Identification of human CYP2C8 as a retinoid-related orphan nuclear receptor target gene.
Retinoid-related orphan nuclear receptors (RORs) alpha and gamma (NR1F1, -3) are highly expressed in liver, adipose tissue, thymus, and brain and are involved in many physiological processes, such as circadian rhythm and immune function. Enzymes in the cytochrome P450 2C subfamily metabolize many clinically important drugs and endogenous compounds, such as the anticancer drug paclitaxel and arachidonic acid, and are highly expressed in liver. Here, we present the first evidence that RORs regulate the transcription of human CYP2C8. Overexpression of RORalpha and RORgamma in HepG2 cells significantly enhanced the activity of the CYP2C8 promoter but not that of the CYP2C9 or CYP2C19 promoters. Computer analyses, promoter deletion studies, gel shift assays, and mutational analysis identified an essential ROR-responsive element at -2045 base pairs in the CYP2C8 promoter that mediates ROR transactivation. Adenoviral overexpression of RORalpha and -gamma significantly induced endogenous CYP2C8 transcripts in both HepG2 cells and human primary hepatocytes. Knockdown of endogenous RORalpha and -gamma expression in HepG2 cells by RNA interference decreased the expression of endogenous CYP2C8 mRNA by approximately 50%. These data indicate that RORs transcriptionally up-regulate CYP2C8 in human liver and, therefore, may be important modulators of the metabolism of drugs and physiologically active endogenous compounds by this enzyme in liver and possibly extrahepatic tissues where RORs are expressed.
Chen
Yuping
Y
Laboratory of Pharmacology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
Coulter
Sherry
S
Jetten
Anton M
AM
Goldstein
Joyce A
JA
D000256:Adenoviridae / Q000235:genetics; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics* / Q000502:physiology; D015153:Blotting, Western; D002460:Cell Line; D002478:Cells, Cultured; D065727:Cytochrome P-450 CYP2C8; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D015870:Gene Expression / Q000187:drug effects; D005822:Genetic Vectors; D022781:Hepatocytes / Q000502:physiology; D006801:Humans; D008099:Liver / Q000201:enzymology; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D057132:Nuclear Receptor Subfamily 1, Group F, Member 3; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics* / Q000502:physiology; D018168:Receptors, Retinoic Acid / Q000235:genetics* / Q000502:physiology; D011988:Receptors, Thyroid Hormone / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics* / Q000502:physiology; D015533:Transcriptional Activation; D014162:Transfection
D018076:DNA, Complementary; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D057132:Nuclear Receptor Subfamily 1, Group F, Member 3; D034741:RNA, Small Interfering; C539738:RORA protein, human; C539900:RORC protein, human; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D015534:Trans-Activators; D001189:Aryl Hydrocarbon Hydroxylases; C450259:CYP2C8 protein, human; D065727:Cytochrome P-450 CYP2C8