重金属通过抑制Leydig细胞（LC）的类固醇激素合成，严重影响男性生殖功能，其机制研究停留在抑制激素合成酶和损伤线粒体上，仍未深入和明确。前期研究中，我们发现二氢硫辛酰胺脱氢酶（DLD）作为镉对LC毒性作用的重要靶点，通过调控ATP和cAMP的生成参与激素合成，其过表达可以逆转镉的毒性效应。在明确镉通过泛素蛋白酶体途径降解DLD蛋白后，应用免疫共沉淀结合LTQ-Orbitrap蛋白质谱技术，我们率先鉴定出了调控DLD泛素化降解的特异E3泛素连接酶Arel1。本研究拟验证Arel1与DLD蛋白的相互作用，阐明镉在LC中通过Arel1介导的毒性作用及其分子机制；利用计算机分子模拟技术结合分子生物学手段筛选两者互作的活性氨基酸位点，设计特异拮抗肽并予以功能验证和完成药效学评价实验。本研究有助于明确男性性功能低下不育症和中老年性功能障碍的发病机制，并为其诊断和治疗提供新的检测终端和治疗思路。

Heavy metals are environmental toxigen to male reproductive health. Although there are many studies disclosed the toxic effects of heavy metals on Leydig cells by decreasing testosterone secretion and mitochondrial damage, the cytotoxic mechanism is still poorly understood. Our previous study found that heavy metals led altered expressions of proteins related to mitochondria, significantly down-regulated the expression of dihydrolipoamide dehydrogenase (DLD). DLD regulates the steroid hormone synthesis by the generation of ATP and cAMP. DLD-siRNA inhibited the expression of progesterone synthesis enzymes (StAR, CYP11A1 and 3β-HSD) and the production of progesterone, while overexpression of DLD could antagonize the mitochondrial damage induced by cadmium and maintain the normal synthesis of steroid hormones. The degradation of DLD is mainly mediated by the ubiquitin proteasome pathway. The specific E3 ligase Apoptosis-resistant E3 ubiquitin protein ligase 1 (Arel1) was successfully identified by Co-immunoprecipitation combined with LC-MS/MS (LTQ-Orbitrap) technology in our previous study. In this study, the degradation of DLD mediated by Arel1 via ubiquitination will be verified; the interaction of Arel1 and DLD will be confirmed in the cellular and non-cellular systems; the role of interaction and its related mechanism will be explored in Leydig cells exposed to cadmium in vivo and in vitro. With the combination of computer-guided molecular simulation technology and traditional molecular biology methods, the key amino acids essential for the specific interaction of Arel1 and DLD will be identified. Based on the identification, several antagonistic peptides will be designed to interrupt the Arel1-DLD interaction. The antagonistic function will be verified in the model of Cd exposure in vivo and in vitro. This study will help to disclose the pathogenesis of male sexual dysfunction, and provide new targets in clinical therapy and diagnosis.