Transmissible gastroenteritis virus nsp7 protein localized in the cytoplasm down-regulates interleukin 8 expression in porcine intestinal epithelial cell.

Abstract

Transmissible gastroenteritis virus (TGEV) is an important pathogen in swine that is responsible for substantial economic losses. Previous studies suggest that the TGEV non-structural protein 7 (nsp7) plays an important role in the viral assembly process. However, the subcellular localization and other functions of the TGEV nsp7 protein are still unclear. In this study we have examined the subcellular localization and other functions of TGEV nsp7 protein through analysis of its effects on cell growth, cell cycle progression, interleukin 8 (IL-8) expression, and NF-κB activation. Our results showed that the nsp7 protein is localized in the cytoplasm and has no effect on intestinal epithelial cells (IECs) growth, cell cycle, and cyclin A expression. Further studies showed that TGEV nsp7 protein had no effect on GRP78 expression, could not induce endoplasmic reticulum (ER) stress and activate NF-κB activity. Interestingly, the IECs expressing nsp7 protein secreted lower levels of IL-8 than control cells. This is the first report to demonstrate the subcellular localization and novel functions of TGEV nsp7 protein. These findings provide novel information about the function of the poorly characterized TGEV non-structural protein 7.