Cytoplasmic accumulation of the nuclear receptor CAR by a tetratricopeptide repeat protein in HepG2 cells
Cytoplasmic accumulation of the nuclear receptor CAR by a tetratricopeptide repeat protein in HepG2 cells
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DOI：
10.1124/mol.64.5.1069
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发表时间：
2003-11-01
影响因子：
3.6
通讯作者：
Negishi, M
中科院分区：
文献类型：
--
作者：
Kobayashi, K;Sueyoshi, T;Negishi, M
核组成型活性受体（CAR）是一种关键的转录因子，调节苯巴比妥（PB）诱导的各种肝脏基因的转录，这些基因编码外源性/类固醇代谢酶。CAR保留在未诱导的肝脏的细胞质中，并在PB诱导后易位到细胞核中（Mol Cell Biol 19：6318-6322，1999）。HepG 2细胞缺乏将CAR保留在细胞质中的能力;因此，受体自发地在细胞核中积累。我们现在已经克隆并表征了一种三肽重复序列（TPR）蛋白，命名为细胞质CAR保留蛋白（CCRP），其能够在共转染的HepG 2细胞的细胞质中积累受体。CCRP直接与CAR的配体结合结构域相互作用，并介导细胞质CAR-CCRP-90-kDa热休克蛋白（hsp 90）三元复合物的形成。荧光蛋白标记的CAR和CCRP的同时表达揭示了它们在体内与小鼠肝脏中的微管蛋白共定位。因此，这些结果表明CCRP可能是CAR-hsp 90复合物的组分，并参与将受体保留在HepG 2细胞和可能的体内肝细胞的细胞质中。
The nuclear constitutive active receptor (CAR) is a key transcription factor regulating phenobarbital (PB)-inducible transcription of various hepatic genes that encode xenobiotic/steroid-metabolizing enzymes. CAR is retained in the cytoplasm of noninduced livers and translocates into the nucleus after PB induction (Mol Cell Biol 19:6318-6322, 1999). HepG2 cells lack the capability of retaining CAR in the cytoplasm; thus, the receptor spontaneously accumulates in the nucleus. We have now cloned and characterized a tetratricopeptide repeat (TPR) protein, designated cytoplasmic CAR retention protein (CCRP), for its ability to accumulate the receptor in the cytoplasm of cotransfected HepG2 cells. CCRP directly interacts with the ligand-binding domain of CAR and mediates the formation of a cytoplasmic CAR-CCRP-90-kDa heat shock protein (hsp90) ternary complex. Simultaneous expression of fluorescent protein-tagged CAR and CCRP reveals their colocalization with tubulin in mouse liver in vivo. Thus, these results indicate that CCRP may be a component of the CAR-hsp90 complex and involved in retaining the receptor in the cytoplasm of both HepG2 cells and probably in vivo liver cells.