Mitochondria-SR Tethering: Its Role in Cardiac Bioenergetics and Ca2+ Dynamics

这一mpi方案的主要主题是线粒体钙摄取起双重“阴阳”作用。 心脏在压力下的作用：它确保在工作压力下满足额外的能量需求， 同时也是氧化应激下细胞内钙超载/毒性的途径。该项目使用了一种新的有条件敲门- 在线粒体主要钙摄取系统的一个重要亚单位EmRE/Smdt1的大鼠模型中，有丝分裂素-Smdt1是线粒体钙摄取系统的重要亚单位。 线粒体钙单转运体通道复合体(MCUC)。激发-生物能量学(EB)耦合是一种信号 一种利用肌浆网(SR)释放的钙离子激活MCUC并产生有丝分裂素的环路。 基质钙离子信号上调三磷酸腺苷的产生。我们的长期目标是将基本的 EB偶联对心脏健康和疾病的作用机制。我们之前的工作表明，MCUC是 被招募到线粒体-SR(Mito-SR)接触的热点，通过一种仍然有效地介导EB偶联 未知的机制。 这项建议旨在解决我们对EB联结的以下认识空白： i)。MCUC在心脏应激耐受、舒张期功能障碍和射血功能不全的心力衰竭中的作用 分数(HFpEF)。Ii)。MCUC募集到热点的分子机制、蛋白质-蛋白质相互作用 Mito-SR联系人。三)。细胞器动力学(接触形成、融合/分裂)是如何与DNA结合在一起的？ 钙离子转运分布动力学？四)。显性负亚单位MCUB在MCUC热点中的作用 形成、控制非活动和可激活的MCUC通道池分布，以达到EB之间的平衡 偶联和钙离子毒性。 中心假说是线粒体Ca~(2+)在控制健康和疾病中的二分法 心肌细胞依赖于EmRE和MCUB在调节细胞功能定位和数量中的关键作用。 传统的MCUC；这种复杂的调节在心脏适应“战斗或逃跑”和氧化应激反应中至关重要。 海绵。为了检验这一假设，我们设定了三个具体目标： 目的1.评估MCUC在交感应激中对EB偶联的调节并确定 如果这一功能的停止可能导致舒张期功能障碍或HFpEF。 目的2.阐明大鼠心肌细胞MCUC热点募集的分子机制。 目的3.研究EMRE、MCU和MCUB在调节MCUC定位中的动态相互作用 在保持EB偶联效率的同时，防止病理性应激下的钙毒性。 拟议研究的完成将为医疗保险的监管机制产生一个新的范式。 心肌能量学中的线粒体钙离子。这一新发现将为一种新的治疗方法提供机制基础 治疗心力衰竭的策略。

This MPI proposal has the overarching theme that mitochondrial Ca2+ uptake plays dual “ying-yang” roles when the heart is under stress: it ensures that extra energy demands are met under workload stress, while it is the route for Ca2+ overload/toxicity under oxidative stress. The project uses a new conditional knock- out rat model for EMRE/Smdt1, an essential subunit of the main mitochondrial Ca2+ uptake system, the mito- chondrial Ca2+ uniporter channel complex (MCUC). The excitation-bioenergetics (EB) coupling is a signaling loop that uses the Ca2+ released by sarcoplasmic reticulum (SR) to activate MCUC and generate mitochon- drial matrix Ca2+ signals to upregulate ATP production. Our long-term goal is to translate the fundamental mechanism of EB coupling to health and disease of the heart. Our previous work demonstrated that MCUC is recruited to hotspots at the mitochondria-SR (Mito-SR) contacts to effectively mediate EB coupling by a yet unknown mechanism. This proposal aims to address the following gaps in our knowledge about EB coupling: i). The role of MCUC in cardiac stress tolerance, diastolic dysfunction and heart failure with preserved ejection fraction (HFpEF). ii). Molecular mechanisms, protein-protein interactions of MCUC recruitment to hotspots at Mito-SR contacts. iii). How are organelle dynamics (contact formation, fusion/fission) integrated with the dy- namics of Ca2+ transport distribution? iv). The role of a dominant negative subunit MCUB in the MCUC hotspot formation, control of the inactive and activatable MCUC channel pool distribution to attain balance between EB coupling and Ca2+ toxicity. The Central Hypothesis is that the dichotomy of mitochondrial Ca2+ in controlling health and disease of cardiomyocytes hinges on the crucial role of EMRE and MCUB in regulating the location and quantity of func- tional MCUC; this elaborate regulation is critical in cardiac adaptation to “fight or flight” and oxidative stress re- sponses. Three specific aims are set up to test this hypothesis: Aim 1. Assess the regulation of EB coupling by MCUC during “fight or flight” sympathetic stress and determine if cessation of this function could lead to diastolic dysfunction or HFpEF. Aim 2. Elucidate the molecular mechanism of the MCUC hotspot recruitment in the rat cardiomyocytes. Aim 3. Study the dynamic interactions between EMRE, MCU and MCUB in regulating the MCUC localization to maintain EB coupling efficiency while preventing Ca2+ toxicity under pathological stresses. Completion of the proposed studies will generate a new paradigm for the regulatory mechanisms of mi- tochondrial Ca2+ in cardiac energetics. The new findings will provide mechanistic basis for a new therapeutic strategy to treat heart failure.