(886) The E3 Ligase RNF11 is a novel regulator of type I Interferon-independent antiviral defenses critical for restricting viral infection in macrophages

Introduction/Rationale: Classically, anti-viral defenses are thought to be driven by the production of pro-inflammatory cytokines and type I interferons (IFNs) triggered by the activation of innate immune sensing pathways such as the DNA sensing pathway cGAS-STING. There are also cell autonomous defense mechanisms, such as xenophagy, that are equally important for restricting viral infections, but these are poorly understood. In this study, we examined a potential role of the E3 ubiquitin ligase RNF11 in regulating cGAS-STING signaling and anti-viral host defense in macrophages.

Methods: We utilized macrophage cell lines including THP-1 and RAW 264.7 to examine the role of RNF11 in cGAS-STING signaling and viral infections in macrophages. Lentiviral vectors expressing control scrambled or RNF11 shRNA were used to knockdown RNF11. We performed western blotting, Incucyte live-cell imaging, qRT-PCR, ELISA, flow cytometry, and confocal microscopy to examine potential roles of RNF11 in cGAS-STING signaling and innate anti-viral responses in macrophages.

Results: Knockdown (KD) of RNF11 elicited more robust activation of the cGAS-STING pathway in response to cGAS and STING agonists and increased type I IFN production in macrophages. Unexpectedly, despite more cGAS-STING activation, there was increased replication of a DNA virus (herpes simplex virus 1 [HSV-1]). Similar results were obtained with a panel of RNA viruses including Sendai virus (SeV) and vesicular stomatitis virus (VSV) and this phenotype was specific to macrophages. Remarkably, the increased viral loads in RNF11 KD macrophages persisted with a blocking antibody specific for interferon alpha/beta receptor 1 (IFNAR1) interferon, suggesting that the anti-viral function of RNF11 is independent of type I IFN signaling.

Conclusion: Overall, our results suggest that RNF11 is an essential component of a novel type I interferon-independent form of cell autonomous defense that is critical for restricting viral infection in macrophages.