RelA/p65 regulation of IκBβ
RelA/p65 regulation of IκBβ
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DOI：
10.1128/mcb.25.12.4956-4968.2005
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发表时间：
2005-06-01
影响因子：
5.3
通讯作者：
Guttridge, DC
中科院分区：
文献类型：
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作者：
Hertlein, E;Wang, JX;Guttridge, DC
I kappa B抑制蛋白是NF-kappa B的主要调节蛋白，与NF-kappa B和I kappa B kappa之间明确的调控相互作用相反，关于NF-kappa B对I kappa Bβ的调节知之甚少。使用p65(-/-)成纤维细胞，我们发现I-kappa Bβ在这些细胞中显著减少，但在其他核因子-kappa B亚单位敲除中没有。这一调节在胚胎和出生后发育期间以组织特有的方式盛行。值得注意的是，在p65(-/-)细胞和组织中，I kappa Bα也减少，但程度不同于I kappa Bβ，从而突显了I kappa Bβ对p65的依赖程度。这种依赖性是基于p65从26S蛋白酶体稳定I kappa Bβ蛋白的能力，这一过程在很大程度上是通过p65羧基末端介导的。此外，发现I kappa Bβ以碱性磷酸化和过度磷酸化的形式存在。虽然过度磷酸化的形式不那么丰富，但它也更稳定，对p65及其羧基结构域的依赖更少。最后，我们发现在p65(-/-)成纤维细胞中，表达一种蛋白分解抗性形式的I kappa Bβ，而不是I kappa Bα，会导致与凋亡相关的严重生长缺陷。基于这些发现，我们认为p65对I kappa Bβ蛋白的严格控制对于维持细胞内环境的稳定是必要的。
I kappa B inhibitor proteins are the primary regulators of NF-kappa B. In contrast to the defined regulatory interplay between NF-kappa B and I kappa B kappa, much less is known regarding the regulation of I kappa B beta by NF-kappa B. Here, we describe in detail the regulation of I kappa B beta by RelA/p65. Using p65(-/-) fibroblasts, we show that I kappa B beta is profoundly reduced in these cells, but not in other NF-kappa B subunit knockouts. This regulation prevails during embryonic and postnatal development in a tissue-specific manner. Significantly, in both p65(-/-) cells and tissues, I kappa B alpha is also reduced, but not nearly to the same extent as I kappa B beta, thus highlighting the degree to which I kappa B beta is dependent on p65. This dependence is based on the ability of p65 to stabilize I kappa B beta protein from the 26S proteasome, a process mediated in large part through the p65 carboxyl terminus. Furthermore, I kappa B beta was found to exist in both a basally phosphorylated and a hyperphosphorylated form. While the hyperphosphorylated form is less abundant, it is also more stable and less dependent on p65 and its carboxyl domain. Finally, we show that in p65(-/-) fibroblasts, expression of a proteolysis-resistant form of I kappa B beta, but not I kappa B alpha, causes a severe growth defect associated with apoptosis. Based on these findings, we propose that tight control of I kappa B beta protein by p65 is necessary for the maintenance of cellular homeostasis.