Proinsulin ER Export and Beta Cell ER Homeostasis in Health and Diabetes

项目摘要 迄今为止，在全基因组关联研究中鉴定的大多数糖尿病相关基因是 富含胰腺β细胞β细胞衰竭在发育中起着核心作用， 2型糖尿病（T2D）的进展。内质网（ER）是细胞的中心细胞器， 胰岛素原的大规模生产和加工。ER稳态对正常β细胞至关重要 功能，并通过蛋白质合成，折叠，输出和运输之间的微妙平衡来维持。 降解相反，许多遗传和环境因素对内质网稳态的破坏， 糖尿病致病因子，诱导ER应激并导致T2D中的β细胞死亡。比起我们 在β细胞ER中的蛋白质合成，折叠和降解方面的知识， 胰岛素原生物合成和ER稳态的研究知之甚少。该提案针对这一点 知识差距。我们已经获得了强有力的初步结果，表明胰岛素原的ER退出 需要COPII（外壳蛋白复合物II）包被的囊泡和有缺陷的COPII依赖性ER输出 强烈诱导ER应激。除了我们的研究结果，最近开始出现的证据表明， 减少的ER-高尔基体转运是β细胞中脂毒性诱导的ER应激的原因。的基础上 这些新的发现，我们的目的是确定如何葡萄糖和脂质毒性影响ER输出的 β细胞中的蛋白质货物，特别是胰岛素原，以及有缺陷的ER输出如何反过来有助于 ER应激和β细胞功能障碍。超过1000种蛋白质，被称为蛋白质稳态 网络，已被提出来维持ER稳态。然而，到目前为止，只有一个非常小的 已经研究了许多ER蛋白参与ER应激或胰岛素原 β细胞的生物合成需要进行系统的蛋白质组学分析， 不同的糖尿病引起的条件如何在T2D发作时扰乱β细胞ER稳态。在 在这个提议中，我们将使用系统生物学方法来检验中心假设， 致糖尿病因素如糖脂毒性通过干扰ER破坏β细胞ER功能 蛋白质稳态和COPII依赖的ER输出。这项建议有两个具体目标：1） 确定COPII依赖性ER输出如何在健康和糖尿病中调节; 2）确定ER如何 糖尿病中的伴侣蛋白和折叠酶发生改变，以及这些变化如何影响β细胞ER 导出.这项研究将使用最先进的定量蛋白质组学和其他系统生物学 表征糖尿病致病条件的分子机制的方法 差异改变ER稳态。重点将放在ER出口上，这是一个调查不足的问题。 β细胞ER稳态的组成部分。

PROJECT SUMMARY Up to date, most of the diabetes-associated genes identified in genome-wide association studies are enriched in the pancreatic beta cells. Beta cell failure plays a central role in the development and progression of type 2 diabetes (T2D). The endoplasmic reticulum (ER) is a central organelle for the massive production and processing of proinsulin. ER homeostasis is critical for normal beta cell function and is maintained by the delicate balance between protein synthesis, folding, export and degradation. In contrast, the disruption of ER homeostasis, by many genetic and environmental diabetes-causing factors, induces ER stress and causes beta cell death in T2D. Compared to our knowledge in protein synthesis, folding and degradation in beta cell ER, the role of ER export in proinsulin biogenesis and ER homeostasis is much less understood. This proposal addresses this knowledge gap. We have obtained strong preliminary results demonstrating that ER exit of proinsulin requires COPII (coat protein complex II) coated vesicles and defective COPII dependent ER export strongly induces ER stress. In addition to our results, evidence has recently begun to emerge that reduced ER-Golgi transport is causative to lipotoxicity-induced ER stress in beta cells. On the basis of these novel findings, we aim to determine how glucose- and lipid-toxicity affect the ER export of protein cargo, particularly proinsulin, in beta cells and how defective ER export, in turn, contributes to ER stress and beta cell dysfunction. Over a thousand proteins, referred to as the proteostasis network, have been proposed to maintain ER homeostasis. However, to date, only a very small number of ER proteins have been investigated for their involvement in ER stress or proinsulin biogenesis in beta cells. A systematic proteomics analysis is needed to comprehensively understand how different diabetes-causing conditions perturb beta cell ER homeostasis at the onset of T2D. In this proposal, using systems biology approaches, we will test the central hypothesis that diabetogenic factors such as glucolipotoxicity disrupt beta cell ER function through perturbing ER protein homeostasis and COPII dependent ER export. There are two specific aims in this proposal: 1) Determine how COPII dependent ER export is regulated in health and diabetes; 2) Determine how ER chaperones and folding enzymes are altered in diabetes and how these changes affect beta cell ER export. This study will use state-of-the-art quantitative proteomics and other systems biology approaches to characterize the molecular mechanisms by which diabetes-causing conditions differentially alter ER homeostasis. The emphasis will be on the ER export, an under-investigated component of beta cell ER homeostasis.