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.

在胰岛胰岛细胞中，胰岛素颗粒（IG）在细胞质深处的高尔基体配合物中形成。它们需要积极地从生产地点运输到质膜下方进行调节的分泌。以前假定依赖MT的转运方向将Ig沿直径微管（MT）轨道传递到细胞外围，从而预测MT在胰岛素分泌中的阳性作用。但是，我们对上一个赠款周期的数据表明，依赖MT的运输限制了现有的IG的分泌，这些分泌通常是多余的。我们还发现，这种负调节功能被分配给β细胞MT的唯一构型。在许多其他秘密细胞中，MT是从中心体和作为径向轨道组织的，可允许方向货物运动。相比之下，大多数β细胞MT在高尔基体（Golgi衍生的MTS，GDMTS）上核mts核，并在细胞内部组织为密集的非方向网格，并添加稳定的亚膜膜MT在细胞外围的MT。实验测试和数学建模表明，这种构型会导致Ig在细胞质中的捕获，并在长期β细胞功能期间将其存储在可持续的胰岛素释放中，以避免胰岛素不适感引起的糖尿病。该功能还可以防止在每种刺激上进行胰岛素过度分泌，以避免胰岛素诱导的低血糖。重要的是，我们表明葡萄糖刺激触发了MT网络的重新配置：它通过CAMP/EPAC2介导的信号诱导新的GDMT核，这对于新的IG生物合成至关重要。它还诱导β细胞周围的MT拆卸，从而通过磷酸化tau（一种已建立的微管相关蛋白（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作用的细胞内机制的很大一部分仍然是弹性的。有趣的是，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。在此提案中，我们将检验一个假设，即β细胞MT网络的最佳动态结构，该网络受细胞内分子机械和细胞间旁分泌信号调节，对于β细胞功能和葡萄糖稳态至关重要。通过解决我们的特定目标，我们将：（1）研究和调节β细胞中唯一的MT网络，（2）确定β细胞中Ig转运和定位的MT依赖性调节，（3）确定MTS在胰岛旁分泌α-β细胞中的作用。