Takatsuna Hiroshi, Kato Hiroki, Gohda Jin, Akiyama Taishin, Moriya Ayaka, Okamoto Yoshinari, Yamagata Yuriko, Otsuka Masami, Umezawa Kazuo, Semba Kentaro, Inoue Jun-Ichiro
Division of Cellular and Molecular Biology, Department of Cancer Biology, The Institute of Medical Science, The University of Tokyo, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
J Biol Chem. 2003 Apr 4;278(14):12144-50. doi: 10.1074/jbc.M300720200. Epub 2003 Feb 3.
Tumor necrosis factor receptor-associated factor 6 (TRAF6) transduces signals from members of the Toll/interleukin-1 (IL-1) receptor family by interacting with IL-1 receptor-associated kinase-1 (IRAK-1) after IRAK-1 is released from the receptor-MyD88 complex upon IL-1 stimulation. However, the molecular mechanisms underlying regulation of the IRAK-1/TRAF6 interaction are largely unknown. We have identified TIFA, a TRAF-interacting protein with a forkhead-associated (FHA) domain. The FHA domain is a motif known to bind directly to phosphothreonine and phosphoserine. In transient transfection assays, TIFA activates NFkappaBeta and c-Jun amino-terminal kinase. However, TIFA carrying a mutation that abolishes TRAF6 binding or mutations in the FHA domain that are known to abolish FHA domain binding to phosphopeptide fails to activate NFkappaBeta and c-Jun amino-terminal kinase. TIFA, when overexpressed, binds both TRAF6 and IRAK-1 and significantly enhances the IRAK-1/TRAF6 interaction. Furthermore, analysis of endogenous proteins indicates that TIFA associates with TRAF6 constitutively, whereas it associates with IRAK-1 in an IL-1 stimulation-dependent manner in vivo. Thus, TIFA is likely to mediate IRAK-1/TRAF6 interaction upon IL-1 stimulation.
肿瘤坏死因子受体相关因子6（TRAF6）在白细胞介素-1（IL-1）刺激下，当白细胞介素-1受体相关激酶-1（IRAK-1）从受体-MyD88复合物中释放后，通过与IRAK-1相互作用，转导来自Toll/IL-1受体家族成员的信号。然而，IRAK-1/TRAF6相互作用调控的分子机制在很大程度上尚不清楚。我们鉴定出了TIFA，一种带有叉头相关（FHA）结构域的TRAF相互作用蛋白。FHA结构域是一种已知可直接结合磷酸苏氨酸和磷酸丝氨酸的基序。在瞬时转染实验中，TIFA激活核因子κB（NFκB）和c-Jun氨基末端激酶。然而，携带消除TRAF6结合的突变的TIFA或已知消除FHA结构域与磷酸肽结合的FHA结构域突变体无法激活NFκB和c-Jun氨基末端激酶。TIFA在过表达时，能结合TRAF6和IRAK-1，并显著增强IRAK-1/TRAF6的相互作用。此外，对内源蛋白的分析表明，TIFA在体内组成性地与TRAF6结合，而它与IRAK-1的结合则以IL-1刺激依赖的方式进行。因此,TIFA可能在IL-1刺激时介导IRAK-1/TRAF6的相互作用。
