Phosphorylation of Cullin3 by the pseudokinase ALDH18A1 disrupts KEAP1-mediated NRF2 degradation.

Abstract

The decline of the transcription factor NRF2 during aging contributes to impaired oxidative stress defense, yet the underlying mechanisms remain incompletely understood. Here we show that ALDH18A1 (P5CS) is downregulated in parallel with NRF2 in the airway epithelial cells of aged mouse lungs. Mechanistically, P5CS directly binds to Cullin3 and promotes its phosphorylation-a previously unrecognized post-translational modification of Cullin3-in a manner dependent on its kinase-like activity. This phosphorylation inhibits Cullin3 neddylation and disrupts its interaction with KEAP1, thereby impairing the ubiquitin ligase activity of the Cullin3-KEAP1 complex and leading to NRF2 stabilization. A kinase-dead mutant (T299I) or pharmacological inhibition of P5CS kinase-like activity abolishes this regulatory effect. Our findings identify Cullin3 phosphorylation as a novel regulatory mechanism controlling NRF2 stability and provide a molecular explanation for the age-related decline of NRF2 downstream of P5CS downregulation.