Beta Endorphin Neurons and the Control of Homeostasis

描述（由申请人提供）：拟议研究的长期目标是确定雌激素（E2）在下丘脑POMC（β-内啡肽）和多巴胺神经元中作用以调节稳态功能（如生殖、温度调节、应激反应、进食、动机和奖励）的快速信号传导机制;并将此信息纳入E2膜启动信号传导的细胞模型中。了解E2的这些新颖、快速的作用以及它们与其基因组作用的关系，将有助于深入了解大约5000万需要激素替代疗法的妇女所面临的一个基本问题。E2具有神经保护作用，可防止潮热，对情绪和情感有积极影响，可预防骨质疏松症，但会增加患乳腺癌和子宫癌的风险。非常需要在中枢神经系统（CNS）中产生E2的有益作用但缺乏E2的癌症风险特征的选择性雌激素受体调节剂（SERM）。已经表明，核雌激素受体ER α和ER β负责E2的所有作用，但我们的研究为新型膜相关E2受体介导CNS中的快速信号传导提供了强有力的证据。该受体尚未被确定，也不是其耦合效应系统的性质完全理解。我们最近合成了第一个SERM，STX，专门针对膜受体，这将使我们能够严格表征并最终确定膜ER。我们的假设是，E2的快速作用是由于其结合G蛋白偶联受体，激活激酶途径，减弱GABA-B和μ阿片受体的活性。在这个提议中，我们试图阐明STX激活的细胞级联反应，并进一步表征介导这些效应的受体。我们将使用一系列独特的细胞，分子和化学工具来表征Gq偶联E2受体，其耦合到下丘脑神经元的信号通路及其功能后果。具体目标是：（1）测试STX是否使用与E2相同的受体介导的信号传导途径来使GABA-B和μ-阿片受体与POMC和多巴胺神经元中的K+通道解偶联。(2)检测STX是否改变了下丘脑神经元中对突触传递至关重要的E2调节转录物亚组的基因表达。(3)为了测试E2和S TX对POMC和多巴胺神经元的快速作用是否存在于ER α和β缺陷小鼠中，并基于结果开发膜ER的克隆策略。这些研究不仅将确定对下丘脑神经元中的快速信号传导至关重要的通路，而且还将允许开发新的SERM，其特异性靶向参与女性体内稳态控制的关键脑回路。

DESCRIPTION (provided by applicant): The long-range goal of the proposed research is to define the rapid signaling mechanism(s) by which estrogen (E2) acts in hypothalamic POMC (beta-endorphin) and dopamine neurons to modulate homeostatic functions such as reproduction, temperature regulation, stress responses, feeding, motivation and reward; and to incorporate this information into a cellular model of membrane-initiated signaling by E2. Understanding these novel, fast actions of E2 and how they relate to its genomic actions will provide insight into a fundamental problem facing approximately 50 million women in need of hormone replacement therapy. E2 is neuroprotective, prevents hot flushes, has a positive influence on mood and affect, is protective against osteoporosis but increases the risk of breast and uterine cancers. Selective estrogen receptor modulators (SERMs) that produce the beneficial effects of E2 in the central nervous system (CNS) but lack the cancer risk profile of E2 are greatly needed. It has been suggested that the nuclear estrogen receptors ER alpha and ER beta are responsible for all of the actions of E2, but our studies provide strong evidence for a novel membrane-associated E2 receptor that mediates rapid signaling in the CNS. The receptor has not yet been identified nor is the nature of its coupling to effector systems completely understood. We recently synthesized the first SERM, STX, that specifically targets the membrane receptor, which will allow us to rigorously characterize and eventually identify the membrane ER. Our hypothesis is that the rapid effects of E2 are due to its binding to a G protein-coupled receptor that activates kinase pathways to attenuate GABA-B and mu-opioid receptor activity. In this proposal, we seek to elucidate the cellular cascades activated by STX and to further characterize the receptor mediating these effects. We will use a unique range of cellular, molecular and chemical tools to characterize the Gq-coupled E2 receptor, its coupling to signaling pathways in hypothalamic neurons and its functional consequences. The specific aims are: (1) To test whether STX uses the same receptor-mediated signaling pathway as E2 to uncouple GABA-B and mu-opioid receptors from K+ channels in POMC and dopamine neurons. (2) To test whether STX alters gene expression in a sub-group of E2-regulated transcripts that are critical for synaptic transmission in hypothalamic neurons. (3) To test whether the rapid effects of E2 and S TX on POMC and dopamine neurons are present in ER alpha and beta-deficient mice, and based on the results develop a cloning strategy for the membrane ER. These studies will not only identify the pathway(s) that is critical for rapid signaling in hypothalamic neurons but also should allow the development of new SERMs specifically targeting critical brain circuits involved in the control of homeostasis in the female.