Transcriptional regulation of CYP2C9 gene. Role of glucocorticoid receptor and constitutive androstane receptor.
Although cytochrome P450 2C9 (CYP2C9) is a major CYP expressed in the adult human liver, its mechanism of regulation is poorly known. In previous work, we have shown that CYP2C9 is inducible in primary human hepatocytes by xenobiotics including dexamethasone, rifampicin, and phenobarbital. The aim of this work was to investigate the molecular mechanism(s) controlling the inducible expression of CYP2C9. Deletional analysis of CYP2C9 regulatory region (+21 to -2088) in the presence of various hormone nuclear receptors suggested the presence of two functional response elements, a glucocorticoid receptor-responsive element (-1648/-1684) and a constitutive androstane receptor-responsive element (CAR, -1783/-1856). Each of these were characterized by co-transfection experiments, directed mutagenesis, gel shift assays, and response to specific antagonists RU486 and androstanol. By these experiments we located a glucocorticoid-responsive element imperfect palindrome at -1662/-1676, and a DR4 motif at -1803/-1818 recognized and transactivated by human glucocorticoid receptor and by hCAR and pregnane X receptor, respectively. Identification of these functional elements provides rational mechanistic basis for CYP2C9 induction by dexamethasone (submicromolar concentrations), and by phenobarbital and rifampicin, respectively. CYP2C9 appears therefore to be a primary glucocorticoid-responsive gene, which in addition, may be induced by xenobiotics through CAR/pregnane X receptor activation.
Gerbal-Chaloin
Sabine
S
INSERM U128, IFR24, Campus CNRS, 1919 Route de Mende, 34293 Montpellier, France.
Daujat
Martine
M
Pascussi
Jean-Marc
JM
Pichard-Garcia
Lydiane
L
Vilarem
Marie-Jose
MJ
Maurel
Patrick
P
D001189:Aryl Hydrocarbon Hydroxylases; D002478:Cells, Cultured; D000090702:Constitutive Androstane Receptor; D003513:Cycloheximide / Q000494:pharmacology; D065729:Cytochrome P-450 CYP2C9; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic; D022781:Hepatocytes / Q000201:enzymology; D006801:Humans; D000077297:Pregnane X Receptor; D012333:RNA, Messenger / Q000032:analysis; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D011965:Receptors, Glucocorticoid / Q000502:physiology*; D018168:Receptors, Retinoic Acid / Q000502:physiology; D011987:Receptors, Steroid / Q000502:physiology; D020218:Response Elements; D047488:Retinoid X Receptors; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000235:genetics*; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
D000090702:Constitutive Androstane Receptor; D000077297:Pregnane X Receptor; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011965:Receptors, Glucocorticoid; D018168:Receptors, Retinoic Acid; D011987:Receptors, Steroid; D047488:Retinoid X Receptors; D014157:Transcription Factors; D003577:Cytochrome P-450 Enzyme System; D003513:Cycloheximide; D013250:Steroid Hydroxylases; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; D039181:Steroid 16-alpha-Hydroxylase