Assembly, organization and regulation of cell surface receptors by lectin-glycan complexes

ELOLA, MARÍA TERESA; BLINDER, ADA; FERRAGUT, FÁTIMA; BRACALENTE, CANDELARIA; RABINOVICH, GABRIEL A.

BIOCHEMICAL JOURNAL

PORTLAND PRESS LTD

Lugar: Londres; Año: 2015 vol. 469 p. 1 - 16

0264-6021

Galectins are a family of galactoside-binding lectins carrying at least one consensus sequence in the carbohydrate-recognition domain, which interacts with certain glycans. Ligand properties such as N- and O-glycan branching, N-acetyllactosamine content and the balance of a2,3- and a2,6-linked sialic acid dramatically influence on galectin binding. The presentation of specific glycans in galectin binding partners is also critical: proper orientation and clustering of oligosaccharide ligands on multiple carbohydrate side chains would increase the binding avidity of galectins for a particular glycoconjugate. When galectins are secreted from cells, they typically concentrate on the cell surface and the local matrix, raising their local concentration. Thus, galectins can form their own multimers in the extracellular milieu, which in turn cross-link glycoconjugates from the cell surfaces producing galectin-glycan complexes -also termed lattices- that modulate intracellular signaling pathways thus regulating cellular processes such as apoptosis, proliferation, migration and angiogenesis. Subtle changes in receptor expression, protein synthesis rates, Golgi enzyme activities, metabolite concentrations supporting biosynthesis, density of glycans/receptor, protein-protein interactions of glycoproteins above and below the plasma membrane, stoichiometry, etc. modify galectin-glycan complexes. Although galectins are key contributors to the formation of these extended glycan complexes leading to inhibition of receptor internalization by surface retention, when lattices are disrupted some galectins (galectin-3/-4) have the ability to drive clathrin-independent mechanisms of endocytosis. Herein, we summarize data available on conspicuous galectin-glycan complexes well-characterized in this field.