Controlling monolysocardiolipin/cytochrome c peroxidase complexes in Barth syndrome

心磷脂（CL）是线粒体的标志性磷脂，是优化线粒体功能和许多细胞过程所必需的。CL的重新合成之后是一个独特的重塑途径，其特征是磷脂酶介导的CL去酰化成单聚心磷脂（mCL）和mCL被他法嗪（Taz）再酰化形成主要不饱和CL的循环。Taz基因突变可导致危及生命的遗传疾病Barth综合征（BTHS），这凸显了CL重塑的重要性。虽然Taz缺乏导致mCL的积累是明确的，但在BTHS中，将有缺陷的CL重塑与病理联系起来的机制尚不清楚。活性氧（ROS）的增加是taz缺陷细胞的一个特征，与BTHS的发病机制有关。然而，在CL重塑的背景下，mCL和CL的氧化物种（mCLox和CLox）的详细氧化还原脂质组学分析尚未进行。我们的初步和已发表的研究表明，CL和mCL与膜间空间血红蛋白细胞色素c （cyt c）形成复合物，将其转化为一种强效过氧化物酶，产生mCLox和CLox。该研究将验证一种创新假设，即异常CL重塑以及mCL/cyt - c复合物的过氧化作用导致BTHS中CL/mCL氧化的恶性代谢循环。我们的方法结合了我们在遗传学，分子生物学和细胞生物学（格林伯格实验室）的专业知识和经验，以及质谱技术，氧化脂质组学和脂质生物化学（卡根实验室）的创新方法。目的1将验证mCL/cyt c过氧化作用因Taz缺乏而加剧的工作假设。目标2将利用固态核磁共振和计算模型来严格表征mCL/cyt c配合物，并确定导致过氧化物酶活性增加的特性。我们希望这些研究能够首次详细描述CL重塑在生成和消除mCLox/CLox中的作用。

Cardiolipin (CL), the signature phospholipid of mitochondria, is required for optimal mitochondrial function and numerous cellular processes. The de novo synthesis of CL is followed by a unique remodeling pathway, which is characterized by cycles of phospholipase-mediated deacylation of CL to monolysocardiolipin (mCL), and reacylation of mCL by tafazzin (Taz) to form predominantly unsaturated CL species. Mutations in Taz cause the life-threatening genetic disorder, Barth syndrome (BTHS), highlighting the significance of CL remodeling. While it is clear that Taz deficiency leads to accumulation of mCL, the mechanism linking defective CL remodeling to the pathology in BTHS is not known. An increase in reactive oxygen species (ROS), a feature of Taz-deficient cells, has been implicated in BTHS pathogenesis. However, detailed redox lipidomic analyses of oxidized species of mCL and CL (mCLox and CLox) in the context of CL remodeling have not been performed. Our preliminary and published studies show that CL and mCL form complexes with the intermembrane space hemoprotein, cytochrome c (cyt c), converting it to a potent peroxidase that generates mCLox and CLox. The proposed study will test the innovative hypothesis whereby aberrant CL remodeling along with peroxidation by mCL/cyt c complexes leads to a vicious metabolic cycle of CL/mCL oxidation in BTHS. Our approach combines our expertise and experience in genetics, molecular biology, and cell biology (Greenberg lab) with innovative approaches in mass spectrometry technologies, oxidative lipidomics, and biochemistry of lipids (Kagan lab). Aim 1 will test the working hypothesis that peroxidation by mCL/cyt c is exacerbated by Taz deficiency. Aim 2 will utilize solid-state NMR and computational modeling to rigorously characterize mCL/cyt c complexes and identify properties resulting in gain of peroxidase activity. We expect these studies to provide the first detailed characterization of the role of CL remodeling in generating and eliminating mCLox/CLox.