Chen Alon, Vaughan Joan, Vale Wylie W
Clayton Foundation Laboratories for Peptide Biology, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
Mol Endocrinol. 2003 Aug;17(8):1622-39. doi: 10.1210/me.2003-0054. Epub 2003 May 22.
Peptides encoded by the urocortin II (Ucn II) gene were recently identified as new members of the corticotropin-releasing factor (CRF) family. Ucn II is a specific ligand for the type 2 CRF receptor. Using RT-PCR, DNA sequencing, and immunofluorescence staining, we report the expression of Ucn II mRNA in several human and mouse (m) neuronal cell lines. Using these neuronal cell lines, we provide evidence that exposure to glucocorticoid hormones increases mUcn II mRNA expression and promoter activation. The effect of glucocorticoids on mUcn II mRNA expression was tested in the Ucn II/glucocorticoid receptor-positive cell line NG108-15. The results demonstrate that mUcn II mRNA expression is up-regulated by dexamethasone in a dose- and time-dependent fashion. Computer analysis revealed the presence of 14 putative half-palindrome glucocorticoid response element sequences within 1.2 kb of the mUcn II 5' flanking region. Transfections with different fragments of the 5'-flanking region of the mUcn II gene fused to a luciferase reporter gene showed a promoter-dependent expression of the reporter gene and regulation by dexamethasone. Promoter deletion studies clarify the sufficient putative glucocorticoid response element site mediating this effect. The steroid hormone antagonist RU486 blocked the effect of dexamethasone on mUcn II mRNA expression and promoter activation, suggesting a direct glucocorticoid receptor-mediated effect of dexamethasone on mUcn II mRNA expression. Ucn II is expressed in vivo in the hypothalamus, brainstem, olfactory bulb, and pituitary. Low levels were also detected in the mouse cortex, hippocampus, and spinal cord. We demonstrated that mUcn II gene transcription was stimulated by glucocorticoid administration in vivo and inhibited by removal of glucocorticoids by adrenalectomy. Administration of dexamethasone to mice resulted in an increase of mUcn II levels in the hypothalamus and brainstem but not in the olfactory bulb region 12 h following ip injection. In light of our present data and the current literature, we propose a putative link between the CRF receptor 1 and CRF receptor 2 pathways.
尿皮质素II（Ucn II）基因编码的肽最近被鉴定为促肾上腺皮质激素释放因子（CRF）家族的新成员。Ucn II是2型CRF受体的特异性配体。我们运用逆转录聚合酶链反应（RT-PCR）、DNA测序和免疫荧光染色技术，报告了Ucn II mRNA在多种人类和小鼠神经元细胞系中的表达情况。利用这些神经元细胞系，我们提供了证据表明，暴露于糖皮质激素会增加小鼠Ucn II mRNA的表达及启动子激活。在Ucn II/糖皮质激素受体阳性细胞系NG108-15中测试了糖皮质激素对小鼠Ucn II mRNA表达的影响。结果表明，地塞米松以剂量和时间依赖性方式上调小鼠Ucn II mRNA的表达。计算机分析显示，在小鼠Ucn II 5'侧翼区域的1.2 kb范围内存在14个推定的半回文糖皮质激素反应元件序列。用与荧光素酶报告基因融合的小鼠Ucn II基因5'侧翼区域的不同片段进行转染，显示报告基因的启动子依赖性表达以及受地塞米松调控。启动子缺失研究明确了介导此效应的足够的推定糖皮质激素反应元件位点。类固醇激素拮抗剂RU486阻断了地塞米松对小鼠Ucn II mRNA表达和启动子激活的作用，表明地塞米松对小鼠Ucn II mRNA表达有直接的糖皮质激素受体介导的效应。Ucn II在体内表达于下丘脑、脑干、嗅球和垂体。在小鼠皮质、海马和脊髓中也检测到低水平表达。我们证明，体内给予糖皮质激素可刺激小鼠Ucn II基因转录，而肾上腺切除术去除糖皮质激素则会抑制其转录。给小鼠腹腔注射地塞米松12小时后，下丘脑和脑干中的小鼠Ucn II水平升高，但嗅球区域未升高。根据我们目前的数据和现有文献，我们提出CRF受体1和CRF受体2途径之间存在推定联系。
