Betal Integrin and Renal Tubulogenesis

描述（由申请人提供）：整合素是介导细胞-ECM相互作用的主要受体，由异二聚体跨膜亚基和亚基组成。在哺乳动物中发现的18和8个亚基联合收割机以受限的方式结合形成具有不同配体结合特性的特异性二聚体。1，在肾脏中表达最丰富的整合素亚基，结合至少12个亚基。它的短胞质尾区与多种细胞内分子相互作用，促进整合素介导的粘附、迁移和信号传导。这些蛋白质中最好定义的是talins和kindlin，我们和其他人表明它们是正常整合素功能所必需的。这些蛋白质结合到两个典型的NPXY基序中发现的所有整联蛋白胞质尾：talins的膜近端和kindlin的膜远端基序。在上一个资助期，我们利用整合素β 1flox/flox小鼠来证明这种整合素亚基是正常输尿管芽（UB）发育所必需的，因为使用hoxb 7 cre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，突变的典型NPXY基序的整合素1胞质尾也导致异常UB发展。在两个基序中具有Y/A突变的肾脏（因此影响talins和kindlin的结合）是严重畸形和发育不良的，但具有比UB整联蛋白1缺失小鼠显著更不严重的分支缺陷。因此，在整合素生物学和肾脏发育领域中的一个关键的未回答的问题是NPXY基序如何调节整合素功能以及它们是否具有彼此不同的功能。我们建议回答这个问题，通过测试的假设，结合的talins和kindlin的特定NPYX图案的整合素1胞质尾差异调节正常UB发展所需的整合素功能。这一假设将通过以下三个具体目标进行检验。1)确定talin与整合素1胞质尾区的近膜NPXY基序结合是否是正常UB发育所需。2)确定kindlin与整联蛋白1胞质尾区的膜远端NPXY基序结合是否是正常UB发育和功能所必需的。3)定义整合素1 NPXY基序结合蛋白调控集合管细胞分支形态发生的机制.这些目标的完成将有助于确定1整合素在UB发育背景下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全/发育不良综合征和成人肾脏疾病具有意义，因为UB分支是肾单位数量的关键决定因素。 公共卫生相关性：我们预计，这项研究将产生新的见解整合素及其结合伙伴，talins和kindlin在肾脏收集系统的发展中的作用。这些知识对于我们理解肾集合系统的功能是至关重要的，并可能定义婴儿畸形发育不良肾脏的新病因。

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. PUBLIC HEALTH RELEVANCE: We anticipate that this study will generate novel insights into the role of integrins and their binding partners, talins and kindlins in the development of the collecting system of the kidney. This knowledge is fundamental to our understanding of how the renal collecting system functions and could potentially define new etiologies for dysmorphic dysgenic kidneys in infants.