E3泛素连接酶Mule调控铁死亡的分子机制及其在肝损伤中的意义

铁死亡是新近发现的铁依赖的非凋亡性细胞死亡形式，涉及多种病理过程。然而，人们对于铁死亡的分子机制和生物学功能仍然知之甚少。申请人早期的研究工作表明Mule对DNA损伤造成的凋亡有促进作用，但最新结果显示Mule对铁死亡有意想不到的保护作用。Mule敲除的小鼠胚胎成纤维细胞对铁死亡更为敏感。在肝脏条件性敲除Mule的小鼠肝组织中，四氯化碳引起的急性损伤更早，同时伴随着铁死亡的加剧，包括脂质ROS的增强以及亚铁离子含量的剧增；这提示Mule缺失影响铁代谢。通过siRNA筛选，我们找到Mule的潜在底物-铁代谢关键因子转铁蛋白受体TfR2，并据此推测Mule缺失可通过累积TfR2促进铁死亡。本项目拟围绕“Mule-TfR2-铁死亡”这一轴线，进一步明确Mule对铁死亡的调控及其分子机制，并阐明其在铁死亡相关急性肝损伤疾病中的作用。这将有助于全面了解铁死亡的调控机制，为肝损伤疾病提供新的治疗思路。

Ferroptosis is a newly discovered iron-dependent form of non-apoptotic cell death involving in a variety of pathological processes. However, little is known about the molecular mechanisms and biological functions of ferroptosis. The Applicant’s previous study demonstrated that E3 ubiquitin ligase Mule knockout mouse embryonic fibroblasts （MEF） are more resistant to apoptosis induced by DNA damage and Histone Deacetylase Inhibitor. In the current study, they surprisingly observed that Mule Knockout MEFs are more susceptible to ferroptosis. Moreover, Carbon Chloride-induced liver injury is much earlier in Mule liver-specific knock-out mice compared to the wild-type mice, accompanied by the increase of both lipid oxidation and the ferrous iron content. These findings suggest that Mule deficiency promotes ferroptosis by regulating iron metabolism. Through siRNA screening, we found the key regulator of iron metabolism-transferrin receptor 2 (TfR2) as the potential substrate of Mule. Therefore, we hypothesize that Mule deficiency promotes ferroptosis through targeted ubiquitination and accumulation of TfR2. Based on these preliminary findings, the project will focus on the axis of “Mule-TfR2-ferroptosis”, aiming to further clarify the regulation of Mule on ferroptosis, its molecular mechanism through targeted ubiquitination of TfR2 and the pathological significance in the liver disease models related to ferroptosis. These studies will provide new insights into the molecular mechanism of ferroptosis and help us to design potential new therapeutic targets for the treatment of ferroptosis-related acute liver injury diseases.