PLTP as a target for lowering VLDL production

 描述(由申请人提供)： 摘要他汀类药物可以治疗高胆固醇血症引起的心血管疾病。然而，有许多不响应和不容忍的情况。因此，迫切需要新的方法来降低血浆低密度脂蛋白，最好是与他汀类药物协同作用。阻断肝脏极低密度脂蛋白是低密度脂蛋白的前体，长期以来一直被认为是降低循环中低密度脂蛋白的有效替代方案。然而，这可能会产生不想要的后果，比如肝脏中的脂肪堆积。因此，在不引起脂质堆积的情况下靶向极低密度脂蛋白的分泌是具有挑战性的，但具有巨大的前景。针对这一建议所做的初步研究表明，肝脏磷脂转移蛋白(PLTP)在调节极低密度脂蛋白(VLDL)分泌从而调节血浆极低密度脂蛋白/低密度脂蛋白(VLDL/LDL)水平方面发挥着重要作用。然而，其中涉及的机制仍不太清楚。肝脏特异性PLTP表达(非过表达)/apoB100纯基因小鼠的建立为我们提供了一个独特的机会来评估肝脏产生的PLTP是否在类似人类的VLDL产生中发挥关键作用。我们的工作假设是：1)PLTP在细胞内极低密度脂蛋白的脂化、转运和翻译后降解中起主要作用，从而促进极低密度脂蛋白的产生；2)。细胞PLTP活性可以受到多种因素的严格调控，呋喃西林(PCSK3)就是其中之一。我们有两个具体目标。目的1：研究肝脏特异性PLTP活性对类人极低密度脂蛋白(VLDL)产生的影响。我们将尝试回答以下问题：1)肝细胞中的极低密度脂蛋白脂化是否需要PLTP活性？2)极低密度脂蛋白运输囊泡(VTV)的形成是否需要PLTP活性？PLTP活性是否能抑制VLDL在肝细胞中的降解。目的：研究Furin介导的PLTP对极低密度脂蛋白(VLDL)产生的影响。我们将描述PLTP和Furin之间的相互作用，特别是它的前段(ProFurin)在体内的作用，并确定这种相互作用对活的极低密度脂蛋白产生的影响。我们还将调查为什么PROFUIN/PLTP介导的极低密度脂蛋白的产生减少不会导致肝脏中的脂肪堆积。我们预计该项目将扩大我们对PLTP和Furin生物学的理解，并为降低血浆VLDL/LDL水平的新策略提供证据，该策略将对人类有效。

 DESCRIPTION (provided by applicant): Summary Hypercholesterinemia-mediated cardiovascular diseases can be treated by statins. However, there are many instances of unresponsiveness and intolerance. Thus, there is urgent need for new approaches to lower plasma LDL, preferably that act synergistically with statins. Blocking liver VLDL, the precursor of LDL, secretion has long been recognized as an effective alternative to lower LDL in the circulation. However, this can have unwanted consequences, such as lipid accumulation in the liver. Therefore, targeting VLDL secretion without causing lipid accumulation is challenging but has great promise. Preliminary studies done for this proposal have revealed an important role of liver phospholipid transfer protein (PLTP) in regulating VLDL secretion, and thereby plasma VLDL/LDL levels. However, the mechanism involved is still not quite clear. The establishment of liver-specific PLTP expression (not overexpression)/apoB100-only mice gives us a unique opportunity to evaluate whether liver-generated PLTP plays a critical role in human-like VLDL production. Our working hypotheses are 1) PLTP plays a major role in intracellular VLDL lipidation, transport, and post-translational degradation, thus promotin VLDL production; 2). Cellular PLTP activity can be tightly regulated by some factors, furin (PCSK3) is one of them. We have two specific aims. Aim 1: To investigate the effect of liver-specific PLTP activity on human-like VLDL production. We will attempt to answer the following questions: 1) Is PLTP activity required for the VLDL lipidation in hepatocytes? 2) Is PLTP activity required for VLDL transport vesicle (VTV) formation? And 3) Does PLTP activity prevent VLDL degradation in hepatocytes. Aim 2: To investigate the impact of furin-mediated PLTP regulation on VLDL production. We will characterize the interaction between PLTP and furin, in particular its pro-segment (profurin) in vivo, and determine the effect of such interaction on live VLDL production. We will also investigate why profurin/PLTP-mediated VLDL less production does not cause lipid accumulation in the liver. We anticipate that this project will broaden our understanding of both PLTP and furin biology and provide evidence for a novel strategy for lowering plasma VLDL/LDL levels that will be effective in humans.