Functions of the HNK-1 antigen in the Nervous system and animal lectins in host defence system.

多聚糖在神经和宿主防御系统中的作用研究1。HNK-1抗原(SO_3-G1cA-LacNAc)在神经系统中的作用：克隆了与HNK-L表位生物合成相关的两个葡萄糖醛酸基转移酶基因(G1cAT-P和G1cAT-S)，并成功建立了其基因缺陷小鼠。G1cAT-P基因缺陷小鼠几乎完全失去了大脑中的HNK-1抗原。这些小鼠在Schaffer侧支-CA1突触的长时程增强减弱，在Morris水玉米测试中空间记忆形成存在缺陷。这是第一个证据表明，失去单一的非还原末端碳水化合物残基会削弱大脑的高级功能。我们发现G1cAT-P和G1cAT-S的催化结构域与高尔基体中的磺基转移酶(HNK1ST)形成了功能复合体，促进了完整HNK1抗原的顺序生物合成。此外，我们还测定了人G1cAT-P和G1cAT-S…的X射线晶体结构并解释为什么这些酶只以其同源二聚体的形式表达其酶活性。甘露聚糖结合蛋白内源性配体的鉴定：我们先前注意到，人MBP基因通过MBP依赖的细胞介导的细胞毒(MDCC)对裸鼠体内的人结肠癌SW1116细胞具有很强的生长抑制活性。我们成功地从SW1116细胞中分离出内源性配基多糖，并与中央研究院邱凯辉博士合作对其结构进行了表征。它们被证明是大的，携带高度岩藻糖化的聚乳糖胺型结构的多触角N-糖链，有趣的是，在非还原末端，Le^b/Le^a或Le^a结构的串联重复占优势。这些结构是独特的，与以前报道的肿瘤特异性碳水化合物抗原不同。我们还证明了金属蛋白结合金属蛋白酶α和β，这两种酶在肾和小肠上皮细胞、白细胞和某些癌细胞中高表达。有趣的是，MBP被发现抑制了MEPRINS的蛋白酶活性和基质降解活性，这表明MBP可能有助于肿瘤进展的潜在治疗靶点。较少

Studies on the roles of glycans in the nervous and host defence Systems.1. The role of HNK-1 antigen (SO_3-G1cA-LacNAc) in nervous system: Two glucuronyltransferase (G1cAT-P and G1cAT-S) genes associated with the biosynthesis of the HNK-lepitope were cloned and their gene-deficient mice were successfully generated. The G1cAT-P gene deficient mice lost the HNK-1 antigen in the brain almost completely. These mice exhibited reduced Long-term potentiation at the Schaffer collateral-CA1 synapses and a defect in spatial memory formation in the Morris water maize test. This is the first evidence that the loss of a single non-reducing terminal carbohydrate residue attenuates brain higher functions. We found that catalytic domains of G1cAT-P and G1cAT-S formed functional complexes with a sulfotransferase (HNK-1 ST) in the Golgi apparatus and facilitated the sequential biosynthesis of the complete HNK-1 antigen. Furthermore, we determined the x-ray crystal structures of human G1cAT-P and G1cAT-S … More and explain the reasons why these enzymes express their enzymic activity only in their homodimeric forms.2. Identification of endogenous ligands to mannan-binding protein, MBP: We previously noticed that the human MBP gene was shown to exhibit potent growth inhibitory activity toward human colorectal carcinoma, SW 1116 cells in nude mice via MBP-dependent cell-mediated cytotoxicity (MDCC). We successfully isolated the endogenous ligand glycans from SW1116 cells and their structures were characterized out in collaboration with Dr. Kay-Hooi Khoo in Academia Sinica. They were shown to be as large, multiantennary N-glycans carrying a highly fucosylated polylactosamine type structure and interestingly, at the nonreducing termini, Le^b/Le^a or tandem repeats of the Le^a structure prevail. These structures are unique and distinct from those of the previously reported tumor specific carbohydrate antigens. We also demonstrate that MBP binds specifically metalloproteases meprin α and β, which are highly expressed in kidney and small intestinal epithelial cells, leukocytes and certain cancer cells. Interestingly, MBP was found to inhibited the protease activity and matrix-degrading activity of meprins, suggesting the possibility that MBP may contribute as a potential therapeutic target to tumor progression. Less