Adaptor Molecules in TGF-beta Signaling

TGF-β 信号转导中的衔接分子

• 批准号: 7921108
• 负责人: H WILLIAM SCHNAPER
• 金额: $ 10万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-25 至 2011-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7921108
• 关键词: 1-Phosphatidylinositol 3-Kinase; AXIN2 protein; Adaptor Signaling Protein; Address; Affect; Animal Model; Apoptosis; Binding; Cell Line; Cell Nucleus; Cells; Chronic; Cicatrix; Clathrin; Complex; Data; Down-Regulation; Early Endosome; End stage renal failure; Endocytosis; Epithelial; Epithelial Cells; Equilibrium; Event; Experimental Models; Exposure to; Extracellular Matrix; Fibrosis; Goals; Human; In Vitro; Kidney; Kidney Diseases; Laboratories; Learning; Location; Mediating; Mediator of activation protein; Mesenchymal; Organ; Outcome; Pathway interactions; Phenotype; Play; Prevention; Production; Proteins; Receptor Activation; Receptor Signaling; Regulation; Reporting; Role; Scaffolding Protein; Signal Transduction; Signaling Molecule; Smad Proteins; Smad protein; Transcriptional Regulation; Transforming Growth Factor beta; Transforming Growth Factors; Tubular formation; Work; base; complex R; cytokine; design; fibrogenesis; glomerulosclerosis; in vitro Model; in vivo Model; interest; kidney cell; mesangial cell; novel; prevent; protein transport; public health relevance; receptor; renal scarring; response; trafficking

DESCRIPTION (provided by applicant): Transforming growth factor (TGF)-¿ is a critical regulator of events leading to chronic progressive renal disease such as extracellular matrix production, apoptosis and epithelial-mesenchymal transition (EMT). While considerable progress has been made in understanding signaling from the TGF-¿ receptor (T¿R) through the Smad signaling molecules, the role of adaptor proteins such as Smad Anchor for Receptor Activation (SARA) in these signals is not well understood. Our preliminary data indicate that, in human mesangial cells (MC) and renal tubular epithelial cell lines (HKC and HK-2), SARA binds to Smad2 in a TGF-¿-dependent manner. In contrast, SARA is constitutively bound to T¿R and is associated with early endosomes. After TGF-¿1 treatment, Smad2 is phosphorylated and clathrin-mediated endocytosis (CME) facilitates propagation of the TGF-¿ signal to the nucleus. Thus, SARA may play a central role in protein trafficking related to TGF-¿ signaling, particularly through its actions in T¿R trafficking and promoting Smad2 activity. In addition to SARA, our preliminary data have detected other adaptor proteins in MC and HKC that are proposed to function in Smad signaling but are even less well understood than SARA. Prolonged TGF-¿1 treatment leads to an eventual decline in SARA expression, which corresponds temporally to the assumption of a myofibroblastoid phenotype in MC, HKC and HK-2. We propose the hypothesis that by acting as scaffolding proteins to assemble and localize the T¿R signaling complex, the adaptor proteins SARA, Dab2 and Axin may each impact the TGF-¿ response, and the loss of SARA expression may alter the balance in T¿R interactions to modulate Smad signaling and enhance TGF-¿-stimulated fibrosis. To address this hypothesis we will pursue four specific aims: (1) Characterize the interactions of SARA, Dab2 and Axin with T¿R in TGF-¿ signaling, their role in T¿R-complex trafficking, and their effect on Smad2- vs. Smad3-mediated responses to TGF-¿1. (2) Examine whether the loss of SARA is sufficient to induce alterations in signaling or trafficking related to fibrosis, and determine how these changes occur. (3) Define the mechanism by which TGF-¿1 decreases SARA expression and the role of PI- 3-kinase in this down-regulation. (4) Determine whether a decrease in SARA expression could play a role in established in vitro and in vivo models of renal fibrogenesis. These studies will identify novel events related to TGF-¿ signaling and renal cell fibrogenic activity. SIGNIFICANCE: Although TGF-¿ is an important mediator of renal fibrogenesis, its mechanisms of action are poorly understood. Our data suggest that the balance among several T¿R-interacting adaptor molecules plays an important role in regulating TGF-¿ responses. Specifically, these studies may identify novel mechanisms whereby kidney cells transition to a fibrogenic phenotype. Understanding these mechanisms may indicate potential targets for interrupting renal scarring. PUBLIC HEALTH RELEVANCE Transforming growth factor (TGF)-¿ is a protein that is found throughout the body and plays a central role in scarring of the kidney and other organs. Although we have made much progress in understanding how TGF-¿ works, we have not learned how to regulate its actions in order to prevent or minimize scarring of the kidney. This project seeks to understand how one group of proteins in the cell, the TGF-¿ receptor adaptor proteins, helps determine whether our cells are disposed to produce scar. In particular, we are interested in understanding how the expression of one protein, called SARA, is regulated and what role this regulation plays in scarring. Carrying out our specific aims will thus provide new basic information regarding how TGF-¿ works and how the kidney is damaged in progressive kidney disease that could be useful in prevention and treatment.

描述（由申请人提供）：转化生长因子(TGF)-¿是导致慢性进行性肾脏疾病的关键事件调节剂，如细胞外基质生成、细胞凋亡和上皮-间质转化（EMT）。虽然在理解TGF-受体（T¿R）通过Smad信号分子发出的信号方面已经取得了相当大的进展，但诸如Smad受体激活锚点（SARA）之类的接头蛋白在这些信号中的作用尚未得到很好的理解。我们的初步数据表明，在人系膜细胞（MC）和肾小管上皮细胞系（HKC和HK-2）中，SARA以TGF-依赖的方式与Smad2结合。相反，SARA与T¿R结合，并与早期核内体相关。TGF-¿1处理后，Smad2被磷酸化，网格蛋白介导的内吞作用（CME）促进了TGF-¿信号向细胞核的传播。因此，SARA可能在与TGF-信号相关的蛋白质运输中发挥核心作用，特别是通过其在T - R运输和促进Smad2活性中的作用。除了SARA，我们的初步数据还发现了MC和HKC中的其他接头蛋白，这些蛋白被认为在Smad信号传导中起作用，但比SARA更不清楚。长时间TGF-¿1治疗导致SARA表达最终下降，这与MC、HKC和HK-2中肌成纤维样细胞表型的假设在时间上相对应。我们提出假设，通过作为支架蛋白组装和定位T - R信号复合物，接头蛋白SARA、Dab2和Axin可能各自影响TGF-反应，SARA表达的缺失可能改变T - R相互作用的平衡，从而调节Smad信号并增强TGF-刺激的纤维化。为了解决这一假设，我们将追求四个具体目标：(1)表征TGF-信号传导中SARA、Dab2和Axin与T¿R的相互作用，它们在T¿R复合物运输中的作用，以及它们对Smad2-与smad3介导的TGF-¿1反应的影响。(2)检查SARA的缺失是否足以诱导与纤维化相关的信号或转运的改变，并确定这些变化是如何发生的。(3)明确TGF-¿1下调SARA表达的机制及PI- 3-激酶在其中的作用。(4)确定SARA表达的降低是否在体外和体内建立的肾纤维化模型中起作用。这些研究将确定与TGF-¿信号传导和肾细胞纤维化活性相关的新事件。意义：虽然TGF-¿是肾纤维化的重要介质，但其作用机制尚不清楚。我们的数据表明，几种T¿r相互作用的接头分子之间的平衡在调节TGF-反应中起着重要作用。具体来说，这些研究可能会确定肾细胞向纤维化表型转变的新机制。了解这些机制可能提示阻断肾瘢痕形成的潜在靶点。转化生长因子(TGF)-¿是一种存在于全身的蛋白质，在肾脏和其他器官的瘢痕形成中起着核心作用。尽管我们在了解TGF-¿如何工作方面取得了很大进展，但我们还没有学会如何调节它的作用，以防止或减少肾脏疤痕。该项目旨在了解细胞中的一组蛋白质，TGF-受体衔接蛋白，如何帮助确定我们的细胞是否倾向于产生疤痕。我们特别感兴趣的是了解一种叫做SARA的蛋白质的表达是如何被调节的，以及这种调节在疤痕形成中起什么作用。因此，实现我们的特定目标将提供关于TGF-¿如何工作以及肾脏如何在进行性肾脏疾病中受损的新的基本信息，这可能有助于预防和治疗。