Molecular examination of mitochondrial calcium control

摘要 心脏中钙离子的升高可以作为线粒体能量输出增加的信号，通过 直接增加电子传输链和相关脱氢酶的活性。然而，在 同时，心肌梗死后急性发生的钙离子持续升高可导致 线粒体通透性转换孔开放引起的心肌细胞坏死和凋亡性死亡 (PTP)。线粒体钙单转运体(MCU)复合体通过内膜将钙离子输入到 线粒体基质，在急性缺血损伤期间，它可以影响能量产生和PTP开放。 因此，MCU复合体和许多最近被描述的构成它的基因可能是新的 旨在减少心肌细胞死亡或改变心脏代谢的药物设计的治疗目标 性能。构成MCU的基因在过去4年里才被发现；因此 关于线粒体钙调节与心脏遗传相关的研究领域仍处于初级阶段 活体生理学和病理生理学。在这里，我们建议使用缺少许多关键分子的小鼠 线粒体Ca~(2+)处理的调节因子对生理和病理的解码和区分 基线和疾病时的钙信号。我们的首要目标是研究线粒体钙离子是如何内流的 外流调节心脏的生命、死亡和新陈代谢。然而，在我们的领域中，没有一个心脏实验室 描述线粒体钙离子处理的复杂生物物理学以及在 同时利用必要的小鼠遗传学和细胞生物学来真正实现这一目标 项目。因此，我们实施了无缝协作的双PI方案，这将是50%的努力 在Molkentin和Bers实验室之间，结合了最好的小鼠分子遗传学和心脏 生理学通过对线粒体和细胞内钙离子成像和PTP活性的创新评估， 分别进行了分析。我们的目标将是：1)表征新发现的MCU复杂基因的功能 以及线粒体钙离子调控心脏的其他新基因，2)评估MCU基因的功能 在潜在的心脏生理、代谢和缺血损伤后，以及3)评估PTP动力学和 PTP在调节线粒体钙离子和细胞死亡中的生理和病理生理状态。这个 2个私人投资机构在与多个共享出版物和联合赠款合作方面有着良好的记录。因此， 它们代表了两种完全不同的实验室技能的理想融合，这两种技能是真正理解 线粒体钙调节及其对心脏生理学和疾病反应性的影响。

Abstract Ca2+ elevations in the heart can serve as a signal for augmented energy output from the mitochondria by directly increasing the activity of the electron transport chain and associated dehydrogenases. However, at the same time sustained elevations in Ca2+ that occurs acutely after myocardial infarction injury can cause cardiomyocyte necrotic and apoptotic death through opening of the mitochondrial permeability transition pore (PTP). The mitochondrial Ca2+ uniporter (MCU) complex imports Ca2+ across the inner membrane into the mitochondrial matrix where it can affect both energy production and PTP opening during acute ischemic injury. Hence the MCU complex and many of the more recently described genes that constitute it could be novel therapeutic targets for drug design with the goal of reducing cardiomyocyte death or altering cardiac metabolic performance. The genes that comprise the MCU were only recently identified in the past 4 years; hence the field is still in its infancy with respect to genetically correlating mitochondrial Ca2+ regulation with cardiac physiology and pathophysiology in vivo. Here we propose to use mice lacking many of these key molecular regulators of mitochondrial Ca2+ handling to decode and differentiate between physiological and pathological Ca2+ signals at baseline and with disease. Our overarching goal is to examine how mitochondrial Ca2+ influx and efflux regulates cardiac life, death and metabolism. However, no single cardiac laboratory in our field has the underlying expertise to both characterize the complex biophysics of mitochondrial Ca2+ handling and at the same time employ the necessary mouse genetics and cell biology to truly achieve the stated goals of this project. Hence, we have implemented a seamless collaborative dual-PI proposal that will be 50/50 effort between the Molkentin and Bers laboratory, to wed the very best in mouse molecular genetics and cardiac physiology with innovative assessment of mitochondrial and intracellular Ca2+ imagining and PTP activity, respectively. Our Aims will be: 1) to characterize the function of the newly identified MCU complex genes as well as other new genes underlying mitochondrial Ca2+ regulation the heart, 2) To assess MCU gene function in underlying cardiac physiology, metabolism and after ischemic injury, and 3) To assess PTP dynamics and the physiologic versus pathophysiologic states of the PTP in regulating mitochondrial Ca2+ and cell death. The 2 PIs have a strong track record of working together with multiple shared publications and joint grants. Hence, they represent an ideal melding of 2 rather divergent laboratory skill sets that are needed to truly understand mitochondrial Ca2+ regulation and its effect on cardiac physiology and disease responsiveness.