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Detecting the Ligand-binding Domain Dimerization Activity of Estrogen Receptor Alpha Using the Mammalian Two-Hybrid Assay
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MDM2 restrains estrogen-mediated AKT activation by promoting TBK1-dependent HPIP degradation

K Shostak1, F Patrascu1, S I Göktuna1

  • 11] Interdisciplinary Cluster for Applied Genoproteomics, GIGA-Research, University of Liège, Liège, Belgium [2] Unit of Medical Chemistry, GIGA-Signal Transduction, GIGA-R, University of Liège, Liège, Belgium.

Cell Death and Differentiation
|February 4, 2014
PubMed

Insights

Inhibiting MDM2 to restore p53 tumor suppressor function may paradoxically activate oncogenic AKT signaling. This occurs because MDM2 inhibition stabilizes HPIP, a protein that promotes AKT activity, potentially limiting cancer therapy effectiveness.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cancer Therapeutics

Background:

  • MDM2 (E3 ligase) inhibition is a cancer therapy strategy by restoring p53 tumor suppressor function.
  • MDM2 targets proteins beyond p53, potentially activating oncogenic pathways.
  • HPIP (microtubule-associated protein) positively regulates oncogenic AKT signaling.

Purpose of the Study:

  • To investigate HPIP as a novel MDM2 substrate.
  • To explore the role of MDM2-HPIP interaction in breast cancer.
  • To understand the implications of MDM2 inhibition on AKT signaling.

Main Methods:

  • Identified HPIP as an MDM2 substrate.
  • Investigated MDM2-dependent HPIP degradation.
  • Analyzed estrogen-activated TBK1 kinase activity.
  • Assessed AKT signaling activation in response to Mdm2 gene dosage.
  • Examined HPIP as a p53 transcriptional target.

Main Results:

  • HPIP is degraded by MDM2 in breast cancer cells following phosphorylation by TBK1.
  • Reduced Mdm2 gene dosage enhances estrogen-dependent AKT activation via HPIP stabilization.
  • HPIP is a p53 transcriptional target.
  • MDM2 inhibition increases HPIP transcription and prevents HPIP degradation by inhibiting TBK1.

Conclusions:

  • p53 reactivation via MDM2 inhibition may lead to unintended AKT oncogenic activity.
  • Maintaining HPIP protein levels contributes to ectopic AKT oncogenic activity.
  • MDM2 inhibition strategies require careful consideration of off-target effects on oncogenic pathways.

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