Caspase-3-dependent cleavage of Bcl-2 promotes release of cytochrome c

Kirsch, D. G., Doseff, A., Chau, B. N., Lim, D. S., de Souza-Pinto, N. C., Hansford, R., Kastan, M. B., Lazebnik, Y. A., Hardwick, J. M. (1999) Caspase-3-dependent cleavage of Bcl-2 promotes release of cytochrome c. Journal of Biological Chemistry, 274 (30). pp. 21155-21161. ISSN 0021-9258

DOI: 10.1074/jbc.274.30.21155


Caspases are cysteine proteases that mediate apoptosis by proteolysis of specific substrates. Although many caspase substrates have been identified, for most substrates the physiologic caspase(s) required for cleavage is unknown. The Bcl-2 protein, which inhibits apoptosis, is cleaved at Asp-34 by caspases during apoptosis and by recombinant caspase-3 in vitro. In the present study, we show that endogenous caspase-3 is a physiologic caspase for Bcl-2. Apoptotic extracts from 293 cells cleave Bcl-2 but not Bax, even though Bax is cleaved to an 18-kDa fragment in SK-NSH cells treated with ionizing radiation. In contrast to Bcl-2, cleavage of Bax was only partially blocked by caspase inhibitors. Inhibitor profiles indicate that Bax may be cleaved by more than one type of noncaspase protease. Immunodepletion of caspase-3 from 293 extracts abolished cleavage of Bcl-2 and caspase-7, whereas immunodepletion of caspase-7 had no effect on Bcl-2 cleavage. Furthermore, MCF-7 cells, which lack caspase-3 expression, do not cleave Bcl-2 following staurosporine-induced cell death. However, transient transfection of caspase-3 into MCF-7 cells restores Bcl-2 cleavage after staurosporine treatment. These results demonstrate that in these models of apoptosis, specific cleavage of Bcl-2 requires activation of caspase-3. When the pro-apoptotic caspase cleavage fragment of Bcl-2 is transfected into baby hamster kidney cells, it localizes to mitochondria and causes the release of cytochrome c into the cytosol. Therefore, caspase-3-dependent cleavage of Bcl-2 appears to promote further caspase activation as part of a positive feedback loop for executing the cell.

Item Type: Paper
Uncontrolled Keywords: Animals Apoptosis Caspase 3 Caspases Cricetinae Cytochrome c Group Enzyme Activation HL-60 Cells Humans Proto-Oncogene Proteins c-bcl-2 Substrate Specificity
Subjects: organs, tissues, organelles, cell types and functions > cell types and functions > cell functions > apoptosis
organs, tissues, organelles, cell types and functions > cell types and functions > cell functions
CSHL Authors:
Communities: CSHL labs > Labeznik lab
Depositing User: Matt Covey
Date: 1999
Date Deposited: 12 Dec 2012 17:30
Last Modified: 12 Dec 2012 17:30
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