Perilipins and cellular triacyglycerol metabolism

描述（由申请人提供）：肥胖是全世界严重的健康问题，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治疗方案，但对调节脂肪储存和脂肪细胞释放的机制知之甚少。三酰甘油（TAG）是身体主要的能量储存形式，被包装在脂肪细胞中的脂滴中，脂肪细胞被周脂蛋白A覆盖，周脂蛋白A是一种在控制TAG储存和脂解以释放作为主要能量来源的脂肪酸中起关键作用的蛋白质。这些研究将阐明脂周蛋白A协调脂肪细胞TAG代谢的分子机制。初步研究提供了证据表明，对脂滴敏感的脂肪酶（HSL）和CGI-58（一种对TAG代谢很重要的蛋白质）通过一种响应于周脂蛋白A磷酸化状态的机制与脂滴相关。拟议的研究将检验以下假设：1）周脂蛋白A的磷酸化通过多种互补机制控制脂解，2）周脂蛋白A作为组织中心，以响应脂肪细胞脂解状态的方式协调TAG分解代谢酶与脂滴的缔合。具体而言，我们将1）阐明周脂蛋白A促进HSL在脂滴上对接的机制，2）鉴定磷酸化周脂蛋白A协调脂解的其他机制，这些机制与其促进HSL对接的作用不同，以及3）阐明周脂蛋白A在将CGI-58对接在脂滴上中发挥的作用以及这种功能性相互作用对TAG代谢的后果。完整和突变的周脂蛋白和HSL或CGI-58将在缺乏这些蛋白质的培养细胞中表达，然后进行TAG储存和脂解的测定;此外，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TAG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.