Substrate-dependent and cyclophilin D-independent regulation of mitochondrial flashes in skeletal and cardiac muscle.
Substrate-dependent and cyclophilin D-independent regulation of mitochondrial flashes in skeletal and cardiac muscle.
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DOI：
10.1016/j.abb.2019.03.003
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发表时间：
2019-04
影响因子：
3.9
通讯作者：
L. Wei-LaPierre;Alina Ainbinder;Kevin M. Tylock;R. Dirksen
中科院分区：
文献类型：
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作者：
L. Wei-LaPierre;Alina Ainbinder;Kevin M. Tylock;R. Dirksen
线粒体闪光（mitoflash）是线粒体靶向cpYFP （mt-cpYFP）检测到的线粒体基质中的随机事件。mitoflash是活性氧（ROS）产生的量子爆发，伴随着适度的基质碱化和线粒体膜电位的去极化。有丝分裂是存在于多种细胞类型中的基本事件。迄今为止，有丝分裂产生和终止的确切机制仍然难以捉摸。线粒体膜通透性过渡孔（mPTP）在线粒体闪变过程中的瞬时开放被提出来解释线粒体膜电位去极化。在这里，我们开始比较亲环蛋白D （CypD）缺乏和线粒体底物对骨骼肌和心肌中线粒体闪速活性的组织特异性影响。与之前的报道相反，我们发现CypD敲除不会改变急性分离心肌细胞、骨骼肌纤维或骨骼肌和心脏分离线粒体的丝裂闪频率或其他丝裂闪特性。然而，在骨骼肌纤维中，CypD缺乏导致活性依赖性线粒体Ca2+摄取和活性依赖性线粒体闪光活性的平行增加。电刺激后线粒体Ca2+摄取和mitoflash活性的增加被线粒体Ca2+摄取的抑制所消除。我们还发现，在完整的骨骼肌纤维和心肌细胞之间，线粒体闪光的频率和幅度有很大差异，但在分离的线粒体中没有这种差异。我们认为，这种差异可能部分是由于完整骨骼肌纤维（主要是糖酵解）和心肌细胞（主要是氧化）中底物可用性的差异。总的来说，我们发现CypD在骨骼肌和心肌的基础条件下对丝裂闪的生物发生没有显著贡献，但在肌肉活动期间确实调节丝裂闪事件。此外，线粒体底物可用性强烈调节线粒体闪变频率的组织依赖性差异。
Mitochondrial flashes (mitoflashes) are stochastic events in the mitochondrial matrix detected by mitochondrial-targeted cpYFP (mt-cpYFP). Mitoflashes are quantal bursts of reactive oxygen species (ROS) production accompanied by modest matrix alkalinization and depolarization of the mitochondrial membrane potential. Mitoflashes are fundamental events present in a wide range of cell types. To date, the precise mechanisms for mitoflash generation and termination remain elusive. Transient opening of the mitochondrial membrane permeability transition pore (mPTP) during a mitoflash is proposed to account for the mitochondrial membrane potential depolarization. Here, we set out to compare the tissue-specific effects of cyclophilin D (CypD)-deficiency and mitochondrial substrates on mitoflash activity in skeletal and cardiac muscle. In contrast to previous reports, we found that CypD knockout did not alter the mitoflash frequency or other mitoflash properties in acutely isolated cardiac myocytes, skeletal muscle fibers, or isolated mitochondria from skeletal muscle and the heart. However, in skeletal muscle fibers, CypD deficiency resulted in a parallel increase in both activity-dependent mitochondrial Ca2+uptake and activity-dependent mitoflash activity. Increases in both mitochondrial Ca2+uptake and mitoflash activity following electrical stimulation were abolished by inhibition of mitochondrial Ca2+uptake. We also found that mitoflash frequency and amplitude differ greatly between intact skeletal muscle fibers and cardiac myocytes, but that this difference is absent in isolated mitochondria. We propose that this difference may be due, in part, to differences in substrate availability in intact skeletal muscle fibers (primarily glycolytic) and cardiac myocytes (largely oxidative). Overall, we find that CypD does not contribute significantly in mitoflash biogenesis under basal conditions in skeletal and cardiac muscle, but does regulate mitoflash events during muscle activity. In addition, tissue-dependent differences in mitoflash frequency are strongly regulated by mitochondrial substrate availability.