Department of Medicine, University of Virginia, Charlottesville, VA 22908-0708, USA.
Cancer Res. 2010 Apr 1;70(7):2799-808. doi: 10.1158/0008-5472.CAN-09-4136. Epub 2010 Mar 23.
Human apurinic/apyrimidinic endonuclease-1 (APE-1), a key enzyme involved in repair of oxidative DNA base damage, is an important transcriptional coregulator. We previously reported that Helicobacter pylori infection induces apoptosis and increases APE-1 expression in human gastric epithelial cells (GEC). Although both the DNA repair activity and the acetylation-mediated transcriptional regulation of APE-1 are required to prevent cell death, the mechanisms of APE-1-mediated inhibition of infection-induced apoptosis are unclear. Here, we show that short hairpin RNA-mediated stable suppression of APE-1 results in increased apoptosis in GEC after H. pylori infection. We show that programmed cell death involves both the caspase-9-mediated mitochondrial pathway and the caspase-8-dependent extrinsic pathway by measuring different markers for both the pathways. Overexpression of wild-type APE-1 in APE-1-suppressed GEC reduced apoptosis after infection; however, overexpression of the DNA repair mutant or the nonacetylable mutant of APE-1 alone was unable to reduce apoptosis, suggesting that both DNA repair and acetylation functions of APE-1 modulate programmed cell death. We show for the first time that the DNA repair activity of APE-1 inhibits the mitochondrial pathway, whereas the acetylation function inhibits the extrinsic pathway during H. pylori infection. Thus, our findings establish that the two different functions of APE-1 differentially regulate the intrinsic and the extrinsic pathway of H. pylori-mediated GEC apoptosis. As proapoptotic and antiapoptotic mechanisms determine the development and progression of gastritis, gastric ulceration, and gastric cancer, this dual regulatory role of APE-1 represents one of the important molecular strategies by H. pylori to sustain chronic infection.
人类脱嘌呤/脱嘧啶核酸内切酶-1（APE-1）是一种参与修复氧化 DNA 碱基损伤的关键酶，也是一种重要的转录共调节因子。我们之前报道过，幽门螺杆菌感染诱导人胃上皮细胞（GEC）凋亡并增加 APE-1 的表达。尽管 APE-1 的 DNA 修复活性和乙酰化介导的转录调控都需要防止细胞死亡，但 APE-1 介导的抑制感染诱导的细胞凋亡的机制尚不清楚。在这里，我们显示短发夹 RNA 介导的 APE-1 稳定抑制导致 H. pylori 感染后 GEC 凋亡增加。我们通过测量两条途径的不同标志物来显示程序性细胞死亡涉及 caspase-9 介导的线粒体途径和 caspase-8 依赖性外在途径。在 APE-1 抑制的 GEC 中转染野生型 APE-1 可减少感染后的凋亡；然而，单独过表达 DNA 修复突变体或非乙酰化突变体均不能减少凋亡，这表明 APE-1 的 DNA 修复和乙酰化功能均调节程序性细胞死亡。我们首次表明 APE-1 的 DNA 修复活性抑制线粒体途径，而乙酰化功能在 H. pylori 感染期间抑制外在途径。因此，我们的发现表明 APE-1 的两种不同功能差异调节了 H. pylori 介导的 GEC 凋亡的内在和外在途径。由于促凋亡和抗凋亡机制决定了胃炎、胃溃疡和胃癌的发展和进展，因此 APE-1 的这种双重调节作用代表了 H. pylori 维持慢性感染的重要分子策略之一。
