The cancer antigen CA125 represents a novel counter receptor for galectin-1
The cancer antigen CA125 represents a novel counter receptor for galectin-1
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DOI：
10.1242/jcs.00312
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发表时间：
2003-04-01
影响因子：
4
通讯作者：
Nickel, W
中科院分区：
文献类型：
--
作者：
Seelenmeyer, C;Wegehingel, S;Nickel, W
CA125是一种卵巢癌抗原，其最近阐明的一级结构表明CA125是一种存在于卵巢癌上的巨大粘蛋白样糖蛋白。肿瘤细胞的细胞表面。在这里，我们建立了 CA125 和 β-半乳糖苷结合细胞表面凝集素之间的功能联系，细胞表面凝集素是细胞外基质的成分，参与细胞粘附、细胞凋亡、细胞增殖和肿瘤进展的调节。在质谱和免疫学分析的基础上，我们发现CA125是galectin-1的反受体，因为来自HeLa细胞裂解物的CA125的可溶性片段和膜相关片段均显示出与人galectin-1高效特异性结合。这种相互作用被证明 (1) 取决于 CA125 的 β-半乳糖封端、O 连接的寡糖链，(2) 与 galectin-3 相比，galectin-1 更受青睐，(3) 受到表达 CA125 的细胞背景的调节。尽管缺乏传统的信号肽，由 1148 个氨基酸组成的 CA125 C 端片段（占全长蛋白质的不到 10%）保留了整合到内质网 (ER) 和高尔基体等分泌膜中的能力，并通过传统的分泌转运靶向质膜。正如一种重建非常规分泌的新测定所证明的那样。基于荧光激活细胞分选 (FACS) 的 galectin-1 分析，我们发现表达内源性 CA125 的肿瘤来源的 HeLa 细胞在其表面呈现的 galectin-1 数量是非肿瘤来源的 CA125 缺陷的 CHO 细胞的十倍以上。有趣的是，CHO 和 HeLa 细胞中的 galectin-1 表达水平和 galectin-1 的细胞表面结合能力相似，表明 CA125 可能是参与调节 galectin-1 向细胞表面输出的因子。
CA125 is an ovarian cancer antigen whose recently elucidated primary structure suggests that CA125 is a giant mucin-like glycoprotein present on. the cell surface of tumor cells. Here, we establish a functional link between CA125 and beta-galactoside-binding, cell-surface lectins, which are components of the extracellular matrix implicated in the regulation of cell adhesion, apoptosis, cell proliferation and tumor progression. On the basis of mass spectrometry and immunological analyses, we find that CA125 is a counter receptor for galectin-1, as both soluble and membrane-associated fragments of CA125 derived from HeLa cell lysates are shown to bind specifically to human galectin-1 with high efficiency. This interaction is demonstrated (1) to depend on beta-galactose-terminated, O-linked oligosaccharide chains of CA125, (2) to be preferential for galectin-1 versus galectin-3 and (3) to be regulated by the cellular background in which CA125 is expressed. Despite lacking a conventional signal peptide, a CA125 C-terminal fragment of 1148 amino acids, representing less than 10% of the full-length protein, retains the ability to integrate into secretory membranes such as the endoplasmic reticulum (ER) and the Golgi, and is targeted to the plasma membrane by conventional secretory transport. As demonstrated by a novel assay that reconstitutes non-conventional secretion. of galectin-1 based on fluorescence-activated cell sorting (FACS), we find that tumor-derived HeLa cells expressing endogenous CA125 present more than ten times as much galectin-1 on their surface compared with non-tumor-derived, CA125-deficient CHO cells. Intriguingly, both the galectin-1 expression level and the cell-surface binding capacity for galectin-1 are shown to be similar in CHO and HeLa cells, suggesting that CA125 might be a factor involved in the regulation of galectin-1 export to the cell surface.