Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Unit 1950, 1901 East Road, Houston, TX, 77054, USA.
Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
Mol Cell Biochem. 2021 Jan;476(1):417-423. doi: 10.1007/s11010-020-03917-1. Epub 2020 Sep 29.
Ataxia telangiectasia mutated (ATM), a critical DNA damage sensor, also possesses non-nuclear functions owing to its presence in extra-nuclear compartments, including peroxisomes, lysosomes, and mitochondria. ATM is frequently altered in several human cancers. Recently, we and others have shown that loss of ATM is associated with defective mitochondrial autophagy (mitophagy) in ataxia-telangiectasia (A-T) fibroblasts and B-cell lymphomas. Further, we reported that ATM protein but not ATM kinase activity is required for mitophagy. However, the mechanism of ATM kinase activation during ionophore-induced mitophagy is unknown. In the work reported here, using several ionophores in A-T and multiple T-cell and B-cell lymphoma cell lines, we show that ionophore-induced mitophagy triggers oxidative stress-induced ATM phosphorylation through ROS activation, which is different from neocarzinostatin-induced activation of ATM, Smc1, and Kap1. We used A-T cells overexpressed with WT or S1981A (auto-phosphorylation dead) ATM plasmids and show that ATM is activated by ROS-induced oxidative stress emanating from ionophore-induced mitochondrial damage and mitophagy. The antioxidants N-acetylcysteine and glutathione significantly inhibited ROS production and ATM phosphorylation but failed to inhibit mitophagy as determined by retroviral infection with mt-mKeima construct followed by lysosomal dual-excitation ratiometric pH measurements. Our data suggest that while ATM kinase does not participate in mitophagy, it is activated via elevated ROS.
共济失调毛细血管扩张突变基因（ATM）是一种关键的 DNA 损伤传感器，由于其存在于核外区室（包括过氧化物酶体、溶酶体和线粒体）中，因此具有非核功能。ATM 在几种人类癌症中经常发生改变。最近，我们和其他人已经表明，共济失调毛细血管扩张症（A-T）成纤维细胞和 B 细胞淋巴瘤中 ATM 的缺失与线粒体自噬（mitophagy）缺陷有关。此外，我们报告说 ATM 蛋白而不是 ATM 激酶活性是线粒体自噬所必需的。然而，离子载体诱导的线粒体自噬过程中 ATM 激酶的激活机制尚不清楚。在本报告中，我们使用几种离子载体在 A-T 和多种 T 细胞和 B 细胞淋巴瘤细胞系中进行研究，结果表明离子载体诱导的线粒体自噬通过 ROS 激活触发氧化应激诱导的 ATM 磷酸化，这与新制癌菌素诱导的 ATM、Smc1 和 Kap1 的激活不同。我们使用过表达 WT 或 S1981A（自动磷酸化失活）ATM 质粒的 A-T 细胞进行研究，并表明 ATM 通过源自离子载体诱导的线粒体损伤和线粒体自噬的 ROS 诱导的氧化应激而被激活。抗氧化剂 N-乙酰半胱氨酸和谷胱甘肽显著抑制 ROS 产生和 ATM 磷酸化，但未能抑制通过 mt-mKeima 构建体进行逆转录病毒感染后用溶酶体双激发比率 pH 测量来确定的线粒体自噬。我们的数据表明，虽然 ATM 激酶不参与线粒体自噬，但它通过升高的 ROS 被激活。
