title: Possible involvement of cyclophilin B and caspase-activated deoxyribonuclease in the induction of chromosomal DNA degradation in TCR-stimulated thymocytes.
abstract: TCR engagement of immature CD4(+)CD8(+) thymocytes induces clonal maturation (positive selection) as well as clonal deletion (negative selection) in the thymus. However, the cell death execution events of thymocytes during the negative selection process remain obscure. Using a cell-free system, we identified two different DNase activities in the cytosol of in vivo anti-TCR-stimulated murine thymocytes: one that induced chromosomal DNA fragmentation, which was inhibited by an inhibitor of caspase-activated DNase, and another that induced plasmid DNA degradation, which was not inhibited by an inhibitor of caspase-activated DNase. We purified the protein to homogeneity that induced plasmid DNA degradation from the cytosol of anti-CD3-stimulated thymocytes and found that it is identical with cyclophilin B (Cyp B), which was reported to locate in endoplasmic reticulum. Ab against Cyp B specifically inhibited the DNA degradation activity in the cytosol of anti-CD3-stimulated thymocytes. Furthermore, recombinant Cyp B induced DNA degradation of naked nuclei, but did not induce internucleosomal DNA fragmentation. Finally, we demonstrated that TCR engagement of a murine T cell line (EL4) with anti-CD3/CD28 resulted in the release of Cyp B from the microsome fraction to the cytosol/nuclear fraction. Our data strongly suggest that both active caspase-activated DNase and Cyp B may participate in the induction of chromosomal DNA degradation during cell death execution of TCR-stimulated thymocytes.
authors.affiliation: Department of Immunology and Second Department of Surgery, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nagata
authors.forename: H
authors.initials: H
authors.lastname: Kishi
authors.forename: Q L
authors.initials: QL
authors.lastname: Liu
authors.forename: T
authors.initials: T
authors.lastname: Yoshino
authors.forename: T
authors.initials: T
authors.lastname: Matsuda
authors.forename: Z X
authors.initials: ZX
authors.lastname: Jin
authors.forename: K
authors.initials: K
authors.lastname: Murayama
authors.forename: K
authors.initials: K
authors.lastname: Tsukada
authors.forename: A
authors.initials: A
authors.lastname: Muraguchi
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D017209:Apoptosis / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000276:immunology; D002467:Cell Nucleus / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D002474:Cell-Free System / Q000276:immunology; D002850:Chromatography, Gel; D002875:Chromosomes / Q000378:metabolism; D021983:Cyclophilins / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D003600:Cytosol / Q000276:immunology / Q000378:metabolism; D053938:DNA Fragmentation; D003851:Deoxyribonucleases / Q000502:physiology*; D004789:Enzyme Activation / Q000276:immunology; D007274:Injections, Intraperitoneal; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D008822:Mice, Transgenic; D008861:Microsomes / Q000276:immunology / Q000378:metabolism; D010446:Peptide Fragments / Q000302:isolation & purification; D019696:Peptidylprolyl Isomerase; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D013347:Subcellular Fractions / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014461:Ultracentrifugation
chemical_list: D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D010446:Peptide Fragments; D011948:Receptors, Antigen, T-Cell; C081786:cyclophilin B; D003851:Deoxyribonucleases; C109663:caspase-activated deoxyribonuclease; D020169:Caspases; D021983:Cyclophilins; D019696:Peptidylprolyl Isomerase