Steinmetz A, Barbaras R, Ghalim N, Clavey V, Fruchart J C, Ailhaud G
SERLIA, Institut Pasteur, Lille, France.
J Biol Chem. 1990 May 15;265(14):7859-63.
Cholesterol efflux was studied in cultured mouse adipose cells after preloading with low density lipoprotein cholesterol. Exposure to complexes containing human apolipoprotein A-IV and L-alpha-dimyristoylphosphatidylcholine (DMPC) as well as to human lipoprotein particles containing apolipoprotein A-IV but not apolipoprotein A-I and particles containing apolipoproteins A-IV and A-I showed that both artificial and native apolipoprotein A-IV-containing particles were able to promote cholesterol efflux at 37 degrees C as a function of time and concentration. The half-maximal concentration was found to be 0.3 X 10(-6) M for apolipoprotein A-IV.DMPC complexes. Binding experiments performed in intact cells at 4 degrees C with labeled apolipoprotein A-IV.DMPC complexes showed the existence of specific binding sites, with a Kd value of 0.32 x 10(-6) M and a maximal binding capacity of 223,000 sites/cell. By cross-competition experiments with labeled and unlabeled complexes containing apolipoprotein A-IV, A-I, or A-II, it appeared that all three apolipoproteins bind to the same cell-surface recognition sites. It is suggested that apolipoprotein A-IV, which is present in the interstitial fluid surrounding adipose cells in vivo at concentrations similar to those required in vitro for the promotion of cholesterol efflux, plays a critical role in cholesterol removal from peripheral cells.
在用低密度脂蛋白胆固醇预加载后，对培养的小鼠脂肪细胞中的胆固醇流出进行了研究。将其暴露于含有人类载脂蛋白A-IV和L-α-二肉豆蔻酰磷脂酰胆碱（DMPC）的复合物以及含有载脂蛋白A-IV但不含载脂蛋白A-I的人类脂蛋白颗粒和含有载脂蛋白A-IV和A-I的颗粒中，结果表明，人工合成的和天然的含载脂蛋白A-IV的颗粒都能够在37℃下促进胆固醇流出，且呈时间和浓度依赖性。载脂蛋白A-IV-DMPC复合物的半最大浓度为0.3×10⁻⁶ M。在4℃下对完整细胞进行的结合实验显示，标记的载脂蛋白A-IV-DMPC复合物存在特异性结合位点，解离常数（Kd）值为0.32×10⁻⁶ M，最大结合容量为223,000个位点/细胞。通过用标记和未标记的含载脂蛋白A-IV、A-I或A-II的复合物进行交叉竞争实验，发现这三种载脂蛋白都与相同的细胞表面识别位点结合。有人提出，在体内脂肪细胞周围的间质液中存在的载脂蛋白A-IV，其浓度与体外促进胆固醇流出所需的浓度相似，在从外周细胞清除胆固醇中起关键作用。
