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

• 批准号: 9913532
• 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
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-04-05 至 2024-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9913532
• 关键词: Acute; Adenosine Monophosphate; 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; Data; Defect; Development; Diabetes Mellitus; Diglycerides; Disease; Disease model; Epidemic; Event; Exocytosis; Functional disorder; Genes; 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; Periodicity; Peripheral; 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; base; 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; nutrition related genetics; prevent; protein degradation; recruit; response; secretion process; soluble NSF attachment protein; synaptotagmin; syntaxin; syntaxin A; syntaxin-2; ubiquitin-protein ligase

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（T2 D）已达到流行比例，约9.4%的美国成年人口患有糖尿病， 另有8410万人患有糖尿病前期。目前认为，胰岛素抵抗和B细胞 功能障碍是T2 D发展中的早期和基本事件。陷阱的形成（可溶性） NSF附着蛋白受体）复合物是胰岛素分泌的限速剂。我们对因素的理解 调节SNARE复合物的形成，以及它们如何有助于减少B- 葡萄糖耐量受损的细胞缺乏。为此，通过使用正向遗传学方法，我们已经确定， Tomosyn-2是胰岛素分泌的内源性抑制剂，通过与突触融合蛋白结合发挥作用。Syntaxin 是调节胰岛素颗粒与血浆融合的SNARE复合物的关键成分 B细胞分泌胰岛素的膜。我们已经发现，一个功能获得性突变， Tomosyn-2基因导致胰岛Tomosyn-2蛋白丰度增加，并形成低胰岛素血症。 小鼠的高血糖表型。Tomosyn-2的丰度和/或功能活性的增加导致 减少人和小鼠胰岛的胰岛素分泌。因此，长期目标是了解如何 Tomosyn-2在B细胞中的功能可以被操纵以改善葡萄糖耐量受损的胰岛素分泌， 糖尿病前期和T2 D的治疗和预防。本申请的目的是确定如何 Tomosyn-2在病理生理学、生理学和分子水平上抑制b细胞的胰岛素分泌， 以及它在B细胞中的抑制功能是如何被调节的。我们的数据表明， Tomosyn-2缺失小鼠是胰岛胰岛素分泌增强的直接结果。此外，减少 在Tomosyn-2蛋白水平升高的高脂肪饮食小鼠的胰岛中观察到胰岛素分泌。我们 已经鉴定了响应于调节Tomosyn-2的主要b细胞信号通路的磷酸化位点 抑制功能此外，E3-泛素连接酶Hrd 1和胰岛素颗粒蛋白Syt 9结合并调节胰岛素的分泌。 Tomosyn-2的蛋白丰度。我们的假设是Tomosyn-2是胞吐机制中的关键蛋白 调节SNARE复合物介导的胰岛素分泌以响应营养和遗传线索， Tomosyn-2的特异性翻译后修饰增加胰岛素分泌。为了验证这个假设，我们 提出三个目标：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，以及3）确定 Tomosyn-2结合蛋白Syt 9和Hrd 1在调节胰岛素分泌中的作用。由此产生的结果 该项目将提供关于b细胞如何防止胰岛素分泌不当的新信息， 早期胰岛素分泌的靶点，以及对胰岛素颗粒融合能力丧失的认识 葡萄糖耐量受损的时候。我们的研究结果将提供有关营养和 SNARE复合物的激素调节，确定可以在T2 D中进行治疗调节的步骤。