Aberrant Cardiolipin Dynamics in Barth Syndrome - Renewal - 1

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。为了检验这一假设，我们将重点关注BS的两个特征，这两个特征都是依赖的 高浓度的膜蛋白。首先，我们将确定BS中能量不足的原因。 我们将确定OXPHOS复合物对飞行肌线粒体中CL重塑的影响， 反之亦然，CL重塑对OXPHOS系统的影响。然后，我们将测试是否干扰CL 重塑或OXPHOS系统对线粒体的单个组分的半衰期有任何影响， 因为我们的初步数据表明CL重塑对于CL稳定性至关重要。二是 将确定BS中精子发生停滞的机制。我们的初步数据表明，CL 重塑对于浓缩线粒体的形成至关重要，浓缩线粒体是一种独特类型的细胞器， 在生殖细胞发育过程中，在高浓度下积累ADP/ATP载体（Ant 4）的特异性同种型 浓度.我们的数据还表明，浓缩的线粒体参与了 顶体我们将确定CL重塑在浓缩线粒体形成中的作用， 建立浓缩的线粒体支持顶体生物发生的机制。我们 应用依赖于尖端技术，如稳定同位素的脂质体通量分析，冷冻， 电子显微镜断层扫描和同量异位素标记的定量蛋白质组学。拟定研究 意义重大，因为它将确定CL重塑的机制和功能，这是一个广泛保守的 反应的不确定意义，因为它将建立BS的病理机制。

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 focus on two features of BS, which are both dependent on the high concentration of membrane proteins. First, we will identify the cause of energy deficiency in BS. We will determine the effect of the complexes of OXPHOS on CL remodeling in flight muscle mitochondria and vice versa, the effect of CL remodeling on the OXPHOS system. We will then test whether disturbing either CL remodeling or the OXPHOS system has any effect on the half-life of individual components of mitochondrial membranes because our preliminary data suggest that CL remodeling is essential for CL stability. Second, we will determine the mechanism of the arrest of spermatogenesis in BS. Our preliminary data suggest that CL remodeling is essential for the formation of condensed mitochondria, a unique type of organelle that emerges during germ cell development and that accumulates a specific isoform of the ADP/ATP carrier (Ant4) at high concentration. Our data also suggest that condensed mitochondria are involved in the biogenesis of acrosomes. We will identify the role of CL remodeling in the formation of condensed mitochondria and then establish the mechanism by which condensed mitochondria support the biogenesis of acrosomes. Our application relies on cutting-edge techniques, such as lipidome-wide flux analysis with stable isotopes, cryo- electron microscopic tomography, and quantitative proteomics with isobaric labeling. 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.