MRC Protein Phosphorylation Unit, College of Life Sciences, Sir James Black Centre, University of Dundee, Dundee, Scotland, U.K.
Biochem J. 2011 Feb 15;434(1):93-104. doi: 10.1042/BJ20101701.
Members of the IKK {IκB [inhibitor of NF-κB (nuclear factor κB)] kinase} family play a central role in innate immunity by inducing NF-κB- and IRF [IFN (interferon) regulatory factor]-dependent gene transcription programmes required for the production of pro-inflammatory cytokines and IFNs. However, the molecular mechanisms that activate these protein kinases and their complement of physiological substrates remain poorly defined. Using MRT67307, a novel inhibitor of IKKϵ/TBK1 (TANK {TRAF [TNF (tumour-necrosis-factor)-receptor-associated factor]-associated NF-κB activator}-binding kinase 1) and BI605906, a novel inhibitor of IKKβ, we demonstrate that two different signalling pathways participate in the activation of the IKK-related protein kinases by ligands that activate the IL-1 (interleukin-1), TLR (Toll-like receptor) 3 and TLR4 receptors. One signalling pathway is mediated by the canonical IKKs, which directly phosphorylate and activate IKKϵ and TBK1, whereas the second pathway appears to culminate in the autocatalytic activation of the IKK-related kinases. In contrast, the TNFα-induced activation of the IKK-related kinases is mediated solely by the canonical IKKs. In turn, the IKK-related kinases phosphorylate the catalytic subunits of the canonical IKKs and their regulatory subunit NEMO (NF-κB essential modulator), which is associated with reduced IKKα/β activity and NF-κB-dependent gene transcription. We also show that the canonical IKKs and the IKK-related kinases not only have unique physiological substrates, such as IκBα, p105, RelA (IKKα and IKKβ) and IRF3 (IKKϵ and TBK1), but also have several substrates in common, including the catalytic and regulatory (NEMO and TANK) subunits of the IKKs themselves. Taken together, our studies reveal that the canonical IKKs and the IKK-related kinases regulate each other by an intricate network involving phosphorylation of their catalytic and regulatory (NEMO and TANK) subunits to balance their activities during innate immunity.
IKK{IκB [NF-κB（核因子κB）抑制剂]激酶}家族成员通过诱导 NF-κB 和 IRF[IFN（干扰素）调节因子]依赖性基因转录程序，在先天免疫中发挥核心作用，这些程序是产生促炎细胞因子和 IFNs 所必需的。然而，激活这些蛋白激酶及其生理底物的分子机制仍未得到很好的定义。使用新型 IKKϵ/TBK1（TANK[TRAF（肿瘤坏死因子-受体相关因子）相关 NF-κB 激活剂]结合激酶 1）抑制剂 MRT67307 和新型 IKKβ抑制剂 BI605906，我们证明两条不同的信号通路参与了配体激活 IL-1（白细胞介素-1）、TLR（Toll 样受体）3 和 TLR4 受体后，IKK 相关蛋白激酶的激活。一种信号通路是由经典的 IKK 介导的，它直接磷酸化并激活 IKKϵ和 TBK1，而第二种通路似乎最终导致 IKK 相关激酶的自催化激活。相比之下，TNFα 诱导的 IKK 相关激酶的激活仅由经典的 IKK 介导。反过来，IKK 相关激酶磷酸化经典 IKK 的催化亚基及其调节亚基 NEMO（NF-κB 必需调节剂），这与 IKKα/β 活性降低和 NF-κB 依赖性基因转录减少有关。我们还表明，经典的 IKK 和 IKK 相关激酶不仅具有独特的生理底物，如 IκBα、p105、RelA（IKKα 和 IKKβ）和 IRF3（IKKϵ 和 TBK1），而且还具有几个共同的底物，包括 IKK 本身的催化和调节（NEMO 和 TANK）亚基。总之，我们的研究揭示了经典的 IKK 和 IKK 相关激酶通过涉及它们的催化和调节（NEMO 和 TANK）亚基磷酸化的复杂网络相互调节，以在先天免疫过程中平衡它们的活性。
