Xu Fang, Rychnovsky Scott D, Belani Jitendra D, Hobbs Helen H, Cohen Jonathan C, Rawson Robert B
Center for Human Nutrition, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
Proc Natl Acad Sci U S A. 2005 Oct 11;102(41):14551-6. doi: 10.1073/pnas.0503590102. Epub 2005 Sep 30.
The structural features of sterols required to support mammalian cell growth have not been fully defined. Here, we use mutant CHO cells that synthesize only small amounts of cholesterol to test the capacity of various sterols to support growth. Sterols with minor modifications of the side chain (e.g., campesterol, beta-sitosterol, and desmosterol) supported long-term growth of mutant cells, but sterols with more complex modifications of the side chain, the sterol nucleus, or the 3-hydroxy group did not. After 60 days in culture, the exogenous sterol comprised >90% of cellular sterols. Inactivation of residual endogenous synthesis with the squalene epoxidase inhibitor NB-598 prevented growth in beta-sitosterol and greatly reduced growth in campesterol. Growth of cells cultured in beta-sitosterol and NB-598 was restored by adding small amounts of cholesterol to the medium. Surprisingly, enantiomeric cholesterol also supported cell growth, even in the presence of NB-598. Thus, sterols fulfill two roles in mammalian cells: (i) a bulk membrane requirement in which phytosterols can substitute for cholesterol and (ii) other processes that specifically require small amounts of cholesterol but are not enantioselective.
支持哺乳动物细胞生长所需的固醇类结构特征尚未完全明确。在此，我们使用仅合成少量胆固醇的突变型中国仓鼠卵巢（CHO）细胞来测试各种固醇类支持细胞生长的能力。侧链有微小修饰的固醇类（如菜油固醇、β-谷甾醇和羊毛甾醇）能支持突变细胞的长期生长，但侧链、固醇核或3-羟基有更复杂修饰的固醇类则不能。培养60天后，外源性固醇类占细胞固醇类的90%以上。用鲨烯环氧酶抑制剂NB-598使残余内源性合成失活，可阻止细胞在β-谷甾醇中生长，并大大降低在菜油固醇中的生长。向培养基中添加少量胆固醇可恢复在β-谷甾醇和NB-598中培养的细胞的生长。令人惊讶的是，对映体胆固醇也能支持细胞生长，即使在存在NB-598的情况下也是如此。因此，固醇类在哺乳动物细胞中发挥两种作用：（i）一种大量的膜需求，其中植物甾醇可替代胆固醇；（ii）其他特别需要少量胆固醇但不具有对映体选择性的过程。
