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PDK1 controls upstream PI3K expression and PIP3 generation

A M Dieterle1, P Böhler2, H Keppeler1

  • 1Department of Internal Medicine I, University Hospital Tübingen, Tübingen, Germany.

Oncogene
|July 30, 2013
PubMed

Insights

This study reveals a new feedback loop where 3-phosphoinositide-dependent protein kinase 1 (PDK1) regulates phosphatidylinositol 3-kinase (PI3K) subunit levels. Inhibiting PDK1 or its effectors boosts PI3K, impacting cell survival and metabolism.

Area of Science:

  • Cellular signaling and molecular biology
  • Cancer biology and immunology

Background:

  • The PI3K/PDK1/Akt pathway is crucial for cell homeostasis, growth, and survival.
  • Dysregulation of this pathway is implicated in cancers and immunological diseases, making it a therapeutic target.
  • Known feedback loops attenuate PI3K/PDK1/Akt signaling, but additional regulatory mechanisms are being discovered.

Purpose of the Study:

  • To identify novel feedback mechanisms regulating the PI3K/PDK1/Akt signaling axis.
  • To investigate the transcriptional control of phosphatidylinositol 3-kinase (PI3K) class IA subunits.
  • To understand the role of 3-phosphoinositide-dependent protein kinase 1 (PDK1) as a cellular sensor.

Main Methods:

  • Genetic deletion of PDK1.
  • Pharmacological inhibition of Akt and mammalian target of rapamycin (mTOR).
  • Analysis of PI3K subunit expression and phosphatidylinositol-3,4,5-trisphosphate (PIP3) generation.
  • Investigation of transcription factor involvement (CREB, FOXO).

Main Results:

  • Genetic deletion or pharmacological inhibition of PDK1/Akt/mTOR leads to negative transcriptional suppression relief.
  • This results in the upregulation of PI3K class IA subunits.
  • Enhanced generation of PIP3 is observed, mediated by transcription factors like CREB and FOXO.
  • PDK1 appears to act as a sensor, balancing PIP3 levels for cell survival.

Conclusions:

  • A novel feedback loop involving negative transcriptional control of PI3K subunits by PDK1 has been identified.
  • PDK1 regulates cellular PIP3 levels, maintaining a balance for cell survival.
  • Targeting feedback circuits in parallel with the PI3K/PDK1/Akt pathway may enhance therapeutic efficacy.

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