Perilipins and cellular triacyglycerol metabolism

描述(申请人提供)：肥胖是全世界一个严重的健康问题，并导致II型糖尿病、心血管疾病和癌症的患病率增加。尽管需要治疗肥胖症的方法，但人们对脂肪细胞储存和释放脂肪的调节机制知之甚少。三酰甘油(Tag)是人体主要的能量储存形式，它被包裹在脂肪细胞中的脂滴中，被Perilipin A覆盖，Perilipin A是一种蛋白质，在控制Tag的储存和脂肪分解以释放作为主要能量来源的脂肪酸方面发挥关键作用。拟议的研究将阐明Perilipin A协调脂肪细胞Tag代谢的分子机制。初步研究表明，激素敏感脂肪酶(HSL)和CGI-58是一种对TAG代谢很重要的蛋白质，它们通过与Perilipin A的磷酸化状态反应的机制与脂滴联系。拟议的研究将检验以下假设：1)Perilipin A的磷酸化通过多种互补机制控制脂肪分解，以及2)Perilipin A作为一个组织中心，以响应脂肪细胞的脂解状态的方式协调Tag分解代谢酶与脂滴的联系。具体地说，我们将1)阐明Perilipin A促进HSL对接在脂滴上的机制，2)确定磷酸化的Perilipin A协调脂解作用的其他机制，这些机制与其促进HSL对接的作用不同，以及3)阐明Perilipin A在对接脂滴上CGI-58所起的作用以及这种功能相互作用对Tag代谢的影响。完整和突变的Perilipins和HSL或CGI-58将在缺乏这些蛋白的培养细胞中表达，随后将进行标签存储和脂解分析；此外，还提出了RNAi方法和重组蛋白的体外研究。这些研究将有助于确定控制脂肪细胞标签代谢的脂滴因素的长期目标。

DESCRIPTION (provided by applicant): Obesity is a serious health problem throughout the world, and contributes to an increased prevalence of Type II diabetes, cardiovascular disease, and cancer. Despite a need for therapeutic options to treat obesity, little is known about the mechanisms that regulate fat storage and release from adipocytes. Triacylglycerols (TAG), the body's major storage form of energy, are packaged in lipid droplets in adipocytes that are covered with perilipin A, a protein that plays a critical role in controlling TAG storage and lipolysis to release fatty acids that serve as a major source of energy. The proposed studies will elucidate the molecular mechanisms by which perilipin A coordinates adipocyte TAG metabolism. Preliminary studies have provided evidence that hormone-sensitive lipase (HSL), and CGI-58, a protein important for TAG metabolism, associate with lipid droplets via a mechanism that is responsive to the phosphorylation state of perilipin A. The proposed studies will test the hypotheses that 1) the phosphorylation of perilipin A controls lipolysis through multiple complementary mechanisms, and 2) that perilipin A serves as an organizing center that coordinates the association of TAG catabolic enzymes with lipid droplets in a manner that is responsive to the lipolytic status of the adipocyte. Specifically, we will 1) elucidate the mechanisms by which perilipin A facilitates the docking of HSL on lipid droplets, 2) identify additional mechanisms by which phosphorylated perilipin A coordinates lipolysis that are distinct from its role in facilitating HSL docking, and 3) elucidate the role that perilipin A plays in docking CGI-58 on lipid droplets and the consequences of this functional interaction to TAG metabolism. Intact and mutated perilipins and HSL or CGI-58 will be expressed in cultured cells that lack these proteins followed by assays for TAG storage and lipolysis; additionally, RNAi approaches and in vitro studies of recombinant proteins are proposed. These studies will contribute to a long-term goal of defining the factors on lipid droplets that control adipocyte TAG metabolism.