and chemokine expression, although inhibition of PTPN2 induced minor or no changes in these inflammatory mediators. These findings indicate that changes in MDA5 and PTPN2 expression modify beta-cell responses to dsRNA. MDA5 regulates inflammatory signals, whereas PTPN2 may function as a defence mechanism against pro-apoptotic signals generated by dsRNA. These two candidate genes for T1D may thus modulate beta-cell apoptosis and/or local release of inflammatory mediators in the course of a viral infection by acting, at least in part, at the pancreatic beta-cell level.

Yuichi Kitai - One of the best experts on this subject based on the ideXlab platform.

  • negative regulation of melanoma differentiation associated gene 5 MDA5 dependent antiviral innate immune responses by arf like protein 5b
    Journal of Biological Chemistry, 2015
    Co-Authors: Yuichi Kitai, Osamu Takeuchi, Takumi Kawasaki, Takuya Sueyoshi, Motoya Murase, Shizuo Akira, Taro Kawai
    Abstract:

    Abstract RIG-I-like receptors (RLRs), including retinoic acid-inducible gene-I (RIG-I) and MDA5, constitute a family of cytoplasmic RNA helicases that senses viral RNA and mounts antiviral innate immunity by producing type I interferons and inflammatory cytokines. Despite their essential roles in antiviral host defense, RLR signaling is negatively regulated to protect the host from excessive inflammation and autoimmunity. Here, we identified ADP-ribosylation factor-like protein 5B (Arl5B), an Arl family small GTPase, as a regulator of RLR signaling through MDA5 but not RIG-I. Overexpression of Arl5B repressed interferon β promoter activation by MDA5 but not RIG-I, and its knockdown enhanced MDA5-mediated responses. Furthermore, Arl5B-deficient mouse embryonic fibroblast cells exhibited increased type I interferon expression in response to MDA5 agonists such as poly(I:C) and encephalomyocarditis virus. Arl5B-mediated negative regulation of MDA5 signaling does not require its GTP binding ability but requires Arl5B binding to the C-terminal domain of MDA5, which prevents interaction between MDA5 and poly(I:C). Our results, therefore, suggest that Arl5B is a negative regulator for MDA5.

  • negative regulation of MDA5 dependent antiviral innate immune responses by arl like protein 5b
    Journal of Biological Chemistry, 2014
    Co-Authors: Yuichi Kitai, Osamu Takeuchi, Takumi Kawasaki, Takuya Sueyoshi, Motoya Murase, Shizuo Akira, Taro Kawai
    Abstract:

    Abstract RIG-I-like receptors (RLRs), including RIG-I and MDA5, constitute a family of cytoplasmic RNA helicases that sense viral RNA and mount antiviral innate immunity by producing type I interferons and inflammatory cytokines. Despite their essential roles in antiviral host defense, RLR signaling is negatively regulated to protect the host from excessive inflammation and autoimmunity. Here, we identified Arl5B, an Arl family small GTPase, as a regulator of RLR signaling through MDA5 but not RIG-I. Overexpression of Arl5B repressed interferon β promoter activation by MDA5 but not RIG-I, and its knockdown enhanced MDA5-mediated responses. Furthermore, Arl5B-deficient mouse embryonic fibroblast cells exhibited increased type I interferon expression in response to MDA5 agonists such as polyI:C and encephalomyocarditis virus. Arl5B-mediated negative regulation of MDA5 signaling does not require its GTP-binding ability, but requires Arl5B binding to the C-terminal domain of MDA5, which prevents interaction between MDA5 and polyI:C. Our results therefore suggest that Arl5B is a negative regulator for MDA5.

Osamu Takeuchi - One of the best experts on this subject based on the ideXlab platform.

  • negative regulation of melanoma differentiation associated gene 5 MDA5 dependent antiviral innate immune responses by arf like protein 5b
    Journal of Biological Chemistry, 2015
    Co-Authors: Yuichi Kitai, Osamu Takeuchi, Takumi Kawasaki, Takuya Sueyoshi, Motoya Murase, Shizuo Akira, Taro Kawai
    Abstract:

    Abstract RIG-I-like receptors (RLRs), including retinoic acid-inducible gene-I (RIG-I) and MDA5, constitute a family of cytoplasmic RNA helicases that senses viral RNA and mounts antiviral innate immunity by producing type I interferons and inflammatory cytokines. Despite their essential roles in antiviral host defense, RLR signaling is negatively regulated to protect the host from excessive inflammation and autoimmunity. Here, we identified ADP-ribosylation factor-like protein 5B (Arl5B), an Arl family small GTPase, as a regulator of RLR signaling through MDA5 but not RIG-I. Overexpression of Arl5B repressed interferon β promoter activation by MDA5 but not RIG-I, and its knockdown enhanced MDA5-mediated responses. Furthermore, Arl5B-deficient mouse embryonic fibroblast cells exhibited increased type I interferon expression in response to MDA5 agonists such as poly(I:C) and encephalomyocarditis virus. Arl5B-mediated negative regulation of MDA5 signaling does not require its GTP binding ability but requires Arl5B binding to the C-terminal domain of MDA5, which prevents interaction between MDA5 and poly(I:C). Our results, therefore, suggest that Arl5B is a negative regulator for MDA5.

  • negative regulation of MDA5 dependent antiviral innate immune responses by arl like protein 5b
    Journal of Biological Chemistry, 2014
    Co-Authors: Yuichi Kitai, Osamu Takeuchi, Takumi Kawasaki, Takuya Sueyoshi, Motoya Murase, Shizuo Akira, Taro Kawai
    Abstract:

    Abstract RIG-I-like receptors (RLRs), including RIG-I and MDA5, constitute a family of cytoplasmic RNA helicases that sense viral RNA and mount antiviral innate immunity by producing type I interferons and inflammatory cytokines. Despite their essential roles in antiviral host defense, RLR signaling is negatively regulated to protect the host from excessive inflammation and autoimmunity. Here, we identified Arl5B, an Arl family small GTPase, as a regulator of RLR signaling through MDA5 but not RIG-I. Overexpression of Arl5B repressed interferon β promoter activation by MDA5 but not RIG-I, and its knockdown enhanced MDA5-mediated responses. Furthermore, Arl5B-deficient mouse embryonic fibroblast cells exhibited increased type I interferon expression in response to MDA5 agonists such as polyI:C and encephalomyocarditis virus. Arl5B-mediated negative regulation of MDA5 signaling does not require its GTP-binding ability, but requires Arl5B binding to the C-terminal domain of MDA5, which prevents interaction between MDA5 and polyI:C. Our results therefore suggest that Arl5B is a negative regulator for MDA5.

  • lgp2 is a positive regulator of rig i and MDA5 mediated antiviral responses
    Proceedings of the National Academy of Sciences of the United States of America, 2010
    Co-Authors: Takashi Satoh, Shizuo Akira, Hiroki Kato, Shintaro Sato, Mitsutoshi Yoneyama, Yutaro Kumagai, Kazufumi Matsushita, Tohru Tsujimura, Takashi Fujita, Osamu Takeuchi
    Abstract:

    RNA virus infection is recognized by retinoic acid-inducible gene (RIG)-I–like receptors (RLRs), RIG-I, and melanoma differentiation–associated gene 5 (MDA5) in the cytoplasm. RLRs are comprised of N-terminal caspase-recruitment domains (CARDs) and a DExD/H-box helicase domain. The third member of the RLR family, LGP2, lacks any CARDs and was originally identified as a negative regulator of RLR signaling. In the present study, we generated mice lacking LGP2 and found that LGP2 was required for RIG-I– and MDA5-mediated antiviral responses. In particular, LGP2 was essential for type I IFN production in response to picornaviridae infection. Overexpression of the CARDs from RIG-I and MDA5 in Lgp2 −/− fibroblasts activated the IFN-β promoter, suggesting that LGP2 acts upstream of RIG-I and MDA5. We further examined the role of the LGP2 helicase domain by generating mice harboring a point mutation of Lys-30 to Ala (Lgp2 K30A/K30A) that abrogated the LGP2 ATPase activity. Lgp2 K30A/K30A dendritic cells showed impaired IFN-β productions in response to various RNA viruses to extents similar to those of Lgp2 −/− cells. Lgp2 −/− and Lgp2 K30A/K30A mice were highly susceptible to encephalomyocarditis virus infection. Nevertheless, LGP2 and its ATPase activity were dispensable for the responses to synthetic RNA ligands for MDA5 and RIG-I. Taken together, the present data suggest that LGP2 facilitates viral RNA recognition by RIG-I and MDA5 through its ATPase domain.

  • LGP2 is a positive regulator of RIG-I– and MDA5-mediated antiviral responses
    Proceedings of the National Academy of Sciences of the United States of America, 2010
    Co-Authors: Takashi Satoh, Shizuo Akira, Hiroki Kato, Shintaro Sato, Mitsutoshi Yoneyama, Yutaro Kumagai, Kazufumi Matsushita, Tohru Tsujimura, Takashi Fujita, Osamu Takeuchi
    Abstract:

    RNA virus infection is recognized by retinoic acid-inducible gene (RIG)-I–like receptors (RLRs), RIG-I, and melanoma differentiation–associated gene 5 (MDA5) in the cytoplasm. RLRs are comprised of N-terminal caspase-recruitment domains (CARDs) and a DExD/H-box helicase domain. The third member of the RLR family, LGP2, lacks any CARDs and was originally identified as a negative regulator of RLR signaling. In the present study, we generated mice lacking LGP2 and found that LGP2 was required for RIG-I– and MDA5-mediated antiviral responses. In particular, LGP2 was essential for type I IFN production in response to picornaviridae infection. Overexpression of the CARDs from RIG-I and MDA5 in Lgp2 −/− fibroblasts activated the IFN-β promoter, suggesting that LGP2 acts upstream of RIG-I and MDA5. We further examined the role of the LGP2 helicase domain by generating mice harboring a point mutation of Lys-30 to Ala (Lgp2 K30A/K30A) that abrogated the LGP2 ATPase activity. Lgp2 K30A/K30A dendritic cells showed impaired IFN-β productions in response to various RNA viruses to extents similar to those of Lgp2 −/− cells. Lgp2 −/− and Lgp2 K30A/K30A mice were highly susceptible to encephalomyocarditis virus infection. Nevertheless, LGP2 and its ATPase activity were dispensable for the responses to synthetic RNA ligands for MDA5 and RIG-I. Taken together, the present data suggest that LGP2 facilitates viral RNA recognition by RIG-I and MDA5 through its ATPase domain.

  • activation of MDA5 requires higher order rna structures generated during virus infection
    Journal of Virology, 2009
    Co-Authors: Andreas Pichlmair, Osamu Takeuchi, Shizuo Akira, Hiroki Kato, Jan Rehwinkel, Oliver Schulz, Giampietro Schiavo, Caetano Reis E Sousa
    Abstract:

    Recognition of virus presence via RIG-I (retinoic acid inducible gene I) and/or MDA5 (melanoma differentiation-associated protein 5) initiates a signaling cascade that culminates in transcription of innate response genes such as those encoding the alpha/beta interferon (IFN-α/β) cytokines. It is generally assumed that MDA5 is activated by long molecules of double-stranded RNA (dsRNA) produced by annealing of complementary RNAs generated during viral infection. Here, we used an antibody to dsRNA to show that the presence of immunoreactivity in virus-infected cells does indeed correlate with the ability of RNA extracted from these cells to activate MDA5. Furthermore, RNA from cells infected with encephalomyocarditis virus or with vaccinia virus and precipitated with the anti-dsRNA antibody can bind to MDA5 and induce MDA5-dependent IFN-α/β production upon transfection into indicator cells. However, a prominent band of dsRNA apparent in cells infected with either virus does not stimulate IFN-α/β production. Instead, stimulatory activity resides in higher-order structured RNA that contains single-stranded RNA and dsRNA. These results suggest that MDA5 activation requires an RNA web rather than simply long molecules of dsRNA.