Aberrant Cardiolipin Dynamics in Barth Syndrome

项目总结/摘要 线粒体是真核生物所必需的富含膜的细胞器。详细的见解已经出现 线粒体膜蛋白的组装和动力学，但一个根本的差距仍然存在 对线粒体脂质的理解。Barth综合征（BS）是一种线粒体脂质代谢紊乱， 特别是抑制心磷脂（CL）的代谢，并因此提供了一种 这是在与人类健康有关的背景下解决这一差距的独特机会。BS是由突变引起的， tafazzin，一种催化CL重塑的酶，即脂肪酸交换反应， 产生CL的特征分子组成。本申请的目的是确定 CL重塑的机制和功能。这一目标符合我们的广泛目标，即了解 CL在线粒体和解开BS的分子病理生理。我们发现全球 氧化磷酸化系统（OXPHOS）的组装驱动CL重塑。我们假设 CL重塑减少了由极高的蛋白质对线粒体脂质施加的包装应力， 浓度，这是由于OXPHOS系统和其他蛋白质在线粒体膜中产生的。因此，在本发明中， CL重塑的功能是稳定脂质-蛋白质相互作用，以允许蛋白质- 拥挤的膜。为了验证这一假设，我们将（i）确定OXPHOS表达的机制， 控制CL重塑和（ii）建立CL重塑在膜组装中的功能。一是为了 为了确定OXPHOS表达控制CL重塑的机制，我们将确定OXPHOS表达对CL重塑的影响。 OXPHOS组装对CL重塑反应的影响，然后确定关键的OXPHOS组装步骤 CL重塑，并最终确定蛋白质拥挤是否影响CL重塑。二是为 建立CL重塑的函数，我们将确定CL重塑对密度的影响， OXPHOS复合物对嵴膜稳定性和生殖细胞发育的影响 线粒体生殖细胞线粒体将被研究，因为我们的初步数据表明， 精子发生中CL重塑和OXPHOS组装。实验将在遗传学上进行 改良酵母、果蝇和小鼠。我们的应用依赖于尖端技术，如脂质体- 稳定同位素宽通量分析、冷冻电子显微镜断层扫描和定量蛋白质组学。 这项研究具有重要意义，因为它将确定CL重塑的机制和功能， 广泛保守的反应，意义不确定，而且因为它将建立 BS.

Project Summary/Abstract Mitochondria are membrane-rich organelles that are essential to eukaryotic life. Detailed insight has emerged into the assembly and the dynamics of mitochondrial membrane proteins, but a fundamental gap has remained in understanding mitochondrial lipids. Barth syndrome (BS) is a disorder of the mitochondrial lipid metabolism, in particular the metabolism of the mitochondria-specific phospholipid cardiolipin (CL), and thus provides a unique opportunity to address this gap in a context relevant to human health. BS is caused by mutations in tafazzin, an enzyme that catalyzes CL remodeling, i.e. the fatty acid exchange reaction by which the characteristic molecular composition of CL is created. The objective of this application is to identify mechanism and function of CL remodeling. This objective fits into our broad goals to understand the function of CL in mitochondria and to unravel the molecular pathophysiology of BS. We discovered that the global assembly of the system of oxidative phosphorylation (OXPHOS) is driving CL remodeling. We hypothesize that CL remodeling reduces the packing stress imposed on mitochondrial lipids by the extremely high protein concentration, which arises in mitochondrial membranes due to the OXPHOS system and other proteins. Thus, the function of CL remodeling is to stabilize lipid-protein interactions in order to allow the assembly of protein- crowded membranes. To test this hypothesis, we will (i) identify the mechanism by which OXPHOS expression controls CL remodeling and (ii) establish the function of CL remodeling in membrane assembly. First, in order to identify the mechanism by which OXPHOS expression controls CL remodeling, we will determine the effect of OXPHOS assembly on the CL remodeling reaction, then identify the OXPHOS assembly step that is critical for CL remodeling, and finally determine whether protein crowding affects CL remodeling. Second, in order to establish the function of CL remodeling, we will determine the effect of CL remodeling on the density of OXPHOS complexes, on the stability of cristae membranes, and on the development of germ cell mitochondria. Germ cell mitochondria will be studied because our preliminary data suggest a specific role of CL remodeling and OXPHOS assembly in spermatogenesis. Experiments will be carried out in genetically modified yeast, Drosophila, and mice. Our application relies on cutting-edge techniques, such as lipidome- wide flux analysis with stable isotopes, cryo-electron microscopic tomography, and quantitative proteomics. The proposed study is significant because it will identify the mechanism and the function of CL remodeling, a widely conserved reaction of uncertain significance, and because it will establish the pathologic mechanism of BS.