Scenario of the biosynthesis of glycosaminoglycans

硫酸化糖胺聚糖是蛋白聚糖的侧多糖链，大致可分为硫酸肝素型和硫酸软骨素型，调节多种信号蛋白分子的功能。然而，在该项目启动之前，对这些聚糖的生物合成机制还没有很好的了解。因此，本项目的目的是阐明生物合成硫酸化糖胺聚糖的情况。在项目期间，我们利用人、蝇和线虫的体内和体外系统，明确了包括链起始、延伸、聚合和链长调控在内的各个方面的生物合成机制，完成了项目的目标。结果包括糖基转移酶、硫基转移酶和调节因子的鉴定以及这些酶和因子的分子相互作用。此外，通过rna干扰技术，利用线虫的软骨素合成酶和软骨素聚合因子的rna，证实了软骨素在线虫的细胞分裂中是必不可少的。发现了一种由缺乏软骨素6- o -硫转移酶引起的人类遗传疾病。另一方面，我们阐明了多营养因子和肝细胞生长因子通过与细胞外基质中硫酸软骨素链的特异性相互作用促进小鼠海马神经元神经突生长的分子机制。硫酸软骨素也被证明是病毒感染的受体。还揭示了与生长因子pleiotrohin和一些细胞因子相互作用所需的糖序列。这些结果不仅对糖生物学领域，而且对其他相关领域产生了相当大的影响。正在进行的GlcAT-I-KO和extl2 - ko小鼠的分析也将证实这些硫酸化糖胺聚糖链的功能的重要性。

Sulfated glycosaminoglycans, which are side polysaccharide chains of proteoglycans, can be largely classified into a heparan sulfate type and a chondroitin sulfate type, and regulate functions of a wide variety of signaling protein molecules. However, the biosynthetic mechanism of these glycans had not been well understood before this project was launched. Therefore, the aim of this project was to clarify the scenario of the biosynthesis of sulfated glycosaminoglycans. During the project period, we clarified various aspects of the biosynthetic mechanism including the chain initiation, elongation, polymerization and the regulation of the chain length using the in vivo and in vitro systems of human, fly and nematode, and accomplished the aim of the project. The results included identification of glycosyltransferases, sulfotransferases and regulatory factors as well as molecular interactions of these ensymes and factors. Furthermore, it was demonstrated that chondroitin is essential in the cell division of C. elegans by the RNAi approach using the RNAs of the chondroitin synthase and the chondroitin polymerizing factor of the namatode. A human genetic disease caused by a deficiency of a chondroitin 6-O-sulfotransferase was discovered. On the other hand we clarified the molecular mechanism whereby the neurite outgrowth of mouse hippocampal neurons is promoted by pleiotrophin and hepatocyte growth factor through specific interactions with chondoitin sulfate chains in the extracellular matrices. It was also proved that chondroitin sulfate plays a role as a receptor for virus infection. The sugar sequences required for the interactions with a growth factor pleiotrohin and a few cytokines were also revealed. These results have started influencing considerably not only the glycobiology field but also other related fields. The on-going analysis of the GlcAT-I-KO and EXTL2-KO-mice will also confirm the importance of the functions of these sulfated glycosaminoglycan chains.