Dissociation of eIF4E-binding protein 2 (4E-BP2) from eIF4E independent of Thr37/Thr46 phosphorylation in the ischemic stress response

PLoS One. 2015 Mar 30;10(3):e0121958. doi: 10.1371/journal.pone.0121958. eCollection 2015.

Abstract

Eukaryotic initiation factor (eIF) 4E-binding proteins (4E-BPs) are translational repressors that bind specifically to eIF4E and are critical in the control of protein translation. 4E-BP2 is the predominant 4E-BP expressed in the brain, but their role is not well known. Here, we characterized four forms of 4E-BP2 detected by two-dimensional gel electrophoresis (2-DGE) in brain. The form with highest electrophoretic mobility was the main form susceptible to phosphorylation at Thr37/Thr46 sites, phosphorylation that was detected in acidic spots. Cerebral ischemia and subsequent reperfusion induced dephosphorylation and phosphorylation of 4E-BP2 at Thr37/Thr46, respectively. The induced phosphorylation was in parallel with the release of 4E-BP2 from eIF4E, although two of the phosphorylated 4E-BP2 forms were bound to eIF4E. Upon long-term reperfusion, there was a decrease in the binding of 4E-BP2 to eIF4E in cerebral cortex, demonstrated by cap binding assays and 4E-BP2-immunoprecipitation experiments. The release of 4E-BP2 from eIF4E was without changes in 4E-BP2 phosphorylation or other post-translational modification recognized by 2-DGE. These findings demonstrated specific changes in 4E-BP2/eIF4E association dependent and independent of 4E-BP2 phosphorylation. The last result supports the notion that phosphorylation may not be the uniquely regulation for the binding of 4E-BP2 to eIF4E under ischemic stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain Ischemia / metabolism*
  • CA1 Region, Hippocampal / metabolism
  • Cerebral Cortex / metabolism
  • Disease Models, Animal
  • Electrophoresis, Gel, Two-Dimensional
  • Eukaryotic Initiation Factor-4E / metabolism*
  • Eukaryotic Initiation Factors / chemistry
  • Eukaryotic Initiation Factors / metabolism*
  • Male
  • Oxidative Stress
  • Phosphorylation
  • Protein Binding
  • Rats
  • Rats, Wistar
  • Reperfusion Injury / metabolism
  • Threonine / chemistry

Substances

  • EIF4EBP2 protein, rat
  • Eukaryotic Initiation Factor-4E
  • Eukaryotic Initiation Factors
  • Threonine

Grants and funding

This work was supported by the Institute of Health Carlos III (http://www.isciii.es/) from the Spanish Ministry of Economy and Competitiveness with the grant numbers PI11/00334 (National Plan) and PI14/00705 (State Plan), and the funding from FEDER grants. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.