Z-DNA binding protein 1 (ZBP1) is an innate sensor of Influenza vRNPs and activates programmed cell death and assembly of NLRP3 inflammasome

Abstract

Abstract Influenza A virus (IAV) infection triggers pulmonary epithelial cell death and inflammation which promote bronchioalveolar tissue damage and failure of lung function. However, the mechanism of IAV induced cell death and inflammation remains unclear. RIP homotypic interaction motif (RHIM) has evolved to play critical role in cell death and inflammation. Z-DNA binding protein 1 (ZBP1/DAI) is unique among RHIM-containing proteins since it has additional Za nucleic acid binding domains. Although ZBP1 domain architecture suggests its function as nucleic acid sensor, its precise physiological role is not established. We discovered that ZBP1 is a central activator of IAV induced programmed cell death and NLRP3 inflammasome activation in both immune and non-immune cells. Mechanistically, ZBP1 senses ribonucleoprotein complexes (vRNPs) of IAV and engage RIPK3-caspase-8 dependent apoptosis, necroptosis and NLRP3 inflammasome assembly. ZBP1 also drives RIPK1 dependent secretion of TNF and IL-6 cytokines after IAV infection. We also discovered that apical activation of RIG-I/MAVS/IFNAR signaling licenses ZBP1 upregulation and activation. In contrast to other RNA viruses, IAV replicates inside the nucleus. Accordingly, we observed localization of ZBP1 in the nucleus suggesting its role in sensing IAV inside the nucleus. Strikingly, we also found that ZBP1 undergoes ubiquitination in response to IAV infection to assemble cell death signaling complexes. In IAV infected mice, ZBP1 induces cell death in lung epithelial cells and its absence conferred better survival advantage, despite high viral titers in the lung. Overall, our work demonstrates the central role of ZBP1 in sensing IAV infection to trigger cell death and inflammation.