Specific secretion of gel-forming mucins and TFF peptides in HT-29 cells of mucin-secreting phenotype

Trefoil factor family (TFF) peptides are typical secretory products of muci n-producing cells, e.g. of the gastrointestinal tract. Here, the expression and secretion of mucins and TFF peptides was studied in the MT-29 cell lin e throughout cellular growth and differentiation in relation to a mucin-sec reting (HT-29 MTX) or an enterocyte-like (HT-29 G) phenotype. mRNAs of seve ral MUC and TFF genes were expressed in both cell subpopulations. However, for most MUC and TFF genes, the expression appeared strongly induced with t he differentiation into the mucin-secreting phenotype. On the other hand, T FF2 was specifically expressed in the mucin-secreting MT-29 MTX cells. The differentiation of MT-29 MTX cells into the mucin-secreting phenotype was c haracterised by secretion of the gel-forming mucins MUC2, MUC5AC, and MUC5B , however, according to a different pattern in the course of differentiatio n. A significant amount of TFF1 and TFF3 was secreted after differentiation , also according to a different pattern, whereas TFF1 was only faintly dete cted. Secretagogues, known to induce the secretion of mucus, increased the secretion of all three TFF peptides. In contrast, neither a secretory mucin nor a TFF peptide was found in the culture medium of MT-29 G cells. Overla y assays indicated that MT-29 MTX mucins bound to secretory peptides of MT- 29 MTX cells with relative molecular mass similar to TFF peptides. TFF1 and TFF3 were specifically localised in the mucus layer of HT-29 MTX cells by confocal microscopy. Finally, the secretion of TFF peptides and mucins appe ars as a co-ordinated process which only occurs after differentiation into goblet cell-like phenotype. (C) 2001 Elsevier Science B.V. All rights reser ved.