ATP6V1G1 Targeting RIG-I Positively Regulates RLR Antiviral Innate Immune Signaling Pathway

The innate immune system is the first line of defense against the invasion of pathogenic microorganism.Host cells sense the invasion of viruses and bacterias through pattern recognition receptors(PRRs)and bind to their pathogen associated molecular patterns(PAMPs)to induce a variety of transcription factors entering the nucleus,including interferon regulatory factors 3/7 and NF-κB,and initiate transcription of type I interferons,inflammatory cytokines,etc.,thereby enabling cells to establish antiviral immune defense mechanisms.RIG-I-like receptors(RLRs)are key sensors for cells to direct innate immunity as the first line of defense against RNA virus infections.Upon recognition of intracytoplasmic viral RNA,activated RIG-I is recruited to the mitochondrion-located adaptor protein VISA(also known as MAVS,CARDIF,and IPS-1).The adaptor protein VISA is further oligomerized,and the activated VISA continues to recruit members of the downstream TRAF family to form the VISA signalsome.On the one hand,TRAFs transmit signals to downstream kinases such as TBK1/IKKε;on the other hand,the signalsome continues to recruit proteins including TANK,TRADD,etc.to amplify the casade.Ultimately,the composed signal protein complex transmits antiviral signals and finally induces the production of type I interferon and the innate antiviral immune response.Although the research on antiviral signal transduction of the RIG-I receptor has gradually increased in recent years,the graphics of its antiviral regulatory mechanism are not complete.In this study,we identified ATP6V1G1 as a positive regulator of the RLRs.First,a number of RIG-I interacting proteins including ATP6V1G1 were obtained through yeast two-hybrid screening and co-immunoprecipitation experiments.Subsequent studies found that overexpression of ATP6V1G1 potentiated virus-triggered activation of IFN-regulatory factor 3(IRF3)and expression of IFNB1,whereas ATP6V1G1 knockdown and deficiency markedly inhibited RNA virus-triggered induction of downstream antiviral genes.We also found that overexpression of ATP6V1G1 enhanced the K63 ubiquitination of RIG-I.Together,these data suggest ATP6V1G1 is an important regulator of the RIG-I-mediated antiviral immune response,thereby highlighting the intricate regulation of innate immune signaling.