Apoptotic pathways are selectively activated by granzyme A and/or granzyme B in CTL-mediated target cell lysis.
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.
Pardo
Julián
J
Departmento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, E-50009 Zaragoza, Spain.
Bosque
Alberto
A
Brehm
Reina
R
Wallich
Reinhard
R
Naval
Javier
J
Müllbacher
Arno
A
Anel
Alberto
A
Simon
Markus M
MM
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
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