Metabolic Impact and Mechanism of Enhanced Mitochondrial Calcium Uptake in Mitochondrial Cardiomyopathies

项目摘要 由线粒体氧化磷酸化组分突变引起的疾病可以是 这是毁灭性的，因为线粒体对能量合成至关重要。这些疾病主要发生在 婴儿和儿童，患病率为1/5000。虽然几乎任何器官都可能受到影响，但心脏 因为心脏功能需要很高的能量。这些线粒体 心肌病的预后特别糟糕，死亡率增加了近三倍， 与没有心脏受累的儿童相比。在将心脏功能与线粒体代谢联系起来时， 钙信号传导可能是病理过程的中心。钙离子流入线粒体， 有效刺激ATP合成，但过量会引发线粒体衰竭和细胞死亡。我们 假设当氧化磷酸化受损时，反馈调节导致 钙内流的代偿性增加，促进ATP合成。然而，经过长时间的进入， 线粒体钙水平变得过高并触发线粒体衰竭，加重心脏病。 功能障碍这项研究的基本原理是确定这种调节是否存在于井中- 线粒体心肌病的特征性动物模型，其特征是一个基因缺失， 线粒体转录因子（Tfam）。第一个目标是确定 初步研究中发现的线粒体钙水平升高是否真的是代偿性的。为 为了这个目标，我们将创造出患有线粒体心肌病的动物，这些动物的线粒体要么 不能吸收钙，或对过量的钙有抵抗力。第二个目标是确定 引起线粒体钙离子内流增强的分子机制，并确定是否 增强可以在来源于人诱导多能干细胞的心肌细胞中复制。在 在这些分析中，我们使用了一套创新的技术，包括直接电测量， 线粒体钙电流，克服了研究钙转运的技术挑战。如果 如果成功，我们的研究将为这些破坏性的潜在治疗确定一个重要的新靶点。 紊乱

PROJECT SUMMARY Diseases that arise from mutations in components of mitochondrial oxidative phosphorylation can be devastating, as mitochondria are crucial for energy synthesis. These diseases occur predominantly in infants and children, with a prevalence of 1 in 5000. Though virtually any organ can be affected, the heart is frequently involved, because cardiac function has such high energy requirements. These mitochondrial cardiomyopathies have a particularly grim prognosis, with mortality rates increased nearly three-fold compared to children without cardiac involvement. In linking cardiac function to mitochondrial metabolism, calcium signaling may be central to the pathological process. Calcium influx into the mitochondria can potently stimulate ATP synthesis, but excessive levels trigger mitochondrial failure and cell death. We hypothesize that, when oxidative phosphorylation becomes impaired, feedback regulation causes a compensatory increase in calcium influx, boosting ATP synthesis. However, after prolonged entry, mitochondrial calcium levels become excessive and trigger mitochondrial failure, exacerbating cardiac dysfunction. The rationale for this study is to determine whether such regulation exists in a well- characterized animal model of mitochondrial cardiomyopathies, which features genetic deletion of a mitochondrial transcription factor (Tfam) selectively in cardiomyocytes. The first aim is to determine whether the increased mitochondrial calcium levels found in preliminary studies are truly compensatory. For this aim, we will create animals with mitochondrial cardiomyopathies that have mitochondria that either cannot take up calcium, or are resistant to excessive calcium levels. The second objective is to determine the molecular mechanism causing enhanced mitochondrial calcium influx, and determine whether such enhancement can be replicated in cardiomyocytes derived from human induced pluripotent stem cells. In these analyses, we use an innovative set of techniques, including direct electrical measurement of mitochondrial calcium currents, that overcome technical challenges present in studying calcium transport. If successful, our research will define a significant new target for potential therapy in these devastating disorders.