Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Leninskiye Gory 1-73, Moscow, 119991, Russia; Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskiye Gory 1-40, Moscow, 119991, Russia.
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskiye Gory 1-40, Moscow, 119991, Russia.
Eur J Cell Biol. 2020 Apr;99(2-3):151071. doi: 10.1016/j.ejcb.2020.151071. Epub 2020 Feb 4.
The mitochondrial network structure dynamically adapts to cellular metabolic challenges. Mitochondrial depolarisation, particularly, induces fragmentation of the network. This fragmentation may be a result of either a direct regulation of the mitochondrial fusion machinery by transmembrane potential or an indirect effect of metabolic remodelling. Activities of ATP synthase and adenine nucleotide translocator (ANT) link the mitochondrial transmembrane potential with the cytosolic NTP/NDP ratio. Given that mitochondrial fusion requires cytosolic GTP, a decrease in the NTP/NDP ratio might also account for protonophore-induced mitochondrial fragmentation. For evaluating the contributions of direct and indirect mechanisms to mitochondrial remodelling, we assessed the morphology of the mitochondrial network in yeast cells with inhibited ANT. We showed that the repression of AAC2 (PET9), a major ANT gene in yeast, increases mitochondrial transmembrane potential. However, the mitochondrial network in this strain was fragmented. Meanwhile, AAC2 repression did not prevent mitochondrial fusion in zygotes; nor did it inhibit mitochondrial hyperfusion induced by Dnm1p inhibitor mdivi-1. These results suggest that the inhibition of ANT, rather than preventing mitochondrial fusion, facilitates mitochondrial fission. The protonophores were not able to induce additional mitochondrial fragmentation in an AAC2-repressed strain and in yeast cells with inhibited ATP synthase. Importantly, treatment with the ATP synthase inhibitor oligomycin A also induced mitochondrial fragmentation and hyperpolarization. Taken together, our data suggest that ATP/ADP translocation plays a crucial role in shaping of the mitochondrial network and exemplify that an increase in mitochondrial membrane potential does not necessarily oppose mitochondrial fragmentation.
线粒体网络结构会动态适应细胞代谢挑战。特别是线粒体去极化会诱导网络的碎片化。这种碎片化可能是跨膜电位直接调节线粒体融合机制的结果，也可能是代谢重塑的间接影响。ATP 合酶和腺嘌呤核苷酸转运蛋白（ANT）的活性将线粒体跨膜电位与细胞质 NTP/NDP 比联系起来。鉴于线粒体融合需要细胞质 GTP，NTP/NDP 比的降低也可能解释质子载体诱导的线粒体碎片化。为了评估直接和间接机制对线粒体重塑的贡献，我们评估了抑制 ANT 的酵母细胞中线粒体网络的形态。我们表明，抑制酵母中主要的 ANT 基因 AAC2（PET9）会增加线粒体跨膜电位。然而，该菌株的线粒体网络发生了碎片化。同时，AAC2 抑制并没有阻止合子中的线粒体融合；也没有抑制 Dnm1p 抑制剂 mdivi-1 诱导的线粒体过度融合。这些结果表明，ANT 的抑制不是阻止线粒体融合，而是促进线粒体分裂。质子载体在 AAC2 抑制的菌株和抑制 ATP 合酶的酵母细胞中不能诱导额外的线粒体碎片化。重要的是，ATP 合酶抑制剂寡霉素 A 的处理也诱导了线粒体碎片化和超极化。总之，我们的数据表明，ATP/ADP 转运在塑造线粒体网络方面起着至关重要的作用，并证明线粒体膜电位的增加不一定与线粒体碎片化相矛盾。
