Mechanisms of non-cell-autonomous regulation of brain protein aggregation in Drosophila

果蝇脑蛋白聚集的非细胞自主调节机制

• 批准号: 9791153
• 负责人: Leo J Pallanck
• 金额: $ 38.88万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-30 至 2021-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9791153
• 关键词: Alzheimer' s Disease; American; Autophagocytosis; Biological; Biology; Brain; Cells; Ceramides; Disease; Drosophila genus; Ectopic Expression; Enzymes; Exhibits; Gaucher Disease; Genes; Genetic; Glucose; Glucosylceramides; Goals; Impairment; Individual; Lead; Lewy Body Dementia; Lipids; Longevity; Measures; Mediating; Medical; Memory impairment; Mitochondria; Modeling; Muscle; Mutation; Nerve Degeneration; Neurodegenerative Disorders; Orthologous Gene; Parkinson Disease; Pathogenesis; Pathway interactions; Peripheral; Phenotype; Play; Prion Diseases; Process; Production; Proteins; Proteomics; Regulation; Risk Factors; Role; Sphingolipids; Stable Isotope Labeling; Testing; Therapeutic Intervention; Tissues; Transplantation; Ursidae Family; Work; age related neurodegeneration; brain tissue; experimental study; extracellular vesicles; fly; genetic approach; glucosylceramidase; knock-down; locomotor deficit; mutant; novel; parkin gene/protein; prevent; protein aggregate; protein aggregation; relating to nervous system; virtual

Accumulation of brain protein aggregates is a hallmark of Alzheimer’s disease and many other neurodegenerative disorders. Brain protein aggregation was originally assumed to be a cell-autonomous phenomenon in Alzheimer’s disease, but increasing evidence indicates that non–cell-autonomous processes also play major roles by promoting the spread of toxic aggregation-prone proteins. Although the principal components of the brain protein aggregates that accumulate in Alzheimer’s disease victims have been detected in extracellular vesicles (EVs), the mechanisms underlying the spread of protein aggregates in Alzheimer’s disease are poorly understood. Recent work in our lab suggests that the GBA gene plays an important role in this process. GBA encodes the lysosomal enzyme glucocerebrosidase, which catalyzes the conversion of the sphingolipid glucosylceramide to glucose and ceramide. Mutations in GBA cause several neurodegenerative diseases characterized by the accumulation of protein aggregates in the brain. To study the mechanisms by which mutations in GBA cause disease, we created a Drosophila model of glucocerebrosidase deficiency by deleting the Drosophila GBA ortholog, GBA1b. GBA1b mutants accumulate ubiquitinated protein aggregates, show age-related neurodegeneration, have changes in the turnover and abundance of EV proteins and exhibit a six-fold elevation in EV abundance. Furthermore, ectopic expression of GBA1b in peripheral tissues such as muscle or gut rescued protein aggregation in the brain. These findings lead us to hypothesize that mutations in GBA1b result in lipidomic alterations promoting the overproduction of extracellular vesicles that spread protein aggregates from peripheral tissues to the brain and possibly between cells in the brain. To test this hypothesis and explore the underlying mechanisms, we propose three aims. First, we will test whether the non–cell-autonomous rescue of brain protein aggregation in GBA1b mutants is mediated by extracellular vesicles, and whether this pathway influences the protein aggregates seen in other common neurodegenerative diseases, including Alzheimer’s disease. Second, we will test whether GBA1b mutants promote the spread of endogenous protein aggregates, as well as those seen in Alzheimer’s and prion disease, by blocking the production of EVs in GBA1b mutants and by transplanting EVs from GBA1b mutants to WT flies. Third, we will perform proteomic, lipidomic and cell biological experiments to explore how mutations in GBA1b alter extracellular vesicle formation and composition. Given the increasing evidence of peripheral influences on the spread of brain protein aggregates in Alzheimer’s disease and other neurodegenerative disorders, we anticipate that our findings will advance our understanding of this phenomenon and also create novel opportunities for therapeutic intervention in these diseases.

大脑蛋白质聚集体的积累是阿尔茨海默病和许多其他神经退行性疾病的标志。脑蛋白聚集最初被认为是阿尔茨海默病中的一种细胞自主现象，但越来越多的证据表明，非细胞自主过程也通过促进有毒聚集倾向蛋白的扩散发挥着重要作用。尽管在细胞外囊泡（EV）中检测到了阿尔茨海默病患者体内积累的大脑蛋白质聚集体的主要成分，但人们对阿尔茨海默病中蛋白质聚集体传播的机制知之甚少。我们实验室最近的工作表明 GBA 基因在此过程中发挥着重要作用。 GBA 编码溶酶体酶葡萄糖脑苷脂酶，该酶催化鞘脂葡萄糖神经酰胺转化为葡萄糖和神经酰胺。 GBA 突变会导致多种神经退行性疾病，其特征是大脑中蛋白质聚集物的积累。为了研究 GBA 突变引起疾病的机制，我们通过删除果蝇 GBA 直系同源物 GBA1b，创建了葡萄糖脑苷脂酶缺陷的果蝇模型。 GBA1b突变体积累泛素化蛋白聚集体，表现出与年龄相关的神经退行性变，EV蛋白的更新和丰度发生变化，并且EV丰度增加六倍。此外，GBA1b 在肌肉或肠道等外周组织中的异位表达挽救了大脑中的蛋白质聚集。这些发现使我们推测 GBA1b 的突变会导致脂质组学的改变，促进细胞外囊泡的过度产生，从而将蛋白质聚集体从周围组织传播到大脑，并可能在大脑细胞之间传播。为了检验这一假设并探索潜在机制，我们提出了三个目标。首先，我们将测试 GBA1b 突变体中脑蛋白聚集的非细胞自主拯救是否是由细胞外囊泡介导的，以及该途径是否影响其他常见神经退行性疾病（包括阿尔茨海默病）中的蛋白质聚集。其次，我们将通过阻断 GBA1b 突变体中 EV 的产生以及将 GBA1b 突变体中的 EV 移植到 WT 果蝇中，来测试 GBA1b 突变体是否促进内源性蛋白质聚集体的传播，以及阿尔茨海默氏症和朊病毒病中所见的扩散。第三，我们将进行蛋白质组学、脂质组学和细胞生物学实验，以探索 GBA1b 的突变如何改变细胞外囊泡的形成和组成。鉴于越来越多的证据表明外周因素对阿尔茨海默病和其他神经退行性疾病中脑蛋白聚集体的传播产生影响，我们预计我们的发现将增进我们对这一现象的理解，并为这些疾病的治疗干预创造新的机会。