Function of a membrane-localized nuclear receptor

描述（由申请人提供）：长期目标是了解核激素受体（NHR）如何响应信号而定向到质膜，以及它如何在非核信号转导系统中发挥作用。虽然类固醇信号传导的经典观点认为这些激素结合细胞内受体作为配体激活的转录因子，但大量证据表明类固醇也可以通过细胞表面的非基因组机制起作用。我们已经鉴定出秀丽隐杆线虫NHR， dpr1，它可能通过这样一个基于膜的信号系统起作用，为解剖基于膜的NHR信号系统提供了第一个遗传系统。在一个小的亲脂分子（水信息素或“daumone”）的存在下，dpr1从细胞质移动到质膜。杜蒙触发了另一种发育停滞状态，即多尔幼虫。DPR- 1基因的缺失突变会减弱对水信息素的反应，加速水状态的退出，而DPR- 1的过表达会引发不适当的水发育，抑制水状态的退出。DPR-1重新定位到细胞膜需要水调控途径。提出的研究将验证DPR-1通过质膜信号转导系统调节水形成的假设。Aim 1将研究影响DPR-1响应daer信息素重新定位的参数，分析DPR-1的基本功能，测试DPR-1的冗余伙伴，评估DPR-1与daer通路的关系。目标2将确定DPR-1信号传导和膜结合所需的结构元件和成分，测试其靶向膜和核时的信号功能，检查DPR-1在daer幼虫中膜坚韧形式的基础，并研究DPR-1与其他蛋白质之间的物理相互作用。目的3将研究DPR-1在异源细胞中是否对水信息素有反应，以及DPR-1亲属和调节水的NHR DAF- 12是否在水有利条件下与膜相关。Aim 4将启动RNAi筛选，以确定负责DPR-1重新定位的成分及其协同基因。阐明NHRs功能的新途径可能会促进我们对许多发育缺陷以及激素对正常人类生理和各种人类病理的影响的理解。

DESCRIPTION (provided by applicant): The long-term goals are to understand how a nuclear hormone receptor (NHR) is directed to the plasma membrane in response to a signal and how it might function in a non-nuclear signal transduction system. While the classical view of steroid signaling holds that these hormones bind intracellular receptors that act as ligand-activated transcription factors, extensive evidence indicates that steroids can also act by a non-genomic mechanism at the cell surface. We have identified a C. elegans NHR, DPR-1, that may act through such a membrane-based signaling system, providing the first genetic system for dissecting a membrane-based NHR signaling system. In the presence of a small lipophilic molecule (dauer pheromone or "daumone") DPR-1 moves from the cytoplasm to the plasma membrane. Daumone triggers an alternative, developmental arrested state, the dauer larva. A deletion mutation of the dpr-1 gene attenuates responsiveness to dauer pheromone and accelerates exit from the dauer state, and overexpression of DPR- 1 triggers inappropriate dauer development and inhibits exit from the dauer state. The dauer regulatory pathway is required for relocalization of DPR-1 to the membrane. The proposed studies will test the hypothesis that DPR-1 regulates dauer formation through a plasma membrane signal transduction system. Aim 1 will investigate parameters that influence relocalization of DPR-1 in response to dauer pheromone, analyze the essential function of dpr-1, test for redundant partners of DPR-1, and assess the relationship between DPR-1 and the dauer pathway. Aim 2 will identify structural elements and components required for DPR-1 signaling and membrane association, test its signaling function when targeted to the membrane and nucleus, examine the basis for a membrane-tenacious form of DPR-1 in dauer larvae, and investigate physical interactions between DPR-1 and other proteins. Aim 3 will examine whether DPR-1 responds to dauer pheromone in heterologous cells and whether DPR-1 relatives and the dauer-regulating NHR, DAF- 12, associate with the membrane under dauer-favoring conditions. Aim 4 will initiate RNAi screens to identify components responsible for relocalization of DPR-1 and genes with which it collaborates. The elucidation of novel pathways through which NHRs function may advance our understanding of many developmental defects and the hormonal influences on normal human physiology and a variety of human pathologies.