Bekaert E D, Alaupovic P, Knight-Gibson C, Norum R A, Laux M J, Ayrault-Jarrier M
Lipoprotein and Atherosclerosis Research Program, Oklahoma Medical Research Foundation, Oklahoma City 73104.
Biochim Biophys Acta. 1992 Jun 5;1126(1):105-13. doi: 10.1016/0005-2760(92)90223-i.
High density lipoproteins (HDL) consist of a mixture of chemically and functionally distinct families of particles defined by their characteristic apolipoprotein (Apo) composition. The two major lipoprotein families are lipoprotein A-I (LP-A-I) and lipoprotein A-I:A-II (LP-A-I:A-II). This study describes the isolation of a third minor HDL family of particles referred to as lipoprotein A-II (LP-A-II) because it lacks ApoA-I and contains ApoA-II as its main or sole apolipoprotein constituent. Because ApoA-II is an integral protein constituent of three distinct lipoprotein families (LP-A-I:A-II, LP-A-II: B:C:D:E and LP-A-II), LP-A-II particles were isolated from whole plasma by sequential immunoaffinity chromatography on immunosorbers with antisera to ApoA-II, ApoB and ApoA-I, respectively. In normolipidemic subjects, the concentration of LP-A-II particles, based on ApoA-II content, is 4-18 mg/dl accounting for 5-20% of the total ApoA-II not associated with ApoB-containing lipoproteins. The lipid composition of LP-A-II particles is characterized by low percentage of triglycerides and cholesterol esters and a high percentage of phospholipids in comparison with lipid composition of LP-A-I and LP-A-II: A-II. The major part of LP-A-II particles contain ApoA-II as the sole apolipoprotein constituent; however, small subsets of LP-A-II particles may also contain ApoD and other minor apolipoproteins. The lipid/protein ratio of LP-A-II is higher than those of LP-A-I and LP-A-I:A-II. In homozygous ApoA-I and ApoA-I/ApoC-III deficiencies, LP-A-II particles are the only ApoA-containing high density lipoprotein with levels found to be within the same range (7-13 mg/dl) as those of normolipidemic subjects. However, in contrast to normal LP-A-II, their lipid composition is characterized by higher percentages of triglycerides and cholesterol esters and a lower percentage of phospholipids and their apolipoprotein composition by the presence of ApoC-peptides and ApoE in addition to ApoA-II and ApoD. These results show that LP-A-II particles are a minor HDL family and suggest that, in the absence of ApoA-I-containing lipoproteins, they become an efficient acceptor/donor of ApoC-peptides and ApoE required for a normal metabolism of triglyceride-rich lipoproteins. Their other possible functional roles in lipid transport remain to be established in future experiments.
高密度脂蛋白（HDL）由化学和功能不同的颗粒家族混合组成，这些家族由其特征性载脂蛋白（Apo）组成定义。两个主要的脂蛋白家族是脂蛋白A-I（LP-A-I）和脂蛋白A-I:A-II（LP-A-I:A-II）。本研究描述了第三种较小的HDL颗粒家族的分离，称为脂蛋白A-II（LP-A-II），因为它缺乏ApoA-I，并且含有ApoA-II作为其主要或唯一的载脂蛋白成分。由于ApoA-II是三个不同脂蛋白家族（LP-A-I:A-II、LP-A-II:B:C:D:E和LP-A-II）的完整蛋白质成分，因此通过分别在针对ApoA-II、ApoB和ApoA-I的抗血清免疫吸附剂上进行连续免疫亲和层析，从全血中分离出LP-A-II颗粒。在血脂正常的受试者中，基于ApoA-II含量，LP-A-II颗粒的浓度为4-18mg/dl，占与含ApoB脂蛋白不相关的总ApoA-II的5-20%。与LP-A-I和LP-A-II:A-II的脂质组成相比，LP-A-II颗粒的脂质组成特点是甘油三酯和胆固醇酯的百分比低，磷脂的百分比高。LP-A-II颗粒的主要部分含有ApoA-II作为唯一的载脂蛋白成分；然而，LP-A-II颗粒的小亚群也可能含有ApoD和其他次要载脂蛋白。LP-A-II的脂质/蛋白质比率高于LP-A-I和LP-A-I:A-II。在纯合子ApoA-I和ApoA-I/ApoC-III缺乏症中,LP-A-II颗粒是唯一含ApoA的高密度脂蛋白，其水平与血脂正常的受试者处于同一范围（7-13mg/dl）。然而，与正常的LP-A-II相比，它们的脂质组成特点是甘油三酯和胆固醇酯的百分比更高，磷脂的百分比更低，并且其载脂蛋白组成除了ApoA-II和ApoD外还存在ApoC肽和ApoE。这些结果表明，LP-A-II颗粒是一个较小的HDL家族，并表明在不含含ApoA-I脂蛋白的情况下，它们成为富含甘油三酯脂蛋白正常代谢所需的ApoC肽和ApoE的有效受体/供体。它们在脂质转运中的其他可能功能作用有待在未来实验中确定。
