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Apoptotic pathways are selectively activated by granzyme A and/or granzyme B in CTL-mediated target cell lysis.

Pardo J, Bosque A, Brehm R, Wallich R, Naval J, Müllbacher A, Anel A, Simon MM - J. Cell Biol. (2004)

Bottom Line: Their physiological relevance in CTL-mediated target cell apoptosis is elusive.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.

View Article: PubMed Central - PubMed

Affiliation: Departmento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, E-50009 Zaragoza, Spain.

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.

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Model for apoptotic pathways activated by gzmB or gzmA during CTL-induced target cell death. Perf is central to all CTL-mediated and gzmA- and gzmB-dependent apoptotic processes. GzmA and gzmB are similarly able to induce PS exposure on plasma membrane (Membrane damage) and the mitochondrial pathway(s), including ΔΨm loss and ROS generation. Only gzmB but not gzmA activates both caspase 3 and 9. GzmB-dependent activation of caspase 9 requires previous activation of caspase 3 and induction of ROS, whereas activation of caspase 3 is amplified by caspase 9 and the mitochondrial pathway. Gzm-induced PS exposure is critically dependent on caspase activation when elicited by gzmB, but not gzmA, and dependent on ROS generation when elicited by gzmA, but not gzmB. GzmB induces the mitochondrial pathway (ΔΨm loss) both via caspase-dependent and -independent pathways, and this process seems to be amplified by ROS, whereas gzmA acts via a caspase-independent pathway also amplified by ROS. Ape-1, an oxidative protein relevant for DNA repair (Fan et al., 2003b), is readily cleaved in the presence of either gzmA or gzmB, but also occurs in the absence of both gzms. However, the latter perf-facilitated and gzm-independent process(es) does not lead to target cell death. Target cell death can also occur even when the caspase pathways or the generation of ROS is inhibited, suggesting alternative, undefined gzm-elicited death pathways.
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fig7: Model for apoptotic pathways activated by gzmB or gzmA during CTL-induced target cell death. Perf is central to all CTL-mediated and gzmA- and gzmB-dependent apoptotic processes. GzmA and gzmB are similarly able to induce PS exposure on plasma membrane (Membrane damage) and the mitochondrial pathway(s), including ΔΨm loss and ROS generation. Only gzmB but not gzmA activates both caspase 3 and 9. GzmB-dependent activation of caspase 9 requires previous activation of caspase 3 and induction of ROS, whereas activation of caspase 3 is amplified by caspase 9 and the mitochondrial pathway. Gzm-induced PS exposure is critically dependent on caspase activation when elicited by gzmB, but not gzmA, and dependent on ROS generation when elicited by gzmA, but not gzmB. GzmB induces the mitochondrial pathway (ΔΨm loss) both via caspase-dependent and -independent pathways, and this process seems to be amplified by ROS, whereas gzmA acts via a caspase-independent pathway also amplified by ROS. Ape-1, an oxidative protein relevant for DNA repair (Fan et al., 2003b), is readily cleaved in the presence of either gzmA or gzmB, but also occurs in the absence of both gzms. However, the latter perf-facilitated and gzm-independent process(es) does not lead to target cell death. Target cell death can also occur even when the caspase pathways or the generation of ROS is inhibited, suggesting alternative, undefined gzm-elicited death pathways.

Mentions: In conclusion, the present study is the first account on gzmA- and/or gzmB-initiated intracellular processes during CTL-target cell interaction, a model of which is schematically represented in Fig. 7. Although the biological significance of the multiple overlapping and nonoverlapping proapoptotic pathways observed with ex vivo–derived CTLs reported herein for their in vivo performance is still elusive, this type of in vitro cytotoxic assay should help to provide a physiologically relevant perspective for gzm-mediated control of infections and cancer.


Apoptotic pathways are selectively activated by granzyme A and/or granzyme B in CTL-mediated target cell lysis.

Pardo J, Bosque A, Brehm R, Wallich R, Naval J, Müllbacher A, Anel A, Simon MM - J. Cell Biol. (2004)

Model for apoptotic pathways activated by gzmB or gzmA during CTL-induced target cell death. Perf is central to all CTL-mediated and gzmA- and gzmB-dependent apoptotic processes. GzmA and gzmB are similarly able to induce PS exposure on plasma membrane (Membrane damage) and the mitochondrial pathway(s), including ΔΨm loss and ROS generation. Only gzmB but not gzmA activates both caspase 3 and 9. GzmB-dependent activation of caspase 9 requires previous activation of caspase 3 and induction of ROS, whereas activation of caspase 3 is amplified by caspase 9 and the mitochondrial pathway. Gzm-induced PS exposure is critically dependent on caspase activation when elicited by gzmB, but not gzmA, and dependent on ROS generation when elicited by gzmA, but not gzmB. GzmB induces the mitochondrial pathway (ΔΨm loss) both via caspase-dependent and -independent pathways, and this process seems to be amplified by ROS, whereas gzmA acts via a caspase-independent pathway also amplified by ROS. Ape-1, an oxidative protein relevant for DNA repair (Fan et al., 2003b), is readily cleaved in the presence of either gzmA or gzmB, but also occurs in the absence of both gzms. However, the latter perf-facilitated and gzm-independent process(es) does not lead to target cell death. Target cell death can also occur even when the caspase pathways or the generation of ROS is inhibited, suggesting alternative, undefined gzm-elicited death pathways.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172484&req=5

fig7: Model for apoptotic pathways activated by gzmB or gzmA during CTL-induced target cell death. Perf is central to all CTL-mediated and gzmA- and gzmB-dependent apoptotic processes. GzmA and gzmB are similarly able to induce PS exposure on plasma membrane (Membrane damage) and the mitochondrial pathway(s), including ΔΨm loss and ROS generation. Only gzmB but not gzmA activates both caspase 3 and 9. GzmB-dependent activation of caspase 9 requires previous activation of caspase 3 and induction of ROS, whereas activation of caspase 3 is amplified by caspase 9 and the mitochondrial pathway. Gzm-induced PS exposure is critically dependent on caspase activation when elicited by gzmB, but not gzmA, and dependent on ROS generation when elicited by gzmA, but not gzmB. GzmB induces the mitochondrial pathway (ΔΨm loss) both via caspase-dependent and -independent pathways, and this process seems to be amplified by ROS, whereas gzmA acts via a caspase-independent pathway also amplified by ROS. Ape-1, an oxidative protein relevant for DNA repair (Fan et al., 2003b), is readily cleaved in the presence of either gzmA or gzmB, but also occurs in the absence of both gzms. However, the latter perf-facilitated and gzm-independent process(es) does not lead to target cell death. Target cell death can also occur even when the caspase pathways or the generation of ROS is inhibited, suggesting alternative, undefined gzm-elicited death pathways.
Mentions: In conclusion, the present study is the first account on gzmA- and/or gzmB-initiated intracellular processes during CTL-target cell interaction, a model of which is schematically represented in Fig. 7. Although the biological significance of the multiple overlapping and nonoverlapping proapoptotic pathways observed with ex vivo–derived CTLs reported herein for their in vivo performance is still elusive, this type of in vitro cytotoxic assay should help to provide a physiologically relevant perspective for gzm-mediated control of infections and cancer.

Bottom Line: Their physiological relevance in CTL-mediated target cell apoptosis is elusive.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.

View Article: PubMed Central - PubMed

Affiliation: Departmento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, E-50009 Zaragoza, Spain.

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.

Show MeSH
Related in: MedlinePlus