GnRH Signaling Mechanisms in the Pituitary Gonadotrope

描述(由申请人提供)：了解构成生殖内分泌轴的组织的发育和调节对于了解生殖功能至关重要。控制生殖功能的中枢调节激素是神经肽促性腺激素释放激素I(GnRH)。促性腺激素释放激素I的主要靶点是垂体前叶促性腺激素的数量。促性腺激素释放激素对促性腺激素的脉动刺激导致异二聚体促性腺激素、黄体生成素和卵泡刺激素的合成和释放增加，进入全身循环。在之前的资助期间，我们描述了GnRH受体翻译控制的新特性。翻译调控是一种直接调节基因表达的手段，特别适用于体内GnRH脉冲幅度和频率的快速变化。在这一更新应用中，我们的目标是彻底了解GnRH的作用，即通过改变促性腺激素蛋白质合成来解释促性腺激素基因表达的短期变化。我们的目标是对GnRH信号在促性腺激素中介导翻译控制的机制有一个基本的了解。然后，我们将定义翻译控制特异性的结构基础，并将我们的研究扩展到研究脉动性在基因调控中的作用。 目的1：GnRH对翻译的调控。我们将确定在促性腺激素细胞系中介导翻译控制的GnRH作用的靶点。我们将在原代垂体培养和一种新的转基因小鼠模型中证实我们的发现。 目的2：GnRH利用信使核糖核酸的特异性。我们将确定促性腺激素特异性基因对翻译调控的敏感性，以确定通过这一机制进行调控的特异性。我们将确定这种特异性的分子基础。 目的3：脉冲性促性腺激素释放激素对促性腺激素合成的调节作用。我们假设翻译和转录受不同的GnRH脉冲机制的不同调控。我们将通过确定调节成分的激活程度和确定负反馈信号在调节对GnRH刺激的反应中的作用来测试这一调节模型和替代调节模型。

DESCRIPTION (provided by applicant): Understanding the development and regulation of the tissues that comprise the reproductive endocrine axis is essential to understanding reproductive function. The central regulatory hormone controlling reproductive function is the neuropeptide gonadotropin-releasing hormone I (GnRH). The principal target of GnRH I is the population of gonadotropes in the anterior pituitary. Pulsatile GnRH stimulation of gonadotropes results in increased synthesis and release of the heterodimeric gonadotropin hormones Luteinizing Hormone and Follicle-Stimulating Hormone into the general circulation. During the previous funding period we described the novel property of translational control by the GnRH receptor. Translational control is a means of direct regulation of gene expression that is uniquely suited to the rapid in vivo changes in GnRH pulse amplitude and frequency. In this renewal application, it is our goal to develop a thorough understanding of GnRH action that accounts for short-term changes in gonadotropin gene expression through alterations in gonadotropin protein synthesis. Our aims are directed toward a basic understanding of the mechanisms of GnRH signaling that mediate translational control in gonadotropes. We will then define the structural basis for the specificity of translation control, and extend our studies to investigate the role of pulsatility in gene regulation. Aim 1: Regulation of translation by GnRH. We will define the targets of GnRH action that mediate translational control in a gonadotrope cell line. We will confirm our findings in primary pituitary culture and in a novel transgenic mouse model. Aim 2: Specificity of mRNA utilization by GnRH. We will determine the sensitivity of gonadotropespecific genes to translational control to establish the specificity of regulation through this mechanism. We will determine the molecular basis for this specificity. Aim 3: Regulation of gonadotropin synthesis by pulsatile GnRH. We hypothesize that translation and transcription are differentially regulated by differing GnRH pulse regimes. We will test this and alternate models of regulation by determination of the degree of regulatory component activation and determination of the role of negative feedback signaling in modulating the response to GnRH stimulation.