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

• 批准号: 10366019
• 负责人: Guoqiang Gu
• 金额: $ 65.86万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 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/10366019
• 关键词: Active Biological Transport; Address; Affect; Anabolism; Architecture; B-Lymphocyte Subsets; Beta Cell; Binding Proteins; Biogenesis; Biological Assay; Cell Communication; Cell Nucleus; Cell membrane; Cell physiology; Cells; Centrosome; Complex; Computer Models; Cyclic AMP; Cytoplasm; 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; Membrane; Metabolic Diseases; Microscopy; Microtubule Bundle; Microtubule-Associated Proteins; Microtubules; Minus End of the Microtubule; Modeling; Molecular; Molecular Motors; Motor; Movement; Mus; Names; Paracrine Communication; Peripheral; Physiological; Physiology; Polymers; 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; fight against; improved; insulin granule; insulin regulation; insulin secretion; intercellular communication; islet; mathematical model; paracrine; prevent; response; tau Proteins; tau-1; vesicle transport

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）形成于细胞质深处的高尔基复合体处。它们需要从生产部位主动运输到质膜下以调节分泌。先前假设MT依赖性转运将IGs沿沿着直微管（MT）轨道定向递送至细胞外周，预测MT在胰岛素分泌中的积极作用。然而，我们在上一个资助周期的数据显示，MT依赖性转运限制了预先存在的IG的分泌，这些IG通常存在于过量的数量中。我们还发现这种负调节功能归因于β细胞MT的独特构型。在许多其他分泌细胞中，MT是由 中心体，并组织为放射状轨道，允许定向货物运动。相比之下，大多数β细胞MT在高尔基体（高尔基体衍生的MT，GDMT）处成核，并且在细胞内部组织为致密的、非定向的网状结构，在细胞外周处添加稳定的亚膜MT束。实验测试和数学建模表明，这种构型导致IG被捕获在细胞质内，将它们储存起来用于长期β细胞功能期间的可持续胰岛素释放，以避免胰岛素不足诱导的糖尿病。该功能还可防止每次刺激时胰岛素过度分泌，以避免高胰岛素血症诱导的低血糖。重要的是，我们发现葡萄糖刺激触发MT网络的重构：它通过cAMP/EPAC 2介导的信号诱导新的GDMT成核，这对新的IG生物合成至关重要。它还通过磷酸化tau（一种公认的微管相关蛋白（MAP））诱导β细胞外周中的MT分解以增强胰岛素分泌。然而，负责β细胞MT组织及其葡萄糖下游作用的大部分细胞内机制仍然是难以捉摸的。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。在这个提议中，我们将测试一个假设，即由细胞内分子机制和细胞间旁分泌信号调节的β细胞MT网络的最佳动态结构对于β细胞功能和葡萄糖稳态是必不可少的。通过解决我们的具体目标，我们将：（1）研究β细胞中独特的MT网络的构建和调节，（2）确定β细胞中IG转运和定位的MT依赖性调节，以及（3）确定MT在胰岛中旁分泌α-β细胞通讯中的作用。