AMFR/Insig1通路在急性肾小管损伤中的作用及机制研究

针对AKI的发生机制进行深入研究是寻找AKI干预靶点的关键。内质网膜蛋白Insig1在脂代谢中发挥重要作用，但在AKI中的作用尚无报道。前期工作发现Insig1在AKI患者、小鼠肾脏及顺铂处理的肾小管细胞（RTEC）中明显下调；体内过表达Insig1显著改善了顺铂诱导的肾脏损伤，在体外也有同样的保护作用。蛋白质组学分析发现在肾小管敲除Insig1可显著影响内质网应激（ERS）通路，过表达Insig1则显著改善了顺铂诱导的ERS。有文献显示AMFR可泛素化降解Insig1。我们也发现AMFR在AKI肾脏显著上调，在RTEC过表达AMFR显著下调了Insig1蛋白表达，也加重了顺铂诱导的细胞凋亡。由此推测：致AKI因素通过上调AMFR导致Insig1的泛素化降解，进而通过促进ERS介导RTEC损伤和AKI。本课题将在整体、细胞和分子水平深入研究这一通路在急性肾小管损伤中的作用及机制。

Acute kidney injury （AKI）is a common clinical complication with high mortality. By now, the pathogenic mechanism of AKI remains unclear, which restricted the development of effective therapeutic strategies. ER-localized protein insulin-induced gene 1 (Insig1) plays an important role in lipid synthesis, while its role in kidney injury remains unknown. Our preliminary study indicated that Insig1 was downregulated in kidneys of AKI patients and animals and the renal tubular cells challenged with cisplatin. Strikingly, overexpression of Insig1 in vivo improved cisplatin-induced AKI, which was confirmed by an in vitro AKI model, suggesting a protective role of Insig1 against AKI. Furthermore, proteomics analysis indicated that specific deletion of Insig1 in renal tubules significantly affected the Endoplasmic Reticulum Stress (ERS) pathway. In renal tubular cells and kidneys, overexpressing Insig1 remarkably attenuated cisplatin-induced ERS. To explore the regulatory mechanism of Insig1, we reviewed literatures and found the report showing that Insig1 could be downregulated by AMFR via ubiquitination mechanism. Thus, we observed the regulation of AMFR under AKI and found an upregulation of AMFR in AKI kidneys. Importantly, overexpression of AMFR in renal tubular cells reduced Insig1 protein expression and deteriorated cisplatin-induced cell death. Based on above preliminary data and known concept, we raised our research hypothesis: under the AKI condition, the upregulation of AMFR in renal tubular cells could downregulate Insig1 protein (a suppressor of ERS) via ubiquitination mechanism, leading to enhanced ERS and renal tubular injury. This proposal will fully investigate AMFR/Insig1/ERS signaling pathway in the pathogenesis of AKI via using AKI patients’ samples and models of animals, cells and molecules, offering new insights into the understanding and therapy of AKI.