AMP-activated protein kinase induces p53 by phosphorylating MDMX and inhibiting its activity

Area of Science:

• Cellular Biology
• Molecular Biology
• Biochemistry

Background:

• AMP-activated protein kinase (AMPK) is a key regulator of cellular energy homeostasis.
• AMPK activation by metabolic stress is known to influence p53 activity.
• The precise molecular mechanisms linking AMPK to p53 activation remain incompletely understood.

Purpose of the Study:

• To elucidate the mechanism by which AMPK activation by metabolic stress leads to p53 activation.
• To investigate the role of MDMX phosphorylation in this process.

Main Methods:

• In vitro and cellular assays to examine AMPK-mediated phosphorylation of MDMX.
• Co-immunoprecipitation to assess MDMX-14-3-3 binding.
• Western blotting to detect p53 ubiquitylation, stabilization, and activation.
• Use of mutant MDMX (S341A, S367A, S402A) and AMPK-deficient cells.
• In vivo studies using AMPK activators (metformin, salicylate) in cell and animal models.

Main Results:

• Metabolic stresses induce AMPK-mediated phosphorylation of MDMX at Ser342.
• Phosphorylated MDMX exhibits enhanced binding to 14-3-3 proteins.
• This interaction inhibits p53 ubiquitylation, leading to p53 stabilization and activation.
• AMPK does not phosphorylate MDM2.
• Mutations in MDMX phosphorylation sites and AMPK deficiency impair MDMX-14-3-3 binding and p53 activation.
• AMPK activators mimic these effects, confirming the pathway.

Conclusions:

• AMPK activation by metabolic stress phosphorylates MDMX, leading to its inactivation.
• This inactivation promotes p53 stabilization and activation, representing a novel regulatory pathway.
• This finding offers potential therapeutic targets for diseases involving p53 dysregulation.