Diversity Supplement - Progranulin, Prosaposin and Lipid Biology in FTD

项目总结 原颗粒蛋白基因功能丧失突变(PGRN单倍体不足)导致遗传形式的 含有TDP-43夹杂物的FTLD。PGRN蛋白及其生物活性的切割片段，即“颗粒蛋白”， 直接调节溶酶体蛋白酶组织蛋白酶D(CTSD)的活性。PGRN与溶酶体的通讯 作为与丙皂苷的杂二聚体(PSAP)。PSAP调节神经鞘脂脂的水平，这是一种重要的 一类在细胞内信号传递、膜转运和细胞凋亡中起作用的脂类。具体的 PGRN单倍体缺陷对蛋白水解酶生物学、鞘磷脂代谢及PGRN和HSP70的影响 PSAP协调调节蛋白质和脂肪的动态平衡在很大程度上仍未得到解决。我们的目标是填补 通过描绘PGRN及其下游的复杂影响，这些知识上的主要差距 切割产物对溶酶体功能的影响。我们的长期目标是了解衰老和疾病是如何- 相关的溶酶体功能障碍促进神经退行性疾病。在此应用程序中，我们的总体 目的是确定PGRN单倍体不足如何影响下游过程，如蛋白酶 和鞘脂酶活性、TDP-43和鞘脂分解，以及总蛋白质和脂肪 动态平衡。我们的中心假设是，通过调节CTSD活性，PGRN单倍体不足， 对蛋白质和脂肪代谢造成“双重打击”，从而损害TDP-43和鞘磷脂。 降解，最终导致溶酶体功能和下游的负面影响 细胞健康。我们工作的基本原理是，通过了解PGRN、PSAP和他们的 裂解产物调节蛋白质和脂肪代谢，我们将获得对其机制的关键见解 神经退行性疾病病理生理学。为此，我们提出了以下具体目标：1) 确定PGRN及其切割产物如何影响CTSD介导的TDP-43的破坏和 蛋白质动态平衡；2)了解PGRN及其裂解产物对皂苷的影响 生产，鞘脂水平和脂平衡；3)询问PGRN单倍体充足的影响。 人源化模型中溶酶体蛋白水解酶和脂酶途径的研究。成功后 完成拟议的研究后，我们将了解PGRN如何影响 下游溶酶体过程，如蛋白酶和鞘磷脂酶活性，TDP-43和 鞘脂的分解，以及整体蛋白质和脂肪的动态平衡。这一贡献是巨大的 因为它将导致对复杂的、与年龄和疾病相关的 与PGRN单倍体功能不全相关的事件。这将进一步转化为更好、更理性的 FTLD-PGRN的靶向治疗方法并允许更好地了解FTLD-PGRN的基本生物学 溶酶体、蛋白水解酶和鞘糖脂酶如何协调调节以及功能如何失调 蛋白质和脂类代谢参与FTLD的发病。

PROJECT SUMMARY Loss-of-function mutations in the progranulin gene (Pgrn haploinsufficiency) cause genetic forms of FTLD with TDP-43 inclusions. The PGRN protein and its bioactive cleavage fragments, the “granulins,” directly modulate activity of the lysosomal protease cathepsin D (CTSD). PGRN traffics to the lysosome as a heterodimer with prosaposin (PSAP). PSAP regulates the levels of sphingolipids, an important class of lipids with roles in intracellular signaling, membrane trafficking and apoptosis. The specific effects of Pgrn haploinsufficiency on protease biology, sphingolipid metabolism and how PGRN and PSAP coordinately regulate protein and lipid homeostasis remain largely unaddressed. We aim to fill these major gaps in knowledge by delineating the complex, downstream effects of PGRN and its cleavage products on lysosomal function. Our long-term goal is to understand how aging and disease- associated lysosomal dysfunction promote neurodegenerative disease. In this application, our overall objective is to determine how Pgrn haploinsufficiency impacts downstream processes such as protease and sphingolipidase activity, TDP-43 and sphingolipid breakdown, and overall protein and lipid homeostasis. Our central hypothesis is that Pgrn haploinsufficiency, via modulation of CTSD activity, confers a “double hit” on protein and lipid metabolism, which impairs both TDP-43 and sphingolipid degradation, ultimately leading to negative downstream consequences on lysosomal function and cellular health. The rationale for our work is that by understanding how PGRN, PSAP and their cleavage products regulate protein and lipid metabolism, we will gain key insights into the mechanisms of neurodegenerative disease pathophysiology. Thus, we propose the following specific aims: 1) Determine how PGRN and its cleavage products affect CTSD-mediated TDP-43 breakdown and protein homeostasis; 2) Understand the impact that PGRN and its cleavage products play on saposin production, sphingolipid levels and lipid homeostasis; 3) Interrogate the effects of Pgrn haploinsuffi- ciency on lysosomal protease and lipidase pathways in humanized models. Upon successful completion of the proposed research, we will have gained understanding of how PGRN impacts downstream lysosomal processes such as protease and sphingolipidase activity, TDP-43 and sphingolipid breakdown, and overall protein and lipid homeostasis. This contribution is significant because it will lead to a comprehensive understanding of the complex, age- and disease-associated events associated with Pgrn haploinsufficiency. This will further translate into better, more rationally targeted approaches to therapy in FTLD-Pgrn and allow better understanding of the basic biology of the lysosome, how proteases and sphingolipidases can be coordinately regulated and how dysfunctional protein and lipid metabolism contribute to FTLD pathogenesis.