Clustering of Escherichia coli Type‐1 Fimbrial Adhesins by Using Multimeric Heptyl α‐D‐Mannoside Probes with a Carbohydrate Core

Abstract

Heptyl α-D-mannoside (HM) is a strong inhibitor of the FimH lectin that mediates the initial adhesion of the uropathogenic Escherichia coli (E. coli) to the bladder cells. We designed a set of multivalent HM ligands based on carbohydrate cores with structural valencies that range from 1 to 7. The chemical strategy used to construct the regular hydrophilic structures consisted of the repetition of a critical glucoside fragment. A primary amino group was grafted at the sugar reducing end to couple the multimers to a fluorescent label. A one-pot synthetic approach was developed to tether the ligands and the fluorescein isothiocyanate (FITC) probe to the scaffold simultaneously. Isothermal calorimetry with the monomeric FimH lectin revealed nanomolar affinities and saturation of all structurally available binding sites on the multivalent HM ligands. Direct titrations domain showed almost strict correlation of enthalpy-entropy compensation with increasing valency of the ligand, whereas reverse titration calorimetry demonstrated negative cooperativity between the first and the second binding site of the divalent heptyl mannoside. A multivalency effect was nevertheless observed by inhibiting the haemagglutination of type-1 piliated UTI89 E. coli, with a titer as low as 60 nM for the heptavalent HM ligand. An FITC-labeled HM trimer showed capture and cross-linking of living bacteria in solution, a phenomenon not previously described with low-valency ligands.

Glycodendrimers: versatile tools for nanotechnology

“…This value compares favorably well with the ones recently published using fullerene (Durka et al, 2011) or pentaerythritol (Gouin et al, 2009 scaffolds. However, a linear heptameric mannocluster built on sugar scaffolds and having a more hydrophobic heptyl aglycon showed better HAI titers than the one reported herein (Almant et al, 2011).…”

Rational design strategies for FimH antagonists: new drugs on the horizon for urinary tract infection and Crohn’s disease

“…While this focus has largely been replaced by the rational design of orally bioavailable lower molecular monomeric mannosides, several multivalent mannoside inhibitors have been reported, including glycodendrimers and neoglycoproteins [107-108], CD-based HMs [69, 109-114], glycoclusters [115-116], and others [117-120]. While these have been extensively reviewed previously [121-122], we present select examples of smaller, di-and tri-valent mannosides in the following discussion.…”

Glycoconjugates and Glycomimetics as Microbial Anti-Adhesives

“…against gut-colonizing AIEC), or when FimH adhesion is exploited to achieve bacterial aggregation and biofilm disruption. They vary from medium-sized scaffolds [19][20][21][22][23], to dendrimers [3,24], polymers [25] and nanoparticles [26][27][28][29]. Despite the spacing between fimbriae can vary between strains and depends on growth conditions [30], only the largest of these materials are likely to engage more than one protein at the time, because the FimH binding site can interact with only one mannose residue at the time and each of the fimbriae carries only a single copy of FimH.…”