Antifibrotic Actions of SARA

纤维化在慢性肾脏疾病(CKD)的进展中起着重要作用。我们的实验室有 确定Smad受体激活锚(SARA)是一个候选的抗纤维化分子。原来是这样的 被描述为促进Smad信号转导的转化生长因子-β受体适配器分子，SARA具有更广泛的 作为一个脚手架蛋白，在复合体中组装分子，指导细胞信号事件。我们 展示了SARA是如何参与内体信号传递的，并且它的表达有助于维持 处于分化状态的细胞。在受到纤维化刺激的细胞中，Sara的表达下调， 伴随着细胞呈现纤维化表型。在这些细胞中过表达sARA 阻止与纤维化相关的表型转换；相反，击倒Sara放大 转化生长因子-β诱导的胶原生成。在初步研究中，我们发现：1)SARA的表达是 2)马兜铃酸诱导的肾小管间质纤维化 在诱导方式过度表达sARA的小鼠中减少，3)过度表达sARA阻止 基因敲除诱导果蝇幼虫心肾管纤维化模型 组蛋白修饰基因。总而言之，这些数据支持这样的假设，即Sara在 一种抗纤维化的状态。通过调节SARA和/或介导性分子的表达 SARA的作用，我们可以改变导致肾纤维化的事件。在这里，我们提出三个具体的建议 旨在验证我们的假设，并将确定：(1)在肾纤维化过程中SARA的表达如何变化 在小鼠中，如果使用转基因方法增加或阻断SarA的表达可以改善或 分别加速了疾病的发生。(2)sARA在体外和体外肝纤维化过程中的表达调控。 活着。我们已经发现转录抑制因子BHLHE40抑制SarA的表达； 抗纤维化蛋白，可溶性Klotho，刺激SARA的表达。我们将确定这些 分子通过SARA影响纤维化肾脏疾病的结局。(3)SARA如何发出信号 以保护细胞不受纤维化“开关”的影响。我们将研究SARA如何影响WNT/β- 从转化生长因子-β作用的RNA序列探讨连环蛋白信号转导与SARA的新效应机制 小鼠细胞和经历心包肾细胞相关纤维化的果蝇幼虫。 意义：这些研究的完成将阐明SARA的机制 调节细胞的纤维化活性，目的是确定新的治疗靶点，以防止或 慢型慢性肾脏病相关纤维化。

Fibrogenesis plays a major role in chronic kidney disease (CKD) progression. Our laboratory has identified Smad anchor for receptor activation (SARA) as a candidate anti-fibrotic molecule. Originally described as a TGF-β receptor adaptor molecule that facilitates Smad signaling, SARA has a broader role as a scaffolding protein that assembles molecules in complexes to direct cell signaling events. We have shown how SARA participates in endosomal signaling, and that its expression helps to maintain cells in a differentiated state. SARA is downregulated in cells that are subjected to fibrogenic stimuli, concomitant with the cells presenting a fibrogenic phenotype. Overexpressing SARA in these cells prevents the phenotypic switch associated with fibrosis; conversely, knocking down SARA amplifies collagen production in response to TGF-β. In preliminary studies, we show: 1) SARA expression is markedly reduced in kidneys undergoing fibrosis, 2) aristolochic acid-induced tubulointerstitial fibrosis is reduced in mice that overexpress SARA in an inducible fashion, and 3) overexpressed SARA prevents fibrosis in a Drosophila larval heart-kidney tube model where fibrogenesis is induced by knockdown of histone-modifying genes. Together, these data support the hypothesis that SARA maintains cells in a fibrosis-resistant state. By regulating the expression of SARA and/or molecules that mediate SARA actions, we can modify the events leading to renal fibrosis. Here, we propose three specific aims to test our hypothesis and will determine: (1) How SARA expression changes during renal fibrosis in mice, and if increasing or blocking SARA expression using transgenic approaches ameliorates or accelerates disease, respectively. (2) How SARA expression is regulated during fibrosis in vitro and in vivo. We have found that the transcriptional repressor, BHLHE40, inhibits SARA expression; and the anti-fibrotic protein, soluble Klotho, stimulates SARA expression. We will determine how these molecules act through SARA to influence the outcome of fibrotic renal disease. (3) How SARA signals downstream to protect cells from the fibrogenic `switch.' We will examine how SARA affects Wnt/β- catenin signaling and seek new effector mechanisms of SARA through RNA-Seq of TGF-β-treated mouse cells, and of Drosophila larvae undergoing pericardial nephrocyte-associated fibrosis. SIGNIFICANCE: Completion of these studies will elucidate the mechanism by which SARA modulates cellular fibrogenic activity, with a goal of identifying novel therapeutic targets to prevent or slow CKD-associated fibrosis.