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

项目总结 到目前为止，在全基因组关联研究中确定的大多数糖尿病相关基因是 富含胰岛β细胞。β细胞衰竭在发育和发育中起着核心作用 2型糖尿病的进展(T2D)。内质网(ER)是一种中枢细胞器。 胰岛素原的大规模生产和加工。内质网稳态对正常的胰岛β细胞至关重要 功能，由蛋白质合成、折叠、输出和输出之间的微妙平衡维持 退化。相比之下，内质网稳态的破坏，由许多遗传和环境因素造成 导致糖尿病的因素，诱导内质网应激，并导致T2D中的β细胞死亡。与我们的 了解β细胞内质网的蛋白质合成、折叠和降解，以及内质网输出在 胰岛素原的生物发生和内质网的动态平衡知之甚少。这项提议解决了这个问题 知识鸿沟。我们已经获得了强有力的初步结果，证明胰岛素原的内质网存在 需要COPII(外壳蛋白复合体II)包被的小泡和有缺陷的COPII依赖内质网输出 强烈诱导内质网应激。除了我们的结果，最近开始有证据表明 内质网高尔基体转运减少是导致脂肪毒性诱导的内质网应激的原因。在…的基础上 这些新的发现，我们的目标是确定葡萄糖和脂质毒性如何影响内质网输出 β细胞中的蛋白质货物，特别是胰岛素原，以及有缺陷的内质网输出如何反过来促进 内质网应激和β细胞功能障碍。超过一千种蛋白质，被称为蛋白质平衡 网络，已被提出维持内质网的动态平衡。然而，到目前为止，只有很小的 许多ER蛋白因参与内质网应激或胰岛素原而被研究 β细胞的生物发生。需要系统的蛋白质组学分析才能全面了解 在T2D开始时，不同的糖尿病致病条件如何扰乱β细胞ER的动态平衡。在……里面 这项提议，使用系统生物学的方法，我们将检验中心假设 糖脂毒性等促糖尿病因子通过干扰内质网干扰β细胞内质网功能 蛋白质稳态和COPII依赖的内质网输出。这项建议有两个具体目的：1) 确定依赖COPII的内质网出口如何在健康和糖尿病中受到调节；2)确定内质网如何 糖尿病患者伴侣蛋白和折叠酶的改变及其对β细胞内质网的影响 出口。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 表征糖尿病致病因素分子机制的方法 差异性改变内质网动态平衡。重点将放在ER出口上，这是一个调查不足的 β细胞内质网内稳态的组成部分。

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.