The PKC and ERK/MAPK pathways regulate glucocorticoid action on TRH transcription
The PKC and ERK/MAPK pathways regulate glucocorticoid action on TRH transcription
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DOI：
10.1007/s11064-008-9698-5
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发表时间：
2008-08-01
影响因子：
4.4
通讯作者：
Joseph-Bravo, Patricia
中科院分区：
文献类型：
--
作者：
Cote-Velez, Antonieta;Perez-Martinez, Leonor;Joseph-Bravo, Patricia
TRH是一种参与能量平衡的神经肽，其生物合成受糖皮质激素的调节。当下丘脑细胞与地塞米松或cAMP类似物孵育时，TRH mRNA和多肽水平增加，但当两者结合时，观察到相互拮抗。这些影响是在转录水平上观察到的，以及糖皮质激素受体(GR)或pCREB与TRH启动子的GRE(CGRE)和Cre-2复合位点的结合。本工作在下丘脑细胞培养中研究了PKC和MAPK通路参与地塞米松的作用及其与cAMP信号的相互作用。抑制PKC或MEK可阻断地塞米松对TRH mRNA水平的刺激作用及其对8BR-cAMP刺激作用的干扰。经地塞米松或8BrcAMP刺激的下丘脑或神经母细胞瘤细胞的核提取物与含有TRH基因启动子Cre或cGRE位点的寡核苷酸的结合在PKC或MEK抑制剂预先孵育时减少。CGRE的AP-1或GRE半区突变显示GR以异源二聚体的形式与cGRE结合，而PKC或MEK抑制剂减少了AP-1位点的结合。因此，PKC和ERK信号调节GR的活性及其与TRH基因启动子上的CREB或AP-1的相互作用。
Biosynthesis of TRH, a neuropeptide involved in energy homeostasis, is modulated by glucocorticoids. TRH mRNA and peptide levels are increased upon incubation of hypothalamic cells with dexamethasone or with cAMP analogs but when combined, a mutual antagonism is observed. These effects are observed at the transcriptional level and on binding of glucocorticoid receptor (GR) or pCREB to the composite GRE (cGRE) and CRE-2 sites of TRH promoter. The present work studied the involvement of PKC and MAPK pathways on the effect of dexamethasone and on its interaction with cAMP signaling in hypothalamic cell cultures. PKC or MEK inhibition abolished dexamethasone-stimulatory effect on TRH mRNA levels, as well as its interference with the stimulatory effect of 8Br-cAMP. Binding of nuclear extracts from hypothalamic or neuroblastoma cells stimulated with dexamethasone or 8Br-cAMP to oligonucleotides containing the CRE or cGRE sites of TRH gene promoter was decreased if cells were preincubated with PKC or MEK inhibitors. Mutations on the AP-1 or the GRE half sites of cGRE showed that GR binds as an heterodimer on cGRE, and PKC or MEK inhibitors diminish binding at the AP-1 site. PKC and ERK signaling thus modulate GR activity and its interaction with CREB or AP-1 at the TRH gene promoter.