GALECTIN-3 PROMOTES NEURAL CELL-ADHESION AND NEURITE GROWTH

Galectin-3 is a member of the galectin family and belongs to a group o f soluble beta-galactoside-binding animal lectins. The molecule is exp ressed by neural and nonneural cells intra- (cytoplasm and nucleus) as well as extra-cellularly (plasma membrane and extracellular space). B y using an in vitro cell-substratum adhesion assay, we have addressed the question whether galectin-3 present in the extracellular milieu ma y support the adhesion and/or neurite outgrowth of neural cells in a m anner analogous to cell adhesion molecules. Galectin-3 was immobilized as a substratum and various cell types, N2A (neuroblastoma), PC12 (ph eochromocytoma), and TSC (transformed Schwann cells) cell lines, neura l cells from early postnatal mouse cerebellum, and dorsal root ganglio n 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 depen dent on the galectin-3 concentration used for coating; 2) adhesion of cells to galectin-3, but not to collagen type I or laminin was inhibit ed by polyclonal antibodies to galectin-3; 3) upon addition of asialof etuin (a polyvalent carrier of terminal beta-galactosides) to the cell suspension prior to the adhesion assay, cell adhesion to galectin-3 w as inhibited in a dose-dependent manner; and 4) cell adhesion to galec tin-3 was abolished by treatment of cells with endo-beta-galactosidase . In addition, the adhesion of dorsal root ganglion neurons to galecti n-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 p olyclonal antibodies to galectin-3. (C) 1998 Wiley-Liss, Inc.