Institute of Medical Biochemistry and Molecular Biology, University Medicine Greifswald, University of Greifswald, Ferdinand-Sauerbruch-Str., D-17475 Greifswald, Germany.
Zentrum für Innovationskompetenz: Humorale Immunreaktionen bei kardiovaskulären Erkrankungen, University of Greifswald, Fleischmannstr. 42-44, D-17489 Greifswald, Germany.
Biochim Biophys Acta Mol Cell Biol Lipids. 2019 Apr;1864(4):452-465. doi: 10.1016/j.bbalip.2019.01.006. Epub 2019 Jan 9.
The mitochondrial phospholipid cardiolipin (CL) has been implicated with mitochondrial morphology, function and, more recently, with cellular proliferation. Tafazzin, an acyltransferase with key functions in CL remodeling determining actual CL composition, affects mitochondrial oxidative phosphorylation. Here, we show that the CRISPR-Cas9 mediated knock-out of tafazzin (Taz) is associated with substantial alterations of various mitochondrial and cellular characteristics in C6 glioma cells. The knock-out of tafazzin substantially changed the profile of fatty acids incorporated in CL and the distribution of molecular CL species. Taz knock-out was further associated with decreased capacity of oxidative phosphorylation that mainly originates from impaired complex I associated energy metabolism in C6 glioma cells. The lack of tafazzin switched energy metabolism from oxidative phosphorylation to glycolysis indicated by lower respiration rates, membrane potential and higher levels of mitochondria-derived reactive oxygen species but keeping the cellular ATP content unchanged. The impact of tafazzin on mitochondria was also indicated by altered morphology and arrangement in tafazzin deficient C6 glioma cells. In the cells we observed tafazzin-dependent changes in the distribution of cellular fatty acids as an indication of altered lipid metabolism as well as in stability/morphology. Most impressive is the dramatic reduction in cell proliferation in tafazzin deficient C6 glioma cells that is not mediated by reactive oxygen species. Our data clearly indicate that defects in CL phospholipid remodeling trigger a cascade of events including modifications in CL linked to subsequent alterations in mitochondrial and cellular functions.
线粒体磷脂心磷脂（CL）与线粒体形态、功能有关，最近还与细胞增殖有关。酰基转移酶 Tafazzin 在 CL 重塑中具有关键作用，决定了 CL 的实际组成，影响线粒体氧化磷酸化。在这里，我们表明，CRISPR-Cas9 介导的 tafazzin（Taz）敲除与 C6 神经胶质瘤细胞中各种线粒体和细胞特征的显著改变有关。Taz 敲除显著改变了 CL 中掺入的脂肪酸的分布和分子 CL 种类的分布。Taz 敲除还与氧化磷酸化能力的降低有关，这主要源于 C6 神经胶质瘤细胞中与复合物 I 相关的能量代谢受损。缺乏 tafazzin 将能量代谢从氧化磷酸化切换到糖酵解，表现为呼吸速率、膜电位降低和线粒体来源的活性氧水平升高，但细胞内 ATP 含量不变。tafazzin 对线粒体的影响还表现在 tafazzin 缺陷的 C6 神经胶质瘤细胞中线粒体形态和排列的改变。在这些细胞中，我们观察到 tafazzin 依赖性的细胞内脂肪酸分布的变化，这表明脂质代谢发生了改变，以及稳定性/形态发生了改变。最引人注目的是，在 tafazzin 缺陷的 C6 神经胶质瘤细胞中，细胞增殖显著减少，这不是由活性氧介导的。我们的数据清楚地表明，CL 磷脂重塑缺陷引发了一系列事件，包括与随后的线粒体和细胞功能改变相关的 CL 连接的修饰。
