DiPerna Gary, Stack Julianne, Bowie Andrew G, Boyd Annemarie, Kotwal Girish, Zhang Zhouning, Arvikar Sheila, Latz Eicke, Fitzgerald Katherine A, Marshall William L
Viral Immune Evasion Group, Department of Biochemistry, Trinity College, Dublin 2, Ireland.
J Biol Chem. 2004 Aug 27;279(35):36570-8. doi: 10.1074/jbc.M400567200. Epub 2004 Jun 23.
Poxviruses encode proteins that suppress host immune responses, including secreted decoy receptors for pro-inflammatory cytokines such as interleukin-1 (IL-1) and the vaccinia virus proteins A46R and A52R that inhibit intracellular signaling by members of the IL-1 receptor (IL-1R) and Toll-like receptor (TLR) family. In vivo, the TLRs mediate the innate immune response by serving as pathogen recognition receptors, whose oligomerized intracellular Toll/IL-1 receptor (TIR) domains can initiate innate immune signaling. A family of TIR domain-containing adapter molecules transduces signals from engaged receptors that ultimately activate NF-kappaB and/or interferon regulatory factor 3 (IRF3) to induce pro-inflammatory cytokines. Data base searches detected a significant similarity between the N1L protein of vaccinia virus and A52R, a poxvirus inhibitor of TIR signaling. Compared with other poxvirus virulence factors, the poxvirus N1L protein strongly affects virulence in vivo; however, the precise target of N1L was previously unknown. Here we show that N1L suppresses NF-kappaB activation following engagement of Toll/IL-1 receptors, tumor necrosis factor receptors, and lymphotoxin receptors. N1L inhibited receptor-, adapter-, TRAF-, and IKK-alpha and IKK-beta-dependent signaling to NF-kappaB. N1L associated with several components of the multisubunit I-kappaB kinase complex, most strongly associating with the kinase, TANK-binding kinase 1 (TBK1). Together these findings are consistent with the hypothesis that N1L disrupts signaling to NF-kappaB by Toll/IL-1Rs and TNF superfamily receptors by targeting the IKK complex for inhibition. Furthermore, N1L inhibited IRF3 signaling, which is also regulated by TBK1. These studies define a role for N1L as an immunomodulator of innate immunity by targeting components of NF-kappaB and IRF3 signaling pathways.
痘病毒编码抑制宿主免疫反应的蛋白质，包括促炎细胞因子（如白细胞介素 -1，IL-1）的分泌型诱饵受体，以及痘苗病毒蛋白A46R和A52R，它们可抑制IL-1受体（IL-1R）和Toll样受体（TLR）家族成员的细胞内信号传导。在体内，TLR作为病原体识别受体介导先天性免疫反应，其寡聚化的细胞内Toll/IL-1受体（TIR）结构域可启动先天性免疫信号传导。一类含TIR结构域的衔接分子转导来自结合受体的信号，最终激活核因子κB（NF-κB）和/或干扰素调节因子3（IRF3）以诱导促炎细胞因子。数据库搜索发现痘苗病毒的N1L蛋白与痘病毒TIR信号抑制剂A52R之间存在显著相似性。与其他痘病毒毒力因子相比，痘病毒N1L蛋白在体内强烈影响毒力；然而，N1L的确切靶点此前未知。在此我们表明，N1L在Toll/IL-1受体、肿瘤坏死因子受体和淋巴毒素受体结合后抑制NF-κB激活。N1L抑制受体、衔接分子、肿瘤坏死因子受体相关因子（TRAF）以及依赖IKK-α和IKK-β的NF-κB信号传导。N1L与多亚基I-κB激酶复合物的几个组分相关联，与激酶TANK结合激酶1（TBK1）的关联最为紧密。这些发现共同支持了以下假设：N1L通过靶向IKK复合物进行抑制，从而破坏Toll/IL-1R和TNF超家族受体向NF-κB的信号传导。此外，N1L抑制同样受TBK1调节的IRF3信号传导。这些研究确定了N1L作为先天性免疫的免疫调节剂的作用，其通过靶向NF-κB和IRF3信号通路的组分来发挥作用。
