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

聚糖在神经系统和宿主防御系统中的作用研究。HNK-1抗原（SO_3-G1cA-LacNAc）在神经系统中的作用：克隆了两个与HNK-lepitope生物合成相关的葡萄糖醛酸转移酶（G1cAT-P和G1cAT-S）基因，并成功生成了它们的基因缺陷小鼠。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Morris水玉米试验中表现出Schaffer侧侧- ca1突触的长期增强减弱和空间记忆形成缺陷。这是第一个证明单个非还原末端碳水化合物残基的丧失会削弱大脑高级功能的证据。我们发现G1cAT-P和G1cAT-S的催化结构域在高尔基体中与硫转移酶（HNK-1 ST）形成功能复合物，促进了完整HNK-1抗原的顺序生物合成。此外，我们还测定了人类G1cAT-P和G1cAT-S的x射线晶体结构，并解释了这些酶仅以同型二聚体形式表达酶活性的原因。甘露聚糖结合蛋白MBP的内源性配体鉴定：我们之前注意到，通过MBP依赖性细胞介导的细胞毒性（MDCC），人类MBP基因在裸鼠中对人类结直肠癌SW 1116细胞表现出强大的生长抑制活性。我们成功地从SW1116细胞中分离出内源性配体聚糖，并与中央研究院的Kay-Hooi Khoo博士合作对其结构进行了表征。它们被证明是大的、多天线的n -聚糖，携带高度集中的聚乳胺型结构，有趣的是，在非还原末端，Le^b/Le^a或Le^a结构的串联重复序列普遍存在。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。我们还发现MBP特异性结合金属蛋白酶meprin α和β，它们在肾和小肠上皮细胞、白细胞和某些癌细胞中高度表达。有趣的是，MBP被发现可以抑制meprins的蛋白酶活性和基质降解活性，这表明MBP可能作为肿瘤进展的潜在治疗靶点。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