Kay M M, Marchalonis J J, Hughes J, Watanabe K, Schluter S F
Department of Medicine, Texas A&M University, Temple 76503.
Proc Natl Acad Sci U S A. 1990 Aug;87(15):5734-8. doi: 10.1073/pnas.87.15.5734.
Senescent cell antigen (SCA), an aging antigen, is a protein that appears on old cells and marks them for removal by the immune system in mammals. It is derived from band 3, a ubiquitous membrane transport protein found in diverse cell types and tissues. We have used synthetic peptides to identify aging antigenic sites on band 3, using a competitive inhibition assay and immunoblotting with IgG directed against the aging antigen on old cells. Results indicate that: (i) the active antigenic sites of the aging antigen reside on membrane protein band 3 residues that are extracellular regions implicated in anion transport (residues 538-554 and 788-827); (ii) a putative ankyrin-binding-region peptide is not involved in SCA activity; and (iii) carbohydrate moieties are not required for the antigenicity or recognition of SCA because synthetic peptides alone abolish binding of senescent cell IgG to erythrocytes. One of the putative transport sites that contributes to the aging antigen is located toward the carboxyl terminus. A model of band 3 is presented. Localization of the active antigenic site on the band 3 molecule facilitates definition of the molecular changes occurring during aging that initiate molecular as well as cellular degeneration.
衰老细胞抗原（SCA）是一种衰老抗原，是一种出现在衰老细胞上并标记它们以便被哺乳动物免疫系统清除的蛋白质。它源自带3，一种在多种细胞类型和组织中普遍存在的膜转运蛋白。我们使用合成肽，通过竞争性抑制试验以及用针对衰老细胞上衰老抗原的IgG进行免疫印迹，来鉴定带3上的衰老抗原位点。结果表明：（i）衰老抗原的活性抗原位点位于膜蛋白带3的残基上，这些残基是参与阴离子转运的细胞外区域（残基538 - 554和788 - 827）；（ii）一个假定的锚蛋白结合区域肽不参与SCA活性；（iii）碳水化合物部分对于SCA的抗原性或识别不是必需的，因为单独的合成肽就能消除衰老细胞IgG与红细胞的结合。对衰老抗原有贡献的一个假定转运位点位于羧基末端附近。给出了带3的模型。带3分子上活性抗原位点的定位有助于确定衰老过程中发生的引发分子以及细胞退化的分子变化。
