Multi-cellular interactions and dynamics underlying pancreatic islet function

项目总结。 朗格汉斯胰岛是位于胰腺内的多细胞微器官。它是维护 通过分泌胰岛素和胰高血糖素等激素来维持血糖的动态平衡。之间的相互作用 胰岛中的细胞对葡萄糖刺激的胰岛素分泌(GSIS)的调节至关重要。体内的β细胞 与孤立的β细胞相比，胰岛分泌胰岛素的GSIS反应增加了许多倍。 此外，胰岛中的β细胞表现出同步振荡，这导致从 整个胰腺。这些协调的胰岛素脉冲被认为在降低血糖方面更有效 以及维持胰岛素敏感性。强调了胰岛内结构和信号的重要性 因为1型糖尿病可以通过移植完整的胰岛有效地逆转(但不是通过 分离的β细胞)。先前的研究和初步数据表明，缝隙结耦合具有 在胰岛功能中的生理作用。然而，其他研究也显示了旁分泌和 细胞间通讯中的旁分泌机制。我们假设它主要是缝隙结耦合。 协调和增强GSIS的电活动，但cAMP偶联介导的信号 胰岛内的α和β细胞之间可以进一步调节GSIS。为了检验这一假设，它将是 有必要引入精确的实验扰动，并使用定量技术来监测 从而对GSIS潜在的信号通路产生影响。在此建议书的指导阶段，我们将 建立必要的生理和生化分析，以及完善定量 目前正在使用的数学模型。然后提出了独立研究的两个具体目标 阶段：1)量化缝隙连接耦合和KATP通道调节的膜极化的相对作用 在调节GSIS中，2)确定β细胞之间cAMP信号偶联的机制和作用 和胰岛内的阿尔法细胞。这两个目标可以独立进行，尽管每个目标的结果 AIM将对检验整体假设起到补充作用。将在多个GAP上进行实验 连接基因敲除和KATP通道转基因小鼠模型以及人类胰岛，并将利用 ART定量成像方法、荧光蛋白生物传感器和数学模型以及 更成熟的生化和生理化验。这些实验将产生一个更完整的 了解胰岛内的信号机制，这将对发展 1型糖尿病的移植和干细胞疗法以及确定新的治疗药物靶点 治疗2型糖尿病。

Project summary. The islet of Langerhans is a multi-cellular micro-organ located in the pancreas. It is central to maintaining blood glucose homeostasis through secretion of hormones such as insulin and glucagon. Interactions between cells in the islet are crucial to the regulation of glucose stimulated insulin secretion (GSIS). Beta cells within the islet secrete insulin with a many-fold increase in GSIS response compared to isolated beta cells. Furthermore beta cells in the islet exhibit synchronized oscillations which lead to pulsatile insulin from the whole pancreas. These coordinated insulin pulses are thought to be more effective in lowering blood glucose and maintaining insulin sensitivity. The importance of the structure and signaling within the islet is highlighted by the fact that type 1 diabetes can be effectively reversed by the transplantation of intact islets (but not by isolated beta cells). Previous research and preliminary data shows that gap junction coupling has a physiological role in islet function. However other research has also shown possible roles for paracrine and juxtacrine mechanisms in cell-cell communication. We hypothesize that it is primarily gap junction coupling of electrical activity which serves to coordinate and enhance GSIS, but coupling of cAMP mediated signaling between alpha and beta cells within the islet can further modulate GSIS. To test this hypothesis it will be necessary to introduce precise experimental perturbations, and use quantitative techniques to monitor the resulting impact on signaling pathways underlying GSIS. During the mentored phase of this proposal we will establish the necessary physiological and biochemical assays, as well as to refine the quantitative mathematical models currently in use. Two specific aims are then proposed for the independent research phase: 1) quantify the relative role of gap junction coupling and KATP channel regulated membrane polarization in regulating GSIS, 2) determine the mechanism and role for coupling of cAMP signaling between beta cells and alpha cells within the islet. These two aims can proceed independently, although the results from each aim will be complimentary to testing the overall hypothesis. Experiments will be performed on a number of gap junction knockout and KATP channel transgenic mouse models as well as human islets, and will utilize state-of- the art quantitative imaging approaches, fluorescent protein biosensors and mathematical models along with more established biochemical and physiological assays. These experiments will yield a more complete understanding of signaling mechanisms within the islet which will be important for the development of transplantation and stem cell therapies for type1 diabetes as well as identifying novel therapeutic drug targets for type2 diabetes.