グライコミクスによる糖鎖遺伝子の細胞内ターゲット分子の同定

抄録

Recent progress of glycobiology has revealed that specific sugar chains on glycoproteins are concerned with cell adhesion, birth, differentiation and cancer metastasis. However, remodeling of cell surface proteins by glycosyltransferase genes (glycogenes), transgenic mice and even knock-out mice could not demonstrate real functions of oligosaccharide structures for each phenotype of glycosyltransferase transfectants, because many glycoproteins were glycosylated by glyco-genes. We should remember that glycoproteins modified with gene arrangement were not randomized but specific for each glycosyltransferase. In this study, we identified intracellular target proteins for glyco-genes using 2-dimensional electrophoresis followed by lectin blots. Used materials were transgenic mice of N-acetylglucosaminyltransferase III (GnT-III) and α1-6 fucosyltransferase (α1-6FucT) transfected Hep3B cells. GnT-III is involved in the synthesis of branching formation on N-glycans and α1-6FucT is involved in the attachment of fucose in the innermost GlcNAc on N-glycans. Treatment with diethylnitrosamine (DEN) of GnT-III transgenic and control mice brought tumor formation in the liver. The numbers of hepatic tumors were significantly smaller in GnT-III transgenic mice than in control mice. One of the target molecules for GnT-III in the serum of GnT-III transgenic mice was identified as haptoglobin. When α1-6FucT transfectants of Hep3B cells were injected into the spleen of athymic mice, tumor formation in the liver was dramatically suppressed as compared to their control cells. One of the causative molecules for this suppression of intrahepatic metastasis was identified as α5β1 integrin which is strongly α1-6 fucosylated. These approaches provide a new insight into glycobiology area and further functional glycomics would be required in the 21st century.