Lactose-Functionalized Carbosilane Glycodendrimers Are Highly Potent Multivalent Ligands for Galectin-9 Binding: Increased Glycan Affinity to Galectins Correlates with Aggregation Behavior

Abstract

Galectins, the glycan binding proteins, and their respective carbohydrate ligands represent a unique fundamental regulatory network modulating a plethora of biological processes. The advances in galectin-targeted therapy must be based on a deep understanding of the mechanism of ligand−protein recognition. Carbosilane dendrimers, the well-defined and finely tunable nanoscaffolds with low toxicity, are promising for multivalent carbohydrate ligand presentation to target galectin receptors. The study discloses a synthetic method for two types of lactosefunctionalized carbosilane glycodendrimers (Lac-CS-DDMs). Furthermore, we report their outstanding, dendritic effect-driven affinity to tandem-type galectins, especially Gal-9. In the enzymelinked immunosorbent assay, the affinity of the third-generation multivalent dendritic ligand bearing 32 lactose units to Gal-9 reached nanomolar values (IC 50 = 970 nM), being a 1400-fold more effective inhibitor than monovalent lactose for this protein. This demonstrates a game-changing impact of multivalent presentation on the inhibitory effect of a ligand as simple as lactose. Moreover, using DLS hydrodynamic diameter measurements, we correlated the increased affinity of the glycodendrimer ligands to Gal-3 and Gal-8 but especially to Gal-9 with the formation of relatively uniform and stable galectin/Lac-CS-DDM aggregates.

Glycopolymer Inhibitors of Galectin-3 Suppress the Markers of Tissue Remodeling in Pulmonary Hypertension

“… 20 , 21 The latter copolymer scaffold was also used for the multivalent presentation of thiodigalactoside-based glycomimetics. 17 Our previous work with both nature-like oligosaccharides 16 , 18 , 20 − 22 and glycomimetics 17 , 23 repeatedly proved that by means of multivalent presentation, the resulting glycoconjugate affinity to galectins can be increased by several orders of magnitude, reaching low nanomolar or even picomolar levels. Thereby, each multivalent scaffold had its specific architectural features, and for maximizing the resulting affinity, it is vital to balance the ligand-scaffold synergy in view of hydrophobicity, sterical properties, flexibility, etc.…”

“…Gal-3 can be efficiently inhibited or scavenged by synthetic carbohydrates and glycomimetics. Its simplest ligands are disaccharides such as lactose (Galβ1,4Glc), LacNAc ( N -acetyllactosamine; Galβ1,4GlcNAc), LacdiNAc (GalNAcβ1,4GlcNAc), or thiodigalactoside (Galβ1,1-S-Gal), which can be attached to various biocompatible carriers 16 − 18 or chemically modified affording glycomimetics. 19 In our earlier studies, poly-LacNAc-based oligosaccharide ligands of Gal-3 were bound to a scaffold of bovine serum albumin 5 or attached to hydrophilic N -(2-hydroxypropyl)methacrylamide (HPMA) copolymer.…”