LAUSR

Stimulator of interferon genes (STING) is a pivotal innate immune adaptor, and its functions during DNA virus infections have been extensively documented. However, its homeostatic regulation is not well understood. Our study demonstrates that Unc‐93 homolog B1 (UNC93B1) is a crucial checker for STING to prevent hyperactivation. Ectopic expression of UNC93B1 attenuates IFN‐β promoter activity and the transcriptions of IFN‐β, ISG54, and ISG56 genes. Moreover, UNC93B1 also blocks the IRF3 nuclear translocation induced by ectopic expression of both cyclic GMP‐AMP synthase (cGAS) and STING and reduces the stability of STING by facilitating its autophagy–lysosome degradation, which can be reversed by lysosome inhibitors. Mechanistically, UNC93B1 interacts with STING and suppresses STING‐activated downstream signaling by delivering STING to the lysosomes for degradation, depending on its trafficking capability. UNC93B1 knockout in human embryonic kidney 293T cells facilitates IFN‐β promoter activity, IFN‐β, ISG54, and ISG56 transcriptions, and IRF3 nuclear translocation induced by ectopic expression of cGAS and STING. Infected with herpes simplex virus‐1 (HSV‐1), UNC93B1 knockdown BJ cells or primary peritoneal macrophages from Unc93b1‐deficient (Unc93b1−/−) mice show enhanced IFN‐β, ISG54, and ISG56 transcriptions, TBK1 phosphorylation, and reduced STING degradation and viral replication. In addition, Unc93b1−/− mice exhibit higher IFN‐β, ISG54, and ISG56 transcriptions and lower mortality upon HSV‐1 infection in vivo. Collectively, these findings demonstrate that UNC93B1 attenuates the cGAS–STING signaling pathway by targeting STING for autophagy–lysosome degradation and provide novel insights into the function of UNC93B1 in antiviral innate immunity.