Stimulator of interferon genes (STING) provides insect antiviral immunity by promoting Dredd caspase-mediated NF-κB activation.

The antiviral cGMP-AMP (cGAMP)-imulator of terferon enes (STING) pathway is well characterized in mammalian cells. However， whether this pathway also plays a role in insect antiviral immunity is unknown. In this study， we found that cGAMP is produced in silkworm () cells infected with nucleopolyhedrovirus (NPV). In searches for STING-related sequences， we identified ， a potential cGAMP sensor in We observed that overexpression effectively inhibits NPV replication in silkworm larvae， whereas dsRNA-mediated knockdown resulted in higher viral load. Cleavage and nuclear translocation of BmRelish， a NF-κB-related transcription factor， was also observed when BmSTING was overexpressed and was enhanced by cGAMP stimulation or viral infection of larvae. Moreover， we identified a caspase-8-like protein (BmCasp8L) as a BmSTING-interacting molecule and as a suppressor of BmSTING-mediated BmRelish activation. Interestingly， cGAMP stimulation decreased BmCasp8L binding to BmSTING and increased BmRelish activity. Of note， an interaction between death-related ced-3/Nedd2-like caspase (BmDredd) and BmSTING promoted BmRelish cleavage for efficient antiviral signaling and protection of insect cells from viral infection. Our findings have uncovered BmSTING as a critical mediator of antiviral immunity in the model insect and have identified several BmSTING-interacting proteins that control antiviral defenses.