Microtubule Regulation of Pancreatic Beta Cell Function and Diabetes

胰腺β细胞功能和糖尿病的微管调节

基本信息

批准号：
10597141
负责人：
Guoqiang Gu
金额：
$ 64.31万
依托单位：
VANDERBILT UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2016
资助国家：
美国
起止时间：
2016-03-01 至 2025-03-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10597141
关键词：
Active Biological Transport Address Affect Alpha Cell Anabolism Architecture Beta Cell Binding Proteins Biogenesis Biological Assay Cell Communication Cell Nucleus Cell membrane Cell physiology Cells Centrosome Complex Computer Models Cyclic AMP Cytoplasm Cytoskeleton Data Diabetes Mellitus Dynein ATPase Enhancers Ensure GLP-I receptor Glucagon Glucose Goals Golgi Apparatus Grant Human Hyperinsulinism Hypoglycemia Insulin Intracellular Transport Islet Cell Islets of Langerhans Joints Kinesin Mediating Metabolic Diseases Microscopy Microtubule Bundle Microtubule Polymerization Microtubule-Associated Proteins Microtubules Minus End of the Microtubule Modeling Molecular Molecular Motors Motor Movement Mus Negative Finding Paracrine Communication Peripheral Physiological Physiology Population Positioning Attribute Production Radial Regulation Role Secretory Cell Signal Transduction Site Slide Stimulus Structure Structure of beta Cell of islet Testing Tissues Vesicle blood glucose regulation fighting improved insulin granule insulin secretion intercellular communication islet mathematical model paracrine prevent response tau Proteins tau-1 vesicle transport

项目摘要

In pancreatic islet β cells, insulin granules (IG) are formed at the Golgi complex deep inside the cytoplasm. They need to be actively transported from the site of production to underneath the plasma membrane for regulated secretion. It was previously assumed that MT-dependent transport directionally delivers IGs to the cell periphery along the straight microtubule (MT) tracks, predicting a positive role of MTs in insulin secretion. However, our data over the previous grant cycle show that MT-dependent transport restricts secretion of pre-existing IGs, which are normally present in excessive numbers. We have also found that this negative regulatory function was ascribed to the unique configuration of β-cell MTs. In many other secretory cells, MTs are assembled from the centrosome and organized as radial tracks that allow directional cargo movement. In contrast, most β-cell MTs are nucleated at the Golgi (Golgi-derived MTs, GDMTs) and are organized as a dense, non-directional meshwork in the cell interior, with addition of stable sub-membrane MT bundles at the cell periphery. Experimental tests and mathematical modeling indicate that this configuration leads to trapping of IGs within the cytoplasm, storing them for sustainable insulin release during long-term β-cell function to avoid insulin-insufficiency-induced diabetes. This function also prevents insulin over-secretion at each stimulus to avoid hyperinsulinemia-induced hypoglycemia. Importantly, we show that glucose stimulus triggers reconfiguration of the MT networks: it induces new GDMT nucleation via the cAMP/EPAC2-mediated signals, which is essential for new IG biosynthesis. It also induces MT disassembly in β-cell periphery to enhance insulin secretion by phosphorylating tau, a well-established microtubule associated protein (MAP). However, a big part of intracellular mechanisms that are responsible for β-cell MT organization and its action downstream of glucose remains elusive. Intriguingly, our preliminary data suggest that glucose-induced MT remodeling depends on the islet microenvironment. In this proposal, we will test a hypothesis that optimal dynamic architecture of the β-cell MT networks, modulated by intracellular molecular machinery and intercellular paracrine signals, is essential for β-cell function and glucose homeostasis. By addressing our Specific Aims, we will: (1) investigate building and regulating the unique MT networks in β cells, (2) determine MT-dependent regulation of IG transport and positioning in β cells, and (3) determine roles of MTs in paracrine α-β cell communication in islets.

在胰岛 β 细胞中，胰岛素颗粒 (IG) 在细胞质深处的高尔基复合体中形成，它们需要主动从产生部位转运到膜质下方以进行调节分泌。运输沿着直微管 (MT) 轨道将 IG 定向输送到细胞外周，预测 MT 在胰岛素分泌中发挥积极作用。然而，我们在之前的资助周期中的数据表明，MT 依赖性运输。限制预先存在的 IG 的分泌，而这些 IG 的数量通常过多。我们还发现，这种负调节功能归因于 β 细胞 MT 的独特结构。在许多其他分泌细胞中，MT 是由相比之下，大多数 β 细胞 MT 在高尔基体上成核（高尔基衍生的 MT，GDMT），并在细胞内部组织为致密的非定向网状结构。在细胞外围添加稳定的亚膜 MT 束实验测试和数学模型表明，这种配置会导致 IG 被捕获在细胞质内，并将其储存起来以供可持续使用。长期 β 细胞功能期间的胰岛素释放，以避免胰岛素不足诱发的糖尿病。该功能还可以防止每次刺激时胰岛素过度分泌，以避免高胰岛素血症诱发的低血糖。重要的是，我们表明葡萄糖刺激会触发 MT 网络的重新配置。：它通过 cAMP/EPAC2 介导的信号诱导新的 GDMT 成核，这对于新的 IG 生物合成至关重要。它还诱导 MT 分解。 β 细胞外周通过磷酸化 tau（一种成熟的微管相关蛋白 (MAP)）来增强胰岛素分泌。然而，负责 β 细胞 MT 组织及其在葡萄糖下游的作用的大部分细胞内机制仍然难以捉摸。，我们的初步数据表明，葡萄糖诱导的 MT 重塑取决于胰岛微环境。在本提案中，我们将测试一个假设，即由细胞内调节的 β 细胞 MT 网络的最佳动态结构。分子机制和细胞间旁分泌信号对于 β 细胞功能和葡萄糖稳态至关重要。通过实现我们的具体目标，我们将：(1) 研究构建和调节 β 细胞中独特的 MT 网络，(2) 确定 MT 依赖性调节。 IG 在 β 细胞中的运输和定位，以及 (3) 确定 MT 在胰岛旁分泌 α-β 细胞通讯中的作用。