title: The involvement of caspases in the CD95(Fas/Apo-1)- but not swelling-induced cellular taurine release from Jurkat T-lymphocytes.
abstract: Following a delay of 45 min, stimulation of the CD95 (Fas/Apo-1)-receptor in Jurkat T-lymphocytes leads to the release of the osmolyte taurine, an event coinciding with apoptotic cell shrinkage. The present study has been performed to elucidate the cellular mechanisms involved in CD95-induced taurine release as compared to swelling-induced taurine release, and to explore whether taurine modifies apoptotic DNA fragmentation and cell shrinkage. Taurine release stimulated by osmotic cell swelling is insensitive to the tyrosine kinase inhibitor herbimycin A and the caspase inhibitor z-Val-Ala-Asp(OMe)-fluoromethylketone (zVAD) but is blunted in the absence of extracellular Ca2+. Conversely, the Ca2+ ionophore ionomycin stimulates taurine release. However, the taurine release following CD95 stimulation is not paralleled by an increase of cytosolic Ca2+ and not inhibited by complexation of extracellular Ca2+. None of herbimycin A, the phosphatase inhibitor vanadate, spingomyelinase or Lck56 deficiency prevent CD95-induced taurine release. In contrast, the caspase inhibitor zVAD, but not the caspase inhibitor Ac-Tyr-Val-Ala-Asp-chloromethylketone (YVAD), almost abolishes CD95-induced taurine release. Both caspase inhibitors blunt CD95-induced cell shrinkage and DNA fragmentation, zVAD being more effective than YVAD. Preloading of the cells with 40 mM taurine but not with 40 mM mannitol significantly inhibits CD95-induced DNA fragmentation (by 28%) and apoptotic cell shrinkage (by 25%). In conclusion, CD95-receptor triggering leads to caspase-dependent stimulation of cellular taurine release, which facilitates, but is not sufficient for, the triggering of apoptotic DNA fragmentation and cell shrinkage.
authors.affiliation: Physiologisches Institut, der Universität Tübingen, Germany. florian.lang@uni-tuebingen.de
authors.forename: F
authors.initials: F
authors.lastname: Lang
authors.forename: J
authors.initials: J
authors.lastname: Madlung
authors.forename: D
authors.initials: D
authors.lastname: Siemen
authors.forename: C
authors.initials: C
authors.lastname: Ellory
authors.forename: A
authors.initials: A
authors.lastname: Lepple-Wienhues
authors.forename: E
authors.initials: E
authors.lastname: Gulbins
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D048429:Cell Size / Q000187:drug effects; D002614:Chelating Agents / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects; D053222:Fas Ligand Protein; D006801:Humans; D007473:Ion Channels / Q000037:antagonists & inhibitors; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000172:deficiency; D008562:Membrane Glycoproteins / Q000378:metabolism; D009994:Osmolar Concentration; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D013108:Sphingomyelin Phosphodiesterase / Q000172:deficiency / Q000494:pharmacology; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D013654:Taurine / Q000378:metabolism* / Q000493:pharmacokinetics / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology; D019014:fas Receptor / Q000494:pharmacology*
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D002614:Chelating Agents; D015853:Cysteine Proteinase Inhibitors; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D007473:Ion Channels; D008562:Membrane Glycoproteins; C098738:N-acetyl-tyrosyl-valyl-alanyl-aspartyl chloromethyl ketone; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; D013654:Taurine; D014638:Vanadates; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D013108:Sphingomyelin Phosphodiesterase; D020169:Caspases; D002118:Calcium