Mechanisms of Endosome-to-Lysosome Trafficking in Brain

描述(申请人提供)：内体-溶酶体途径是神经元和其他真核细胞中的一个主要的蛋白分解系统。最近的研究发现，果蝇突变体中内含体到溶酶体的运输受到干扰，导致突触生长异常和神经传递功能受损，这一途径在神经元信号转导和突触功能中的重要性得到了突显。此外，该通路的异常与许多神经疾病和神经退行性疾病的发病机制有关，包括阿尔茨海默病、亨廷顿病和40多种溶酶体储存障碍。尽管内酶体-溶酶体途径在正常生理和疾病中具有重要作用，但控制内酶体向溶酶体转运的分子机制仍不清楚。这项研究的长期目标是在分子水平上了解内吞蛋白是如何被分类并运输到溶酶体进行降解的，以及这一过程是如何在神经和神经退行性疾病中变得失调的。申请人和其他人最近的工作揭示了内体蛋白肝细胞生长因子调节的酪氨酸激酶底物(HRS)在调节内体到溶酶体运输中的关键作用。然而，HRS的作用机制仍不清楚。申请人的初步研究已经鉴定出三种HRS相互作用蛋白，即分类连接蛋白1(SNX1)、信号转导接头分子(STAM)和亨廷顿蛋白相关蛋白1(HAP1)。该项目将检验这一假设，即HRs及其相关蛋白SNX1、STAM和HAP1是内体运输机制的关键组件，该机制控制内吞蛋白的分选和运输到溶酶体进行降解。将结合生化、蛋白质组学、分子生物学和细胞生物学方法来表征HRs相关蛋白复合体，并确定它们在泛素依赖的内切酶到溶酶体运输和神经退行性变中的作用。这些研究结果将有助于我们深入了解神经细胞内小体向溶酶体转运的分子机制，并促进我们对多种神经系统疾病和神经退行性疾病中内小体-溶酶体途径异常的致病机制的理解。

DESCRIPTION (provided by applicant): The endosomal-lysosomal pathway is a major proteolytic system in neurons as well as in other eukaryotic cells. The importance of this pathway in neuronal signaling and synaptic function is highlighted by recent findings that disturbed endosome-to-lysosome trafficking in Drosophila mutants results in abnormal synaptic growth and impaired neurotransmission. Furthermore, aberrations in this pathway have been implicated in the pathogenesis of a number of neurological disorders and neurodegenerative diseases, including Alzheimer's disease, Huntington's disease, and more than 40 lysosomal storage disorders. Despite the critical importance of the endosomal-lysosomal pathway in normal physiology and diseases, the molecular mechanism that controls endosome-to-lysosome trafficking remains poorly characterized. The long-term goal of this research is to understand, at the molecular level, how endocytosed proteins are sorted and transported to lysosomes for degradation, and how this process becomes dysregulated in neurological and neurodegenerative diseases. Recent work by the applicant and others has revealed a crucial role for the endosomal protein hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) in regulating endosome-to-lysosome trafficking. However, the mechanism of action of Hrs remains unclear. The applicant's preliminary studies have identified three Hrs-interacting proteins, sorting nexin 1 (SNXl), signal transducing adaptor molecule (STAM), and huntingtin-associated protein 1 (HAP1). This project will test the hypothesis that Hrs and its associated proteins SNXl, STAM, and HAP1 are key components of the endosomal trafficking machinery that control the sorting and trafficking of endocytosed proteins to lysosomes for degradation. A combination of biochemical, proteomic, molecular biological, and cell biological approaches will be used to characterize Hrs-associated protein complexes and determine their roles in ubiquitin-dependent endosome-to-lysosome trafficking and in neurodegeneration. Results from these studies should generate novel insights into the molecular mechanism governing endosome-to-lysosome trafficking in neurons, and advance our understanding of the pathogenic mechanism of abnormal endosomal-lysosomal pathway in a variety of neurological disorders and neurodegenerative diseases.