Effects of mutant apolipoprotein A-I on the reverse cholesterol transport

人们普遍认为，高密度脂蛋白（HDL）发挥其抗动脉粥样硬化的作用，通过促进过量的胆固醇从外周细胞到肝脏和类固醇生成器官的反向转运。载脂蛋白（apo）A-I与HDL复合，是血浆酶磷脂胆固醇酰基转移酶（LCAT）最有效的激活剂，并增加外周组织胆固醇流出。在我们的实验室中，对10种不同的apo A-I突变进行了表征。在本项目中，通过在大肠杆菌中表达突变和野生型重组proapo（r-proapo）A-I cDNA来检查突变的功能后果。我们产生了四种不同的r-proapo A-I，proapo A-I（Tyr 100 His）加拉津，proapo A-I（Trp108Arg）Tsushima，proapo A-I（Vall 56 Glu）大分，前脱脂蛋白A-I（Glu 235 *0）Nichinan胆固醇流出至r-proapo A-I [^3H]胆固醇标记的乙酰化低密度脂蛋白转化的小鼠腹腔巨噬细胞中的（Glu 235 *0）Nichinan减少了54%正常家兔体内转换研究表明，与正常r-proapo A-I相比，r-proapo A-I Nichinan被快速清除22%。我们得出结论，（Glu 235 *0）Nichinan诱导apo A-I的羧基末端结构域的关键结构变化，用于细胞胆固醇流出和增加apo A-I的催化活性，导致HDL胆固醇水平降低。我们将继续下一个实验，对突变型载脂蛋白A-I进行功能分析。

It is widely assumed that high density lipoproteins (HDL) exert their antiatherogenic role by contributing to the reverse transport of excess cholesterol from peripheral cells to the liver and steoidogenic organs. In complexes with HDL,apolipoprotein (apo) A-I acts as the most potent activator of the plasma enzume lecithin : chlesterol acyltransferase (LCAT) and increases cholesterol efflux from peripheral tissues. In our laboratory, ten different apo A-I mutations were characterized. In this project, functional consequences of the mutation were examined by expressing the mutated and wild-type recombinant proapo (r-proapo) A-I cDNAs in E.coli. We produced four different mutations of r-proapo A-I,proapo A-I (Tyr100His) Karatsu, proapo A-I (Trp108Arg) Tsushima, proapo A-I (Vall56Glu) Oita, proapo A-I (Glu235*0) Nichinan Cholesterol efflux to r-proapo A-I (Glu235*0) Nichinan from mouse peritoneal macrophages converted with [^3H] cholesterol-labeled acetylated LDL was decreased by 54% when compared that of normal r-proapo A-I.In vivo turnover studies in normal rabbits demonstrated that the r-proapo A-I Nichinan was rapidly cleared by 22% compared with normal r-proapo A-I.We conclude that the apo A-I (Glu235*0) Nichinan induced a critical structural change of the carboxyl-terminal domain of apo A-I for cellular cholesterol efflux and increased catabolism of the apo A-I,resulting in low HDL cholesterol level. We are going to continue the next experiment for functional analysis of mutant apo A-I.