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Hyperoxia alters the expression and phosphorylation of multiple factors regulating translation initiation

Jeffrey S Shenberger1, Jennifer L Myers, Stephen G Zimmer

  • 1Department of Pediatrics, Dartmouth Medical School, Hanover, New Hampshire, USA. jeffrey.s.shenberger@dartmouth.edu

American Journal of Physiology. Lung Cellular and Molecular Physiology
|November 16, 2004
PubMed

Insights

High oxygen levels (hyperoxia) harm cells by reducing protein synthesis. This study shows hyperoxia increases eIF4E phosphorylation and 4E-BP1 binding, inhibiting translation initiation in human lung fibroblasts.

Area of Science:

  • Cellular and Molecular Biology
  • Biochemistry
  • Physiology

Background:

  • Hyperoxia, or high oxygen levels, is known to be cytotoxic.
  • It impairs cellular metabolic functions, notably protein synthesis.
  • Translational control, primarily during initiation, is a key regulatory point.

Purpose of the Study:

  • To investigate the mechanisms by which hyperoxia affects protein synthesis in human lung fibroblasts.
  • To examine the roles of eukaryotic initiation factor 4E (eIF4E) and 4E-binding proteins (4E-BP) in hyperoxia-induced translational inhibition.
  • To assess the impact of hyperoxia on the eIF2alpha pathway.

Main Methods:

  • Exposure of human lung fibroblasts to 95% O2.
  • Measurement of thymidine and leucine incorporation to assess DNA and protein synthesis.
  • Analysis of protein phosphorylation, expression, and binding interactions (eIF4E, 4E-BP1, eIF2alpha).

Main Results:

  • Hyperoxia decreased DNA and protein synthesis.
  • Increased phosphorylation of eIF4E and decreased phosphorylation of 4E-BP1 were observed.
  • Hyperoxia led to increased eIF4E expression and enhanced eIF4E-4E-BP1 association.
  • Phosphorylation of eIF2alpha increased at later time points without stress granule formation.

Conclusions:

  • Hyperoxia diminishes protein synthesis in lung fibroblasts.
  • This inhibition is mediated by increased eIF4E phosphorylation and enhanced binding affinity of 4E-BP1 for eIF4E.
  • The eIF2alpha pathway is also affected, but distinct from the primary eIF4E-mediated mechanism.

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