Figure 3.

Role of superoxide dismutases (SODs) in the regulation of redox homeostasis and cell signaling. In addition to the classical function of SODs [i.e. to dismutate superoxide ion into hydrogen peroxide (H₂O₂)], SODs are increasingly recognized to regulate diverse cellular processes from mitogenic signaling to oxidative stress response. The H₂O₂ product in turn can activate receptor tyrosine kinase (RTK) signaling. SOD1 also acts as a transcription factor regulating oxidative stress response. When H₂O₂ reaches an excessive level, it activates the checkpoint kinase ataxia-telangiectasia mutated (ATM) kinase, which promotes SOD1 phosphorylation by Cds/Dun1 kinase and SOD1 localization into the nucleus where SOD1 acts as a transcription factor for a large panel of genes involved in oxidative stress responses.