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

从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已经被确定。结果表明，大鼠不同组织中主要含有双触角复合型和高甘露糖型糖链，并含有不同数量的三触角和四触角复合型糖链、唾液酸糖链、岩藻糖链、半乳糖糖链、二等分N-乙酰氨基葡萄糖链和乳糖胺聚糖糖链，且具有组织特异性。当两个大鼠腹水肝癌细胞进行了分析，与正常肝脏相比，它们主要是三和四触角复合型糖链和那些具有重复结构，这是不同的肝脏。然而，一种腹水肝癌细胞AH 414失去细胞粘附并以单细胞存在，其表达的岩藻糖基杂交型糖链的量远远大于肝脏和另一种腹水肝癌细胞AH 7974，其保持部分细胞间粘附。 ...更多信息 用唾液酸粘蛋白型糖蛋白优先结合的低密度WGA-Sepharose柱分析了大鼠肝细胞和两个腹水肝癌细胞质膜上的糖蛋白。AH 414细胞中存在高度唾液酸化的粘蛋白型糖蛋白，其糖链呈团簇状，但在肝细胞和AH 7974细胞中的含量要少得多。糖链结构分别为GalNAc、Gal 1-GalNAc和Gal 1-（GlcNAc 1-）GalNAc，表明质膜糖蛋白中的杂合型糖链和高唾液酸化粘蛋白型糖链的出现可能与原组织形成细胞的细胞粘附功能丧失有关。半乳糖基转移酶的活动，参与合成的天冬氨酸连接和粘蛋白型糖链的转化细胞是高的，这可能反映了增加的合成分支天冬氨酸连接的糖链和高度唾液酸化的簇粘蛋白型糖蛋白。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