Overexpressing cell surface beta 1.4-galactosyltransferase in PC12 cells increases neurite outgrowth on laminin

Neurite outgrowth on cellular and extracellular matrices is mediated by a variety of cell surface receptors. Some of these receptors recognize peptide determinants, whereas others bind oligosaccharide ligands. Previous studies have suggested that cell surface beta 1.4-galactosyltransferase functions as one of these receptors during neurite outgrowth on basal lamina by binding to N-linked oligosaccharides in the E8 domain of laminin. However, these previous investigations have been limited to the use of galactosyltransferase inhibitory reagents to block neurite formation. Therefore, in this study, we investigated whether the level of surface galactosyltransferase directly affects the efficiency of neurite outgrowth, or rather, is incidental to neurite formation. Northern blot analysis and cell surface galactosyltransferase assays were used to select two stable PC12 transfectants that overexpress surface galactosyltransferase by approximately four-fold. Radiolabeled antibody binding to intact cells and indirect immunofluorescence confirmed the higher expression of surface galactosyltransferase on transfected cells, compared to controls. Both galactosyltransferase transfected cell lines exhibited markedly enhanced neurite initiation, neurite formation, and rates of neurite elongation by two- to three-fold. These studies demonstrate that the expression of laminin receptors can be rate-limiting during neurite outgrowth, and that the level of surface galactosyltransferase can modulate the frequency and rate of neurite formation from PC12 cells on laminin.