Forkhead transcription factor FOXO3a protects quiescent cells from oxidative stress

Area of Science:

• Cellular biology
• Molecular mechanisms of cell death
• Oxidative stress and aging

Background:

• Reactive oxygen species (ROS) are crucial for cell proliferation but can trigger apoptosis.
• Protein kinase B (PKB) activation protects proliferating cells from ROS-induced apoptosis.
• Mechanisms protecting quiescent cells lacking PKB activity from ROS-induced apoptosis remain unclear.

Purpose of the Study:

• To investigate how quiescent cells, lacking PKB activity, are protected against cell death induced by reactive oxygen species.
• To elucidate the role of the Forkhead transcription factor FOXO3a in cellular protection against oxidative stress in quiescent cells.

Main Methods:

• Investigated the role of FOXO3a in quiescent cells under oxidative stress conditions.
• Assessed the impact of FOXO3a on manganese superoxide dismutase (MnSOD) mRNA and protein levels.
• Examined the relationship between PKB inactivity, FOXO3a activation, and MnSOD expression.

Main Results:

• FOXO3a directly increases manganese superoxide dismutase (MnSOD) mRNA and protein in quiescent cells, enhancing resistance to oxidative stress.
• This FOXO3a-mediated MnSOD upregulation counteracts apoptosis induced by glucose deprivation.
• PKB inactivity in quiescent cells triggers Forkhead transcription factor activation, leading to MnSOD transcriptional activation and ROS reduction.

Conclusions:

• FOXO3a-mediated MnSOD upregulation is a key protective mechanism against oxidative stress in quiescent mammalian cells, independent of PKB signaling.
• This alternative pathway highlights the adaptability of cellular defense mechanisms against ROS.
• The findings suggest that Forkhead transcription factors play a conserved role in regulating oxidative stress resistance and potentially longevity across species, extending from C. elegans to mammals.