Cell and molecular biology of enzymes involved in branch formation of mucin-type sugar chains

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1. Regulation of oligosaccharide structures by core 2beta1,6 GlcNAc transferase (C2GnT) during lymphocyte activation : A human B lymphoblastic cell line, HuNS-1, was induced to express core 2 oligosaccharides by activation with IL-4. This induction was accompanied with increased expression of C2GnT activity and its mRNA.It is suggested, therefore, that the elevation of C2GnT may have some roles in the process of B cell activation.2. Expression of sialy Lewis X accompanied with branch formation of sugar chains and its corelation with adhesiveness to endothelial cells : The gene coding the enzyme involved in synthesis of polysialic acids was introduced to CHO cells expressing sialy Lewis X.This transfection resulted in the decreased expression of sialyl Lewis X and the reduced adhesion of the cells to E-selectin.3. Cloning of core 4beta1,6 GlcNAc transferase : The cDNA library was constructed from poly (A) + RNA of colon carcinoma LS174 cells. Then, several positive clones were obtained by cross hybridization, using homologous regions of the two beta1,6 GlcNAc transferases involved in synthesis of I antigenic determinant and core 2 oligosaccharide.4. Structure, function and biosynthesis of the sugar moieties expressed on the branched core : Cloning of CMP-NeuAc hydroxylase were successfully performed. The structures of sugar chains which may serve as ligands for T-cell adhesion molecule CD2 were characterized.