Increase of Nuclear Ceramide through Caspase-3-Dependent Regulation of the “Sphingomyelin Cycle” in Fas-Induced Apoptosis

Abstract

Regardless of the existence of ceramide-related molecules, such as sphingomyelin (SM), neutral sphingomyelinase (nSMase), and SM synthase, in the nucleus, the regulation of ceramide in the nucleus is poorly understood in stress-induced apoptosis. In Fas-induced Jurkat T-cell apoptosis, we found a time-and dose-dependent increase of ceramide content in the nuclear and microsomal fractions. Fas-induced increase of ceramide content in the nucleus also was detected by confocal microscopy using anticeramide antibody. Activation of nSMase and inhibition of SM synthase were evident in the nuclear fraction after Fas cross-linking, whereas nSMase was activated, but SM synthase was not affected, in the microsomal fraction. Pretreatment with D-609, a putative SM synthase inhibitor, enhanced Fas-induced increase of ceramide in the nucleus and induction of apoptosis along with increase of Fas-induced inhibition of nuclear SM synthase. Fas-induced activation of caspase-3 was detected in the nuclear fraction and in whole cell lysate. A caspase-3 inhibitor, acetyl-Asp-GluVal-Asp-chloromethyl ketone, blocked not only Fas-induced increases of apoptosis and ceramide content but also Fas-induced activation of nSMase and inhibition of SM synthase in the nuclear fraction. Taken together, it is suggested that the nucleus is a site for ceramide increase and caspase-3 activation in Fas-induced Jurkat T-cell apoptosis and that caspase-3-dependent regulation of the "SM cycle" consisting of nSMase and SM synthase plays a role in Fas-induced ceramide increase in the nucleus.

Molecular requirements for doxorubicin-mediated death in murine oocytes

“…As cytoplasmic 33 and nuclear localization of ceramide have been previously documented, 34 we hypothesize that once inside the oocytes, DXR takes residence in the cytosol, binds to ceramide (if present), and ultimately it (DXR) or its derivative(s) is transported to the nucleus where again complexing with ceramide enhances its association with the DNA. As there is published evidence 35 of the possible modulatory role of other lipids (e.g., sphingomyelin) in DXR mediations, we cannot exclude their contribution to the DXR pathway in this model.…”

Expression Cloning of a Human cDNA Restoring Sphingomyelin Synthesis and Cell Growth in Sphingomyelin Synthase-defective Lymphoid Cells

“…SM synthase is closely regulated by the levels of ceramide and DAG, as well as extracellular stresses (15,18,31,42). SM synthase is suggested to localize not only in the plasma membrane (37) and Golgi apparatus (43) but also in the endoplasmic reticulum (38) and nucleus (17,44). We recently reported that, in Fas-induced Jurkat T cell apoptosis, ceramide increased through inhibition of SM synthase in the nucleus (17).…”

“…SM synthase is suggested to localize not only in the plasma membrane (37) and Golgi apparatus (43) but also in the endoplasmic reticulum (38) and nucleus (17,44). We recently reported that, in Fas-induced Jurkat T cell apoptosis, ceramide increased through inhibition of SM synthase in the nucleus (17). The relationship between the intracellular localization and the regulation of SM synthase activity and the regulatory mechanism for the levels of lipid mediators in cell growth and death through SM synthase should be clarified by detailed analysis of the SMS genes.…”

“…In SV40-transformed lung fibroblasts, SM synthase regulates the levels of ceramide and DAG in an opposite direction (16). We recently reported that SM synthase was activated to inhibit ceramide generation in IL-2-induced proliferation of natural killer cells, 2 whereas the activity in nucleus was inhibited with ceramide generation in Fas-induced T cell apoptosis (17). We also showed its in vivo implication that the level of ceramide was decreased via activation of SM synthase in chemotherapy-resistant blast cells obtained from refractory leukemia patients than in chemotherapy-sensitive leukemic blasts (18).…”

Caspase-mediated inhibition of sphingomyelin synthesis is involved in FasL-triggered cell death

“…A more recent study indicates that Fas engagement is accompanied by the inhibition of an SMS activity and ceramide increase within the nucleus. 13 Different stimuli, including TNFa, photodynamic therapy and UVB, have been shown to inhibit de novo SM synthesis. [14][15][16][17] Although homotrimerization of CERT (ceramide transfer protein) has been implicated in UVB-mediated inhibition of SM synthesis, the underlying mechanisms involved are largely unknown.…”