Galectin-glycan lattices regulate cell-surface glycoprotein organization and signalling.

The formation of multivalent complexes of soluble galectins with glycoprotein receptors on the plasma membrane helps to organize glycoprotein assemblies on the surface of the cell. In some cell types, this formation of galectin-glycan lattices or scaffolds is critical for organizing plasma membrane domains, such as lipid rafts, or for targeted delivery of glycoproteins to the apical or basolateral surface. Galectin-glycan lattice formation is also involved in regulating the signalling threshold of some cell-surface glycoproteins, including T-cell receptors and growth factor receptors. Finally, galectin-glycan lattices can determine receptor residency time by inhibiting endocytosis of glycoprotein receptors from the cell surface, thus modulating the magnitude or duration of signalling from the cell surface. This paper reviews recent evidence in vitro and in vivo for critical physiological and cellular functions that are regulated by galectin-glycoprotein interactions.