Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
PLoS Pathog. 2012;8(6):e1002780. doi: 10.1371/journal.ppat.1002780. Epub 2012 Jun 28.
Dengue is one of the most important arboviral diseases caused by infection of four serotypes of dengue virus (DEN). We found that activation of interferon regulatory factor 3 (IRF3) triggered by viral infection and by foreign DNA and RNA stimulation was blocked by DEN-encoded NS2B3 through a protease-dependent mechanism. The key adaptor protein in type I interferon pathway, human mediator of IRF3 activation (MITA) but not the murine homologue MPYS, was cleaved in cells infected with DEN-1 or DEN-2 and with expression of the enzymatically active protease NS2B3. The cleavage site of MITA was mapped to LRR↓(96)G and the function of MITA was suppressed by dengue protease. DEN replication was reduced with overexpression of MPYS but not with MITA, while DEN replication was enhanced by MPYS knockdown, indicating an antiviral role of MITA/MPYS against DEN infection. The involvement of MITA in DEN-triggered innate immune response was evidenced by reduction of IRF3 activation and IFN induction in cells with MITA knockdown upon DEN-2 infection. NS2B3 physically interacted with MITA, and the interaction and cleavage of MITA could be further enhanced by poly(dA:dT) stimulation. Thus, we identified MITA as a novel host target of DEN protease and provide the molecular mechanism of how DEN subverts the host innate immunity.
登革热是由四种登革病毒血清型（DEN）感染引起的最重要的虫媒病毒病之一。我们发现，病毒感染和外源 DNA 和 RNA 刺激引发的干扰素调节因子 3（IRF3）的激活被 DEN 编码的 NS2B3 通过依赖蛋白酶的机制阻断。I 型干扰素途径中的关键衔接蛋白、人类 IRF3 激活的介体（MITA），而不是鼠同源物 MPYS，在感染 DEN-1 或 DEN-2 的细胞中和表达具有酶活性的蛋白酶 NS2B3 时被切割。MITA 的切割位点被定位到 LRR↓（96）G，登革热蛋白酶抑制了 MITA 的功能。过表达 MPYS 可降低 DEN 复制，但 MITA 则不行，而 MPYS 敲低则增强 DEN 复制，表明 MITA/MPYS 对 DEN 感染具有抗病毒作用。MITA 在 DEN 触发的固有免疫反应中的参与作用，通过 DEN-2 感染时 MITA 敲低的细胞中 IRF3 激活和 IFN 诱导的减少得到证实。NS2B3 与 MITA 发生物理相互作用，并且多聚（dA:dT）刺激可进一步增强两者的相互作用和切割。因此，我们鉴定了 MITA 作为 DEN 蛋白酶的一种新的宿主靶标，并提供了 DEN 如何颠覆宿主固有免疫的分子机制。
