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）如何响应信号定向至质膜，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作为配体激活的转录因子的细胞内受体，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。我们已经确定了一个C。elegans NHR，DPR-1，可能通过这种基于膜的信号系统发挥作用，为剖析基于膜的NHR信号系统提供了第一个遗传系统。在存在小的亲脂性分子（道厄信息素或“道蒙”）的情况下，DPR-1从细胞质移动到质膜。杜蒙引发了另一种发育停滞状态，即幼虫。dpr-1基因的缺失突变减弱了对dauer信息素的反应性并加速退出dauer状态，并且DPR- 1的过表达触发了不适当的dauer发育并抑制退出dauer状态。DPR-1在细胞膜上的再定位需要dauer调节通路。本研究将验证DPR-1通过质膜信号转导系统调节dauer形成的假设。目的1研究影响DPR-1在dauer信息素作用下重定位的参数，分析DPR-1的基本功能，检测DPR-1的冗余配偶体，并评估DPR-1与dauer途径之间的关系。目标2将确定DPR-1信号传导和膜缔合所需的结构元件和组件，测试其针对膜和细胞核的信号传导功能，检查DPR-1在Dauer幼虫中的膜粘性形式的基础，并研究DPR-1与其他蛋白质之间的物理相互作用。目的3将检查DPR-1是否响应于异源细胞中的dauer信息素，以及DPR-1亲属和dauer调节NHR，NHR- 12是否在dauer有利条件下与膜结合。Aim 4将启动RNAi筛选，以确定负责DPR-1重新定位的组件以及与其合作的基因。阐明NHRs功能的新途径可能会促进我们对许多发育缺陷和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.