The impairment of UPR increased PEDV replication. (A) Vero cells were transfected with shRNAs to knockdown protein PERK for 48 h, and then infected with PEDV for 36 h. Scramble shRNA plasmid was used as the negative control. PERK, eIF2α and phos-eIF2α expression and the N protein of PEDV were analyzed by Western blot. β-Actin was used as sample loading control. (B) PEDV titers in the supernatants were measured by plaque formation assays. (C) The RNA level of gene ORF3 from the infected cells was evaluated by Q-PCR. (D, E) Vero cells were infected with PEDV for 2 h, then treated with 4-PBA for 24 h. The Western blot was performed to test eIF2α and phospho-eIF2α expression and the change of N protein of PEDV. β-Actin was used as sample loading control.