Uncovering the Mechanism of Forkhead-Associated Domain-Mediated TIFA Oligomerization That Plays a Central Role in Immune Responses

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• 作者：Jui-Hung Weng ; Yin-Cheng Hsieh ; Chia-Chi Flora Huang ; Tong-You Wade Wei ; Liang-Hin Lim ; Yu-Hou Chen ; Meng-Ru Ho ; Iren Wang ; Kai-Fa Huang ; Chun-Jung Chen ; Ming-Daw Tsai
• 刊名：Biochemistry
• 出版年：2015
• 出版时间：October 13, 2015
• 年：2015
• 卷：54
• 期：40
• 页码：6219-6229
• 全文大小：818K
• ISSN：1520-4995

文摘

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-伪, TIFA is phosphorylated at Thr9, which triggers TIFA oligomerization via pThr9鈥揊HA domain binding and activates nuclear factor 魏B (NF-魏B). However, the structural mechanism for the functionally important TIFA oligomerization remains to be established. While FHA domain鈥損Thr 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鈥?50, with the unstructured C-terminal tail truncated) and its complex with the N-terminal pThr9 peptide (residues 1鈥?5), which show unique features in the FHA structure (intrinsic dimer and extra 尾-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鈥揊HA 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.