Korczeniewska Justyna, Barnes Betsy J
Department of Biochemistry & Molecular Biology, New Jersey Medical School, UMDNJ, Newark, New Jersey, USA.
New Jersey Medical School-University Hospital Cancer Center, UMDNJ, Newark, New Jersey, USA.
Mol Cell Biol. 2018 Jan 16;38(3). doi: 10.1128/MCB.00493-17. Print 2018 Feb 1.
The transcription factor interferon regulatory factor 5 (IRF5) exerts crucial functions in the regulation of host immunity against extracellular pathogens, DNA damage-induced apoptosis, death receptor signaling, and macrophage polarization. Tight regulation of IRF5 is thus warranted for an efficient response to extracellular stressors and for limiting autoimmune and inflammatory responses. Here we report that the COP9 signalosome (CSN), a general modulator of diverse cellular and developmental processes, associates constitutively with IRF5 and promotes its protein stability. The constitutive CSN/IRF5 interaction was identified using proteomics and confirmed by endogenous immunoprecipitations. The CSN/IRF5 interaction occurred on the carboxyl and amino termini of IRF5; a single internal deletion (Δ455-466) was found to significantly reduce IRF5 protein stability. CSN3 was identified as a direct interacting partner of IRF5, and knockdown of this subunit with small interfering RNAs (siRNAs) resulted in enhanced degradation. Degradation was further augmented by knockdown of CSN1 and CSN3 together. The ubiquitin E1 inhibitor UBEI-41 or the proteasome inhibitor MG132 prevented IRF5 degradation, supporting that its stability is regulated by the ubiquitin-proteasome system. Importantly, activation of IRF5 by the death receptor ligand tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) resulted in enhanced degradation via loss of the CSN/IRF5 interaction. This study defines the CSN as a new interacting partner of IRF5 that controls its stability.
转录因子干扰素调节因子5（IRF5）在调节宿主针对细胞外病原体的免疫、DNA损伤诱导的细胞凋亡、死亡受体信号传导以及巨噬细胞极化方面发挥着关键作用。因此，对IRF5进行严格调控对于有效应对细胞外应激源以及限制自身免疫和炎症反应是必要的。在此，我们报告COP9信号体（CSN），一种多种细胞和发育过程的通用调节剂，与IRF5组成性结合并促进其蛋白质稳定性。通过蛋白质组学鉴定了组成性的CSN/IRF5相互作用，并通过内源性免疫沉淀得到证实。CSN/IRF5相互作用发生在IRF5的羧基末端和氨基末端；发现单个内部缺失（Δ455 - 466）会显著降低IRF5蛋白质稳定性。CSN3被鉴定为IRF5的直接相互作用伴侣，用小干扰RNA（siRNA）敲低该亚基会导致降解增强。同时敲低CSN1和CSN3会进一步增强降解。泛素E1抑制剂UBE1 - 41或蛋白酶体抑制剂MG132可阻止IRF5降解，支持其稳定性受泛素 - 蛋白酶体系统调节。重要的是，死亡受体配体肿瘤坏死因子（TNF）相关凋亡诱导配体（TRAIL）对IRF5的激活导致通过CSN/IRF5相互作用丧失而增强降解。本研究将CSN定义为控制IRF5稳定性的新相互作用伴侣。
