Zika Virus NS2B Recruits NS3 And Activates Its Protease Activity

Background and ObjectiveZika virus(ZIKV)is an emergent flavivirus associated with severe neurological disorders including microcephaly in newborns and Guillain-Barre syndrome in adults.Currently,there is no effective drug or vaccine for ZIKV infection or other flaviviruses infections.Research on the molecular mechanisms of viral replication is vital for the development of antiviral drugs and vaccines.ZIKV NS3 protein is a viral protease that cleaves the ZIKV polyprotein precursor into individual viral proteins,leading to the fact that NS3 protease becomes a popular drug target.Although recent studies have solved the structure of the ZIKV NS2B-NS3 complex and have provided conformational information on NS3 protease,how NS2B affects NS3 function during viral replication is not yet clear.We aim to explore the effects of NS2B on the functions of NS3.Methods,Content and ResultsIn this study,we identified ZIKV NS2B as a crucial factor in recruiting NS3 to the endoplasmic reticulum(ER)and activating its protease activity.We found that ZIKV NS3 by itself exhibited mitochondrial localization,which was quite different from its ER localization in ZIKV-infected cells.We screened viral proteins and identified NS2B as the bona fide recruiter of NS3 to the ER.The NS2B C-terminal tail interacted with NS3 protease domain to retain NS3 on the ER.?-Sheet motifs that formed between NS2B and the NS3 protease domain played important roles in their interaction,while mutation in the ?-strand of NS2B attenuated NS2B-NS3 interaction and impaired the ability of NS3 protease to cleave the polyprotein precursor into multiple viral proteins.Consequently,NS2B mutations led to severe inhibition of ZIKV replication and production due to insufficient NS3 protease activity.Conclusions and SignificanceOur study reveals the critical role of NS2B in NS3 recruitment and protease function and provides mechanistic insight into ZIKV replication.The results of this study help to elucidate the role of NS2B-NS3 protease in ZIKV replication and would help the development of new antiviral drugs targeting NS3 protease.