Integrated analyses of biological functions of sugar chains : Glycomics

为了通过综合分析了解糖链的生物学功能，我们鉴定了以下特异性糖基转移酶的靶糖蛋白：GnT-V催化β 1-6 GlcNAc分支的合成，该分支参与肿瘤的转移和侵袭。在这个项目中，我们鉴定了间质蛋白酶作为GnT-V的靶分子，其可以激活uPA和HGF。在matriptase上添加β 1 -6 GlcNAc分支会延长这些蛋白的降解，导致裸鼠实验中的肿瘤转移。钙粘蛋白和整合素是GnT-III的靶分子，GnT-III参与合成二等分GlcNAc结构。二等分GlcNAc通过GnT-V或GnT-IV抑制N-聚糖延伸的进一步加工。在这个项目中，糖链对整合素和ECM相互作用的生物学功能被阐明为纯化分子的水平。钙粘蛋白/β连环蛋白系统也受GnT-III调节。β-连环蛋白的磷酸化被GnT-III抑制，e-钙粘蛋白的表达由GnT-IIIFut控制，8参与N-聚糖上的核心岩藻糖基化。为了解Fut 8基因的生理学意义，我们建立了Fut 8基因缺陷小鼠模型。这种小鼠表现出严重的生长迟缓，70%的小鼠在出生后3天内死亡。有趣的是，病理学分析显示小鼠肺气肿样病变。这种变化的机制是由于TGF β受体的失调，导致MMP表达增加。

To know biological functions of sugar chain by integrated analyses, we have identified target glycoproteins of specific glycosyltransferases as follows.GnT-V catalyses the synthesis of beta 1-6 GlcNAc branching which involves inn tumor metastasis and invasion. In this project, we identified matriptase as a target molecule of GnT-V, which can activate uPA, and HGF. Addition of betal-6 GlcNAc branching on matriptase brought prolonged degradation of these proteins, leading to tumor metastasis in nude mice experiments.Cadherin and integrin are target molecules for GnT-III which involves in the synthesis of bisecting GlcNAc structure. Bisecting GlcNAc inhibit further processing of N-glycan elongation via GnT-V or GnT-IV. In this project, biological functions of sugar chains on integrin and ECM interaction were clarified as a level of purified molecules. Cadherin/beta catenin system is also regulated by GnT-III. Phosphorylation of beta-catenin is suppressed by GnT-III and expression of e-cadherin is controlled by GnT-IIIFut8 involves in core fucosylation on N-glycans. To know physiological meaning of Fut8, we established Fut8 deficient mice. This mouse shows severe growth retardation and 70% of mice die within 3 days after birth. Interestingly, pathological analysis showed emphysema-like lesion in lung of the mice. The mechanism underlying this change is due to dys-regulation of TGF beta-receptor, leading to increases in MMP expression.