Nishihara Shoko, Iwasaki Hiroko, Nakajima Kazuyuki, Togayachi Akira, Ikehara Yuzuru, Kudo Takashi, Kushi Yasunori, Furuya Akiko, Shitara Kenya, Narimatsu Hisashi
Division of Cell Biology, Institute of Life Science, Soka University, Tangi-cho, Hachioji, Tokyo 192-8577, Japan.
Glycobiology. 2003 Jun;13(6):445-55. doi: 10.1093/glycob/cwg048. Epub 2003 Feb 20.
The expression of the Lewis X (Lex) carbohydrate structure in brain is developmentally regulated and is thought to play a role in cell-cell interaction during neuronal development. Mice possess three functional alpha1,3-fucosyltransferase genes: Fut4, Fut7, and Fut9. Fut7 is known to have no activity to synthesize Lex. In the present study, the relative activities of Fut4 and Fut9 for Lex synthesis were determined using recombinant enzymes. Fut9 exhibited very strong activity for oligosaccharide acceptors and glycolipid acceptors, that is, more than 10- and 100-fold, respectively, than that of Fut4. Furthermore, both cerebrum and cerebellum at various stages of development (E17, P0, P7, P30, P100) expressed 15-100 times more Fut9 transcript than Fut4 transcript. Neurons and astrocytes in primary culture also expressed 10-15 times more Fut9 than Fut4 transcript. Moreover, alpha1,3-Fut activity toward a polylactosamine chain in homogenates of brain tissues and primary cultured cells showed a pattern typical of Fut9, not Fut4. The developmental profile of activity for the synthesis of Lex was well correlated with that of Fut9 transcript. Immunohistochemistry with anti-Fut9 monoclonal antibody revealed the distribution of the Lex structure. These results showed that Fut9 is the most responsible enzyme for the synthesis of Lex in brain.
路易斯X（Lex）碳水化合物结构在大脑中的表达受到发育调控，并且被认为在神经元发育过程中的细胞间相互作用中发挥作用。小鼠拥有三个功能性α1,3-岩藻糖基转移酶基因：Fut4、Fut7和Fut9。已知Fut7没有合成Lex的活性。在本研究中，使用重组酶测定了Fut4和Fut9合成Lex的相对活性。Fut9对寡糖受体和糖脂受体表现出非常强的活性，分别比Fut4的活性高10倍和100倍以上。此外，在发育的各个阶段（E17、P0、P7、P30、P100），大脑和小脑表达的Fut9转录本比Fut4转录本多15 - 100倍。原代培养的神经元和星形胶质细胞表达的Fut9也比Fut4转录本多10 - 15倍。此外，脑组织和原代培养细胞匀浆中针对聚乳糖胺链的α1,3-Fut活性呈现出典型的Fut9模式，而非Fut4模式。Lex合成活性的发育谱与Fut9转录本的发育谱高度相关。用抗Fut9单克隆抗体进行免疫组织化学分析揭示了Lex结构的分布。这些结果表明，Fut9是大脑中合成Lex的最主要负责酶。
