cGAS-IFN-I responses by extracting nuclear DNA from dying cells via nucleocytosis

Self-DNA triggers cGAS-STING-mediated type I interferon (IFN-I) to induce both protective and pathogenic immune responses; however, how self-DNA activates the cytosolic cGAS-STING pathway remains unclear. Here we show that the cGAS/STING/IFN-I axis is activated by self-DNA via a process termed 'nucleocytosis', in which nuclear DNA is extracted from dying cells by macrophages. Mechanistically, lysosomal malfunction, via both proton loss and palmitoyl-protein thioesterase 1 (PPT1) inhibition, triggers cell death and calreticulin accumulation in the nuclei. Live-cell imaging of secretion activity reveals that macrophages access the calreticulin-enriched nuclei of dying cells and extract DNA for cGAS-STING activation. Consistent with these findings, PPT1-targeting cationic amphiphilic drugs induce a cGAS-STING-dependent IFN-I response in vitro and in vivo. Our findings thus identify nucleocytosis as a macrophage function for nuclear DNA extraction and induction of the cGAS/IFN-I axis, and suggest that nucleocytosis-inducing cell death could be a druggable target for treating self-DNA-related inflammatory diseases.