Departments of Medical Biochemistry and Cardiovascular Medicine and Center for Research Education, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan.
Proc Natl Acad Sci U S A. 2014 Jan 7;111(1):273-8. doi: 10.1073/pnas.1318547111. Epub 2013 Dec 16.
The oxidative phosphorylation (OXPHOS) system generates most of the ATP in respiring cells. ATP-depleting conditions, such as hypoxia, trigger responses that promote ATP production. However, how OXPHOS is regulated during hypoxia has yet to be elucidated. In this study, selective measurement of intramitochondrial ATP levels identified the hypoxia-inducible protein G0/G1 switch gene 2 (G0s2) as a positive regulator of OXPHOS. A mitochondria-targeted, FRET-based ATP biosensor enabled us to assess OXPHOS activity in living cells. Mitochondria-targeted, FRET-based ATP biosensor and ATP production assay in a semiintact cell system revealed that G0s2 increases mitochondrial ATP production. The expression of G0s2 was rapidly and transiently induced by hypoxic stimuli, and G0s2 interacts with OXPHOS complex V (FoF1-ATP synthase). Furthermore, physiological enhancement of G0s2 expression prevented cells from ATP depletion and induced a cellular tolerance for hypoxic stress. These results show that G0s2 positively regulates OXPHOS activity by interacting with FoF1-ATP synthase, which causes an increase in ATP production in response to hypoxic stress and protects cells from a critical energy crisis. These findings contribute to the understanding of a unique stress response to energy depletion. Additionally, this study shows the importance of assessing intramitochondrial ATP levels to evaluate OXPHOS activity in living cells.
氧化磷酸化（OXPHOS）系统在呼吸细胞中产生大部分的 ATP。ATP 耗竭条件，如缺氧，会引发促进 ATP 产生的反应。然而，OXPHOS 在缺氧条件下是如何被调节的还没有被阐明。在这项研究中，通过选择性测量线粒体内部的 ATP 水平，发现 G0/G1 开关基因 2（G0s2）作为 OXPHOS 的正调节剂。一种线粒体靶向的、基于 FRET 的 ATP 生物传感器使我们能够在活细胞中评估 OXPHOS 活性。线粒体靶向的、基于 FRET 的 ATP 生物传感器和半完整细胞系统中的 ATP 产生测定表明，G0s2 增加了线粒体的 ATP 产生。G0s2 被缺氧刺激快速且短暂地诱导表达，并且 G0s2 与 OXPHOS 复合物 V（FoF1-ATP 合酶）相互作用。此外，生理上增强 G0s2 的表达可以防止细胞 ATP 耗竭，并诱导细胞对缺氧应激的耐受。这些结果表明，G0s2 通过与 FoF1-ATP 合酶相互作用，正向调节 OXPHOS 活性，导致在缺氧应激时增加 ATP 产生，并保护细胞免受关键的能量危机。这些发现有助于理解对能量耗竭的独特应激反应。此外，这项研究表明评估活细胞中线粒体内部 ATP 水平对于评估 OXPHOS 活性的重要性。
