Inhibition of STING-mediated antiviral innate immunity activation by CD97 via modulation of ER-phagy.

Endoplasmic reticulum (ER) autophagy (ER-phagy) is a vital homeostatic process triggered by multiple signals and plays a crucial role in regulating innate immunity and viral replication. However, the mechanisms by which host proteins utilize ER-phagy to regulate innate immune response during viral infection remains largely unclear. Here, we uncover the regulatory crosstalk between innate immune adapter, ER retention protein Stimulator of Interferon Genes (STING), and the G protein-coupled receptor ADGRE5/CD97 (Cluster of Differentiation 97). Our results demonstrate that CD97 suppresses the STING-mediated type-I interferon (IFN-I) response against DNA virus and cytosolic DNA, thereby promoting herpes simplex virus type 1 (HSV-1) replication in both cells and mice. CD97 facilitates the recruitment of the ER-phagy receptor, FAM134B (family with sequence similarity 134, member B), to initiate ER-phagy, resulting in the degradation of STING subsequent to DNA virus infection. Furthermore, Cd97-deficient mice exhibit higher IFN-I response and greater resistance to HSV-1 infection. Additionally, our findings reveal that inhibiting CD97 with sanguinarine effectively disrupts HSV-1 replication. These findings shed light on the role of CD97 in the innate immune response against DNA virus infections and offer valuable checkpoint for anti-viral STING activation.