Reactive nitrogen species regulate autophagy through ATM-AMPK-TSC2-mediated suppression of mTORC1
Reactive nitrogen species regulate autophagy through ATM-AMPK-TSC2-mediated suppression of mTORC1
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DOI：
10.1073/pnas.1307736110
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发表时间：
2013-08-06
影响因子：
11.1
通讯作者：
Wogan, Gerald N.
中科院分区：
文献类型：
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作者：
Tripathi, Durga N.;Chowdhury, Rajdeep;Wogan, Gerald N.
活性中间体（例如活性氮）作为信号分子在细胞中发挥着重要作用，但过量时会构成细胞损伤的主要来源。我们发现稳态一氧化氮 (NO) 诱导的亚硝化应激会导致 ATM 损伤反应途径快速激活，从而导致该应激激酶向 LKB1 和 AMPK 激酶发出下游信号，并激活 TSC 肿瘤抑制因子。结果，mTORC1 以 ATM、LKB1、TSC 依赖性方式受到抑制，mTORC1 激酶的直接靶标 S6K、4E-BP1 和 ULK1 的磷酸化降低证明了这一点。响应亚硝化应激，mTORC1 在 S757 处减少 ULK1 磷酸化，并激活 AMPK 在 S317 处磷酸化 ULK1，导致自噬增加：LC3-II/LC3-I 比率增加，GFP-LC3 斑点和酸性囊泡也增加； p62 水平以溶酶体依赖性方式下降，证实了 NO 诱导的自噬通量增加。 NO 诱导的自噬与细胞活力的丧失相关，这表明在这种情况下，自噬主要作为对过量亚硝化应激的细胞毒性反应发挥作用。这些数据确定了一条亚硝化应激信号通路，该通路与 ATM 以及 LKB1 和 TSC2 肿瘤抑制因子结合，抑制 mTORC1 并调节自噬。由于癌细胞对亚硝化应激特别敏感，这些数据为利用活性氮诱导自噬介导的细胞死亡的能力的治疗开辟了另一条途径。
Reactive intermediates such as reactive nitrogen species play essential roles in the cell as signaling molecules but, in excess, constitute a major source of cellular damage. We found that nitrosative stress induced by steady-state nitric oxide (NO) caused rapid activation of an ATM damage-response pathway leading to downstream signaling by this stress kinase to LKB1 and AMPK kinases, and activation of the TSC tumor suppressor. As a result, in an ATM-, LKB1-, TSC-dependent fashion, mTORC1 was repressed, as evidenced by decreased phosphorylation of S6K, 4E-BP1, and ULK1, direct targets of the mTORC1 kinase. Decreased ULK1 phosphorylation by mTORC1 at S757 and activation of AMPK to phosphorylate ULK1 at S317 in response to nitrosative stress resulted in increased autophagy: the LC3-II/LC3-I ratio increased as did GFP-LC3 puncta and acidic vesicles; p62 levels decreased in a lysosome-dependent manner, confirming an NO-induced increase in autophagic flux. Induction of autophagy by NO correlated with loss of cell viability, suggesting that, in this setting, autophagy was functioning primarily as a cytotoxic response to excess nitrosative stress. These data identify a nitrosative-stress signaling pathway that engages ATM and the LKB1 and TSC2 tumor suppressors to repress mTORC1 and regulate autophagy. As cancer cells are particularly sensitive to nitrosative stress, these data open another path for therapies capitalizing on the ability of reactive nitrogen species to induce autophagy-mediated cell death.