OVEREXPRESSING CELL-SURFACE BETA-1,4-GALACTOSYLTRANSFERASE IN PC12 CELLS INCREASES NEURITE OUTGROWTH ON LAMININ

Neurite outgrowth on cellular and extracellular matrices is mediated b y a variety of cell surface receptors. Some of these receptors recogni ze peptide determinants, whereas others bind oligosaccharide ligands. Previous studies have suggested that cell surface beta 1,4-galactosylt ransferase functions as one of these receptors during neurite outgrowt h on basal lamina by binding to N-linked oligosaccharides in the E8 do main of laminin. However, these previous investigations have been limi ted to the use of galactosyltransferase inhibitory reagents to block n eurite formation. Therefore, in this study, we investigated whether th e level of surface galactosyltransferase directly affects the efficien cy 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 su rface galactosyltransferase by approximately four-fold. Radiolabeled a ntibody binding to intact cells and indirect immunofluorescence confir med the higher expression of surface galactosyltransferase on transfec ted cells, compared to controls. Both galactosyltransferase transfecte d cell lines exhibited markedly enhanced neurite initiation, neurite f ormation, and rates of neurite elongation by two- to three-fold. These studies demonstrate that the expression of laminin receptors can be r ate-limiting during neurite outgrowth, and that the level of surface g alactosyltransferase can modulate the frequency and rate of neurite fo rmation from PC12 cells on laminin.