Phosphorylated Nuclear Receptor CAR Forms a Homodimer To Repress Its Constitutive Activity for Ligand Activation
| Autor: | Lalith Perera, Makoto Osabe, Tatsuya Sueyoshi, Rick Moore, Masahiko Negishi, Ryota Shizu |
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| Rok vydání: | 2017 |
| Předmět: |
Male
0301 basic medicine Receptors Cytoplasmic and Nuclear Mice Transgenic Biology Ligands Receptors for Activated C Kinase Dephosphorylation Mice 03 medical and health sciences Epidermal growth factor Constitutive androstane receptor Animals Humans Protein phosphorylation Protein Phosphatase 2 Phosphorylation Protein kinase A Molecular Biology Cells Cultured Constitutive Androstane Receptor Mice Knockout Mice Inbred C3H Epidermal Growth Factor Neuropeptides Cell Biology Protein phosphatase 2 Cell biology ErbB Receptors Mice Inbred C57BL 030104 developmental biology Gene Expression Regulation Biochemistry Nuclear receptor Hepatocytes Protein Multimerization human activities Research Article |
| Zdroj: | Molecular and Cellular Biology. 37 |
| ISSN: | 1098-5549 |
| DOI: | 10.1128/mcb.00649-16 |
| Popis: | The nuclear receptor CAR (NR1I3) regulates hepatic drug and energy metabolism as well as cell fate. Its activation can be a critical factor in drug-induced toxicity and the development of diseases, including diabetes and tumors. CAR inactivates its constitutive activity by phosphorylation at threonine 38. Utilizing receptor for protein kinase 1 (RACK1) as the regulatory subunit, protein phosphatase 2A (PP2A) dephosphorylates threonine 38 to activate CAR. Here we demonstrate that CAR undergoes homodimer-monomer conversion to regulate this dephosphorylation. By coexpression of two differently tagged CAR proteins in Huh-7 cells, mouse primary hepatocytes, and mouse livers, coimmunoprecipitation and two-dimensional gel electrophoresis revealed that CAR can form a homodimer in a configuration in which the PP2A/RACK1 binding site is buried within its dimer interface. Epidermal growth factor (EGF) was found to stimulate CAR homodimerization, thus constraining CAR in its inactive form. The agonistic ligand CITCO binds directly to the CAR homodimer and dissociates phosphorylated CAR into its monomers, exposing the PP2A/RACK1 binding site for dephosphorylation. Phenobarbital, which is not a CAR ligand, binds the EGF receptor, reversing the EGF signal to monomerize CAR for its indirect activation. Thus, the homodimer-monomer conversion is the underlying molecular mechanism that regulates CAR activation, by placing phosphorylated threonine 38 as the common target for both direct and indirect activation of CAR. |
| Databáze: | OpenAIRE |
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