Investigation of the Molecular Mechanisms of Lipoprotein Lipase Inhibitors

脂蛋白脂酶(LPL)是一种分泌型脂肪酶，是清除循环脂蛋白中甘油三酯的关键酶。由于血浆甘油三酯升高是心血管疾病的独立危险因素，我们寻求提高LPL活性的方法，这将降低血浆甘油三酯。脂蛋白脂酶活性受一类被称为血管生成素样蛋白(ANGPTL)的大分子抑制物家族的下调。该家族包括LPL抑制剂Angptl3、ANGPTL4和ANGPTL8。ANGPTLS功能缺失突变导致LPL活性增加，血清甘油三酯降低。我们在这项研究中的目标是更好地了解ANGPTL是如何与LPL以及它们之间的相互作用的，以便我们能够针对这些相互作用来防止LPL抑制。我们将通过三个具体目标来实现这些目标。在目标1中，我们将建立在我们对Angptl3和ANGPTL4用于抑制LPL的机制的了解的基础上，以确定专门阻断抑制剂-LPL相互作用的新疗法。在目标2中，我们将使用冷冻电子显微镜来解决LPL与其抑制剂结合的结构。最后，在目标3中，我们将研究抑制物在细胞内的功能，以及它们在细胞外的转运。这些目标的成功完成将提供描述LPL及其抑制剂如何结合的分子细节，以及阻止这些相互作用的新方法。由于LPL在调节血浆甘油三酯水平方面的关键作用，这些发现有望为预防心血管疾病提供新的方法。

Lipoprotein lipase (LPL) is a secreted lipase and the key enzyme in clearing triglycerides from circulating lipoproteins. Because elevated plasma triglycerides are an independent risk factor for cardiovascular disease, we seek ways to enhance LPL activity, which will lower plasma triglycerides. LPL activity is downregulated by a family of macromolecular inhibitors known as angiopoietin-like (ANGPTL) proteins. This family includes the LPL inhibitors ANGPTL3, ANGPTL4, and ANGPTL8. Loss-of-function mutations in the ANGPTLs results in increased LPL activity, and decreased serum triglycerides. Our objectives in this study are to better understand how the ANGPTLs associate with LPL, and with each other, so that we can target these interactions to prevent LPL inhibition. We will achieve these objectives in three specific aims. In Aim 1, we will build on our knowledge of the mechanisms used by ANGPTL3 and ANGPTL4 to inhibit LPL to identify new therapeutics that specifically block the inhibitor-LPL interaction. In Aim 2, we will use cryo-electron microscopy to solve structures of LPL bound to its inhibitors. Finally, in Aim 3, we will study the function of inhibitors within cells, and their transport out of cells. Successful completion of these aims will provide molecular details describing how LPL and its inhibitors come together, as well as new ways to block these interactions. Because of LPL's key role in regulating plasma triglyceride levels, these discoveries hold promise for new ways to prevent cardiovascular disease.