Autophagy-dependent senescence in response to DNA damage and chronic apoptotic stress
Autophagy-dependent senescence in response to DNA damage and chronic apoptotic stress
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DOI：
10.4161/auto.8.2.18600
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发表时间：
2012-02-01
期刊：
影响因子：
13.3
通讯作者：
Almasan, Alexandru
中科院分区：
文献类型：
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作者：
Singh, Kamini;Matsuyama, Shigemi;Almasan, Alexandru
自噬调节细胞在各种细胞胁迫下的生存和死亡，但所涉及的分子信号事件尚未明确。在这里，我们建立了蛋白水解细胞周期蛋白E片段（p18-CycE）在DNA损伤诱导的自噬、凋亡和衰老中的功能。p18-CycE在DNA损伤诱导的造血细胞凋亡中被鉴定出来。在暴露于DNA损伤的上皮细胞中，慢性但非短暂的p18-CycE表达导致LC3 I/II的高周转率和自噬体和自溶体的出现增加。p18-CycE是由内源性Cyclin E的蛋白水解裂解产生的，在氯喹的作用下，p18-CycE的水平大大增加，并与LC 3II的转化相关。阻止p18-CycE的发生阻断了LC3 I向LC3 II的转化。DNA损伤后，表达p18- cyce的细胞中细胞质失调性毛细血管扩张突变（ATM）磷酸化，导致腺苷单磷酸依赖性激酶（AMPK）持续激活。这些导致哺乳动物自噬启动激酶ULK1的持续激活，该激酶在抑制ATM和AMPK磷酸化时被取消。此外，p18-CycE通过自噬降解，随后诱导衰老。抑制自噬可防止细胞自噬和衰老，通过稳定p18-CycE的表达，使表达p18-CycE的细胞凋亡增加。衰老进一步与细胞质共定位和p18-CycE和Ku70的降解有关。简而言之，慢性p18-CycE表达诱导的自噬导致DNA损伤后p18-CycE的清除和衰老的诱导。自噬抑制稳定了细胞质p18-CycE-Ku70复合物，导致细胞凋亡。因此，我们的研究结果定义了慢性凋亡应激和DNA损伤如何启动自噬并通过衰老和/或凋亡调节细胞存活。
Autophagy regulates cell survival and cell death upon various cellular stresses, yet the molecular signaling events involved are not well defined. Here, we established the function of a proteolytic Cyclin E fragment (p18-CycE) in DNA damage-induced autophagy, apoptosis, and senescence. p18-CycE was identified in hematopoietic cells undergoing DNA damage-induced apoptosis. In epithelial cells exposed to DNA damage, chronic but not transient expression of p18-CycE leads to higher turnover of LC3 I/II and increased emergence of autophagosomes and autolysosomes. Levels of p18-CycE, which was generated by proteolytic cleavage of endogenous Cyclin E, were greatly increased by chloroquine and correlated with LC 3II conversion. Preventing p18-CycE genesis blocked conversion of LC3 I to LC3 II. Upon DNA damage, cytoplasmic ataxia-telangiectasia-mutated (ATM) was phosphorylated in p18-CycE-expressing cells resulting in sustained activation of the adenosine-mono-phosphate-dependent kinase (AMPK). These lead to sustained activation of mammalian autophagy-initiating kinase ULK1, which was abrogated upon inhibiting ATM and AMPK phosphorylation. Moreover, p18-CycE was degraded via autophagy followed by induction of senescence. Both autophagy and senescence were prevented by inhibiting autophagy, which leads to increased apoptosis in p18-CycE-expressing cells by stabilizing p18-CycE expression. Senescence was further associated with cytoplasmic co-localization and degradation of p18-CycE and Ku70. In brief, chronic p18-CycE expression-induced autophagy leads to clearance of p18-CycE following DNA damage and induction of senescence. Autophagy inhibition stabilized the cytoplasmic p18-CycE-Ku70 complex leading to apoptosis. Thus, our findings define how chronic apoptotic stress and DNA damage initiate autophagy and regulate cell survival through senescence and/or apoptosis.