Perturbation of membrane microdomains reduces mitogenic signaling and increases susceptibility to apoptosis after T cell receptor stimulation.
Acid sphingomyelinase-deficient (asmase-/-) mice generated by gene targeting abundantly store sphingomyelin in the reticuloendothelial system of liver, spleen, bone marrow, and in brain. Liver cells of asmase-/- mice accumulate sphingomyelin and glycosphingolipids in purified lipid bilayers of microsomes, Golgi, and the plasma membrane, but cholesterol is depleted in the plasma membrane. Detergent-insoluble glycolipid-enriched membrane microdomains (GEM) can be isolated from hepatocytes, embryonic fibroblasts, and splenocytes of wild-type, but not of asmase-/- mice, by sucrose gradient density centrifugation. Lck and other Src-family kinases are reduced in isopycnic fractions of asmase-/- splenocytes compared to GEM-containing fractions of wild-type cells. The proliferation of asmase-/- T lymphocytes is reduced, whereas their susceptibility to Fas-induced apoptosis is increased after T cell receptor (TCR) stimulation. TNF receptor I signaling remains unimpaired. The perturbation of GEM impairs tyrosine phosphorylation and, consequently, mitogenic signaling of the TCR. Reduced MAPK activity-dependent FLICE-like inhibitory protein (FLIP) expression in asmase-/- T lymphocytes increases their sensitivity towards Fas-mediated apoptosis.
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Laboratory of Molecular Neuroscience, Institute of Biochemistry, Faculty of Medicine, University of Cologne, D-50931 Cologne, Germany.
Stoffel
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D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004705:Endocytosis; D005347:Fibroblasts / Q000378:metabolism; D006028:Glycosphingolipids / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000166:cytology / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008938:Mitosis; D010766:Phosphorylation; D010873:Pinocytosis; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000172:deficiency / Q000235:genetics; D013109:Sphingomyelins / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins; C506387:Cflar protein, mouse; D017931:DNA Primers; D006028:Glycosphingolipids; D047908:Intracellular Signaling Peptides and Proteins; D008563:Membrane Lipids; D011948:Receptors, Antigen, T-Cell; D013109:Sphingomyelins; D019014:fas Receptor; D014443:Tyrosine; D013108:Sphingomyelin Phosphodiesterase