Zhdanov Alexander V, Andreev Dmitry E, Baranov Pavel V, Papkovsky Dmitri B
School of Biochemistry & Cell Biology, University College Cork, Cork, Ireland.
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.
Free Radic Biol Med. 2017 May;106:184-195. doi: 10.1016/j.freeradbiomed.2017.02.025. Epub 2017 Feb 9.
Mitochondrial polarisation is paramount for a variety of cellular functions. Under ischemia, mitochondrial membrane potential (ΔΨm) and proton gradient (ΔpH) are maintained via a reversal of mitochondrial F1Fo ATP synthase (mATPase), which can rapidly deplete ATP and drive cells into energy crisis. We found that under normal conditions in cells with disassembled cytochrome c oxidase complex (COX-deficient HCT116), mATPase maintains ΔΨm at levels only 15-20% lower than in WT cells, and for this utilises relatively little ATP. For a small energy expenditure, mATPase enables mitochondrial ΔpH, protein import, Ca turnover, and supports free radical detoxication machinery enlarged to protect the cells from oxidative damage. Whereas in COX-deficient cells the main source of ATP is glycolysis, the ΔΨm is still maintained upon inhibition of the adenine nucleotide translocators with bongkrekic acid and carboxyatractyloside, indicating that the role of ANTs is redundant, and matrix substrate level phosphorylation alone or in cooperation with ATP-Mg/P carriers can continuously support the mATPase activity. Intriguingly, we found that mitochondrial complex III is active, and it contributes not only to free radical production, but also to ΔΨm maintenance and energy budget of COX-deficient cells. Overall, this study demonstrates that F1Fo ATP synthase can support general mitochondrial and cellular functions, working in extremely efficient 'energy saving' reverse mode and flexibly recruiting free radical detoxication and ATP producing / transporting pathways.
线粒体极化对于多种细胞功能至关重要。在缺血状态下，线粒体膜电位（ΔΨm）和质子梯度（ΔpH）通过线粒体F1Fo ATP合酶（mATPase）的逆转得以维持，这会迅速消耗ATP并使细胞陷入能量危机。我们发现，在细胞色素c氧化酶复合体解体的细胞（COX缺陷型HCT116）的正常条件下，mATPase维持的ΔΨm水平仅比野生型细胞低15 - 20%，并且为此消耗的ATP相对较少。通过少量的能量消耗，mATPase实现线粒体ΔpH、蛋白质导入、钙周转，并支持扩大的自由基解毒机制以保护细胞免受氧化损伤。而在COX缺陷型细胞中，ATP的主要来源是糖酵解，在用硼酸和羧基苍术苷抑制腺嘌呤核苷酸转运体后，ΔΨm仍能维持，这表明腺嘌呤核苷酸转运体的作用是多余的，仅基质水平磷酸化或与ATP - Mg/P载体协同作用就能持续支持mATPase活性。有趣的是，我们发现线粒体复合体III是活跃的，它不仅有助于自由基的产生，还对COX缺陷型细胞的ΔΨm维持和能量收支有贡献。总体而言，这项研究表明F1Fo ATP合酶可以支持一般的线粒体和细胞功能，以极其高效的“节能”逆向模式工作，并灵活地招募自由基解毒以及ATP产生/运输途径。
