Morte B, Iñiguez M A, Lorenzo P I, Bernal J
Instituto de Investigaciones Biomédicas, CSIC, Madrid, Spain.
J Neurochem. 1997 Sep;69(3):902-9. doi: 10.1046/j.1471-4159.1997.69030902.x.
The calmodulin-binding, protein kinase C substrate RC3/neurogranin is the product of a neuron-specific gene expressed in the forebrain that is under specific regional and temporal control by thyroid hormone (3,5,3'-triiodothyronine, T3). In vivo, some neuronal populations are sensitive and others are insensitive to T3. The goal of this study was to identify neuronal cell cultures that express RC3/neurogranin, to check whether they are sensitive to T3, and to examine the mechanism of regulation. We found that RC3 is induced by T3 in the hypothalamic cell line GT1-7 at the transcriptional level. The half-life of the mature mRNA was 20 h and was not affected by the hormone. Addition of T3 to the cell culture induces neurogranin mRNA after 6 h in the absence of new protein synthesis. These results suggest a direct transcriptional effect of T3 mediated through nuclear receptors. Indeed, GT1-7 cells express functional T3 receptors, as shown by northern blotting, nuclear T3-binding assays, and transactivation of reporter genes. The role of retinoic acid and glucocorticoids on RC3 expression was also evaluated, because we have previously noted the presence of consensus response elements for these hormones in the RC3 upstream promoter region. In contrast to T3, neither retinoic acid nor dexamethasone influences neurogranin expression despite the presence of respective functional receptors.
钙调蛋白结合蛋白激酶C底物RC3/神经颗粒素是一种在大脑前叶表达的神经元特异性基因的产物，该基因受甲状腺激素（3,5,3'-三碘甲状腺原氨酸，T3）的特定区域和时间控制。在体内，一些神经元群体对T3敏感，而另一些则不敏感。本研究的目的是鉴定表达RC3/神经颗粒素的神经元细胞培养物，检查它们是否对T3敏感，并研究其调节机制。我们发现，在转录水平上，T3可诱导下丘脑细胞系GT1-7中的RC3表达。成熟mRNA的半衰期为20小时，不受该激素影响。在细胞培养物中添加T3后6小时，在没有新蛋白质合成的情况下可诱导神经颗粒素mRNA表达。这些结果表明T3通过核受体介导直接转录作用。事实上，如Northern印迹、核T3结合测定和报告基因的反式激活所示，GT1-7细胞表达功能性T3受体。我们还评估了视黄酸和糖皮质激素对RC3表达的作用，因为我们之前注意到在RC3上游启动子区域存在这些激素的共有反应元件。与T3不同，尽管存在各自的功能性受体，但视黄酸和地塞米松均不影响神经颗粒素的表达。
