Specific binding of glycosylated beta-galactosidase to rat clonal pheochromocytoma PC12h cells: effects of nerve growth factor and gangliosides.

Rat clonal pheochromocytoma PC12h cells were found to bind beta-galactosidase modified with specific glycosides. The enzyme modified with p-aminophenyl beta-D-glucoside was most effectively bound to the cells, followed by alpha-D-mannoside and alpha-D-glucoside. The binding was dependent on the number of PC12h cells, the incubation interval, and the pH; the maximal binding at 4 degrees C was obtained by incubation with 75 micrograms of cell protein for 15 min at pH 4.0. The binding proved to be a saturable and receptor-mediated process, and the apparent Km value and the maximal binding capacity of the cells with beta-D-glucosylated beta-galactosidase were 1.03 +/- 0.06 microM and 333 +/- 24 pmol/min/mg of protein, respectively. When the cells were cultured in the presence of nerve growth factor (NGF), GM1, GM2, and a ganglioside mixture, marked morphological differentiation was observed in the presence of NGF, and the specificity of the binding was also affected. By supplementation of NGF in the culture medium, the cells lost the selectivity of the glycoside binding, whereas cells cultured with GM1 supplement showed increased binding of the specific glycosides.