Scenario of the biosynthesis of glycosaminoglycans

硫酸化糖胺聚糖是蛋白聚糖的侧多糖链，其可大致分为硫酸乙酰肝素型和硫酸软骨素型，并调节多种信号蛋白分子的功能。然而，在该项目启动之前，这些聚糖的生物合成机制尚未得到很好的理解。因此，本项目的目的是澄清硫酸化糖胺聚糖的生物合成的情况。在项目期间，我们利用人、蝇和线虫的体内和体外系统阐明了生物合成机制的各个方面，包括链的起始、延伸、聚合和链长的调节，并完成了项目的目标。结果包括糖基转移酶，磺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，还证明了软骨素在C.通过RNAi方法，使用线虫的软骨素合酶和软骨素聚合因子的RNA，在线虫中表达。发现了由软骨素6-O-磺基转移酶缺乏引起的人类遗传疾病。另一方面，我们阐明了多效生长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突起生长的分子机制。硫酸软骨素作为病毒感染的受体发挥作用。还揭示了与生长因子多曲肽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重大影响。GlcAT-I-KO和EXTL 2-KO小鼠的持续分析也将证实这些硫酸化糖胺聚糖链功能的重要性。

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.