Roles of Heparan Sulfate Sulfation in Dentinogenesis
Roles of Heparan Sulfate Sulfation in Dentinogenesis
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DOI：
10.1074/jbc.m111.332924
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发表时间：
2012-04-06
影响因子：
4.8
通讯作者：
Yamashiro, Takashi
中科院分区：
文献类型：
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作者：
Hayano, Satoru;Kurosaka, Hiroshi;Yamashiro, Takashi
细胞表面硫酸肝素（HS）是细胞信号传导和发育的重要调节因子。HS在HS蛋白聚糖（HSPGs）的糖胺聚糖侧链中捕获信号分子，如Wnt，并调节其功能。巯基内酯酶Sulf1和Sulf2在细胞表面分泌，选择性地去除HSPGs上的6- o -硫酸盐基团，从而改变细胞表面HSPGs对其配体的亲和力。本研究为HSPG硫酸化和脱硫在牙本质形成中的功能作用提供了分子证据。我们发现，成牙细胞在细胞表面高度硫酸化，并在向成牙细胞分化的过程中发生脱硫，成牙细胞产生牙本质。Sulf1/Sulf2双零突变小鼠表现出较薄的牙本质基质和较短的根，并伴有编码牙本质特异性细胞外基质前体蛋白的牙本质唾液磷酸蛋白（Dspp） mRNA的表达减少，而单硫突变小鼠则不表现出这种缺陷表型。在成牙细胞细胞系中，Dspp mRNA的表达通过激活Wnt经典信号通路而增强。此外，HS磺化的药理干扰通过激活Wnt信号通路促进Dspp mRNA的表达。相反，Sulf的沉默会抑制Wnt信号通路，进而抑制Dspp mRNA的表达。我们还发现，在成牙细胞中，Wnt10a蛋白与细胞表面的HSPGs结合，干扰HS硫化降低了Wnt10a与HSPGs的结合亲和力，促进了Wnt10a与其受体的结合，增强了Wnt信号通路，从而上调了Dspp mRNA的表达。这些结果表明，硫介导的细胞HSPGs的脱硫是一种重要的修饰，对成牙本质细胞中Wnt信号的激活和牙本质基质的产生至关重要。
Cell surface heparan sulfate (HS) is an essential regulator of cell signaling and development. HS traps signaling molecules, like Wnt in the glycosaminoglycan side chains of HS proteoglycans (HSPGs), and regulates their functions. Endosulfatases Sulf1 and Sulf2 are secreted at the cell surface to selectively remove 6-O-sulfate groups from HSPGs, thereby modifying the affinity of cell surface HSPGs for its ligands. This study provides molecular evidence for the functional roles of HSPG sulfation and desulfation in dentinogenesis. We show that odontogenic cells are highly sulfated on the cell surface and become desulfated during their differentiation to odontoblasts, which produce tooth dentin. Sulf1/Sulf2 double null mutant mice exhibit a thin dentin matrix and short roots combined with reduced expression of dentin sialophosphoprotein (Dspp) mRNA, encoding a dentin-specific extracellular matrix precursor protein, whereas single Sulf mutants do not show such defective phenotypes. In odontoblast cell lines, Dspp mRNA expression is potentiated by the activation of the Wnt canonical signaling pathway. In addition, pharmacological interference with HS sulfation promotes Dspp mRNA expression through activation of Wnt signaling. On the contrary, the silencing of Sulf suppresses the Wnt signaling pathway and subsequently Dspp mRNA expression. We also show that Wnt10a protein binds to cell surface HSPGs in odontoblasts, and interference with HS sulfation decreases the binding affinity of Wnt10a for HSPGs, which facilitates the binding of Wnt10a to its receptor and potentiates the Wnt signaling pathway, thereby up-regulating Dspp mRNA expression. These results demonstrate that Sulf-mediated desulfation of cellular HSPGs is an important modification that is critical for the activation of the Wnt signaling in odontoblasts and for production of the dentin matrix.