USP14 Suppresses RIG-I-Mediated Antiviral Innate Response By Deubiquitinating K63-Linked RIG-I

Innate immune system is the first defense that protects the host from infection by pathogenic organisms.Recognition of viral components by pattern-recognition receptors(PRRs)and initiation of related signaling pathways are crucial for host to restrain viral infection and propagation.One of the RIG-I-like receptors(RLRs)is RIG-I,which is the most important receptor recognized by RNA virus.RIG-I could be activated by single strand RNA virus,double strand RNA virus and RNAs with 5'-pp and 5'-ppp end.Ubiquitin modification is one of the most important protein post-translation modification and exists in almost all of the cell activities,and is indispensable in innate immune response.Ubiquitin types include K6,K11,K27,K29,K48 and K63.We know more about K48 and K63 ubiquitin modifications.K63 ubiquitin modification is related with activation of substrates and induction of signaling pathways.For example,when triggered by RNA virus,RIG-I would undergo K63 ubiquitin modification and be activated,finally promoting transduction of downstream signal.Ubiquitin modification could be reversed by deubiquitinase enzymes(DUBs).By co-immunoprecipitation and mass-spectrum analysis,our group had ever screened the DUBs interacting with RIG-I in stable overexpression of RIG-I in HEK293T cells infected with VSV.We found USP14 could interact with RIG-I.It implied that USP14 might regulate RIG-I-mediated innate immune response.In present study,we examined what and how USP14 regulated cellular antiviral responses.In mouse peritoneal macrophage and THP1 cells,knockdown of UPS 14 significantly elevated RIG-I mediated type ? IFN,IL-6 and TNF-? production,inhibited VSV replication as well.Cells pretreated with IU1 also enhanced RNA virus induced type ? IFN,IL-6 and TNF-?production and reduced VSV titers.Overexpression of USP14 in HeLa cells inhibited IFN-? production and promoted VSV replication.Dual-luciferase reporter assay,immunoprecipitation and immunoblot together showed that USP14 interacted with RIG-I and removed K63-linked ubiquitin from RIG-I.VSV infection elevated Akt phosphorylation in mouse peritoneal macrophage and phosphorylated Akt promoted USP14 phosphorylation and activation.Furthermore,we discovered that USP14 negatively regulated RIG-I-mediated NF-?B activation.In present study,we find out the mechanisms that USP14 negatively regulates cellular antiviral response.These findings provide insights into a potential new therapy specifically targeting USP14 for RNA virus related diseases.