Nutrient-sensor O-GlcNAc Transferase Regulation of Autophagy in Homeostatis of Pancreatic Beta-cell Mass and Function

项目摘要/摘要 O-谷氨酸氨基转移酶是一种在胰腺β细胞中高表达的营养和应激敏感蛋白。这 该酶专一催化目标胞浆蛋白和核蛋白(O- GlcN酰化)。β-细胞OGT基因敲除小鼠出现严重的糖尿病表型，表明OGT在 塑造血糖动态平衡。这项研究的长期目标是了解 蛋白质O-GlcN酰化形成β-细胞健康和功能。O-GlcN酰化、mTORC1和AMPK信号转导 在包括2型糖尿病在内的许多疾病中调节失调。尽管我们在我们的 通过对营养感受器蛋白mTORC1、AMPK和OGT的研究来理解它们的作用 单独来说，它们在体内是如何串扰的在很大程度上是未知的。我们过去六年的研究工作揭示了 OGT通过其感知营养水平和协调凝聚力的能力促进β细胞的最佳健康 维持β细胞质量和诱导足够的胰岛素释放的细胞反应。在目前的提案中，我们将 验证OGT与mTORC1和AMPK及其下游引起串扰的主要假设 靶向ULK，负向调节自噬，维持β细胞质量和功能稳态。糖尿病 与β细胞中失调的自噬和改善自噬内稳态的干预有关 可能有益于减少由糖毒性引起的胰岛功能损害。我们将利用 具有OGT、mTORC1、AMPK和ULK功能增加或减少的创新体内模型，以测试 这些营养感受器蛋白之间的串扰调节自噬依赖的β细胞功能和 线粒体动态平衡。具体目标1：描述OGT通过 调节β细胞中的mTORC1信号转导。具体目标2：描述OGT在β自噬中的作用 细胞。这一新提议是创新的，因为目前还没有将OGT和mTORC1联系起来的研究 胰岛中的串扰及其对依赖自噬的β细胞团和胰岛素分泌的调节。一个 更好地理解主要营养和胁迫传感器之间的复杂相互作用OGT、mTOR和 AMPK信号在优化β细胞健康方面至关重要。我们的结果将揭示OGT作为一种 β细胞中营养信号通路的主要协调者，这些信号通路可能是β细胞保存的有价值的目标， 为糖尿病患者的治疗提供新的治疗模式。

PROJECT SUMMARY/ABSTRACT O-GlcNAc transferase (OGT) is a nutrient and stress sensor protein highly expressed in pancreatic β-cells. This enzyme exclusively catalyzes the post-translational glycosylation of target cytosolic and nucleic proteins (O- GlcNAcylation). β-cell OGT knockout mice develop severe diabetic phenotype, suggesting that OGT is crucial in shaping glucose homeostasis. The long-term goal of this research is to understand the mechanisms of how protein O-GlcNAcylation shape β-cell health and function. O-GlcNAcylation, mTORC1 and AMPK signaling are dysregulated in many diseases including Type 2 diabetes. Although we have made advancements in our understanding of the roles of nutrient sensor proteins mTORC1, AMPK, and OGT by studying them independently, how they crosstalk in vivo is largely unknown. Our research work for the past six years reveal that OGT promotes optimal β-cell health through its ability to sense nutrient levels and orchestrate a cohesive cellular response to maintain β-cell mass and elicit sufficient insulin release. In this current proposal, we will test the main hypothesis that OGT elicits crosstalk with mTORC1 and AMPK, and their downstream target ULK, to negatively regulate autophagy to maintain β-cell mass and function homeostasis. Diabetes is associated with dysregulated autophagy in β-cells and interventions ameliorating autophagy homeostasis could be beneficial in reducing functional impairments in islets caused by glucolipotoxicity. We will leverage innovative in vivo models with increased or reduced function of OGT, mTORC1, AMPK, and ULK to test the crosstalk among these nutrient-sensor proteins regulating autophagy-dependent β-cell function and mitochondrial homeostasis. Specific Aim 1: To delineate molecular mechanisms through which OGT regulates mTORC1 signaling in β-cells. Specific Aim 2: To delineate the role of OGT on autophagy in β- cells. This new proposal is innovative because there are currently no studies linking OGT and mTORC1 crosstalk in pancreatic islets and their regulation of autophagy-dependent β-cell mass and insulin secretion. A greater understanding of the complex interactions between major nutrient and stress sensors OGT, mTOR and AMPK signaling is critical in optimizing β-cell health. Our results will reveal the central function of OGT as a master orchestrator of nutrient signaling pathways in β-cells that may be valuable targets for β-cells preservation, providing new therapeutic models for treating patients with diabetes.