Novel role for the nuclear phosphoprotein SET in transcriptional activation of P450c17 and initiation of neurosteroidogenesis
Novel role for the nuclear phosphoprotein SET in transcriptional activation of P450c17 and initiation of neurosteroidogenesis
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DOI：
10.1210/me.14.6.875
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发表时间：
2000-06-01
影响因子：
--
通讯作者：
Mellon, SH
中科院分区：
文献类型：
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作者：
Compagnone, NA;Zhang, P;Mellon, SH
神经类固醇是γ-氨基丁酸(GABA(A))和N-甲基-D-天冬氨酸(NMDA)受体的重要内源性调节因子，也影响神经元的形态和功能。神经类固醇是在大脑中使用肾上腺和性腺中发现的许多相同的酶来产生的。在脑中合成脱氢表雄酮的关键酶是细胞色素P450c17，其转录策略在脑中的表达明显不同于在肾上腺或性腺中的表达。我们之前从LeydigMA-10细胞中鉴定了一种新的转录调控因子，称为STF-IT-1，它与已知的转录因子Coup-TF(鸡卵蛋白上游启动子转录因子)、NGF-IB(神经生长因子诱导蛋白B)和SF-1(类固醇生成因子-1)结合在大鼠P450c17启动子的-447/-399碱基上。我们现在已经从未成熟的猪睾丸中纯化并测序了这个蛋白，鉴定它是核磷蛋白SET；SET在转录中的作用以前没有确定。细菌表达的人和大鼠SET结合到大鼠P450c17基因-418/-399的DNA位点上，可以反式激活神经元和睾丸间质细胞中的P450c17。我们还发现SET在人NT2神经前体细胞中表达，这可能与神经类固醇的生成有关。小鼠胚胎的免疫细胞化学和原位杂交表明，SET在发育中的神经系统中的个体发生和分布与SET是启动P450c17转录的关键是一致的。SET的发育表达模式表明，它可能参与了神经以及骨骼和造血系统的早期个体发生。这些研究描述了P450c17转录调控的一个重要新因素，从而在脱氢表雄酮和性类固醇的产生中。
Neurosteroids are important endogenous regulators of gamma-aminobutryic acid (GABA(A)) and N-methyl-D-aspartate (NMDA) receptors and also influence neuronal morphology and function. Neurosteroids are produced in the brain using many of the same enzymes found in the adrenal and gonad. The crucial enzyme for the synthesis of DHEA (dehydroepiandrosterone) in the brain is cytochrome P450c17, The transcriptional strategy for the expression of P450c17 is clearly different in the brain from that in the adrenal or gonad. We previously characterized a novel transcriptional regulator from Leydig MA-10 cells, termed StF-IT-1, that binds at bases -447/-399 of the rat P450c17 promoter, along with the known transcription factors COUP-TF (chicken ovalbumin upstream promoter transcription factor), NGF-IB (nerve growth factor inducible protein B), and SF-1 (steroidogenic factor-1). We have now purified and sequenced this protein from immature porcine testes, identifying it as the nuclear phosphoprotein SET; a role for SET in transcription was not established previously. Binding of bacterially expressed human and rat SET to the DNA site at -418/-399 of the rat P450c17 gene transactivates P450c17 in neuronal and in testicular Leydig cells. We also found SET expressed in human NT2 neuronal precursor cells, implicating a role in neurosteroidogenesis. Immunocytochemistry and in situ hybridization in the mouse fetus show that the ontogeny and distribution of SET in the developing nervous system are consistent with SET being crucial for initiating P450c17 transcription. SET's developmental pattern of expression suggests it may participate in the early ontogenesis of the nervous, as well as the skeletal and hematopoietic, systems. These studies delineate an important new factor in the transcriptional regulation of P450c17 and consequently, in the production of DHEA and sex steroids.