Coordinated functions of ER quality control mechanisms in pancreatic islet α cells

总结 糖尿病发病机制的一个中心组成部分是胰岛素和胰高血糖素从B和α分泌失调 内分泌胰腺的细胞。内分泌细胞依赖于细胞内的蛋白质质量控制（QC）系统。 内质网（ER）清除错误折叠的蛋白质，维持ER稳态，确保激素分泌 生产错误折叠的蛋白质部分通过Sel 1 L-Hrd 1 ER的底物特异性清除而被去除。 相关降解（ERAD），或通过自噬的聚集体的整体降解。我们最近的研究表明 ERAD和自噬调节β细胞生物学的不同方面-β细胞身份的维持， 生存，分别。尽管它们在控制葡萄糖稳态方面具有共同的重要性，但我们的理解是， α细胞生物学的发展滞后于β细胞。调节ER稳态的机制（因此，合成 α细胞的能力仍然在很大程度上未被探索。为此，缺乏Sel 1 L-Hrd 1 ERAD或 α细胞的自噬特征。ERAD缺陷会限制胰高血糖素的产生和α细胞群， 不损害对低血糖的全身性胰高血糖素分泌。与此相反，在α-淀粉样蛋白中， 细胞破坏ER体内平衡并损害胰高血糖素分泌。有趣的是，我们的初步数据 指出这两台QC机器之间存在潜在串扰。因此，这项建议将考验 总体假设Sel 1 L-Hrd 1 ERAD和自噬合作，以确保ER蛋白稳态， 胰腺α细胞-其对于α细胞身份、功能和/或存活至关重要。使用in的组合 使用小鼠模型、细胞系和人胰岛的体内和体外遗传学和药理学方法， 将测试以下目的：（1）证明ERAD之间相互作用的病理生理学重要性 阐明ERAD与自噬相互作用的分子机制 和α细胞中的自噬。这项研究将为α细胞中的ER QC机制提供前所未有的见解， 这可能被用来确定新的治疗方法，以解决糖尿病中的α细胞功能障碍。这 这项事业将建立在Reinert博士在发育生物学和生理学方面的科学专长基础上， 在两个前沿细胞生物学领域的培训，ERAD和自噬，重点是细胞器串扰。 此外，这项研究将通过提供最先进的细胞培训来加强Reinert博士的技术技能 生物技术，从而为她未来的职业生涯奠定了坚实的基础，作为一名医生科学家， 研究胰岛细胞生物学和病理生理学的跨学科小组。这个职业发展奖将是 由三位杰出的科学家和导师Ling Qi博士，Peter Arvan和Jandie Lin监督， 密歇根大学。

SUMMARY A central component of diabetes pathogenesis is dysregulated secretion of insulin and glucagon from b and α cells of the endocrine pancreas. Endocrine cells rely on protein quality control (QC) systems within the endoplasmic reticulum (ER) to clear misfolded proteins, maintain ER homeostasis and ensure hormone production. Misfolded proteins are removed in part through substrate-specific clearance by Sel1L-Hrd1 ER- associated degradation (ERAD), or bulk degradation of aggregates by autophagy. Our recent study showed that ERAD and autophagy regulate different aspects of β cell biology – maintenance of β cell identity and survival, respectively. Despite their shared importance in controlling glucose homeostasis, our understanding of α cell biology lags behind that of β cells. The mechanisms regulating ER homeostasis in (and thus, synthetic capacity of) α cells remain largely unexplored. To this end, mouse models lacking Sel1L-Hrd1 ERAD or autophagy in α cells were characterized. Defective ERAD limited glucagon production and α cell mass, but did not impair systemic glucagon secretion in response to hypoglycemia. In contrast, defective autophagy in α cells disrupted ER homeostasis and impaired glucagon secretion in vivo. Intriguingly, our preliminary data points to potential crosstalk between these two QC machineries. Hence, this proposal will test the overarching hypothesis that Sel1L-Hrd1 ERAD and autophagy cooperate to ensure ER proteostasis in pancreatic α cells – which is critical for α cell identity, function and/or survival. Using a combination of in vivo and in vitro genetic and pharmacologic approaches using mouse models, cell lines, and human islets, we will test the following Aims: (1) Demonstrate the pathophysiological importance of the interplay between ERAD and autophagy in α cells, and (2) Delineate the molecular mechanism underlying the crosstalk between ERAD and autophagy in α cells. This study will provide unprecedented insights into ER QC mechanisms in α cells, which may be harnessed to identify new therapeutic approaches to address α cell dysfunction in diabetes. This undertaking will build upon Dr. Reinert’s scientific expertise in developmental biology and physiology with training in two cutting-edge cell biology fields, ERAD and autophagy, with a focus on organelle crosstalk. Moreover, this study will strengthen Dr. Reinert’s technical skills by providing training in state-of-the-art cell biology techniques, thus paving a strong foundation for her future career as a physician scientist leading an interdisciplinary team studying islet cell biology and pathophysiology. This career development award will be overseen by three outstanding scientists and mentors Drs. Ling Qi, Peter Arvan, and Jiandie Lin at the University of Michigan.