Molecular modulation of the mitochondrial Na+/Ca2+ exchanger as a novel therapeutic target for heart failure.

项目摘要/摘要 心力衰竭(HF)是美国人残疾和死亡的主要原因，目前影响着600万人 仅在美国，人们每年的经济负担就高达300亿美元。钙的流动(钙离子) 线粒体的进出是调节细胞能量代谢和细胞死亡的关键机制。 由于在衰竭的心脏中，能量和心肌细胞的存活都受到了影响，线粒体发生了变化 Ca~(2+)(mCa~(2+))的处理被认为是HF的一个促成因素。然而，具体的变化是 在心力衰竭的发生发展过程中发生的钙离子交换及其调节机制 这些影响仍然没有得到明确的界定。因此，在开发HF疗法之前，一个必要的步骤 旨在调节mCa~(2+)交换的是准确确定mCa~(2+)在整个过程中是如何处理变化的 失败过程，并了解慢性改变的mCa~(2+)交换对 衰竭的心脏的功能。最近的研究表明，线粒体钠钙交换器(NCLX)， 在人类心力衰竭中转录上调。NCLX的结构和功能 也通过包括磷酸化和选择性剪接在内的机制来控制，以及初步数据 提示心肌细胞在生理或病理过程中通过这些过程调节NCLX 压力。初步研究结果还表明，转基因NCLX过表达可增强心肌细胞的线粒体钙离子水平 挤压足以保护小鼠模型的收缩功能和减轻病理重塑 非缺血性心衰。基于这些数据，我们假设心肌细胞增加净NCLX活性是因为 调节心衰细胞内钙离子平衡的适应性机制。在这里，我们将追求特定的目标，利用基因 心脏NCLX功能净增加或减少的小鼠模型研究NCLX改变的贡献 NCLX在慢性心力衰竭发生发展中的作用及疗效评价 对这种疾病的调制。我们还将结合强大的蛋白质组和分子方法与直接 NCLX功能的体外评估以确定控制NCLX活性的内源性机制 在内心深处。该项目将首次对NCLX活动的改变如何保护或 当承受持续的病理性应激时，使心脏容易衰竭，并将产生基本的 可用于治疗控制NCLX活性的知识。这些发现将具有广泛的意义 翻译相关性不仅与心脏病有关，而且与其他以线粒体钙离子变化为特征的疾病也相关 动态平衡，如阿尔茨海默病和神经退行性变。详细的培训计划，概述了 应向申请人提供的指导以及天普提供的资源和技术支持 大学的转化医学中心已经建立起来，以确保成功完成 建议的工作，并培养申请者的科学成熟为独立的学术研究人员。

PROJECT SUMMARY/ABSTRACT Heart failure (HF) is a leading cause of disability and death among Americans that currently affects 6 million people at an economic burden of ~$30 billion per year in the United States alone. The flow of calcium (Ca2+) into and out of the mitochondria is a key mechanism regulating cellular energy metabolism and cell death. Since both energetics and cardiomyocyte survival are compromised in the failing heart, altered mitochondrial Ca2+ (mCa2+) handling has been proposed as a contributing factor in HF. However, the specific changes that occur in mCa2+ exchange during the development and progression of HF, and the mechanisms that mediate these effects, remain poorly defined. Therefore, a necessary step before the development of HF therapies aimed at modulating mCa2+ exchange is to determine exactly how mCa2+ handling changes throughout the failure process and to understand the specific consequences of chronically-altered mCa2+ exchange on the function of the failing heart. Recent studies reveal that the mitochondrial sodium-calcium exchanger (NCLX), which mediates extrusion of mCa2+, is transcriptionally upregulated in human HF. NCLX structure and function are also controlled via mechanisms including phosphorylation and alternative splicing, and preliminary data indicate that cardiomyocytes regulate NCLX through these processes during physiological or pathological stress. Initial findings also suggest that transgenic overexpression of NCLX to enhance cardiomyocyte mCa2+ extrusion is sufficient to protect contractile function and attenuate pathological remodeling in mouse models of non-ischemic HF. Based on these data, we hypothesize that cardiomyocytes increase net NCLX activity as an adaptive mechanism to control mCa2+ homeostasis in HF. Here we will pursue Specific Aims employing genetic mouse models with net gain or reduction of cardiac NCLX function to examine the contribution of altered NCLX activity to the development and progression of chronic HF and assess the therapeutic potential of NCLX modulation for this disease. We will also combine robust proteomic and molecular approaches with direct in vitro assessments of NCLX function to determine the endogenous mechanisms that control NCLX activity within the heart. This project will be the first to causatively examine how alterations in NCLX activity protect or predispose the heart to failure when subjected to sustained pathological stress, and will generate fundamental knowledge that can be exploited for therapeutic control of NCLX activity. These findings will have broad translational relevance not only for cardiac disease, but also for other conditions characterized by altered mCa2+ homeostasis such as Alzheimer’s disease and neurodegeneration. A detailed training plan outlining the mentorship to be provided to the Applicant and the resources and technical support available at Temple University’s Center for Translational Medicine has been developed to ensure successful completion of the proposed work and foster the Applicant’s scientific maturation into an independent academic investigator.