The Rac1/MKK7/JNK pathway signals upregulation of Atg5 and subsequent autophagic cell death in response to oncogenic Ras
The Rac1/MKK7/JNK pathway signals upregulation of Atg5 and subsequent autophagic cell death in response to oncogenic Ras
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DOI：
10.1093/carcin/bgp235
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发表时间：
2009-11-01
期刊：
影响因子：
4.7
通讯作者：
Lee, Su-Jae
中科院分区：
文献类型：
--
作者：
Byun, Joo-Yun;Yoon, Chang-Hwan;Lee, Su-Jae
为了防止恶性肿瘤的发展，哺乳动物细胞激活处理程序，如程序性细胞死亡，以响应癌基因表达的解除调控。然而，目前调控细胞处理机制以响应激活的癌基因的分子基础尚不清楚。在这项研究中，我们发现自噬相关蛋白ATG5的上调是H-ras致癌的自噬细胞死亡所必需的，而rac1/MKK/c-jun氨基末端激酶(JNK)是ATG5上调的信号。在正常成纤维细胞中，过表达H-ras(V12)可诱导显著的自噬空泡形成和细胞死亡，而caspase抑制剂对其无影响。用自噬抑制剂Bafilmycin A1预处理可完全减弱H-ras(V12)诱导的细胞死亡和自噬空泡的形成。在高表达H-ras(V12)的细胞中观察到ATG5的选择性产生，靶向ATG5的小干扰RNA(SiRNA)明显抑制自噬细胞的死亡。有趣的是，特异性siRNA抑制JNK或c-Jun可抑制ATG5上调和自噬细胞死亡。此外，抑制MKK7，而不是MKK4，有效地减弱了H-ras(V12)诱导的JNK激活。此外，异位表达racN17或rac1-siRNA可有效抑制MKK7-JNK激活、ATG5上调和自噬细胞死亡。这些数据支持ATG5上调是致癌H-ras诱导的正常成纤维细胞自噬细胞死亡所必需的，而rac1/MKK7/JNK-信号通路的激活导致ATG5上调是致癌H-ras反应的结果。我们的发现表明，在获得不受调控的癌基因表达的细胞中，致癌应激触发自噬细胞死亡，从而保护细胞免受恶性进展。
To prevent the development of malignancies, mammalian cells activate disposal programs, such as programmed cell death, in response to deregulated oncogene expression. However, the molecular basis for regulation of cellular disposal machinery in response to activated oncogenes is unclear at present. In this study, we show that upregulation of the autophagy-related protein, Atg5, is critically required for the oncogenic H-ras-induced autophagic cell death and that Rac1/mitogen-activated kinase kinase (MKK) 7/c-Jun N-terminal kinase (JNK) signals upregulation of Atg5. Overexpression of H-ras(V12) induced marked autophagic vacuole formation and cell death in normal fibroblasts, which remained unaffected by a caspase inhibitor. Pretreatment with Bafilomycin A1, an autophagy inhibitor, completely attenuated H-ras(V12)-induced cell death as well as autophagic vacuole formation. Selective production of Atg5 was observed in cells overexpressing H-ras(V12), and small interfering RNA (siRNA) targeting of Atg5 clearly inhibited autophagic cell death. Interestingly, inhibition of JNK or c-Jun by specific siRNA suppressed Atg5 upregulation and autophagic cell death. Moreover, inhibition of MKK7, but not MKK4, effectively attenuated H-ras(V12)-induced JNK activation. In addition, ectopic expression of RacN17 or Rac1-siRNA effectively inhibited MKK7-JNK activation, Atg5 upregulation and autophagic cell death. These data support the notion that upregulation of Atg5 is required for the oncogenic H-ras-induced autophagic cell death in normal fibroblasts and that activation of Rac1/MKK7/JNK-signaling pathway leads to upregulation of Atg5 in response to oncogenic H-ras. Our findings suggest that in cells acquiring deregulated oncogene expression, oncogenic stress triggers autophagic cell death, which protects cells against malignant progression.