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

项目总结 由线粒体氧化磷酸化成分突变引起的疾病可能是 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5000人中有1人。虽然几乎任何器官都可能受到影响，但心脏 经常参与，因为心脏功能对能量的需求如此之高。这些线粒体 心肌病的预后尤其严峻，死亡率几乎增加了三倍。 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的过程中， 钙信号可能在病理过程中起中心作用。钙离子流入线粒体可以 有效地刺激ATP的合成，但过高的水平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，促进了ATP的合成。不过，经过长时间的进入， 线粒体钙水平过高，引发线粒体衰竭，加重心脏疾病 功能障碍。这项研究的基本原理是确定这样的监管是否存在于井中- 特征性的线粒体心肌病动物模型，其特征是A基因缺失 线粒体转录因子(Tfam)在心肌细胞中的选择性表达。第一个目标是确定 在初步研究中发现的线粒体钙水平增加是否真的是代偿性的。为 这个目标是，我们将创造出线粒体心肌病的动物，这些动物的线粒体可以是 不能吸收钙，或抵抗过高的钙水平。第二个目标是确定 导致线粒体钙内流增强的分子机制，并确定这种 增强可以在人类诱导的多能干细胞来源的心肌细胞中复制。在……里面 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，克服了钙转运研究中存在的技术挑战。如果 如果成功，我们的研究将为这些毁灭性疾病的潜在治疗定义一个重要的新目标 精神错乱。

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.