Regulation of the human oxytocin receptor by nuclear factor-kappaB and CCAAT/enhancer-binding protein-beta.
BACKGROUND
Increased myometrial sensitivity to oxytocin at term is mediated through increased oxytocin receptor (OTR) expression. OTR promoter contains putative transcription factor-binding sites for activating protein-1 (AP-1), CCAAT/enhancer-binding protein (C/EBP), and nuclear factor-kappaB (NF-kappaB), which may be activated by IL-1beta, whose concentrations increase with labor.


OBJECTIVE
The objective of this study was to examine the effect of IL-1beta on OTR expression and the roles of AP-1, C/EBP, and NF-kappaB in OTR promoter function.


RESULTS
IL-1beta induces an increase in OTR mRNA concentrations and OTR ligand binding in myometrial cells, which is maximal at 4 h and decreased after 20 h. IL-1beta activates the transcription factors AP-1 C/EBPbeta, and NF-kappaB. Using computer-based analysis and EMSA studies, we have identified three AP-1, nine C/EBP, and three NF-kappaB DNA-binding sites in the OTR promoter. In transient transfection studies, OTR promoter activity was increased by C/EBPbeta and NF-kappaB, but not by AP-1. C/EBPbeta and NF-kappaB together had a synergistic action in the induction of OTR promoter activity. Site-directed mutagenesis of each individual C/EBP and NF-kappaB site had no effect on the ability of C/EBPbeta, NF-kappaB, or their combination to activate OTR promoter. However, mutation of both NF-kappaB sites inhibited promoter activation by NF-kappaB alone, but not that by the combination of C/EBPbeta and NF-kappaB. Deletion studies showed that a region between -851 and -656 of the OTR confers responsiveness to the combination of C/EBPbeta and NF-kappaB.


CONCLUSIONS
IL-1beta has a biphasic effect on OTR expression in myometrial cells, and C/EBP and NF-kappaB play synergistic roles in OTR promoter activation.
Parturition Research Group, Institute of Reproductive and Developmental Biology, Hammersmith Hospital Campus, Du Cane Road, East Acton, London W12 ONN, United Kingdom. v.terzidou@imperial.ac.uk
Vasso
V
Terzidou
Yooni
Y
Lee
Tamsin
T
Lindström
Mark
M
Johnson
Steven
S
Thornton
Phillip R
PR
Bennett
D022782:CCAAT-Enhancer-Binding Protein-beta / Q000502:physiology*; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D032342:Muscle Cells / Q000378:metabolism; D016328:NF-kappa B / Q000502:physiology*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D018045:Receptors, Oxytocin / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000378:metabolism
D022782:CCAAT-Enhancer-Binding Protein-beta; D007375:Interleukin-1; D016328:NF-kappa B; D012333:RNA, Messenger; D018045:Receptors, Oxytocin; D018808:Transcription Factor AP-1; D004247:DNA