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Evaluation of Substrate Ubiquitylation by E3 Ubiquitin-ligase in Mammalian Cell Lysates
09:47

Evaluation of Substrate Ubiquitylation by E3 Ubiquitin-ligase in Mammalian Cell Lysates

Published on: May 10, 2022

Noxa controls Mule-dependent Mcl-1 ubiquitination through the regulation of the Mcl-1/USP9X interaction

Patricia Gomez-Bougie1, Emmanuelle Ménoret, Philippe Juin

  • 1INSERM, UMR892, Université de Nantes, Nantes Atlantique Universités, UFR Médecine et Techniques Médicales, 44093 Nantes, France.

Biochemical and Biophysical Research Communications
|September 13, 2011
PubMed

Insights

Noxa protein triggers the degradation of the Mcl-1 survival protein by promoting its polyubiquitination and preventing deubiquitination. This mechanism involves the E3 ligase Mule and affects the USP9X interaction, leading to Mcl-1 proteasomal degradation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Mcl-1 is a pro-survival protein crucial for regulating apoptosis.
  • Mcl-1 levels are tightly controlled, and its down-regulation promotes cell death.
  • Noxa, a BH3-only protein, modulates Mcl-1 expression and stability.

Purpose of the Study:

  • To investigate the mechanism by which Noxa influences Mcl-1 degradation.
  • To elucidate the roles of E3 ligases and deubiquitinases in Noxa-mediated Mcl-1 turnover.
  • To understand the complex interactions governing Mcl-1 proteasomal degradation.

Main Methods:

  • Mitochondrial localization studies of Noxa.
  • Analysis of Mcl-1 polyubiquitination and degradation.
  • Investigation of protein-protein interactions: Noxa-Mcl-1, Mule-Mcl-1, USP9X-Mcl-1, and Mule-USP9X.
  • Assessment of Noxa's effect on deubiquitination processes.

Main Results:

  • Noxa induces Mcl-1 degradation specifically at the mitochondria.
  • Noxa-induced Mcl-1 degradation requires the E3 ligase Mule for polyubiquitination.
  • Noxa overexpression disrupts the USP9X-Mcl-1 interaction, increasing Mcl-1 polyubiquitination.
  • Noxa enhances the Mule-Mcl-1 interaction while reducing the Mule-USP9X complex.

Conclusions:

  • Noxa triggers Mcl-1 proteasomal degradation by promoting its ubiquitination via Mule and inhibiting USP9X-mediated deubiquitination.
  • The interplay between Noxa, Mule, USP9X, and Mcl-1 highlights a complex regulatory network controlling Mcl-1 stability.
  • Understanding this pathway offers insights into therapeutic strategies targeting Mcl-1 in cancer.

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