The fucosylation and secretion of mucins synthesized in human bronchial cells vary according to growth conditions.
In order to evaluate the importance of an extracellular matrix on mucin secretion, human bronchial epithelial cells were cultured for 3 weeks on either plastic or type I collagen. By metabolically labeling cells with tritiated glucosamine, we found that cells grown on collagen secreted more radiolabeled mucins than cells grown on plastic, and their amount increased from week 1 to week 3 in both conditions. Secreted mucins were also assayed by ELISA using an anti-Lewis b monoclonal antibody. The amount of immunoreactive mucins secreted by cells grown on plastic during the first 2 weeks of culture was much lower than that of cells grown on collagen. This indicated that the expression of the Lewis b antigen on mucins secreted by cells grown on plastic was very low during the first 2 weeks of radiolabeling and increased during the third week to reach levels that were comparable to the levels of expression by cells grown on collagen. The expression of the Lewis b epitope and the mRNA level of fucosyltransferases FUT2 and FUT3, which are involved in Lewis b synthesis, varied in a similar way. The two fucosyltransferases were expressed later in cells cultured on plastic than in cells grown on collagen. These results suggest that growth conditions influence both the biosynthesis and secretion of respiratory mucins.