The Laminin Receptors in Kidney Development

描述（由申请人提供）：整合素是介导细胞与ECM之间相互作用的由β和β亚基组成的跨膜受体。在哺乳动物中，有18 ′和8 ′亚基，它们联合收割机形成二聚体，表现出不同的配体结合特性。整合素通过这些配体结合特性分为胶原、LM和RGD结合受体。主要的LM结合整合素是β 3 β 1、β 6 β 1和β 6 β 4。虽然对配体的特异性由整合素胞外结构域介导，但其跨膜结构域（TM）和胞质尾区（CT）在介导选择性胞内信号传导的活化中起关键作用，从而有助于整合素功能的特异性。 整合素介导的细胞与LM相互作用对肾集合系统发育至关重要。我们以前的研究表明，在小鼠UB中缺失整合素β 3亚基会产生发育表型，与最近在人类中的发现相似，会使小鼠在单侧输尿管梗阻（UUO）后对肾纤维化易感。相比之下，缺失整合素β 6或β 4亚基并不改变UB的发展，但UUO引起严重的肾小管扩张。我们的初步数据显示，整合素β 3/β 6复合突变小鼠的肾脏表型比单一突变小鼠明显更差，这表明整合素β 3、β 1和β 6整合素之间的合作是UB发育和正常功能所必需的。我们进一步表明，当缺乏β 3或β 6亚基的集合管（CD）细胞接种在同一LM上时，整合素β 3 β 1和β 6 β 1依赖的细胞内信号传导存在重大差异。这一结果表明，β 3和β 6 TM/CT结构域激活特定的信号通路。这些观察结果提出了几个关键的未回答的问题，在该领域的LM整合素在肾脏：LM整合素如何协同它们的信号和什么是机制，使他们的TM/CT域调节差异信号，尽管结合相同的配体？我们将通过检验LM整合素的TM/CT结构域的功能和结构特征赋予正常UB发育和功能所需的信号传导特异性的假设来回答这些问题。为了验证这一假设，我们将：目的1）定义LM整合素如何在UB发育和功能中合作。目的2）探讨整合素α 3和α 6 CTs调控CD细胞功能的机制。目的3）确定α 3、α 6 TM/CT结构域及β 3 β 1和β 6 β 1 TM/CT异二聚体的结构。

DESCRIPTION (provided by applicant): Integrins are transmembrane receptors composed of � and � subunits that mediate the interactions between cells and ECM. In mammals, there are 18 � and 8 � subunits, which combine to form dimers that exhibit different ligand binding properties. Integrins are classified by these ligand binding properties into collagen, LM and RGD binding receptors. The principal LM binding integrins are �3�1, �6�1 and �6�4. While specificity to ligand is mediated by the integrin extracellular domains, their transmembrane domain (TM) and cytoplasmic tail (CT) play a critical role in mediating activation of selective intracellular signaling, thus contributing to specificity of integrin function. Integrin-mediated cell interactins with LMs are critical for renal collecting system development. We previously showed that deleting the integrin �3 subunit in the UB in mice gives a developmental phenotype and, similar to the recent findings in humans, makes mice susceptible to renal fibrosis after unilateral ureteric obstruction (UUO). By contrast, deleting the integrin �6 or �4 subunits did not alter UB development; but UUO caused severe tubular dilatation. Our preliminary data show that integrin �3/�6 compound mutant mice develop significantly worse renal phenotypes than single mutants, suggesting that cooperation between integrins �3�1 and �6 integrins is required for development and proper function of the UB. We further showed that when collecting duct (CD) cells lacking the �3 or the �6 subunit were plated on the same LM, there were major differences in integrin �3�1- and �6�1-dependent intracellular signaling. This result indicates that the �3 and �6 TM/CT domains activate specific signaling pathways. These observations pose several key unanswered questions in the field of LM integrins in the kidney: how do LM integrins synergize their signaling and what are the mechanisms whereby their TM/CT domains regulate differential signaling despite binding the same ligand? We will answer these questions by testing the hypothesis that functional and structural features of the TM/CT domains of the LM integrins confer specificity of signaling required for normal UB development and function. To test this hypothesis, we will: Aim 1) Define how the LM integrins cooperate in UB development and function. Aim 2) Determine the mechanism whereby integrin a3 and a6 CTs regulate CD cell function. Aim 3) Determine the structures of the individual a3, a6 TM/CT domains and of the �3�1 and �6�1 TM/CT heterodimers.