Czarnecka H, Yokoyama S
Department of Medicine, University of Alberta, Edmonton, Canada.
Biochemistry. 1995 Apr 4;34(13):4385-92. doi: 10.1021/bi00013a030.
Lecithin:cholesterol acyltransferase (LCAT) reaction was studied in free apolipoprotein-mediated cellular lipid efflux from mouse peritoneal macrophages and human skin fibroblasts. When the cells were incubated with lipid-free human apolipoproteins (apo) A-I or A-II, pre-beta high density lipoprotein (HDL) particles were generated by removing cellular cholesterol and phospholipid. Cholesterol was esterified by LCAT in such particles generated with human apoA-I, but not in those with apoA-II. The reactivity of the apoA-I-pre-beta-HDL particles with LCAT was in the same order as that in human plasma HDL and in phosphatidylcholine/cholesterol unilamellar vesicles activated by apoA-I when compared on the rate of percent cholesterol esterification. However, cholesterol efflux mediated by apoA-I was not enhanced by active cholesterol esterification in the medium from either type of cells. Thus, it is unlikely the LCAT reaction on newly generated pre-beta-HDL directly causes further cellular cholesterol efflux. In control experiments, LCAT esterified cholesterol on human plasma HDL in the cell medium regardless of its origin, either HDL or cells. Cholesterol esterification on HDL was unable to enhance cellular cholesterol efflux significantly but reduced the influx of cholesterol from HDL to cell, resulting in the increase of net efflux of cellular cholesterol, in agreement with the results previously demonstrated.
在游离载脂蛋白介导的小鼠腹腔巨噬细胞和人皮肤成纤维细胞的细胞脂质流出过程中，对卵磷脂胆固醇酰基转移酶（LCAT）反应进行了研究。当细胞与无脂质的人载脂蛋白（apo）A-I或A-II孵育时，通过去除细胞胆固醇和磷脂产生前β高密度脂蛋白（HDL）颗粒。在用人类apoA-I产生的此类颗粒中，胆固醇被LCAT酯化，但在apoA-II产生的颗粒中则不然。当比较胆固醇酯化百分比速率时，apoA-I-前β-HDL颗粒与LCAT的反应性与人类血浆HDL以及由apoA-I激活的磷脂酰胆碱/胆固醇单层囊泡中的反应性顺序相同。然而，由apoA-I介导的胆固醇流出并未因两种细胞类型的培养基中的活性胆固醇酯化而增强。因此，新生成的前β-HDL上的LCAT反应不太可能直接导致进一步的细胞胆固醇流出。在对照实验中，无论细胞培养基中的人类血浆HDL来源是HDL还是细胞，LCAT都会使其中的胆固醇酯化。HDL上的胆固醇酯化不能显著增强细胞胆固醇流出，但会减少胆固醇从HDL流入细胞，导致细胞胆固醇净流出增加，这与先前证明的结果一致。
