ER stress induced by ionising radiation in IEC-6 cells.
OBJECTIVE
Ionising radiation (IR) can evoke a series of biochemical events inside the cell. However, whether IR can directly induce endoplasmic reticulum (ER) stress is not clear. In our previous study, we found that there might be a causative link between IR and ER stress. In this study, we further characterised the type of ER stress induced by IR.


METHODS
Rat intestinal epithelial cells IEC-6 were irradiated at a dose of 10 Gy, and total RNA and proteins were harvested at indicated time points. The mRNA and protein expression of immunoglobulin heavy chain binding protein (BiP) and glucose regulated protein 94 (GRP94) was detected along with proteins associated with ER stress signal pathways.


RESULTS
Our results indicated that IR induced up-regulation of ER stress marker including BiP and GRP94 at protein and mRNA levels in IEC-6 cells. Increased phosphorylation of eukaryotic translation initiation factor 2 (eIF2alpha) and induced mRNA splicing of X-box binding protein 1 (XBP1) suggested that PERK (interferon-induced double-stranded RNA-activated protein kinase (PRKR) -like endoplasmic reticulum kinase) and IRE1 (inositol requirement 1) signal transduction pathways were involved in this kind of ER stress. However, the active form of activating transcription factor 6 (ATF6) did not change significantly in irradiated cells, which suggested that the ATF6 pathway was not involved.


CONCLUSIONS
Thus, we concluded that IR could induce moderate ER stress directly in IEC-6 cells.
Zhang
Bo
B
Institute of Combined Injury, State Key Laboratory of Trauma, Burns and Combined Injury, Third Military Medical University, Chongqing, China.
Wang
Yan
Y
Pang
Xueli
X
Su
Yongping
Y
Ai
Guoping
G
Wang
Tao
T
D051702:Activating Transcription Factor 6 / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000528:radiation effects*; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism / Q000528:radiation effects*; D006360:Heat-Shock Proteins / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D014176:Protein Biosynthesis / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011839:Radiation, Ionizing; D051381:Rats; D015398:Signal Transduction / Q000528:radiation effects; D013312:Stress, Physiological / Q000528:radiation effects*; D014158:Transcription, Genetic / Q000528:radiation effects; D015854:Up-Regulation / Q000528:radiation effects; D019892:eIF-2 Kinase / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP
D051702:Activating Transcription Factor 6; D015415:Biomarkers; D006360:Heat-Shock Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D017346:Protein Serine-Threonine Kinases; D019892:eIF-2 Kinase; C497113:Atf6 protein, rat; C051684:GRP78 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP; C053387:endoplasmin; C486557:Ern2 protein, rat