Heat shock protein A1 inhibits the replication of foot-and-mouth disease virus by degrading viral RNA polymerase 3D through chaperone-mediated autophagy.

Foot-and-mouth disease virus (FMDV), a member of the Picornaviridae family, is a single-stranded, positive-sense RNA virus. Heat shock protein A1 (HSPA1) has been shown to influence the entry, translation, assembly, and release of enterovirus A71 (EV-A71), another Picornaviridae family member. In this study, we demonstrate that HSPA1 plays a different role in the replication of FMDV. By investigating various stages of virus replication, we found that HSPA1 specifically inhibits the RNA replication stage in which HSPA1 inhibits viral RNA replication by degrading the viral RNA-dependent RNA polymerase (RdRp), 3D protein. In the presence of specific inhibitors, we find out that this degradation occurs through the autophagy pathway. Activation and blockage of chaperone-mediated autophagy (CMA) demonstrate that HSPA1 degrades 3D through the CMA pathway. Mutation analysis reveals that (421)QEKLI(425) is the key motif in 3D responsible for HSPA1-mediated CMA degradation. In summary, this study shows that HSPA1 can degrade the viral 3D protein through the CMA pathway, thereby inhibiting the RNA replication of FMDV and interfering with virus infection. This study, for the first time, demonstrates that HSPA1 employs its chaperone function to mediate the degradation of the FMDV RdRp, revealing the crucial role of HSPA1 in the FMDV infection process and suggesting that HSPA1 could be a potential target for the prevention and treatment of FMDV infection. IMPORTANCE: Viral RNA replication is the key stage in understanding the pathogenic mechanisms of foot-and-mouth disease virus (FMDV). During this process, the viral non-structural protein 3D serves as an RNA-dependent RNA polymerase (RdRp) to synthesize progeny RNA using the viral genomic RNA as a template. However, the regulatory effect of host cells on FMDV 3D proteins has not yet been studied. In this study, we find that heat shock protein A1 (HSPA1) degrades the viral 3D protein through the chaperone-mediated autophagy (CMA) pathway, thereby inhibiting the RNA replication of FMDV and interfering with virus infection. This study, for the first time, demonstrates that HSPA1 employs its chaperone function to mediate the degradation of the FMDV RdRp.