Activation of the heterodimeric IκB kinase α (IKKα)-IKKβ complex is directional:: IKKα regulates IKKβ under both basal and stimulated conditions
Activation of the heterodimeric IκB kinase α (IKKα)-IKKβ complex is directional:: IKKα regulates IKKβ under both basal and stimulated conditions
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DOI：
10.1128/mcb.20.4.1170-1178.2000
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发表时间：
2000-02-01
影响因子：
5.3
通讯作者：
Greene, WC
中科院分区：
文献类型：
--
作者：
O'Mahony, A;Lin, X;Greene, WC
真核生物nf - κ B转录因子的信号诱导核表达涉及选择有丝分裂原激活的蛋白激酶激酶激酶激酶对IKK α和IKK β激酶的刺激作用，IKK α和IKK β激酶位于称为信号体的大分子信号复合体中。虽然遗传学研究表明IKK β是参与促炎细胞因子诱导的I κ B磷酸化的主要激酶，但同等表达的IKK α的功能尚不清楚。在这里，我们证明了IKK α与IKK β在异二聚体信号体中的组装有两个重要功能：(i)在未受刺激的细胞中，IKK α抑制IKK β的组成i κ B激酶活性；（ii）在活化细胞中，IKK α激酶活性是诱导IKK β的必要条件。将激酶失活的IKK α、IKK α激活环突变体或IKK α反义RNA引入293或HeLa细胞，可阻断NIK （nf - κ b诱导激酶）诱导的IKK β激活环磷酸化，这些磷酸化发生在功能信号体中。相反，IKK β的催化失活突变体不会阻断这些大分子信号复合物中ik介导的IKK α磷酸化。在其他nf - κ B诱导剂（包括肿瘤坏死因子α、人t细胞白血病病毒1型Tax、Cot和MEKK1）中，也观察到这种需要精通激酶的IKK α来激活异二聚体IKK信号体中的IKK β。相反，同样诱导NF-kappa B/Rel的蛋白激酶C的θ亚型直接针对IKK β进行磷酸化和激活，可能通过同型二聚体IKK β复合物起作用。总之，我们的研究结果表明，各种不同的诱导剂对异二聚体IKK复合物的激活以定向方式进行，并且依赖于IKK α的激酶活性来激活IKK β。
Signal-induced nuclear expression of the eukaryotic NF-kappa B transcription factor involves the stimulatory action of select mitogen-activated protein kinase kinase kinases on the I kappa B kinases (IKK alpha and IKK beta) which reside in a macromolecular signaling complex termed the signalsome. While genetic studies indicate that IKK beta is the principal kinase involved in proinflammatory cytokine-induced I kappa B phosphorylation, the function of the equivalently expressed IKK alpha is less clear. Here we demonstrate that assembly of IKK alpha with IKK beta in the heterodimeric signalsome serves two important functions: (i) in unstimulated cells, IKK alpha inhibits the constitutive I kappa B kinase activity of IKK beta; (ii) in activated cells, IKK alpha kinase activity is required for the induction of IKK beta. The introduction of kinase-inactive IKK alpha, activation loop mutants of IKK alpha, or IKK alpha antisense RNA into 293 or HeLa cells blocks NIK (NF-kappa B-inducing kinase)-induced phosphorylation of the IKK beta activation loop occurring in functional signalsomes. In contrast, catalytically inactive mutants of IKK beta do not block NIK-mediated phosphorylation of IKK alpha in these macromolecular signaling complexes. This requirement for kinase-proficient IKK alpha to activate IKK beta in heterodimeric IKK signalsomes is also observed with other NF-kappa B inducers, including tumor necrosis factor alpha, human T-cell leukemia virus type 1 Tax, Cot, and MEKK1. Conversely, the theta isoform of protein kinase C, which also induces NF-kappa B/Rel, directly targets IKK beta for phosphorylation and activation, possibly acting through homodimeric IKK beta complexes. Together, our findings indicate that activation of the heterodimeric IKK complex by a variety of different inducers proceeds in a directional manner and is dependent on the kinase activity of IKK alpha to activate IKK beta.