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Identification of Intracellular Signaling Events Induced in Viable Cells by Interaction with Neighboring Cells Undergoing Apoptotic Cell Death
09:18

Identification of Intracellular Signaling Events Induced in Viable Cells by Interaction with Neighboring Cells Undergoing Apoptotic Cell Death

Published on: December 27, 2016

Mdm2 exerts pro-apoptotic activities by antagonizing insulin-like growth factor-I-mediated survival

Pascal Froment1, Joelle Dupont, Jean Christophe-Marine

  • 1Laboratory for Molecular Cancer Biology, VIB-UGent, Gent, Belgium.

Cell Cycle (Georgetown, Tex.)
|September 20, 2008
PubMed

Insights

Mdm2 protein regulates Insulin-like Growth Factor 1 Receptor (IGF-1R) levels and signaling. Loss of Mdm2 enhances IGF-1 protection against DNA damage-induced apoptosis, revealing a p53-independent role for Mdm2 in apoptosis.

Area of Science:

  • Oncogenesis
  • Molecular Biology
  • Cellular Signaling

Background:

  • Mdm2 oncoprotein is an E3 ubiquitin ligase crucial for maintaining low p53 protein levels.
  • Mdm2 amplification/overexpression contributes to tumor formation by antagonizing p53 tumor suppressor activity.
  • p53-independent roles for Mdm2 have been suggested, involving regulation of cell proliferation proteins.

Purpose of the Study:

  • To investigate the physiological role of Mdm2 in controlling Insulin-like Growth Factor 1 Receptor (IGF-1R) signaling.
  • To determine if Mdm2's regulation of IGF-1R is dependent on p53.
  • To explore the impact of Mdm2 loss on IGF-1-mediated protection against DNA-damage-induced apoptosis.

Main Methods:

  • Western blot analysis to assess protein levels of Mdm2, p53, and IGF-1R-beta.
  • Cell culture experiments using cells with and without p53.
  • Apoptosis assays following DNA damage induction and IGF-1 treatment.

Main Results:

  • Loss of Mdm2 significantly increased IGF1-R-beta protein levels, irrespective of p53 status.
  • Mdm2 facilitates ubiquitylation and proteasome degradation of IGF-1R, independent of p53.
  • Insulin-like Growth Factor 1 (IGF-1) protected cells from DNA-damage-induced apoptosis only in the absence of Mdm2.

Conclusions:

  • Mdm2 plays a physiological role in regulating IGF1 signaling.
  • Mdm2 exhibits a p53-independent proapoptotic function.
  • These findings highlight Mdm2's involvement in cellular responses to DNA damage and its regulation of growth factor signaling pathways.

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