VAMP8 contributes to TRIM6-mediated type-I interferon antiviral response during West Nile virus infection

Members of the tripartite motif (TRIM) family of E3 ubiquitin ligases regulate immune pathways including the antiviral type I interferon (IFN-I) system. Previously, we demonstrated that TRIM6 is involved in IFN-I induction and signaling. In absence of TRIM6 function, optimal IFN-I signaling is reduced, allowing increased replication of interferon-sensitive viruses. Despite numerous mechanisms to restrict vertebrate host’s IFN-I response, West Nile Virus (WNV) replication is sensitive to pre-treatment with IFN-I. However, the regulators and products of the IFN-I pathway important in regulating WNV replications are incompletely defined. Consistent with WNV’s sensitivity to IFN-I, we found that in TRIM6 knockout (TRIM6 KO) A549 cells WNV replication is significantly increased. Additionally, induction of Ifnb mRNA was delayed and the expression of several IFN-stimulated genes (ISGs) was reduced in TRIM6 KO cells. IFNβ pre-treatment was more effective in protecting against subsequent WNV infection in wt cells, indicating that TRIM6 contributes to the establishment of an IFN-induced antiviral response against WNV. Using next generation sequencing, we identified potential factors involved in this TRIM6-mediated antiviral response. One identified gene, VAMP8, is a soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) in the vesicle-associated membrane protein subfamily. Knockdown of VAMP8 resulted in reduced STAT1 phosphorylation and impaired induction of several ISGs following WNV infection or IFNβ treatment. Therefore, VAMP8 is a novel gene involved in the regulation of IFN-I signaling, and its expression is dependent on TRIM6 function. Overall, these results indicate that TRIM6 contributes to the antiviral response against WNV by regulating the IFN-I system.