Emerging evidence suggests that ubiquitin mediated post translational modification is a critical regulatory process involved in diverse cellular pathways including cell death. During ubiquitination, E3 ligases recognize target proteins and determine the topology of ubiquitin chains. Recruitment of E3 ligases to targets proteins under stress conditions including oxidative stress and their implication in cell death have not been systemically explored. In the present study, we characterized the role of TRIM32 as an E3 ligase in regulation of oxidative stress induced cell death. TRIM32 is ubiquitously expressed in cell lines of different origin and form cytoplasmic speckle like structures that transiently interact with mitochondria under oxidative stress conditions. The ectopic expression of TRIM32 sensitizes cell death induced by oxidative stress whereas TRIM32 knockdown shows a protective effect. The turnover of TRIM32 is enhanced during oxidative stress and its expression induces ROS generation, loss of mitochondrial transmembrane potential and decrease in complex-I activity. The pro-apoptotic effect was rescued by pan-caspase inhibitor or antioxidant treatment. E3 ligase activity of TRIM32 is essential for oxidative stress induced apoptotic cell death. Furthermore, TRIM32 decreases X-linked inhibitor of apoptosis (XIAP) level and overexpression of XIAP rescued cells from TRIM32 mediated oxidative stress and cell death. Overall, the results of this study provide the first evidence supporting the role of TRIM32 in regulating oxidative stress induced cell death, which has implications in numerous pathological conditions including cancer and neurodegeneration.

新出现的证据表明，泛素介导的翻译后修饰是涉及多种细胞途径（包括细胞死亡）的关键调节过程。在泛素化过程中，E3 连接酶识别目标蛋白并确定泛素链的拓扑结构。尚未系统地探索在压力条件下将 E3 连接酶募集到靶蛋白，包括氧化应激及其对细胞死亡的影响。在本研究中，我们表征了 TRIM32 作为 E3 连接酶在调节氧化应激诱导的细胞死亡中的作用。TRIM32 在不同来源的细胞系中普遍表达，并形成细胞质斑点状结构，在氧化应激条件下与线粒体瞬时相互作用。TRIM32 的异位表达使氧化应激诱导的细胞死亡变得敏感，而 TRIM32 敲低显示出保护作用。TRIM32 的周转在氧化应激期间增强，其表达诱导 ROS 产生、线粒体跨膜电位的丧失和复合物 I 活性的降低。泛半胱天冬酶抑制剂或抗氧化剂治疗挽救了促凋亡作用。TRIM32 的 E3 连接酶活性对于氧化应激诱导的细胞凋亡至关重要。此外，TRIM32 降低 X 连锁细胞凋亡抑制剂 (XIAP) 水平和 XIAP 过表达从 TRIM32 介导的氧化应激和细胞死亡中拯救细胞。总的来说，这项研究的结果提供了第一个支持 TRIM32 在调节氧化应激诱导的细胞死亡中的作用的证据，