Efficient extra-mitochondrial aerobic ATP synthesis in neuronal membrane systems,Journal of Neuroscience Research

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Efficient extra-mitochondrial aerobic ATP synthesis in neuronal membrane systems
Journal of Neuroscience Research ( IF 2.9 ) Pub Date : 2021-06-03 , DOI: 10.1002/jnr.24865
Silvia Ravera ₁ , Martina Bartolucci _{2,

3} , Daniela Calzia ₃ , Alessandro M Morelli ₃ , Isabella Panfoli ₃

Affiliation

The nervous system displays high energy consumption, apparently not fulfilled by mitochondria, which are underrepresented therein. The oxidative phosphorylation (OxPhos) activity, a mitochondrial process that aerobically provides ATP, has also been reported also in the myelin sheath and the rod outer segment (OS) disks. Thus, commonalities and differences between the extra-mitochondrial and mitochondrial aerobic metabolism were evaluated in bovine isolated myelin (IM), rod OS, and mitochondria-enriched fractions (MIT). The subcellular fraction quality and the absence of contamination fractions have been estimated by western blot analysis. Oxygen consumption and ATP synthesis were stimulated by conventional (pyruvate + malate or succinate) and unconventional (NADH) substrates, observing that oxygen consumption and ATP synthesis by IM and rod OS are more efficient than by MIT, in the presence of both kinds of respiratory substrates. Mitochondria did not utilize NADH as a respiring substrate. When ATP synthesis by either sample was assayed in the presence of 10–100 µM ATP in the assay medium, only in IM and OS it was not inhibited, suggesting that the ATP exportation by the mitochondria is limited by extravesicular ATP concentration. Interestingly, IM and OS but not mitochondria appear able to synthesize ATP at a later time with respect to exposure to respiratory substrates, supporting the hypothesis that the proton gradient produced by the electron transport chain is buffered by membrane phospholipids. The putative transfer mode of the OxPhos molecular machinery from mitochondria to the extra-mitochondrial structures is also discussed, opening new perspectives in the field of neurophysiology.

中文翻译：

神经元膜系统中有效的线粒体外需氧 ATP 合成

神经系统显示出高能量消耗，显然不能由线粒体来满足，线粒体在其中的代表性不足。氧化磷酸化 (OxPhos) 活性是一种有氧提供 ATP 的线粒体过程，在髓鞘和杆外段 (OS) 圆盘中也有报道。因此，在牛分离髓鞘 (IM)、棒状 OS 和富含线粒体的部分 (MIT) 中评估了线粒体外和线粒体有氧代谢之间的共性和差异。通过蛋白质印迹分析估计了亚细胞级分质量和无污染级分。常规（丙酮酸+苹果酸或琥珀酸）和非常规（NADH）底物刺激耗氧量和ATP合成，观察到在两种呼吸底物存在的情况下，IM 和棒状 OS 的耗氧量和 ATP 合成比 MIT 更有效。线粒体不利用 NADH 作为呼吸底物。当在测定培养基中存在 10–100 µM ATP 的情况下测定任一样品的 ATP 合成时，仅在 IM 和 OS 中它没有被抑制，这表明线粒体的 ATP 输出受到囊外 ATP 浓度的限制。有趣的是，在暴露于呼吸底物后，IM 和 OS 而不是线粒体似乎能够在稍后时间合成 ATP，这支持了电子传递链产生的质子梯度被膜磷脂缓冲的假设。

更新日期：2021-08-11

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