Stewart L A, van Driel I R, Toh B H, Gleeson P A
Department of Pathology and Immunology, Monash University Medical School, Melbourne, Victoria, Australia.
Glycobiology. 1999 Jun;9(6):601-6. doi: 10.1093/glycob/9.6.601.
The gastric H/K ATPase beta-subunit, an abundant glycoprotein of the secretory membranes of gastric parietal cells, is the major autoantigen recognized by human parietal cell autoantibodies in gastric autoimmunity. Our previous studies demonstrated that the human autoantibodies recognize the H/K ATPase beta-subunit from a number of species and that glycosylation of the beta-subunit with complex N-glycans is required for autoantibody binding. The N-glycans of the beta-subunit contain polylactosamine chains. The lactosamine chains of the rabbit beta-subunit are terminated with alpha-linked galactosyl residues (alpha-galactosyl epitope) (Tyagarajan et al., Biochemistry, 1996, 35, 3238-3246). Here we have investigated the expression of alpha-galactosyl epitopes on the H/K ATPase beta-subunit from a number of species. Using the alpha-galactosyl binding lectin, BS1-IB4, and naturally occurring anti-alpha-galactosyl antibodies, we have demonstrated that the rat H/K ATPase beta-subunit also contains terminal alpha-galactosyl residues, but not the beta-subunit from pig, dog, and mouse, indicating species-specific differences in the terminal saccharide sequences of the beta-subunit. We also investigated the potential contribution of the alpha-galactosyl epitopes to the binding by human sera. The reactivity of human pernicious anemia serum with gastric parietal cells could not be inhibited with saccharide inhibitors and, in addition, no binding was observed with normal human sera. We conclude that the H/K ATPase beta-subunit oligosaccharides from rabbit and rat are terminated with alpha-galactosyl epitopes, and although the presence of this epitope does not contribute to binding by human parietal cell autoantibodies at the concentrations routinely used, it is recommended that neither rat or rabbit stomachs be used for screening human sera.
胃H/K ATP酶β亚基是胃壁细胞分泌膜中一种丰富的糖蛋白，是胃自身免疫中人类壁细胞自身抗体识别的主要自身抗原。我们之前的研究表明，人类自身抗体可识别多种物种的H/K ATP酶β亚基，且β亚基与复杂N聚糖的糖基化是自身抗体结合所必需的。β亚基的N聚糖含有多乳糖胺链。兔β亚基的乳糖胺链以α连接的半乳糖基残基（α-半乳糖基表位）终止（Tyagarajan等人，《生物化学》，1996年，35卷，3238 - 3246页）。在此，我们研究了多种物种H/K ATP酶β亚基上α-半乳糖基表位的表达情况。使用α-半乳糖基结合凝集素BS1 - IB4和天然存在的抗α-半乳糖基抗体，我们证明大鼠H/K ATP酶β亚基也含有末端α-半乳糖基残基，但猪、狗和小鼠的β亚基则没有，这表明β亚基末端糖序列存在物种特异性差异。我们还研究了α-半乳糖基表位对人血清结合的潜在贡献。糖类抑制剂不能抑制人类恶性贫血血清与胃壁细胞的反应性，此外，正常人血清未观察到结合。我们得出结论，兔和大鼠的H/K ATP酶β亚基寡糖以α-半乳糖基表位终止，尽管在常规使用的浓度下该表位的存在对人类壁细胞自身抗体的结合没有贡献，但建议不要使用大鼠或兔的胃来筛选人血清。
