Deciphering the metabolism of LBPA and its function in the endolysosomal system

解读 LBPA 的代谢及其在内溶酶体系统中的功能

• 批准号: 8802927
• 负责人: Gilbert Di Paolo
• 金额: $ 24万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8802927
• 关键词: Address; Adult; Alzheimer' s Disease; Amyloid beta-Protein; Antibodies; Apolipoproteins; Applications Grants; Autophagocytosis; Biochemical; Biological Assay; Biological Markers; Biology; Blocking Antibodies; Brain region; Cells; Characteristics; Cholesterol; Chronic; Data; Defect; Disease; Employee Strikes; Endosomes; Enzymes; Family; Fluorescence; Frontotemporal Dementia; Functional disorder; Genes; Goals; Hela Cells; Hippocampus (Brain); Hydrolase; In Vitro; Lewy Body Disease; Lipids; Lysosomes; Mass Spectrum Analysis; Mediating; Metabolism; Microscopic; Microscopy; Molecular Genetics; Mus; Mutant Strains Mice; Mutation; Neurodegenerative Disorders; Neurons; Organelles; Parkinson Disease; Pathway interactions; Patients; Peptides; Phospholipids; Physiological; Physiology; Prevention; Process; Proteins; RNA Interference; Reagent; Recombinant Proteins; Role; Sphingolipids; System; Techniques; Technology; Testing; Therapeutic; Tissues; Vesicle; alpha synuclein; base; bis(monoacylglyceryl)phosphate; genome-wide; lipid metabolism; liquid chromatography mass spectrometry; mouse model; mutant; nervous system disorder; public health relevance; synuclein; tau Proteins; tool

DESCRIPTION (provided by applicant): Defects in the endolysosomal system are increasingly viewed as key pathological features of neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease. An emerging hypothesis is that chronic endolysosomal defects occurring in these disorders compromise the degradative capacity of lysosomes, causing the aberrant accumulation of a variety of lysosomal cargoes that are targeted to these organelles generally through the endocytic or autophagy pathway. These cargoes not only include a range of aggregate-prone proteins or peptides (e.g., Abeta, aberrant alpha-synuclein and tau), but also lipids, such as cholesterol and sphingolipids. Recently, our lab has employed a systems-based approach called "lipidomics" to profile hundreds of lipids from healthy and diseased tissue using state-of-the-art mass spectrometry. With this technology, we identified a striking lipid alteration in vulnerable brain regions from patients with AD, in a mouse model of Niemann-Pick type C (NPC), an aggressive lysosomal storage disorder that shares some pathogenic processes in common with AD, as well as in other instances where apolipoprotein-derived cholesterol is aberrantly accumulating. This lipid is called lysobisphosphatidic acid (LBPA) or bis(monoacylglycero) phosphate, an atypical phospholipid that is specifically enriched in the multivesicular endosomes and lysosomes, where it is further concentrated on cholesterol-rich intralumenal vesicles (ILVs). LBPA has been previously suggested to promote the formation of ILVs in the endolysosomal compartment, to regulate the storage and distribution of apolipoprotein-derived cholesterol, and facilitate lysosomal degradation by stimulating hydrolases. Together with these studies, our lipidomic data not only identify LBPA as a candidate biomarker for disorders associated with endolysosomal dysfunction, but they also suggest a critical role for this phospholipid both in the physiology and the pathophysiology of these organelles as well as in the administration of apolipoprotein-derived cholesterol. Unfortunately, tools are currently lacking to understand the precise (patho)physiological roles of this endolysosomal lipid and manipulate its levels to assess its therapeutic potential. The primary reason behind this roadblock is that the enzymes mediating the synthesis and degradation of this elusive phospholipid are unknown. The main goals of this proposal are thus (i) to identify the LBPA-metabolizing enzymes and more generally, the genes positively or negatively regulating the levels of LBPA using a combination of genome-wide RNAi screen and lipidomics; and (ii) to assess the impact of various types of LBPA manipulations on lysosomal function in normal neurons as well as in neurons derived from Npc1 mutant mice. We anticipate that our studies will be critical to understand the role of LBPA in endolysosomal physiology with potentially major implications for disorders associated with lysosomal dysfunction.

描述（由申请人提供）：内溶酶体系统的缺陷越来越被视为神经退行性疾病的关键病理特征，例如阿尔茨海默病（AD）和帕金森病。一个新的假设是，这些疾病中发生的慢性内溶酶体缺陷会损害溶酶体的降解能力，导致通常通过内吞或自噬途径靶向这些细胞器的各种溶酶体货物的异常积累。这些货物不仅包括一系列易于聚集的蛋白质或肽（例如 Abeta、异常 α-突触核蛋白和 tau），还包括脂质，例如胆固醇和鞘脂。最近，我们的实验室采用了一种称为“脂质组学”的基于系统的方法，使用最先进的质谱分析法来分析健康和患病组织中的数百种脂质。通过这项技术，我们在尼曼-匹克 C 型 (NPC) 小鼠模型中发现了 AD 患者脆弱大脑区域的显着脂质变化，NPC 是一种侵袭性溶酶体贮积症，与 AD 具有一些共同的致病过程，以及载脂蛋白衍生的胆固醇异常积累的其他情况。这种脂质称为溶双磷脂酸 (LBPA) 或双（单酰基甘油）磷酸盐，是一种非典型磷脂，专门富集在多囊泡内体和溶酶体中，并进一步集中在富含胆固醇的腔内囊泡 (ILV) 中。 LBPA 先前已被认为可促进内溶酶体室中 ILV 的形成，调节载脂蛋白衍生胆固醇的储存和分布，并通过刺激水解酶促进溶酶体降解。与这些研究一起，我们的脂质组学数据不仅将 LBPA 确定为与内溶酶体功能障碍相关的疾病的候选生物标志物，而且还表明这种磷脂在这些细胞器的生理学和病理生理学以及载脂蛋白衍生胆固醇的管理中发挥着关键作用。不幸的是，目前缺乏工具来了解这种内溶酶体脂质的精确（病理）生理作用并操纵其水平来评估其治疗潜力。这一障碍背后的主要原因是介导这种难以捉摸的磷脂的合成和降解的酶尚不清楚。因此，该提案的主要目标是 (i) 结合全基因组 RNAi 筛选和脂质组学来识别 LBPA 代谢酶，更一般地说，识别正向或负向调节 LBPA 水平的基因； (ii) 评估不同类型的 LBPA 操作对正常神经元以及 Npc1 突变小鼠神经元溶酶体功能的影响。我们预计，我们的研究对于理解 LBPA 在内溶酶体生理学中的作用至关重要，对与溶酶体功能障碍相关的疾病具有潜在的重大影响。