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Published on: March 9, 2012

p38alpha antagonizes p38gamma activity through c-Jun-dependent ubiquitin-proteasome pathways in regulating Ras

Xiaomei Qi1, Nicole M Pohl, Mathew Loesch

  • 1Department of Pharmacology and Toxicology, Zablocki Department of Veterans Affairs Medical Center, Wisconsin 53226, USA.

The Journal of Biological Chemistry
|August 29, 2007
PubMed

Insights

p38alpha MAPK regulates Ras transformation and stress response by depleting p38gamma protein. This feed-forward mechanism, involving c-Jun and ubiquitin-proteasome pathways, ensures coordinated p38 MAPK family responses.

Area of Science:

  • Cellular Biology
  • Molecular Signaling
  • Protein Interactions

Background:

  • The p38 MAPK family comprises four isoforms (alpha, beta, gamma, delta) activated by common stimuli.
  • The precise interplay between these isoforms in mediating biological responses remains largely unelucidated.

Purpose of the Study:

  • To investigate the regulatory mechanism of p38alpha on its family member p38gamma.
  • To elucidate the role of this interaction in Ras transformation and cellular stress response.

Main Methods:

  • Analysis of MAPK kinase 6 (MKK6)-p38 fusion proteins to assess isoform activity.
  • Investigating c-Jun phosphorylation and AP-1 regulation.
  • Utilizing ubiquitin-proteasome pathway inhibitors to determine degradation mechanisms.

Main Results:

  • p38alpha phosphorylation inhibits c-Jun, while p38gamma stimulates it, leading to distinct AP-1 activity.
  • p38alpha activation leads to p38gamma depletion via c-Jun-dependent ubiquitin-proteasome pathways.
  • p38alpha-mediated p38gamma downregulation influences Ras transformation and stress-induced cell death.

Conclusions:

  • p38alpha acts as a gatekeeper within the p38 MAPK family upon phosphorylation.
  • A feed-forward mechanism involving p38alpha-mediated p38gamma depletion ensures coordinated cellular responses.
  • This regulation impacts Ras transformation and stress response pathways.

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