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Fucose-Galactose Polymers Inhibit Cholera Toxin Binding to Fucosylated Structures and Galactose-Dependent Intoxication of Human Enteroids
Version 3 2020-03-19, 17:45
Version 2 2020-03-19, 14:04
Version 1 2020-03-12, 08:29
journal contribution
posted on 2020-03-19, 17:45 authored by Jakob Cervin, Andrew Boucher, Gyusaang Youn, Per Björklund, Ville Wallenius, Lynda Mottram, Nicole S. Sampson, Ulf YrlidA promising strategy to limit cholera
severity involves blockers
mimicking the canonical cholera toxin ligand (CT) ganglioside GM1.
However, to date the efficacies of most of these blockers have been
evaluated in noncellular systems that lack ligands other than GM1.
Importantly, the CT B subunit (CTB) has a noncanonical site that binds
fucosylated structures, which in contrast to GM1 are highly expressed
in the human intestine. Here we evaluate the capacity of norbornene
polymers displaying galactose and/or fucose to block CTB binding to
immobilized protein-linked glycan structures and also to primary human
and murine small intestine epithelial cells (SI ECs). We show that
the binding of CTB to human SI ECs is largely dependent on the noncanonical
binding site, and interference with the canonical site has a limited
effect while the opposite is observed with murine SI ECs. The galactose–fucose
polymer blocks binding to fucosylated glycans but not to GM1. However,
the preincubation of CT with the galactose–fucose polymer only
partially blocks toxic effects on cultured human enteroid cells, while
preincubation with GM1 completely blocks CT-mediated secretion. Our
results support a model whereby the binding of fucose to the noncanonical
site places CT in close proximity to scarcely expressed galactose
receptors such as GM1 to enable binding via the canonical site leading
to CT internalization and intoxication. Our finding also highlights
the importance of complementing CTB binding studies with functional
intoxication studies when assessing the efficacy inhibitors of CT.
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block CTB bindinglimit cholera severityganglioside GM 1.GM 1. Importantlynoncanonical site places CTintestine epithelial cellsnoncanonical binding sitegalactoseprotein-linked glycan structurespolymerFucose-Galactose Polymers Inhibit Cholera Toxin Bindingmurine SI ECscomplementing CTB binding studiesGM 1CT B subunitblocks CT-mediated secretioncanonical sitecanonical cholera toxin ligandSI ECs
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