The Rac1/MKK7/JNK pathway signals upregulation of Atg5 and subsequent autophagic cell death in response to oncogenic Ras

Joo Yun Byun, Chang Hwan Yoon, Sungkwan An, In Chul Park, Chang Mo Kang, Min Jung Kim, Su Jae Lee

Research output: Contribution to journalArticle

79 Citations (Scopus)

Abstract

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-rasV12 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-rasV12-induced cell death as well as autophagic vacuole formation. Selective production of Atg5 was observed in cells overexpressing H-rasV12, 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.

Original languageEnglish
Pages (from-to)1880-1888
Number of pages9
JournalCarcinogenesis
Volume30
Issue number11
DOIs
StatePublished - 2009 Dec 4

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Autophagy
Signal Transduction
Phosphotransferases
Up-Regulation
Oncogenes
Small Interfering RNA
Cell Death
JNK Mitogen-Activated Protein Kinases
Vacuoles
Fibroblasts
Caspase Inhibitors
Mitogens
Neoplasms

Cite this

Byun, Joo Yun ; Yoon, Chang Hwan ; An, Sungkwan ; Park, In Chul ; Kang, Chang Mo ; Kim, Min Jung ; Lee, Su Jae. / The Rac1/MKK7/JNK pathway signals upregulation of Atg5 and subsequent autophagic cell death in response to oncogenic Ras. In: Carcinogenesis. 2009 ; Vol. 30, No. 11. pp. 1880-1888.
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abstract = "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-rasV12 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-rasV12-induced cell death as well as autophagic vacuole formation. Selective production of Atg5 was observed in cells overexpressing H-rasV12, 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.",
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The Rac1/MKK7/JNK pathway signals upregulation of Atg5 and subsequent autophagic cell death in response to oncogenic Ras. / Byun, Joo Yun; Yoon, Chang Hwan; An, Sungkwan; Park, In Chul; Kang, Chang Mo; Kim, Min Jung; Lee, Su Jae.

In: Carcinogenesis, Vol. 30, No. 11, 04.12.2009, p. 1880-1888.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The Rac1/MKK7/JNK pathway signals upregulation of Atg5 and subsequent autophagic cell death in response to oncogenic Ras

AU - Byun, Joo Yun

AU - Yoon, Chang Hwan

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AU - Park, In Chul

AU - Kang, Chang Mo

AU - Kim, Min Jung

AU - Lee, Su Jae

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N2 - 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-rasV12 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-rasV12-induced cell death as well as autophagic vacuole formation. Selective production of Atg5 was observed in cells overexpressing H-rasV12, 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.

AB - 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-rasV12 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-rasV12-induced cell death as well as autophagic vacuole formation. Selective production of Atg5 was observed in cells overexpressing H-rasV12, 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.

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