Phosphorylation of phase‐separated p62 bodies by ULK1 activates a redox‐independent stress response

Abstract

NRF2 is a transcription factor responsible for antioxidant stress responses that is usually regulated in a redox‐dependent manner. p62 bodies formed by liquid–liquid phase separation contain Ser349‐phosphorylated p62, which participates in the redox‐independent activation of NRF2. However, the regulatory mechanism and physiological significance of p62 phosphorylation remain unclear. Here, we identify ULK1 as a kinase responsible for the phosphorylation of p62. ULK1 colocalizes with p62 bodies, directly interacting with p62. ULK1‐dependent phosphorylation of p62 allows KEAP1 to be retained within p62 bodies, thus activating NRF2. p62 S351E/+ mice are phosphomimetic knock‐in mice in which Ser351, corresponding to human Ser349, is replaced by Glu. These mice, but not their phosphodefective p62 S351A/S351A counterparts, exhibit NRF2 hyperactivation and growth retardation. This retardation is caused by malnutrition and dehydration due to obstruction of the esophagus and forestomach secondary to hyperkeratosis, a phenotype also observed in systemic Keap1 ‐knockout mice. Our results expand our understanding of the physiological importance of the redox‐independent NRF2 activation pathway and provide new insights into the role of phase separation in this process. image NRF2 is a master transcription factor for antioxidant stress that is usually regulated by redox states of KEAP1. This study shows that when ULK1 phosphorylates phase‐separated p62 bodies, they bind KEAP1, leading to NRF2‐activation in a redox‐independent manner. ULK1 phosphorylates p62 bodies formed by liquid–liquid phase separation. KEAP1 is retained into these phosphorylated p62 bodies, leading to NRF2 activation. Persistent activation of NRF2 by the redox‐independent pathway causes hyperkeratosis in vivo . The resulting esophageal and forestomach obstruction causes severe growth retardation due to malnutrition.