CCDC92在糖尿病肾病足细胞脂毒性损伤中的作用及机制

Recent epidemiological evaluation report shows that the hospitalized population with chronic kidney disease related to diabetes has become the first cause for chronic kidney disease. Increasing evidences indicate that podocyte lipotoxicity is critical for the occurrence and development of diabetic kidney disease (DKD). The latest clinical research shows that coiled-coil domain containing protein 92 (CCDC92) is a common risk gene for coronary heart disease and type 2 diabetes, while the biological function of CCDC92 is unknown till now. Our preliminary studies suggested that CCDC92 might play an important role in podocyte injury and lipid metabolism in diabetic kidney disease, but the mechanism is not yet understood. In this study, we will use podocyte specific knockout mice, cultured human podocytes and clinical renal biopsy sections to investigate the role of CCDC92 on podocyte lipotoxicity in diabetic kidney disease by various methods of morphology, cellular and molecular biology, immunoelectron microscopy, flow cytometry, confocal as well as isotope labeling. Moreover, we are going to demonstrate that the mechanism of this effect is partly through increasing the proteasome subunits accumulation on the cellular centrosome, which may activate ubiquitin proteasome system subsequently. As a sequence, the ATP-binding cassette transporter A1 (ABCA1) protein which mediates the cholesterol efflux from cell will be decreased by the ubiquitin-proteasome-mediated degradation, resulting in cholesterol accumulation and therefore inducing the podocyte injury. We also intend to demonstrate that the effect of CCDC92 in podocyte lipotoxicity is regulated by NADPH oxidase NOX4 mediated oxidative stress. Our study may enrich the pathophysiologic mechanisms of diabetic kidney disease, add new results for the signal pathway of podocyte lipotoxicity,supply more informations for the biological function of CCDC92 as well . Furthermore, our work may provide a new viewpoint for the potential theraputic methods of slowing the progress of diabetic kidney disease in the future.

糖尿病相关肾脏疾病已成为我国慢性肾脏疾病的首要病因，足细胞脂质代谢紊乱参与了糖尿病肾病的发生和发展。最新临床研究报道卷曲螺旋结构域蛋白CCDC92是冠心病和2型糖尿病共同的风险基因，但其生物学功能尚不清楚。我们前期实验发现CCDC92在糖尿病肾病足细胞损伤中扮演重要角色，但机制不明。本课题将通过足细胞特异性基因敲除小鼠、体外培养足细胞和临床切片，借助形态学、细胞和分子生物学、免疫电镜、流式细胞术、激光共聚焦、同位素标记等方法明确在糖尿病肾病过程中，CCDC92通过增加足细胞中蛋白酶体在中心体的聚集，增强泛素/蛋白酶体系统的活性，增加细胞内胆固醇外排酶ABCA1的降解，引起胆固醇累积，造成脂毒性损伤，且该作用受到NOX4介导的氧化应激通路的调控。本课题将对糖尿病肾病的病理生理机制和CCDC92的生物学功能进行补充，并为临床寻找延缓糖尿病肾病进展的有效策略提供新的靶点与研究基础。

糖尿病肾病是糖尿病最常见的血管并发症，也是导致终末期肾病的主要原因。最新流行病学评估结果表明，糖尿病相关肾脏疾病已成为我国慢性肾脏疾病的首要病因，而足细胞损伤被认为是糖尿病肾病最重要的早期事件，足细胞糖脂代谢平衡紊乱是引起糖尿病肾病发生和发展的重要因素。卷曲螺旋结构域蛋白（CCDC）是一类以α-螺旋卷曲结构域为特征的蛋白家族，其分子中特有的卷曲螺旋基序使之具有形成细胞骨架、调控细胞极性及运动、转运细胞内物质以及分子识别和信号转导等多种功能。CCDC92是卷曲结构域蛋白家族的新成员，尽管以全基因组关联（GAWS）研究为基础的大量临床分析数据表明CCDC92的遗传变异可能参与脂代谢相关疾病，但目前尚无系统的研究探索CCDC92在肾脏中的功能及其信号转导途径。本课题利用足细胞特异性CCDC92基因敲除模式动物，通过建立多种糖尿病肾病动物模型，结合体外培养足细胞和临床病人的肾活检组织切片，借助于形态学、细胞和分子生物学、流式细胞学、激光共聚焦、液质联用等方法，研究了明确在糖尿病肾病过程中，CCDC92蛋白中的59-113氨基酸序列区段通过结合足细胞中的蛋白酶体激活成分PA28α，增强蛋白酶体活性，增加足细胞内胆固醇外排酶ABCA1的降解，引起胆固醇累积，造成脂毒性损伤。本课题将对糖尿病肾病的病理生理机制和CCDC92的生物学功能进行补充，同时为临床寻找延缓糖尿病肾病进展的有效策略提供新的靶点与研究基础。