Activated sterol regulatory element-binding protein-2 suppresses hepatocyte nuclear factor-4-mediated Cyp3a11 expression in mouse liver

Mol Pharmacol. 2011 Jan;79(1):148-56. doi: 10.1124/mol.110.068577. Epub 2010 Oct 6.

Abstract

Sterol regulatory element-binding protein-2 (SREBP-2) is a key transcription factor for the cholesterol homeostasis. Recent studies have suggested the association of CYP3A enzymes, major drug-metabolizing enzymes, with cholesterol metabolism. In the present study, we have investigated a possible involvement of SREBP-2 in hepatic Cyp3a11 expression. Feeding a low-cholesterol diet (LCD) to mice activated hepatic SREBP-2 whereas it attenuated hepatic Cyp3a11 expression. These phenomena were reversed by cholesterol supplementation to LCD. In reporter assays, the overexpression of constitutively active SREBP-2 reduced Cyp3a11 reporter activity through the region from -1581 to -1570 of Cyp3a11. This region contained a putative hepatocyte nuclear factor-4α (HNF-4α) binding motif, and HNF-4α, but not SREBP-2, bound to the motif in in vitro binding assays. With the mutation or deletion of this motif, the SREBP-2-dependent suppression of Cyp3a11 expression disappeared in reporter assays. In pull-down assays and coimmunoprecipitation assays, SREBP-2 bound to peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), a major coactivator for HNF-4α, via its transactivation domain and inhibited the interaction between HNF-4α and PGC-1α in vitro. A mutant SREBP-2 lacking the transactivation domain consistently failed to reduce Cyp3a11 reporter activity. Furthermore, PGC-1α overexpression relieved the SREBP-2-mediated reduction of Cyp3a11 reporter activity. Finally, chromatin immunoprecipitation assays demonstrated that the extent of PGC-1α binding to the Cyp3a11 promoter was reduced by LCD-feeding in mouse livers. In conclusion, activated SREBP-2 interacts with PGC-1α in mouse livers at reduced cholesterol intake. This results in the reduced PGC-1α recruitment to HNF-4α on the Cyp3a11 promoter and the subsequent down-regulation of Cyp3a11 expression.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cholesterol, Dietary / administration & dosage
  • Cytochrome P-450 CYP3A / biosynthesis
  • Cytochrome P-450 CYP3A Inhibitors*
  • Gene Expression Regulation, Enzymologic*
  • Hep G2 Cells
  • Hepatocyte Nuclear Factor 4 / antagonists & inhibitors*
  • Hepatocyte Nuclear Factor 4 / physiology
  • Humans
  • Liver / drug effects
  • Liver / metabolism*
  • Male
  • Membrane Proteins / antagonists & inhibitors*
  • Membrane Proteins / biosynthesis
  • Mice
  • Mice, Inbred C57BL
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • Salmon
  • Sterol Regulatory Element Binding Protein 2 / metabolism*
  • Trans-Activators / metabolism*
  • Transcription Factors

Substances

  • Cholesterol, Dietary
  • Cytochrome P-450 CYP3A Inhibitors
  • Hepatocyte Nuclear Factor 4
  • Membrane Proteins
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • Ppargc1a protein, mouse
  • Sterol Regulatory Element Binding Protein 2
  • Trans-Activators
  • Transcription Factors
  • Cyp3a11 protein, mouse
  • Cytochrome P-450 CYP3A