StarD7 Protein Deficiency Adversely Affects the Phosphatidylcholine Composition, Respiratory Activity, and Cristae Structure of Mitochondria
StarD7 Protein Deficiency Adversely Affects the Phosphatidylcholine Composition, Respiratory Activity, and Cristae Structure of Mitochondria
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DOI：
10.1074/jbc.m116.736793
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发表时间：
2016-11-25
影响因子：
4.8
通讯作者：
Sugimoto, Hiroyuki
中科院分区：
文献类型：
--
作者：
Horibata, Yasuhiro;Ando, Hiromi;Sugimoto, Hiroyuki
磷脂酰胆碱（PC）是线粒体的主要磷脂，占外膜和内膜的40-50%。然而，PC必须从其生产细胞器中输入，因为线粒体缺乏PC生物合成所必需的酶。在先前的研究中，我们发现StarD 7介导PC向线粒体的细胞内转移。因此，在这项研究中，我们分析了StarD 7的贡献，线粒体磷脂含量和功能的维护使用siRNA介导的敲低和敲除（KO）的StarD 7基因在HEPA-1细胞。呼吸活动的真实的时间分析表明，StarD 7-KD细胞的耗氧速率和线粒体复合物的活性受损。为了证实这些结果，我们使用CRISPR/Cas9 n通过双切口建立了StarD 7-KO HEPA-1细胞。如预期的，StarD 7-KD和- KO细胞显示线粒体PC含量显著降低。KO细胞的ATP水平和生长速率显着低于野生型细胞相比，当在无葡萄糖的含半乳糖的培养基中培养，迫使细胞依赖于线粒体ATP的生产。在KO细胞中，MTCO 1蛋白（复合物IV的主要亚基）的水平降低，而其mRNA没有随之降低，但当StarD 7-I过表达时，该水平恢复。StarD 7-KO细胞表现出线粒体超复合物的形成受损，并表现出紊乱的嵴结构，而视神经萎缩1蛋白没有变化。这些发现表明，StarD 7在维持线粒体磷脂的适当组成以及线粒体功能和形态发生方面起着重要作用。
Phosphatidylcholine (PC) is a major phospholipid of mitochondria, comprising 40-50% of both the outer and the inner membranes. However, PC must be imported from its production organelles because mitochondria lack the enzymes essential for PC biosynthesis. In a previous study, we found that StarD7 mediates the intracellular transfer of PC to mitochondria. Therefore, in this study, we analyzed the contribution of StarD7 to the maintenance of mitochondrial phospholipid content and function using siRNA-mediated knockdown and knock-out (KO) of the StarD7 gene in HEPA-1 cells. Real time analysis of respiratory activity demonstrated that the oxygen consumption rate and activity of mitochondrial complexes were impaired in StarD7-KD cells. To confirm these results, we established StarD7-KO HEPA-1 cells by double nicking using CRISPR/Cas9n. As expected, StarD7-KD and - KO cells showed a significant reduction in mitochondrial PC content. The ATP level and growth rate of KO cells were notably lower compared with wild-type cells when cultured in glucose-free galactose-containing medium to force cells to rely on mitochondrial ATP production. In KO cells, the level of the MTCO1 protein, a primary subunit of complex IV, was reduced without a concomitant decrease in its mRNA, but the level was restored when StarD7-I was overexpressed. StarD7-KO cells showed impaired formation of the mitochondrial supercomplexes and exhibited a disorganized cristae structure, with no changes in optic atrophy 1 protein. These findings indicate that StarD7 plays important roles in maintaining the proper composition of mitochondrial phospholipids as well as mitochondrial function and morphogenesis.