Hou Tingting, Jian Chongshu, Xu Jiejia, Huang August Yue, Xi Jianzhong, Hu Keping, Wei Liping, Cheng Heping, Wang Xianhua
State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China.
Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.
Cell Calcium. 2016 May;59(5):262-70. doi: 10.1016/j.ceca.2016.03.002. Epub 2016 Mar 4.
Mitochondrial flashes (mitoflashes) represent stochastic and discrete mitochondrial events that each comprises a burst of superoxide production accompanied by transient depolarization and matrix alkalinization in a respiratory mitochondrion. While mitochondrial Ca(2+) is shown to be an important regulator of mitoflash activity, little is known about its specific mechanism of action. Here we sought to determine possible molecular players that mediate the Ca(2+) regulation of mitoflashes by screening mitochondrial proteins containing the Ca(2+)-binding motifs. In silico analysis and targeted siRNA screening identified four mitoflash activators (MICU1, EFHD1, SLC25A23, SLC25A25) and one mitoflash inhibitor (LETM1) in terms of their ability to modulate mitoflash response to hyperosmotic stress. In particular, overexpression or down-regulation of EFHD1 enhanced or depressed mitoflash activation, respectively, under various conditions of mitochondrial Ca(2+) elevations. Yet, it did not alter mitochondrial Ca(2+) handling, mitochondrial respiration, or ROS-induced mitoflash production. Further, disruption of the two EF-hand motifs of EFHD1 abolished its potentiating effect on the mitoflash responses. These results indicate that EFHD1 functions as a novel mitochondrial Ca(2+) sensor underlying Ca(2+)-dependent activation of mitoflashes.
线粒体闪烁（mitoflashes）代表随机且离散的线粒体事件，每个事件都包括超氧化物爆发产生，同时伴有呼吸性线粒体的瞬时去极化和基质碱化。虽然线粒体Ca(2+)被证明是线粒体闪烁活动的重要调节因子，但其具体作用机制却知之甚少。在这里，我们试图通过筛选含有Ca(2+)结合基序的线粒体蛋白，来确定介导Ca(2+)对线粒体闪烁调节作用的可能分子参与者。通过计算机分析和靶向siRNA筛选，鉴定出了四种线粒体闪烁激活剂（MICU1、EFHD1、SLC25A23、SLC25A25）和一种线粒体闪烁抑制剂（LETM1），依据它们调节线粒体闪烁对高渗应激反应的能力。特别是，在各种线粒体Ca(2+)升高的条件下，EFHD1的过表达或下调分别增强或抑制了线粒体闪烁激活。然而，它并没有改变线粒体Ca(2+)的处理、线粒体呼吸或ROS诱导的线粒体闪烁产生。此外，EFHD１的两个EF-手基序的破坏消除了其对线粒体闪烁反应的增强作用。这些结果表明，EFHD1作为一种新型的线粒体Ca(2+)传感器，参与Ca(2+)依赖的线粒体闪烁激活。
