Department of Anatomy and Regenerative Biology, George Washington University Medical Center, 2300 I Street N.W., Washington, DC 20037, U.S.A.
ASN Neuro. 2010 May 24;2(2):e00034. doi: 10.1042/AN20100005.
Preserving mitochondrial mass, bioenergetic functions and ROS (reactive oxygen species) homoeostasis is key to neuronal differentiation and survival, as mitochondria produce most of the energy in the form of ATP to execute and maintain these cellular processes. In view of our previous studies showing that NeuroD6 promotes neuronal differentiation and survival on trophic factor withdrawal, combined with its ability to stimulate the mitochondrial biomass and to trigger comprehensive antiapoptotic and molecular chaperone responses, we investigated whether NeuroD6 could concomitantly modulate the mitochondrial biomass and ROS homoeostasis on oxidative stress mediated by serum deprivation. In the present study, we report a novel role of NeuroD6 as a regulator of ROS homoeostasis, resulting in enhanced tolerance to oxidative stress. Using a combination of flow cytometry, confocal fluorescence microscopy and mitochondrial fractionation, we found that NeuroD6 sustains mitochondrial mass, intracellular ATP levels and expression of specific subunits of respiratory complexes upon oxidative stress triggered by withdrawal of trophic factors. NeuroD6 also maintains the expression of nuclear-encoded transcription factors, known to regulate mitochondrial biogenesis, such as PGC-1alpha (peroxisome-proliferator-activated receptor gamma co-activator-1alpha), Tfam (transcription factor A, mitochondrial) and NRF-1 (nuclear respiratory factor-1). Finally, NeuroD6 triggers a comprehensive antioxidant response to endow PC12-ND6 cells with intracellular ROS scavenging capacity. The NeuroD6 effect is not limited to the classic induction of the ROS-scavenging enzymes, such as SOD2 (superoxide dismutase 2), GPx1 (glutathione peroxidase 1) and PRDX5 (peroxiredoxin 5), but also to the recently identified powerful ROS suppressors PGC-1alpha, PINK1 (phosphatase and tensin homologue-induced kinase 1) and SIRT1. Thus our collective results support the concept that the NeuroD6-PGC-1alpha-SIRT1 neuroprotective axis may be critical in co-ordinating the mitochondrial biomass with the antioxidant reserve to confer tolerance to oxidative stress.
维持线粒体质量、生物能量功能和 ROS（活性氧）稳态对于神经元分化和存活至关重要，因为线粒体以 ATP 的形式产生大部分能量，以执行和维持这些细胞过程。鉴于我们之前的研究表明 NeuroD6 在营养因子缺失时促进神经元分化和存活，并且它能够刺激线粒体生物量并引发全面的抗凋亡和分子伴侣反应，我们研究了 NeuroD6 是否可以同时调节线粒体生物量和 ROS 稳态在血清剥夺介导的氧化应激下。在本研究中，我们报道了 NeuroD6 作为 ROS 稳态调节剂的新作用，从而增强了对氧化应激的耐受性。通过流式细胞术、共聚焦荧光显微镜和线粒体分离，我们发现 NeuroD6 在营养因子缺失引发的氧化应激下维持线粒体质量、细胞内 ATP 水平和呼吸复合物特定亚基的表达。NeuroD6 还维持核编码转录因子的表达，这些转录因子已知调节线粒体生物发生，如 PGC-1alpha（过氧化物酶体增殖物激活受体γ共激活因子 1α）、Tfam（线粒体转录因子 A）和 NRF-1（核呼吸因子-1）。最后，NeuroD6 引发全面的抗氧化反应，使 PC12-ND6 细胞具有细胞内 ROS 清除能力。NeuroD6 的作用不仅限于经典诱导 ROS 清除酶，如 SOD2（超氧化物歧化酶 2）、GPx1（谷胱甘肽过氧化物酶 1）和 PRDX5（过氧化物酶 5），还包括最近发现的强大的 ROS 抑制剂 PGC-1alpha、PINK1（磷酸酶和张力蛋白同源物诱导激酶 1）和 SIRT1。因此，我们的综合结果支持这样的概念，即 NeuroD6-PGC-1alpha-SIRT1 神经保护轴对于协调线粒体生物量与抗氧化储备以赋予对氧化应激的耐受性可能至关重要。
