A Molecular Mechanism for Toll-IL-1 Receptor Domain-containing Adaptor Molecule-1-mediated IRF-3 Activation*
A Molecular Mechanism for Toll-IL-1 Receptor Domain-containing Adaptor Molecule-1-mediated IRF-3 Activation*
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DOI：
10.1074/jbc.m109.099101
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发表时间：
2010-04
期刊：
影响因子：
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通讯作者：
Megumi Tatematsu;A. Ishii;H. Oshiumi;M. Horiuchi;F. Inagaki;T. Seya;M. Matsumoto
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文献类型：
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作者：
Megumi Tatematsu;A. Ishii;H. Oshiumi;M. Horiuchi;F. Inagaki;T. Seya;M. Matsumoto
含有 Toll-IL-1 受体 (TIR) 结构域的接头分子 1 (TICAM-1，也称为 TRIF) 是 TLR3 和 TLR4 的信号传导接头，可激活转录因子 IRF-3、NF-κB 和 AP-1，从而诱导 I 型干扰素和细胞因子的产生。 TICAM-1 的 N 端区域参与 IRF-3 激活，而 C 端区域参与 NF-κB 激活。然而，TICAM-1 被激活并传输信号的机制在很大程度上尚不清楚。在这项研究中，我们确定 Leu194 是 TICAM-1 介导的 IRF-3 激活的关键氨基酸。当 Leu194 被 Ala 取代时，突变体 TICAM-1 未能招募 IRF-3 激酶 TBK1，导致 IRF-3 磷酸化缺失，尽管 TRAF3 和 NAP1 似乎被招募。 TICAM-1的N端176个氨基酸（N端结构域（NTD））形成一个蛋白酶抗性结构域。缺乏 N 端 180 个氨基酸的 TICAM-1 突变体显示出比野生型 TICAM-1 更强的干扰素-β 启动子激活。此外，免疫沉淀和蛋白质-蛋白质相互作用分析表明 NTD 与 TICAM-1-TIR 的 N 末端相互作用。这些结果表明 NTD 折叠到 TIR 结构域结构中以维持 TICAM-1 的原始构象。刺激 TLR3/4 后，TICAM-1 通过 TIR 结构域和 C 末端区域寡聚化，这可能会破坏分子内缔合并诱导构象变化，使 TBK1 能够接触 TICAM-1。
The Toll-IL-1 receptor (TIR) domain-containing adaptor molecule-1 (TICAM-1, also called TRIF) is a signaling adaptor for TLR3 and TLR4 that activates the transcription factors IRF-3, NF-κB, and AP-1, leading to induction of type I interferon and cytokines. The N-terminal region of TICAM-1 participates in IRF-3 activation, although the C-terminal region is involved in NF-κB activation. However, the mechanism by which TICAM-1 is activated and transmits signals is largely unknown. In this study, we identified Leu194 as a critical amino acid for TICAM-1-mediated IRF-3 activation. When Leu194 was substituted with Ala, the mutant TICAM-1 failed to recruit the IRF-3 kinase TBK1, resulting in lack of IRF-3 phosphorylation, although TRAF3 and NAP1 appeared to be recruited. The N-terminal 176 amino acids of TICAM-1 (N-terminal domain (NTD)) form a protease-resistant structural domain. A TICAM-1 mutant lacking the N-terminal 180 amino acids showed greater interferon-β promoter activation than wild-type TICAM-1. Furthermore, immunoprecipitation and protein-protein interaction analysis revealed that the NTD interacted with the N terminus of TICAM-1-TIR. These results suggest that the NTD folds into the TIR domain structure to maintain the naive conformation of TICAM-1. Upon stimulation of TLR3/4, TICAM-1 oligomerizes through the TIR domain and the C-terminal region, which may break the intramolecular association and induce a conformational change that allows TBK1 access to TICAM-1.