Volpe J J, Obert K A
J Neurochem. 1982 Apr;38(4):931-8. doi: 10.1111/j.1471-4159.1982.tb05332.x.
Ubiquinone synthesis has been studied in cultured C-6 glial and neuroblastoma cells by utilizing an inhibitor, 3-beta-(2-diethylaminoethoxy) androst-5-en-17-one hydrochloride (U18666A), of cholesterol biosynthesis. Exposure of C-6 glial cells to nanomolar quantities of U18666A caused a marked inhibition of total sterol synthesis from [14C]acetate or [3H]mevalonate within minutes. A 95% inhibition was apparent after a 3-h exposure to 200 ng/ml of U18666A. These observations, together with studies of the incorporation of radioactivity from the two precursors into cholesterol, desmosterol, lanosterol, and squalene, indicated that although the most sensitive site to inhibition by U18666A is desmosterol reduction to cholesterol, a major site of inhibition is demonstrable at a more proximal site, perhaps squalene synthetase. As a consequence of the latter inhibition, exposure of C-6 glial cells to U18666A caused a marked stimulation of incorporation of [14C]acetate or [3H]mevalonate into ubiquinone. Over a wide range of U18666A concentrations, the increase in ubiquinone synthesis was accompanied by an approximately similar decrease in total sterol synthesis. Whereas in the absence of U18666A only approximately 7% of the radioactivity incorporated from [3H]mevalonate into isoprenoid compounds was found in ubiquinone, in the presence of the drug approximately 90% of incorporated radioactivity was found in ubiquinone. The reciprocal effects of U18666A on ubiquinone and sterol syntheses were apparent also in the neuronal cells. THe data thus demonstrate a tight relationship between ubiquinone and sterol biosyntheses in cultured cells of neural origin. In such cells ubiquinone synthesis is exquisitely sensitive to the availability of isoprenoid precursors derived from the cholesterol biosynthetic pathway.
通过利用胆固醇生物合成抑制剂3-β-(2-二乙氨基乙氧基)雄甾-5-烯-17-酮盐酸盐（U18666A），对培养的C-6神经胶质细胞和神经母细胞瘤细胞中的泛醌合成进行了研究。将C-6神经胶质细胞暴露于纳摩尔量的U18666A中，几分钟内就会导致从[14C]乙酸盐或[3H]甲羟戊酸合成总甾醇受到显著抑制。暴露于200 ng/ml的U18666A 3小时后，抑制率达95%。这些观察结果，连同对两种前体的放射性掺入胆固醇、脱氢胆固醇、羊毛甾醇和角鲨烯的研究表明，虽然U18666A抑制的最敏感位点是脱氢胆固醇还原为胆固醇，但一个主要的抑制位点在更靠近上游的位点是可证明的，可能是角鲨烯合酶。由于后者的抑制作用，将C-6神经胶质细胞暴露于U18666A会导致[14C]乙酸盐或[3H]甲羟戊酸掺入泛醌受到显著刺激。在广泛的U18666A浓度范围内，泛醌合成的增加伴随着总甾醇合成大致相似的减少。在不存在U18666A时，从[3H]甲羟戊酸掺入类异戊二烯化合物的放射性中只有约7%存在于泛醌中，而在药物存在的情况下，约90%的掺入放射性存在于泛醌中。U18666A对泛醌和甾醇合成的相互作用在神经元细胞中也很明显。因此，数据证明了神经源性培养细胞中泛醌和甾醇生物合成之间的紧密关系。在这类细胞中，泛醌合成对源自胆固醇生物合成途径的类异戊二烯前体的可用性极为敏感。
