Site-Specific Photo-Cross-Linking Reveals CCT2 as a Regulator of cGAS-STING Signaling via Clearance of cGAS-DNA Condensates.

Cyclic GMP-AMP synthase (cGAS) serves as a cytosolic DNA sensor that detects double-stranded DNA (dsDNA) and responds by producing 2'3'-cyclic GMP-AMP (cGAMP), which in turn initiates downstream signaling events that drive innate immune activation. Tight control of cGAS activity is required to preserve immune balance; however, the molecular factors that fine-tune its activation dynamics and protein stability are not yet fully understood. Here, we employed a residue-resolved photo-cross-linking approach coupled with quantitative proteomics to profile cGAS regulators, which uncovered the chaperonin TRiC subunit CCT2 as a previously unappreciated cGAS-associated factor. Functional analyses demonstrated that CCT2 attenuates cGAS-STING signaling by facilitating autophagy-mediated turnover of DNA-bound cGAS aggregates, thereby limiting the persistence of immunostimulatory cytosolic DNA signals and ensuring appropriate immune responses. Collectively, these findings demonstrate that site-specific protein photo-cross-linking provides a powerful means to interrogate protein-protein interactions and define CCT2 as a key negative modulator of cGAS, with implications for therapeutic modulation of antiviral immunity.