Sorting and Trafficking in the Endosomal System

项目摘要 内体系统由一系列细胞器组成，这些细胞器是由囊泡介导的。 从质膜和高尔基体运输，成熟后与溶酶体融合。 在内体成熟过程中发生的分子分选反应将分子导向溶酶体 降解途径，或进入从内体输出分子以便随后运输的途径 转移到另一个细胞器以供重复使用。后者的“内体循环”和“逆行”转运途径提供了一种 调节质膜的组成，从而调节细胞的特性，以及调节体内细胞器的关键手段 对新陈代谢和环境提示的反应。重要的是，这些途径的基因扰动导致 溶酶体蓄积性疾病、帕金森氏病、阿尔茨海默病、癌症等疾病，提示 对内体进行适当的分类对于预防疾病是至关重要的。这项研究的总体目标是 该项目旨在阐明蛋白质和脂类被分类和运输的机制。 内生体。在之前的资金周期中，我们发现高尔基体逆行通路被用来 调节质膜的组成以响应环境和营养提示，我们 一种名为“逆转录”的可溶性蛋白质分选复合体和磷脂酰肌醇3的效应物-- 在这一过程中，有一种名为Nexin蛋白排序的蛋白。这些组件协同工作，以捕获和 将完整的膜蛋白和脂类货物包装到运输载体中，从萌发和分裂 内生体。拟议的研究将阐明作为分类基础的机械原理和事件 内切溶酶体内完整的膜蛋白和脂类。多样化的实验方法将 被应用于鉴定和表征控制细胞内逆转录酶介导的分选的调节机制， 这些将与生化重建研究相辅相成，这些研究将阐明和排序 逆转聚体及相关蛋白组成的分子功能。更多的研究将阐明 Nexin排序逆转录非依赖循环途径的功能和机制原理。

Project Summary The endosomal system is composed of a continuum of organelles that are derived by vesicle-mediated trafficking from the plasma membrane and Golgi apparatus which mature until fusing with the lysosome. Molecular sorting reactions that take place during endosome maturation direct molecules into the lysosomal degradation pathway, or into pathways that export the molecules from the endosome for subsequent trafficking to another organelle for re-use. The latter ‘endosomal recycling’ and ‘retrograde’ trafficking pathways provide a key means for regulating the composition of the PM, and hence cellular identity, and of internal organelles in response to metabolic and environmental cues. Importantly, genetic perturbations to these pathways result in lysosomal storage diseases, Parkinson’s disease, Alzheimer’s disease, cancer, and other diseases, indicating that proper sorting at the endosome is essential for protection from disease. The broad goal of this research project is to elucidate the mechanisms by which proteins and lipids are sorted and trafficked from the endosome. In previous funding cycles we discovered that Golgi-directed retrograde pathways are used to modulate the composition of the plasma membrane in response to environmental and nutritional cues, and we established roles for a soluble protein sorting complex called ‘retromer’ and effectors of phosphatidylinositol 3- kinase, called sorting nexin proteins, in this process. These components function together to capture and package integral membrane protein and lipid cargo into transport carriers that bud and fission from the endosome. The proposed research will elucidate the mechanistic principles and events that underlie sorting of integral membrane proteins and lipids within the endo-lysosomal system. Diverse experimental approaches will be applied to identify and characterize regulatory mechanisms that control retromer-mediated sorting in cells, and these will be complemented with biochemical reconstitution studies that will elucidate and order the molecular functions of the components of retromer and associated proteins. Additional studies will elucidate the functions and mechanistic principles of retromer-independent recycling pathways by sorting nexins.