Oxidant-induced hypertrophy of A549 cells is accompanied by alterations in eukaryotic translation initiation factor 4E and 4E-binding protein-1.
Control of protein synthesis resides at the level of eukaryotic translation initiation (eIF) complex formation. Complex formation is regulated by the mRNA cap-binding protein, eIF4E, whose activity is influenced by phosphorylation and binding to 4E-binding protein 1 (4E-BP1). To provide a link between alterations in protein synthesis and the pathogenesis of oxidant-mediated lung disease, we investigated the effect of hydrogen peroxide (H2O2) on actively growing A549 cells. Cells were exposed to 200 or 400 microM H2O2 for 4 h and then assessed for changes in proliferation, protein synthesis, and eIF4E and 4E-BP1 status over 72 h. We found that both concentrations of H2O2 inhibited [3H]thymidine incorporation and cell division while inducing a G2/M-predominant growth arrest within 24 h. In addition, H2O2 increased cell size, [3H]leucine incorporation/cell, and total cell protein. Although time had little effect on eIF4E and 4E-BP1 expression and phosphorylation state of control cells, H2O2 induced a 2- to 3-fold increase in eIF4E and 4E-BP1 expression, a 5-fold increase in eIF4E phosphorylation, and a shift in the distribution of 4E-BP1 phosphorylation favoring lesser phosphorylated forms. These findings suggest that oxidant-mediated alterations in protein synthesis and cell morphology occur in concert with changes in factors known to regulate translation kinetics.
Shenberger
Jeffrey S
JS
Department of Pediatrics, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03756, USA. Jeffrey.S.Shenberger@Dartmouth.edu
Adams
Mary H
MH
Zimmer
Stephen G
SG
D048868:Adaptor Proteins, Signal Transducing; D000230:Adenocarcinoma; D014408:Biomarkers, Tumor / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins; D048429:Cell Size / Q000187:drug effects; D039561:Eukaryotic Initiation Factor-4E; D005434:Flow Cytometry; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D006984:Hypertrophy / Q000378:metabolism*; D008175:Lung Neoplasms; D016877:Oxidants / Q000494:pharmacology*; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured
D048868:Adaptor Proteins, Signal Transducing; D014408:Biomarkers, Tumor; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D039561:Eukaryotic Initiation Factor-4E; D016877:Oxidants; D010448:Peptide Initiation Factors; D010750:Phosphoproteins; D011506:Proteins; D012097:Repressor Proteins; D006861:Hydrogen Peroxide