A Cytosolic Sensor, DDX41, Binds Double Stranded-DNA and Triggers the Activation of an Innate Antiviral Response in the Shrimp via the STING-Dependent Signaling Pathway.

Helicase DDX41 is a cytosolic sensor capable of detecting double-stranded DNA in mammals. However, the function of DDX41 remains poorly understood in invertebrates. In a previous study, we identified the first DDX41 sensor in the black tiger shrimp (DDX41) and showed that it played a role in anti-viral response. In the present study, we demonstrated that was localized in the cytoplasm of shrimp hemocytes. However, was localized in both the cytoplasm and nucleus of hemocytes in the presence of white spot syndrome virus (WSSV) infection or when stimulated by the nucleic acid mimics, poly(dA:dT) and poly(I:C). Similar results were observed when DDX41 was transfected into human embryonic kidney 293T (HEK293T) cells. Immunoprecipitation further demonstrated that DDX41 bound to biotin-labeled poly(dA:dT) but not poly(I:C). The overexpression of shrimp DDX41 and mouse stimulator of interferon gene (STING) in HEK293T cells synergistically promoted IFN-β and NF-κB promoter activity via the DEADc domain. Co-immunoprecipitation (Co-IP) also confirmed that there was an interaction between DDX41 and STING after stimulation with poly(dA:dT) but not poly(I:C). Our study is the first to demonstrate that DDX41 acts as a cytosolic DNA sensor that interacts with STING via its DEADc domain to trigger the IFN-β and NF-κB signaling pathways, thus activating antiviral innate immune responses.