Discipline of Anatomy and Histology, Bosch Institute, University of Sydney, NSW, Australia.
Gene & Stem Cell Therapy Program, Centenary Institute, Camperdown, NSW, Australia; Sydney Medical School, University of Sydney, NSW, Australia.
Exp Eye Res. 2018 May;170:148-159. doi: 10.1016/j.exer.2018.02.025. Epub 2018 Mar 1.
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.
芽蛋白（Sprouty）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剂，在许多系统中抑制细胞增殖、迁移和分化。由于这个拮抗剂家族的不同成员在晶状体上皮中以重叠的模式强烈表达，因此在本研究中，我们使用晶状体上皮外植体来研究这些不同的拮抗剂对与碱性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和分子变化的影响。使用不同的方法转染晶状体上皮外植体中的细胞，以过表达不同的 Sprouty（Sprouty1、Sprouty2）和 Spred（Spred1、Spred2、Spred3）成员，并比较它们诱导 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 诱导的细胞伸长的倾向明显降低，表明对晶状体纤维分化的阻断。在这些拮抗剂中，Sprouty1 和 Spred2 似乎在它们各自的家族成员中最有效，基于未能伸长的细胞的百分比，表现出对 FGF 诱导的纤维分化的最大阻断。与报道的 Sprouty 和 Spred 的活性一致，我们表明 Sprouty2 的过表达能够抑制晶状体细胞中 FGF 诱导的 ERK1/2 磷酸化，以及 ERK1/2 依赖性纤维特异性标志物 Prox1，但不能积累β-晶状体蛋白。总之，主要在原位晶状体上皮中表达的 Sprouty 和 Spred 蛋白似乎对负调控与 FGF 诱导的晶状体上皮细胞伸长相关的 ERK1/2 信号具有重叠的作用，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独特的结构和极性方面的重要调节作用。
