SRC-3 is required for CAR-regulated hepatocyte proliferation and drug metabolism

J Hepatol. 2012 Jan;56(1):210-7. doi: 10.1016/j.jhep.2011.07.015. Epub 2011 Aug 7.


Background & aims: Nuclear receptors such as pregnane X receptor and constitutive androstane receptor (CAR) are important regulators of drug-metabolizing systems such as P450 enzymes and modulate xenobiotic metabolism as well as hepatocellular proliferation. Binding of CAR to NR response elements alone is not sufficient to activate gene expression. Here, we investigate the role of steroid receptor co-activator (SRC) family members in CAR-mediated hepatocyte proliferation and drug metabolism.

Methods: The role of SRCs in CAR activation was assessed in cell-based transfection assays and protein-protein interaction assays. The in vivo role of SRCs in CAR-mediated hepatocyte proliferation and drug metabolism was examined by using mice deficient in SRCs.

Results: SRC-3 displayed the highest co-activating activity to CAR compared with SRC-1 and SRC-2 in a cell-based reporter assay. Knockout of SRC-3 in mice attenuated hepatic hyperplasia induced by a CAR agonist 1,4-bis-[2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP), which was associated with a reduced expression of c-Myc and Foxm-1. In contrast, knockout of SRC-1 or SRC-2 in mice did not affect TCPOBOP-induced hepatic hyperplasia. SRC-3-deficient mice were hypersensitive to zoxazolamine-induced paralysis, but were resistant to acetaminophen hepatotoxicity induced by TCPOBOP, whereas mutant mice deficient in SRC-1 or SRC-2 exhibited severe acetaminophen hepatotoxicity similar to wild-type controls. Accordingly, deficiency in SRC-3, but not SRC-1 or SRC-2, resulted in a reduced CAR-mediated expression of drug metabolism-related genes in the liver.

Conclusions: Our study demonstrates that SRC-3 is the predominant transcriptional co-activator among the three SRC family members for CAR activation to promote hepatocyte proliferation and drug metabolism.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetaminophen / toxicity
  • Animals
  • Cell Proliferation
  • Constitutive Androstane Receptor
  • Gene Expression
  • Hepatocytes / cytology*
  • Hepatocytes / metabolism*
  • Hyperplasia
  • Liver / drug effects
  • Liver / metabolism
  • Liver / pathology
  • Male
  • Mice
  • Mice, 129 Strain
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Nuclear Receptor Coactivator 1 / deficiency
  • Nuclear Receptor Coactivator 1 / genetics
  • Nuclear Receptor Coactivator 1 / metabolism
  • Nuclear Receptor Coactivator 2 / deficiency
  • Nuclear Receptor Coactivator 2 / genetics
  • Nuclear Receptor Coactivator 2 / metabolism
  • Nuclear Receptor Coactivator 3 / deficiency
  • Nuclear Receptor Coactivator 3 / genetics
  • Nuclear Receptor Coactivator 3 / metabolism*
  • Pyridines / toxicity
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Xenobiotics / metabolism


  • Constitutive Androstane Receptor
  • Nuclear Receptor Coactivator 2
  • Pyridines
  • Receptors, Cytoplasmic and Nuclear
  • Xenobiotics
  • Acetaminophen
  • 1,4-bis(2-(3,5-dichloropyridyloxy))benzene
  • Ncoa1 protein, mouse
  • Ncoa3 protein, mouse
  • Nuclear Receptor Coactivator 1
  • Nuclear Receptor Coactivator 3