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The SCFSkp2 ubiquitin ligase complex modulates TRAIL-R2-induced apoptosis by regulating FLIP(L).
Cell Death and Differentiation ( IF 13.7 ) Pub Date : 2020-04-20 , DOI: 10.1038/s41418-020-0539-7
Jamie Z Roberts 1 , Caitriona Holohan 1 , Tamas Sessler 1 , Jennifer Fox 1 , Nyree Crawford 1 , Joel S Riley 1 , Hajrah Khawaja 1 , Joanna Majkut 1 , Emma Evergren 1 , Luke M Humphreys 1 , Jennifer Ferris 1 , Catherine Higgins 1 , Margarita Espona-Fiedler 1 , Paul Moynagh 2, 3 , Simon S McDade 1 , Daniel B Longley 1
Affiliation  

TRAIL-R2 (DR5) is a clinically-relevant therapeutic target and a key target for immune effector cells. Herein, we identify a novel interaction between TRAIL-R2 and the Skp1-Cullin-1-F-box (SCF) Cullin-Ring E3 Ubiquitin Ligase complex containing Skp2 (SCFSkp2). We find that SCFSkp2 can interact with both TRAIL-R2's pre-ligand association complex (PLAC) and ligand-activated death-inducing signalling complex (DISC). Moreover, Cullin-1 interacts with TRAIL-R2 in its active NEDDylated form. Inhibiting Cullin-1's DISC recruitment using the NEDDylation inhibitor MLN4924 (Pevonedistat) or siRNA increased apoptosis induction in response to TRAIL. This correlated with enhanced levels of the caspase-8 regulator FLIP at the TRAIL-R2 DISC, particularly the long splice form, FLIP(L). We subsequently found that FLIP(L) (but not FLIP(S), caspase-8, nor the other core DISC component FADD) interacts with Cullin-1 and Skp2. Importantly, this interaction is enhanced when FLIP(L) is in its DISC-associated, C-terminally truncated p43-form. Prevention of FLIP(L) processing to its p43-form stabilises the protein, suggesting that by enhancing its interaction with SCFSkp2, cleavage to the p43-form is a critical step in FLIP(L) turnover. In support of this, we found that silencing any of the components of the SCFSkp2 complex inhibits FLIP ubiquitination, while overexpressing Cullin-1/Skp2 enhances its ubiquitination in a NEDDylation-dependent manner. DISC recruitment of TRAF2, previously identified as an E3 ligase for caspase-8 at the DISC, was also enhanced when Cullin-1's recruitment was inhibited, although its interaction with Cullin-1 was found to be mediated indirectly via FLIP(L). Notably, the interaction of p43-FLIP(L) with Cullin-1 disrupts its ability to interact with FADD, caspase-8 and TRAF2. Collectively, our results suggest that processing of FLIP(L) to p43-FLIP(L) at the TRAIL-R2 DISC enhances its interaction with co-localised SCFSkp2, leading to disruption of p43-FLIP(L)'s interactions with other DISC components and promoting its ubiquitination and degradation, thereby modulating TRAIL-R2-mediated apoptosis.

中文翻译:

SCFSkp2 泛素连接酶复合物通过调节 FLIP(L) 调节 TRAIL-R2 诱导的细胞凋亡。

TRAIL-R2 (DR5) 是临床相关的治疗靶点和免疫效应细胞的关键靶点。在这里,我们确定了 TRAIL-R2 与含有 Skp2 (SCFSkp2) 的 Skp1-Cullin-1-F-box (SCF) Cullin-Ring E3 泛素连接酶复合物之间的新型相互作用。我们发现 SCFSkp2 可以与 TRAIL-R2 的前配体结合复合物 (PLAC) 和配体激活的死亡诱导信号复合物 (DISC) 相互作用。此外,Cullin-1 与其活性 NEDDylated 形式的 TRAIL-R2 相互作用。使用 NEDDylation 抑制剂 MLN4924 (Pevonedistat) 或 siRNA 抑制 Cullin-1 的 DISC 募集会增加对 TRAIL 的细胞凋亡诱导。这与 TRAIL-R2 DISC 中 caspase-8 调节因子 FLIP 的水平升高有关,特别是长剪接形式 FLIP(L)。我们随后发现 FLIP(L)(但不是 FLIP(S)、caspase-8、其他核心 DISC 组件 FADD 也不与 Cullin-1 和 Skp2 相互作用。重要的是,当 FLIP(L) 处于其 DISC 相关、C 末端截断的 p43 形式时,这种相互作用会得到增强。防止 FLIP(L) 加工成其 p43 形式可以稳定蛋白质,这表明通过增强其与 SCFSkp2 的相互作用,切割为 p43 形式是 FLIP(L) 营业额的关键步骤。为了支持这一点,我们发现沉默 SCFSkp2 复合物的任何成分都会抑制 FLIP 泛素化,而过表达 Cullin-1/Skp2 会以 NEDDylation 依赖的方式增强其泛素化。TRAF2 的 DISC 募集(之前被确定为 DISC 中 caspase-8 的 E3 连接酶)在 Cullin-1 的募集受到抑制时也得到了增强,尽管发现它与 Cullin-1 的相互作用是通过 FLIP(L) 间接介导的。尤其,p43-FLIP(L) 与 Cullin-1 的相互作用破坏了其与 FADD、caspase-8 和 TRAF2 相互作用的能力。总的来说,我们的结果表明,在 TRAIL-R2 DISC 处理 FLIP(L) 到 p43-FLIP(L) 增强了它与共定位 SCFSkp2 的相互作用,导致 p43-FLIP(L) 与其他 DISC 相互作用的中断成分并促进其泛素化和降解,从而调节 TRAIL-R2 介导的细胞凋亡。
更新日期:2020-04-24
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