Multi-cellular interactions and dynamics underlying pancreatic islet function

项目摘要。 胰岛是位于胰腺内的多细胞微器官。这是维持 通过分泌激素如胰岛素和胰高血糖素维持血糖稳态。之间的相互作用 胰岛中的细胞对于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 胰岛分泌胰岛素，与分离β细胞相比，GSIS应答增加许多倍。 此外，胰岛中的β细胞表现出同步振荡，这导致来自胰岛的脉动胰岛素。 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 和维持胰岛素敏感性。强调了胰岛内结构和信号传导的重要性 1型糖尿病可以通过移植完整的胰岛（但不能通过 分离的β细胞）。先前的研究和初步数据表明，间隙连接耦合具有 胰岛功能的生理作用。然而，其他研究也显示了旁分泌和 细胞间通讯中的阿曲他克林机制。我们假设它主要是间隙连接偶联， 电活性，其用于协调和增强GSIS，但cAMP介导的信号传导的偶联 胰岛内α和β细胞之间的相互作用可以进一步调节GSIS。为了验证这一假设， 需要引入精确的实验扰动，并使用定量技术来监测 从而影响GSIS的信号通路。在本提案的指导阶段，我们将 建立必要的生理和生化测定，以及完善定量 目前使用的数学模型。两个具体目标，然后提出了独立的研究 阶段：1）定量间隙连接偶联和KATP通道调节膜极化的相对作用 在调节GSIS中，2）确定β细胞之间cAMP信号传导偶联的机制和作用 和胰岛内的α细胞。这两个目标可以独立进行，尽管每个目标的结果 目标将是补充测试的整体假设。实验将在一些间隙上进行 连接敲除和KATP通道转基因小鼠模型以及人类胰岛，并将利用 现有技术的定量成像方法、荧光蛋白生物传感器和数学模型沿着 更成熟的生化和生理分析。这些实验将产生一个更完整的 了解胰岛内的信号传导机制，这对发展 1型糖尿病的移植和干细胞疗法以及鉴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.