Dissecting molecular determinants of the Galectin-4 glycan axis and its potential role in intestinal inflammation

MASSARO, MORA; RABINOVICH, GABRIEL A.; MANSELLE COCCO, MONTANA; MARIÑO, KARINA V.; PÉREZ SÁEZ, JUAN MANUEL; CAGNONI, ALEJANDRO J.

Buenos Aires

Simposio; 5to Simposio Argentino de Jovenes Investigadores en Bioinformatica; 2020

International Society of Computational Biology

Inflammatory Bowel Diseases (IBD) constitute a group of chronic inflammatory disorders that affect the gastrointestinal tract, in which the perpetual state of inflammation predisposes to the development of colitis associated colorectal cancer (CACRC). The increasing global incidence of both pathologies generate a prevailing need for the search of new biomarkers and therapeutic targets. In this context, and even though galectin-glycan interactions play a central role as a mediator of pathophysiological processes, their role in IBD and CACRC has been barely explored. Galectins, a family of soluble lectins, are involved in immunomodulation, inflammation, pathogen recognition, tumor escape and metastasis. In particular, Galectin-4 (Gal-4), a tandem-repeat galectin expressed in the gastrointestinal tract, exerts a predominantly pro-inflammatory role stimulating T lymphocytes and exacerbating intestinal inflammation via recognition of an aberrant "Colitis-Associated Glycome?. This galectin presents two carbohydrate recognition (CRD) domains at the N- and C-terminal ends. Through an interdisciplinary approach, we have recombinantly expressed human Gal-4 and each of its isolated CRDs, and their glycosidic preferences were evaluated. In doing so, we identified selective affinity of Gal-4 for specific glycan moieties. We evaluated the inhibitory role in vitro of a specific glycan, for which we demonstrate its capability of modulating the proinflammatory role of this lectin. We characterized the biochemical and biophysical determinants of these interactions in silico, using docking simulations and molecular dynamics. For docking, Gal-4 N and C terminal domains and glycan structures were downloaded from Protein Data Bank (PDB) and prepared for the analyses using AutoDock Tools. The simulations were performed with AutoDock4, AutoDock Vina, Vina-Carb and AutoDock Bias software packages. The best glycan conformations were visualized and selected for molecular dynamics studies with VMD software. For these studies, Gal-4 terminal domains were previously equilibrated, 200 ns simulations were done at constant pressure with Amber12 package and visualized with VMD software. Together, these analyses allowed for the identification of key amino acid residues responsible for glycan recognition preferences. Taking into account the results obtained, together with the high affinity for Gal-4 and its lack of toxicity, these glycans present very promising properties for their use as potential therapeutic agents in IBD.