A Simple Cellular Model for Lipodystrophy

脂肪营养不良的简单细胞模型

• 批准号: 8728912
• 负责人: JOEL M GOODMAN
• 金额: $ 31.8万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2017-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8728912
• 关键词: Adipose tissue; Affect; Age; Animal Model; BSCL2 gene; Back; Binding; Biological; Biological Models; Biology; Cardiovascular system; Cell model; Cell physiology; Cells; Cellular biology; Cessation of life; Cytoplasm; Endoplasmic Reticulum; Ensure; Enzymes; Equilibrium; Esters; Eukaryotic Cell; Familial generalized lipodystrophy; Fatty Acids; Fatty Liver; Fatty acid glycerol esters; Genes; Genetic; Genome; Growth; Health; Histocompatibility Testing; Human; Individual; Knowledge; Lead; Lipase; Lipids; Lipodystrophy; Liver diseases; Maintenance; Mammalian Cell; Mediating; Membrane; Metabolic; Modeling; Molecular; Mutate; Mutation; Neurofibrillary Tangles; Obesity; Organelles; Organism; Outcome; Pathway interactions; Patients; Phenotype; Phospholipids; Play; Process; Proteins; Reagent; Reporting; Role; Saccharomyces cerevisiae; Site; Societies; Specificity; Surface; System; Time; Triglycerides; Variant; Work; Yeasts; base; cell type; cost; deprivation; human disease; monolayer; mutant; new technology; novel; oxidation; peroxisome; protein transport; public health relevance; synthetic enzyme; systems research; trafficking

DESCRIPTION (provided by applicant): A primary role of adipose tissue is to store fat in lipid droplets. Storage of triacylglycerol (TAG) and steryl esters, the main components of stored fat, not only provides energy in times of caloric deprivation; it also protects the organism from lipotoxicity. However, adipose tissue has a limited capacity for fat storage, and many obese individuals have exceeded it, leading to fatty liver disease and a variety of cardiovascular, immunological and metabolic imbalances with serious negative health outcomes and great cost to society. In contrast, some individuals cannot store any fat properly, a condition known as lipodystrophy; health outcomes of these patients are even more serious and often lead to death at an early age. The most severe form of lipodystrophy is the fault of mutations in the gene that encodes seipin. Considering the negative outcomes and the costs associated with poor fat storage, it is surprising that there are huge gaps in our basic knowledge of this process. Lipid droplets are not just coalesced neutral lipids in the cytoplasm but are surrounded by a monolayer of phospholipids into which are integrated a constellation of specific proteins; they emanate from the endoplasmic reticulum (ER) and may always be associated with it. To understand fat storage the mechanism of lipid droplet assembly must be known. The key enzymes that produce neutral lipid have been identified but the details of droplet assembly are murky. Fortunately, droplets are made in virtually all eukaryotic cells and can be studied in model organisms. Bakers yeast, Saccharomyces cerevisiae is a great system for this research, since the cells can robustly store lipid in droplets and the organism provides facile genetic and cell biological approaches. We reported the identification of yeast seipin in 2007; it is now clear that it plays an important role in fat storage in yeast as well as humans. We propose to study three basic aspects of droplet assembly using reagents derived from seipin as springboards to understand fundamental biology of fat storage: (1) we have developed a yeast strain in which storage of TAG is exquisitely sensitive to seipin. We shall interrogate this system to understand the molecular mechanism by which seipin catalyzes packaging of TAG and we shall determine whether TAG normally flows between droplets and the connecting ER. (2) We have identified a seipin mutant that apparently causes an imbalance of TAG vs. phospholipid packaging into droplets. We shall determine whether seipin balances the packaging of neutral lipid and phospholipids into the organelle. We shall also screen for suppressors of seipin mutations and use whole genome approaches to uncover novel proteins in droplet assembly. (3) Many lipases reside on lipid droplets where they mobilize fat for energy and export. We have found conditions in which the lipase Tgl3p and others require seipin for localization to droplets. The mechanism by which lipases traffic to droplets and the role of seipin in this process will be determined. Overall, our proposed work will increase our understanding of droplet assembly, the basis of obesity and lipodystrophy, at its most basic level.

描述（由申请人提供）：脂肪组织的主要作用是将脂肪储存在脂滴中。三酰甘油（TAG）和甾醇酯的储存，储存脂肪的主要成分，不仅在热量缺乏时提供能量;它还保护生物体免受脂毒性。然而，脂肪组织的脂肪储存能力有限，许多肥胖个体已经超过了它，导致脂肪肝疾病和各种心血管，免疫和代谢失衡，具有严重的负面健康后果和巨大的社会成本。相比之下，有些人不能正确储存任何脂肪，这种情况被称为脂肪代谢障碍;这些患者的健康状况更为严重，往往导致早期死亡。脂肪代谢障碍最严重的形式是编码seipin的基因突变。考虑到与脂肪储存不良相关的负面结果和成本，令人惊讶的是，我们对这一过程的基本知识存在巨大差距。脂滴不仅仅是细胞质中的中性脂质，而且被单层磷脂包围，磷脂中整合了一系列特定的蛋白质;它们来自内质网（ER），并且可能总是与内质网相关。产生中性脂质的关键酶已经被确定，但液滴组装的细节还不清楚。幸运的是，液滴几乎在所有真核细胞中产生，并且可以在模式生物中进行研究。面包酵母，酿酒酵母是这项研究的一个很好的系统，因为细胞可以在液滴中稳健地储存脂质，并且生物体提供了简单的遗传和细胞生物学方法。我们在2007年报告了酵母Seipin的鉴定;现在已经清楚了 它在酵母和人类的脂肪储存中起着重要作用。我们建议使用来自seipin的试剂作为跳板来研究液滴组装的三个基本方面，以理解脂肪储存的基础生物学：（1）我们已经开发了一种酵母菌株，其中TAG的储存对seipin非常敏感。我们将询问该系统以了解seipin催化TAG包装的分子机制，并且我们将确定TAG是否正常地在液滴和连接ER之间流动。(2)我们已经鉴定了一种seipin突变体，其显然导致TAG与磷脂包装成液滴的不平衡。我们将确定是否seipin平衡包装中性脂质和磷脂进入细胞器。我们还将筛选seipin突变的抑制因子，并使用全基因组方法来发现液滴组装中的新蛋白质。(3)许多脂肪酶驻留在脂滴上，在那里它们动员脂肪用于能量和输出。我们已经发现了脂肪酶Tgl 3 p和其他需要seipin定位到液滴的条件。脂肪酶交通液滴和seipin在这个过程中的作用的机制将被确定。总的来说，我们提出的工作将增加我们对液滴组装的理解，这是肥胖和脂肪代谢障碍的基础，在其最基本的水平。