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Serine‐202 regulates the nuclear translocation of constitutive active/androstane receptor CAR
Author(s) -
Hosseinpour Fardin,
Moore Rick,
Negishi Masahiko,
Sueyoshi Tatsuya
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a261-b
Subject(s) - chromosomal translocation , constitutive androstane receptor , chemistry , dephosphorylation , microbiology and biotechnology , phosphorylation , mutant , phosphatase , biochemistry , biology , nuclear receptor , gene , transcription factor
The constitutive active receptor CAR in mouse primary hepatocytes undergoes okadaic acid (OA)‐sensitive nuclear translocation following 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 Ser202. Mutation of Ser202 to Asp (S202D) prevented mCAR translocation into the nucleus of TCPOBOP‐treated HepG2 cells. Also, 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. This work has been supported by NIEHS Intramural Research Program.