MAVS O-GlcNAcylation Is Essential for Host Antiviral Immunity against Lethal RNA Viruses.

It is known that lethal viruses profoundly manipulate host metabolism, but how the metabolism alternation affects the immediate host antiviral immunity remains elusive. Here, we report that the O-GlcNAcylation of mitochondrial antiviral-signaling protein (MAVS), a key mediator of interferon signaling, is a critical regulation to activate the host innate immunity against RNA viruses. We show that O-GlcNAcylation depletion in myeloid cells renders the host more susceptible to virus infection both in vitro and in vivo. Mechanistically, we demonstrate that MAVS O-GlcNAcylation is required for virus-induced MAVS K63-linked ubiquitination, thereby facilitating IRF3 activation and IFNß production. We further demonstrate that D-glucosamine, a commonly used dietary supplement, effectively protects mice against a range of lethal RNA viruses, including human influenza virus. Our study highlights a critical role of O-GlcNAcylation in regulating host antiviral immunity and validates D-glucosamine as a potential therapeutic for virus infections.

Interleukin-18 and interleukin-12 together downregulate ATP-binding cassette transporter A1 expression through the interleukin-18R/nuclear factor-κB signaling pathway in THP-1 macrophage-derived foam cells.

BACKGROUND: Interleukin (IL)-18 and IL-12 synergize for the production of interferon (IFN)-γ, which can downregulate ATP-binding cassette transporter A1 (ABCA1) expression. The aim of the present study was to investigate the effect of IL-18 and/or IL-12 on ABCA1 expression. METHODS AND RESULTS: IL-18 combined with IL-12 decreased ABCA1 expression and cellular cholesterol efflux in THP-1 macrophage-derived foam cells, whereas IL-18 or IL-12 alone had no effect. IL-12 increased IL-18 receptor (IL-18R) expression, which was suppressed by small interfering RNA (siRNA) for signal transducer and activator of transcription 3. IL-18R but not IL-12 receptor siRNA completely reversed the effects of IL-18 and IL-12 on ABCA1 expression and cellular cholesterol efflux. Treatment with IL-18 plus IL-12 markedly augmented nuclear translocation of nuclear factor (NF)-κB but had no effect on expression and activity of liver X receptor α. IL-18 and IL-12 also significantly increased zinc finger protein 202 (ZNF202) levels and IFN-γ secretion. Furthermore, siRNA for ZNF202 or IFN-γ significantly impaired IL-18/IL-12-induced suppression of ABCA1, whereas NF-κB siRNA treatment blocked IL-18/IL-12' action on ZNF202 levels, IFN-γ secretion, and ABCA1 expression. CONCLUSIONS: IL-18 and IL-12 together can decrease ABCA1 expression and cellular cholesterol efflux in THP-1 macrophage-derived foam cells through the IL-18R/NF-κB signaling pathway.