Huet G, Hennebicq-Reig S, de Bolos C, Ulloa F, Lesuffleur T, Barbat A, Carrière V, Kim I, Real F X, Delannoy P, Zweibaum A
Unité de Recherches sur la Biologie et la Physiopathologie des Cellules Mucipares, Institut National de la Sante et de la Recherche Medicale (INSERM) U377, 59045 Lille Cedex, France.
J Cell Biol. 1998 Jun 15;141(6):1311-22. doi: 10.1083/jcb.141.6.1311.
Exposure for 24 h of mucus-secreting HT-29 cells to the sugar analogue GalNAc-alpha-O-benzyl results in inhibition of Galbeta1-3GalNAc:alpha2,3-sialyltransferase, reduced mucin sialylation, and inhibition of their secretion (Huet, G., I. Kim, C. de Bolos, J.M. Loguidice, O. Moreau, B. Hémon, C. Richet, P. Delannoy, F.X. Real., and P. Degand. 1995. J. Cell Sci. 108:1275-1285). To determine the effects of prolonged inhibition of sialylation, differentiated HT-29 populations were grown under permanent exposure to GalNAc-alpha-O-benzyl. This results in not only inhibition of mucus secretion, but also in a dramatic swelling of the cells and the accumulation in intracytoplasmic vesicles of brush border-associated glycoproteins like dipeptidylpeptidase-IV, the mucin-like glycoprotein MUC1, and carcinoembryonic antigen which are no longer expressed at the apical membrane. The block occurs beyond the cis-Golgi as substantiated by endoglycosidase treatment and biosynthesis analysis. In contrast, the polarized expression of the basolateral glycoprotein GP 120 is not modified. Underlying these effects we found that (a) like in mucins, NeuAcalpha2-3Gal-R is expressed in the terminal position of the oligosaccharide species associated with the apical, but not the basolateral glycoproteins of the cells, and (b) treatment with GalNAc-alpha-O-benzyl results in an impairment of their sialylation. These effects are reversible upon removal of the drug. It is suggested that alpha2-3 sialylation is involved in apical targeting of brush border membrane glycoproteins and mucus secretion in HT-29 cells.
将分泌黏液的HT - 29细胞暴露于糖类似物N - 乙酰半乳糖胺 - α - O - 苄基24小时，会导致β1,3 - 半乳糖基 - N - 乙酰半乳糖胺：α2,3 - 唾液酸转移酶受到抑制，黏蛋白的唾液酸化减少，以及其分泌受到抑制（Huet, G., I. Kim, C. de Bolos, J.M. Loguidice, O. Moreau, B. Hémon, C. Richet, P. Delannoy, F.X. Real., and P. Degand. 1995. J. Cell Sci. 108:1275 - 1285）。为了确定长期抑制唾液酸化的影响，将分化的HT - 29细胞群体在持续暴露于N - 乙酰半乳糖胺 - α - O - 苄基的条件下培养。这不仅导致黏液分泌受到抑制，还会使细胞显著肿胀，并使刷状缘相关糖蛋白如二肽基肽酶 - IV、黏蛋白样糖蛋白MUC1和癌胚抗原在胞质内小泡中积累，而这些蛋白不再在顶端膜表达。通过内切糖苷酶处理和生物合成分析证实，这种阻断发生在顺式高尔基体之后。相比之下，基底外侧糖蛋白GP 120的极化表达没有改变。在这些效应的背后，我们发现：（a）与黏蛋白一样，NeuAcα2 - 3Gal - R在与细胞顶端而非基底外侧糖蛋白相关的寡糖种类的末端位置表达；（b）用N - 乙酰半乳糖胺 - α - O - 苄基处理会导致其唾液酸化受损。去除药物后，这些效应是可逆的。有人提出，α2 - 3唾液酸化参与了HT - 29细胞中刷状缘膜糖蛋白的顶端靶向和黏液分泌。
