Transcriptional regulation of the human Na+/H+ exchanger NHE3 by serotonin in intestinal epithelial cells.
Serotonin (5-HT) decreases NHE2 and NHE3 activities under acute conditions in human intestinal epithelial cells. Here, we have investigated the effects of 5-HT on expression of the human NHE3 gene and the mechanisms underlying its transcriptional regulation in differentiated C2BBe1 cells. Treatment of the human intestinal epithelial cell line, C2BBe1, with 5-HT (20 microM) resulted in a significant decrease in NHE3 mRNA and protein expression. In transient transfection studies, 5-HT repressed the NHE3 promoter activity by approximately 55%. The repression of the NHE3 promoter activity in response to 5-HT was accompanied by reduced DNA-binding activity of transcription factors Sp1 and Sp3 to the NHE3 promoter without alteration in their nuclear levels. Pharmacological inhibitors of protein kinase C reversed the inhibitory effect of 5-HT on the promoter activity. Our data indicate that 5-HT suppresses the transcriptional activity of the NHE3 promoter and this effect may be mediated by PKCalpha and modulation of DNA-binding affinities of Sp1 and Sp3.
Amin
Md Ruhul
MR
Section of Digestive Diseases and Nutrition, Department of Medicine, University of Illinois at Chicago, 840 S. Wood Street, Chicago, IL 60612, USA.
Ghannad
Leda
L
Othman
Ahmad
A
Gill
Ravinder K
RK
Dudeja
Pradeep K
PK
Ramaswamy
Krishnamurthy
K
Malakooti
Jaleh
J
D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D020218:Response Elements / Q000187:drug effects; D012701:Serotonin / Q000378:metabolism* / Q000494:pharmacology; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics*; D016329:Sp1 Transcription Factor / Q000378:metabolism; D051705:Sp3 Transcription Factor / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
C000613385:SLC9A3 protein, human; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D016329:Sp1 Transcription Factor; D051705:Sp3 Transcription Factor; D012701:Serotonin; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C