CAR and PXR are members of the NR1I subfamily within the nuclear receptor superfamily. My laboratory was the first to characterize CAR as a drug-activated nuclear receptor, leading world-wide investigations to characterize CAR and PXR and establish their biological roles. Both CAR and PXR regulate not only hepatic drug metabolism and disposition but also energy metabolism such as gluconeogenesis and lipogenesis and ketogenesis. In addition, they regulate cell growth and death signals as well, which includes JNK1, p38MAPK, AKT and GADD45 signals. Consequently, CAR and PXR have now been implicated in various hepatic toxicities and diseases such as liver tumors. It is now known that these receptors act as transcription factors as well as signal transducers in these regulations. However, their molecular mechanisms are not fully understood now. Our work found that CAR is phosphorylated at threonine 38 within the DBD and is inactivated. This phosphorylation is the underlying principle through which CAR functions diverge. For example, phenobarbital stimulates dephosphorization of threonine 38 by protein phosphatase 2A, by binding EGF receptor and/or insulin receptor and repressing their down-stream ERK1/2 signal for CAR activation. In PXR, phosphorylation of serine 350 within the LBD regulates its functions. These phosphorylation motifs within the DBD or LBD are conserved in the majority of nuclear receptors, suggesting that findings with CAR and PXR can be implicated in the investigations of numerous other nuclear receptors Estrogen receptor (ER) conserves threonine 38 of CAR at serine 216 within its DBD. With a phospho-Ser216peptide antibody, it was found that ER is specifically phosphorylated at serine 216 in immune cells such as neutrophils and macrophages in mice. ER KI (Esr1S216A) mice bearing a non-phosphomimetic alanine mutation were generated to investigate the biological roles of this phosphorylation. ER KI mice are fertile but develop obesity. Analysis of brains and microglia and Kupffer cells (resident macrophages in the brain or liver) showed that this phosphorylation confers anti-inflammatory and anti-apoptotic capabilities to ER Phosphorylated ER can be a novel target to investigate various diseases such as obesity and inflammation-related neurodegenerative diseases and their mechanisms. ER KI mice can be an excellent animal model for these investigations. Retinoid related orphan receptor (ROR) conserves this phosphorylation at serine 100 within the DBD. This serine residue becomes phosphorylated in mouse livers in response to phenobarbital treatment, regulating CAR-targeted genes. These nuclear receptors appears to communicate through the conserved phosphorylation, regulating genes and disease developments in response to environmental chemicals and providing an excellent experimental system to investigate the molecular mechanism of this communication. in response to drug treatments and/or physiological/pathophysiological conditions. There are 40 nuclear receptors which conserve this motif with the DBD, enabling us to extend the same line of communication study far beyond these three nuclear receptors.

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34
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2019
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Negishi, Masahiko (2017) Phenobarbital Meets Phosphorylation of Nuclear Receptors. Drug Metab Dispos 45:532-539
Nagase, Hayato; Kudo, Daisuke; Suto, Akiko et al. (2017) 4-Methylumbelliferone Suppresses Hyaluronan Synthesis and Tumor Progression in SCID Mice Intra-abdominally Inoculated With Pancreatic Cancer Cells. Pancreas 46:190-197
Shizu, Ryota; Osabe, Makoto; Perera, Lalith et al. (2017) Phosphorylated Nuclear Receptor CAR Forms a Homodimer To Repress Its Constitutive Activity for Ligand Activation. Mol Cell Biol 37:
Li, Lei; Bao, Xiaochen; Zhang, Qing-Yu et al. (2017) Role of CYP2B in Phenobarbital-Induced Hepatocyte Proliferation in Mice. Drug Metab Dispos 45:977-981
Hori, Takeshi; Moore, Rick; Negishi, Masahiko (2016) p38 MAP Kinase Links CAR Activation and Inactivation in the Nucleus via Phosphorylation at Threonine 38. Drug Metab Dispos 44:871-6
Shindo, Sawako; Moore, Rick; Negishi, Masahiko (2016) Detection and Functional Analysis of Estrogen Receptor ? Phosphorylated at Serine 216 in Mouse Neutrophils. Methods Mol Biol 1366:413-424
Yasujima, Tomoya; Saito, Kosuke; Moore, Rick et al. (2016) Phenobarbital and Insulin Reciprocate Activation of the Nuclear Receptor Constitutive Androstane Receptor through the Insulin Receptor. J Pharmacol Exp Ther 357:367-74
Hashiguchi, Takuyu; Arakawa, Shingo; Takahashi, Shogo et al. (2016) Phosphorylation of Farnesoid X Receptor at Serine 154 Links Ligand Activation With Degradation. Mol Endocrinol 30:1070-1080
Li, Linhao; Li, Haishan; Garzel, Brandy et al. (2015) SLC13A5 is a novel transcriptional target of the pregnane X receptor and sensitizes drug-induced steatosis in human liver. Mol Pharmacol 87:674-82
Gotoh, Saki; Negishi, Masahiko (2015) Statin-activated nuclear receptor PXR promotes SGK2 dephosphorylation by scaffolding PP2C to induce hepatic gluconeogenesis. Sci Rep 5:14076

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