PREFERENTIAL INTERACTION OF E. COLI HEAT-LABILE TOXIN WITH ENTEROCYTE-LIKE DIFFERENTIATED HT-29 CELL LINE.
Galván Estela M, Monferran Clara G.
In this study we compared the interaction of cholera toxin (CT) and the type I heat-labile enterotoxin from Escherichia coli infecting human intestine (LT) with the enterocyte?like differentiated human colon adenocarcinoma HT-29 cell line. Differentiation was induced by growing undifferentiated HT-29 cells in RPMI medium. This process yield intercellular lumina bordered with brush-border microvilli observed by electrón microscopy and the expression of aminopeptidase N, sucrase, lactase, maltase and phosphatase alkaline activities. Differentiated HT-29 cells bound 18-fold more 125I-labeled LT than 125I-labeled CT. 125I-labeled LT binding to the cells was not significnatly reduced by preincubation with a CT-B excess but, on the contrary, 125I-labeled CT binding was abolished by preincubation with a LT-B excess. Helix pomatia lectin produced a dose-dependent inhibition of 125I-labeled LT interaction with differentiated HT-29 cells and no effect on 125I-labeled CT binding. A-blood group activity was detected on several glycolipids separated by TLC and two glycoproteins on western blot analysis. Only LTB was able to interact with A blood group-active glycolipids and an A-glycoprotein of about 230 kDa. These results indicate that although the ganglioside GM1 is the common receptor for CT and LT, LT interacted also with additional receptors not recognized by CT. In the enterocyte-like differentiated HT-29 cells glycoconjugates carrying A-blood group actvity could act as additional LT receptors.
