Elimination of N-linked glycosylation sites from the human IgA1 constant region: effects on structure and function.
Elimination of N-linked glycosylation sites from the human IgA1 constant region: effects on structure and function.
复制标题
DOI：
10.4049/jimmunol.158.2.724
复制
发表时间：
1997-01
影响因子：
4.4
通讯作者：
P. D. Chuang;S. Morrison
中科院分区：
文献类型：
--
作者：
P. D. Chuang;S. Morrison
IgA 1 Ab在第二个C区和分泌的尾片段结构域中具有保守的N-连接糖基化位点。为了了解这些碳水化合物在人IgA 1的结构和功能中的作用，已经产生了产生缺乏一个或两个N-连接的碳水化合物位点的人IgA 1的定点突变体。当突变重链在产生相关κ-轻链的骨髓瘤细胞系中表达时，可以看到IgA 1的单体和二聚体形式的有效分泌。此外，存在缺乏第三结构域碳水化合物的伊加分子的较高聚合物形式，无论是单独的还是在双突变体中。对IgA 1蛋白的功能分析表明，各种突变体和野生型伊加之间存在显著差异。碳水化合物突变体显示出对它们的靶Ag（丹磺酰基）的亲和力降低。所有的IgA 1分子都保留了与多聚IG受体结合的能力。所有伊加分子均观察到C3结合，缺乏第三结构域碳水化合物的伊加突变体显示结合C3的能力降低;然而，伊加不能有效激活旁路途径，如通过因子B切割和末端复合物结合所确定的。这些研究表明，人IgA 1恒定区的N-连接糖基化在IgA 1的生物学特性中起着重要作用。
IgA1 Abs possess conserved N-linked glycosylation sites in the second C region and secreted tailpiece domains. To understand the role of these carbohydrates in the structure and function of human IgA1, site-directed mutants that produce human IgA1 lacking either one or both of the N-linked carbohydrate sites have been produced. When the mutant heavy chains are expressed in myeloma lines producing the relevant kappa-light chain, efficient secretion of the monomer and dimer forms of IgA1 is seen. In addition, higher polymer forms of the IgA molecules lacking the third domain carbohydrate, either singly or in the double mutant, are present. Functional analysis of the IgA1 proteins has shown significant differences between the various mutants and wild-type IgA. The carbohydrate mutants show a reduced affinity for their target Ag, dansyl. All of the IgA1 molecules retained the ability to bind to the polymeric Ig receptor. C3 binding was observed for all of the IgA molecules, with the IgA mutants lacking the third domain carbohydrate showing a reduced ability to bind C3; however, IgA did not effectively activate the alternative pathway, as determined by factor B cleavage and terminal complex binding. These studies demonstrate that N-linked glycosylation in the constant domain of human IgA1 plays an important role in the biologic properties of IgA1.