At 24 h postinfection (hpi), both PDCoV- and mock-infected IPEC-J2 cells grown in T25 flasks (∼5 × 106 cells/flask) were rinsed twice with prechilled PBS, and then harvested with disposable cell scrapers. Three flasks of each group (PDCoV or mock) were harvested and used as three independent biological replicates. After centrifugation at 300g for 10 min, the cell pellets from each flask were lysed with 800 μL of RIPA lysis buffer (Beyotime, Shanghai, China) containing 1% SDS, 8 M urea and protease inhibitors (Beyotime). The cell lysates were further sonicated on ice for 5 min with 10 s bursts and 10 s pauses between cycles. After centrifugation for 20 min at 12 000g and 4 °C, the supernatant was collected and used as the total cellular proteins. The concentration of protein samples was determined using a Pierce BCA protein assay kit (Thermo Scientific, Rockford, IL, USA).