Foot-and-mouth disease virus induces lysosomal degradation of host protein kinase PKR by 3C proteinase to facilitate virus replication

- FMDV infection triggers PKR mRNA expression, while decreases PKR protein levels.
- 3Cpro was responsible for FMDV-induced inhibition of PKR expression and activation.
- 3Cpro-induced PKR reduction was independent of its proteinase activity.
- 3Cpro induces PKR degradation by lysosomal pathway.

The interferon-induced double-strand RNA activated protein kinase (PKR) plays important roles in host defense against viral infection. Here we demonstrate the significant antiviral role of PKR against foot-and-mouth disease virus (FMDV) and report that FMDV infection inhibits PKR expression and activation in porcine kidney (PK-15) cells. The viral nonstructural protein 3 C proteinase (3Cpro) is identified to be responsible for this inhibition. However, it is independent of the well-known proteinase activity of 3Cpro or 3Cpro-induced shutoff of host protein synthesis. We show that 3Cpro induces PKR degradation by lysosomal pathway and no interaction is determined between 3Cpro and PKR. Together, our results indicate that PKR acts an important antiviral factor during FMDV infection, and FMDV has evolved a strategy to overcome PKR-mediated antiviral role by downregulation of PKR protein.