Medical School and Model Animal Research Center of Nanjing University, Nanjing 210093, China.
Department of Physiology and Biophysics, University of California, Irvine, California 92697, Unites States.
J Proteome Res. 2020 Mar 6;19(3):1119-1130. doi: 10.1021/acs.jproteome.9b00626. Epub 2020 Feb 3.
The COP9 signalosome (CSN) is an evolutionarily conserved multisubunit protein complex, which controls protein degradation through deneddylation and inactivation of cullin-RING ubiquitin E3 ligases (CRLs). Recently, the CSN complex has been linked to the NF-κB signaling pathway due to its association with the IKK complex. However, how the CSN complex is regulated in this signaling pathway remains unclear. Here, we have carried out biochemical experiments and confirmed the interaction between the CSN and IKK complexes. In addition, we have determined that overexpression of IKKα or IKKβ leads to enhanced phosphorylation of CSN5, the catalytic subunit for CSN deneddylase activity. Mutational analyses have revealed that phosphorylation at serine 201 and threonine 205 of CSN5 impairs CSN-mediated deneddylation activity in vitro. Interestingly, TNF-α treatment not only enhances the interaction between CSN and IKK but also induces an IKK-dependent phosphorylation of CSN5 at serine 201, linking CSN to TNF-α signaling through IKK. Moreover, TNF-α treatment affects the CSN interaction network globally, especially the associations of CSN with the proteasome complex, eukaryotic translation initiation factor complex, and CRL components. Collectively, our results provide new insights into IKK-mediated regulation of CSN associated with the NF-κB signaling pathway.
COP9 信号体（CSN）是一种进化上保守的多亚基蛋白复合物，通过去泛素化和失活 Cullin-RING 泛素 E3 连接酶（CRLs）来控制蛋白质降解。最近，由于 CSN 复合物与 IKK 复合物的关联，CSN 复合物与 NF-κB 信号通路有关。然而，CSN 复合物在这条信号通路中是如何被调控的仍然不清楚。在这里，我们进行了生化实验并证实了 CSN 复合物和 IKK 复合物之间的相互作用。此外，我们确定了 IKKα 或 IKKβ 的过表达导致 CSN5 的磷酸化增强，CSN5 是 CSN 去泛素化活性的催化亚基。突变分析表明 CSN5 的丝氨酸 201 和苏氨酸 205 的磷酸化会损害 CSN 介导的体外去泛素化活性。有趣的是，TNF-α 处理不仅增强了 CSN 和 IKK 之间的相互作用，而且还诱导 CSN5 的丝氨酸 201 上的 IKK 依赖性磷酸化，通过 IKK 将 CSN 与 TNF-α 信号联系起来。此外，TNF-α 处理会全局影响 CSN 相互作用网络，特别是 CSN 与蛋白酶体复合物、真核翻译起始因子复合物和 CRL 成分的关联。总之，我们的结果为 IKK 介导的与 NF-κB 信号通路相关的 CSN 调控提供了新的见解。
