Du Jun, Hong Senlian, Dong Lu, Cheng Bo, Lin Liang, Zhao Bing, Chen Ye-Guang, Chen Xing
From the State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China and.
the Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry and Molecular Engineering, Synthetic and Functional Biomolecules Center, and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China.
J Biol Chem. 2015 May 8;290(19):12000-13. doi: 10.1074/jbc.M115.636969. Epub 2015 Mar 25.
Epithelial-mesenchymal transition (EMT) is a fundamental process in embryonic development and organ formation. Aberrant regulation of EMT often leads to tumor progression. Changes in cell surface sialylation have recently been implicated in mediating EMT. Herein we report the visualization of dynamic changes of sialylation and glycoproteomic analysis of newly synthesized sialylated proteins in EMT by metabolic labeling of sialylated glycans with azides, followed by click labeling with fluorophores or affinity tags. We discovered that sialylation was down-regulated during EMT but then reverted and up-regulated in the mesenchymal state after EMT, accompanied by mRNA expression level changes of genes involved in the sialic acid biosynthesis. Quantitative proteomic analysis identified a list of sialylated proteins whose biosynthesis was dynamically regulated during EMT. Sialylation of cell surface adherent receptor integrin β4 was found to be down-regulated, which may regulate integrin functions during EMT. Furthermore, a global sialylation inhibitor was used to probe the functional role of sialylation during EMT. We found that inhibition of sialylation promoted EMT. Taken together, our findings suggest the important role of sialylation in regulating EMT and imply its possible function in related pathophysiological events, such as cancer metastasis.
上皮-间质转化（EMT）是胚胎发育和器官形成过程中的一个基本过程。EMT的异常调控常常导致肿瘤进展。细胞表面唾液酸化的变化最近被认为与介导EMT有关。在此，我们报告了通过用叠氮化物对唾液酸化聚糖进行代谢标记，随后用荧光团或亲和标签进行点击标记，来可视化EMT过程中唾液酸化的动态变化以及对新合成的唾液酸化蛋白进行糖蛋白质组分析。我们发现，在EMT过程中唾液酸化下调，但在EMT后的间充质状态下又恢复并上调，同时伴随着唾液酸生物合成相关基因的mRNA表达水平变化。定量蛋白质组分析确定了一系列在EMT过程中其生物合成受到动态调控的唾液酸化蛋白。发现细胞表面黏附受体整合素β4的唾液酸化下调，这可能在EMT过程中调节整合素功能。此外，使用一种全局唾液酸化抑制剂来探究唾液酸化在EMT过程中的功能作用。我们发现抑制唾液酸化会促进EMT。综上所述，我们的研究结果表明唾液酸化在调节EMT中起重要作用，并暗示其在相关病理生理事件（如癌症转移）中可能发挥的功能。
