Sorting and Trafficking in the Endosomal System

项目摘要 内体系统由连续的细胞器组成，这些细胞器通过囊泡介导的细胞内信号转导而产生。 从成熟的质膜和高尔基体运输，直至与溶酶体融合。 在核内体成熟过程中发生的分子分选反应将分子引导到溶酶体中 降解途径，或进入从内体输出分子用于随后运输的途径 转移到另一个细胞器中重复使用后一种“内体再循环”和“逆行”运输途径提供了一种 调节PM组成的关键手段，因此细胞的身份，和内部细胞器， 对代谢和环境线索的反应。重要的是，这些途径的遗传干扰导致 溶酶体贮积病、帕金森病、阿尔茨海默病、癌症和其他疾病，表明 核内体的正确分类对于防止疾病至关重要。这项研究的主要目标是 该项目的目的是阐明蛋白质和脂质从细胞中分选和运输的机制。 核内体在之前的资助周期中，我们发现高尔基体定向的逆行通路用于 调节质膜的组成，以响应环境和营养线索，我们 被称为“逆转录酶”的可溶性蛋白质分选复合物和磷脂酰肌醇3- 一种叫做分类连接蛋白的激酶。这些组件共同发挥作用， 包装完整的膜蛋白和脂质货物进入运输载体，从芽和分裂 核内体拟议的研究将阐明机械原理和事件的基础排序 内溶酶体系统内的完整膜蛋白和脂质。不同的实验方法将 应用于鉴定和表征控制细胞中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补充，将阐明和排序 retromer和相关蛋白质组分的分子功能。进一步的研究将阐明 通过对连接蛋白的分类，研究了非逆转录酶依赖的再循环途径的功能和机理。

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.