Nuclear Transport: A Switch for the Oxidative Stress—Signaling Circuit?

Figure 4

Mild and severe oxidative stress have different effects on nuclear transport factors. The effects of mild (2 mM DEM) and severe oxidative stress (10 mM H₂O₂) on the subcellular distribution of importin-α1, Ran, and HuR were analyzed in HeLa cells. Proteins were located by indirect immunofluorescence [39, 69, 79]. DEM treatment accumulated importin-α1 in nuclei but did not drastically affect the distribution of Ran. By contrast, severe oxidative stress induced by H₂O₂ caused a pronounced nuclear accumulation of importin-α1 and collapsed the nucleocytoplasmic Ran gradient. Both treatments relocated HuR to the cytoplasm. However, DEM triggered the assembly of HuR-containing SGs, which were rare or absent upon incubation with H₂O₂.