Linear ubiquitination is a novel type of ubiquitination that plays important physiological roles in signalling pathways such as tumour necrosis factor (TNF) signalling. However, little is known about the regulatory mechanisms of linear ubiquitination, except the well-described enzymatic regulators E3 ligase linear ubiquitin chain assembly complex (LUBAC) and deubiquitinase OTULIN. Previously, we identified SNX27, a member of the sorting nexin family protein, as a selective linear ubiquitin chain interactor in mass spectrometry-based ubiquitin interaction screening. Here, we demonstrated that the interaction between the linear ubiquitin chain and SNX27 is mediated by the OTULIN. Furthermore, we found that SNX27 inhibits LUBAC-mediated linear ubiquitin chain formation and TNFα-induced signalling activation. Mechanistic studies showed that, upon TNFα stimulation, OTULIN-SNX27 is localised to membrane-associated TNF receptor complex, where OTULIN deubiquitinates the linear polyubiquitin chain that formed by the LUBAC complex. Significantly, chemical inhibition of SNX27-retromer translocation by cholera toxin inhibits OTULIN membrane localization. In conclusion, our study demonstrated that SNX27 inhibits TNFα induced NF-κB signalling activation via facilitating OTULIN to localize to TNF receptor complex.

中文翻译：

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SNX27 驱动的 OTULIN 膜定位拮抗线性泛素化和 NF-κB 信号激活

线性泛素化是一种新型泛素化，在肿瘤坏死因子 (TNF) 信号转导等信号通路中起着重要的生理作用。然而，关于线性泛素化的调控机制知之甚少，除了描述良好的酶促调节剂 E3 连接酶线性泛素链组装复合物 (LUBAC) 和去泛素化酶 OTULIN。以前，我们将 SNX27（分选 nexin 家族蛋白的成员）确定为基于质谱的泛素相互作用筛选中的选择性线性泛素链相互作用物。在这里，我们证明了线性泛素链和 SNX27 之间的相互作用是由 OTULIN 介导的。此外，我们发现 SNX27 抑制 LUBAC 介导的线性泛素链形成和 TNFα 诱导的信号激活。机理研究表明，在 TNFα 刺激下，OTULIN-SNX27 定位于膜相关 TNF 受体复合物，其中 OTULIN 使由 LUBAC 复合物形成的线性多泛素链去泛素化。重要的是，霍乱毒素对 SNX27-retromer 易位的化学抑制抑制了 OTULIN 膜定位。总之，我们的研究表明，SNX27 通过促进 OTULIN 定位于 TNF 受体复合物来抑制 TNFα 诱导的 NF-κB 信号激活。