Beta Endorphin Neurons and the Control of Homeostasis

描述(申请人提供)：拟议研究的长期目标是确定雌激素(E2)作用于下丘脑POMC(β-内啡肽)和多巴胺神经元以调节生殖、温度调节、应激反应、摄食、动机和奖励等动态平衡功能的快速信号机制(S)；并将这些信息整合到由E2启动的膜启动信号的细胞模型中。了解E2的这些新的、快速的作用及其与其基因组作用的关系，将为大约5000万需要激素替代治疗的妇女面临的一个根本问题提供洞察。雌二醇具有神经保护作用，防止潮热，对情绪和情绪有积极影响，对骨质疏松有保护作用，但会增加患乳腺癌和子宫癌的风险。选择性雌激素受体调节剂(SERM)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，因此非常需要。已有研究表明，雌激素核受体ERα和ERβ负责E2的所有作用，但我们的研究为一种新的膜相关E2受体提供了强有力的证据，该受体介导中枢神经系统的快速信号传递。受体尚未被识别，其与效应器系统的偶联的性质也不完全清楚。我们最近合成了第一个SERM，STX，它专门针对膜受体，这将使我们能够严格表征并最终识别膜ER。我们的假设是，E2的快速作用是由于它与G蛋白偶联受体结合，该受体激活激酶通路以减弱GABA-B和Mu-阿片受体的活性。在这个提案中，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偶联的E2受体，它与下丘脑神经元中的信号通路的偶联及其功能后果。其具体目的是：(1)测试STX是否使用与E2相同的受体介导的信号通路，使POMC和多巴胺神经元的K+通道中的GABA-B和Mu-阿片受体解偶联。(2)测试STX是否改变了下丘脑神经元中对突触传递至关重要的一组E2调节的转录子的基因表达。(3)检测雌二醇和S TX对雌激素受体α和β缺陷小鼠前额叶细胞和多巴胺神经元的快速作用，并在此基础上建立膜雌激素受体的克隆策略。这些研究不仅将确定对下丘脑神经元快速信号传递至关重要的通路(S)，而且还将允许开发新的SERM，专门针对参与女性体内平衡控制的关键大脑回路。

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.