Porcine epidemic diarrhea virus N protein prolongs S-phase cell cycle, induces endoplasmic reticulum stress, and up-regulates interleukin-8 expression

Abstract

Porcine epidemic diarrhea (PED) is an acute and highly contagious enteric disease of swine caused by porcine epidemic diarrhea virus (PEDV). The porcine intestinal epithelial cell is the PEDV target cell. In this study, we established a porcine intestinal epithelial cell (IEC) line which can stably express PEDV N protein. We also investigate the subcellular localization and function of PEDV N protein by examining its effects on cell growth, cycle progression, interleukin-8 (IL-8) expression, and survival. The results show that the PEDV N protein localizes in the endoplasmic reticulum (ER), inhibits the IEC growth and prolongs S-phase cell cycle. The S-phase is prolonged which is associated with a decrease of cyclin A transcription level and an increase of cyclin A degradation. The IEC expressing PEDV N protein can express higher levels of IL-8 than control cells. Further studies show that PEDV N protein induces ER stress and activates NF-κB, which is responsible for the up-regulation of IL-8 and Bcl-2 expression. This is the first report to demonstrate that PEDV N protein can induce cell cycle prolongation at the S-phase, ER stress and up-regulation interleukin-8 expression. These findings provide novel information on the function of the PEDV N protein and are likely to be very useful in understanding the molecular mechanisms responsible for PEDV pathogenesis.

Knockdown of CREB3/Luman by shRNA in Mouse Granulosa Cells Results in Decreased Estradiol and Progesterone Synthesis and Promotes Cell Proliferation

“…Cyclin A1 may function as the M-phase cyclin since the cell cycle progression was arrested at S phase in cyclin A1-deficient mice [37]. Cyclin B1 is associated with cyclin-dependent kinase 1 (cdk1), and is the key regulators of cell cycle progression from S phase to G2/M phase [38]. Thus, we surmised that the higher mRNA expression levels of Cyclin A1 and Cyclin B1 may be responsible for promoting cell cycle progression from S to M phase after Luman knockdown.…”

Continuous and Discontinuous RNA Synthesis in Coronaviruses

“…N protein nuclear localization is associated with induction of cell cycle arrest and inhibition of cytokinesis (68–72) and is involved in recruitment to the cytoplasm of cell nuclear proteins, such as heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) and the helicase DDX1 (34, 73). As noted above, N protein–recruited DDX1 functions in the RTC in facilitating TRS read-through and synthesis of long sgmRNAs (34).…”

Virulence factors in porcine coronaviruses and vaccine design

“…In fact, the interaction of TGEV N protein with several host cell proteins has been shown (Zhang et al, 2015b; Zhang et al, 2014c), and overexpression of PDCoV N protein in porcine cells affected the accumulation of many host cell proteins (Lee and Lee, 2015). In addition, both TGEV and PEDV N protein overexpression induces cell cycle arrest (Ding et al, 2014a; Xu et al, 2013b). …”

“…Nevertheless, there is accumulating evidence indicating that N protein could be a virulence factor. PEDV N protein expression has been correlated with the activation of NF-κB and increased production of pro-inflammatory cytokines (Xu et al, 2013b) possibly by the activation of Toll-like receptor (TLR) pathways (Cao et al, 2015b). On the other hand, PEDV N protein overexpression prevents TBK1-IRF3 interaction, avoiding IRF3 activation and IFN production (Ding et al, 2014b).…”