Roles of innate immune regulator TAPE in RIG-I signaling and antiviral defenses

Abstract

Pattern-recognition receptors detect pathogen-associated molecular patterns to trigger downstream pathways leading to type I IFN and inflammatory cytokines production to defend pathogen infection. RIG-I-like receptors (RLRs) are key cytosolic sensors for recognizing viral RNA to trigger antiviral immunity. The underlying mechanisms linking RLR-mediated viral recognition to antiviral immunity remain to be further explored. Through our previous work, we uncovered an innate immune regulator termed TAPE (TBK1-Associated Protein in Endolysosomes), also known as CC2D1A, which is implicated in the viral RNA senor TLR3 and RLR pathways. Yet, the in vivo role of TAPE in antiviral defenses and the mechanistic mechanisms of how TAPE regulates cytosolic RIG-I signaling still remain to be established. TAPE conditional knockout mice were generated for our study. Results from in vivo studies showed that TAPEf/f CD11c-Cre mice exhibited a more severe mortality than WT mice upon influenza A virus (IAV) infection. Ex vivo studies also showed that TAPE-deficient mouse embryonic fibroblasts and macrophages were defective in type-I interferon induction upon RLR ligand stimulation. In addition, our biochemical analyses showed that the N-terminal region of TAPE was critical for interacting with the CARD domain of RIG-I while the C-terminal region of TAPE contributed most to the interaction with MAVS/IPS-1, a RLR downstream mediator. Together, our results suggest a crucial role for TAPE in linking RIG-I to type I IFN-mediated antiviral responses. Future work will further determine the in vivo role of TAPE in IAV and other RNA virus infection, and explore the mechanistic mechanisms of how TAPE regulates RIG-I signaling.