Elevation of Ceramide within Distal Neurites Inhibits Neurite Growth in Cultured Rat Sympathetic Neurons

Abstract

Sphingolipids are abundant constituents of neuronal membranes and have been implicated in intracellular signaling. We show that two analogs of glycosphingolipid biosynthetic intermediates, fumonisin B 1 (which inhibits dihydroceramide synthesis) and DL-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol (PPMP) (which inhibits glucosylceramide synthesis) decrease glycosphingolipid synthesis in rat sympathetic neurons. Although both fumonisin and PPMP inhibit glycosphingolipid synthesis, these inhibitors have differential effects on ceramide metabolism in axons. threo-PPMP, but not erythro-PPMP or fumonisin, induces an accumulation of [ 3 H]palmitate-labeled ceramide and impairs axonal growth. Moreover, exogenously added, cell-permeable C 6 -ceramide, but not C 6 -dihydroceramide, mimicks the effect of PPMP. Our studies suggest that the lipid second messenger ceramide acts in distal axons, but not cell bodies, as a negative regulator of neurite growth. Glycosphingolipids (GSLs)1 are major components of eukaryotic cell membranes and are particularly enriched in neuronal membranes. Lipids of this class contain one or more sugar residues attached to a sphingoid base backbone. GSLs are present in the outer leaflet of the plasma membrane (1, 2) where they have been postulated to play a role in a number of important cellular processes including cell-cell and cell-substratum recognition, adhesion, differentiation, proliferation, and oncogenic transformation. The pattern of GSLs differs among cell types and changes during development, cellular differentiation, and oncogenic transformation suggesting an important role for GSLs in cell growth and proliferation (3-5).In addition, intermediates in the biosynthesis and catabolism of sphingolipids and GSLs may function as lipid second messengers mediating the effects of extracellular agents and agonists (6 -8). One approach used extensively to examine the function of GSLs is the exogenous addition of GSLs to cells, since the amphipathic nature of GSLs permits their incorporation into cellular membranes. The enrichment of gangliosides (sialic acid containing GSLs) in neuronal membranes induces neuritogenesis (3, 9 -12), modulates growth factor receptor activity (reviewed in Refs. 3,13,14), potentiates responses to neurotrophic factors (13, 15), and protects against apoptotic death caused by withdrawal of trophic support (16). Moreover, antibodies raised against gangliosides inhibit neurite outgrowth from neural cells and tissues slices in vitro (17, 18). Tettamanti and Riboni (19) have summarized the role of gangliosides in neurodifferentiation, neuritogenesis, and synaptogenesis.Only recently has the effect of the reduction of cellular GSL levels on neurons, through the inhibition of endogenous GSL synthesis, been examined. Inhibition of dihydroceramide synthesis, an early step in the synthesis of all GSLs (see Fig. 1), in cultured hippocampal neurons disrupts axonal growth (20) and the formation and maintenance of axonal branches (21). Similar studies have found that sphingolipi...

Apoptosis‐induced inhibition of CD1d‐mediated antigen presentation: different roles for caspases and signal transduction pathways

“…PPMP, an analogue of ceramide, competitively inhibits glucosylceramide synthase and thus prevents the conversion of ceramide to glucosylceramide. 31,32 As a result, the intracellular ceramide level in PPMP-treated cells is elevated over time, resulting in apoptosis. We also found that PPMP treatment inhibited CD1d-mediated antigen presentation, and increased the intracellular levels of ceramide, whereas other glycosphingolipid inhibitors such as FB1 or NB-DGJ did not.…”

“…It is known that PPMP (but not FB1 or NB-DGJ) treatment results in an increased level of intracellular ceramide, leading to apoptosis, whereas FB1 inhibits the biosynthesis of the ceramide in the treated cells. 31 LMTKCD1d1 cells treated with PPMP showed a reduction in their ability to stimulate NKT cells in a concentrationdependent manner (Fig. 1a), with an almost 50% decrease in antigen presentation at the highest concentration of PPMP as compared to vehicle-treated cells.…”

Ceramide influences neurite outgrowth and neuroblastoma cell apoptosis regulated by novel protein kinase C isoforms

“…However, ceramide has also been shown to negatively regulate neurite growth. This is exemplified by the inhibition of elongation of sympathetic axons by a local increase in ceramide levels (de Chaves et al 1997(de Chaves et al , 2001.…”

Selectivity of Cell Signaling in the Neuronal Response Based on NGF Mutations and Peptidomimetics in the Treatment of Alzheimers Disease

“…Sympathetic neurons and basal forebrain neurons that were p75-deficient in p75-/-mice underwent robust axonal sprouting, hypertrophy, or target innervation with naturally-occurring developmental apoptosis being significantly delayed (Kaplan & Miller, 2000;Walsh et al, 1999;Yeo et al, 1997;Bamji et al, 1998). Without intrinsic catalytic activity, the p75 ICD appears to rely on docking of adaptor www.intechopen.com Aloyz et al, 1998;Salehi, et al, 2002;Muller, et al, 1998;de Chaves et al, 1997;Casademunt, et al, 1999;2 Chittka & Chao, 1999;3 Domeniconi et al, 2005;4 Khursigara et al, 1999;5 Susen, et al, 1999;Lad & Neet, 2003.…”

“…Functional data gathered from systematic mutagenesis studies and through the construction of inter-neurotrophin chimeras coupled with structural data from crystallographic studies have implicated several spatially distinct patches of residues in bestowing receptor specificity to each neurotrophin (Casademunt et al, 1999;de Chaves et al, 1997;Grimes et al, 1997;Ilag et al, 1994;Lad et al, 2003a;Ninkina et al, 1997;Rabizadeh et al, 1993;J. Scott et al, 1983;Walsh et al, 1999;Wiesmann et al, 1999;Yeo et al, 1997) .…”