title: Epidermal growth factor receptor expression and signaling are essential in glutamine's cytoprotective mechanism in heat-stressed intestinal epithelial-6 cells.
abstract: Epidermal growth factor receptor (EGFR) expression and signaling can induce cellular protection after intestinal inflammation. L-Glutamine (GLN) is known to prevent apoptosis after intestinal injury by activating MAPK and phosphatidylinositol 3-kinase (PI3-K)/Akt pathways. However, the role of EGFR expression and signaling in GLN-mediated cellular protection in intestinal epithelial-6 (IEC-6) cells after heat stress (HS) is unknown. To address the role of EGFR in GLN-mediated protection, IEC-6 cells were treated with GLN in the presence or absence of EGFR small interfering RNA, the EGFR tyrosine kinase inhibitor AG1478, the ERK1/2 inhibitor PD98059, the p38MAPK inhibitor SB203580, or the PI3-K/Akt inhibitor LY294002 under basal and HS conditions. GLN-mediated cell survival was measured using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. Phosphorylated and/or total levels of EGFR, cleaved caspase-3, poly(ADP-ribose) polymerase-1, ERK1/2, p38MAPK, and Akt were assessed by Western blotting. We showed that HS induced a decrease in total, cytoplasmic, and nuclear EGFR levels in IEC-6 cells, which was prevented by GLN supplementation, leading to attenuated apoptosis via EGFR small interfering RNA. Furthermore, the protective effect of GLN was lessened by AG1478, PD98059, and LY294002 but was not affected by SB203580. AG1478 attenuated GLN-mediated increases in ERK1/2 and decreases in p38MAPK phosphorylation. However, AG1478 had no effect on GLN-mediated augmentations in Akt phosphorylation. In summary, EGFR expression was important in the protective mechanism of GLN, as well as GLN-mediated activation of EGFR tyrosine kinase activity. GLN-mediated EGFR signaling activated ERK1/2 and decreased p38MAPK signaling. However, GLN-mediated Akt phosphorylation after HS seems to be independent of EGFR signaling.
authors.affiliation: Department of Anesthesiology, University of Colorado, Colorado, Aurora, CO, USA. Stefanie.Niederlechner@ucdenver.edu
authors.forename: Stefanie
authors.initials: S
authors.lastname: Niederlechner
authors.forename: Christine
authors.initials: C
authors.lastname: Baird
authors.forename: Benjamin
authors.initials: B
authors.lastname: Petrie
authors.forename: Erhard
authors.initials: E
authors.lastname: Wischmeyer
authors.forename: Paul E
authors.initials: PE
authors.lastname: Wischmeyer
mesh_terms: D015153:Blotting, Western; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology*; D066246:ErbB Receptors / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*; D005973:Glutamine / Q000494:pharmacology*; D018882:Heat Stress Disorders / Q000235:genetics / Q000503:physiopathology*; D006801:Humans; D007422:Intestines / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000502:physiology; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology
chemical_list: D004791:Enzyme Inhibitors; D066246:ErbB Receptors; D005973:Glutamine; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D048051:p38 Mitogen-Activated Protein Kinases