posted on 2018-02-07, 00:00authored byAmberlyn
M. Wands, Jakob Cervin, He Huang, Ye Zhang, Gyusaang Youn, Chad A. Brautigam, Maria Matson Dzebo, Per Björklund, Ville Wallenius, Danielle K. Bright, Clay S. Bennett, Pernilla Wittung-Stafshede, Nicole S. Sampson, Ulf Yrlid, Jennifer J. Kohler
Cholera toxin (CT) enters host intestinal
epithelia cells, and
its retrograde transport to the cytosol results in the massive loss
of fluids and electrolytes associated with severe dehydration. To
initiate this intoxication process, the B subunit of CT (CTB) first
binds to a cell surface receptor displayed on the apical surface of
the intestinal epithelia. While the monosialoganglioside GM1 is widely
accepted to be the sole receptor for CT, intestinal epithelial cell
lines also utilize fucosylated glycan epitopes on glycoproteins to
facilitate cell surface binding and endocytic uptake of the toxin.
Further, l-fucose can competively inhibit CTB binding to
intestinal epithelia cells. Here, we use competition binding assays
with l-fucose analogs to decipher the molecular determinants
for l-fucose inhibition of cholera toxin subunit B (CTB)
binding. Additionally, we find that mono- and difucosylated oligosaccharides
are more potent inhibitors than l-fucose alone, with the
LeY tetrasaccharide emerging as the most potent inhibitor of CTB binding
to two colonic epithelial cell lines (T84 and Colo205). Finally, a
non-natural fucose-containing polymer inhibits CTB binding two orders
of magnitude more potently than the LeY glycan when tested against
Colo205 cells. This same polymer also inhibits CTB binding to T84
cells and primary human jejunal epithelial cells in a dose-dependent
manner. These findings suggest the possibility that polymeric display
of fucose might be exploited as a prophylactic or therapeutic approach
to block the action of CT toward the human intestinal epithelium.