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MKP-1 antagonizes C/EBPβ activity and lowers the apoptotic threshold after ischemic injury

A Rininger1, C Dejesus, A Totten

  • 1Department of Pediatrics, University of Rochester Medical Center, NY, USA.

Cell Death and Differentiation
|April 24, 2012
PubMed

Insights

MAPK phosphatase-1 (MKP-1) promotes cell death in the central nervous system by inhibiting the neuroprotective factor C/EBPβ. Targeting this MKP-1 and C/EBPβ interaction may offer therapeutic strategies for ischemic disorders.

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Cell Biology

Background:

  • MAPK phosphatase-1 (MKP-1) regulates MAP kinase signaling and is present in the central nervous system (CNS), but its role in ischemic stress is not fully understood.
  • MKP-1 influences metabolic, inflammatory, and survival pathways, and its induction post-ischemia suggests a critical function in neuronal response.

Purpose of the Study:

  • To investigate the function of MKP-1 in the CNS, particularly its role in neuronal cell death and its interaction with neuroprotective factors.
  • To elucidate the molecular mechanisms by which MKP-1 affects cell survival and death pathways.

Main Methods:

  • In vitro studies assessing MKP-1's effects on cell death factors (BCL2,')} protein 3, caspases 3 and 12) and CCAAT/enhancer-binding protein beta (C/EBPβ).
  • Analysis of C/EBPβ expression and phosphorylation in response to MKP-1.
  • Rescue experiments using enforced C/EBPβ expression.
  • Studies in MKP-1 knockout mice to evaluate MKP-1's role in basal C/EBPβ localization and its response to global forebrain ischemia.

Main Results:

  • MKP-1 induced apoptotic cell death in vitro by activating cell death factors and caspases.
  • MKP-1 inhibited C/EBPβ, reducing its expression and phosphorylation at a key site.
  • Enforced C/EBPβ expression protected cells from MKP-1-induced toxicity.
  • MKP-1 activity was necessary for excluding C/EBPβ from the nucleus and antagonized C/EBPβ expression after ischemia, especially in the hippocampus.
  • MKP-1 lowers the apoptotic threshold by inhibiting C/EBPβ and increasing BH3 protein and caspase activity.

Conclusions:

  • MKP-1 promotes neuronal cell death by inhibiting the neuroprotective transcription factor C/EBPβ.
  • The MKP-1-C/EBPβ axis is a critical regulator of apoptosis in the CNS following ischemic injury.
  • Targeting the MKP-1-C/EBPβ interaction may hold therapeutic potential for ischemic disorders, but inhibiting MKP-1's phosphatase activity alone might be insufficient.

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