GLUCOSE UP-REGULATES EXPRESSION OF THE DIFFERENTIATION-ASSOCIATED BRUSH-BORDER BINDING-SITE FOR ENTEROTOXIGENIC ESCHERICHIA-COLI COLONIZATION FACTOR ANTIGEN-I IN CULTURED HUMAN ENTEROCYTE-LIKE CELLS

The association of enterotoxigenic Escherichia coli expressing coloniz ation factor antigen I (CFA/I) with the cultured human colon adenocarc inoma cell, a model of the mature enterocyte of the small intestine, i s dependent on the binding of CFA/I to a brush border-associated compo nent, Binding of the purified radiolabeled [I-125]CFA/I- and C-14-labe led CFA/I-positive bacteria could be displaced by an increasing concen tration of unlabeled CFA/I. Moreover, we showed that expression of the specific CFA/I binding developed as a function of cell differentiatio n in Caco-2 cells, whereas expression of the nonspecific binding did n ot, Expression of the brush border differentiation-associated componen t acting as a binding site for CFA/I was up-regulated by glucose, Inde ed, the enterocyte-like HT-29 glc(-) cell subpopulation not expressing the CFA/I binding site when cultured in dialyzed serum and hexose-fre e medium regained the ability to bind CFA/I when the cells were return ed to culture medium containing glucose; Furthermore, expression of th e brush border-associated CFA/I binding site in the enterocyte-like Ca co-2 cells was repressed when the cells were cultured in hexose-free c onditions.