Metherall J E, Waugh K, Li H
Department of Human Genetics, University of Utah, Salt Lake City 84112, USA.
J Biol Chem. 1996 Feb 2;271(5):2627-33. doi: 10.1074/jbc.271.5.2627.
Cells acquire cholesterol through endogenous synthesis and through receptor-mediated uptake of cholesterol-rich low density lipoprotein (LDL). Esterification of LDL-derived cholesterol is catalyzed by acyl-CoA:cholesterol acyltransferase (ACAT) in the endoplasmic reticulum (ER). Progesterone inhibits esterification, and, although the mechanism of inhibition is not completely understood, this inhibition results from progesterone's ability to inhibit the activity of multiple drug resistance (MDR) P-glycoproteins (P. DeBry and J. E. Metherall, submitted for publication). In the current manuscript, we demonstrate that progesterone inhibits cholesterol biosynthesis resulting in the accumulation of a number of sterol precursors. In Chinese hamster ovary (CHO) cells, high concentrations (100 microM) of progesterone completely blocked cholesterol production, resulting in the accumulation of lanosterol and a lanosterol precursor. Lower concentrations (40 microM) of progesterone cause plasma membrane accumulation of several sterol products. The majority of these sterols are precursors of cholesterol since they were efficiently converted to cholesterol upon removal of progesterone from the culture medium. Although very high concentrations (> 200 microM) of progesterone killed CHO cells, their growth was restored by the addition of cholesterol to the growth medium, indicating that progesterone toxicity resulted from cholesterol auxotrophy. The effect of progesterone was not unique to CHO cells; progesterone also inhibited cholesterol biosynthesis in all human cell lines tested. These observations suggest that a common progesterone-sensitive pathway is involved in both cholesterol biosynthesis and the processing of LDL-derived cholesterol.
细胞通过内源性合成以及通过受体介导摄取富含胆固醇的低密度脂蛋白（LDL）来获取胆固醇。在内质网（ER）中，LDL衍生胆固醇的酯化由酰基辅酶A：胆固醇酰基转移酶（ACAT）催化。孕酮抑制酯化作用，尽管抑制机制尚未完全明确，但这种抑制是由于孕酮能够抑制多药耐药（MDR）P-糖蛋白的活性（P. DeBry和J. E. Metherall，待发表）。在本手稿中，我们证明孕酮抑制胆固醇生物合成，导致多种固醇前体积累。在中国仓鼠卵巢（CHO）细胞中，高浓度（100 microM）的孕酮完全阻断胆固醇生成，导致羊毛甾醇及其前体积累。较低浓度（40 microM）的孕酮导致几种固醇产物在质膜积累。这些固醇中的大多数是胆固醇的前体，因为在从培养基中去除孕酮后它们能有效地转化为胆固醇。尽管极高浓度（> 200 microM）的孕酮会杀死CHO细胞，但通过在生长培养基中添加胆固醇可恢复其生长，这表明孕酮毒性是由胆固醇营养缺陷引起的。孕酮的作用并非CHO细胞所特有；孕酮在所有测试的人类细胞系中也抑制胆固醇生物合成。这些观察结果表明，一个共同的孕酮敏感途径参与胆固醇生物合成和LDL衍生胆固醇的加工过程。
