Ceramide Enables Fas to Cap and Kill

著者: Aida Cremesti, François Paris, Heike Grassmé, Nils Holler, Jürg Tschopp, Zvi Fuks, Erich Gulbins, Richard Kolesnick - Journal of Biological Chemistry 2001 被引用: 375

Recent studies suggest that trimerization of Fas is insufficient for apoptosis induction and indicate that super-aggregation of trimerized Fas might be prerequisite. For many cell surface receptors, cross-linking by multivalent ligands or antibodies induces their lateral segregation within the plasma membrane and co-localization into “caps” on one pole of the cell. In this study, we show that capping of Fas is essential for optimal function and that capping is ceramide-dependent. In Jurkat T lymphocytes and in primary cultures of hepatocytes, ceramide elevation was detected as early as 15–30 s and peaked at 1 min after CH-11 and Jo2 anti-Fas antibody treatment, respectively. Capping was detected 30 s after Fas ligation, peaked at 2 min, and was maintained at a lower level for as long as 30 min in both cell types. Ceramide generation appeared essential for capping. Acid sphingomyelinase− /− hepatocytes were defective in Jo2-induced ceramide generation, capping, and apoptosis, and nanomolar concentrations of C16-ceramide restored these events. To further explore the role of ceramide in capping of Fas, we employed FLAG-tagged soluble Fas ligand (sFasL), which binds trimerized Fas but is unable to induce capping or apoptosis in Jurkat cells. Cross-linking of sFasL with M2 anti-FLAG antibody induced both events. Pretreatment of cells with natural C16-ceramide bypassed the necessity for forced antibody cross-linking and enabled sFasL to cap and kill. The presence of intact sphingolipid-enriched membrane domains may be essential for Fas capping since their disruption with cholesterol-depleting agents abrogated capping and prevented apoptosis. These data suggest that capping is a ceramide-dependent event required for optimal Fas signaling in some cells. Recent studies suggest that trimerization of Fas is insufficient for apoptosis induction and indicate that super-aggregation of trimerized Fas might be prerequisite. For many cell surface receptors, cross-linking by multivalent ligands or antibodies induces their lateral segregation within the plasma membrane and co-localization into “caps” on one pole of the cell. In this study, we show that capping of Fas is essential for optimal function and that capping is ceramide-dependent. In Jurkat T lymphocytes and in primary cultures of hepatocytes, ceramide elevation was detected as early as 15–30 s and peaked at 1 min after CH-11 and Jo2 anti-Fas antibody treatment, respectively. Capping was detected 30 s after Fas ligation, peaked at 2 min, and was maintained at a lower level for as long as 30 min in both cell types. Ceramide generation appeared essential for capping. Acid sphingomyelinase− /− hepatocytes were defective in Jo2-induced ceramide generation, capping, and apoptosis, and nanomolar concentrations of C16-ceramide restored these events. To further explore the role of ceramide in capping of Fas, we employed FLAG-tagged soluble Fas ligand (sFasL), which binds trimerized Fas but is unable to induce capping or apoptosis in Jurkat cells. Cross-linking of sFasL with M2 anti-FLAG antibody induced both events. Pretreatment of cells with natural C16-ceramide bypassed the necessity for forced antibody cross-linking and enabled sFasL to cap and kill. The presence of intact sphingolipid-enriched membrane domains may be essential for Fas capping since their disruption with cholesterol-depleting agents abrogated capping and prevented apoptosis. These data suggest that capping is a ceramide-dependent event required for optimal Fas signaling in some cells. Fas-associated death domain protein terminal dUTP nick-end labeling soluble Fas ligand glycosphingolipid-enriched microdomain acid sphingomyelinase fluorescein isothiocyanate Hepes-buffered saline The current model of Fas (CD95 or APO-1) signaling suggests that engagement of Fas by its ligand or anti-Fas antibody leads to receptor trimerization and recruitment of the cytoplasmic adapter protein FADD1 (MORT-1) and pro-caspase 8 (Flice/MACH-1), (1Krammer P.H. Toxicol. Lett. 1998; 102–103: 131-137Crossref PubMed Scopus (38) Google Scholar, 2Scaffidi C. Fulda S. Srinivasan A. Friesen C. Li F. Tomaselli K.J. Debatin K.M. Krammer P.H. Peter M.E. EMBO J. 1998; 17: 1675-1687Crossref PubMed Scopus (2617) Google Scholar), thus forming a death-inducing signaling complex. Assembly of the death-inducing signaling complex results in release of active caspase 8, initiating the apoptotic process (1Krammer P.H. Toxicol. Lett. 1998; 102–103: 131-137Crossref PubMed Scopus (38) Google Scholar, 2Scaffidi C. Fulda S. Srinivasan A. Friesen C. Li F. Tomaselli K.J. Debatin K.M. Krammer P.H. Peter M.E. EMBO J. 1998; 17: 1675-1687Crossref PubMed Scopus (2617) Google Scholar). Peter and co-workers (2Scaffidi C. Fulda S. Srinivasan A. Friesen C. Li F. Tomaselli K.J. Debatin K.M. Krammer P.H. Peter M.E. EMBO J. 1998; 17: 1675-1687Crossref PubMed Scopus (2617) Google Scholar) provide evidence that after caspase 8 activation, Fas signals apoptosis via two different mechanisms. In Type I cells, caspase 8 directly activates a hierarchical cascade of effector caspases, involving among others caspases 3 and 7. Apoptosis in Type II cells occurs after minimal caspase 8 activation and proceeds through an amplification cascade involving mitochondrial dysfunction, the release of mitochondrial cytochrome c, and activation of Apaf-1 and caspase 9. Commitment to apoptosis ensues subsequently via effector caspase activation.Whereas this model is widely accepted, recent data are incompatible with portions of this paradigm. Siegel et al. (3Siegel R.M. Frederiksen J.K. Zacharias D.A. Chan F.K. Johnson M. Lynch D. Tsien R.Y. Lenardo M.J. Science. 2000; 288: 2354-2357Crossref PubMed Scopus (534) Google Scholar) reported recently that Fas may already exist in a trimerized state before ligand interaction and that preassembly may be required for binding Fas ligand and triggering cell death. Homotrimer generation in the absence of ligand is mediated by the pre-ligand assembly domain located within the extracellular amino-terminal region of the receptor. It was further suggested that Fas ligand may orchestrate the multimerization of trimerized receptors, generating aggregates of activated receptors, thus producing high local concentration of Fas death domain complexes (4Golstein P. Science. 2000; 288: 2328-2329Crossref PubMed Scopus (35) Google Scholar). Consistent with this paradigm, FLAG-tagged soluble Fas ligand (sFasL) that retained the capacity to interact with Fas failed to induce apoptosis unless it was cross-linked with anti-FLAG antibody, apparently forming a super-aggregated state required for Fas signaling (5Schneider P. Holler N. Bodmer J.L. Hahne M. Frei A. J. J. 1998; PubMed Scopus Google and of cell surface binding to their ligands reported for a of receptors, the J. PubMed Scopus Google Scholar), PubMed Scopus Google Scholar), S. A. F. PubMed Scopus Google Scholar), D. PubMed Scopus Google Scholar), and receptor C. J. R.M. C. 1998; PubMed Scopus Google Scholar, M.J. K.M. J. Google Scholar). In of these of were to one pole of the cell and to a cap via an process involving PubMed Scopus Google Scholar, D. PubMed Scopus Google Scholar). capping to of extracellular signals by local assembly of the signaling For et J. A. J. 2000; PubMed Scopus Google Scholar) show activation of the of required for receptor in and These and studies the that the assembly of in is for and for of their is evidence for a role of capping in Fas signaling of apoptosis. et al. C. P. F. M. 1998; PubMed Scopus Google Scholar) that Fas ligand induced Fas capping and apoptosis in and et al. J. M. Krammer P.H. P. 1998; Google Scholar) defective Fas capping and apoptosis in cell evidence suggests that membrane as glycosphingolipid-enriched or membrane may be with cap are membrane of and membrane PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). is into plasma membrane as that are in a of membrane in cells D.A. J.K. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar), M. M. A. J. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar), and cell surface EMBO J. PubMed Scopus Google Scholar, Li C. 1998; PubMed Scopus Google Scholar, D. J. PubMed Scopus Google Scholar, J.K. J. PubMed Scopus Google Scholar, M. J. PubMed Scopus Google Scholar, 1998; PubMed Scopus Google Scholar, C. C. J. C. M. EMBO J. 1998; 17: PubMed Scopus Google Scholar). It suggested that these provide a for segregation of of and the and of in of abrogated signaling through this in a of cell P.H. J. 1998; PubMed Scopus Google Scholar). abrogated capping of and the receptor on the surface of lymphocytes M.J. J. PubMed Scopus Google Scholar, A. A. PubMed Scopus Google Scholar). that of cells abrogated but apoptosis J. Google Scholar). cell as that the model of Fas signaling to the role of the ceramide in the apoptotic are of ceramide elevation Fas activation M. J. F. 1998; PubMed Scopus Google Scholar, P. M. A. J. PubMed Scopus Google Scholar, A. S. C. F. A. D. PubMed Scopus Google Scholar, F. A. J. A. J. PubMed Scopus Google Scholar, S. A. S. S. A. PubMed Scopus Google Scholar), by acid or sphingomyelinase P. M. A. J. PubMed Scopus Google Scholar, M.J. A. S. F. J. 2000; PubMed Scopus Google Scholar). Recent evidence that ceramide generation is and occurs before to the effector of the apoptotic process C. J. 2000; PubMed Scopus Google Scholar). In these the of or pro-caspase 8 into or cells was to the induced apoptosis. these and pro-caspase 8 induced ceramide generation that was by the caspase ceramide in to Fas is in the apoptotic process or it an a of and co-workers J. 1998; PubMed Scopus Google Scholar) that which an a of in ceramide generation and apoptosis, and co-workers J. J. 1998; PubMed Scopus Google Scholar). we evidence for the role of ceramide in apoptosis F. A. J. A. J. PubMed Scopus Google Scholar, S. F. M. A. J. 2000; PubMed Google Scholar). /− failed to ceramide elevation in to Jo2 anti-Fas antibody and were 1 to apoptotic death The of nanomolar of natural C16-ceramide /− hepatocytes on apoptosis, restored Fas for natural ceramide and Fas The of ceramide to the Fas of the evidence that ceramide is for at one of apoptosis. The of ceramide of apoptosis the we show that in to Fas apoptosis via Fas and cap Jurkat T lymphocytes and primary cultures of hepatocytes to CH-11 or Jo2 anti-Fas antibody, with ceramide capping, and hepatocytes were defective in these but nanomolar concentrations of natural C16-ceramide restored capping and apoptosis. sFasL failed to induce capping or apoptosis in Jurkat cells, but cross-linking of sFasL with M2 anti-FLAG antibody restored both Pretreatment with C16-ceramide bypassed the necessity for forced M2 antibody cross-linking and enabled sFasL to cap and induce apoptosis. of sphingolipid-enriched membrane domains may be for the Fas since their disruption with cholesterol-depleting agents abrogated capping and prevented apoptosis. These data provide a for the of ceramide in one of studies provide the role of ceramide in Fas Ceramide is via within of Fas ligation, Fas and capping in Jurkat cells and primary cultures of The for ceramide generation, capping, and apoptosis within cell evidence a role for ceramide in the hepatocytes a in capping. ceramide is for capping hepatocytes is by the of Fas capping by nanomolar of natural evidence that capping may be for optimal apoptosis is studies cholesterol-depleting which P.H. J. 1998; PubMed Scopus Google Scholar), and in the capping and apoptosis. These domains for ceramide signaling in to P. J. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar), S. M.E. M. J. PubMed Scopus Google Scholar), J. PubMed Scopus Google Scholar), and A. 2000; PubMed Scopus Google Scholar, A. 1998; PubMed Scopus Google Scholar) via an P. J. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google J. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar, J. 1998; PubMed Scopus Google Scholar). show into A. A. J. J. PubMed Scopus Google Scholar) and ceramide elevation within and Fas of show that ceramide-dependent capping be bypassed by forced of cross-linking Jo2 by binding to S. F. M. A. J. 2000; PubMed Google Scholar) or the of Jo2 to J. M. PubMed Scopus Google Scholar, Google Scholar) and apoptosis in the absence of forced a process is For for apoptosis. In for S. F. M. A. J. 2000; PubMed Google Scholar), of and S. F. M. A. J. 2000; PubMed Google Scholar), of and which model the Fas in it is cells that apoptosis of as or the cell for the cap In this are for ceramide generation as of sphingomyelinase or which might be for studies of ceramide in model provide into the that may ceramide to capping. In cells, the of the plasma which is an of and may be by and of within the A. J. Scopus Google Scholar). which the membrane J. 1998; PubMed Scopus Google Scholar, S. J. PubMed Google Scholar), to membrane lateral of membrane to the capacity to capping is the generation of of of ceramide in model membrane of protein A. J. 2000; PubMed Scopus Google Scholar). In ceramide the to into as detected by a of J. Scopus Google Scholar), the of and J.L. A. J. PubMed Scopus Google Scholar), and M. J. PubMed Scopus Google Scholar). these are in ceramide might into of into M.J. J. PubMed Scopus Google Scholar). The interaction of Fas with these might a high local concentration of Fas and its Consistent with this paradigm, a recently antibody detected high ceramide within Fas by for this studies that activation is C. J. 2000; PubMed Scopus Google Scholar), to be a caspase trimerized Fas or Fas activation and ceramide generation is the studies by al. C. J. 2000; PubMed Scopus Google Scholar) suggest that Fas which may be to induce apoptosis, may be to ceramide receptor cap C16-ceramide capping with a of ceramide and that receptor interaction with but death-inducing signaling complex results with ceramide and the anti-Fas antibody in Jurkat the of Fas capping, recent studies show that within the membrane of Fas is for Fas to in ceramide a that occurs Fas, as with M. M. A. PubMed Scopus Google Scholar), binds its might to the membrane that it interact with at the receptor within a it is of the death-inducing signaling receptor capping may provide the for of and caspase 8, which of the Fas D.A. Siegel R.M. Lenardo M.J. J. 1998; PubMed Scopus Google Scholar, M. PubMed Scopus Google Scholar, A. S. J. 1998; PubMed Scopus Google Scholar), to the apoptotic a for signaling through ceramide studies are to these it that this may be a for receptor as capping of and signaling through and are by or disruption of The current model of Fas (CD95 or APO-1) signaling suggests that engagement of Fas by its ligand or anti-Fas antibody leads to receptor trimerization and recruitment of the cytoplasmic adapter protein FADD1 (MORT-1) and pro-caspase 8 (Flice/MACH-1), (1Krammer P.H. Toxicol. Lett. 1998; 102–103: 131-137Crossref PubMed Scopus (38) Google Scholar, 2Scaffidi C. Fulda S. Srinivasan A. Friesen C. Li F. Tomaselli K.J. Debatin K.M. Krammer P.H. Peter M.E. EMBO J. 1998; 17: 1675-1687Crossref PubMed Scopus (2617) Google Scholar), thus forming a death-inducing signaling complex. Assembly of the death-inducing signaling complex results in release of active caspase 8, initiating the apoptotic process (1Krammer P.H. Toxicol. Lett. 1998; 102–103: 131-137Crossref PubMed Scopus (38) Google Scholar, 2Scaffidi C. Fulda S. Srinivasan A. Friesen C. Li F. Tomaselli K.J. Debatin K.M. Krammer P.H. Peter M.E. EMBO J. 1998; 17: 1675-1687Crossref PubMed Scopus (2617) Google Scholar). Peter and co-workers (2Scaffidi C. Fulda S. Srinivasan A. Friesen C. Li F. Tomaselli K.J. Debatin K.M. Krammer P.H. Peter M.E. EMBO J. 1998; 17: 1675-1687Crossref PubMed Scopus (2617) Google Scholar) provide evidence that after caspase 8 activation, Fas signals apoptosis via two different mechanisms. In Type I cells, caspase 8 directly activates a hierarchical cascade of effector caspases, involving among others caspases 3 and 7. Apoptosis in Type II cells occurs after minimal caspase 8 activation and proceeds through an amplification cascade involving mitochondrial dysfunction, the release of mitochondrial cytochrome c, and activation of Apaf-1 and caspase 9. Commitment to apoptosis ensues subsequently via effector caspase this model is widely accepted, recent data are incompatible with portions of this paradigm. Siegel et al. (3Siegel R.M. Frederiksen J.K. Zacharias D.A. Chan F.K. Johnson M. Lynch D. Tsien R.Y. Lenardo M.J. Science. 2000; 288: 2354-2357Crossref PubMed Scopus (534) Google Scholar) reported recently that Fas may already exist in a trimerized state before ligand interaction and that preassembly may be required for binding Fas ligand and triggering cell death. Homotrimer generation in the absence of ligand is mediated by the pre-ligand assembly domain located within the extracellular amino-terminal region of the receptor. It was further suggested that Fas ligand may orchestrate the multimerization of trimerized receptors, generating aggregates of activated receptors, thus producing high local concentration of Fas death domain complexes (4Golstein P. Science. 2000; 288: 2328-2329Crossref PubMed Scopus (35) Google Scholar). Consistent with this paradigm, FLAG-tagged soluble Fas ligand (sFasL) that retained the capacity to interact with Fas failed to induce apoptosis unless it was cross-linked with anti-FLAG antibody, apparently forming a super-aggregated state required for Fas signaling (5Schneider P. Holler N. Bodmer J.L. Hahne M. Frei A. J. J. 1998; PubMed Scopus Google Scholar). and of cell surface binding to their ligands reported for a of receptors, the J. PubMed Scopus Google Scholar), PubMed Scopus Google Scholar), S. A. F. PubMed Scopus Google Scholar), D. PubMed Scopus Google Scholar), and receptor C. J. R.M. C. 1998; PubMed Scopus Google Scholar, M.J. K.M. J. Google Scholar). In of these of were to one pole of the cell and to a cap via an process involving PubMed Scopus Google Scholar, D. PubMed Scopus Google Scholar). capping to of extracellular signals by local assembly of the signaling For et J. A. J. 2000; PubMed Scopus Google Scholar) show activation of the of required for receptor in and These and studies the that the assembly of in is for and for of their is evidence for a role of capping in Fas signaling of apoptosis. et al. C. P. F. M. 1998; PubMed Scopus Google Scholar) that Fas ligand induced Fas capping and apoptosis in and et al. J. M. Krammer P.H. P. 1998; Google Scholar) defective Fas capping and apoptosis in cell evidence suggests that membrane as glycosphingolipid-enriched or membrane may be with cap are membrane of and membrane PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). is into plasma membrane as that are in a of membrane in cells D.A. J.K. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar), M. M. A. J. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar), and cell surface EMBO J. PubMed Scopus Google Scholar, Li C. 1998; PubMed Scopus Google Scholar, D. J. PubMed Scopus Google Scholar, J.K. J. PubMed Scopus Google Scholar, M. J. PubMed Scopus Google Scholar, 1998; PubMed Scopus Google Scholar, C. C. J. C. M. EMBO J. 1998; 17: PubMed Scopus Google Scholar). It suggested that these provide a for segregation of of and the and of in of abrogated signaling through this in a of cell P.H. J. 1998; PubMed Scopus Google Scholar). abrogated capping of and the receptor on the surface of lymphocytes M.J. J. PubMed Scopus Google Scholar, A. A. PubMed Scopus Google Scholar). that of cells abrogated but apoptosis J. Google Scholar). cell as that the model of Fas signaling to the role of the ceramide in the apoptotic are of ceramide elevation Fas activation M. J. F. 1998; PubMed Scopus Google Scholar, P. M. A. J. PubMed Scopus Google Scholar, A. S. C. F. A. D. PubMed Scopus Google Scholar, F. A. J. A. J. PubMed Scopus Google Scholar, S. A. S. S. A. PubMed Scopus Google Scholar), by acid or sphingomyelinase P. M. A. J. PubMed Scopus Google Scholar, M.J. A. S. F. J. 2000; PubMed Scopus Google Scholar). Recent evidence that ceramide generation is and occurs before to the effector of the apoptotic process C. J. 2000; PubMed Scopus Google Scholar). In these the of or pro-caspase 8 into or cells was to the induced apoptosis. these and pro-caspase 8 induced ceramide generation that was by the caspase ceramide in to Fas is in the apoptotic process or it an a of and co-workers J. 1998; PubMed Scopus Google Scholar) that which an a of in ceramide generation and apoptosis, and co-workers J. J. 1998; PubMed Scopus Google Scholar). we evidence for the role of ceramide in apoptosis F. A. J. A. J. PubMed Scopus Google Scholar, S. F. M. A. J. 2000; PubMed Google Scholar). /− failed to ceramide elevation in to Jo2 anti-Fas antibody and were 1 to apoptotic death The of nanomolar of natural C16-ceramide /− hepatocytes on apoptosis, restored Fas for natural ceramide and Fas The of ceramide to the Fas of the evidence that ceramide is for at one of apoptosis. The of ceramide of apoptosis In the we show that in to Fas apoptosis via Fas and cap Jurkat T lymphocytes and primary cultures of hepatocytes to CH-11 or Jo2 anti-Fas antibody, with ceramide capping, and hepatocytes were defective in these but nanomolar concentrations of natural C16-ceramide restored capping and apoptosis. sFasL failed to induce capping or apoptosis in Jurkat cells, but cross-linking of sFasL with M2 anti-FLAG antibody restored both Pretreatment with C16-ceramide bypassed the necessity for forced M2 antibody cross-linking and enabled sFasL to cap and induce apoptosis. of sphingolipid-enriched membrane domains may be for the Fas since their disruption with cholesterol-depleting agents abrogated capping and prevented apoptosis. These data provide a for the of ceramide in one of apoptosis. studies provide the role of ceramide in Fas Ceramide is via within of Fas ligation, Fas and capping in Jurkat cells and primary cultures of The for ceramide generation, capping, and apoptosis within cell evidence a role for ceramide in the hepatocytes a in capping. ceramide is for capping hepatocytes is by the of Fas capping by nanomolar of natural evidence that capping may be for optimal apoptosis is studies cholesterol-depleting which P.H. J. 1998; PubMed Scopus Google Scholar), and in the capping and apoptosis. These domains for ceramide signaling in to P. J. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar), S. M.E. M. J. PubMed Scopus Google Scholar), J. PubMed Scopus Google Scholar), and A. 2000; PubMed Scopus Google Scholar, A. 1998; PubMed Scopus Google Scholar) via an P. J. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google J. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar, J. 1998; PubMed Scopus Google Scholar). show into A. A. J. J. PubMed Scopus Google Scholar) and ceramide elevation within and Fas of show that ceramide-dependent capping be bypassed by forced of cross-linking Jo2 by binding to S. F. M. A. J. 2000; PubMed Google Scholar) or the of Jo2 to J. M. PubMed Scopus Google Scholar, Google Scholar) and apoptosis in the absence of forced a process is For for apoptosis. In for S. F. M. A. J. 2000; PubMed Google Scholar), of and S. F. M. A. J. 2000; PubMed Google Scholar), of and which model the Fas in it is cells that apoptosis of as or the cell for the cap In this are for ceramide generation as of sphingomyelinase or which might be for studies of ceramide in model provide into the that may ceramide to capping. In cells, the of the plasma which is an of and may be by and of within the A. J. Scopus Google Scholar). which the membrane J. 1998; PubMed Scopus Google Scholar, S. J. PubMed Google Scholar), to membrane lateral of membrane to the capacity to capping is the generation of of of ceramide in model membrane of protein A. J. 2000; PubMed Scopus Google Scholar). In ceramide the to into as detected by a of J. Scopus Google Scholar), the of and J.L. A. J. PubMed Scopus Google Scholar), and M. J. PubMed Scopus Google Scholar). these are in ceramide might into of into M.J. J. PubMed Scopus Google Scholar). The interaction of Fas with these might a high local concentration of Fas and its Consistent with this paradigm, a recently antibody detected high ceramide within Fas by for this studies that activation is C. J. 2000; PubMed Scopus Google Scholar), to be a caspase trimerized Fas or Fas activation and ceramide generation is the studies by al. C. J. 2000; PubMed Scopus Google Scholar) suggest that Fas which may be to induce apoptosis, may be to ceramide receptor cap C16-ceramide capping with a of ceramide and that receptor interaction with but death-inducing signaling complex results with ceramide and the anti-Fas antibody in Jurkat the of Fas capping, recent studies show that within the membrane of Fas is for Fas to in ceramide a that occurs Fas, as with M. M. A. PubMed Scopus Google Scholar), binds its might to the membrane that it interact with at the receptor within a it is of the death-inducing signaling receptor capping may provide the for of and caspase 8, which of the Fas D.A. Siegel R.M. Lenardo M.J. J. 1998; PubMed Scopus Google Scholar, M. PubMed Scopus Google Scholar, A. S. J. 1998; PubMed Scopus Google Scholar), to the apoptotic a for signaling through ceramide studies are to these it that this may be a for receptor as capping of and signaling through and are by or disruption of The studies provide the role of ceramide in Fas Ceramide is via within of Fas ligation, Fas and capping in Jurkat cells and primary cultures of The for ceramide generation, capping, and apoptosis within cell evidence a role for ceramide in the hepatocytes a in capping. ceramide is for capping hepatocytes is by the of Fas capping by nanomolar of natural evidence that capping may be for optimal apoptosis is studies cholesterol-depleting which P.H. J. 1998; PubMed Scopus Google Scholar), and in the capping and apoptosis. These domains for ceramide signaling in to P. J. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar), S. M.E. M. J. PubMed Scopus Google Scholar), J. PubMed Scopus Google Scholar), and A. 2000; PubMed Scopus Google Scholar, A. 1998; PubMed Scopus Google Scholar) via an P. J. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google J. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar, J. 1998; PubMed Scopus Google Scholar). show into A. A. J. J. PubMed Scopus Google Scholar) and ceramide elevation within and Fas of show that ceramide-dependent capping be bypassed by forced of cross-linking Jo2 by binding to S. F. M. A. J. 2000; PubMed Google Scholar) or the of Jo2 to J. M. PubMed Scopus Google Scholar, Google Scholar) and apoptosis in the absence of forced a process is For for apoptosis. In for S. F. M. A. J. 2000; PubMed Google Scholar), of and S. F. M. A. J. 2000; PubMed Google Scholar), of and which model the Fas in it is cells that apoptosis of as or the cell for the cap In this are for ceramide generation as of sphingomyelinase or which might be for capping. Recent studies of ceramide in model provide into the that may ceramide to capping. In cells, the of the plasma which is an of and may be by and of within the A. J. Scopus Google Scholar). which the membrane J. 1998; PubMed Scopus Google Scholar, S. J. PubMed Google Scholar), to membrane lateral of membrane to the capacity to capping is the generation of of of ceramide in model membrane of protein A. J. 2000; PubMed Scopus Google Scholar). In ceramide the to into as detected by a of J. Scopus Google Scholar), the of and J.L. A. J. PubMed Scopus Google Scholar), and M. J. PubMed Scopus Google Scholar). these are in ceramide might into of into M.J. J. PubMed Scopus Google Scholar). The interaction of Fas with these might a high local concentration of Fas and its Consistent with this paradigm, a recently antibody detected high ceramide within Fas by for this studies that activation is C. J. 2000; PubMed Scopus Google Scholar), to be a caspase trimerized Fas or Fas activation and ceramide generation is the studies by al. C. J. 2000; PubMed Scopus Google Scholar) suggest that Fas which may be to induce apoptosis, may be to ceramide receptor cap C16-ceramide capping with a of ceramide and that receptor interaction with but death-inducing signaling complex results with ceramide and the anti-Fas antibody in Jurkat the of Fas capping, recent studies show that within the membrane of Fas is for Fas to in ceramide a that occurs Fas, as with M. M. A. PubMed Scopus Google Scholar), binds its might to the membrane that it interact with at the receptor within a it is of the death-inducing signaling receptor capping may provide the for of and caspase 8, which of the Fas D.A. Siegel R.M. Lenardo M.J. J. 1998; PubMed Scopus Google Scholar, M. PubMed Scopus Google Scholar, A. S. J. 1998; PubMed Scopus Google Scholar), to the apoptotic The a for signaling through ceramide studies are to these it that this may be a for receptor as capping of and signaling through and are by or disruption of and for with these