Graham Julie R, Williams Cara M M, Yang Zhiyong
Inflammation and Remodeling Research Unit, Pfizer, Inc., Cambridge, Massachusetts, 02140.
J Cell Biochem. 2014 Sep;115(9):1539-48. doi: 10.1002/jcb.24809.
Fibrosis is a chronic disease characterized by an excessive deposition of scar tissue in the affected organs. A central mediator of this process is transforming growth factor-β (TGF-β), which stimulates the production of extracellular matrix proteins such as collagens. MicroRNAs (miRNAs) have been implicated in both fibrosis as well as in TGF-β signaling, but the extent of their regulation has not been fully defined. A functional screen was conducted using a library of miRNA inhibitors to identify miRNAs that affect TGF-β-induced type I collagen expression, a key event in the development of fibrosis. The inhibition of one miRNA in particular, miR-27b, caused a significant increase in type I collagen expression. We found that miR-27b directly targets Gremlin 1 by binding to its 3'-UTR, reducing its mRNA levels. TGF-β signaling decreased miR-27b expression and caused a corresponding increase in Gremlin 1 levels, suggesting that TGF-β regulates Gremlin 1 expression in part by modulating miR-27b expression. Reducing Gremlin 1 levels by either siRNA-mediated gene silencing or by using the miR-27b mimic inhibited the expression of several genes known to be involved in fibrosis, while increasing Gremlin 1 levels by the addition of either recombinant protein or the miR-27b inhibitor enhanced the expression of these genes. In summary, we have demonstrated that miR-27b targets Gremlin 1, and that this regulation likely represents an important control point in fibrotic pathways.
纤维化是一种慢性疾病，其特征是在受影响的器官中过度沉积瘢痕组织。这一过程的核心介质是转化生长因子-β（TGF-β），它刺激细胞外基质蛋白如胶原蛋白的产生。微小RNA（miRNA）与纤维化以及TGF-β信号传导都有关联，但其调控程度尚未完全明确。使用miRNA抑制剂文库进行了功能筛选，以鉴定影响TGF-β诱导的I型胶原蛋白表达的miRNA，这是纤维化发展中的一个关键事件。特别是对一种miRNA，即miR-27b的抑制，导致I型胶原蛋白表达显著增加。我们发现miR-27b通过与Gremlin 1的3'-UTR结合直接靶向Gremlin 1，降低其mRNA水平。TGF-β信号传导降低了miR-27b的表达，并导致Gremlin 1水平相应增加，这表明TGF-β部分通过调节miR-27b的表达来调控Gremlin 1的表达。通过siRNA介导的基因沉默或使用miR-27b模拟物降低Gremlin 1水平可抑制几种已知参与纤维化的基因的表达，而通过添加重组蛋白或miR-27b抑制剂增加Gremlin 1水平则增强了这些基因的表达。总之，我们已经证明miR-27b靶向Gremlin 1，并且这种调控可能代表纤维化途径中的一个重要控制点。
