Antifibrotic Actions of SARA

纤维化在慢性肾脏病（CKD）进展中起主要作用。本实验室 将受体激活的Smad锚（SARA）鉴定为候选抗纤维化分子。原本 SARA被描述为促进Smad信号传导的TGF-β受体接头分子，具有更广泛的 作为支架蛋白的作用，组装复合物中的分子以指导细胞信号事件。我们 已经表明SARA如何参与内体信号传导，并且它的表达有助于维持 处于分化状态的细胞。SARA在受到纤维化刺激的细胞中下调， 与呈现纤维化表型的细胞同时存在。在这些细胞中过度表达SARA 阻止与纤维化相关的表型转换;相反，敲低SARA会放大 胶原蛋白的产生。在初步研究中，我们发现：1）SARA表达是 在经历纤维化的肾脏中显著减少，2）马兜铃酸诱导的肾小管间质纤维化是 在以诱导方式过表达SARA的小鼠中减少，和3）过表达SARA防止 果蝇幼虫心肾管模型中的纤维化，其中纤维化是通过敲低 组蛋白修饰基因总之，这些数据支持SARA维持细胞在 抗纤维化状态。通过调节SARA和/或介导细胞凋亡的分子的表达， SARA行动，我们可以修改导致肾纤维化的事件。在此，我们提出三个具体的 目的是验证我们的假设，并将确定：（1）SARA表达在肾纤维化过程中的变化 在小鼠中，如果使用转基因方法增加或阻断SARA表达， 分别加速了疾病的发展。(2)在体外和体内纤维化过程中SARA表达是如何调节的 vivo.我们已经发现转录抑制因子BHLHE 40抑制SARA表达; 抗纤维化蛋白可溶性Klotho刺激SARA表达。我们将确定这些 分子通过SARA作用以影响纤维化肾病的结果。(3)SARA信号 下游保护细胞免受纤维化“开关”的影响。“我们将研究SARA如何影响Wnt/β- catenin信号通路，通过TGF-β处理的SARA的RNA-Seq寻找新的效应机制。 小鼠细胞和经历心包肾细胞相关纤维化的果蝇幼虫。 意义：完成这些研究将阐明SARA 调节细胞纤维化活性，目的是鉴定新的治疗靶点以预防或 慢性肾病相关纤维化。

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.