The structural basis for cholesterol esterification in human plasma

卵磷脂：胆固醇酰基转移酶(LCAT)催化脂肪酸的酯化反应 胆固醇，是人体内大部分胆固醇酯(CE)的来源 发行量。辅因子载脂蛋白可显著增强其活性，如 载脂蛋白A-I在高密度脂蛋白中，载脂蛋白E在低密度脂蛋白/极低密度脂蛋白和脑脂蛋白中。虽然这件事 辅因子关系已经知道几十年了，我们对载脂蛋白如何 激活LCAT仍然有限。我们的初步工作表明，LCAT与两个 ApoA-I内由一个apoA-I分子中的螺旋4组成的镜像对接位点 和相反分子的螺旋6。当这个注册表被破坏时，LCAT仍然可以绑定HDL 但不再催化CE的形成。我们假设这些停靠点朝向LCAT 与高密度脂蛋白颗粒的脂面有关，并可形成一条管道，通过该管道，颗粒 进入岩芯以沉积CE。此外，我们怀疑这些网站引导了 胆固醇底物通过特定的识别序列与LCAT相互作用的部位。我们 我还认为，另一种高度丰富的高密度脂蛋白载脂蛋白ApoA-II会破坏这一过程 降低LCAT活性的相互作用。利用在我们的 实验室，我们将：1)确定LCAT apoA-I激活的分子机制和 这些相互作用位点的作用，2)决定apoA-II如何减弱LCAT反应和3) 明确载脂蛋白E刺激LCAT的机制。这项工作将回答近50年 载脂蛋白如何增强LCAT调节血浆胆固醇能力的老问题 酯化反应。此外，我们将把这些知识转化为新颖的双螺旋结构的设计 可能构成治疗LCAT遗传部分缺陷个体的基础的多肽 活动，如鱼眼病(FED)。

Lecithin:cholesterol acyl transferase (LCAT) catalyzes the esterification of a fatty acid to cholesterol and is responsible for the majority of cholesteryl ester (CE) in the human circulation. Its activity is dramatically enhanced by cofactor apolipoproteins such as apolipoprotein (apo)A-I in HDL and apoE in LDL/VLDL and brain lipoproteins. While this cofactor relationship has been known for decades, our understanding of how apolipoproteins activate LCAT remains limited. Our preliminary work has shown that LCAT interacts with two mirror image docking sites within apoA-I that are composed of helix 4 in one apoA-I molecule and helix 6 of the opposing molecule. When this registry is disrupted, LCAT can still bind HDL but no longer catalyzes CE formation. We hypothesize that these docking sites orient LCAT with respect to the lipid faces of HDL particles and may form a conduit by which the particle core is accessed for deposition of CE. Additionally, we suspect that these sites direct the cholesterol substrate to the site of LCAT interaction via specific recognition sequences. We also believe that apoA-II, another highly abundant HDL apolipoprotein, disrupts this interaction to reduce LCAT activity. Leveraging new experimental tools developed in our laboratory, we will; 1) define the molecular mechanism for apoA-I activation of LCAT and the role of these interaction sites, 2) determine how apoA-II attenuates the LCAT reaction and 3) define the mechanism behind apoE stimulation of LCAT. This work will answer nearly 50 year old questions about how apolipoproteins enhance LCAT’s ability mediate plasma cholesterol esterification. In addition, we will translate this knowledge into the design of novel bi-helical peptides that may form a basis for treating individuals with genetic partial deficiencies of LCAT activity such as Fish Eye Disease (FED).