Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Can J Physiol Pharmacol. 2009 Oct;87(10):813-20. doi: 10.1139/Y09-055.
We examined whether cardiolipin (CL) synthesis was required to support cholesterol (CH) production from palmitate in Hela cells. Knockdown of human cardiolipin synthase-1 (hCLS1) in Hela cells has been shown to reduce CL synthesis. Therefore Hela cells stably expressing shRNA for hCLS1 and mock control cells were incubated for 16 h with [14C(U)]palmitate bound to albumin (1:1 molar ratio) in the absence or presence of serum. Knockdown of hCLS1 in Hela cells resulted in a reduction in [14C(U)]palmitate incorporation into CL and CH. This reduction in [14C(U)]palmitate incorporation into CH was most pronounced during incubation under serum-free conditions. The reduction in [14C(U)]palmitate incorporation into CH was not due to alterations in total uptake of [14C(U)]palmitate into cells or altered palmitate metabolism, since [14C(U)]palmitate incorporation into phosphatidylcholine, the major [14C(U)]palmitate-containing lipid, and its immediate precursor, 1,2-diacyl-sn-glycerol, were unaffected by hCLS1 knockdown. In addition, knockdown of hCLS1 did not affect CH pool size, indicating that CH catabolism was unaltered. Hydroxymethylglutaryl coenzyme A reductase enzyme activity and its mRNA expression were reduced by knockdown of hCLS1 and this was most pronounced in Hela cells cultured under serum-free conditions. These data indicate that CL synthesis is required to support human de novo CH biosynthesis under conditions of increased demand for CH.
我们研究了心磷脂 (CL) 的合成是否需要支持 Hela 细胞从棕榈酸合成胆固醇 (CH)。已证明人源心磷脂合酶-1 (hCLS1) 的敲低会降低 CL 的合成。因此，用与白蛋白结合的 [14C(U)]棕榈酸 (1:1 摩尔比) 孵育稳定表达 hCLS1 shRNA 的 Hela 细胞和mock 对照细胞 16 小时，在有无血清的情况下进行。hCLS1 在 Hela 细胞中的敲低导致 [14C(U)]棕榈酸掺入 CL 和 CH 的减少。在无血清条件下孵育时，[14C(U)]棕榈酸掺入 CH 的减少最为明显。[14C(U)]棕榈酸掺入 CH 的减少不是由于细胞对 [14C(U)]棕榈酸的总摄取或棕榈酸代谢的改变，因为 [14C(U)]棕榈酸掺入磷脂酰胆碱，即主要的 [14C(U)]棕榈酸含脂质，及其直接前体 1,2-二酰基-sn-甘油，不受 hCLS1 敲低的影响。此外，hCLS1 的敲低不影响 CH 池的大小，表明 CH 分解代谢未改变。羟甲基戊二酰辅酶 A 还原酶酶活性及其 mRNA 表达在 hCLS1 敲低时降低，在无血清培养的 Hela 细胞中最为明显。这些数据表明，在 CH 需求增加的情况下，CL 的合成对于支持人从头合成 CH 是必需的。
