title: Active ERK1/2 protein interacts with the phosphorylated nuclear constitutive active/androstane receptor (CAR; NR1I3), repressing dephosphorylation and sequestering CAR in the cytoplasm.
abstract: The nuclear constitutive active/androstane receptor (CAR) is inactivated and sequestered in the cytoplasm when Thr-38 is phosphorylated. Here, we have demonstrated that activated ERK1/2 interacts with phosphorylated CAR to repress dephosphorylation of Thr-38. The phosphorylation-dependent interaction between CAR and ERK1/2 was examined by co-immunoprecipitation experiments of ectopically expressed FLAG-tagged CAR T38A and CAR T38D mutants with endogenous phospho-ERK1/2 in Huh-7 cells. Phospho-ERK1/2 coprecipitated only the phosphorylation-mimicking CAR T38D mutant; this coprecipitation was mediated by the interaction with the xenochemical response signal peptide near the C terminus of CAR. This interaction increased after EGF treatment and decreased after treatment with the MEK inhibitor U0126 as well as after knockdown of MEK1/2 by shRNA in Huh-7 cells. The phosphorylation levels of Thr-38 of CAR decreased in U0126-treated Huh-7 cells. Thus, activated ERK1/2 interacts with CAR and represses dephosphorylation of Thr-38, providing a cell signal-regulated mechanism for CAR activation.
authors.affiliation: Pharmacogenetics Section, Laboratory of Reproductive and Developmental Toxicology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709.
authors.forename: Makoto
authors.initials: M
authors.lastname: Osabe
authors.affiliation: Pharmacogenetics Section, Laboratory of Reproductive and Developmental Toxicology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709. Electronic address: negishi@niehs.nih.gov.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Negishi
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D000090702:Constitutive Androstane Receptor; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D021382:Protein Sorting Signals / Q000502:physiology; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*
chemical_list: D002070:Butadienes; D000090702:Constitutive Androstane Receptor; D004791:Enzyme Inhibitors; C000716327:NR1I3 protein, human; D009570:Nitriles; C000716328:Nr1i3 protein, mouse; D021382:Protein Sorting Signals; D018160:Receptors, Cytoplasmic and Nuclear; C113580:U 0126; C482128:MAP2K2 protein, human; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; C482127:Map2k1 protein, mouse; C482129:Map2k2 protein, mouse