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

1. 在淋巴细胞活化过程中，core 2beta1,6 GlcNAc转移酶（C2GnT）对低聚糖结构的调控：通过IL-4激活诱导人B淋巴母细胞HuNS-1表达core 2低聚糖。这种诱导伴随着C2GnT活性及其mRNA表达的增加。因此，提示C2GnT的升高可能在B细胞活化过程中起一定作用。sialyl Lewis X的表达伴随着糖链分支的形成及其与内皮细胞粘附性的相关性：将编码多唾液酸合成酶的基因引入表达sialy Lewis X的CHO细胞中，转染后sialyl Lewis X的表达降低，细胞对e -selectin的粘附性降低。核心4beta1,6 GlcNAc转移酶的克隆：利用结肠癌LS174细胞的poly (A) + RNA构建cDNA文库。然后，利用参与I抗原决定因子和core 2低聚糖合成的两个β 1,6 GlcNAc转移酶的同源区域进行交叉杂交，获得了多个阳性克隆。支核表达糖基的结构、功能和生物合成：成功克隆了CMP-NeuAc羟化酶。表征了可能作为t细胞粘附分子CD2配体的糖链结构。

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.