白细胞介素-1诱导的肝细胞中核因子-κB-IκBα自调节反馈环。蛋白激酶Cα在IκBα再合成的转录后调控中的作用。

Interleukin-1-induced nuclear factor-kappaB-IkappaBalpha autoregulatory feedback loop in hepatocytes. A role for protein kinase calpha in post-transcriptional regulation of ikappabalpha resynthesis.

作者信息

Han Y, Meng T, Murray N R, Fields A P, Brasier A R

机构信息

Department of Internal Medicine, University of Texas Medical Branch, Galveston, Texas 77555-1060, USA.

出版信息

J Biol Chem. 1999 Jan 8;274(2):939-47. doi: 10.1074/jbc.274.2.939.

DOI:10.1074/jbc.274.2.939

PMID:9873035

Abstract

The IkappaB inhibitors regulate the activity of the potent transcription factor nuclear factor-kappaB (NF-kappaB). Following signal-induced IkappaB proteolysis, NF-kappaB translocates into the nucleus to activate transcription of target genes, including IkappaBalpha itself, initiating the "NF-kappaB-IkappaBalpha autoregulatory feedback loop." Upon IkappaBalpha resynthesis, NF-kappaB is subsequently inactivated and redistributed back into the cytoplasm. We have previously reported a robust NF-kappaB-IkappaBalpha autoregulatory feedback loop in HepG2 hepatocytes. Sixty minutes after tumor necrosis factor (TNF-alpha) stimulation, IkappaBalpha is resynthesized to approximately 2-fold greater level than in control cells and completely inhibits NF-kappaB binding. Here we investigate the mechanism for IkappaBalpha resynthesis comparing the effect of stimulation of TNF-alpha with that of interleukin-1 (IL-1alpha). Although either TNF-alpha or IL-1alpha stimulation of protein kinase C (PKC)-down-regulated cells equivalently induces NF-kappaB translocation, the kinetics of IkappaBalpha resynthesis is slowed. Moreover, pretreatment with selective calcium-dependent PKC inhibitors selectively slowed the kinetics of the IL-1alpha-induced overshoot without affecting that produced by TNF-alpha. Down-regulation of PKCalpha by antisense phosphorothioate oligonucleotides and expression vectors selectively blocked the IL-1alpha-induced IkappaBalpha overshoot. In the absence of PKCalpha, although IL-1alpha induced similar amounts of IkappaBalpha transcription and changes in steady-state mRNA, a greater component of IkappaBalpha mRNA was retained in the nucleus. These data indicate a selective role for PKCalpha in IL-1alpha-induced IkappaBalpha resynthesis, which is mediated, at least in part, by post-transcriptional control of mRNA export.

摘要

IκB 抑制剂可调节强效转录因子核因子-κB（NF-κB）的活性。在信号诱导的 IκB 蛋白水解后，NF-κB 转位进入细胞核以激活靶基因的转录，包括 IκBα 自身，从而启动“NF-κB-IκBα 自动调节反馈环”。IκBα 重新合成后，NF-κB 随后失活并重新分布回到细胞质中。我们之前报道过在 HepG2 肝细胞中存在强大的 NF-κB-IκBα 自动调节反馈环。肿瘤坏死因子（TNF-α）刺激 60 分钟后，IκBα 重新合成的水平比对照细胞高约 2 倍，并完全抑制 NF-κB 结合。在此我们研究 IκBα 重新合成的机制，比较 TNF-α 刺激与白细胞介素-1（IL-1α）刺激的效果。尽管对蛋白激酶 C（PKC）下调的细胞进行 TNF-α 或 IL-1α 刺激均可等效诱导 NF-κB 转位，但 IκBα 重新合成的动力学减慢。此外，用选择性钙依赖性 PKC 抑制剂预处理可选择性减慢 IL-1α 诱导的过冲动力学，而不影响 TNF-α 产生的过冲。用反义硫代磷酸酯寡核苷酸和表达载体下调 PKCα 可选择性阻断 IL-1α 诱导的 IκBα 过冲。在没有 PKCα 的情况下，尽管 IL-1α 诱导了相似量的 IκBα 转录以及稳态 mRNA 的变化，但更大比例的 IκBα mRNA 保留在细胞核中。这些数据表明 PKCα 在 IL-1α 诱导的 IκBα 重新合成中具有选择性作用，这至少部分是由 mRNA 输出的转录后控制介导的。