Suppression of p65 phosphorylation coincides with inhibition of IκBα polyubiquitination and degradation
Suppression of p65 phosphorylation coincides with inhibition of IκBα polyubiquitination and degradation
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DOI：
10.1002/mc.20142
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发表时间：
2005-12-01
影响因子：
4.6
通讯作者：
Colburn, NH
中科院分区：
文献类型：
--
作者：
Hu, J;Haseebuddin, M;Colburn, NH
转录因子核因子-κ B（NF-κ B）通过I κ B抑制剂以非活性状态保持在细胞质中。NF-κ B的致癌激活通过刺激诱导的泛素化和随后的I κ B α的蛋白酶体介导的降解来实现。一旦从抑制剂释放，NF-κ B/p65进入细胞核。精氨酸诱导的I κ B α泛素化和降解的先决条件是I κ B α在S32/S36的磷酸化。然而，单独的I κ B α磷酸化不足以触发其降解，这表明调节I κ B α降解必须需要其他事件。在这项研究中，我们测试的假设，磷酸化p65在536所需的TNF-α。诱导I κ B α蛋白水解，进而控制p65核转位。我们观察到，在不影响I κ B α磷酸化的情况下，MEK 1抑制剂U 0126处理不仅抑制p65-S536磷酸化，而且抑制TNF-α诱导的I κ B α的多泛素化，从而抑制I κ B α降解。用p65 S536磷酸化突变体和模拟物，我们进一步观察到p65丝氨酸536到丙氨酸的结构突变抑制了泛素向含p65复合物的募集。作为抑制含p65复合物的多聚泛素化的结果，p65磷酸化突变体结合的I κ B α的降解也被抑制。因此，磷酸化受损的p65的核转位显著减少。这些发现表明，p65磷酸化在刺激诱导的I κ B α泛素化中起着关键作用。2005年出版Wiley-Liss，Inc.（匕首）
Transcription factor nuclear factor-kappa B (NF-kappa B) is held in the cytoplasm in an inactive state by I kappa B inhibitors Oncogenic activation of NF-kappa B is achieved by stimulus-induced ubiquitination and subsequent proteasome-mediated degradation of I kappa B alpha. Once released from the inhibitor, NF-kappa B/p65 enters the nucleus. A pre-requisite for cytokine-induced I kappa B alpha ubiquitination and degradation is the phosphorylation Of I kappa B alpha at S32/S36. Phosphorylation Of I kappa B alpha alone, however, is not sufficient to trigger its degradation, suggesting other events must be required for regulating I kappa B alpha degradation. In this study, we tested the hypothesis that phosphorylation of p65 at 536 is required for TNF-alpha. induced I kappa B alpha proteolysis that in turn controls p65 nuclear translocation. We observed that, without affecting I kappa B alpha phosphorylation, MEK1 inhibitor U0126 treatment inhibited not only p65-S536 phosphorylation but also TNF-alpha-induced polyubiquitination Of I kappa B alpha thereby inhibiting I kappa B alpha degradation. With p65 S536 phosphorylation mutants and mimics, we further observed that the structural mutation of p65 serine 536 to alanine inhibited the recruitment of ubiquitin to the p65-containing complex. As a consequence of suppressing polyubiquitination of the p65-containing complex, degradation of p65 phosphorylation mutant-bound I kappa B alpha was also inhibited. Accordingly, the nuclear translocation of phosphorylation-impaired p65 was significantly reduced. These findings suggest that p65 phosphorylation plays a key role in stimulus-induced I kappa B alpha ubiquitination. Published 2005 Wiley-Liss, Inc.(dagger)