lntegrin binding proteins and the kidney

慢性肾脏疾病(CKD)的一个特征是进展为肾小管间质(TI)纤维化。虽然新的机制 近几十年来，已经发现了一种有效的治疗方法来直接阻止或逆转这一过程 仍然难以捉摸。我们小组长期以来一直有兴趣定义细胞外基质(ECM)受体如何 如整合素及其结合伙伴调节肾脏发育和对损伤的反应。在这些人中 整合素结合伙伴，我们关注的是整合素连接的激酶(ILK)；PINCH；α-Parvin复合体的支架 蛋白质，也称为IPP复合体。我们最近发现了一种干扰整合素的新方式 IPP复合体介导的依赖信号通路可能代表一种新的治疗和 预防TI纤维化，并最终预防CKD。 整合素是由非共价结合的α和β亚基组成的跨膜受体。β1是最多的 在肾脏中大量表达，可与12种不同的α亚基结合。β-1胞质尾巴 通过结合多种胞质蛋白来调节整合素介导的信号和细胞骨架的功能 调制。IPP复合体是结合整合素β1胞浆尾巴及其键的主要骨架枢纽 功能是捆绑肌动蛋白细丝，从而在整合素和肌动蛋白之间传递机械信号 细胞骨架。正常的肌动蛋白细胞骨架是胚胎所必需的大多数细胞功能所必需的。 损伤后组织的发育和恢复。ILK是带来IPP复合体的主要支架蛋白 然而，α和βParvins是调节肌动蛋白细胞骨架的主要IPP复合蛋白。 我们有初步证据表明，α-PARVIN是正常肾脏发育和损伤后修复所必需的。 小鼠肾收集系统启动时α-PARVIN缺失(E10.5)导致严重畸形 基底侧F-肌动蛋白过量的肾脏。我们还提供了证据表明，在完全发育的人中删除α-parvin 肾集合系统(E18.5)导致单侧输尿管梗阻后过度的肾小管损伤 (UUO)模型。携带不能与α-PARVIN结合的突变同类的小鼠(A.A.220：ILK-K220M 小鼠)在发育中的收集系统中发育正常，用小分子治疗的野生型小鼠 Csbl-1(干扰ILK-α-PARVIN相互作用)可减轻UUO后的肾纤维化。这些 数据有力地表明，α-PARVIN执行多种独立于其相互作用的细胞功能 随着ILK和矛盾地破坏ILK与α-帕尔文的结合，提高了肾脏对损伤的反应。 最后，我们有证据表明α-Parvin-Null集合管(CD)细胞有过量的F-肌动蛋白形成， 细胞黏附、扩散和迁移增加，活化的RhoA和CDC42显著增加。 基于这些数据，我们假设α-parvin通过Rho-GTP酶介导的肌动蛋白动力学的调节 信号转导促进肾小管发育、动态平衡和损伤后的恢复。这一假设 将在以下两个目标中进行测试。 目的1.探讨α-PARVIN在肾小管发育和损伤中的作用。我们将检验这一假设 α-Parvin介导的肌动蛋白细丝捆绑是正常肾小管发育和 保护免受伤害。 目的2.确定α-Parvin调节依赖肌动蛋白捆绑的上皮细胞的机制 功能。我们将检验α-Parvin介导的对RhoA和Cdc42活性的抑制这一假设 促进cofilin介导的肌动蛋白周转依赖的上皮细胞的极性和增殖，即 对于正常的肾小管形成和修复是必需的。

A hallmark of chronic kidney disease (CKD) is advancing tubulointerstitial (TI) fibrosis. While new mechanisms of fibrosis have been uncovered in recent decades, effective treatment to directly halt or reverse this process remains elusive. Our group has a long-standing interest in defining how extracellular matrix (ECM) receptors such as integrins and their binding partners regulate kidney development and response to injury. Among the integrin binding partners, we focus on the integrin linked kinase (ILK); pinch; α-parvin complex of scaffold proteins, also known as the IPP complex. We recently uncovered a novel modality to interfere with integrin dependent signaling pathways mediated by the IPP complex that may represent a new strategy to treat and prevent TI fibrosis and ultimately CKD. Integrins are transmembrane receptors composed of non-covalently bound α and β subunits. β1 is the most abundantly expressed subunit in the kidney and can bind 12 different α subunits. The β1 cytoplasmic tail functions by binding multiple cytoplasmic proteins which regulate integrin-mediated signaling and cytoskeleton modulation. The IPP complex is a major scaffolding hub that binds the integrin β1 cytoplasmic tail and its key function is to bundle actin filaments, thereby transmitting mechanical signals between integrins and the actin cytoskeleton. A normal actin cytoskeleton is required for most cell functions necessary for embryonic development and recovery of tissue from injury. ILK is the major scaffold protein that brings the IPP complex together; however, the α and β parvins are the major IPP complex proteins that regulate the actin cytoskeleton. We have preliminary evidence that α-parvin is required for normal kidney development and repair after injury. Deletion of α-parvin in mice at the initiation of the kidney collecting system (E10.5) causes severely dysmorphic kidneys with excessive basolateral F-actin. We also provide evidence that deleting α-parvin in the fully developed kidney collecting system (E 18.5) results in excessive tubular injury following a unilateral ureteric obstruction (UUO) model. Mice carrying a mutant ILK unable to bind to α-parvin (K-to-M mutation in a.a. 220: ILK-K220M mice) in the developing collecting system develop normally and wild-type mice treated with the small molecule Csbl-1 (that interferes with the ILK-α-parvin interaction) have decreased renal fibrosis following UUO. These data strongly suggest that α-parvin performs multiple cellular functions that are independent of its interactions with ILK and paradoxically disrupting ILK binding to α-parvin improves the response of the kidney to injury. Finally, we have evidence that α-parvin-null collecting duct (CD) cells have excessive F-actin formation, increased cell adhesion, spreading and migration as well as a profound increase in activated RhoA and Cdc42. Based on these data, we hypothesize that α-parvin-mediated regulation of actin dynamics via Rho-GTPase signaling promotes kidney tubule development, homeostasis, and recovery from injury. This hypothesis will be tested in the following 2 aims. Aim 1. Determine the role of α-parvin in kidney tubule development and injury. We will test the hypothesis that α-parvin-mediated actin filament bundling is required for normal kidney tubule development and protection from injury. Aim 2. Determine the mechanisms whereby α-parvin regulates actin-bundling dependent epithelial cell function. We will test the hypothesis that α-parvin-mediated inhibition of RhoA and Cdc42 activity promotes cofilin-mediated actin turnover dependent epithelial cell polarity and proliferation that is required for normal tubule formation and repair.