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Ordering the cytochrome c-initiated caspase cascade: hierarchical activation of caspases-2, -3, -6, -7, -8, and -10 in a caspase-9-dependent manner.

Slee EA, Harte MT, Kluck RM, Wolf BB, Casiano CA, Newmeyer DD, Wang HG, Reed JC, Nicholson DW, Alnemri ES, Green DR, Martin SJ - J. Cell Biol. (1999)

Bottom Line: Here, we report that six additional caspases (caspases-2, -3, -6, -7, -8, and -10) are processed in cell-free extracts in response to cytochrome c, and that three others (caspases-1, -4, and -5) failed to be activated under the same conditions.Immunodepletion of caspases-3, -6, and -7 from cell extracts enabled us to order the sequence of caspase activation events downstream of caspase-9 and reveal the presence of a branched caspase cascade.Caspase-3 is required for the activation of four other caspases (-2, -6, -8, and -10) in this pathway and also participates in a feedback amplification loop involving caspase-9.

View Article: PubMed Central - PubMed

Affiliation: Molecular Cell Biology Laboratory, Department of Biology, National University of Ireland, Maynooth, Co. Kildare, Ireland.

ABSTRACT
Exit of cytochrome c from mitochondria into the cytosol has been implicated as an important step in apoptosis. In the cytosol, cytochrome c binds to the CED-4 homologue, Apaf-1, thereby triggering Apaf-1-mediated activation of caspase-9. Caspase-9 is thought to propagate the death signal by triggering other caspase activation events, the details of which remain obscure. Here, we report that six additional caspases (caspases-2, -3, -6, -7, -8, and -10) are processed in cell-free extracts in response to cytochrome c, and that three others (caspases-1, -4, and -5) failed to be activated under the same conditions. In vitro association assays confirmed that caspase-9 selectively bound to Apaf-1, whereas caspases-1, -2, -3, -6, -7, -8, and -10 did not. Depletion of caspase-9 from cell extracts abrogated cytochrome c-inducible activation of caspases-2, -3, -6, -7, -8, and -10, suggesting that caspase-9 is required for all of these downstream caspase activation events. Immunodepletion of caspases-3, -6, and -7 from cell extracts enabled us to order the sequence of caspase activation events downstream of caspase-9 and reveal the presence of a branched caspase cascade. Caspase-3 is required for the activation of four other caspases (-2, -6, -8, and -10) in this pathway and also participates in a feedback amplification loop involving caspase-9.

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Schematic representation of events that take  place distal to the entry of cytochrome c to the cytoplasm.  The mitochondrial apoptosome is formed upon exit  of cytochrome c from the mitochondrial intermembrane  space, possibly triggered by  either Bax or Bid. Upon activation, caspase-9 may disengage from the cytochrome  c/Apaf-1 complex in order to  activate downstream caspases,  alternatively, downstream caspases may also become recruited to this apoptosome  via suitable adaptor proteins.
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Figure 11: Schematic representation of events that take place distal to the entry of cytochrome c to the cytoplasm. The mitochondrial apoptosome is formed upon exit of cytochrome c from the mitochondrial intermembrane space, possibly triggered by either Bax or Bid. Upon activation, caspase-9 may disengage from the cytochrome c/Apaf-1 complex in order to activate downstream caspases, alternatively, downstream caspases may also become recruited to this apoptosome via suitable adaptor proteins.

Mentions: In contrast to the effects seen after depletion of caspases-9, -3, or -6, immunodepletion of caspase-7 from the extracts failed to have any detectable inhibitory effects on any of the caspase processing events observed in the presence of cytochrome c (Fig. 10 B). Taken together, these data suggest an order of caspase activation events that take place distal to entry of cytochrome c into the cytosol (Fig. 11).


Ordering the cytochrome c-initiated caspase cascade: hierarchical activation of caspases-2, -3, -6, -7, -8, and -10 in a caspase-9-dependent manner.

Slee EA, Harte MT, Kluck RM, Wolf BB, Casiano CA, Newmeyer DD, Wang HG, Reed JC, Nicholson DW, Alnemri ES, Green DR, Martin SJ - J. Cell Biol. (1999)

Schematic representation of events that take  place distal to the entry of cytochrome c to the cytoplasm.  The mitochondrial apoptosome is formed upon exit  of cytochrome c from the mitochondrial intermembrane  space, possibly triggered by  either Bax or Bid. Upon activation, caspase-9 may disengage from the cytochrome  c/Apaf-1 complex in order to  activate downstream caspases,  alternatively, downstream caspases may also become recruited to this apoptosome  via suitable adaptor proteins.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132895&req=5

Figure 11: Schematic representation of events that take place distal to the entry of cytochrome c to the cytoplasm. The mitochondrial apoptosome is formed upon exit of cytochrome c from the mitochondrial intermembrane space, possibly triggered by either Bax or Bid. Upon activation, caspase-9 may disengage from the cytochrome c/Apaf-1 complex in order to activate downstream caspases, alternatively, downstream caspases may also become recruited to this apoptosome via suitable adaptor proteins.
Mentions: In contrast to the effects seen after depletion of caspases-9, -3, or -6, immunodepletion of caspase-7 from the extracts failed to have any detectable inhibitory effects on any of the caspase processing events observed in the presence of cytochrome c (Fig. 10 B). Taken together, these data suggest an order of caspase activation events that take place distal to entry of cytochrome c into the cytosol (Fig. 11).

Bottom Line: Here, we report that six additional caspases (caspases-2, -3, -6, -7, -8, and -10) are processed in cell-free extracts in response to cytochrome c, and that three others (caspases-1, -4, and -5) failed to be activated under the same conditions.Immunodepletion of caspases-3, -6, and -7 from cell extracts enabled us to order the sequence of caspase activation events downstream of caspase-9 and reveal the presence of a branched caspase cascade.Caspase-3 is required for the activation of four other caspases (-2, -6, -8, and -10) in this pathway and also participates in a feedback amplification loop involving caspase-9.

View Article: PubMed Central - PubMed

Affiliation: Molecular Cell Biology Laboratory, Department of Biology, National University of Ireland, Maynooth, Co. Kildare, Ireland.

ABSTRACT
Exit of cytochrome c from mitochondria into the cytosol has been implicated as an important step in apoptosis. In the cytosol, cytochrome c binds to the CED-4 homologue, Apaf-1, thereby triggering Apaf-1-mediated activation of caspase-9. Caspase-9 is thought to propagate the death signal by triggering other caspase activation events, the details of which remain obscure. Here, we report that six additional caspases (caspases-2, -3, -6, -7, -8, and -10) are processed in cell-free extracts in response to cytochrome c, and that three others (caspases-1, -4, and -5) failed to be activated under the same conditions. In vitro association assays confirmed that caspase-9 selectively bound to Apaf-1, whereas caspases-1, -2, -3, -6, -7, -8, and -10 did not. Depletion of caspase-9 from cell extracts abrogated cytochrome c-inducible activation of caspases-2, -3, -6, -7, -8, and -10, suggesting that caspase-9 is required for all of these downstream caspase activation events. Immunodepletion of caspases-3, -6, and -7 from cell extracts enabled us to order the sequence of caspase activation events downstream of caspase-9 and reveal the presence of a branched caspase cascade. Caspase-3 is required for the activation of four other caspases (-2, -6, -8, and -10) in this pathway and also participates in a feedback amplification loop involving caspase-9.

Show MeSH