Dimerized Glycosaminoglycan Chains Increase FGF Signaling during Zebrafish Development
Dimerized Glycosaminoglycan Chains Increase FGF Signaling during Zebrafish Development
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DOI：
10.1021/cb400132r
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发表时间：
2013-05-01
影响因子：
4
通讯作者：
Kuberan, Balagurunathan
中科院分区：
文献类型：
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作者：
Nguyen, Thao K. N.;Tran, Vy M.;Kuberan, Balagurunathan
蛋白多聚糖(PG)通过其糖胺多聚糖(GAG)侧链与包括成纤维细胞生长因子(FGFs)在内的各种信号分子结合，调节发育过程中的多种信号通路。大多数PG具有两条或两条以上的GAG侧链，这表明GAG的多价性对于体内的生物学功能是必不可少的。然而，只有少数研究考察了GAG多价性的生物学意义。在这篇报道中，我们利用在同一支架上分别产生两条和三条GAG链的双木糖苷和三木糖苷的文库，从而模拟PGs，来研究GAG价态和链类型在调节斑马鱼体内FGF/FGFR相互作用中的重要性。一些双木糖苷和三木糖苷，但不是单木糖苷，在注入胚胎后引起伸长表型。原位杂交结果显示，在延长的胚胎中，成纤维细胞生长因子靶基因mkp3的表达增加，而其他途径的报告基因表达没有变化，表明成纤维细胞生长因子/成纤维细胞生长因子受体信号被特异性地过度激活。为了支持这一观察，延长可以被酪氨酸激酶抑制剂SU5402，FGFR拮抗剂Sprouty4的mRNA，或FGF8吗啉逆转。在木苷处理后，内源性GAG似乎没有受到影响，这表明这是一种功能获得表型。此外，含有Syndecan-1蛋白多糖的多价而不是单价GAG的表达概括了二价木糖苷观察到的伸长表型。基于这些体内实验结果，我们提出了一个新的GAG/FGF/FGFR相互作用模型，在该模型中，二聚化的GAG链可以激活成纤维细胞生长因子介导的信号转导通路。
Proteoglycans (PGs) modulate numerous signaling pathways during development through binding of their glycosaminoglycan (GAG) side chains to various signaling molecules, including fibroblast growth factors (FGFs). A majority of PGs possess two or more GAG side chains, suggesting that GAG multivalency is imperative for biological functions in vivo. However, only a few studies have examined the biological significance of GAG multivalency. In this report, we utilized a library of bis- and tris-xylosides that produce two and three GAG chains on the same scaffold, respectively, thus mimicking PGs, to examine the importance of GAG valency and chain type in regulating FGF/FGFR interactions in vivo in zebrafish. A number of bis- and tris-xylosides, but not mono-xylosides, caused an elongation phenotype upon their injection into embryos. In situ hybridization showed that elongated embryos have elevated expression of the FGF target gene mkp3 but unchanged expression of reporters for other pathways, indicating that FGF/FGFR signaling was specifically hyperactivated. In support of this observation, elongation can be reversed by the tyrosine kinase inhibitor SU5402, mRNA for the FGFR antagonist sprouty4, or FGF8 morpholino. Endogenous GAGs seem to be unaffected after xyloside treatment, suggesting that this is a gain-of-function phenotype. Furthermore, expression of a multivalent but not a monovalent GAG containing syndecan-1 proteoglycan recapitulates the elongation phenotype observed with the bivalent xylosides. On the basis of these in vivo findings, we propose a new model for GAG/FGF/FGFR interactions in which dimerized GAG chains can activate FGF-mediated signal transduction pathways.