Studies on carbohydrate structures of plasma membrane blycoproteins in relation to the loss of cell adhesion.

测定了由组织形成细胞和非组织形成细胞制备的质膜糖蛋白的碳水化合物结构。结果表明，大鼠各组织主要含有双触角配合物型和高甘露糖型糖链，并以组织特异性的方式含有不同数量的三、四触角配合物型糖链、唾液酸糖链、焦糖糖链、半乳糖糖链、分割n -乙酰氨基葡萄糖糖链和乳胺聚糖糖链。对两种大鼠腹水肝癌细胞与正常肝脏进行比较，发现它们主要是三、四天线复合物型糖链以及与肝脏不同的重复结构。然而，一种失去细胞粘附并以单细胞形式存在的腹水肝癌细胞AH414，比肝脏和另一种保持部分细胞间粘附的腹水肝癌细胞AH7974表达的聚焦型杂交型糖链要多得多。用低密度WGA-Sepharose色谱柱分析与大鼠肝质膜和两种腹水肝癌相关的黏液型糖蛋白，发现AH414细胞中存在高度黏液化的黏液型糖链糖蛋白，但在肝脏和AH7974细胞中含量较少。它们的碳水化合物结构分别为GalNAc、Gal 1-GalNAc和Gal 1-(GlcNAc 1-)GalNAc。上述结果表明，质膜糖蛋白中出现杂交型糖链和高度唾液化的黏液型糖链可能与原组织形成细胞的细胞粘附丧失有关。在转化的细胞中，参与asn连接糖链和黏液型糖链合成的半乳糖转移酶活性较高，这可能反映了支链asn连接糖链和高度唾液化的簇状黏液型糖蛋白的合成增加。少

The carbohydrate structures of plasma membrane glycoproteins prepared from tissue forming cells and from non-tissue forming cells have been determined. The results showed that various tissues of rat contain mainly biantennary complex-type and high-mannose type sugar chains with different amounts of tri- and tetraantennary complex-type ones, of sialic acid, of fucose, of -galactose, of bisecting N-acetylglucosamine and of lactosaminoglycan in a tissue specific manner. When two rat ascites hepatoma cells were analyzed in comparison to normal livers, they were primarily tri- and tetraantennary complex-type sugar chains and those with a repeating structure which are different from that of livers. However, one ascites hepatoma cells, AH414, which lose cell adhesion and are present as single cells, expressed fucosyl hybrid-type sugar chains in much larger amount than livers and the other ascites hepatoma cells, AH7974, which maintain partial intercellular adhesion.When mucin-type glycoprotei … More ns associated with plasma membranes of liver and two ascites hepatoma of rat were analyzed by using a low density WGA-Sepharose column to which sialyl mucin-type glycoproteins preferentially bind, AH414 cells showed the presence of highly sialylated glycoprotein(s) with clusted mucin-type sugar chains, which were detected but in much lesser amount in liver and AH7974 cells. The carbohydrate structures of them were turned out to be GalNAc, Gal 1-GalNAc and Gal 1-(GlcNAc 1-)GalNAc.The above results indicated that the appearance of hybrid-type sugar chains as well as highly sialylated mucin-type sugar chains in plasma membrane glycoproteins may be related to the loss of cell adhesion of originally tissue forming cells. The activities of galactosyltransferases that are involved in the synthesis of Asn-linked and mucin-type sugar chains in the transformed cells were high, which probably may reflect the increased synthesis of branched Asn-linked sugar chains and of highly sialylated clustered mucin-type glycoproteins. Less