Differential regulation of gonadotropin subunit gene promoter activity by pulsatile gonadotropin-releasing hormone (GnRH) in perifused LβT2 cells:: Role of GnRH receptor concentration
Differential regulation of gonadotropin subunit gene promoter activity by pulsatile gonadotropin-releasing hormone (GnRH) in perifused LβT2 cells:: Role of GnRH receptor concentration
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DOI：
10.1210/en.2002-221140
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发表时间：
2003-05-01
期刊：
影响因子：
4.8
通讯作者：
Kaiser, UB
中科院分区：
文献类型：
--
作者：
Bédécarrats, GY;Kaiser, UB
刺激垂体-性腺轴需要下丘脑脉冲式释放GnRH，GnRH脉冲频率的变化与垂体促性腺激素合成和释放LH和FSH的差异有关。促性腺激素如何区分GnRH脉冲频率，并随后差异调节LH β和FSH β基因的表达仍有待确定。在本研究中，使用灌注系统，使我们能够复制体内发生的GnRH脉动，我们已经系统地表征了不同的GnRH脉冲频率对LH β，FSH β，α和GnRH受体（GnRH HR）基因启动子刺激LbetaT 2细胞的影响。我们证明，LH β基因启动子活性的刺激在最大程度上在较高的GnRH脉冲频率，而FSH β基因启动子优先刺激在较低的GnRH脉冲频率，反映了以前的观察在原代大鼠垂体细胞在体内和体外。通过测量GnRH结合，我们表明，细胞表面的GnRH受体的数量增加，在较高频率的脉动GnRH和这种增加之前的LH β和FSH β基因启动子活性的差异调节。为了测试GnRH受体数量在介导脉冲GnRH的差异效应中的作用，在LbetaT 2细胞中过表达大鼠GnRH受体，并再次评估对脉冲GnRH的反应。有趣的是，虽然过表达GnRH受体对LH β的频率依赖性调节没有影响，但脉冲式GnRH对FSH β基因启动子活性的诱导减少，频率依赖性被消除。我们的研究结果表明，LbetaT 2细胞代表了一个合适的模型，用于研究促性腺激素亚单位基因表达的差异调节脉冲GnRH。此外，我们的研究表明，细胞表面GnRHR密度是这种差异调节的关键介质。
The pulsatile release of GnRH by the hypothalamus is required to stimulate the pituitary-gonadal axis, and variations in GnRH pulse frequency are associated with differential synthesis and release of LH and FSH by pituitary gonadotropes. How gonadotropes differentiate between GnRH pulse frequencies and subsequently differentially regulate the expression of the LHbeta and FSHbeta genes remains to be determined. In the present study, using a perifusion system that allows us to replicate the GnRH pulsatility occurring in vivo, we have systematically characterized the effects of varying GnRH pulse frequencies on LHbeta, FSHbeta, alpha, and GnRH receptor (GnRHR) gene promoter stimulation in LbetaT2 cells. We demonstrate that LHbeta gene promoter activity is stimulated to the greatest extent at higher GnRH pulse frequencies, whereas the FSHbeta gene promoter is preferentially stimulated at lower GnRH pulse frequencies, reflecting previous observations in primary rat pituitary cells in vivo and in vitro. By measuring GnRH binding, we demonstrate that cell-surface GnRHR number is increased at higher frequencies of pulsatile GnRH and that this increase precedes the differential regulation of LHbeta and FSHbeta gene promoter activity. To test the role of GnRHR number in mediating the differential effects of pulsatile GnRH, the rat GnRHR was overexpressed in LbetaT2 cells, and the response to pulsatile GnRH was again assessed. Interestingly, although overexpression of GnRHR had no effect on the frequency-dependent regulation of LHbeta, the induction of FSHbeta gene promoter activity by pulsatile GnRH was reduced, and frequency dependence was abrogated. Our results demonstrate that LbetaT2 cells represent a suitable model for the study of the differential regulation of gonadotropin subunit gene expression by pulsatile GnRH. Furthermore, our studies indicate that cell-surface GnRHR density is a critical mediator of this differential regulation.