IFI207 promotes antiviral responses by modulating STING ubiquitination and degradation

Aim2-like receptors (ALRs) play crucial roles in innate immune signaling pathways and demonstrate strong positive selection likely driven by pathogens. IFI207, an ALR found in all Mus species, enhances interaction with and stabilization of STING, contributing to the control of murine leukemia virus (MLV) infection. We show here that IFI207 enhances the type 1 interferon response by inhibiting activation-induced K63-linked ubiquitination of STING, thereby preventing its recognition by hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), a key component of the ESCRT complex, and its subsequent degradation in lysosomes. IFI207 promotes downstream signaling in the STING pathway in multiple cell types and moreover enhances the STING-dependent response to herpes simplex virus 1 infection ex vivo and in vivo. We also show that IFI207 likely functions in dendritic cells to suppress MLV infection. Our study reveals that IFI207 acts as a modulator in the STING pathway, strengthening the host's defense against viral infections and suggesting that the expansion of the Alr locus in mice may have occurred in response to endemic viruses.

The innate immune system serves as a first line of defense by utilizing a variety of pattern recognition receptors (PRRs) that detect various nucleic acids generated during virus infection, many of which activate the STING pathway, leading to interferon production. One family of PRRs, the Aim2-like receptors (ALRs), is thought to contribute to innate immunity by this mechanism. However, the Alr locus is highly polymorphic at the sequence and copy number level. We found that at least one member in mice, IFI207, contributes to innate immunity by preventing the degradation of STING that normally occurs after its activation, defining a novel mechanism for sustaining immune response. Several ALRs have been implicated in adipogenesis, autoimmune disease, and inflammation, and identification of the pressures that shaped the genes in the locus is thus important for understanding the biological processes in which the ALRs function.