当前位置: X-MOL 学术Front. Immunol. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Cullin-5 Adaptor SPSB1 Controls NF-κB Activation Downstream of Multiple Signaling Pathways.
Frontiers in Immunology ( IF 7.3 ) Pub Date : 2020-01-21 , DOI: 10.3389/fimmu.2019.03121
Iliana Georgana 1 , Carlos Maluquer de Motes 1
Affiliation  

The initiation of innate immune responses against pathogens relies on the activation of pattern-recognition receptors (PRRs) and corresponding intracellular signaling cascades. To avoid inappropriate or excessive activation of PRRs, these responses are tightly controlled. Cullin-RING E3 ubiquitin ligases (CRLs) have emerged as critical regulators of many cellular functions including innate immune activation and inflammation. CRLs form multiprotein complexes in which a Cullin protein acts as a scaffold and recruits specific adaptor proteins, which in turn recognize specific substrate proteins for ubiquitylation, hence providing selectivity. CRLs are divided into 5 main groups, each of which uses a specific group of adaptor proteins. Here, we systematically depleted all predicted substrate adaptors for the CRL5 family (the so-called SOCS-box proteins) and assessed the impact on the activation of the inflammatory transcription factor NF-κB. Depletion of SPSB1 resulted in a significant increase in NF-κB activation, indicating the importance of SPSB1 as an NF-κB negative regulator. In agreement, overexpression of SPSB1 suppressed NF-κB activity in a potent, dose-dependent manner in response to various agonists. Inhibition by SPSB1 was specific to NF-κB, because other transcription factors related to innate immunity and interferon (IFN) responses such as IRF-3, AP-1, and STATs remained unaffected by SPSB1. SPSB1 suppressed NF-κB activation induced via multiple pathways including Toll-like receptors and RNA and DNA sensing adaptors, and required the presence of its SOCS-box domain. To provide mechanistic insight, we examined phosphorylation and degradation of the inhibitor of κB (IκBα) and p65 translocation into the nucleus. Both remained unaffected by SPSB1, indicating that SPSB1 exerts its inhibitory activity downstream, or at the level, of the NF-κB heterodimer. In agreement with this, SPSB1 was found to co-precipitate with p65 after over-expression and at endogenous levels. Additionally, A549 cells stably expressing SPSB1 presented lower cytokine levels including type I IFN in response to cytokine stimulation and virus infection. Taken together, our results reveal novel regulatory mechanisms in innate immune signaling and identify the prominent role of SPSB1 in limiting NF-κB activation. Our work thus provides insights into inflammation and inflammatory diseases and new opportunities for the therapeutic targeting of NF-κB transcriptional activity.

中文翻译:

Cullin-5适配器SPSB1控制多个信号通路下游的NF-κB激活。

针对病原体的先天免疫应答的启动依赖于模式识别受体(PRR)和相应的细胞内信号传导级联的激活。为了避免不适当或过度激活PRR,必须严格控制这些响应。Cullin-ring E3泛素连接酶(CRL)已成为许多细胞功能(包括先天性免疫激活和炎症)的关键调节剂。CRL形成多蛋白复合物,其中Cullin蛋白充当支架并募集特定的衔接子蛋白,后者又识别特定的底物蛋白进行泛素化,从而提供了选择性。CRL分为5个主要组,每个组使用特定的衔接子蛋白组。这里,我们系统地消耗了CRL5家族的所有预测底物衔接子(所谓的SOCS-box蛋白),并评估了对炎症转录因子NF-κB活化的影响。SPSB1的耗尽导致NF-κB激活的显着增加,表明SPSB1作为NF-κB负调节剂的重要性。一致地,SPSB1的过表达以有效的,剂量依赖性的方式抑制了各种激动剂,从而抑制了NF-κB的活性。SPSB1的抑制对NF-κB具有特异性,因为与先天免疫和干扰素(IFN)反应相关的其他转录因子(例如IRF-3,AP-1和STATs)仍然不受SPSB1的影响。SPSB1抑制了通过多种途径诱导的NF-κB激活,这些途径包括Toll样受体以及RNA和DNA感应衔接子,并且需要存在其SOCS-box域。为了提供机理上的见解,我们研究了κB抑制剂(IκBα)的磷酸化和降解以及p65易位到核中。两者均不受SPSB1的影响,表明SPSB1在NF-κB异二聚体的下游或水平发挥其抑制活性。与此相符的是,发现SPSB1在过度表达后和内源水平与p65共沉淀。另外,响应于细胞因子刺激和病毒感染,稳定表达SPSB1的A549细胞呈现较低的细胞因子水平,包括I型IFN。综上所述,我们的结果揭示了先天免疫信号传导中的新型调节机制,并确定了SPSB1在限制NF-κB活化中的重要作用。
更新日期:2020-01-21
down
wechat
bug