Removing Ubiquitin to Regulate NF-κB Activity
Removing Ubiquitin to Regulate NF-κB Activity
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去除泛素以调节 NF-κB 活性
DOI：
10.1126/stke.3792007tw102
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
Naumann M
中科院分区：
文献类型：
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作者：
Schweitzer K;Bozko PM;Dubiel W;Naumann M
作为负反馈机制的一部分，转录因子核因子κ B（NF-κB）诱导I κBα转录，恢复细胞中其负调节因子IκBα的量。然而，功能性IκBα的快速恢复意味着即使在IκB激酶β（IKKβ）磷酸化的情况下，也存在其他稳定IκBα的机制。该事件导致IκBα的泛素化，靶向其进行蛋白酶体降解并导致活性NF-κB的释放。Schweitzeret等人发现了COP 9信号体（CSN）在这一过程中发挥的关键作用。CSN是一个由8个亚基组成的蛋白复合体，控制着多亚基cullin-RING泛素连接酶（CRL）的活性，其中SCFβTrCP可使IκBα泛素化。作者进行了免疫共沉淀研究，确定了用肿瘤坏死因子-α（TNF-α）处理转染的HeLa细胞后，CSN 2与IκBα相关。通过免疫共沉淀和电泳迁移率变动分析，以及小干扰RNA（siRNA）敲低CSN 2，作者表明，与对照细胞相比，用TNF-α处理后，CSN 2缺陷细胞中IκBα的恢复大大降低。在CSN 2缺陷的细胞中也观察到泛素化IκBα的早期积累和增加量。CSN复合物的一个组分是USP 15，一种去泛素化酶（DUB）。与对照细胞相比，转染USP 15特异性siRNA的HeLa细胞在TNF-α刺激降解后显示IκBα的恢复减少。体外DU B测定，使用泛素化IκBα作为底物，证明纯化的CSN和USP 15都去泛素化IκBα。总之，这些数据证明了CSN通过稳定IκB激酶在调节NF-κB活性中的一种以前未知的作用。Schweitzer，P. M.博兹科湾Dubiel，M. Naumann，CSN controls the NF-κB by deubiquitinylation of IκBα.EMBO J.26，1532-1541（2007）. [PubMed]
As part of a negative feedback mechanism, the transcription factor nuclear factor κΒ (NF-κB) inducesIκBαtranscription, restoring the amount of its negative regulator, IκBα, in the cell. However, the rapidity with which functional IκBα recovers implies the existence of other mechanisms to stabilize IκBα, even in the face of phosphorylation by IκB kinase β (IKKβ). This event leads to ubiquitinylation of IκBα, targeting it for proteasomal degradation and resulting in the release of active NF-κB. Schweitzeret al. have uncovered the crucial role that the COP9 signalosome (CSN) plays in this process. CSN is an eight-subunit (CSN1-8) protein complex that controls the activities of multisubunit cullin-RING ubiquitin ligases (CRLs), one member of which, SCFβTrCP, ubiquitinylates IκBα. The authors performed coimmunoprecipitation studies that established that CSN2 associated with IκBα after treatment of transfected HeLa cells with tumor necrosis factor-α (TNF-α). Through coimmunoprecipitation and electrophoretic mobility shift assays, and knockdown of CSN2 by small interfering RNA (siRNA), the authors showed that the recovery in IκBα after treatment with TNF-α was much reduced in CSN2-deficient cells compared with control cells. Earlier accumulation and enhanced amounts of ubiquitinylated IκBα were also seen in cells deficient in CSN2. One component of the CSN complex is USP15, a deubiquitinylase (DUB). HeLa cells transfected with a USP15-specific siRNA showed reduced recovery of IκBα after TNF-α-stimulated degradation compared with control cells. In vitro DUB assays, using ubiquitinylated IκBα as a substrate, demonstrated that both purified CSN and USP15 deubiquitinylated IκBα. Together, these data demonstrate a previously unknown role for CSN in regulating NF-κB activity through the stabilization of IκBα.K. Schweitzer, P. M. Bozko, W. Dubiel, M. Naumann, CSN controls NF-κB by deubiquitinylation of IκBα.EMBO J.26, 1532-1541 (2007). [PubMed]