Differential effects of three inhibitors of glycosphingolipid biosynthesis on neuronal differentiation of embryonal carcinoma stem cells

Gangliosides have been implicated in having important roles in neural development. It has been shown that disruption of ganglioside biosynthesis inhibits neurite outgrowth. However, many contradictory results have been reported. The inconsistency of these reports may result from the differential use of neuronal cell lines and inhibitors for ganglioside biosynthesis. In order to clarify the inconsistency in these studies, we utilized an in vitro neuronal differentiation model using an embryonic caricinoma (EC) stem cell line to elucidate the relationship between ganglioside expression and neural development. These cells were exposed to three different inhibitors of glucosylceramide synthase, the first enzyme committed for the biosynthesis of most of the brain gangliosides. All three inhibitors, d-threo-1-phenyl-2-decanoylamino-3-morphlino-1-propanol (D-PDMP), d-threo-1-phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (D-PPPP), and N-butydeoxynojirimycin (NB-DNJ) can inhibit greater than 90% of ganglioside biosynthesis at certain concentrations, respectively. D-PDMP significantly slowed down cellular proliferation in undifferentiated P19 EC cells, inhibited neurite outgrowth, and eventually caused cell death in differentiated cells. However, no retardation in cell growth, neuronal differentiation, and neurite outgrowth was observed in cultures treated with D-PPPP or NB-DNJ despite the depletion of gangliosides. These results indicate that the effect of D-PDMP on cellular proliferation, neurite outgrowth, and survival of differentiated cells is independent of the inhibition of ganglioside biosynthesis.