Abstract

The PI(3)K–PKB–FOXO signalling network provides a major intracellular hub for the regulation of cell proliferation, survival and stress resistance. Here we report an unexpected role for FOXO transcription factors in regulating autophagy by modulating intracellular glutamine levels. To identify transcriptional targets of this network, we performed global transcriptional analyses after conditional activation of the key components PI(3)K, PKB/Akt, FOXO3 and FOXO4. Using this pathway approach, we identified glutamine synthetase as being transcriptionally regulated by PI(3)K–PKB–FOXO signalling. Conditional activation of FOXO also led to an increased level of glutamine production. FOXO activation resulted in mTOR inhibition by preventing the translocation of mTOR to lysosomal membranes in a glutamine-synthetase-dependent manner. This resulted in an increased level of autophagy as measured by LC3 lipidation, p62 degradation and fluorescent imaging of multiple autophagosomal markers. Inhibition of FOXO3-mediated autophagy increased the level of apoptosis, suggesting that the induction of autophagy by FOXO3-mediated glutamine synthetase expression is important for cellular survival. These findings reveal a growth-factor-responsive network that can directly modulate autophagy through the regulation of glutamine metabolism.

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Acknowledgements

We thank R. Korswagen for helpful discussions. K.E.v.d.V. was supported by a grant from the Dutch Scientific Organisation (NWO-VIDI), R.G. was supported by grants (0313081F and 0315735, Virtual Liver) from the German Federal Ministry of Education and Research (BMBF), T.P-C. was supported by the German Research Foundation (DFG; SFB 773, A03), R.v.B. was supported by a grant from CTMM and L.P.V. was supported by a grant from NIRM.

Author information

Author notes

    • Kristan E. van der Vos

    Present address: Departments of Neurology and Radiology, Massachusetts General Hospital, and Neuroscience Program, Harvard Medical School, Boston, Massachusetts 02129, USA

    • Pernilla Eliasson
    •  & Tassula Proikas-Cezanne

    These authors contributed equally to this work

Affiliations

  1. Department of Immunology, University Medical Center Utrecht, Utrecht 3584CX, The Netherlands

    • Kristan E. van der Vos
    •  & Paul J. Coffer
  2. Department of Cell Biology, University Medical Center Utrecht, Utrecht 3584CX, The Netherlands

    • Pernilla Eliasson
    • , Stephin J. Vervoort
    • , Ruben van Boxtel
    • , Cornelieke Pals
    • , Liesbeth P. Verhagen
    • , A. Koen Braat
    •  & Paul J. Coffer
  3. Autophagy Laboratory, Interfaculty Institute for Cell Biology, University of Tuebingen, Tuebingen 72076, Germany

    • Tassula Proikas-Cezanne
    •  & Mario Mauthe
  4. Department of Molecular Cancer Research, University Medical Center, Utrecht 3584CX, The Netherlands

    • Marrit Putker
    • , Iris J. van Zutphen
    • , Marian J. A. Groot Koerkamp
    • , Tobias B. Dansen
    • , Frank C. Holstege
    •  & Boudewijn M. Burgering
  5. Institut für Biochemie, Medizinische Fakultät, Universität Leipzig, Leipzig 04103, Germany

    • Sebastian Zellmer
    •  & Rolf Gebhardt
  6. Center for Molecular and Cellular Intervention, Wilhelmina Children’s Hospital, Utrecht 3584EA, The Netherlands

    • Stephin J. Vervoort
    • , A. Koen Braat
    •  & Paul J. Coffer

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Contributions

K.E.v.d.V. was involved in experimental strategy and design, performed experiments, analysed data and wrote the paper. P.E., S.J.V., R.v.B., M.P., I.J.v.Z., M.M., S.Z., C.P., L.P.V., M.J.A.G.K., A.K.B. and T.B.D. performed experiments. T.P-C., F.C.H., R.G. and B.M.B. were involved in experimental design. P.J.C. was involved in experimental strategy and design and wrote the paper.

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The authors declare no competing financial interests.

Corresponding author

Correspondence to Paul J. Coffer.

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https://doi.org/10.1038/ncb2536

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