Positive Feedback Loop Between PI3K-Akt-mTORC1 Signaling and the Lipogenic Pathway Boosts Akt Signaling: Induction of the Lipogenic Pathway by a Melanoma Antigen

  • Yoshio Yamauchi
    Authors' Affiliations: 1Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya; and 2Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Kasugai, Aichi, Japan
  • Keiko Furukawa
    Authors' Affiliations: 1Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya; and 2Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Kasugai, Aichi, Japan
  • Kazunori Hamamura
    Authors' Affiliations: 1Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya; and 2Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Kasugai, Aichi, Japan
  • Koichi Furukawa
    Authors' Affiliations: 1Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya; and 2Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Kasugai, Aichi, Japan

抄録

<jats:title>Abstract</jats:title> <jats:p>The lipogenic phenotype is a metabolic hallmark of cancer cells. Sterol regulatory element–binding proteins (SREBP) are key transcriptional factors to regulate biosynthesis of cholesterol and fatty acids. It has been poorly understood how the lipogenic phenotype in cancer cells is regulated and how it augments their malignant properties. Here we describe roles of the melanoma antigen ganglioside GD3 and phosphatidylinositol 3-kinase (PI3K)-Akt-mTOR complex 1 (mTORC1) signaling in the regulation of SREBP activity, cholesterol biosynthesis, and the integrity of lipid rafts in human melanoma cells. GD3 expression induced the activation of both SREBP-1 and SREBP-2. Consequently, HMG-CoA reductase expression and cholesterol biosynthesis increased. The activation of the SREBP pathway was independent of the oncogenic BRAF mutation. On the other hand, it was regulated by PI3K-Akt-mTORC1 signaling in human melanoma cells. Disruption of the signaling pathway resulted in the reduction of cholesterol in lipid rafts. Inhibition of the SREBP pathway attenuated Akt activation in lipid rafts and suppressed the growth of human melanoma cells in vitro and in vivo. These results suggest that PI3K-Akt-mTORC1 signaling is important for the integrity of lipid rafts by regulating SREBP activation and subsequent cholesterogenesis. We thus propose a positive feedback circuit in which PI3K-Akt-mTORC1-SREBP signaling boosts Akt signaling in human melanoma cells expressing GD3. Cancer Res; 71(14); 4989–97. ©2011 AACR.</jats:p>

収録刊行物

  • Cancer Research

    Cancer Research 71 (14), 4989-4997, 2011-07-14

    American Association for Cancer Research (AACR)

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