Role of afadin signaling in nephron tubulogenesis

描述(由申请人提供)：Afadin信号在肾小管生成项目中的作用概述/摘要极化上皮小管的形成对肾脏的结构和功能至关重要。尽管它很重要，但在理解小管形成的最早步骤，即上皮如何建立顶端-基底端和产生中心管腔方面存在着根本的差距。这一缺口的持续存在是一个重要的问题，因为在它被填补之前，对肾脏发育异常的理解在很大程度上仍然是无法理解的。这项应用的目的是阐明顶端-基底端的极性是如何建立的，以及管腔的形成是如何启动的，重点是Afadin信号在肾单位形成中的作用。Afadin是一种黏附受体Nectin家族的适配蛋白。我们的初步数据表明，Afadin对于建立顶端表面和启动发育中的小鼠肾单位的管腔形成至关重要。为了进一步阐明启动极性和管腔形成的细胞和分子机制，拟议的研究有三个具体目标。第一个目标是详细描述体内管腔形成的分子步骤。这些研究将通过对极性、运输和连接复合体的亚细胞定位，以及通过对小鼠管腔形成的实时成像，产生管腔起始的分子时间表。一旦确定了特征，进一步的研究将开始使用小鼠模型将蛋白质分配到该途径的不同阶段。第二个目标是利用已建立的3D细胞培养模型，确定根尖极性和管腔形成的新的分子机制。具体地说，拟议的实验将阐明Nectins和Afadin启动管腔形成的详细信号通路。第三个目的是研究Afadin在缺血损伤后小管再生中的作用，强调与发育过程的相似性。总之，这些研究将描绘出极性和管腔起始的基本步骤，并为理解肾小管发育和获得性疾病提供一个改进的框架。

DESCRIPTION (provided by applicant): Role of Afadin Signaling in Nephron Tubulogenesis Project Summary/Abstract Formation of polarized epithelial tubules is central to the structure and function of the kidney. Despite its importance, there is a fundamental gap in understanding the earliest steps in tubulogenesis, namely how epithelia establish apical-basal polarity and generate a central lumen. Continued existence of this gap represents an important problem because, until it is filled, an understanding of developmental abnormalities of the kidney will remain largely incomprehensible. The objective of this application is to elucidate how apical- basal polarity is established and lumen formation initiated, focusing on the role of Afadin signaling in nephron formation. Afadin is an adaptor protein to the Nectin family of adhesion receptors. Our preliminary data identify Afadin as critical for establishing an apical surface and initiating lumen formation in developing mouse nephrons. To further elucidate the cellular and molecular mechanisms that initiate polarity and lumen formation, the proposed studies have three specific aims. The first aim is to characterize molecular steps of lumen formation in vivo and in great detail. These studies will generate a molecular timeline of lumen initiation through subcellular localization of polarity, trafficking, and junctional complexes, and through live imaging of lumen formation in mice. Once characterized, additional studies will begin to assign proteins to different stages in the pathway using mouse models. The second aim is to identify novel molecular mechanisms of apical polarity and lumen formation using an established 3D cell culture model. Specifically the proposed experiments will elucidate a detailed signaling pathway by which Nectins and Afadin initiate lumen formation. The third aim will examine the role of Afadin in tubule regeneration after ischemic injury, emphasizing similarities to the developmental process. Together these studies will delineate fundamental steps in polarity and lumen initiation and provide an improved framework for understanding developmental and acquired disorders of renal tubules.