REGULATION OF MITOCHONDRIAL ENERGETICS BY INTRACELLULAR IONS

细胞内离子对线粒体能量的调节

• 批准号: 7114057
• 负责人: Brian O'Rourke
• 金额: $ 36.74万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-10 至 2010-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7114057
• 关键词: biochemistry; bioenergetics; biological signal transduction; calcium flux; calcium ion; cardiac myocytes; electrophysiology; extracellular matrix; fluorescence; heart function; intracellular transport; ion transport; laboratory rabbit; mathematical model; mitochondria; myocardial ischemia /hypoxia; myocardium; potassium channel; potassium ion; proteomics; reperfusion; sodium ion

An increase in cardiac work evokes a rapid increase in mitochondrial oxygen consumption and ATP synthesis to meet the energetic demand. The mechanism of this response is thought to involve stimulation of oxidative phosphorylation at multiple sites in the pathway. Two commonly proposed mechanisms include i) enhancement of the rate of mitochondrial electron transport and ATP synthesis by the products of ATP consumption (ADP, Pi), and ii) upstream stimulation of NADH production by Ca2+ at the level of the Krebs cycle. In intact cardiac muscle, ischemia and reperfusion alters both ion homeostasis and mitochondrial function, but the effects on global mitochondrial control have not been investigated. The goal of this project is to characterize the role of intracellular cations in the mechanism of energy supply and demand matching in intact cardiac muscle and isolated cardiomyocytes and to determine how these processes are modified by ischemia and reperfusion. Specifically, we will employ novel fluorescence techniques to examine how the interdependent actions of intracellular Ca2+, Na , and K+ modulate the mitochondrial bioenergetic response to a change in workload in normal and post-ischemic cardiac muscles and cells. The dynamics of Ca2+ transport from the cytoplasmic space to the mitochondrial matrix during cardiac excitation-contraction coupling will be measured, and the coupling of mitochondrial Ca2+ influx to the stimulation of energy metabolism will be determined. We will test the hypothesis that intracellular Na+, which increases dramatically during ischemia, plays a key role in modifying the bioenergetic response to changes in intracellular Ca2+. We will also examine whether mitochondrial Ca2+-activated K+ (mitoKca) channels are activated in response to physiological changes in mitochondrial matrix Ca2+, thus modifying the energetic response. This data will be integrated into a newly developed comprehensive computational model of the cardiac cell as a framework for understanding the effects of altered ion homeostasis and ischemia on the electrophysiology, force production, and Ca2+ handling properties of intact cardiac muscle. The results will be compared with the proteomic and biochemical analyses, and metabolic control experiments to be carried out using the same animal model in the other components of the Program Project. Elucidating the contribution of ion homeostasis to supply and demand matching will permit us to rationally design therapeutic strategies for coping with contractile failure and arrhythmogenesis in the post-ischemic heart.

心脏工作的增加引起了线粒体消耗量的迅速增加和 ATP合成以满足能量需求。人们认为这种反应的机制涉及刺激途径中多个位点的氧化磷酸化。两种通常提出的机制包括i）通过ATP消耗的产物（ADP，PI）和II）在KREBS循环的水平上提高了ATP消耗（ADP，PI）和II）的线粒体电子传输速率和ATP合成的速率。在完整的心肌肌肉中，缺血和再灌注会改变离子稳态和线粒体功能，但尚未研究对全球线粒体控制的影响。该项目的目的是表征细胞内阳离子在完整心肌和孤立的心肌细胞中能量供求机理中的作用，并确定如何通过缺血和再灌注来改变这些过程。具体而言，我们将采用新型的荧光技术来研究细胞内Ca2+，Na和K+的相互依赖作用如何调节线粒体生物能对正常和缺血后心脏肌肉和细胞工作量变化的变化。将测量从细胞质空间到心脏激发反应偶联过程中Ca2+转运到线粒体基质的动力学，并确定线粒体Ca2+涌入与刺激能量代谢代谢的偶联。我们将检验以下假设：缺血期间大幅增加的细胞内Na+在修饰对细胞内Ca2+变化的生物能反应中起着关键作用。我们还将检查线粒体Ca2+激活的K+（Mitokca）通道是否会因线粒体基质Ca2+的生理变化而激活，从而改变了能量反应。这些数据将集成到心脏细胞的新开发的综合计算模型中，以了解改变离子稳态和缺血对电生理学，力产生以及CA2+处理性心脏肌肉的影响的影响。结果将与蛋白质组学和生化分析以及要进行的代谢控制实验进行比较。 在程序项目的其他组件中使用相同的动物模型。阐明离子体内平衡对供求匹配的贡献将使我们能够合理地设计治疗策略，以应对后缺血性心脏中的收缩衰竭和心律失常发生。