Prolactin gene expression dynamics and mammotrope function

描述（由申请人提供）：催乳素（PRL）由垂体前叶释放，对多种组织的正常功能非常重要，特别是生殖系统的组织。PRL的表达具有时间特征，表明其受高度调控。这在很大程度上可以归因于下丘脑因子的数量和类型，这些因子作用于乳房增生人群，调节其合成和释放。然而，在理解PRL调控过程中，同样重要的考虑因素是这些因素所作用的乳腺的功能状态。我们对个体活乳腺组织中PRL基因表达（PRL- ge）的测量显示，PRL- ge基础水平较低的细胞对促甲状腺激素释放激素的反应比基础水平较高的细胞更敏感，这表明靶细胞的状态极大地影响了其反应。此外，最近的实验表明，这些PRL-GE的基础水平不是恒定的，而是在重复的爆发或脉冲中振荡。这些振荡反映了基底活动的时间变化，这可能决定了细胞对分泌物的反应准备程度。最后，这些PRL- ge脉冲被发现依赖于PRL启动子中一个被称为E-box的特定位点，该位点结合与昼夜节律基因调控相关的转录因子，这表明脉冲的细化是一个高度调控的、特定定时的细胞过程。综上所述，很明显，了解PRL- ge脉冲对于充分理解PRL的调控及其对生殖系统的影响至关重要。在这项研究中，我们提出验证“PRL-GE脉冲是控制乳腺基底和刺激功能的基础，因此是正常生殖功能的一个重要方面”的假设。这将通过解决三个特定目标来实现：1)确定PRL-GE的基本脉冲模式和单个细胞的分泌是固定的还是随着不同的生殖状态而变化；2)阐明PRL-GE脉冲与单个乳腺细胞下丘脑分泌作用（即刺激或抑制）之间的关系；3)确定乳腺细胞搏动PRL-GE的分子过程。从这些研究中获得的信息将对PRL表达的这一基本方面的作用提供重要的见解，并应显著有助于我们理解影响生殖的高或低泌乳素血症的治疗方法。

DESCRIPTION (provided by applicant): Prolactin (PRL) is released by the anterior pituitary and is important for the proper functioning of a wide variety of tissues, especially those of the reproductive system. PRL is expressed with temporal characteristics that suggest a high degree of regulation. Much of this can be attributed to the number and type of hypothalamic factors that act on the mammotrope population to modulate its synthesis and release. However, an equally important consideration in understanding the process of PRL regulation is the functional state of the mammotropes on which these factors act. Our measurement of PRL gene expression (PRL-GE) in individual living mammotropes revealed that cells with lower basal levels of PRL-GE were more responsive to thyrotropin releasing hormone than cells with higher levels indicating that the state of a target cell greatly impacts its response. Moreover, recent experiments revealed that these basal levels of PRL-GE are not constant, but oscillate in repetitive bursts or pulses. These oscillations reflect temporal changes in basal activity that would likely dictate the readiness of the cell to respond to secretagogues. Finally, these PRL-GE pulses were found to depend on a specific site in the PRL promoter termed an E-box that bind transcription factors associated with circadian gene regulation suggesting that elaboration of a pulse is a highly regulated and specifically timed cellular process. Taken together, it is clear that an understanding of PRL-GE pulses is critical to fully comprehend the regulation of PRL and its impact on the reproductive system. In this study, we propose to test the hypothesis that "pulses of PRL-GE are fundamental to the control of both basal and stimulated mammotrope function and consequently are an important facet of normal reproductive function". This will be accomplished by addressing three SPECIFIC AIMS: I) to determine whether basal pulse patterns of PRL-GE and secretion in individual cells are fixed or change with varying reproductive state, II) to elucidate the relationship between pulses of PRL-GE and hypothalamic secretagogue action (i.e., stimulatory or inhibitory) in single mammotropes, and III) to identify the molecular processes that underlie pulsatile PRL- GE in mammotropes. Information gained from these studies will provide important insight into the role of this fundamental aspect of PRL expression and should contribute markedly to our understanding of the treatment of hyper or hypoprolactinemic conditions that impact reproduction.