title: Apoptotic pathways are selectively activated by granzyme A and/or granzyme B in CTL-mediated target cell lysis.
abstract: Purified cytolytic T lymphocyte (CTL) proteases granzyme (gzm)A and gzmB with sublytic dose of perforin (perf) initiate distinct proapoptotic pathways. Their physiological relevance in CTL-mediated target cell apoptosis is elusive. Using ex vivo virus-immune CD8(+) T cells from mice deficient in perf, gzmA and/or gzmB, and the Fas-resistant EL4.F15 tumor target cell, we show that (a) CTL from gzmA(-/-) or gzmB(-/-) mice similarly induced early proapoptotic features, such as phosphatidyl serine (PS) exposure on plasma membrane, Delta Psi(m) loss, and reactive oxygen radical generation, though with distinct kinetics; (b) CTL from gzmA(-/-) but not from gzmB(-/-) mice activate caspase 3 and 9; (c) PS exposure induced by CTL from gzmA(-/-) or gzmB(-/-) mice is prevented, respectively, by caspase inhibitors or by reactive oxygen scavengers without interfering with target cell death; and (d) all gzm-induced apoptotic features analyzed depend critically on perf. Thus, perf is the principal regulator in CTL-mediated and gzm-facilitated intracellular processes. The ability of gzmA and gzmB to induce multiple independent cell death pathways may be the hosts response to circumvent evasion strategies of pathogens and tumors.
authors.affiliation: Departmento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, E-50009 Zaragoza, Spain.
authors.forename: Julián
authors.initials: J
authors.lastname: Pardo
authors.forename: Alberto
authors.initials: A
authors.lastname: Bosque
authors.forename: Reina
authors.initials: R
authors.lastname: Brehm
authors.forename: Reinhard
authors.initials: R
authors.lastname: Wallich
authors.forename: Javier
authors.initials: J
authors.lastname: Naval
authors.forename: Arno
authors.initials: A
authors.lastname: Müllbacher
authors.forename: Alberto
authors.initials: A
authors.lastname: Anel
authors.forename: Markus M
authors.initials: MM
authors.lastname: Simon
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D053804:Granzymes; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000502:physiology; D008564:Membrane Potentials; D051379:Mice; D018345:Mice, Knockout; D054353:Perforin; D010718:Phosphatidylserines / Q000378:metabolism; D052899:Pore Forming Cytotoxic Proteins; D017382:Reactive Oxygen Species / Q000378:metabolism; D012697:Serine Endopeptidases / Q000172:deficiency / Q000502:physiology*; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology* / Q000276:immunology; D013997:Time Factors
chemical_list: D008562:Membrane Glycoproteins; D010718:Phosphatidylserines; D052899:Pore Forming Cytotoxic Proteins; D017382:Reactive Oxygen Species; D054353:Perforin; D053804:Granzymes; C509214:Gzmb protein, mouse; D012697:Serine Endopeptidases