NERVE GROWTH FACTOR-INDUCED NEURITE FORMATION IN PC12 CELLS IS INDEPENDENT OF ENDOGENOUS CELLULAR GANGLIOSIDES

The PC12 rat pheochromocytoma cell line is an established model for ne rve growth factor (NGF)-induced neurite formation. It has been shown t hat when gangliosides are added to the culture medium of PC12 cells, N GF-induced neurite formation of PC12 cells is enhanced. To determine t he role of endogenous cellular gangliosides themselves in NGF-elicited neurite formation, we depleted cellular gangliosides using the new sp ecific glucosylceramide synthase inhibitor, enyl-2-hexadecanoylamino-3 -pyrrolidino-1-propanol. HCl (PPPP). 0.5-2 mu M PPPP rapidly inhibited ganglioside synthesis and depleted cellular gangliosides. Nonetheless , over a concentration range of 5-100 ng/ml NGF, in both low serum and serum-free medium, neurite formation was normal. Even pretreatment of PC12 cells up to 6 days with 1 mu M PPPP followed by cotreatment with PPPP and NGF for 10 days, still did not inhibit neurite formation. Th e conclusion that ganglioside depletion did not block neurite formatio n stimulated by NGF was supported by the lack of effect of PPPP, under these same conditions, on cellular acetylcholine esterase activity, a neuronal differentiation marker (73.8+/-12.1 versus 67.2+/-4.6 nmol/m in/mg protein at 50 ng/ml NGF; control versus 1 mu M PPPP). These find ings, together with previous studies showing enhancement of NGF-induce d neurite formation by exogenous gangliosides, underscore that vastly different effects that exogenous gangliosides and endogenous gangliosi des may have upon cellular functions.