GALACTOSE AND N-ACETYLGALACTOSAMINE-SPECIFIC ENDOCYTOSIS OF GLYCOPEPTIDES BY ISOLATED RAT HEPATOCYTES
GALACTOSE AND N-ACETYLGALACTOSAMINE-SPECIFIC ENDOCYTOSIS OF GLYCOPEPTIDES BY ISOLATED RAT HEPATOCYTES
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DOI：
10.1016/0092-8674(80)90371-2
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发表时间：
1980-01-01
期刊：
影响因子：
64.5
通讯作者：
FIETE, D
中科院分区：
文献类型：
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作者：
BAENZIGER, JU;FIETE, D
在离体大鼠肝细胞系统中，研究了碘化糖蛋白和糖肽末端Gal或GalNAc部分的结合和摄取动力学。具有3个末端Gal残基的天冬酰胺连接的三触角复合寡糖以与无唾液酸-orosomucoid相同的动力学被内吞，而具有1个或2个末端Gal残基的双触角复合寡糖不被内吞。带有少至4个O-糖苷连接的Gal β 1，3GalNAc或GalNAc部分的糖肽也被快速内吞，而具有1或2个更紧密间隔的部分的糖肽不被内吞。所有的内吞糖蛋白和糖肽具有相似的表观解离常数和完整肝细胞表面上相似数量的结合位点。完整细胞质膜中受体的配体结合特性不同于溶解的受体，这表明与其他尚未确定的细胞组分的相互作用可能赋予区分密切相关的寡糖结构的能力。这与模型一致，其中仅具有落入受限空间关系内的末端Gal或GalNAc残基的糖肽可诱导发生摄取所需的受体构象改变。许多糖蛋白（如人无唾液酸铜蓝蛋白）的内吞作用可由具有适当结构的单一复合寡糖的存在来解释。
The kinetics of binding and uptake of iodinated glycoproteins and glycopeptides bearing terminal Gal or GalNAc moieties in an isolated rat hepatocyte system were examined. Asparagine-linked, triantennary complex oligosaccharides with 3 terminal Gal residues are endocytosed with the same kinetics as asialo-orosomucoid, whereas biantennary, complex oligosaccharides with 1 or 2 terminal Gal residues are not endocytosed. Glycopeptides bearing as few as 4 O-glycosidically-linked Gal.beta.1, 3GalNAc or GalNAc moieties are also rapidly endocytosed, while glycopeptides with 1 or 2 more closely spaced moieties are not endocytosed. All the endocytosable glycoproteins and glycopeptides have similar apparent dissociation constants and a similar number of binding sites on the surface of the intact hepatocyte. The ligand-binding properties of the receptor in the plasma membrane of intact cells differ from those of the solubilized receptor, suggesting interaction with other as yet undefined cellular components probably confers the ability to discriminate among closely related oligosaccharide structures. This is consistent with a model in which only glycopeptides bearing terminal Gal or GalNAc residues that fall within a restricted spatial relationship can induce a conformational alteration in the receptor which is required for uptake to occur. The endocytosis of a number of glycoproteins such as human asialo-ceruloplasmin can be accounted for by the presence of a single, complex oligosaccharide with the appropriate structure.