THE EMERGENCE OF A BASOLATERAL 1-DEOXYMANNOJIRIMYCIN-SENSITIVE MANNOSE CARRIER IS A FUNCTION OF INTESTINAL EPITHELIAL-CELL DIFFERENTIATION - EVIDENCE FOR A NEW INHIBITORY EFFECT OF 1-DEOXYMANNOJIRIMYCIN ON FACILITATIVE MANNOSE TRANSPORT

We have previously reported that 1-deoxymannojiri-mycin (dMM), a speci fic cy-mannosidase I inhibitor interfered with the uptake of D-[2-H-3] mannose in differentiated HT-29 cells (a cell line derived from a huma n colon adenocarcinoma) (Ogier Denis, E., Trugnan, G., Sapin, C., Aube ry, M., and Codogno, P. (1990) J. Biol. Chem. 265, 5366-5369). In the present work, we have used another cell line derived from a human colo n adenocarcinoma, Caco-2 cells, which has the capacity to grow and to dif ferentiate on porous filters. We have determined that mannose coul d enter the cells by two distinct transporters. One sensitive to dMM, present at the basolateral membrane of differentiated Caco-2 cells, an d one insensitive to the drug localized at the brush border membrane o f these cells. The basolateral mannose uptake is mediated by a Na+-ind ependent transporter whereas the apical entry of mannose is under the dependence of Na+. We have focused our studies on the basolateral dMM- sensitive mannose carrier. Kinetic studies indicated that this facilit ative mannose transporter has a K-m and a V-max of 55 +/- 8 mu m and 0 .144 +/- 0.005 mu mol/mg of protein/ min, respectively. This basolater al transporter is clearly distinct from facilitative glucose transport ers. Moreover, this dMM-sensitive mannose transport accurately follows the differentiation process of intestinal epithelial cells as well in vitro as shown using Caco-2 cells as in vivo when experiments were do ne on crypt cells and villus cells isolated from rat jejunum.