Functional characterization of the ER stress induced X-box-binding protein-1 (Xbp-1) in the porcine system

Abstract

AbstractBackgroundThe unfolded protein response (UPR) is an evolutionary conserved adaptive reaction for increasing cell survival under endoplasmic reticulum (ER) stress conditions. X-box-binding protein-1 (Xbp1) is a key transcription factor of UPR that activates genes involved in protein folding, secretion, and degradation to restore ER function. The UPR induced by ER stress was extensively studied in diseases linked to protein misfolding and aggregations. However, in the porcine system, genes in the UPR pathway were not investigated. In this study, we isolated and characterized the porcineXbp1(pXbp1) gene in ER stress using porcine embryonic fibroblast (PEF) cells and porcine organs. ER stress was induced by the treatment of tunicamycin and cell viability was investigated by the MTT assay. For cloning and analyzing the expression pattern ofpXbp1, RT-PCR analysis and Western blot were used. Knock-down ofpXbp1was performed by the siRNA-mediated gene silencing.ResultsWe found that thepXbp1mRNA was the subject of the IRE1α-mediated unconventional splicing by ER stress. Knock-down ofpXbp1enhanced ER stress-mediated cell death in PEF cells. In adult organs,pXbp1mRNA and protein were expressed and the spliced forms were detected.ConclusionsIt was first found that the UPR mechanisms and the function of pXbp1 in the porcine system. These results indicate that pXbp1 plays an important role during the ER stress response like other animal systems and open a new opportunity for examining the UPR pathway in the porcine model system.