The interaction between host Annexin A2 and viral Nsp9 is beneficial for replication of porcine reproductive and respiratory syndrome virus.

Non-structural protein 9 (Nsp9), a RNA-dependent RNA polymerase (RdRp) of the porcine reproductive and respiratory syndrome virus (PRRSV), is necessary for PRRSV replication. However, the binding partners of Nsp9 have not been identified. In this study, seven host proteins were identified as Nsp9-binding proteins using yeast two-hybrid (Y2H). Among of them, we confirmed the interaction of Nsp9 with Annexin A2 (ANXA2) using Y2H, Co-immunoprecipitation (Co-IP), GST pulldown and immunofluorescence assay (IFA). We found that only full-length ANXA2 could bind with Nsp9 in vitro and Nsp9 interacted with endogenous ANXA2 in PRRSV-infected MARC-145 cells. In addition, we found that the Nsp9-ANXA2 interaction was partially reduced by RNase A treatment. Furthermore, PRRSV growth was significantly hindered in ANXA2-knockdown MARC-145 cells. Taken together, these results indicate that Nsp9 binding partner ANXA2 is beneficial for PRRSV replication.