Combining Glycomimetic and Multivalent Strategies toward Designing Potent Bacterial Lectin Inhibitors

Abstract

As part of ongoing activities toward the design of potent and selective ligands against galactoside-binding proteins from animal, bacterial, and plant lectins, a systematic investigation involving the synthesis and binding evaluations of a series of original β-C-galactopyranoside mimetics is described. The multivalent presentation of partly optimized candidates on various dendritic scaffolds through Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAc) has also been achieved. Biophysical investigations based on isothermal titration calorimetry (ITC) have indicated a dissociation constant in the low micromolar range for the best optimized monovalent conjugate (K(d)=37 μM). The results thus confirmed that stable C-galactosides could represent efficient synthetic glycomimetics of natural α-linked oligosaccharidic inhibitors of PA-IL lectin (Lec A) from the pathogenic Pseudomonas aeruginosa. Striking enhancements in the avidity of the glycoconjugates were also observed for tri-, hexa-, and nonavalent derivatives, among which the most potent exhibited dissociation constants below 500 nM, corresponding to a 400-fold increase in affinity compared with the β-D-Gal-O-Me used as reference. To deepen our understanding of the binding mode of the best glycomimetics involved in the recognition process, molecular modeling studies, docking calculations, and NMR diffusion measurements have been performed. Although favorable complementary interactions induced by the addition of the hydrophobic aglycon might explain the affinity enhancement, experimental determination of the size and the topology of the multivalent conjugates further supported the formation of aggregative complexes as a major multivalent binding mode. This work represents a systematic and comprehensive study towards a thorough understanding of the protein-carbohydrate interactions involved in Pseudomonas aeruginosa infection, and as such should prove useful for the development of stable and optimized anti-adhesive agents.

Synthesis and solvodynamic diameter measurements of closely related mannodendrimers for the study of multivalent carbohydrate–protein interactions

“…Zemplén deprotection (NaOMe, MeOH) afforded 5 in 94% yield. Synthesis of the related homolog 9 , prepared in 74% overall yield from known 6 [17] by an analogous click chemistry, is also described in Scheme 1. To this end, trichloride 1 was treated as above with 3-azido-1-propanamine to provide 6 in 87% yield.…”

“…Among the diverse strategies leading to efficient ligands, glycopolymers [1,5–7], glycodendrimers [7–14], and sugar rods [15–16] have retained most attention. An additional approach that has gained keen interest resides in the modifications of both the aglycon [17–19] and substituent residues [20–22] of the targeted sugar moieties through extensive studies of quantitative structure–activity relationships (QSARs). In most of the studies related to aglycon modifications, it was concluded that aromatic glycosides possessed improved binding properties due to the ubiquitous presence of aromatic amino acids in the cognate binding sites [23–25].…”

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2011–2012

“…(Chabre et al, 2011) Triphenylamine Glucose TOF Star-shaped glycosylated conjugated oligomer for twophoton fluorescence imaging Trivinyl benzene Sulfonated-GlcNAc TOF Click chemistry. Synthesis and observation of a reduction in nanofiber formation Poly-( -amino esters) TOF Synthesis of nanoparticles for sustained drug delivery across the blood-brain barrier (Gil et al, 2012) Sucrose Peptides TOF (sinapinic)…”

Glycodendrimers and Their Derivatives as Potential Therapeutic Agents

“…It has been shown that solutions of galactose and fucose which are capable of bounding to LecA and LecB, respectively, have a therapeutic potential against P. aeruginosa pneumonia in a mouse model and in patients with cystic fibrosis. [9] Recently it has been investigated that peptide glycomimetics have high binding affinity to both LecA and LecB, and prevent their toxic activity. [10] LecA (also called PA-IL) is a tetrameric cytotoxic lectin consisting of four subunits of 121 amino acids (12.75 kDa) each with specificity to α-D-galactose and, preferentially, to binding to Gal-α-(1,4)-Gal, containing globotriacylceramide Gb3 sphingolipid.…”