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FTLD TDP-43包裹体。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以异源二聚体的形式与溶酶体通讯 异丙皂苷(PSAP)。PSAP调节鞘磷脂的水平，这是一类重要的脂类，在体内发挥作用。 细胞信号转导、膜转运和细胞凋亡。PGRN单倍体缺陷对蛋白表达的特异性影响 酶生物学，鞘脂代谢，以及PGRN和PSAP如何协调调节蛋白质和脂类。 动态平衡在很大程度上仍然没有得到解决。我们的目标是通过描绘建筑群来填补这些重大的知识空白， PGRN及其切割产物对溶酶体功能的下游影响。我们的长期目标是- 了解衰老和疾病相关的溶酶体功能障碍如何促进神经退行性疾病。在这 应用，我们的总体目标是确定PGRN单倍体不足如何影响下游流程 如蛋白酶和鞘磷脂酶活性、TDP-43和鞘脂分解，以及总蛋白质和 脂质动态平衡。我们的中心假设是，通过调节CTSD活性，PGRN单倍体不足- FERS对蛋白质和脂肪代谢造成“双重打击”，会损害TDP-43和鞘磷脂的降解。 最终导致溶酶体功能和细胞健康的负面下游后果。Ra- 我们工作的基础是通过了解PGRN、PSAP及其切割产物如何调节蛋白质 和脂质代谢，我们将获得对神经退行性疾病病理生理机制的关键见解。 学。因此，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降解和蛋白质动态平衡；2)了解PGRN及其受体的影响 裂解产物对皂苷产量、鞘磷脂水平和脂质动态平衡的影响；3)询问效果。 人源化模型中PGRN单倍体缺陷对溶酶体蛋白水解酶和脂酶途径的影响。vt.在.的基础上 成功完成拟议的研究，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和鞘磷脂 分解，以及整体蛋白质和脂肪的动态平衡。这一贡献意义重大，因为它将导致 全面了解与PGRN HAP相关的复杂、年龄和疾病相关事件- 肺功能不全。这将进一步转化为更好、更合理地针对FTLD的治疗方法- PGRN，并允许更好地了解溶酶体的基本生物学，以及蛋白酶和鞘磷脂酶如何 以及蛋白质和脂代谢紊乱在FTLD发病机制中的作用。 创世纪。

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 intra- cellular signaling, membrane trafficking and apoptosis. The specific effects of Pgrn haploinsufficiency on prote- ase biology, sphingolipid metabolism and how PGRN and PSAP coordinately regulate protein and lipid home- ostasis 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 under- stand 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, con- fers 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 ra- tionale 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 pathophysi- ology. 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 ef- fects of Pgrn haploinsufficiency 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 hap- loinsufficiency. 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 patho- genesis.