MAVS activates TBK1 and IKKε through TRAFs in NEMO dependent and independent manner.
MAVS activates TBK1 and IKKε through TRAFs in NEMO dependent and independent manner.
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MAVS 通过 TRAF 以 NEMO 依赖和独立方式激活 TBK1 和 IKKε
DOI：
10.1371/journal.ppat.1006720
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发表时间：
2017-11
期刊：
影响因子：
6.7
通讯作者：
Jiang Z
中科院分区：
文献类型：
--
作者：
Fang R;Jiang Q;Zhou X;Wang C;Guan Y;Tao J;Xi J;Feng JM;Jiang Z
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，MAV激活下游成分，如Tbk1和IKKα/β的机制尚不清楚，尽管以前的工作表明NEMO或Tbk1结合蛋白TANK、NAP1和SINTABAD参与其中。在这里，我们报告了MAVS介导的天然免疫激活依赖于TRAF，部分依赖于NEMO，但不依赖于TBK1结合蛋白。MAVS通过TRAF与TbK1/IKKε的卷曲螺旋结构域直接相互作用而预先与Tbk1/IKKε结合的TRAF招募Tbk1/IKKε。TRAF_2、−/−_3、−/−_5、−/−_6、−/−细胞完全失去了病毒应答。TRAFS的E3连接酶活性是NEMO激活所必需的，它通过合成与NEMO结合的泛素链来激活NF-κB和Tbk1/IKKε。NEMO激活的IKKα/β通过IKKε介导的TbK1/IKKα/β磷酸化，对Tbk1/IKKε的激活起重要作用。此外，在生理条件下，不同的TRAF不同地介导了Tbk1/IKKε的激活，从而微调了抗病毒免疫。先天免疫是抵御病毒感染的第一道防线。RIG-I样受体识别RNA病毒中的各种病毒RNA，并启动宿主抗病毒反应，产生I型干扰素(IFN)和其他细胞因子。RLR通过共享一种称为线粒体抗病毒信号蛋白(MAV)的共同适配器蛋白来感知不同类型的病毒。虽然RLRs在病毒感染后如何招募和激活MAV已经有了很好的研究，但MAV是如何激活其下游成分的，包括Tbk1/IKKε和IKK复合体，仍有待阐明。在这里，通过使用TRAF_2−/−_−/−_−/−、TRAF_2_−/−_3_−/−_5_−/−_6_−/−和TRAF_2_−/−_3_−/−_5_−/−_6_−/−_nemo_−/−_293T细胞，结合重组实验，我们发现MAV通过预先结合的TRAF_TRAF-TbK_1/IKK_ε复合体通过TRAF来募集TRAF_1/IKK_ε。Tbk1/IKKε的激活既需要TRAFS介导的Tbk1自身磷酸化，也需要TRAFS-NEMO-IKKβ介导的Tbk1磷酸化。我们证明了TRAFS的E3连接酶活性仅是NEMO和IKKα/β激活所必需的。IKKα/β对Tbk1和NF-κB的激活均起关键作用。我们的结果表明，MAVS通过TRAF以NEMO依赖和非依赖的方式激活Tbk1/ikkε。重要的是，在病毒感染过程中，极少量的IFN的产生独立于NF-κB的激活，并且不同的TRAF以不同的方式介导Tbk1/IKKε的激活，从而微调生理条件下的抗病毒免疫。
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. Innate immunity is the first line of defense against virus infection. RIG-I-like receptors (RLRs) recognize various viral RNA from RNA viruses and initiate host antiviral responses to produce type I interferons (IFNs) and other cytokines. RLRs sense distinct types of viruses by sharing a common adaptor protein called mitochondrial antiviral-signaling protein (MAVS). Although it has been well studied how RLRs recruit and activate MAVS upon virus infection, it remains to be elucidated how MAVS activates its downstream components, including kinases TBK1/IKKε and the IKK complex. Here, by using TANK−/−NAP1−/−SINTBAD−/−, TRAF2−/−3−/−5−/−6−/− and TRAF2−/−3−/−5−/−6−/−NEMO−/− 293T cells combined with reconstitution experiments, we discovered that MAVS recruited TBK1/IKKε via TRAFs through pre-associated TRAFs-TBK1/IKKε complex. TBK1/IKKε activation required both TRAFs-mediated TBK1 autophosphorylation and TRAFs-NEMO-IKKβ-mediated TBK1 phosphorylation. We demonstrated that TRAFs’ E3 ligase activity was solely required for NEMO and IKKα/β activation. IKKα/β were crucial for both TBK1 and NF-κB activation. Our results thus demonstrated that MAVS activates TBK1/IKKε through TRAFs in both NEMO-dependent and independent manner. Importantly, a minimal amount of IFNs was produced independent of NF-κB activation during virus infection and that individual TRAFs differently mediated TBK1/IKKε activation, thus fine-tuned antiviral immunity under physiological conditions.
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影响因子：
64.8
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