Biological Regulation of GlcNAc cycle

我们提出了一个基本的范式“GlcNAc循环”，即活细胞调节多糖的生物合成和分解代谢，以响应病理变化。我们可以通过分析糖基化的每一步来掌握细胞的动态信息。用离子对高效液相色谱法同时测定核苷糖水平。代谢标记的核苷酸糖和N-和O-糖链的质量同位异体分析揭示了UDP-GlcNAc的代谢。我们还建立了一种检测各种GlcNAc转移酶活性的高效液相色谱方法，并在Neuro2a细胞中发现了GlcNAc转移酶-IX的内源性抑制因子(GnT-IX)。GnT-IX的脑特异性表达也受表观遗传组蛋白修饰的调节。此外，GnT-III补偿了核心岩藻糖功能的损失。这些数据表明，糖基化受细胞内GlcNAc代谢的多个阶段的调节。

We proposed a fundamental paradigm"GlcNAc cycle" that living cell regulates biosynthesis and catabolism of glycans in response to pathological changes. We could grasp the dynamic cellular information by analyzing the each step in glycosylation. Nucleotide sugars level were simultaneously determined by ion-pair HPLC. Mass isotopomer analysis of metabolically labeled nucleotide sugars and N- and O-glycans revealed the UDP-GlcNAc metabolisms. We also developed a HPLC method for various GlcNAc transferases activities, and found the endogenous inhibitory factor for GlcNAc transferase-IX (GnT-IX) in Neuro2a cells. Brain-specific expression of the GnT-IX was also regulated by epigenetic histone modifications. In addition, GnT-III compensated for the loss of core fucose functions. These data suggested that glycosylation is regulated by multiple stages in cellular GlcNAc metabolisms.