Serine 202 regulates the nuclear translocation of constitutive active/androstane receptor

Mol Pharmacol. 2006 Apr;69(4):1095-102. doi: 10.1124/mol.105.019505. Epub 2005 Dec 23.

Abstract

The constitutive active receptor (CAR) in mouse primary hepatocytes undergoes okadaic acid (OA)-sensitive nuclear translocation after activation by xenobiotics such as phenobarbital (PB) and 1,4 bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP). We have now mimicked this TCPOBOP-dependent and OA-sensitive translocation of mouse CAR (mCAR) in HepG2 cells and have demonstrated that protein phosphatase 2A regulates this nuclear translocation. Site-directed mutagenesis analysis of various Ser and Thr residues delineated the translocation activity to Ser-202. Mutation of Ser-202 to Asp (S202D) prevented mCAR translocation into the nucleus of TCPOBOP-treated HepG2 cells. In addition, in the livers of Car-/- mice, the YFP-tagged S202D mutant did not translocate into the nucleus after PB treatment. To examine whether Ser-202 can be phosphorylated, flag-tagged wild-type mCAR or flag-tagged S202A mutant was expressed in HepG2 cells and subjected to Western blot analysis using an antibody specific to a peptide containing phospho-Ser-202. A high molecular weight phosphorylated form of CAR was detected only with the wild-type mCAR. These results are consistent with the conclusion that the dephosphorylation of Ser-202 is a required step that regulates the xenobiotic-dependent nuclear translocation of mCAR.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Cell Nucleus / metabolism*
  • Mice
  • Molecular Sequence Data
  • Phenobarbital / pharmacology
  • Phosphorylation
  • Protein Transport
  • Pyridines / pharmacology
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Sequence Homology, Amino Acid
  • Serine / metabolism
  • Transcription Factors / metabolism*

Substances

  • Pyridines
  • Receptors, Cytoplasmic and Nuclear
  • Transcription Factors
  • constitutive androstane receptor
  • Serine
  • 1,4-bis(2-(3,5-dichloropyridyloxy))benzene
  • Phenobarbital