The Role of Microtubule Sliding in Regulation of Insulin Secretion

摘要 糖尿病是一种主要的代谢紊乱疾病，目前在西方影响5-10%的人口。 社会。在占所有糖尿病的90%的2型糖尿病中，胰岛素不被释放到 足够量的血液。胰岛素分泌是胰腺β细胞的功能。β细胞必须 分泌有限剂量的胰岛素，以将血糖降至正常水平，但不能完全 消耗它;这需要细胞内胰岛素储存和分泌之间的紧密协调。我们的数据表明 这种协调是由细胞骨架聚合物微管（MT）调节的，已知微管作为 细胞内高速公路;分子马达如驱动蛋白-1，沿着沿着MT移动以运输和停放膜 细胞器和胰岛素颗粒在特定的细胞位置。我们的实验室已经表明， 胰腺β细胞将胰岛素颗粒抑制在“笼子”中，限制胰岛素颗粒对葡萄糖的利用率， 刺激胰岛素分泌。先前的研究表明，驱动蛋白-1的靶向失活导致 高血糖症，并且作者得出结论，这是由于驱动蛋白-1运输胰岛素的损失。是否 MT网络由这种驱动蛋白重塑和配置也是未知的，因此可能是 潜在的高血糖表型观察到的常规驱动蛋白的靶向失活， 胰腺解决这些笼子的一种可能性是通过驱动蛋白主动转运MT 电机有趣的是，我发现葡萄糖刺激促进了β细胞中新的MT滑动过程。我 假设MT滑动分解“笼状”胰岛素颗粒和/或影响MT网络配置， 胰腺β细胞的正常功能。我的具体目标是（1）确定葡萄糖依赖性 促进MT滑动的途径和机制;（2）阐明MT滑动在MT- 胰岛素释放的依赖性调节。我建议利用高端方法进行高端和超- 分辨率生物成像、计算建模和各种葡萄糖分泌测定来实现这些功能。 目标。发现MT作为β细胞中的调节组分是本领域的一个新的和令人兴奋的课题。 领域

Abstract Diabetes mellitus is a major metabolic disorder currently affecting 5–10% of the population in the western societies. In type-2 diabetes, which accounts for 90% of all diabetes, insulin is not released into the bloodstream in sufficient amounts. Insulin secretion is a function of pancreatic beta cells. Beta cells have to secrete restricted doses of insulin, in order to reduce blood sugar to normal levels but do not completely deplete it; this requires tight coordination between intracellular insulin storage and secretion. Our data indicate that this coordination is regulated by cytoskeletal polymers microtubules (MTs), which are known to serve as intracellular highways; molecular motors such as kinesin-1, move along MTs to transport and park membrane organelles and insulin granules at specific cellular locations. Our lab has shown that the dense MTs in pancreatic beta cells restrain insulin granules in “cages”, restricting insulin granule availability for glucose- stimulated insulin secretion. Previous studies have shown that targeted inactivation of kinesin-1 leads to hyperglycemia and the authors concluded that this is due to loss of trafficking of insulin by kinesin-1. Whether the MT network is remodeled and configured by this kinesin as well is not known and therefore may be part of the underlying hyperglycemic phenotype observed in the targeted inactivation of conventional kinesin in the pancreas. One possibility for resolution of these cages is through the active transport of MTs by a kinesin motor. Interestingly, I have found that glucose stimulation promotes the novel MT sliding process in beta cells. I hypothesize that MT sliding resolves “caged” insulin granules and/or impacts MT network configuration in pancreatic beta cells for their proper function. My specific aims are (1) to determine glucose-dependent pathways and mechanisms that facilitate MT sliding and (2) to elucidate the role of MT sliding in MT- dependent regulation of insulin release. I proposed to utilize high-end approaches for high- and super- resolution biological imaging, computational modeling, and various glucose secretion assays to achieve these aims. The discovery of MTs serving as regulatory components in beta cells is a new and exciting topic in the field.