Molecular Biophysics of Mitochondrial Membranes

项目摘要 该项目的重点是了解控制能量转换的分子机制， 电池发电厂，即太阳能电池。离子和代谢物通过线粒体内部的转运 膜是线粒体生理学的基础。在这里，我们研究的分子机制， 线粒体被动摄取H+（“线粒体H+泄漏”）和Ca 2+（“线粒体Ca 2+摄取”）降低 线粒体内膜上的负电压。线粒体H+泄漏是 用于将线粒体底物的化学能转化为热量。线粒体Ca 2+摄取 在胞质Ca 2+瞬变期间Ca 2+进入线粒体以刺激三羧酸钙依赖性酶 循环和线粒体能量转换。线粒体H+泄漏和Ca 2+吸收由 称为解偶联蛋白（UCPs）的线粒体内膜的专门整合蛋白， 线粒体Ca ~（2+）单向转运体（MCU）。UCPs的分子和功能表征 MCU由于无法测量穿过内部线粒体的H+和Ca 2+电流而变得困难 膜直接。我们已经解决了这一重大技术障碍，并开发了一种直接修补的方法- 钳位记录跨整个线粒体内膜的UCP和MCU电流。使用此 方法，我们建议解决UCP和MCU内的结构-功能关系，以了解 通过这些膜转运蛋白控制H+和Ca 2+转运的分子机制。为 UCPs，我们计划确定游离脂肪酸，内源性UCPs激活剂， H+通过UCPs转运。我们还建议开发新一代能够激活H+泄漏的药物 通过UCP，用于治疗II型糖尿病、肥胖症和脂肪肝。在MCU方面，我们建议 揭示了负责MCU的异常高的Ca 2+选择性的分子机制，MCU 内向整流（Ca 2+单向渗透到线粒体），以及细胞溶质的MCU增强 Ca2+。这项研究将解决生物能量学领域的几个长期存在的问题，并最终 能够在治疗和研究目的中对关键线粒体功能进行药理学控制。

Project Summary This project is focused on understanding of the molecular mechanisms that control energy conversion within the cell power plant, the mitochondrion. Transport of ion and metabolites across the inner mitochondrial membrane is the foundation of mitochondrial physiology. Here we study the molecular mechanisms involved in passive uptake of H+ (“mitochondrial H+ leak”) and Ca2+ (“mitochondrial Ca2+ uptake”) into mitochondria down the negative voltage () across the inner mitochondrial membrane. The mitochondrial H+ leak is responsible for the conversion of chemical energy of mitochondrial substrates into heat. The mitochondrial Ca2+ uptake lets Ca2+ enter mitochondria during cytosolic Ca2+ transients to stimulate Ca2+-dependent enzymes of the Krebs cycle and mitochondrial energy conversion. The mitochondrial H+ leak and Ca2+ uptake are mediated by specialized integral proteins of the inner mitochondrial membrane called uncoupling proteins (UCPs) and mitochondrial Ca2+ uniporter (MCU) correspondingly. The molecular and functional characterization of UCPs and MCU has been difficult due to the inability to measure H+ and Ca2+ currents across the inner mitochondrial membrane directly. We have resolved this major technical barrier and developed a method for direct patch- clamp recording of UCP and MCU currents across the whole inner mitochondrial membrane. Using this method, we propose to address the structure-function relations within UCPs and MCU to understand the molecular mechanisms that govern H+ and Ca2+ translocation via these membrane transport proteins. For UCPs, we plan to identify the mechanisms by which free fatty acids, the endogenous UCPs activators, cause H+ translocation via UCPs. We also propose to develop a new generation of drugs that can activate H+ leak via UCP and be used for the treatment of type II diabetes, obesity, and fatty liver. For MCU, we propose to reveal the molecular mechanisms responsible for the exceptionally high Ca2+ selectivity of MCU, the MCU inward rectification (one-way permeation of Ca2+ into mitochondria), and the MCU potentiation by cytosolic Ca2+. This research will resolve several long-standing problems in the field of bioenergetics and will eventually enable pharmacological control of key mitochondrial functions in therapeutic and research purposes.