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Pro-apoptotic apoptosis protease-activating factor 1 (Apaf-1) has a cytoplasmic localization distinct from Bcl-2 or Bcl-x(L).
- Source :
-
The Journal of cell biology [J Cell Biol] 2000 May 01; Vol. 149 (3), pp. 623-34. - Publication Year :
- 2000
-
Abstract
- How Bcl-2 and its pro-survival relatives prevent activation of the caspases that mediate apoptosis is unknown, but they appear to act through the caspase activator apoptosis protease-activating factor 1 (Apaf-1). According to the apoptosome model, the Bcl-2-like proteins preclude Apaf-1 activity by sequestering the protein. To explore Apaf-1 function and to test this model, we generated monoclonal antibodies to Apaf-1 and used them to determine its localization within diverse cells by subcellular fractionation and confocal laser scanning microscopy. Whereas Bcl-2 and Bcl-x(L) were prominent on organelle membranes, endogenous Apaf-1 was cytosolic and did not colocalize with them, even when these pro-survival proteins were overexpressed or after apoptosis was induced. Immunogold electron microscopy confirmed that Apaf-1 was dispersed in the cytoplasm and not on mitochondria or other organelles. After the death stimuli, Bcl-2 and Bcl-x(L) precluded the release of the Apaf-1 cofactor cytochrome c from mitochondria and the formation of larger Apaf-1 complexes, which are steps that presage apoptosis. However, neither Bcl-2 nor Bcl-x(L) could prevent the in vitro activation of Apaf-1 induced by the addition of exogenous cytochrome c. Hence, rather than sequestering Apaf-1 as proposed by the apoptosome model, Bcl-2-like proteins probably regulate Apaf-1 indirectly by controlling upstream events critical for its activation.
- Subjects :
- Animals
Antibodies, Monoclonal immunology
Apoptosis
Apoptotic Protease-Activating Factor 1
Caspases metabolism
Cell Line
Cytochrome c Group pharmacology
Cytoplasm ultrastructure
Enzyme Activation
Fluorescent Antibody Technique
Humans
Microscopy, Confocal
Microscopy, Immunoelectron
Proteins immunology
bcl-X Protein
Cytoplasm metabolism
Proteins metabolism
Proto-Oncogene Proteins c-bcl-2 metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9525
- Volume :
- 149
- Issue :
- 3
- Database :
- MEDLINE
- Journal :
- The Journal of cell biology
- Publication Type :
- Academic Journal
- Accession number :
- 10791976
- Full Text :
- https://doi.org/10.1083/jcb.149.3.623