Differential expression of sucrase-isomaltase in clones isolated from early and late passages of the cell line Caco-2: evidence for glucose-dependent negative regulation.

The expression of the brush border-associated hydrolase sucrase-isomaltase was shown to increase from early to late passages of Caco-2 cells, concomitant with a decrease in the rates of glucose consumption. Twenty-six clones were isolated from early (P29) and late (P198) passages of the cell line. These clones show considerable and inverse differences in the levels of sucrase activities and rates of glucose consumption, without marked changes in other features of enterocytic differentiation of the cells (presence of an apical brush border, levels of expression of other brush border-associated hydrolases). Clones with low sucrase-isomaltase expression show a mosaic expression of the enzyme and a 38-fold higher rate of glucose consumption than clones with high sucrase-isomaltase expression. The clones with high expression show an homogeneous apical distribution of the enzyme and 70-fold and 35-fold higher levels of sucrase activities and sucrase-isomaltase mRNA, respectively. In contrast no differences were found from one clone to another in the enrichment of sucrase activity in brush border-enriched fractions as compared to cell homogenates. Switch to low glucose-containing medium (1 mM versus 25 mM in standard culture conditions) of cells with low sucrase-isomaltase results in an increased and more homogeneous expression of the enzyme and a tenfold augmentation of the levels of sucrase-isomaltase mRNA and sucrase activity. These results show that glucose interferes with the expression of sucrase-isomaltase in Caco-2 cells at the mRNA level.