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Abstract：
Sprouty (Spry) and Spred proteins have been identified as closely related negative regulators of the receptor tyrosine kinase (RTK)-mediated MAPK pathway, inhibiting cellular proliferation, migration and differentiation in many systems. As the different members of this antagonist family are strongly expressed in the lens epithelium in overlapping patterns, in this study we used lens epithelial explants to examine the impact of these different antagonists on the morphologic and molecular changes associated with fibroblast growth factor (FGF)-induced lens fiber differentiation. Cells in lens epithelial explants were transfected using different approaches to overexpress the different Spry (Spry1, Spry2) and Spred (Spred1, Spred2, Spred3) members, and we compared their ability to undergo FGF-induced fiber differentiation. In cells overexpressing any of the antagonists, the propensity for FGF-induced cell elongation was significantly reduced, indicative of a block to lens fiber differentiation. Of these antagonists, Spry1 and Spred2 appeared to be the most potent among their respective family members, demonstrating the greatest block in FGF-induced fiber differentiation based on the percentage of cells that failed to elongate. Consistent with the reported activity of Spry and Spred, we show that overexpression of Spry2 was able to suppress FGF-induced ERK1/2 phosphorylation in lens cells, as well as the ERK1/2-dependent fiber-specific marker Prox1, but not the accumulation of β-crystallins. Taken together, Spry and Spred proteins that are predominantly expressed in the lens epithelium in situ, appear to have overlapping effects on negatively regulating ERK1/2-signaling associated with FGF-induced lens epithelial cell elongation leading to fiber differentiation. This highlights the important regulatory role for these RTK antagonists in establishing and maintaining the distinct architecture and polarity of the lens.
摘要：
Sprouty（Spry）和Spred蛋白已被确定为受体酪氨酸激酶（RTK）介导的MAPK途径的密切相关的负调节因子，抑制细胞增殖，在许多系统中迁移和分化。由于该拮抗剂家族的不同成员在晶状体上皮中以重叠模式强烈表达，在这项研究中,我们使用晶状体上皮外植体来研究这些不同拮抗剂对成纤维细胞生长因子(FGF)诱导的晶状体纤维分化相关的形态学和分子改变的影响.使用不同的方法转染晶状体上皮外植体中的细胞，以过度表达不同的Spry（Spry1，Spry2）和Spred（Spred1，Spred2，Spred3）成员，我们比较了它们经历FGF诱导的纤维分化的能力。在过表达任何拮抗剂的细胞中，FGF诱导的细胞伸长倾向显着降低，指示晶状体纤维分化的阻滞。在这些拮抗剂中，Spry1和Spred2似乎是各自家庭成员中最有效的，根据未能延长的细胞百分比，显示FGF诱导的纤维分化中最大的阻滞。与Spry和Spred的报告活动一致，我们显示过表达Spry2能够抑制FGF诱导的晶状体细胞ERK1/2磷酸化,以及ERK1/2依赖性纤维特异性标记Prox1，但不是β-晶状体蛋白的积累。一起来看,Spry和Spred蛋白主要在晶状体上皮原位表达，似乎对与FGF诱导的晶状体上皮细胞伸长相关的ERK1/2信号传导具有重叠作用，从而导致纤维分化。这突出了这些RTK拮抗剂在建立和维持晶状体的不同结构和极性中的重要调节作用。
