Activation of MTK1/MEKK4 by GADD45 through induced N-C dissociation and dimerization-mediated trans autophosphorylation of the MTK1 kinase domain
Activation of MTK1/MEKK4 by GADD45 through induced N-C dissociation and dimerization-mediated trans autophosphorylation of the MTK1 kinase domain
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DOI：
10.1128/mcb.01435-06
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发表时间：
2007-04-01
影响因子：
5.3
通讯作者：
Saito, Haruo
中科院分区：
文献类型：
--
作者：
Miyake, Zenshi;Takekawa, Mutsuhiro;Saito, Haruo
丝裂原活化蛋白激酶（MAPK）模块由MAPK、MAPK激酶（MAPKK）和MAPKK激酶（MAPKKK）组成，是在整个真核世界中保守的细胞信号传导装置。在哺乳动物细胞中，各种细胞外应激激活MAPK的两个主要亚家族，即Jun N-末端激酶和p38/应激激活的MAPK（SAPK）。MTK 1（也称为MEKK 4）是一种应激反应性MAPKKK，与应激诱导型GADD 45蛋白家族（GADD 45 α/β/γ）结合并被其激活。在这里，我们剖析了GADD 45蛋白激活MTK 1的分子机制。MTK 1的N末端与其C末端片段结合，从而抑制C末端激酶结构域。这种N-C相互作用被GADD 45与MTK 1 N-末端GADD 45结合位点的结合破坏。GADD 45结合还通过含有卷曲螺旋基序的二聚化结构域诱导MTK 1二聚化，所述卷曲螺旋基序对于MTK 1在激酶活化环中的Thr-1493处的反式自磷酸化是必需的。在Thr-1493处的MTK 1丙氨酸取代突变体具有严重降低的活性。因此，我们得出结论，GADD 45结合诱导MTK 1 N-C解离，二聚化，和自磷酸化的Thr-1493，导致激活的激酶催化结构域。组成型活性MTK 1突变体诱导相同的事件，但在GADD 45的情况下。
The mitogen-activated protein kinase (MAPK) module, composed of a MAPK, a MAPK kinase (MAPKK), and a MAPKK kinase (MAPKKK), is a cellular signaling device that is conserved throughout the eukaryotic world. In mammalian cells, various extracellular stresses activate two major subfamilies of MAPKs, namely, the Jun N-terminal kinases and the p38/stress-activated MAPK (SAPK). MTK1 (also called MEKK4) is a stress-responsive MAPKKK that is bound to and activated by the stress-inducible GADD45 family of proteins (GADD45 alpha/beta/gamma). Here, we dissected the molecular mechanism of MTK1 activation by GADD45 proteins. The MTK1 N terminus bound to its C-terminal segment, thereby inhibiting the C-terminal kinase domain. This N-C interaction was disrupted by the binding of GADD45 to the MTK1 N-terminal GADD45-binding site. GADD45 binding also induced MTK1 dimerization via a dimerization domain containing a coiled-coil motif, which is essential for the trans autophosphorylation of MTK1 at Thr-1493 in the kinase activation loop. An MTK1 alanine substitution mutant at Thr-1493 has a severely reduced activity. Thus, we conclude that GADD45 binding induces MTK1 N-C dissociation, dimerization, and autophosphorylation at Thr-1493, leading to the activation of the kinase catalytic domain. Constitutively active MTK1 mutants induced the same events, but in the absence of GADD45.