Regulation of Glucagon Secretion from Pancreatic Islets

胰岛胰高血糖素分泌的调节

基本信息

批准号：
10264101
负责人：
David W Piston
金额：
$ 39.38万
依托单位：
WASHINGTON UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-09-14 至 2025-07-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10264101
关键词：
Alpha Cell Animals Beta Cell Biochemical Biological Assay Biosensor Cell physiology Cell surface Cells Cellular Structures Clinical Closure by clamp Complex Complications of Diabetes Mellitus Cyclic AMP Cyclic AMP-Dependent Protein Kinases D Cells Data Diabetes Mellitus Dominant-Negative Mutation Electrophysiology (science)Exhibits Exocytosis F-Actin Genetic Glucagon Glucagon Receptor Glucose Hormone secretion Hormones Human Hyperglycemia Hypoglycemia Image Individual Insulin Insulin-Dependent Diabetes Mellitus Ion Channel Islet Cell Islets of Langerhans Ligands Link Measurement Measures Mediating Methods Microfluidics Modeling Molecular Mus Non-Insulin-Dependent Diabetes Mellitus Paracrine Communication Pathology Pathway interactions Pattern Phosphorylation Play Proteins RNA Interference Regulation Research Role SNAP receptor Signal Pathway Signal Transduction Somatostatin Structure of alpha Cell of islet Structure of beta Cell of islet Testing Transgenic Mice Work base blood glucose regulation cell type diabetic patient euglycemia experimental study hyperglucagonemia improved in vivo innovation insulin signaling islet mouse model new therapeutic target novel pancreatic juice paracrine polymerization response rho GTP-Binding Proteins side effect small molecule therapeutic target treatment strategy

项目摘要

The islet of Langerhans plays a key role in glucose homeostasis through regulated hormone secretion. Islet research has focused on the insulin-secreting β-cells, even though aberrant secretion of another islet hormone, glucagon from α-cells, exacerbates the pathology of diabetes. Normalization of glucagon action by glucagon receptor antagonism can help diabetic patients maintain euglycemia and avoid hypoglycemic episodes, but progress on this approach has been slowed by numerous side-effects. An alternate approach would be to reduce glucagon secretion, but the mechanism controlling its exocytosis remains controversial. Recent data from our lab and others suggest that the long-standing focus on α-cell Ca2+ signaling may have been misleading, and that regulation of glucagon secretion requires signaling through multiple pathways. This complexity drives an innovative research strategy where we integrate data from mechanistic experiments focused on individual components, while also testing for possible cross-talk between pathways. The loss of glucose-regulation of glucagon secretion (GRGS) in vivo after β-cells are destroyed in Type I diabetes suggests that interactions between islet cell types are critical to α-cell function. This has led to models of paracrine signaling where secreted factors from islet β- and δ-cells constrain α-cell function. We have shown that insulin and somatostatin work in concert to reduce cAMP and PKA activity, which lowers glucagon secretion, but does not by itself explain GRGS. Preliminary data point to a key role for complexin 2 in linking PKA activity to secretion. We have also shown that a novel juxtacrine pathway, EphA4/7 forward signaling, is activated by ephrinA5 ligands on the β-cell surface. This effect leads to F-actin polymerization and decreased glucagon secretion, putatively via RhoA activation, and it appears to have a glucose-regulated component. Thus, both paracrine and juxtracrine pathways drive GRGS from islets, but dispersed α-cells treated with ephrinA5 also exhibit an additional GRGS mechanism, which appears to be intrinsic to the α-cell. Based on these data, we hypothesize that GRGS requires a synergistic combination of paracrine, juxtacrine, and cell-intrinsic signaling pathways. This hypothesis will be tested via three specific aims: 1) Determine the role of paracrine-mediated PKA-activated phosphorylation of complexin 2 in insulin- and somatostatin-mediated inhibition of glucagon secretion; 2) Determine the role of RhoA activation in the juxtacrine EphA4/7 forward signaling that leads to inhibition of glucagon secretion; 3) Determine the role of EphA4/7 forward signaling in intrinsic α-cell response to glucose. The multiple intracellular and intercellular signaling mechanisms that we are uncovering will be elucidated by methods that allow precise observation of the pertinent dynamics in living cells and islets. The research plan will also leverage our findings that the mechanisms of GRGS are similar in mouse and human α-cells, and we will perform parallel experiments across species to the extent possible. These experiments will further our understanding of α-cell function, which is a critical step towards discovering new potential targets for the regulation of glucagon and treatment of diabetes.

Langerhans的胰岛通过受管制的骑马分泌物在葡萄糖稳态中起关键作用。胰岛研究集中在分泌胰岛素的β细胞上，尽管另一匹胰岛马（来自α细胞的胰高血糖）的异常分泌加剧了糖尿病的病理。胰高血糖素受体拮抗作用的胰高血糖素作用的归一化可以帮助糖尿病患者维持凝血症并避免降血糖发作，但这种方法的进展已被多种副作用减慢。另一种方法是减少胰高血糖素的分泌，但是控制其胞吐作用的机制仍然浓缩。我们实验室和其他实验室的最新数据表明，对α细胞Ca2+信号传导的长期关注可能是误导性的，并且胰高血糖素分泌的调节需要通过多种途径进行信号传导。这种复杂性驱动了一种创新的研究策略，在该策略中，我们从机械实验中的数据集成了集中在各个组件上，同时还测试了途径之间可能的跨话。 β细胞在I型糖尿病中破坏后体内胰高血糖素分泌（GRGS）的葡萄糖调节的丧失表明胰岛细胞类型之间的相互作用对于α细胞功能至关重要。这导致了旁分泌信号传导来自胰岛和δ细胞的分泌因子限制了α细胞功能。我们已经表明，胰岛素和生长抑素协同工作以减少营地和PKA活动，从而降低胰高血糖素的分泌，但本身并不能解释GRG。初步数据表明，复杂蛋白2在将PKA活性与分泌联系起来的关键作用。我们还表明，新型的近距离途径Epha4/7正向信号传导被β细胞表面上的Ephrina5配体激活。这种作用通过RhoA激活推动了F-肌动蛋白聚合并改善胰高血糖素的分泌，并且似乎具有葡萄糖调节的成分。那是旁分泌和缩影途径从胰岛驱动GRG，但是用ephrina5处理的α细胞也暴露了另一种GRGS机制，这似乎与α细胞是固有的。基于这些数据，我们假设GRG需要旁分泌，近距离和细胞中性信号通路的协同组合。该假设将通过三个特定目的进行检验：1）确定复合蛋白2在胰岛素和生长抑素介导的胰高血糖素分泌抑制中的旁分泌介导的PKA激活的磷酸化的作用； 2）确定RhoA激活在近去二氨酸以Epha4/7前的作用导致胰高血糖素分泌的信号传导； 3）确定EPHA4/7正向信号传导在固有的α细胞对葡萄糖反应中的作用。我们正在发现的多个细胞内和细胞间信号传导机制将通过允许精确观察活细胞和胰岛相关动态的方法来阐明。该研究计划还将利用我们的发现，即在小鼠和人α细胞中GRG的机制相似，我们将尽可能地进行跨物种的平行实验。这些实验将进一步了解我们对α细胞功能的理解，这是朝着发现调节臀部和治疗糖尿病的新潜在目标的关键步骤。