EFFECTS OF BREFELDIN-A ON SPHINGOMYELIN TRANSPORT AND LIPID-SYNTHESIS IN BHK-21-CELLS
EFFECTS OF BREFELDIN-A ON SPHINGOMYELIN TRANSPORT AND LIPID-SYNTHESIS IN BHK-21-CELLS
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DOI：
10.1042/bj2890307
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发表时间：
1993-01-01
影响因子：
4.1
通讯作者：
ALLAN, D
中科院分区：
文献类型：
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作者：
KALLEN, KJ;QUINN, P;ALLAN, D
1.与未处理的对照相比，向与[H-3]乙酸盐孵育4小时的BHK细胞中添加布雷菲德菌素A（BFA）导致标记物掺入鞘磷脂、单葡糖神经酰胺和胆固醇酯中增加3-4倍。[H-3]胆碱掺入鞘磷脂也有类似的增加。胆固醇酯的水平增加3倍时，添加BFA的细胞标记与[H-3]醋酸平衡，但没有统计学显着变化的其他脂质的水平。2. BFA似乎通过将乙酸转移到鞘脂和胆固醇酯中而起作用，其代价是磷脂酰胆碱（降低高达15%）、胆固醇（降低30- 40%）和三酰甘油（降低35- 50%）。3. Forskolin（100 μ M）阻止0.25 μ g/ml BFA诱导的标记变化，但在1 μ g/ml BFA存在下，它对鞘磷脂和三酰甘油标记没有影响，仅部分阻断BFA对胆固醇和胆固醇酯标记的影响。4.没有标记的鞘磷脂被降解在BFA处理的细胞，随后暴露于细胞外鞘磷脂酶，显示所有新合成的鞘磷脂仍然在细胞内。在未标记的细胞中磷脂磷的测定证实，在BFA的存在下，没有新合成的鞘磷脂能够到达细胞表面，支持鞘磷脂通常依赖于囊泡运输通过质膜的想法。5.结果与BHK细胞中胆固醇合成和酯化过程对BFA引起的鞘磷脂质膜缺陷敏感的假设一致。
1. Addition of brefeldin A (BFA) to BHK cells incubated for 4 h with [H-3]acetate led to a 3-4-fold increase in incorporation of label into sphingomyelin, monoglucosylceramide and cholesterol ester compared with untreated controls. There was a similar increase in incorporation of [H-3]choline into sphingomyelin. The level of cholesterol ester increased 3-fold when BFA was added to cells labelled to equilibrium with [H-3]acetate, but no statistically significant changes in the levels of other lipids were seen. 2. BFA appeared to act by diverting incorporation of acetate into sphingolipids and cholesterol ester at the expense of phosphatidylcholine (decreased by up to 15 %), cholesterol (decreased by 30-40 %) and triacylglycerol (decreased by 35-50 %). 3. Forskolin (100 muM) prevented the changes in labelling induced by 0.25 mug of BFA/ml, but in the presence of 1 mug of BFA/ml it had no effect on sphingomyelin and triacylglycerol labelling and only partly blocked the effects of BFA on labelling of cholesterol and cholesterol ester. 4. None of the labelled sphingomyelin was degraded in BFA-treated cells which were subsequently exposed to an extracellular sphingomyelinase, showing that all the newly synthesized sphingomyelin remained inside the cells. Determinations of phospholipid phosphorus in unlabelled cells confirmed that, in the presence of BFA, no newly synthesized sphingomyelin was able to reach the cell surface, supporting the idea that sphingomyelin normally depends on vesicular transport for its passage to the plasma membrane. 5. The results are consistent with the hypothesis that cholesterol synthesis and esterification processes in BHK cells are sensitive to the plasma-membrane deficit of sphingomyelin caused by BFA.