The Function And Molecular Mechanism Of Zinc Finger Antiviral Protein ZAP In NLRP3 Inflammasome Activation

NLRP3(nucleotide-binding domain(NOD)-like receptor prtein3)is a vital component of NLRP3 inflammasome,and one of members of the NLRs family.NLRP3 inflammasome is the most widely and deeply studied inflammasome,and its abnormal activation can cause a variety of diseases,such as cancer,Cardiovascular disease and neurodegenerative disease.Therefore,precise regulation of NLRP3 inflammasome activation is of great significance and application value for exploring the genesis and development mechanism of these diseases and seeking new prevention and treatment ways.NLRP3 inflammasome can be activated by various agonists,such as urate crystals,Nig,ATP,glucose and other metabolites.Due to the diversity of these agonists and lack of explicit research which shows NLRP3 could directly bind to these agonists,there is no unified conclusion on the mechanism of NLRP3 inflammasome activation,which needs to be further explored.The zinc finger antiviral protein ZAP(coded by zinc-finger CCCH-type antiviral protein 1,ZC3HAV1),also called PARP13(ADP-ribosyltransferase diphtheria toxinlike 13),is a member of the PARP family.It could recognize and recruit viral RNA in cytoplasm,and bind to ZRE(ZAP responsive element)of RNA virus,thus degrading the viral RNAs through its N-terminal zinc finger domain.Furthermore,this antiviral effect is independent of TLRs and RLRs.It has been reported that ZAP has several isoforms,most of which ZAPL and ZAPS are the most investigated,and the isoforms have different antiviral activities.ZAPL is more sensitive against Sindbis virus(SINV)and HIV-1 than ZAPS,while ZAPS is more resistant to XMRV and HBV than ZAPL.However,the roles of ZAP isoforms,especially ZAPL and ZAPS,in inflammation remains unclear.It has been reported that ZAPS is more easily induced than ZAPL in interferon treatment or viral infection,and could target RIG-I and facilitate its oligomerization and ATPase activity,thus promoting Type Ⅰ IFNs expression.As is known that NLRP3 oligomerization is a key step in NLRP3 inflammasome activation.Therefore,we wondered whether ZAP could regulate NLRP3 inflammasome activation via targeting NLRP3 oligomerization,thus playing important roles in NLRP3-related diseases.In our preliminary experiments,we found that LPS greatly induced ZAP expression,and IL-1β suppressed its expression,suggesting that ZAP may be involved in the regulation of inflammation.Meanwhile,the data showed that ZAPS expression is greater induced than ZAPL.So we mainly explored the roles of ZAPS in inflammation.We used the small interfering RNA and gene knockout of Zap to conduct the following study.Our data showed that Zap knockdown or knockout significantly reduced the secretion of IL-1β and the cleavage of Caspase-1 induced by NLRP3 inflammasome activation.Next,we found that ZAPS could specifically bind to NLRP3 via co-immunoprecipitation,but had no effect on NLRP3 expression.Subsequently,we explored the roles of ZAP in NLRP3 oligomerization,and found that both ZAPS and ZAPL could promote NLRP3 oligomerization,and the effect of ZAPS is more obvious.Over all,ZAPS facilitates the activation of NLRP3 inflammasome by promoting the oligomerization of NLRP3.The significance and innovation of this study is that we further deepen the understanding of mechanisms of NLRP3 inflammasome activation via exploring the role and molecular mechanism of ZAP in NLRP3 inflammasome activation;In the next plan,we will use Zap knockout mice to construct NLRP3-related disease models to further explore the physiological role of ZAP,which will provide new drug targets and ideas for the prevention and treatment of NLRP3-related diseases.