Mechanism Of Palmitoylation In Regulating NLRP3 Inflammasome Activation And Zika Virus Infection

Protein post-translational modification,such as acetylation,ubiquitination,methylation and lipidization,plays an important role in the structure,function and chemical properties of protein.Palmitoylation is a kind of lipidization.The result of palmitoylation is that the palmitate is covalently bound with the active sulfhydryl on the cysteine residue of the protein,which alters the hydrophobicity of target protein and thus regulates the subcellular localization,stability and function of it.Plamitoylation is dynamic and reversible,which is catalyzed by a series of proteases containing Asp-HisHis-Cys(DHHC)motifs,and removed by acylprotein thioesterases.It was reported previously that palmitoylation plays important roles in immune regulation,tumorigenesis,cancer progression and pathogen infection,but its role in NLRP3 inflammasome activation and Zika virus(ZIKV)infection has not been thoroughly reported.NLRP3(NOD-,LRR-and pyrin domain-containing protein 3)is one of the important pattern recognition receptors in the innate immune system,which plays a key role in the resistance to pathogen invasion and the response to endogenous danger signals.Meanwhile,aberrant activity of NLRP3 has been repeatedly shown to be associated with neurodegenerative diseases,autoimmune diseases,metabolic diseases,and cancers.Therefore,it is important to explore the specific mechanisms of NLRP3 activation and regulation.Here,a novel regulatory mechanism for NLRP3 activation is proposed,in which palmitoylation regulates NLRP3 inflammasome activation.Palmitoylation of NLRP3 is identidfied during its activation,which occurs on Cys419 of NLRP3.At the cellular level,the palmitoylation inhibitor,2-bromopalmitate(2-BP)treatment or mutation in Cys419 can effectively block NLRP3 palmitoylation and activation,suggesting that NLPR3 palmitoylation is essential for its activation.In addition,ZDHHC17 is identified as the predominant enzyme that mediates the initiation of NLRP3 palmitoylation and promotes the activation of NLRP3 inflammasome.In mechanism,ZDHHC17 dirtectly interacts with NLRP3 to mediate NLRP3 palmitoylation and helps to recruit NEK7,thus licensing inflammasome activation.These findings enrich the regulatory mechanisms of NLRP3 inflammasome activation and provide potential targets for the treatment of NLRP3-mediated inflammatory diseases.ZIKV is a mosquito-borne Flavivirus.It is reported that ZIKV infection would cause severe central nervous system diseases,including Guillain-Barre syndrome and microcephaly in newborns,as well as possible male sterility.So far,there is no vaccine or effective drug to treat ZIKV infection.Therefore,studying the mechanism of ZIKV infection and replication can provide more theoretical basis for drug development against ZIKV.Here,we explored the effect of palmitoylation on ZIKV infection.We found that2-BP treatment can effectively promote ZIKV infection in Vero cells,suggesting that the occurrence of palmitoylation may be not conducive to viral infection.The structure protein Envelope of ZIKV was identified to be palmitoylated,which occurred on Cys308.Further studies showed that ZDHHC11 mediated the palmitoylation of Envelope protein through interacting with Envelope protein.More importantly,ZDHHC11 effectively inhibited ZIKV infection in U251 cells with an enzyme-dependent manner,probably by mediating Envelope palmitoylation to inhibit viral infection.These results enrich the mechanism of host regulation of ZIKV infection and provide a theoretical basis for ZIKV treatment and drug development.