Porcine epidemic diarrhea virus M protein blocks cell cycle progression at S-phase and its subcellular localization in the porcine intestinal epithelial cells.

Porcine epidemic diarrhea (PED) caused by virulent strains of porcine epidemic diarrhea virus (PEDV) is a highly contagious enteric disease of swine characterized by severe enteritis, vomiting, and watery diarrhea. This study investigates the subcellular localization and function of PEDV M protein through examination of its effects on cell growth, cell cycle progression, and interleukin 8 (IL-8) expression. Our results revealed that the PEDV M protein is localized throughout the cytoplasm. The M protein altered swine intestinal epithelial cell line (IEC) growth and induced cell cycle arrest at the S-phase via the cyclin A pathway. The S-phase arrest is associated with a decrease in level of cyclin A. Furthermore, our results revealed that the M protein of PEDV does not induce endoplasmic reticulum (ER) stress and does not activate NF-κB which is responsible for IL-8 and Bcl-2 expression. This is the first report to demonstrate that the PEDV M protein is localized in the whole cell and induces cell cycle arrest at the S-phase. This study provides novel findings in the function of M proteins of PEDV.