Determinants of GPCR Ciliary Localization and Effects on Signaling

描述（由申请人提供）：初级纤毛是存在于几乎所有哺乳动物细胞上的孤立附属物。虽然原纤毛曾经被认为是退化的，但它们现在被认为是重要的细胞感觉和信号细胞器。初级纤毛的形成或功能缺陷与许多人类发育障碍和疾病的发病机制有关。然而，纤毛在大多数细胞上的功能尚不清楚。对纤毛功能障碍和疾病的研究表明，初级纤毛的功能是由定位于纤毛膜的特定信号蛋白决定的。这些研究还表明，纤毛信号蛋白不能正确定位可导致疾病。然而，很少有纤毛信号蛋白被确定，并且调节它们定位到纤毛的机制仍然未知。我们发现，与人类纤毛疾病Bardet-Biedl综合征（BBS）相关的遗传缺陷似乎通过破坏G蛋白偶联受体（gpcr）到纤毛的运输机制影响纤毛功能。重要的是，这一发现可能代表了看似不同的BBS表型（包括肥胖、认知缺陷、肾囊性疾病和视网膜变性）病理生理学的基本机制。这一提议的中心假设是；1)纤毛GPCR含有介导其定位到纤毛的独特序列，2)GPCR的纤毛定位需要与BBS蛋白相互作用，3)BBS中纤毛受体的错定位会改变信号传导并导致疾病。本应用的目的是定义GPCR纤毛定位的分子内决定因素，并利用这些信息识别新的纤毛信号通路。明确GPCR纤毛定位的分子间决定因素以及BBS蛋白调控这一过程的机制，并确定纤毛GPCR错定位对信号传导的影响。这些研究将为了解纤毛gpcr的贩运提供有价值的见解，并将用于预测新的纤毛gpcr。了解纤毛定位的决定因素和机制，以及纤毛定位缺失对信号传导的影响，对于阐明这些细胞器的功能和确定它们在发育和疾病中的作用至关重要。

DESCRIPTION (provided by applicant): Primary cilia are solitary appendages that are present on nearly all mammalian cells. Although primary cilia were once considered vestigial, they are now recognized as important cellular sensory and signaling organelles. Defects in the formation or function of primary cilia have been implicated in the pathogenesis of many human developmental disorders and diseases. Yet, the functions of cilia on most cells are unknown. Studies of cilia dysfunction and disease have revealed that the functions of primary cilia are defined by the specific signaling proteins that localize to the membrane of the cilium. These studies have also shown that failure of ciliary signaling proteins to properly localize can lead to disease. However, few ciliary signaling proteins have been identified and the mechanisms that regulate their localization to cilia remain unknown. We have discovered that the genetic defects associated with the human ciliary disorder Bardet-Biedl syndrome (BBS) appear to affect cilia function through a mechanism that disrupts trafficking of G protein-coupled receptors (GPCRs) onto the cilium. Importantly, this finding may represent the fundamental mechanism underlying the pathophysiology of the seemingly diverse BBS phenotypes, including obesity, cognitive deficits, renal cystic disease, and retinal degeneration. The central hypotheses of this proposal are; 1) Ciliary GPCRs contain unique sequences that mediate their localization to cilia, 2) Ciliary localization of GPCRs requires interactions with the BBS proteins, and 3) Mislocalization of ciliary receptors in BBS alters signaling and leads to disease The objectives of this application are to define the intramolecular determinants of GPCR ciliary localization and use this information to identify novel ciliary signaling pathways, define the intermolecular determinants of GPCR ciliary localization and the mechanism(s) by which BBS proteins regulate this process, and determine the effects of ciliary GPCR mislocalization on signaling. These studies will lend valuable insight into the trafficking of ciliary GPCRs and will be used to predict novel ciliary GPCRs. Understanding the determinants and mechanisms of ciliary localization and the effects of a lack of ciliary localization on signaling is essential to elucidating the functions of these organelles and determining their roles in development and disease. PUBLIC HEALTH REVELANCE: Although it is known that almost every cell in the human body possesses an important sensory and signaling appendage called a primary cilium, the functions of cilia on most cells are unknown. The importance of these organelles is highlighted by the fact that defects in primary cilia have been associated with developmental disorders and diseases, including; obesity, renal disease, blindness, nervous system abnormalities, mental retardation, liver disease, and limb defects. The results obtained from the proposed studies will provide important insights into the mechanisms that control the localization of specific signaling proteins to cilia and how disruptions in these mechanisms affect signaling.