Retinoic acid receptor-α up-regulates proopiomelanocortin gene expression in AtT20 corticotroph cells.
Retinoic acid receptor-α up-regulates proopiomelanocortin gene expression in AtT20 corticotroph cells.
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DOI：
10.1507/endocrj.ej14-0115
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发表时间：
2014
影响因子：
2
通讯作者：
A. Uruno;Akiko Saito-hakoda;A. Yokoyama;N. Kogure;K. Matsuda;R. Parvin;K. Shimizu;I. Sato;M. Kudo;T. Yoshikawa;H. Kagechika;Y. Iwasaki;S. Ito;A. Sugawara
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文献类型：
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作者：
A. Uruno;Akiko Saito-hakoda;A. Yokoyama;N. Kogure;K. Matsuda;R. Parvin;K. Shimizu;I. Sato;M. Kudo;T. Yoshikawa;H. Kagechika;Y. Iwasaki;S. Ito;A. Sugawara
库欣病是一种由垂体促皮质性肿瘤ACTH分泌过多引起的疾病。虽然其标准治疗方法是经蝶窦手术，但迫切需要创新新的医学治疗方法。维甲酸（RA）已被报道抑制库欣病促肾上腺皮质激素（ACTH）分泌。然而，RA受体（RAR）在促黑素皮质素（Pomc）基因表达中的作用仍不确定。我们在此使用AtT20促皮质细胞研究了RARα在Pomc调控中的作用。令人惊讶的是，合成的RARα激动剂Am80增加了Pomc mRNA表达、crh诱导的ACTH分泌和Pomc启动子活性。小干扰rna介导的rar α-敲低抑制了基础和am80诱导的Pomc启动子活性。rar α-过表达剂量依赖性地增加Pomc启动子活性。Pomc启动子突变分析显示，Tpit和NeuroD1结合元件都与am80介导的作用有关。Am80增加Tpit的表达，而RAR拮抗剂LE540抑制其表达。tpit过表达增加了Pomc启动子活性。哺乳动物双杂交实验显示，Am80诱导神经d1 - rar α相互作用。NeuroD1过表达增强了am80诱导的Pomc启动子活性，而这种活性被截断的突变体过表达抑制。RARα通过与NeuroD1的相互作用和Tpit表达的增加，正向调节ACTH分泌/Pomc基因的表达。目前的观察结果将有助于RA/类维甲酸衍生治疗疾病的未来发展。
Cushing's disease is a disorder caused by excessive ACTH secretion from a corticotroph tumor of the pituitary gland. Although its standard therapy is a transsphenoidal surgery, innovation of novel medical treatments for the disease is urgently necessary. Retinoic acid (RA) has been reported to suppress adrenocorticotropic hormone (ACTH) secretion in Cushing's disease. However, the role of RA receptor (RAR) in proopiomelanocortin (Pomc) gene expression remains uncertain. We here examined the involvement of RARα in Pomc regulation using AtT20 corticotroph cells. Surprisingly, a synthetic RARα agonist Am80 increased Pomc mRNA expression, CRH-induced ACTH secretion, and Pomc promoter activity. Small interfering RNA-mediated RARα-knockdown suppressed both basal and Am80-induced Pomc promoter activity. RARα-overexpression dose-dependently increased Pomc promoter activity. Pomc promoter mutation analysis revealed that both Tpit and NeuroD1 binding elements were responsible for the Am80-mediated effect. Am80 increased Tpit expression while RAR antagonist LE540 suppressed the increase. Tpit-overexpression increased Pomc promoter activity. Mammalian two-hybrid assay revealed that Am80 induced NeuroD1-RARα interaction. NeuroD1-overexpression enhanced the Am80-induced Pomc promoter activity, which was suppressed by NeuroD1 truncated mutant-overexpression. RARα thus positively regulates ACTH secretion/Pomc gene expression through interaction with NeuroD1 and Tpit expression increase. The present observation will be useful for the future development of the RA/retinoid-derived therapeutics of the disease.