白介素-17(IL-17)是一個重要的促炎症細胞因子,由輔助性T細胞(Th17)及先天性免疫細胞等分泌,在多種炎性反應及自身免疫性疾病病理過程中發揮關鍵作用。IL-17受體(IL-17R)通過信號轉導複合體IL-17R-Act1-TRAF6激活下遊NF-kB、JNK等信號通路。然而,該信號通路的調控機制還有待深入闡明。博士生瞿芳芳,高漢超等在錢友存研究員的指導下研究發現IKK相關激酶(TBK1和IKKi)以冗餘方式直接磷酸化Act1,致使Act1與TRAF6的結合能力減弱,從而抑制IL-17誘導NF-kB激活。進一步研究發現,TRAF6通過介導TBK1的激活以及IKK相關激酶與Act1的相互作用,參與IL-17誘導的Act1的磷酸化;而TRAF3,作為抗病毒反應中IKK相關激酶的上遊的關鍵銜接蛋白,不參與IL-17誘導的ACT1磷酸化。該研究發現並闡明了IL-17激活NF-kB通路中新的調控機制,即Act1-TRAF6-TBK1/IKKi-Act1負反饋循環調控,為IL-17相關疾病治療提供了新的潛在靶點。
該項目得到了國家自然科學基金,國家科技部,中國科學院和上海市科委的資助。(生物谷Bioon.com)
TRAF6 dependent Act1 phosphorylation by the IKK-related kinases suppresses IL-17-induced NF-κB activation
Qu F, Gao H, Zhu S, Shi P, Zhang Y, Liu Y, Jallal B, Yao Y, Shi Y, Qian Y.
Interleukin 17 (IL-17) is critically involved in the pathogenesis of various inflammatory disorders. IL-17 receptor (IL-17R) proximal signaling complex (IL-17R-Act1-TRAF6) is essential for IL-17 mediated NF-κB activation while IL-17-mediated mRNA stability is TRAF6 independent. Recently, IKKi has been identified to phosphorylate Act1 on Ser 311 to mediate IL-17-induced mRNA stability. Here we show TBK1, the other IKK-related kinase, directly phosphorylated Act1 on three other Ser sites to suppress IL-17R mediated NF-κB activation. IL-17 stimulation activated TBK1 and induced its association with Act1. IKKi also phosphorylated Act1 on the three serine sites and played a redundant role with TBK1 in suppressing IL-17-induced NF-κB activation. Act1 phosphorylation on the three sites inhibited its association with TRAF6 and consequently NF-κB activation in IL-17R signaling. Interestingly, TRAF6 but not TRAF3 which is the upstream adaptor of the IKK related kinases in antiviral signaling, was critical for IL-17 induced Act1 phosphorylation. TRAF6 was essential for IL-17-induced TBK1 activation, its association with Act1, and consequent Act1 phosphorylation. Our findings define a new role for the IKK-related kinases in suppressing IL-17-mediated NF-κB activation through TRAF6 dependent Act1 phosphorylation