Optometabolic and molecular analysis of functional links between mitochondrial CA2+signaling, gene regulation and metabolism in the brain

线粒体是唯一的细胞器，结合能量控制和维持Ca2+稳态的关键作用。在驱动ATP合成的同样陡峭的膜电位的驱动下，Ca2+离子被Ca2+单转运体（MCU）带入线粒体，并主要由Na+/Ca2+反转运体（NCLX）挤压回细胞质。适当的线粒体代谢和Ca2+穿梭对于维持一系列神经元活动至关重要。在病理条件下，线粒体功能障碍引起一系列恶性循环，导致不可逆的神经元损伤。然而，线粒体在神经元中的作用的研究受到可用药理学试剂精确度和可逆性不足的阻碍。在这里，我们提出(1)利用我们团队最近发现的MCU和NCLX的分子特性来设计特定的分子工具来控制线粒体功能；(2)建立一种新的光遗传（光代谢）策略，基于靶向光激活离子通道到线粒体基质，通过光线粒体膜电位来控制ATP合成和Ca2+穿梭。利用光代谢-分子结合的方法，我们将确定(1)线粒体如何形成树突核ca2 +信号和神经元基因表达；(2)MCU/NCLX降解或失调是否影响缺血期间神经元的功能特性和命运；(3)线粒体膜电位的快速和短暂变化如何控制单个神经元之间的神经传递；(4)脑区域内和脑区域之间的通信。光代谢和分子技术的实施将能够控制线粒体膜电位，从而以一种暂时可控的、可逆的和细胞特异性的方式控制Ca2+信号和代谢率，无论是在体外还是在体内，因此对于研究从脑或心脏缺血到糖尿病的代谢和缺血性疾病也具有普遍的重要性。

Mitochondria are the only organelles that combine energy control with the critical role in the maintenance of Ca2+ homeostasis. Powered by the same steep membrane potential that drives ATP synthesis, Ca2+ ions are taken into mitochondria by Ca2+ uniporter, MCU, and extruded back to the cytosol primarily by the Na+/Ca2+ antiporter, NCLX. Proper mitochondrial metabolism and Ca2+ shuttling are essential for maintenance of a range of neuronal activities. Under pathologic conditions, mitochondrial dysfunction causes a series of vicious cycles that lead to irreversible neuronal damage. Studies of the role of mitochondria in neurons, however, are impeded by the insufficient precision and reversibility of available pharmacological agents. Here, we propose (1) to take advantage of our team’s recent discovery of the molecular identity of MCU and NCLX to devise specific molecular tools to control the mitochondrial function and (2) to establish a novel optogenetic (optometabolic) strategy based on targeting light-activated ion channels to the mitochondrial matrix, to control by light mitochondrial membrane potential and thereby ATP synthesis and Ca2+ shuttling. Using the combined optometabolic-molecular approach, we will determine (1) how mitochondria shape dendritic-nuclearCa2+ signaling and neuronal gene expression, (2) if MCU/NCLX degradation or dysregulation affects neuronal functional properties and fate during ischemia, (3) how fast and transient changes in mitochondrial membrane potential control neurotransmission between individual neurons and (4) communications within and between brain areas. Implementation of the optometabolic and molecular technologies will enable control of the mitochondrial membrane potential and thereby of the Ca2+ signaling and metabolic rate in a temporallycontrolled, reversible and cell-specific way, both in vitro and in vivo, and therefore will be also of general importance for investigating metabolic and ischemic disorders ranging from brain or cardiac ischemia to Diabetes.