Laboratory of Bioenergetics and Mitochondrial Physiology, Institute of Medical Biochemistry Leopoldo de Meis, Center for Health Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
J Neurochem. 2019 Jun;149(5):624-640. doi: 10.1111/jnc.14705. Epub 2019 May 8.
The adult brain is a high-glucose and oxygen-dependent organ, with an extremely organized network of cells and large energy-consuming synapses. To reach this level of organization, early stages in development must include an efficient control of cellular events and regulation of intracellular signaling molecules and ions such as hydrogen peroxide (H O ) and calcium (Ca ), but in cerebral tissue, these mechanisms of regulation are still poorly understood. Hexokinase (HK) is the first enzyme in the metabolism of glucose and, when bound to mitochondria (mtHK), it has been proposed to have a role in modulation of mitochondrial H O generation and Ca handling. Here, we have investigated how mtHK modulates these signals in the mitochondrial context during postnatal development of the mouse brain. Using high-resolution respirometry, western blot analysis, spectrometry and resorufin, and Calcium Green fluorescence assays with brain mitochondria purified postnatally from day 1 to day 60, we demonstrate that brain HK increases its coupling to mitochondria and to oxidative phosphorylation to induce a cycle of ADP entry/ATP exit of the mitochondrial matrix that leads to efficient control over H O generation and Ca uptake during development until reaching plateau at day 21. This contrasts sharply with the antioxidant enzymes, which do not increase as mitochondrial H O generation escalates. These results suggest that, as its use of glucose increases, the brain couples HK to mitochondria to improve glucose metabolism, redox balance and Ca signaling during development, positioning mitochondria-bound hexokinase as a hub for intracellular signaling control.
成人大脑是一个高葡萄糖和氧依赖性器官，具有极其组织化的细胞网络和大量能量消耗的突触。为了达到这种组织水平，早期发育阶段必须包括对细胞事件的有效控制和对细胞内信号分子和离子（如过氧化氢 (H O ) 和钙 (Ca ) ）的调节，但在脑组织中，这些调节机制仍知之甚少。己糖激酶 (HK) 是葡萄糖代谢的第一酶，当与线粒体结合 (mtHK) 时，它被提议在调节线粒体 H O 生成和 Ca 处理中发挥作用。在这里，我们研究了 mtHK 如何在小鼠大脑出生后发育的线粒体背景下调节这些信号。使用高分辨率呼吸测定法、western blot 分析、光谱法和 Resorufin 以及钙绿荧光测定法，我们从第 1 天到第 60 天纯化了出生后大脑中的线粒体，结果表明，脑 HK 增加了与线粒体和氧化磷酸化的结合，以诱导线粒体基质中 ADP 进入/ATP 输出的循环，从而在发育过程中对 H O 生成和 Ca 摄取进行有效控制，直到在第 21 天达到平台期。这与抗氧化酶形成鲜明对比，随着线粒体 H O 生成的增加，抗氧化酶并没有增加。这些结果表明，随着葡萄糖利用的增加，大脑将 HK 与线粒体结合以改善发育过程中的葡萄糖代谢、氧化还原平衡和 Ca 信号，使线粒体结合的己糖激酶成为细胞内信号控制的枢纽。
