Glycosylation status of bone sialoprotein and its role in mineralization
Glycosylation status of bone sialoprotein and its role in mineralization
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骨唾液蛋白的糖基化状态及其在矿化中的作用
DOI：
10.1016/j.yexcr.2017.09.034
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发表时间：
2017
影响因子：
3.7
通讯作者：
Xiong Su
中科院分区：
文献类型：
--
作者：
Lan Xu;Zhenqing Zhang;Xue Sun;Jingjing Wang;Wei Xu;Lv Shi;Jiaojiao Lu;Juan Tang;Jingjing Liu;Xiong Su
高糖基化骨涎蛋白（BSP）是骨中含量丰富的非胶原蛋白，在体外和体内均能促进成骨细胞分化和新骨沉积。然而，其不同糖基化键的结构细节尚未得到很好的研究，它们在骨稳态中的功能也不清楚。先前的研究表明，BSP上的theo -聚糖高度唾液化，而非non -聚糖。本研究采用串联质谱法（MS/MS）证实重组人整合素结合唾液蛋白（rhiBSP）在其末端也富集于唾液酸（SAs）中。我们还发现了n -聚糖修饰的多个新位点。rhiBSP处理可增强MC3T3-E1细胞的成骨细胞分化和矿化，这种作用可通过有效的酶解其n -聚糖而部分逆转。去除末端的所有SAs对逆转rhiBSP对成骨的作用有更大的作用，尤其是对矿化的作用，这表明n -聚糖和do -聚糖末端的唾液化在这一调节中都起着重要作用。此外，bsp结合的SAs可能通过ERK激活VDR表达来影响矿化。综上所述，我们的研究结果确定了rhiBSP上富含SAs的新n -聚糖，并证明了n -和o -聚糖上的SAs对BSP调控体外成骨细胞分化和矿化都很重要。
The highly glycosylated bone sialoprotein (BSP) is an abundant non-collagenous phosphoprotein in bone which enhances osteoblast differentiation and new bone deposition in vitro and in vivo. However, the structural details of its different glycosylation linkages have not been well studied and their functions in bone homeostasis are not clear. Previous studies suggested that theO-glycans, but not theN-glycans on BSP, are highly sialylated. Herein, we employed tandem mass spectrometry (MS/MS) to demonstrate that theN-glycanson the recombinant human integrin binding sialoprotein (rhiBSP) are also enriched in sialic acids (SAs) at their termini. We also identified multiple novel sites ofN-glycan modification. Treatment of rhiBSP enhances osteoblast differentiation and mineralization of MC3T3-E1 cells and this effect could be partially reversed by efficient enzymatic removal of itsN-glycans. Removal of all terminal SAs has a greater effect in reversing the effect of rhiBSP on osteogenesis, especially on mineralization, suggesting that sialylation at the termini of bothN-glycans andO-glycans plays an important role in this regulation. Moreover, BSP-conjugated SAs may affect mineralization via ERK activation of VDR expression. Collectively, our results identified novelN-glycans enriched in SAs on the rhiBSP and demonstrated that SAs at bothN- andO-glycans are important for BSP regulation of osteoblast differentiation and mineralization in vitro.