Galectin-3 promotes neural cell adhesion and neurite growth

Galectin-3 is a member of the galectin family and belongs to a group of soluble beta-galactoside-binding animal lectins. The molecule is expressed by neural and nonneural cells intra- (cytoplasm and nucleus) as well as extra-cellularly (plasma membrane and extracellular space). By using an in vitro cell-substratum adhesion assay, we have addressed the question whether galectin-3 present in the extracellular milieu may support the adhesion and/or neurite outgrowth of neural cells in a manner analogous to cell adhesion molecules. Galectin-3 was immobilized as a substratum and various cell types, N2A (neuroblastoma), PC12 (pheochromocytoma), and TSC (transformed Schwann cells) cell lines, neural cells from early postnatal mouse cerebellum, and dorsal root ganglion neurons from newborn mice were allowed to adhere to the lectin. Here we show that all cell types studied specifically adhered to galectin-3 by the following criteria: 1) the number of adherent cells was dependent on the galectin-3 concentration used for coating; 2) adhesion of cells to galectin-3, but not to collagen type I or laminin was inhibited by polyclonal antibodies to galectin-3; 3) upon addition of asialofetuin (a polyvalent carrier of terminal beta-galactosides) to the cell suspension prior to the adhesion assay, cell adhesion to galectin-3 was inhibited in a dose-dependent manner; and 4) cell adhesion to galectin-3 was abolished by treatment of cells with endo-beta-galactosidase. In addition, the adhesion of dorsal root ganglion neurons to galectin-3 could be inhibited by lactose. Notably, substratum-bound galectin-3 promoted the outgrowth of neurites from dorsal root ganglia explants and this neurite outgrowth promoting activity could be inhibited by polyclonal antibodies to galectin-3.