Cellular DNAJA3, a Novel VP1-Interacting Protein, Inhibits Foot-and-Mouth Disease Virus Replication by Inducing Lysosomal degradation of VP1 and Attenuating its Antagonistic Role on the IFN-β signaling pathway.

DnaJ heat shock protein family (Hsp40) member A3 (DNAJA3) plays an important role in viral infections. However, the role of DNAJA3 in replication of footand-mouth-disease virus (FMDV) remains unknown. In this study, DNAJA3, a novel binding partner of VP1, was identified using yeast two-hybrid screening. The DNAJA3-VP1 interaction was further confirmed by coimmunoprecipitation and colo-calization in FMDV-infected cells. The J domain of DNAJA3 (amino acids 1 to 168) and the lysine at position 208 (K208) of VP1 were shown to be critical for the DNAJA3-VP1 interaction. Overexpression of DNAJA3 dramatically dampened FMDV replication, whereas loss of function of DNAJA3 elicited opposing effects against FMDV replication. Mechanistical study demonstrated that K208 of VP1 was critical for reducing virus titer caused by DNAJA3 using K208A mutant virus. DNAJA3 induced lysosomal degradation of VP1 by interacting with LC3 to enhance the activation of lysosomal pathway. Meanwhile, we discovered that VP1 suppressed the beta interferon (IFN-beta) signaling pathway by inhibiting the phosphorylation, dimerization, and nuclear translocation of IRF3. This inhibitory effect was considerably boosted in DNAJA3-knockout cells. In contrast, overexpression of DNAJA3 markedly attenuated VP1-mediated suppression on the IFN-beta signaling pathway. Poly(I.C)-induced phosphorylation of IRF3 was also decreased in DNAJA3-knockout cells compared to that in the DNAJA3-WT cells. In conclusion, our study described a novel role for DNAJA3 in the host's antiviral response by inducing the lysosomal degradation of VP1 and attenuating the VP1-induced suppressive effect on the IFN-beta signaling pathway. IMPORTANCE This study pioneeringly determined the antiviral role of DNAJA3 in FMDV. DNAJA3 was found to interact with FMDV VP1 and trigger its degradation via the lysosomal pathway. In addition, this study is also the first to clarify the mechanism by which VP1 suppressed IFN-beta signaling pathway by inhibiting the phosphorylation, dimerization, and nuclear translocation of IRF3. Moreover, DNAJA3 significantly abrogated VP1-induced inhibitive effect on the IFN-beta signaling pathway. These data suggested that DNAJA3 plays an important antiviral role against FMDV by both degrading VP1 and restoring of IFN-beta signaling pathway.