Selmi-Ruby S, Rousset B
Institut National de la Santé et de la Recherche Médicale, U 369, Faculté de Médecine Alexis Carrel, Lyon, France.
Mol Cell Endocrinol. 1996 May 17;119(1):95-104. doi: 10.1016/0303-7207(96)03801-4.
T3 nuclear receptors (TR) are present in thyroid cells. We have analyzed the ability of thyroid TR to function as transcriptional regulators. Studies were performed on pig thyrocytes in primary culture. Messenger RNA corresponding to TR alpha 1, alpha 2 and beta were detected in pig thyrocytes by RT-PCR and Northern blot; the alpha 2 mRNA was more abundant than the alpha 1 mRNA. Thyrocytes were transiently transfected with different plasmids containing the CAT (chloramphenicol acetyl transferase) gene placed under the control of different promoters (delta MTV, TK or delta SV40) and bearing a thyroid hormone response element, TREp or TRE DR + 4. It was found that TSH induced a concentration-dependent increase of the transfection efficiency, an effect reproduced by (Bu)2cAMP and Forskolin. Cells transfected with either delta MTV-, TK- or delta SV40-TREp-CAT expressed similar basal CAT activities. Addition of T3 produced a 3-fold increase of CAT activity expressed from each of these vectors. In contrast, CAT activity expressed from a vector containing the TRE DR + 4 was decreased by about 50% by T3. Thus, TREp and TRE DR + 4 gave distinct responses. These data demonstrate that TR physiologically expressed in thyroid cells can act as transcriptional regulators in a T3-dependent manner. This finding directly substantiates the concept of autocrine regulatory actions of thyroid hormones.
T3核受体（TR）存在于甲状腺细胞中。我们分析了甲状腺TR作为转录调节因子的功能。研究在原代培养的猪甲状腺细胞上进行。通过逆转录聚合酶链反应（RT-PCR）和Northern印迹法在猪甲状腺细胞中检测到了与TRα1、α2和β相对应的信使核糖核酸（mRNA）；α2 mRNA比α1 mRNA更丰富。用不同的质粒对甲状腺细胞进行瞬时转染，这些质粒含有置于不同启动子（δMTV、TK或δSV40）控制下的氯霉素乙酰转移酶（CAT）基因，并带有甲状腺激素反应元件TREp或TRE DR + 4。发现促甲状腺激素（TSH）诱导转染效率呈浓度依赖性增加，该效应可被双丁酰环磷腺苷（Bu）2cAMP和福斯可林重现。用δMTV -、TK -或δSV40 - TREp - CAT转染的细胞表达相似的基础CAT活性。添加T3使从这些载体中的每一个表达的CAT活性增加了3倍。相比之下，T3使含有TRE DR + 4的载体表达的CAT活性降低了约50%。因此，TREp和TRE DR + 4产生了不同的反应。这些数据表明，在甲状腺细胞中生理表达的TR可以以T3依赖的方式作为转录调节因子发挥作用。这一发现直接证实了甲状腺激素自分泌调节作用的概念。
