Transformation of autophagic SQSTM1 droplets to SQSTM1-dependent P-bodies.

ABSTRACT

SQSTM1/p62 droplets play crucial roles in droplets-based macroautophagy/autophagy including selective autophagy and bulk autophagy. We observed that under several stress milieus, SQSTM1 droplets entirely colocalize with P-body markers, and these stress-induced SQSTM1 droplets contain mRNAs. We thus determined that under certain stress conditions, autophagic SQSTM1 droplets are converted to a type of enlarged P-bodies, designated SQSTM1/p62-dependent P-bodies (pd-PBs). Stress-enhanced SQSTM1 droplet formation drives the nucleation of pd-PBs through the interaction between SQSTM1 and the RNA-binding protein DDX6. Furthermore, pd-PBs sequester PYCARD, facilitating the assembly of NLRP3 inflammasomes, and in turn induce inflammation-related cytotoxicity. Our study suggests that under stress settings, autophagic SQSTM1 droplets are transformed to pd-PBs, underlining a critical role of SQSTM1 in P-body condensation.