PARP-1 Modulation of mTOR Signaling in Response to a DNA Alkylating Agent
PARP-1 Modulation of mTOR Signaling in Response to a DNA Alkylating Agent
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DOI：
10.1371/journal.pone.0047978
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发表时间：
2012-10-24
期刊：
影响因子：
3.7
通讯作者：
Poirier, Guy G.
中科院分区：
文献类型：
--
作者：
Ethier, Chantal;Tardif, Maxime;Poirier, Guy G.
多聚腺苷二磷酸核糖聚合酶-1（Poly（ADP-ribose）polymerase-1，PARP-1）广泛参与细胞死亡反应。根据损伤程度和细胞类型，PARP激活可能导致自噬、凋亡或坏死。在暴露于烷基化剂N-甲基-N '-硝基-N'-亚硝基鸟苷（MNNG）的HEK 293细胞中，我们表明PARP-1激活会触发坏死细胞死亡反应。PARP-1激活后大量聚腺苷二磷酸核糖（PAR）的合成导致mTORC 1通路的调节。MNNG暴露后不久，NAD+和ATP水平下降，而AMP水平急剧增加。我们在分子水平上表征了这些改变的核苷酸水平的后果。首先，AMP活化蛋白激酶（AMPK）被激活，mTORC 1通路被Raptor的磷酸化抑制，试图保持细胞能量。mTORC 1靶点S6的磷酸化以及mTORC 2组分Rictor在Thr 1135上的磷酸化均减少。最后，Ser 473上的Akt磷酸化丧失，然后发生坏死导致的细胞死亡。用有效的PARP抑制剂AG 14361抑制PARP-1可预防所有这些事件。此外，抗氧化剂N-乙酰-L-半胱氨酸（NAC）也可以消除由MNNG暴露引起的所有信号传导事件，表明活性氧（ROS）的产生参与PARP-1激活和mTOR信号传导的调节。在这项研究中，我们表明，PARP-1激活和PAR合成影响细胞的能量状态，抑制mTORC 1信号通路，并可能调节mTORC 2复合物影响细胞命运。这些结果提供了新的证据，即坏死引起的细胞死亡是由几种信号通路之间的平衡协调的，并且PARP-1和PAR参与了这些事件。
Poly(ADP-ribose) polymerase-1 (PARP-1) is widely involved in cell death responses. Depending on the degree of injury and on cell type, PARP activation may lead to autophagy, apoptosis or necrosis. In HEK293 cells exposed to the alkylating agent N-methyl-N'-nitro-N'-nitrosoguanine (MNNG), we show that PARP-1 activation triggers a necrotic cell death response. The massive poly(ADP-ribose) (PAR) synthesis following PARP-1 activation leads to the modulation of mTORC1 pathway. Shortly after MNNG exposure, NAD+ and ATP levels decrease, while AMP levels drastically increase. We characterized at the molecular level the consequences of these altered nucleotide levels. First, AMP-activated protein kinase (AMPK) is activated and the mTORC1 pathway is inhibited by the phosphorylation of Raptor, in an attempt to preserve cellular energy. Phosphorylation of the mTORC1 target S6 is decreased as well as the phosphorylation of the mTORC2 component Rictor on Thr1135. Finally, Akt phosphorylation on Ser473 is lost and then, cell death by necrosis occurs. Inhibition of PARP-1 with the potent PARP inhibitor AG14361 prevents all of these events. Moreover, the antioxidant N-acetyl-L-cysteine (NAC) can also abrogate all the signaling events caused by MNNG exposure suggesting that reactive oxygen species (ROS) production is involved in PARP-1 activation and modulation of mTOR signaling. In this study, we show that PARP-1 activation and PAR synthesis affect the energetic status of cells, inhibit the mTORC1 signaling pathway and possibly modulate the mTORC2 complex affecting cell fate. These results provide new evidence that cell death by necrosis is orchestrated by the balance between several signaling pathways, and that PARP-1 and PAR take part in these events.