title: Dissociation of eIF4E-binding protein 2 (4E-BP2) from eIF4E independent of Thr37/Thr46 phosphorylation in the ischemic stress response.
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.
authors.affiliation: Department of Investigation, Hospital Ramón y Cajal, IRYCIS, Madrid, Spain.
authors.forename: María I
authors.initials: MI
authors.lastname: Ayuso
authors.affiliation: Department of Investigation, Hospital Ramón y Cajal, IRYCIS, Madrid, Spain.
authors.forename: Emma
authors.initials: E
authors.lastname: Martinez-Alonso
authors.affiliation: Department of Investigation, Hospital Ramón y Cajal, IRYCIS, Madrid, Spain.
authors.forename: Nelida
authors.initials: N
authors.lastname: Salvador
authors.affiliation: Institute of Neurobiology, Slovak Academy of Sciences, Košice, Slovakia.
authors.forename: Petra
authors.initials: P
authors.lastname: Bonova
authors.affiliation: Department of Neurophysiology, Hospital Ramón y Cajal, IRYCIS, Madrid, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Regidor
authors.affiliation: Department of Investigation, Hospital Ramón y Cajal, IRYCIS, Madrid, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Alcázar
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D056547:CA1 Region, Hippocampal / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D004195:Disease Models, Animal; D015180:Electrophoresis, Gel, Two-Dimensional; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism*; D039642:Eukaryotic Initiation Factors / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D018384:Oxidative Stress; D010766:Phosphorylation; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000378:metabolism; D013912:Threonine / Q000737:chemistry
chemical_list: C583882:EIF4EBP2 protein, rat; D039561:Eukaryotic Initiation Factor-4E; D039642:Eukaryotic Initiation Factors; D013912:Threonine
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