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Galectins are involved in various biological processes, e.g. cell-cell and cell-matrix adhesion and the transmission of cellular signals. Despite the diversity of functions, little is known about the nature of their physiological cognate ligands on the cell surface and the localization of galectins in the glycocalyx, although this information is important for understanding the functional activity of galectins. In this work, localization of endogenous and exogenously loaded galectins in the glycocalyx was studied. The following main conclusions are drawn: 1) galectins are not evenly distributed within the glycocalyx, they are accumulated in patches. Patching is not the result of a cross-linking of cellular glycans by galectins. Instead, patch-wise localization is the consequence of irregular distribution of glycans forming the glycocalyx; 2) galectins are accumulated in the inner zone of the glycocalyx rather than at its outer face or directly in vicinity of the cell membrane; 3) patches are not associated with cell rafts.

A major aspect of carbohydrate-dependent galectin functionality is their cross-linking capacity. Using a cell surface as biorelevant platform for galectin binding and a panel of 40 glycans as sensor part of a fluorescent polyacrylamide neoglycopolymer for profiling galectin reactivity, properties of related proteins can be comparatively analyzed. The group of the chicken galectins (CGs) is an especially suited system toward this end due to its relatively small size, compared with mammalian galectins. The experiments reveal particularly strong reactivity toward N-acetyllactosamine repeats for all tested CGs and shared reactivity of CG-1A and CG-2 to histo-blood group ABH determinants. In cross-species comparison, CG-1B's properties closely resembled those of human galectin-1, as was the case for the galectin-2 (but not galectin-3) ortholog pair. Although binding-site architectures are rather similar, reactivity patterns can well differ., (© The Author 2015. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)