DIFFERENTIAL SELENIUM-DEPENDENT EXPRESSION OF TYPE-I 5'-DEIODINASE AND GLUTATHIONE-PEROXIDASE IN THE PORCINE EPITHELIAL KIDNEY-CELL LINE LLC-PK1
DIFFERENTIAL SELENIUM-DEPENDENT EXPRESSION OF TYPE-I 5'-DEIODINASE AND GLUTATHIONE-PEROXIDASE IN THE PORCINE EPITHELIAL KIDNEY-CELL LINE LLC-PK1
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DOI：
10.1042/bj3060851
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发表时间：
1995-03-15
影响因子：
4.1
通讯作者：
KOHRLE, J
中科院分区：
文献类型：
--
作者：
GROSS, M;OERTEL, M;KOHRLE, J
研究了无血清培养条件下猪肾上皮细胞株LLC-PK 1中两种含硒蛋白--细胞内谷胱甘肽过氧化物酶（cGPx）和I型碘甲腺原氨酸-5 '-脱碘酶（5' DI）的表达。通过酶活性测定、5 'DI亲和标记、Se-75蛋白质代谢标记和稳态mRNA分析揭示了cGPx和5' DI的亚硒酸盐依赖性表达。这两种酶的表达强烈依赖于培养基中的亚硒酸盐浓度。cGPx需要比5 'DI高2倍的亚硒酸盐水平才能达到半最大活性。硒依赖性酶活性与相应的稳态mRNA水平近似平行。这两种酶对硒供应的反应进一步表征了动力学硒耗尽和-repletion实验。在去除培养基亚硒酸盐后，cGPx活性呈指数下降，而在1-2天的初始下降后，5 'DI水平在另外2天内完全恢复。这些数据表明，一个差分硒依赖性调节的两种硒蛋白，与5 'DI被优先提供的微量元素硒，从而确保连续的细胞能力，甲状腺激素激活，即使在硒缺乏的条件下。在硒供应充足的细胞中，丰富的cGPx可能作为细胞硒库，在缺硒条件下可被动员用于合成更重要的硒蛋白，如5 'DI。因此，硒蛋白表达的细胞层次结构，反映了不同的个人在转录和转录后水平的调节机制，增加了以前公认的组织特异性层次结构的硒保留。
The Se-dependent expression of two selenoproteins, cytosolic glutathione peroxidase (cGPx) and type I iodothyronine-5'-deiodinase (5'DI), was investigated in the porcine epithelial kidney cell line LLC-PK1 in serum-free medium. The selenite-dependent expression of cGPx and 5'DI was revealed by enzyme-activity measurements, affinity labelling of 5'DI, metabolic labelling of proteins with Se-75 and steady-state mRNA analysis. The expression of the two enzymes strongly depended on selenite concentrations of the culture medium. cGPx required 2-fold higher selenite levels than 5'DI to reach half-maximal activity. The Se-dependent enzyme activities were approximately par alleled by the corresponding steady-state mRNA levels. The response of the two enzymes to Se supply was further characterized by kinetic Se-depletion and -repletion experiments. Upon removal of medium selenite, cGPx activity decreased exponentially, whereas after an initial decrease over 1-2 days, 5'DI levels completely recovered during a further 2 days. These data indicate a differential Se-dependent regulation of the two selenoproteins, with 5'DI being preferentially supplied with the trace element Se, thus ensuring a continuous cellular capacity for thyroid-hormone activation, even under Se-deficient conditions. The abundant cGPx in cells with sufficient Se supply might serve as a cellular Se store which can be mobilized for the synthesis of more vital selenoproteins such as 5'DI under shortage conditions. Thus, a cellular hierarchy of selenoprotein expression, reflected by different individual regulation mechanisms at the transcriptional and post-transcriptional level, adds to the previously recognized tissue-specific hierarchy of Se retention.