NEUROENDO SIGNAL TRANSDUCTION--REPRODUCTIVE PHYSIOLOGY

催乳素(PRL)是一种脑垂体前叶激素，对 女性生育能力。事实上，催乳素的高分泌是主要的 与女性不孕症相关的神经内分泌相关病理。 不幸的是，导致过度分泌的潜在缺陷 PRL的定义仍然不明确。为以下项目提供合理的框架 了解这些缺陷并治疗相关的病理，是 对阐明催乳素的细胞和分子机制至关重要 分泌调节。正常情况下，催乳素分泌处于紧张性抑制状态 由下丘脑多巴胺(DA)引起。催乳素周期性生理性激增 在女性中需要从这种多巴胺能抑制中撤出。 由于对DA的反应性降低是高催乳素血症的标志 症状，我们的注意力集中在细胞和分子基础上 DA对乳酸菌的作用。 我们已经发现并广泛表征了一种DA激活的 正常乳汁中的内向整流钾通道(KDA)。KDA DA激活导致乳酸膜超极化 和钙依赖动作电位的停止，驱动力 用于补充性催乳素分泌。体外研究已经证明了关键的 该KDA通道在DA调节PRL释放中的作用。 此外，Kda的功能表达依赖于 雌激素，这可能解释了人们长期以来认识到的 这个系统里有雌激素。在这些方面，KDA渠道位于 催乳素的多巴胺能调节中的顶级事件 分泌物。 作为阐明分子基础的第一步 KDA在乳酸菌中的生理作用，我们克隆了三个不同的 女性垂体前叶组织的K通道基因产物。基座 论天然通道与重组通道的功能相似性 在非洲爪哇卵母细胞中表达的通道，其中两个基因产物是 编码异源多聚体KDA的优秀候选亚单位。作为一名 在这些研究的逻辑延伸下，我们建议评估 这个效应器K通道在它的生理环境中-整个 动物--通过转基因技术。为此，我们将设计和 构建能抑制野生型的“显性-负性”突变体 KDA在乳酸菌中的作用。然后我们将创造一只转基因小鼠 该突变体的表达定向到脑下垂体的模型 使用催乳素启动子的乳酸菌。这些研究代表着一个及时的 而P.I.S工作的重要延伸和最终将提供 深入了解催乳素分泌紊乱的基础及其影响 关于女性的生育能力。

Prolactin (PRL), an anterior pituitary hormone, has profound effects on female fertility. In fact, hypersecretion of PRL is the major neuroendocrine-related pathology associated with female infertility. Unfortunately, the underlying defects which lead to the hypersecretion of PRL remain ill-defined. To provide a rational framework for understanding these defects and treating associated pathologies, it is essential to elucidate the cellular and molecular mechanisms of PRL secretion regulation. Normally PRL secretion is under tonic inhibition by hypothalamic dopamine (DA). Periodic, physiological surges of PRL in females require a withdrawal from this dopaminergic inhibition. Since reduced responsiveness to DA is a hallmark of hyperprolactinemic syndromes, our attention has focused on the cellular and molecular basis of DA action on the lactotrope. We have discovered and extensively characterized a DA-activated inwardly-rectifying potassium channel (KDA) in normal lactotropes. KDA activation by DA leads to hyperpolarization of the lactotrope membrane and cessation of calcium-dependent action potentials, the driving force for tonic PRL secretion. In vitro studies have demonstrated a critical role for this KDA channel in the regulation PRL release by DA. Furthermore, the functional expression of KDA is dependent upon estrogen, which may explain a long-recognized modulatory action of estrogen on this system. In these regards, the KDA channel lies at the top of a hierarchy of events in dopaminergic regulation of PRL secretion. As an initial step in elucidating the molecular basis for the physiological role of KDA in lactotropes, we have cloned three different K channel gene products from female anterior pituitary tissue. Based on functional similarities between the native channel and recombinant channels expressed in Xenopus oocytes, two of the gene products are excellent candidate subunits encoding a heteromultimeric KDA. As a logical extension of these studies, we propose to evaluate the role of this effector K channel within its physiological context- the whole animal-through transgenic technology. To this end, we will design and construct "dominant-negative" mutants, capable of inhibiting wild-type KDA function in lactotropes. We will then create a transgenic mouse model in which expression of this mutant is directed to pituitary lactotropes using the PRL promoter. These studies represent a timely and important extension of the P.I.'s work and will ultimately provide insight into the basis of disorders in PRL secretion and their impact on female fertility.