Faculty of Medicine and Health Sciences, Department of Anatomy and Cell Biology, McGill University, Montreal, Canada.
Department of Natural Science, University of Lübeck, Lübeck, Germany.
FASEB J. 2021 May;35(5):e21598. doi: 10.1096/fj.202100282R.
Fibrillin-1 is an extracellular matrix protein which contains one conserved RGD integrin-binding motif. It constitutes the backbone of microfibrils in many tissues, and mutations in fibrillin-1 cause various connective tissue disorders. Although it is well established that fibrillin-1 interacts with several RGD-dependent integrins, very little is known about the associated intracellular signaling pathways. Recent published evidence identified a subset of miRNAs regulated by fibrillin-1 RGD-cell adhesion, with miR-1208 among the most downregulated. The present study shows that the downregulated miR-1208 controls fibroblast proliferation. Inhibitor experiments revealed that fibrillin-1 RGD suppressed miR-1208 expression via c-Src kinase and the downstream JNK signaling. Bioinformatic prediction and experimental target sequence validation demonstrated four miR-1208 binding sites on the ERK2 mRNA and one on the MEK1 mRNA. ERK2 and MEK1 are critical proliferation-promoting kinases. Decreased miR-1208 levels elevated the total and phosphorylated ERK1/2 and MEK1/2 protein levels and the phosphorylated to total ERK1/2 ratio. Together, the data demonstrate a novel outside-in signaling mechanism explaining how fibrillin-1 RGD-cell binding regulates fibroblast proliferation.
原纤维蛋白 1 是一种细胞外基质蛋白，含有一个保守的 RGD 整联蛋白结合基序。它构成了许多组织中微纤维的主干，原纤维蛋白 1 的突变导致各种结缔组织疾病。尽管已经证实原纤维蛋白 1 与几种依赖 RGD 的整联蛋白相互作用，但与之相关的细胞内信号通路却知之甚少。最近发表的证据确定了一组受原纤维蛋白 1 RGD-细胞黏附调节的 miRNAs，其中 miR-1208 下调最为明显。本研究表明，下调的 miR-1208 控制成纤维细胞的增殖。抑制剂实验表明，原纤维蛋白 1 RGD 通过 c-Src 激酶和下游 JNK 信号通路抑制 miR-1208 的表达。生物信息学预测和实验靶序列验证表明 ERK2 mRNA 上有四个 miR-1208 结合位点，MEK1 mRNA 上有一个 miR-1208 结合位点。ERK2 和 MEK1 是促进增殖的关键激酶。miR-1208 水平的降低增加了总 ERK1/2 和磷酸化 ERK1/2、MEK1/2 蛋白水平以及磷酸化 ERK1/2 与总 ERK1/2 的比值。总之，这些数据表明了一种新的由外向内的信号机制，解释了原纤维蛋白 1 RGD-细胞结合如何调节成纤维细胞的增殖。
