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

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

BIOORGANIC & MEDICINAL CHEMISTRY.

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2021

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 associationconstants 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 association constants six- and seven-fold lower than thoseinvolving β-(1→4) and β-(1→3) linkages, respectively. Moreover, docking experimentsrevealed the presence of hydrogen bond interactions between the N-acetyl group of theglucopyranose moiety of the evaluated galactosides and specific amino acid residues of Gal-1,relevant for galectin-glycan affinity. Noticeably, the binding free energies deltaG bindcalc) derivedfrom the molecular docking were in good agreement with experimental values determined byITC measurements (deltaGbind exp), evidencing a good correlation between theoretical andexperimental approaches, which validates the in silico simulations and constitutes an importanttool for the rational design of future optimized ligands.