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

Elizabeth A. Slee, Mary T. Harte, Ruth M. Kluck, Beni B. Wolf, Carlos A. Casiano, Donald D. Newmeyer, Hong Gang Wang, John C. Reed, Donald W. Nicholson, Emad S. Alnemri, Douglas R. Green, Seamus J. Martin

Research output: Contribution to journalArticlepeer-review

1590 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)281-292
Number of pages12
JournalJournal of Cell Biology
Volume144
Issue number2
DOIs
StatePublished - Jan 25 1999

All Science Journal Classification (ASJC) codes

  • Cell Biology

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