Mitochondrial antiviral-signaling protein (MAVS) transmits signals from RIG-I-like receptors after RNA virus infections. However, the mechanism by which MAVS activates downstream components, such as TBK1 and IKKα/β, is unclear, although previous work suggests the involvement of NEMO or TBK1-binding proteins TANK, NAP1, and SINTBAD. Here, we report that MAVS-mediated innate immune activation is dependent on TRAFs, partially on NEMO, but not on TBK1-binding proteins. MAVS recruited TBK1/IKKε by TRAFs that were pre-associated with TBK1/IKKε via direct interaction between the coiled-coil domain of TRAFs and the SDD domain of TBK1/IKKε. TRAF2^−/−3^−/−5^−/−6^−/− cells completely lost RNA virus responses. TRAFs’ E3 ligase activity was required for NEMO activation by synthesizing ubiquitin chains that bound to NEMO for NF-κB and TBK1/IKKε activation. NEMO-activated IKKα/β were important for TBK1/IKKε activation through IKKα/β-mediated TBK1/IKKε phosphorylation. Moreover, individual TRAFs differently mediated TBK1/IKKε activation and thus fine-tuned antiviral immunity under physiological conditions.

线粒体抗病毒信号蛋白（MAVS）在RNA病毒感染后从RIG-I样受体传递信号。然而，尽管以前的工作表明NEMO或TBK1结合蛋白TANK，NAP1和SINTBAD参与其中，但MAVS激活下游成分（如TBK1和IKKα/β）的机制尚不清楚。在这里，我们报告MAVS介导的先天免疫激活取决于TRAFs，部分取决于NEMO，而不取决于TBK1结合蛋白。MAVS通过TRAF的盘绕线圈结构域与TBK1 /IKKε的SDD结构域之间的直接相互作用，通过与TRKs预先关联的TRAF招募了TBK1 /IKKε。TRAF2 ^-/- 3 ^-/- 5 ^-/- 6 ^-/-细胞完全丧失了RNA病毒反应。通过合成与NEMO结合的NF-κB和TBK1 /IKKε激活的泛素链，TRAMO的E3连接酶活性对于NEMO激活是必需的。NEMO激活的IKKα/β通过IKKα/β介导的TBK1 /IKKε磷酸化对于TBK1 /IKKε激活很重要。此外，单个TRAFs在生理条件下以不同的方式介导了TBK1 /IKKε激活，因此微调了抗病毒免疫性。