Organelle membrane-associated proteins recruit cGAS via phase separation to facilitate its membrane localization

Abstract Double-stranded DNA is recognized as a danger signal by cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS), triggering innate immune responses in mammals. As a DNA sensor, cGAS is generally believed to distribute in the cytoplasm, whereas alternative subcellular localization of cGAS, including cytoplasmic membrane and nucleus, is important to regulate its activity. However, it remains obscure whether cGAS could localized to organelle membrane and the mechanism has yet to be uncovered. Our study reveals that cGAS could localize to the endoplasmic reticulum, Golgi apparatus, and endosomes upon DNA challenge. We identified that the post-translational modification enzymes ZDHHC18 and MARCH8, through their intrinsically disordered regions (IDRs), facilitate the binding of cGAS to the Golgi and endosome, respectively. These IDRs phase separated to recruit cGAS and double-stranded DNA (dsDNA) into biomolecular condensates, suppressing cGAS activity and downstream signaling pathways. These findings highlight the regulatory mechanisms of cGAS activity through the spatial organization, providing new insights into the modulation of innate immune responses.