A Study On Molecular Mechanism Of MAVS Induced Cell Apoptosis Through VDAC1

MAVS(mitochondria antiviral signaling protein) plays a very important role in innate immunity. MAVS localizes in the outer mitochondrial membrane and constitutes an N-terminal CARD(caspase recruitment domain)-like domian, a middle proline-rich domain and a C-terminal mitochondrial transmembrane sequence(TM). It can receive signals from upstream signaling molecule RIG-Ⅰas an adapter protein and recruit downstream signaling molecule TBK1 and IKKεso that transcription factors IRF-3 and IRF-7 are phosphorylated to form homodimer and remove to nucleus to promote expression of type I interferon(IFN). MAVS can also promote the formation of complex IKKα/β/γto activate transcription factor NF-κB. Activated NF-κB enters nucleus from cytoplasm to promote expression of many precursors of inflammatory cytokines for protecting the cell against viral infection. Recent studies showed that MAVS may get involved in cell apoptosis signaling pathway. First, the cleavage of MAVS in cell apoptosis was dependent on proteasome and caspase. Second, MAVS facilitated cell death by disrupting the mitochondrial membrane potential and by activating caspase-3, caspase-8 and caspase-9. Third, the effect of Sendai virus(SeV) infection was downregulated by MAVS RNA interfere. The Dengue virus(DEN) suppressed cell apoptosis by cleaving MAVS. However, its detailed functions in apoptosis are still unclear.VDAC(voltage-dependent anion channel) is located on the mitochondrial membrane like MAVS. There are three kinds of mammalian VDAC isoforms, VDAC1, VDAC2 and VDAC3, and VDAC1 is the main study object because it's the most abundant isoform in most cells. VDAC1 is involved in the mitochondrial energy metabolism and is used for ATP/ADP transport between mitochondria and cytoplasm. Meanwhile it also allows Cytochrome C to remove from mitochondria to cytoplasm which indicates it's the key component in cell apoptosis. Here we found that MAVS may participate in cell apoptosis signalling pathway through VDAC1.1. MAVS induces apoptosis:MAVS could induce dose-dependent cell apoptosis which was detected through MTT assay and Annexin V-FITC/PI dyed flow cytometry; MAVS could induce cell cycle arrest which was detected through cell cycle arrest assay.2. MAVS induced cell apoptosis requires its interaction with VDAC:small interferece RNA plasmid of VDAC1 was constructed and transfected into cells to knockdown VDAC1. The cell apoptosis induced by MAVS was suppressed in VDAC1 knockdown cells; Then fusion expression vectors of VDAC1 with different kinds of tag were constructed. The interaction of MAVS and VDAC1 was found by co-immunoprecipitation in vivo. The endogenous physiological interaction of MAVS and VDAC1 was found by immunoprecipitation. The direct interaction of MAVS and VDAC 1 was found by Far Western assay in vitro. The proline-rich domain was found to be required to interact with the a-helix domain of N-terminal of VDAC 1.3. MAVS induced cell apoptosis through stablizing VDAC1:The expression of endogenous VDAC 1 protein was upregulated when MAVS was overexpressed; The expression of endogenous VDAC1 protein was downregulated in MAVS deficiency cell line.Taken together, these results suggest MAVS upregulates the expression of VDAC1 through the direct interaction with VDAC1 resulting in cell apoptosis. It is the first study on molecule mechanism of MAVS induced cell apoptosis through VDAC1, which broadens the function of MAVS from the field of innate immunity to the field of cell apoptosis. It may promote the mechanism research of virus induced cell apoptosis for its proliferation when it may also provide the foundation for the research and design of the antiviral drug.