Mechanisms of Signaling Protein Retention in the Primary Cilium

项目摘要 初级纤毛是一个孤立的膜突出的顶端表面的非循环休息 哺乳动物的细胞它作为一种感觉细胞器，负责静息细胞的感觉 环境条件，并与相邻的细胞进行通信。这个细胞器由一个 一个微管为基础的轴丝包裹在质膜，导致纤毛的形成 在其基部通过过渡区与细胞质分开的隔室。蛋白质运输 在睫状室内是由鞭毛内运输，横贯室双介导的。 在微管上定向。越来越多的证据表明，初级纤毛的能力， 作为感觉细胞器的功能依赖于各种信号分子的选择性积累。许多 纤毛依赖性通路的组分被发现被运输进出初级纤毛 对环境线索的反应。然而，受管制的贩运的基本机制仍然存在， 未知 拟议的应用是定义一个以前未知的机制，在鞭毛内蛋白质 正如我们的初步数据所表明的那样，它调节可溶性蛋白质的纤毛积累， 激酶对流动应力和化学刺激的响应。这种新型机制是由 滤泡素（FLCN）是一种肿瘤抑制因子，其缺陷导致Birt-Hogg-Dube（BHD）综合征， 临床上表现为多器官的良性肿瘤和囊性生长的遗传性疾病。在 FLCN的纤毛静止细胞失活对几种主要的纤毛依赖性细胞产生深远的影响， 通路，包括Sonic Hedgehog（Shh）通路，它变得完全活跃，对 配体刺激初步数据表明FLCN将Shh配体刺激偶联到睫状体， Smoothened（Smo）的积累和激活，这是Shh信号传导中的关键但知之甚少的步骤。 应用程序提出了定义潜在的分子基础及其功能意义， 一般纤毛信号。三条线的调查将进行的背景下，配体和流动 应激调节Shh信号传导。包括：1）确定FLCN介导的纤毛蛋白积累 控制Smo激活响应Shh配体刺激; 2）确定Rab23小的作用 GT3在FLCN纤毛功能中的作用; 3）确定流动应力如何通过 FLCN。成功完成拟议的研究将提供一个新的范例，以解释如何纤毛 信号传导受环境因素的调节，并阐明了Shh配体的潜在机制， 激活Smo。

PROJECT SUMMARY The primary cilium is a solitary membrane extrusion from the apical surface of noncycling resting cells in mammals. It functions as a sensory organelle that is responsible for the resting cells to sense environmental conditions and communicate with adjacent cells. This organelle is composed of a microtubule-based axoneme encased in the plasma membrane, resulting in formation of a ciliary compartment that is separated from the cytoplasm by a transition zone at its base. Protein trafficking within the ciliary compartment is mediated by intraflagellar transport that transverses the compartment bi- directionally on the microtubules. Accumulating evidence suggests that the ability of the primary cilium to function as a sensory organelle depends on selective accumulation of various signaling molecules. Many components of cilium-dependent pathways are found to be transported into and out of the primary cilium in response to environmental cues. However, the mechanisms underlying the regulated trafficking remain unknown. The proposed application is to define a previously unknown mechanism in intraflagellar protein trafficking that as suggested by our preliminary data, regulates ciliary accumulation of soluble protein kinases in response to flow stress and chemical stimulation. This novel mechanism is mediated by folliculin (FLCN), a tumor suppressor, of which defects cause the Birt-Hogg-Dube (BHD) syndrome, a genetic disorder that is manifested clinically by benign tumors and cystic growth in multiple organs. In ciliated resting cells inactivation of FLCN produces profound effects on several major cilium-dependent pathways, including the Sonic Hedgehog (Shh) pathway, which becomes fully active and unresponsive to ligand stimulation. Preliminary data suggest that FLCN couples Shh ligand stimulation to ciliary accumulation and activation of Smoothened (Smo), a key but poorly understood step in Shh signaling. The application is proposed to define the underlying molecular basis and its functional significance in general ciliary signaling. Three lines of investigation will be carried out in the context of ligand and flow stress regulated Shh signaling. including: 1) determining how FLCN-mediated ciliary protein accumulation controls Smo activation in response to Shh ligand stimulation; 2) determining the role of Rab23 small GTPase in the ciliary function of FLCN; 3) determining how flow stress controls Shh signaling through FLCN. Successful completion of the proposed studies will offer a new paradigm to explain how ciliary signaling is regulated by environmental cues and elucidate the mechanism underlying the Shh ligand- induced activation of Smo.