Institute for Molecular Science of Medicine, Aichi Medical University, Nagakute, Japan.
PLoS One. 2012;7(8):e43806. doi: 10.1371/journal.pone.0043806. Epub 2012 Aug 28.
Chondroitin sulfate (CS) is a linear polysaccharide consisting of repeating disaccharide units of N-acetyl-D-galactosamine and D-glucuronic acid residues, modified with sulfated residues at various positions. Based on its structural diversity in chain length and sulfation patterns, CS provides specific biological functions in cell adhesion, morphogenesis, neural network formation, and cell division. To date, six glycosyltransferases are known to be involved in the biosynthesis of chondroitin saccharide chains, and a hetero-oligomer complex of chondroitin sulfate synthase-1 (CSS1)/chondroitin synthase-1 and chondroitin sulfate synthase-2 (CSS2)/chondroitin polymerizing factor is known to have the strongest polymerizing activity. Here, we generated and analyzed CSS2(-/-) mice. Although they were viable and fertile, exhibiting no overt morphological abnormalities or osteoarthritis, their cartilage contained CS chains with a shorter length and at a similar number to wild type. Further analysis using CSS2(-/-) chondrocyte culture systems, together with siRNA of CSS1, revealed the presence of two CS chain species in length, suggesting two steps of CS chain polymerization; i.e., elongation from the linkage region up to Mr ∼10,000, and further extension. There, CSS2 mainly participated in the extension, whereas CSS1 participated in both the extension and the initiation. Our study demonstrates the distinct function of CSS1 and CSS2, providing a clue in the elucidation of the mechanism of CS biosynthesis.
硫酸软骨素 (CS) 是一种由 N-乙酰-D-半乳糖胺和 D-葡萄糖醛酸残基重复组成的线性多糖，在各种位置上带有硫酸化残基修饰。基于其在链长和硫酸化模式上的结构多样性，CS 在细胞黏附、形态发生、神经网络形成和细胞分裂中提供了特定的生物学功能。迄今为止，已知有六种糖基转移酶参与软骨素聚糖链的生物合成，并且已经知道硫酸软骨素合酶 1 (CSS1)/软骨素合酶 1 和硫酸软骨素合酶 2 (CSS2)/软骨素聚合因子的异源寡聚物复合物具有最强的聚合活性。在这里，我们生成并分析了 CSS2(-/-) 小鼠。尽管它们具有活力和生育能力，没有明显的形态异常或骨关节炎，但它们的软骨中含有 CS 链，其长度较短，数量与野生型相似。使用 CSS2(-/-) 软骨细胞培养系统以及 CSS1 的 siRNA 进行的进一步分析揭示了两种 CS 链长度的存在，表明 CS 链聚合有两个步骤；即在连接区延伸到 Mr∼10000，然后进一步延伸。在那里，CSS2 主要参与延伸，而 CSS1 参与延伸和起始。我们的研究表明 CSS1 和 CSS2 具有不同的功能，为阐明 CS 生物合成的机制提供了线索。
