Heparanase attenuates Zika virus infection by destabilizing the viral envelope protein

Heparanase (Hpa) is the only endoglycosidase enzyme in mammalian cells capable of cleaving heparan sulfate. In addition to its well-known functions in the regulation of glycosaminoglycans integrity, accumulating evidence indicates that Hpa plays vital roles in viral infection, while the mechanisms are not yet fully understood, especially in RNA virus infection. In this study, we report that Hpa functions as a restriction factor for Zika virus (ZIKV) infection. Our results demonstrated that Hpa, but not the enzymatic inactive mutant (Hpa-DM), resulted in degradation of the ZIKV envelope (E) protein, which could be rescued by treatment of the proteasome inhibitor (MG132) and the autophagy inhibitor (NH ₄ Cl), separately. Additionally, the ubiquitination of ZIKV E did not show an significant change in the presence of Hpa. Overexpression of Hpa, but not Hpa-DM, dramatically decreased ZIKV infection in different cell models, evidenced by the reduction of viral proteins and a compromised production of infectious virions. This was further confirmed by the results in MEF cells, in which knockout Hpa enhanced ZIKV infection, while overexpression of Hpa suppressed the production of virions. In addition, ZIKV was found to downregulate the Hpa expression, which could counteract the inhibitory effects of Hpa. Altogether, our study discovers an unrecognized role of Hpa in virus infection and demonstrates that Hpa serves as a restriction factor for ZIKV infection.