STING1 Knockout Cell Line (HeLa)

The cyclic guanosine monophosphate (GMP)-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway plays a pivotal role in innate immune responses to viral infection and inhibition of autoimmunity. Recent studies have suggested that micronuclei formed by genotoxic stress can activate innate immune signaling via the cGAS-STING pathway. Here, we investigated cGAS localization, activation, and downstream signaling from micronuclei induced by ionizing radiation, replication stress, and chromosome segregation errors. Although cGAS localized to ruptured micronuclei via binding to self-DNA, we failed to observe cGAS activation; cGAMP production; downstream phosphorylation of STING, TBK1, or IRF3; nuclear accumulation of IRF3; or expression of interferon-stimulated genes. Failure to activate the cGAS-STING pathway was observed across primary and immortalized cell lines, which retained the ability to activate the cGAS-STING pathway in response to dsDNA or modified vaccinia virus infection. We provide evidence that micronuclei formed by genotoxic insults contain histone-bound self-DNA, which we show is inhibitory to cGAS activation in cells.

BACKGROUND AND PURPOSE:Stimulator of interferon response cGAMP interactor 1 (STING), a central hub protein of cyclic GMP-AMP synthase (cGAS)-STING signalling pathway, has a crucial role in regulating type I interferons (IFNs) production and response. Recent studies indicate that excessive activation of STING is strongly associated with autoimmune diseases, including systemic lupus erythematosus (SLE). Searching immunomodulators that negatively regulate STING might greatly contribute to the suppression of autoimmunity. EXPERIMENTAL APPROACH:The peripheral blood mononuclear cells (PBMCs) of SLE patients, Hela cells, L929 cells and bone marrow-derived macrophages (BMDMs) from mice were used as in vitro models. While, Trex1 KO mouse autoimmune disease model was used as in vivo model. After treatment with cordycepin, a nucleoside from Cordyceps mushrooms, type I IFNs production and response were determined by western blotting, real-time polymerase chain reaction (PCR), dual-luciferase assay, enzyme-linked immunosorbent assay (ELISA), haematoxylin-eosin staining and RNA-seq. KEY RESULTS:Cordycepin inhibited type I IFNs production and response in human and murine systems following cGAS-STING signalling activation. Importantly, cordycepin markedly attenuates the autoinflammatory and autoimmune responses in Trex1 KO BMDMs and Trex1 KO mice. Furthermore, cordycepin effectively suppressed the production of type I IFNs and interferon-stimulated genes (ISGs) in the PBMCs of SLE patients. Mechanistically, cordycepin promoted STING degradation via autophagy pathway upon DNA stimulation. CONCLUSION AND IMPLICATIONS:This study shows that cordycepin promotes STING autophagic degradation to alleviate autoimmunity upon DNA stimulation. Cordycepin might be a potential therapeutic candidate for alleviating aberrant type I IFNs in autoimmune and autoinflammatory diseases.