Involvement of mitophagy in oncogenic K-Ras-induced transformation: Overcoming a cellular energy deficit from glucose deficiency

June Hyung Kim, Hee Young Kim, Young Kyoung Lee, Young Sil Yoon, Wei Guang Xu, Joon Kee Yoon, Sung E. Choi, Young Gyu Ko, Min Jung Kim, Su Jae Lee, Hee Jung Wang, Gyesoon Yoon

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62 Citations (Scopus)

Abstract

Although mitochondrial impairment has often been implicated in carcinogenesis, the mechanisms of its development in cancer remain unknown. We report here that autophagy triggered by oncogenic K-Ras mediates functional loss of mitochondria during cell transformation to overcome an energy deficit resulting from glucose deficiency. When Rat2 cells were infected with a retrovirus harboring constitutively active K-RasV12, mitochondrial respiration significantly declined in parallel with the acquisition of transformation characteristics. Decreased respiration was not related to mitochondrial biogenesis but was inversely associated with the increased formation of acidic vesicles enclosing mitochondria, during which autophagy-related proteins such as Beclin 1, Atg5, LC3-II and vacuolar ATPases were induced. Interestingly, blocking autophagy with conventional inhibitors (bafilomycin A, 3-methyladenin) and siRNA-mediated knockdown of autophagy-related genes recovered respiratory protein expression and respiratory activity; JNK was involved in these phenomena as an upstream regulator. The cells transformed by K-RasV12 maintained cellular ATP level mainly through glycolytic ATP production without induction of GLUT1, the low K m glucose transporter. Finally, K-RasV12-triggered LC3-II formation was modulated by extracellular glucose levels, and LC3-II formation increased only in hepatocellular carcinoma tissues exhibiting low glucose uptake and increased K-Ras expression. Taken together, our observations suggest that mitochondrial functional loss may be mediated by oncogenic K-Ras-induced mitophagy during early tumorigenesis even in the absence of hypoxia, and that this mitophagic process may be an important strategy to overcome the cellular energy deficit triggered by insufficient glucose.

Original languageEnglish
Pages (from-to)1187-1198
Number of pages12
JournalAutophagy
Volume7
Issue number10
DOIs
Publication statusPublished - 2011 Oct

Keywords

  • Cell transformation
  • Energy deficit
  • K-Ras
  • Mitochondrial loss
  • Mitophagy

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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  • Cite this

    Kim, J. H., Kim, H. Y., Lee, Y. K., Yoon, Y. S., Xu, W. G., Yoon, J. K., Choi, S. E., Ko, Y. G., Kim, M. J., Lee, S. J., Wang, H. J., & Yoon, G. (2011). Involvement of mitophagy in oncogenic K-Ras-induced transformation: Overcoming a cellular energy deficit from glucose deficiency. Autophagy, 7(10), 1187-1198. https://doi.org/10.4161/auto.7.10.16643