Mechanisms of Signaling Protein Retention in the Primary Cilium

项目总结 初级纤毛是从非循环休息区的顶面挤出的一层孤立的膜。 哺乳动物体内的细胞。它起着感觉器官的作用，负责休眠细胞的感觉 环境条件和与相邻单元的通信。这个细胞器由一个 以微管为基础的轴丝包裹在质膜中，形成纤毛 由底部的过渡区与细胞质隔开的隔室。蛋白质运输 在睫状室内是由鞭毛内的运输所调节的，它横跨睫状室。 在微管上定向。越来越多的证据表明，初级纤毛 作为感觉器官的功能依赖于各种信号分子的选择性积累。许多 纤毛依赖通路的组成部分被发现运输进和出初级纤毛。 对环境线索的反应。然而，受管制的贩运背后的机制仍然存在 未知。 建议的应用是定义鞭毛内蛋白以前未知的机制。 我们的初步数据表明，纤毛运输调节可溶性蛋白质的积累 对流动压力和化学刺激的反应。这一新的机制是由 卵泡蛋白(FLCN)是一种肿瘤抑制因子，其缺陷导致Birt-Hogg-Dube综合征(BHD)。 临床表现为多器官良性肿瘤和囊性生长的遗传性疾病。在……里面 纤毛静息细胞失活对纤毛依赖的几个主要因素的影响 途径，包括Sonic Hedgehog(Shh)途径，它变得完全活跃，对 配体刺激。初步数据表明，FLCN将Shh配体的刺激偶联到纤毛上 Smoothens(Smo)的积累和激活，这是Shh信号转导中的一个关键但知之甚少的步骤。 这一应用被用来定义潜在的分子基础及其功能意义 一般纤毛信号。将在配基和流动的背景下进行三条线的调查 胁迫调节Shh信号转导。包括：1)确定Flcn介导的睫状蛋白是如何积累的 控制Shh配体刺激下Smo的激活；2)确定Rab23 Small的作用 FLCN纤毛功能中的GTP酶；3)决定流动应激如何通过 Flcn.拟议研究的成功完成将提供一个新的范例来解释纤毛是如何 信号受环境信号的调节，并阐明Shh配体的潜在机制- Smo的诱导激活。

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.