Uncovering the Mechanism of Forkhead-Associated Domain-Mediated TIFA Oligomerization That Plays a Central Role in Immune Responses
Uncovering the Mechanism of Forkhead-Associated Domain-Mediated TIFA Oligomerization That Plays a Central Role in Immune Responses
复制标题
DOI：
10.1021/acs.biochem.5b00500
复制
发表时间：
2015-10-13
期刊：
影响因子：
2.9
通讯作者：
Tsai, Ming-Daw
中科院分区：
文献类型：
--
作者：
Weng, Jui-Hung;Hsieh, Yin-Cheng;Tsai, Ming-Daw
叉头相关（FHA）结构域是唯一特异识别磷酸苏氨酸（pThr）的信号结构域。具有FHA结构域的TRAF相互作用蛋白（TIFA）通过与TRAF 2和TRAF 6结合参与免疫应答。我们最近报道了TIFA在溶液中是二聚体，并且在TNF-α刺激下，TIFA在Thr 9处磷酸化，这通过pThr 9-FHA结构域结合触发TIFA寡聚化并激活核因子KB（NF-κ B）。然而，功能重要的TIFA寡聚化的结构机制仍有待确定。虽然已知FHA结构域-pThr结合介导蛋白质二聚化，但其在寡聚化中的作用尚未在结构水平上得到证实。在这里，我们报告了TIFA的晶体结构（残基1-150，非结构化C-末端尾部截短）及其与N-末端pThr 9肽（残基1-15）的复合物，其在FHA结构（内在二聚体和额外的β链）及其与pThr肽（pThr之前而不是之后的残基）的相互作用中显示出独特的特征。这些结构特征支持先前的和额外的功能分析。此外，复合物的结构表明，pThr 9-FHA结构域的相互作用可以只发生在不同的二聚体之间，而不是在二聚体内的两个原聚体之间，提供了TIFA寡聚化的结构机制。我们的研究结果揭示了FHA结构域介导的寡聚化在免疫应答中的关键步骤的机制，并扩展了FHA结构域结构和功能的范式。
Forkhead-associated (FHA) domain is the only signaling domain that recognizes phosphothreonine (pThr) specifically. TRAF-interacting protein with an FHA domain (TIFA) was shown to be involved in immune responses by binding with TRAF2 and TRAF6. We recently reported that TIFA is a dimer in solution and that, upon stimulation by TNF-alpha, TIFA is phosphorylated at Thr9, which triggers TIFA oligomerization via pThr9-FHA domain binding and activates nuclear factor KB (NF-kappa B). However, the structural mechanism for the functionally important TIFA oligomerization remains to be established. While FHA domain-pThr binding is known to mediate protein dimerization, its role in oligomerization has not been demonstrated at the structural level. Here we report the crystal structures of TIFA (residues 1-150, with the unstructured C-terminal tail truncated) and its complex with the N-terminal pThr9 peptide (residues 1-15), which show unique features in the FHA structure (intrinsic dimer and extra beta-strand) and in its interaction with the pThr peptide (with residues preceding rather than following pThr). These structural features support previous and additional functional analyses. Furthermore, the structure of the complex suggests that the pThr9-FHA domain interaction can occur only between different sets of dimers rather than between the two protomers within a dimer, providing the structural mechanism for TIFA oligomerization. Our results uncover the mechanism of FHA domain-mediated oligomerization in a key step of immune responses and expand the paradigm of FHA domain structure and function.