维甲酸改变人肝癌细胞表面N－糖链的结构及其酶学机制

RETINOIC ACID CHANGES THE STRUCTURE OF N-GLYCAN ON THE SURFACE OF HUMAN HEPATOCARCINOMA CELL AND ITS ENZYMATIC MECHANISM

用３Ｈ－甘露糖标记７７２１人肝癌细胞表面糖蛋白的Ｎ－糖链，经提取和去唾液酸后，用ＣｏｎＡ和ＤＳＡ亲和柱顺序层析将３Ｈ－标记的Ｎ－糖链分成４个类型和天线数不同的组分来研究维甲酸（ＲＡ）对细胞表面Ｎ－糖链的影响。结果：１０μｍｏｌ／ＬＲＡ处理细胞３～５ｄ后，可使Ｃ２Ｃ２二天线复杂型Ｎ－糖链增加，而高甘露糖型及三、四天线，特别是带有Ｃ２，６分支结构的复杂型Ｈ－糖链减少。用ＬＣＡ亲和柱还证明二天线糖链中的核心岩藻糖也减少。进一步发现上述改变的酶学机制是ＲＡ降低Ｎ－乙酰氨基萄葡糖转移酶Ｖ和α－１，６－核心岩藻糖转移酶的活力。结论：ＢＡ通过改变某些糖基转移酶活力而改变细胞表面糖链结构，这可能是ＲＡ使７７２１细胞诱导分化的机理之－。

The N-glycans of glycoproteins on the surface of 7721human hepatocarcinoma cell were labeled with 3H-Mannose,The 3H-N-glycans were prepared from cell surface,desialylated,and subjected to sequential chromatography on con A and DSA affinity columns to separate the glycans into 4fractions with different type and antennary member in order to study the effect of retinoic acid(RA) on the structure of N-glycan on cell surface. It was found that the C2C2 biantennary complex type N-glycan was increased, but the high mannose type as weil as the triand tetra-antennary complex type,especially the C2,6 branched complex type N- glycans were decreased after the cells were treated with RA for 3 to 5 days. using LCA affinity column, it was also discovered that core fucose in the biantennary glycans were also decreased;Study on the enzymatic mechanism of the above mentioned changes were revealed in further to be the decrease of N-acetyl glucosaminyl transferase V and α-1, 6 core fucose transferase by RA. It can be concluded that RA changed the structure of cell surface N-glycans thorugh the changes of the activities of some glycosyl transferases and it was one of the mechanism that RA induced the differentiation of 7721 cells.