Göttke M U, Keller K, Belley A, Garcia R M, Hollingsworth M A, Mack D R, Chadee K
Institute of Parasitology, McGill University, Québec, Canada.
J Eukaryot Microbiol. 1998 Mar-Apr;45(2):17S-23S. doi: 10.1111/j.1550-7408.1998.tb04519.x.
Mucins secreted from the gastrointestinal epithelium from the basis of the adherent mucus layer which is the host's first line of defense against invasion by Entamoeba histolytica. Galactose and N-acetyl-D-galactosamine residues of mucins specifically inhibit binding of the amebic 170 kDa heavy subunit Gal-lectin to target cells, an absolute prerequisite for pathogenesis. Herein we characterized the secretory mucins isolated from the human colon and from three human colonic adenocarcinoma cell lines: two with goblet cell-like (LS174T and T84) and one with absorptive cell-like morphology (Caco-2). By Northern blot analysis the intestinal mucin genes MUC2 and MUC3 were constitutively expressed by confluent LS174T and Caco-2 cells, whereas T84 cells only transcribed MUC2 and not MUC3 mRNA. 3H-glucosamine and 3H-threonine metabolically labeled proteins separated as high M, mucins in the void (Vo > 10(6) Da) of Sepharose-4B column chromatography and remained in the stacking gel of SDS-PAGE as depicted by fluorography. All mucin preparations contained high amounts of N-acetyl-glucosamine, galactose, N-acetyl-galactosamine, fucose and sialic acid, saccharides typical of the O-linked carbohydrate side chains. Mucin samples from the human colon and from LS174T and Caco-2 cells inhibited E. histolytica adherence to chinese hamster ovary cells, whereas mucins from T84 cells did not. These results suggest that genetic heterogeneity and/or posttranslational modification in glycosylation of colonic mucins can affect specific epithelial barrier function against intestinal pathogens.
胃肠道上皮分泌的黏蛋白构成了黏附性黏液层的基础，该黏液层是宿主抵御溶组织内阿米巴侵袭的第一道防线。黏蛋白的半乳糖和N-乙酰-D-半乳糖胺残基可特异性抑制阿米巴170 kDa重亚基半乳糖凝集素与靶细胞的结合，这是发病机制的绝对必要条件。在此，我们对从人结肠和三种人结肠腺癌细胞系中分离出的分泌性黏蛋白进行了表征：两种具有杯状细胞样形态（LS174T和T84），一种具有吸收细胞样形态（Caco-2）。通过Northern印迹分析，汇合的LS174T和Caco-2细胞组成性表达肠道黏蛋白基因MUC2和MUC3，而T84细胞仅转录MUC2，不转录MUC3 mRNA。经3H-葡萄糖胺和3H-苏氨酸代谢标记的蛋白质在Sepharose-4B柱色谱的空体积（Vo > 10(6) Da）中作为高分子量黏蛋白分离，并如荧光显影所示保留在SDS-PAGE的堆积胶中。所有黏蛋白制剂都含有大量的N-乙酰葡糖胺、半乳糖、N-乙酰半乳糖胺、岩藻糖和唾液酸，这些都是O-连接碳水化合物侧链特有的糖类。来自人结肠以及LS174T和Caco-2细胞的黏蛋白样品可抑制溶组织内阿米巴对中国仓鼠卵巢细胞的黏附，而来自T84细胞的黏蛋白则不能。这些结果表明，结肠黏蛋白糖基化的遗传异质性和/或翻译后修饰可能会影响针对肠道病原体的特定上皮屏障功能。
