Structural insights in galectin-1-glycan recognition: relevance of the glycosidic linkage and the N-acetylation pattern of sugar moieties

PORCIUNCULA, DIANA; CAGNONI, ALEJANDRO J.; FONTANA, CAROLINA; MARIÑO, KARINA VALERIA; SAENZ-MENDEZ, PATRICIA; GIACOMINI, CECILIA; IRAZOQUI, GABRIELA

BIOORGANIC & MEDICINAL CHEMISTRY.

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2021 vol. 44

0968-0896

Galectins, soluble lectins widely expressed intra- and extracellularly in different cell types, playmajor roles in deciphering the cellular glycocode. Galectin-1 (Gal-1), a prototype member ofthis family, presents a carbohydrate recognition domain (CRD) with specific affinity for β-galactosides such as N-acetyllactosamine (-D-Galp-(1 4)-D-GlcpNAc), and mediatenumerous physiological and pathological processes.In this work, Gal-1 binding affinity for β-(1 6) galactosides, including β-D-Galp-(1→6)-β-DGlcpNAc-(1→4)-D-GlcpNAc was evaluated, and their performance was compared to that of β-(1→4) and β-(1→3) galactosides. To this end, the trisaccharide β-D-Galp-(1→6)-β-DGlcpNAc-(1→4)-D-GlcpNAc was enzymatically synthesized, purified and structurallycharacterized.To evaluate the affinity of Gal-1 for the galactosides, competitive solid phase assays (SPA) andisothermal titration calorimetry (ITC) studies were carried out. The experimental dissociationconstants and binding energies obtained were compared to those calculated by moleculardocking. These analyses evidenced the critical role of the glycosidic linkage between theterminal galactopyranoside residue and the adjacent monosaccharide, as galactosides bearingβ-(1→6) glycosidic linkages showed dissociation constants six- and seven-fold higher thanthose involving β-(1→4) and β-(1→3) linkages, respectively. Moreover, docking experimentsrevealed the presence of hydrogen bond interactions between the N-acetyl group of theglucosaminopyranose moiety of the evaluated galactosides and specific amino acid residues ofGal-1, relevant for galectin-glycan affinity. Noticeably, the binding free energiesGbindcalc) derived from the molecular docking were in good agreement with experimental values determined by ITC measurements (Gbind exp), evidencing a good correlation between 3 theoretical and experimental approaches, which validates the in silico simulations and constitutes an important tool for the rational design of future optimized ligands.