Cycloheximide increases glucocorticoid-stimulated alpha -ENaC mRNA in collecting duct cells by p38 MAPK-dependent pathway.
Aldosterone and glucocorticoids (GCs) stimulate Na(+) reabsorption in the collecting ducts by increasing the activity of the epithelial Na(+) channel (ENaC). Our laboratory has used Madin-Darby canine kidney-C7 cells to demonstrate that this effect is associated with an increase in alpha-ENaC gene transcription (Mick VE, Itani OA, Loftus RW, Husted RF, Schmidt TJ, and Thomas CP, Mol Endocrinol 15: 575-588, 2001). Cycloheximide (CHX) superinduced the GC-stimulated alpha-ENaC expression in a dose-dependent manner, but had no effect on basal or aldosterone-stimulated alpha-ENaC expression, whereas anisomycin inhibited basal and corticosteroid-stimulated alpha-ENaC expression. The superinduction of alpha-ENaC expression was also seen with hypotonicity, was blocked by RU-38486, and was independent of protein synthesis. CHX had no effect on alpha-ENaC mRNA half-life, confirming that its effect was via an increase in alpha-ENaC transcription. The effect of CHX and hypotonicity on alpha-ENaC expression was abolished by SB-202190, indicating an effect mediated via p38 MAPK. Consistent with this scheme, CHX increased pp38 and MKK6, an upstream activator of p38, stimulated alpha-ENaC promoter activity. These data confirm a model in which CHX activates p38 in Madin-Darby canine kidney-C7 cells to increase alpha-ENaC gene transcription in a GC-dependent manner.
Itani
Omar A
OA
Department of Internal Medicine, and Graduate Program in Molecular Biology, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.
Cornish
Kristyn L
KL
Liu
Kang Z
KZ
Thomas
Christie P
CP
D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology; D004285:Dogs; D004640:Emetine / Q000494:pharmacology; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053503:Epithelial Sodium Channels; D015870:Gene Expression / Q000187:drug effects; D005938:Glucocorticoids / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007038:Hypotonic Solutions / Q000494:pharmacology; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015735:Mifepristone / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases
D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D053503:Epithelial Sodium Channels; D005938:Glucocorticoids; D007038:Hypotonic Solutions; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D015222:Sodium Channels; D015735:Mifepristone; D000450:Aldosterone; D003907:Dexamethasone; D003513:Cycloheximide; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D004640:Emetine