Department of Surgery, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA.
Free Radic Biol Med. 2012 Nov 1;53(9):1782-90. doi: 10.1016/j.freeradbiomed.2012.07.025. Epub 2012 Jul 27.
Apurinic/apyrimidinic endonuclease 1 (Ape1/Ref-1) is a multifunctional protein critical for cellular survival. Its involvement in adaptive survival responses includes key roles in redox sensing, transcriptional regulation, and repair of DNA damage via the base excision repair (BER) pathway. Ape1 is abundant in most cell types and central in integrating the first BER step catalyzed by different DNA glycosylases. BER is the main process for removal of oxidative DNA lesions in postmitotic brain cells, and after ischemic brain injury preservation of Ape1 coincides with neuronal survival, while its loss has been associated with neuronal death. Here, we report that in cultured primary neurons, diminution of cellular ATP by either oligomycin or H(2)O(2) is accompanied by depletion of nuclear Ape1, while other BER proteins are unaffected and retain their nuclear localization under these conditions. Importantly, while H(2)O(2) induces γH2AX phosphorylation, indicative of chromatin rearrangements in response to DNA damage, oligomycin does not. Furthermore, despite comparable diminution of ATP content, H(2)O(2) and oligomycin differentially affect critical parameters of mitochondrial respiration that ultimately determine cellular ATP content. Taken together, our findings demonstrate that in neurons, nuclear compartmentalization of Ape1 depends on ATP and loss of nuclear Ape1 reflects disruption of neuronal energy homeostasis. Energy crisis is a hallmark of stroke and other ischemic/hypoxic brain injuries. In vivo studies have shown that Ape1 deficit precedes neuronal loss in injured brain regions. Thus, our findings bring to light the possibility that energy failure-induced Ape1 depletion triggers neuronal death in ischemic brain injuries.
脱嘌呤/脱嘧啶核酸内切酶 1（Ape1/Ref-1）是一种多功能蛋白，对细胞存活至关重要。其参与适应性存活反应包括在氧化还原感应、转录调控以及通过碱基切除修复（BER）途径修复 DNA 损伤方面的关键作用。Ape1 在大多数细胞类型中含量丰富，并且在整合由不同 DNA 糖苷酶催化的 BER 第一步中起着核心作用。BER 是切除有丝分裂后脑细胞中氧化 DNA 损伤的主要过程，缺血性脑损伤后 Ape1 的保留与神经元存活一致，而其缺失与神经元死亡有关。在这里，我们报告在培养的原代神经元中，寡霉素或 H2O2 使细胞内 ATP 减少会伴随着核 Ape1 的耗竭，而其他 BER 蛋白不受影响，并在这些条件下保留其核定位。重要的是，虽然 H2O2 诱导 γH2AX 磷酸化，表明染色质对 DNA 损伤的重排，但寡霉素不会。此外，尽管 ATP 含量有可比性的减少，H2O2 和寡霉素对线粒体呼吸的关键参数有不同的影响，最终决定细胞内 ATP 的含量。总之，我们的研究结果表明，在神经元中，Ape1 的核区室化依赖于 ATP，核 Ape1 的丢失反映了神经元能量稳态的破坏。能量危机是中风和其他缺血/缺氧性脑损伤的标志。体内研究表明，Ape1 缺陷先于损伤脑区的神经元丢失。因此，我们的研究结果揭示了能量衰竭诱导的 Ape1 耗竭可能触发缺血性脑损伤中的神经元死亡的可能性。
