Restoration of ENaC expression by glucocorticoid receptor transfection in human HT-29/B6 colon cells.
The epithelial sodium channel (ENaC) controls colonic sodium absorption. So far, investigation of ENaC was limited by an unexplained lack of steroid-dependent ENaC expression in cultured intestinal cells, which we aimed to resolve. HT-29/B6 cells constitutively expressed the alpha-ENaC subunit, while beta- and gamma-ENaC subunits could not be detected due to deficient basal as well as corticosteroid-induced transcription. This was due to a lack of expression of both activating and inhibiting isoforms of glucocorticoid receptor (GR-alpha, -beta) and mineralocorticoid receptor. Stable transfection of GR-alpha restored intestine-specific glucocorticoid upregulation of beta- and gamma-ENaC in HT-29/B6 cells, which was followed by intact targeting of ENaC channels to the apical cell membrane and dose-dependent induction of electrogenic sodium absorption. In conclusion, ENaC deficiency is due to a lack of steroid receptors and not the consequence of a crypt-like phenotype of cultured intestinal cells. By stable GR transfection we obtained a model, in which ENaC regulation can be studied.
Zeissig
Sebastian
S
Department of Gastroenterology, Charité, Campus Benjamin Franklin, Berlin, Germany. sebastian.zeissig@charite.de
Fromm
Anja
A
Mankertz
Joachim
J
Zeitz
Martin
M
Fromm
Michael
M
Schulzke
Jörg D
JD
D003106:Colon / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D053503:Epithelial Sodium Channels; D005938:Glucocorticoids / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D011188:Potassium / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000502:physiology*; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D053503:Epithelial Sodium Channels; D005938:Glucocorticoids; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D015222:Sodium Channels; C411470:glucocorticoid receptor alpha; D011188:Potassium