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p38γ Mitogen-activated protein kinase signals through phosphorylating its phosphatase PTPH1 in regulating ras protein

Songwang Hou1, Padmanaban S Suresh, Xiaomei Qi

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

The Journal of Biological Chemistry
|June 26, 2012
PubMed

Insights

Mitogen-activated protein kinase (MAPK) p38γ phosphorylates its substrate, protein-tyrosine phosphatase H1 (PTPH1), revealing a novel mechanism for regulating oncogenesis and cellular stress responses.

Area of Science:

  • Cellular Biology
  • Molecular Oncology
  • Signal Transduction

Background:

  • Protein kinases and phosphatases are key regulators of cellular processes.
  • Protein-tyrosine phosphatase H1 (PTPH1) deactivates p38γ mitogen-activated protein kinase (MAPK).
  • The reciprocal regulation between kinases and phosphatases is not fully understood.

Purpose of the Study:

  • To investigate whether p38γ MAPK can phosphorylate its substrate, PTPH1.
  • To elucidate the role of this phosphorylation in oncogenic activity and stress response.
  • To uncover a novel signaling pathway involving MAPK-phosphatase interaction.

Main Methods:

  • Unbiased proteomic analysis to identify PTPH1 as a p38γ substrate.
  • In vitro and in vivo experiments to confirm phosphorylation at Ser-459.
  • Genetic and pharmacological analyses to assess the role of Ras signaling.
  • Physiological stimuli to study stress response pathways.

Main Results:

  • PTPH1 is identified as a direct substrate of p38γ MAPK, with phosphorylation occurring at Ser-459.
  • Ser-459 phosphorylation is regulated by Ras signaling and is crucial for the oncogenic activity of Ras, p38γ, and PTPH1.
  • A novel stress response pathway involving p38γ-mediated phosphorylation of PTPH1 regulates cell growth and death.
  • This pathway functions independently of canonical MAPK activities but is dependent on cellular environments.

Conclusions:

  • p38γ MAPK directly phosphorylates its substrate PTPH1 at Ser-459, establishing a feedback loop.
  • This phosphorylation event is a critical mechanism for regulating Ras-driven oncogenesis and cellular stress responses.
  • The findings reveal a new signaling paradigm where a MAPK modulates oncogenesis and stress by directly phosphorylating its phosphatase.

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