Cullin-3 adaptor SHKBP1 inhibits SQSTM1/p62 oligomerization and Keap1 sequestration

SQSTM1/p62 is a master regulator of the autophagic and ubiquitination pathways of protein degradation and the antioxidant response. p62 functions in these pathways via reversible assembly and sequestration of additional factors into cytoplasmic phase-separated structures termed p62 bodies. The physiological roles of p62 in these various pathways depend on numerous mechanisms for regulating p62 body formation and dynamics that are incompletely understood. Here, we identify a new mechanism for regulation of p62 oligomerization and incorporation into p62 bodies by SHKBP1, a cullin-3 E3 ubiquitin ligase adaptor, that is independent of its potential functions in ubiquitination. We map an SHKBP1-p62 protein-protein interaction outside of p62 bodies that limits p62 assembly into p62 bodies and affects the antioxidant response involving sequestration of Keap1 and nuclear translocation of Nrf2. These studies provide a non-ubiquitination-based mechanism for an E3 ligase adaptor in regulating p62 body formation and cellular responses to oxidative stress.