Peffley D M
University of Tennessee, Memphis, Health Science Center, Department of Pharmacology 38163.
Somat Cell Mol Genet. 1992 Jan;18(1):19-32. doi: 10.1007/BF01233446.
C100 is a baby hamster kidney cell line that expresses high levels of HMG-CoA reductase relative to its parental cell line SV28. In this study the effects of the oxysterol 25-hydroxycholesterol and mevalonate on the mRNA level and rate of synthesis for HMG-CoA reductase were evaluated in C100 cells treated with mevinolin, a competitive inhibitor of HMG-CoA reductase. The addition of 25-hydroxycholesterol to the cell culture medium resulted in a fourfold decrease in both the rate of synthesis and mRNA level for HMG-CoA reductase. Mevalonate at a concentration of 0.4 mM, when added to mevinolin-treated C100 cells, produced no apparent reduction in HMG-CoA reductase mRNA levels and only a small (25%) decline in HMG-CoA synthesis. Mevalonate (0.4 mM) added to 25-hydroxycholesterol-treated cells resulted in no further reduction in the HMG-CoA reductase mRNA level when compared to cells treated with 25-hydroxycholesterol alone, but produced an additional 30-fold decrease in the rate of HMG-CoA reductase synthesis. Degradation of HMG-CoA reductase was rapid in the presence (t1/2 = 1.34 h) or absence (t1/2 = 1.17 h) of mevinolin and was not changed significantly by adding either 25-hydroxycholesterol, alone (t1/2 = 1.30 h) or both 25-hydroxycholesterol and mevalonate (t1/2 = 1.30 h) to mevinolin-treated cells. This study demonstrates that mevalonate and 25-hydroxycholesterol act synergistically in the presence of mevinolin to achieve a greater degree of suppression in the rate of HMG-CoA reductase synthesis than can be accounted for by their individual effects on HMG-CoA reductase mRNA. In addition, the data suggest that mevalonate affects the synthesis of HMG-CoA reductase at a yet unidentified posttranscriptional control site.
C100是一种仓鼠肾细胞系，相对于其亲代细胞系SV28，它能高水平表达HMG-CoA还原酶。在本研究中，在用洛伐他汀（一种HMG-CoA还原酶的竞争性抑制剂）处理的C100细胞中，评估了氧化甾醇25-羟基胆固醇和甲羟戊酸对HMG-CoA还原酶mRNA水平和合成速率的影响。向细胞培养基中添加25-羟基胆固醇导致HMG-CoA还原酶的合成速率和mRNA水平均下降四倍。当向用洛伐他汀处理的C100细胞中添加浓度为0.4 mM的甲羟戊酸时，HMG-CoA还原酶mRNA水平没有明显降低，HMG-CoA合成仅小幅下降（25%）。与仅用25-羟基胆固醇处理的细胞相比，向用25-羟基胆固醇处理的细胞中添加甲羟戊酸（0.4 mM）不会导致HMG-CoA还原酶mRNA水平进一步降低，但会使HMG-CoA还原酶合成速率额外降低30倍。在有（t1/2 = 1.34小时）或无（t1/2 = 1.17小时）洛伐他汀的情况下，HMG-CoA还原酶的降解都很快，并且向用洛伐他汀处理的细胞中单独添加25-羟基胆固醇（t1/2 = 1.30小时）或同时添加25-羟基胆固醇和甲羟戊酸（t1/2 = 1.30小时），HMG-CoA还原酶的降解没有显著变化。本研究表明，在洛伐他汀存在的情况下，甲羟戊酸和25-羟基胆固醇协同作用，比它们对HMG-CoA还原酶mRNA的单独影响能更显著地抑制HMG-CoA还原酶的合成速率。此外，数据表明甲羟戊酸在一个尚未确定的转录后控制位点影响HMG-CoA还原酶的合成。
