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，对各种组织的正常功能非常重要，尤其是生殖系统。PRL表达具有时间特征，表明高度调节。这在很大程度上可以归因于作用于mammotrope群体以调节其合成和释放的下丘脑因子的数量和类型。然而，在理解PRL调节过程中同样重要的考虑因素是这些因子作用的促乳腺激素的功能状态。我们的测量PRL基因表达（PRL-GE）在个别生活mammotropes显示，细胞与较低的基础水平的PRL-GE更响应促甲状腺激素释放激素比细胞具有较高的水平，表明靶细胞的状态极大地影响其响应。此外，最近的实验表明，这些基础水平的催乳素-GE不是恒定的，但在重复的爆发或脉冲振荡。这些振荡反映了基础活动的时间变化，这可能决定了细胞对促分泌素的反应。最后，发现这些PRL-GE脉冲依赖于PRL启动子中的特定位点，称为E盒，其结合与昼夜节律基因调控相关的转录因子，表明脉冲的加工是高度调节和特定定时的细胞过程。总之，很明显，了解PRL-GE脉冲对于充分理解PRL的调节及其对生殖系统的影响至关重要。在这项研究中，我们提出了测试的假设，即“脉冲的PRL-GE是基础和刺激mammotrope功能的控制，因此是正常生殖功能的一个重要方面”。这将通过解决三个具体目标来实现：I）确定PRL-GE的基础脉冲模式和个体细胞中的分泌是否随着不同的生殖状态而固定或变化，II）阐明PRL-GE的脉冲和下丘脑促分泌素作用之间的关系（即，刺激性或抑制性），和III）鉴定在促乳腺细胞中作为脉动PRL-GE基础的分子过程。从这些研究中获得的信息将提供重要的洞察PRL表达的这一基本方面的作用，并应显着有助于我们的治疗高或低催乳素血症的条件，影响生殖的理解。

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.