Mijiddorj Tselmeg, Kanasaki Haruhiko, Sukhbaatar Unurjargal, Oride Aki, Hara Tomomi, Kyo Satoru
Department of Obstetrics and Gynecology, Shimane University Faculty of Medicine, Izumo, Shimane 693-8501, Japan.
Department of Obstetrics and Gynecology, Shimane University Faculty of Medicine, Izumo, Shimane 693-8501, Japan.
Gen Comp Endocrinol. 2017 May 15;246:382-389. doi: 10.1016/j.ygcen.2017.01.014. Epub 2017 Jan 11.
Hypothalamic kisspeptin plays a pivotal role in the regulation of the hypothalamic-pituitary-gonadal axis by stimulating gonadotropin-releasing hormone (GnRH) release into the portal circulation, with the subsequent release of gonadotropins. Kisspeptin and its receptor, the kisspeptin 1 receptor (Kiss1R), are also expressed in the pituitary gland. This study demonstrates the interaction between GnRH and kisspeptin within the pituitary gonadotrophs by altering their individual receptor expression. Our results show that kisspeptin and Kiss1R are expressed in the mouse pituitary gonadotroph cell line LβT2. Endogenous Kiss1R did not respond to kisspeptin and failed to stimulate gonadotropin LHβ and FSHβ expression in LβT2 cells; however, kisspeptin increased both LHβ and FSHβ promoter activity in Kiss1R-overexpressing LβT2 cells. Stimulating the cells with GnRH significantly increased Kiss1R expression, whereas kisspeptin increased the expression of the GnRH receptor (GnRHR) in these cells. Elevating the Kiss1R concentration led to an increase in the basal activities of gonadotropin LHβ- and FSHβ-subunit promoters. In addition, the level of kisspeptin-induced LHβ promoter activity, but not that of FSHβ, was significantly increased when a large number of Kiss1R expression vectors was introduced into the cells. The level of induction of GnRH-induced gonadotropin promoter activities was not significantly changed by increasing Kiss1R expression. Increasing the amount of GnRHR by overexpressing cellular GnRHR did not potentiate basal gonadotropin promoter activities; however, kisspeptin- and GnRH-stimulated increases in gonadotropin promoter activities were significantly potentiated (except GnRH-induced LHβ promoters). The activities of serum response element-containing promoters were also modified in cells overexpressing Kiss1R or GnRHR. Our current observations demonstrate that GnRH and kisspeptin affect each other's function to stimulate gonadotropin subunit gene expression by reciprocally increasing the expression of their receptors.
下丘脑的 kisspeptin 通过刺激促性腺激素释放激素（GnRH）释放进入门脉循环，进而促使促性腺激素的释放，在调节下丘脑 - 垂体 - 性腺轴中发挥关键作用。Kisspeptin 及其受体，即 kisspeptin 1 受体（Kiss1R），也在垂体中表达。本研究通过改变 GnRH 和 kisspeptin 在垂体促性腺细胞内各自受体的表达，证明了它们之间的相互作用。我们的结果表明，kisspeptin 和 Kiss1R 在小鼠垂体促性腺细胞系 LβT2 中表达。内源性 Kiss1R 对 kisspeptin 无反应，且无法刺激 LβT2 细胞中促性腺激素 LHβ 和 FSHβ 的表达；然而，kisspeptin 在过表达 Kiss1R 的 LβT2 细胞中增加了 LHβ 和 FSHβ 启动子活性。用 GnRH 刺激细胞显著增加了 Kiss1R 的表达，而 kisspeptin 则增加了这些细胞中 GnRH 受体（GnRHR）的表达。提高 Kiss1R 浓度导致促性腺激素 LHβ 和 FSHβ 亚基启动子的基础活性增加。此外，当大量 Kiss1R 表达载体导入细胞时，kisspeptin 诱导的 LHβ 启动子活性水平显著增加，但 FSHβ 启动子活性水平未显著增加。增加 Kiss1R 表达对 GnRH 诱导的促性腺激素启动子活性的诱导水平无显著影响。通过过表达细胞 GnRHR 增加 GnRHR 的量并不能增强促性腺激素启动子的基础活性；然而，kisspeptin 和 GnRH 刺激的促性腺激素启动子活性增加显著增强（GnRH 诱导的 LHβ 启动子除外）。在过表达 Kiss1R 或 GnRHR 的细胞中，含血清反应元件的启动子活性也发生了改变。我们目前的观察结果表明，GnRH 和 kisspeptin 通过相互增加其受体的表达来影响彼此刺激促性腺激素亚基基因表达的功能。
