Sukhbaatar Unurjargal, Mijiddorj Tselmeg, Oride Aki, Kanasaki Haruhiko
Department of Obstetrics and Gynecology, Shimane University School of Medicine, 89-1 Enya, Izumo City, Shimane Prefecture, 693-8501, Japan.
Endocrine. 2015 May;49(1):222-30. doi: 10.1007/s12020-014-0464-y. Epub 2014 Oct 30.
Acting via ionotropic GABAA receptors, the neurotransmitter γ-aminobutyric acid (GABA) is an important modulator of gonadotropin-releasing hormone (GnRH) neurons. In the present study, we examined the effect of DS1, a GABAA α4β3δ receptor agonist, on a strain of mouse hypothalamic immortalized GnRH neuronal cells, the GT1-7 cell line. DS1 increased the activities of serum-response element (SRE) and cAMP-response element (CRE) promoters, which reflect the activities of extracellular signal-regulated kinase and cAMP/protein kinase A (PKA) pathways, respectively. In G protein-coupled receptor 54 (GPR54)-overexpressing GT1-7 cells, both DS1 and kisspeptin-10 stimulated SRE promoter activity, and combined treatment with DS1 and kisspeptin further increased SRE promoter activity compared with DS1 or kisspeptin alone. Pituitary adenylate cyclase-activating polypeptide (PACAP) increased CRE promoter activity in PACAP type I receptor-overexpressing GT1-7 cells, with an effect similar to that of DS1 alone, and combined stimulation with PACAP and DS1 potentiated their individual effects. DS1 stimulated the transcriptional activity of GnRH receptor, and DS1 induced GnRH receptor mRNA and protein expression. PACAP-increased GnRH receptor expression was enhanced in the presence of DS1. However, DS1 significantly inhibited the basal expression of GnRH mRNA in GT1-7 cells. Our current observations suggest that DS1 exerts its stimulatory effect on the intracellular signal transduction system via GABAA α4β3δ receptors in GnRH-producing neurons. Stimulation with DS1 increased the expression of GnRH receptor but decreased the basal expression of GnRH mRNA.
神经递质γ-氨基丁酸（GABA）通过离子型GABAA受体发挥作用，是促性腺激素释放激素（GnRH）神经元的重要调节因子。在本研究中，我们检测了GABAA α4β3δ受体激动剂DS1对小鼠下丘脑永生化GnRH神经元细胞系GT1-7细胞的作用。DS1增加了血清反应元件（SRE）和环磷酸腺苷反应元件（CRE）启动子的活性，这分别反映了细胞外信号调节激酶和环磷酸腺苷/蛋白激酶A（PKA）信号通路的活性。在过表达G蛋白偶联受体54（GPR54）的GT1-7细胞中，DS1和 kisspeptin-10均刺激了SRE启动子活性，与单独使用DS1或kisspeptin相比，DS1与kisspeptin联合处理进一步增加了SRE启动子活性。垂体腺苷酸环化酶激活多肽（PACAP）在过表达PACAP I型受体的GT1-7细胞中增加了CRE启动子活性，其作用与单独使用DS1相似，PACAP与DS1联合刺激增强了它们各自的作用。DS1刺激了GnRH受体的转录活性，并诱导了GnRH受体mRNA和蛋白表达。在存在DS1的情况下，PACAP增加的GnRH受体表达增强。然而，DS1显著抑制了GT1-7细胞中GnRH mRNA的基础表达。我们目前的观察结果表明，DS1通过GnRH产生神经元中的GABAA α4β3δ受体对细胞内信号转导系统发挥刺激作用。用DS1刺激增加了GnRH受体的表达，但降低了GnRH mRNA的基础表达。
