Betal Integrin and Renal Tubulogenesis

描述(申请人提供)：整合素是介导细胞-细胞外基质相互作用的主要受体，由异二聚体跨膜和亚基组成。在哺乳动物中发现的18和8亚基以一种受限的方式结合，形成具有不同配体结合特性的特定二聚体。1是肾脏中表达最丰富的整合素亚基，与至少12个亚基结合。其短的胞浆尾巴与多种细胞内分子相互作用，促进整合素介导的黏附、迁移和信号转导。这些蛋白质中定义最好的是Talins和kindlins，我们和其他人证明了它们是正常整合素功能所必需的。这些蛋白与在所有整合素细胞质尾巴中发现的两个典型的NPXY基序结合：膜近端的Talins和膜的远端基序kindlins。在上一个资助期，我们利用整合素Beta1flx/FLOX小鼠证明了整合素亚单位S是正常输尿管芽(UB)发育所必需的，因为使用Hoxb7cre小鼠删除它会导致分支形态发生严重异常。我们进一步表明，整合素1细胞质尾部典型NPXY基序的突变也会导致UB的异常发育。两个基序都有Y/A突变(从而影响Talin和kindlins的结合)的肾脏严重畸形和发育不良，但与UB整合素1缺失的小鼠相比，其严重的分支缺陷要轻得多。因此，在整合素生物学和肾脏发育领域中一个关键的悬而未决的问题是，NPXY基序如何调节整合素的功能，以及它们是否具有不同的功能。我们建议通过检验以下假设来回答这个问题：Talins和kindlins与整合素1细胞质尾部的特定NPYX基序的结合差异调节正常UB发育所需的整合素功能。这一假设将通过以下三个具体目标进行检验。1)确定Talin是否与整合素1细胞质尾部的膜近端NPXY基序结合是正常UB发育所必需的。2)确定kindlin是否与整合素1细胞质尾部的膜远端NPXY基序结合是UB正常发育和功能所必需的。3)明确整合素1 NPXY基序结合蛋白调控集合管细胞分支形态发生的机制。完成这些目标将有助于确定1在UB发育背景下整合素调节肾小管形成的基本机制。这对我们理解先天性肾发育不良/发育不良综合征和成人肾脏疾病都有意义，因为UB分支是决定肾单位数量的关键因素。

DESCRIPTION (provided by applicant): Integrins, the principal receptors that mediate cell-ECM interactions, are composed of heterodimeric transmembrane and subunits. The 18 and 8 subunits found in mammals combine in a restricted manner to form specific dimers with different ligand binding properties. 1, the most abundantly expressed integrin subunit in the kidney, binds at least 12 subunits. Its short cytoplasmic tail interacts with multiple intracellular molecules tht promote integrin- mediated adhesion, migration and signaling. The best defined of these proteins are talins and kindlins, which we and others showed are required for normal integrin function. These proteins bind to two canonical NPXY motifs found in all integrin cytoplasmic tails: talins to the membrane proximal and kindlins to the membrane distal motifs. In the last funding period, we utilized integrin beta1flox/flox mice to demonstrate that this integrin subunit s required for normal uretereic bud (UB) development, as deleting it using hoxb7cre mice resulted in severe abnormalities in branching morphogenesis. We further showed that mutating canonical NPXY motifs of the integrin 1 cytoplasmic tail also resulted in abnormal UB development. Kidneys with a Y/A mutation in both motifs (thus affecting binding of talins and kindlins) are severely dysmorphic and dysplastic, but have a significantly less severe branching defect than the UB integrin 1-null mice. Thus a key unanswered question in the field of integrin biology and kidney development is how the NPXY motifs regulate integrin function and whether they have distinct functions from each other. We propose to answer this question by testing the hypothesis that binding of talins and kindlins to specific NPYX motifs of the integrin 1 cytoplasmic tail differentially regulates integrin functions required for normal UB development. This hypothesis will be tested by the following three specific aims. 1) Determine if talin binding to the membrane proximal NPXY motif of the integrin 1 cytoplasmic tail is required for normal UB development. 2) Determine if kindlin binding to the membrane distal NPXY motif of the integrin 1 cytoplasmic tail is required for normal UB development and function. 3) Define the mechanisms whereby integrin 1 NPXY motif binding proteins regulate collecting duct cell branching morphogenesis. Completion of these aims will help define the fundamental mechanisms whereby 1 integrins regulate renal tubule formation in the context of UB development. This has implications for our understanding of both congenital renal hypoplasia/dysplasia syndromes and adult renal diseases as UB branching is a key determinant of nephron number.