PPP1R16A, the membrane subunit of protein phosphatase 1β, signals nuclear translocation of the nuclear receptor constitutive active/androstane receptor
PPP1R16A, the membrane subunit of protein phosphatase 1β, signals nuclear translocation of the nuclear receptor constitutive active/androstane receptor
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DOI：
10.1124/mol.107.042960
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发表时间：
2008-04-01
影响因子：
3.6
通讯作者：
Negishi, Masahiko
中科院分区：
文献类型：
--
作者：
Sueyoshi, Tatsuya;Moore, Rick;Negishi, Masahiko
组成型活性/雄烷受体（CAR）是核类固醇/甲状腺激素受体家族的成员，在暴露于治疗药物和环境污染物时激活许多肝脏基因的转录。这种受体被隔离在细胞质中，通过移位到细胞核中来发出外源性暴露的信号，例如苯巴比妥（PB）。与其他激素受体不同，易位可以间接触发而不与外源性物质结合。我们现在已经确定了蛋白磷酸酶1的膜相关亚基（PPP 1 R16 A，或缩写为R16 A）作为一种新的CAR结合蛋白。当CAR和R16 A在小鼠肝脏中共表达时，CAR易位到细胞核中。使用表达的黄色荧光蛋白（YFP）-CAR和CFP-R16 A融合蛋白，通过荧光共振能量转移（FRET）分析显示R16 A和CAR分子在肝膜上的紧密结合。R16 A可以通过其中间区域形成二聚体，最近在该区域发现了蛋白激酶A磷酸化位点。CAR通过R16 A的易位与R16 A经由中间区域形成分子间相互作用的能力相关。此外，PB处理增强了小鼠肝脏中的这种相互作用。R16 A特异性地与HepG 2细胞中的PP 1 β相互作用，尽管PP 1家族分子的结构高度保守。R16 A在体外抑制PP 1 β活性，PP 1 β在肝脏中的共表达可以阻止YFP-CAR易位到小鼠肝脏中。总之，膜上的R16 A可以介导PB信号以启动CAR核转位，通过包括其二聚化和抑制PP 1 β活性的机制，为核受体转位提供了一种新的模型，其中配体和受体的直接相互作用可能不是至关重要的。
Constitutive active/androstane receptor (CAR), a member of the nuclear steroid/thyroid hormone receptor family, activates transcription of numerous hepatic genes upon exposure to therapeutic drugs and environmental pollutants. Sequestered in the cytoplasm, this receptor signals xenobiotic exposure, such as phenobarbital (PB), by translocating into the nucleus. Unlike other hormone receptors, translocation can be triggered indirectly without binding to xenobiotics. We have now identified a membrane-associated subunit of protein phosphatase 1 (PPP1R16A, or abbreviated as R16A) as a novel CAR-binding protein. When CAR and R16A are coexpressed in mouse liver, CAR translocates into the nucleus. Close association of R16A and CAR molecule on liver membrane was shown by fluorescence resonance energy transfer (FRET) analysis using expressed yellow fluorescent protein (YFP)-CAR and CFP-R16A fusion proteins. R16A can form dimer through its middle region, where protein kinase A phosphorylation sites are recently identified. Translocation of CAR by R16A correlates with the ability of R16A to form an intermolecular interaction via the middle region. Moreover, this interaction is enhanced by PB treatment in mouse liver. R16A specifically interacted with PP1 beta in HepG2 cells despite the highly conserved structure of PP1 family molecules. PP1 beta activity was inhibited by R16A in vitro and coexpression of PP1 beta in liver can prevent YFP-CAR translocation into mouse liver. Taken together, R16A at the membrane may mediate the PB signal to initiate CAR nuclear translocation, through a mechanism including its dimerization and inhibition of PP1 beta activity, providing a novel model for the translocation of nuclear receptors in which direct interaction of ligands and the receptors may not be crucial.