The role of Tomosyn-2 in insulin secretion and glucose tolerance

Tomosyn-2在胰岛素分泌和葡萄糖耐量中的作用

基本信息

批准号：
10549803
负责人：
Sushant Bhatnagar
金额：
$ 37.13万
依托单位：
UNIVERSITY OF ALABAMA AT BIRMINGHAM
依托单位国家：
美国
项目类别：
财政年份：
2019
资助国家：
美国
起止时间：
2019-04-05 至 2025-01-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10549803
关键词：
Acute Adult Affect B-Lymphocytes Beta Cell Binding Binding Proteins Biochemical Biological Assay Blood Glucose Cell Line Cell membrane Cell physiology Chronic Co-Immunoprecipitations Competence Complex Cues Cyclic AMP Data Defect Development Diabetes Mellitus Diglycerides Disease Disease model Epidemic Event Exocytosis Functional disorder Genes Genetic Glucose Goals High Fat Diet Human Hyperglycemia Impairment In Vitro Insulin Insulin Antagonists Insulin Resistance Islets of Langerhans Kinetics Knockout Mice Knowledge Mediating Methods Microscopic Mission Molecular Molecular Target Mus Mutation Non-Insulin-Dependent Diabetes Mellitus Nutritional Outcome Pathway interactions Peripheral Persons Phase Phenotype Phosphorylation Phosphorylation Site Physiology Plasma Population Post-Translational Protein Processing Prediabetes syndrome Predisposition Prevention Proteins Public Health Regulation Role SNAP receptor Signal Pathway Structure of beta Cell of islet Testing Therapeutic Thinness Ubiquitin United States United States National Institutes of Health confocal imaging diabetic forward genetics gain of function mutation genetic approach glucose tolerance hormonal signals hormone regulation impaired glucose tolerance improved innovation insight insulin granule insulin regulation insulin secretion islet knock-down novel prevent protein degradation recruit response secretion process soluble NSF attachment protein synaptotagmin syntaxin syntaxin A ubiquitin-protein ligase

项目摘要

Type 2 diabetes (T2D) has reached epidemic proportions, with ~9.4% of the US adult population being diabetic, and another 84.1 million have pre-diabetes. It is currently acknowledged that both insulin resistance and b-cell dysfunction are early and essential events in the development of T2D. The formation of the SNARE (Soluble NSF Attachment Protein Receptor) complex is rate limiting for insulin secretion. Our understanding of factors that regulate the formation of the SNARE complex and how they contribute to reduced insulin secretion from b- cells in impaired glucose tolerance is lacking. To this end, by using forward genetics approach, we have identified Tomosyn-2, which is an endogenous inhibitor of insulin secretion and functions by binding to syntaxin. Syntaxin is a key component of the SNARE complex that modulates the fusion of the insulin granules to the plasma membrane for insulin secretion from b-cells. We have discovered that a gain-of-function mutation in the Tomosyn-2 gene led to an increase in islet Tomosyn-2 protein abundance and formation of hypoinsulinemic/ hyperglycemic phenotypes in mice. Increased abundance and/or the functional activity of Tomosyn-2 causes reduction in insulin secretion from human and mouse islets. Thus, the long-term goal is to understand how Tomosyn-2 function in b-cells can be manipulated to improve insulin secretion in impaired glucose tolerance for the treatment and prevention of prediabetes and T2D. The objective of this application is to determine how Tomosyn-2 inhibits insulin secretion from b-cells in the pathophysiology, physiology, and at the molecular level, and how its inhibitory function in b-cells is regulated. Our data show that the improved glucose tolerance in Tomosyn-2-null mice is a direct result of enhanced insulin secretion from pancreatic islets. Further, reduced insulin secretion is observed in islets of mice on a high-fat diet that have elevated Tomosyn-2 protein levels. We have identified phosphorylation sites in response to major b-cell signaling pathways that modulate Tomosyn-2 inhibitory function. Also, E3-ubiquitin ligase, Hrd1 and an insulin granule protein, Syt9 bind and regulate the protein abundance of Tomosyn-2. Our hypothesis is that Tomosyn-2 is a key protein in the exocytotic machinery that regulates SNARE complex-mediated insulin secretion in response to nutritional and genetic cues, and that specific post-translational modifications of Tomosyn-2 increase insulin secretion. To test this hypothesis, we propose three aims: 1) determine the sub-cellular mechanisms by which Tomosyn-2 inhibits insulin secretion, 2) determine Tomosyn-2 phosphorylation regulates its activity on downstream insulin secretion, and 3) determine the role of the Tomosyn-2-binding proteins, Syt9 and Hrd1, in regulating insulin secretion. Outcomes from this project will provide novel information on how b-cells prevent inappropriate insulin secretion, identify the molecular target for the early phase insulin secretion, and insights into the loss in fusion competency of insulin granules during impaired glucose tolerance. Our results will provide fundamental new knowledge of the nutritional and hormonal regulation of the SNARE complex, identifying steps that could be modulated therapeutically in T2D.

2型糖尿病（T2D）已达到流行比例，约9.4％的美国成年人口为糖尿病，另外8410万人有糖尿病前。目前公认的是胰岛素抵抗和B细胞功能障碍是T2D发展的早期和基本事件。圈套的形成（可溶性 NSF附着蛋白受体）复合物是胰岛素分泌的速率限制。我们对因素的理解调节军鼓复合物的形成及其如何促进b-的胰岛素分泌减少缺乏葡萄糖耐受性受损的细胞。为此，通过使用远期遗传学方法，我们已经确定了 tomosyn-2，它是一种与义大素结合，是胰岛素分泌和功能的内源性抑制剂。语法素是SNARE复合物的关键组成部分，可调节胰岛素颗粒与等离子体的融合 B细胞的胰岛素分泌的膜。我们已经发现，功能奖励突变 tomosyn-2基因导致胰岛tomosyn-2蛋白丰度的增加，并形成低胰岛素/血症/ 小鼠高血糖表型。 tomosyn-2原因的丰度和/或功能活性增加减少人类和小鼠胰岛的胰岛素分泌。因此，长期目标是了解如何可以操纵B细胞中的tomosyn-2功能，以改善葡萄糖耐受性受损的胰岛素分泌糖尿病前期和T2D的治疗和预防。该应用程序的目的是确定如何 tomosyn-2抑制病理生理，生理学和分子水平的B细胞的胰岛素分泌，以及如何调节其在B细胞中的抑制功能。我们的数据表明，提高的葡萄糖耐受性 Tomosyn-2-Null小鼠是胰岛胰岛素分泌增强的直接结果。此外，减少了在高脂饮食的小鼠胰岛中观察到胰岛素分泌，该饮食升高了tomosyn-2蛋白水平。我们已经确定了响应主要B细胞信号通路的磷酸化位点，该途径调节tomosyn-2 抑制功能。另外，E3-泛素连接酶，HRD1和胰岛素颗粒蛋白，SYT9结合并调节 tomosyn-2的蛋白质丰度。我们的假设是，tomosyn-2是胞胞胞菌机械中的关键蛋白这可以调节对营养和遗传线索的反应，从而调节核心复合物介导的胰岛素分泌，并且 tomosyn-2的特定翻译后修饰增加了胰岛素分泌。为了检验这一假设，我们提出三个目的：1）确定tomosyn-2抑制胰岛素分泌的亚细胞机制，2）确定tomosyn-2磷酸化调节其对下游胰岛素分泌的活性，3）确定 Tomosyn-2结合蛋白SYT9和HRD1在调节胰岛素分泌方面的作用。结果项目将提供有关B细胞如何防止不适当胰岛素分泌的新信息，确定分子早期胰岛素分泌的靶标，以及对胰岛素颗粒融合能力损失的见解在葡萄糖耐受性受损期间。我们的结果将为营养和圈圈复合物的激素调节，识别可以在T2D中调节治疗的步骤。