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.

脑蛋白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。脑蛋白质聚集最初被认为是阿尔茨海默病中的细胞自主现象，但越来越多的证据表明，非细胞自主过程也通过促进毒性聚集倾向蛋白质的传播而发挥重要作用。虽然在阿尔茨海默病患者中积累的脑蛋白质聚集体的主要成分已经在细胞外囊泡（EV）中检测到，但对阿尔茨海默病中蛋白质聚集体扩散的潜在机制知之甚少。我们实验室最近的工作表明，GBA基因在这一过程中起着重要作用。GBA编码溶酶体酶葡糖脑苷脂酶，其催化鞘脂葡糖神经酰胺转化为葡萄糖和神经酰胺。GBA突变导致几种神经退行性疾病，其特征在于蛋白质聚集体在脑中的积累。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乏的果蝇模型。GBA1b突变体积累泛素化蛋白聚集体，表现出年龄相关的神经退行性变，EV蛋白的周转和丰度发生变化，EV丰度升高6倍。此外，GBA1b在外周组织如肌肉或肠道中的异位表达挽救了大脑中的蛋白质聚集。这些发现使我们假设GBA1b突变导致脂质组学改变，促进细胞外囊泡的过度产生，这些囊泡将蛋白质聚集体从外周组织传播到大脑，并可能在大脑细胞之间传播。为了验证这一假设并探索潜在的机制，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由细胞外囊泡介导，以及这种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）中的蛋白聚集体。其次，我们将测试GBA1b突变体是否促进内源性蛋白质聚集体的传播，以及在阿尔茨海默病和朊病毒病中看到的那些，通过阻断GBA1b突变体中EV的产生和将EV从GBA1b突变体移植到WT果蝇中。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，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受到外周影响，我们预计我们的研究结果将促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。