Stress heals

IKKα regulates human keratinocyte migration through surveillance of the redox environment

Although the functions of H₂O₂ in epidermal wound repair are conserved throughout evolution, the underlying signaling mechanisms are largely unknown. In this study we used human keratinocytes (HEK001) to investigate H₂O₂-dependent wound repair mechanisms. Scratch wounding led to H₂O₂ production in two or three cell layers at the wound margin within ∼30 min and subsequent cysteine modification of proteins via sulfenylation. Intriguingly, exogenous H₂O₂ treatment resulted in preferential sulfenylation of keratinocytes that adopted a migratory phenotype and detached from neighboring cells, suggesting that one of the primary functions of H₂O₂ is to stimulate signaling factors involved in cell migration. Based on previous findings that revealed epidermal growth factor receptor (EGFR) involvement in H₂O₂-dependent cell migration, we analyzed oxidation of a candidate upstream target, the inhibitor of κB kinase α (IKKα; encoded by CHUK), as a mechanism of action. We show that IKKα is sulfenylated at a conserved cysteine residue in the kinase domain, which correlates with de-repression of EGF promoter activity and increased EGF expression. Thus, this indicates that IKKα promotes migration through dynamic interactions with the EGF promoter depending on the redox state within cells.

Summary: This study provides a newly identified mechanism by which H₂O₂-dependent oxidation of the inhibitor of κB kinase α and de-repression of epidermal growth factor promoter activity stimulates keratinocyte migration.