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J. Cell Biol.,
Volume 140, Number 6, March 23, 1998 1485-1495
§
* Department of Medicine, Caspase-3-mediated proteolysis is a critical
element of the apoptotic process. Recent studies have
demonstrated a central role for mitochondrial proteins
(e.g., Bcl-2 and cytochrome c) in the activation of
caspase-3, by a process that involves interaction of several protein molecules. Using antibodies that specifically recognize the precursor form of caspase-3, we
demonstrate that the caspase-3 proenzyme has a mitochondrial and cytosolic distribution in nonapoptotic
cells. The mitochondrial caspase-3 precursor is contained in the intermembrane space. Delivery of a variety of apoptotic stimuli is accompanied by loss of mitochondrial caspase-3 precursor staining and appearance
of caspase-3 proteolytic activity. We propose that the
mitochondrial subpopulation of caspase-3 precursor molecules is coupled to a distinct subset of apoptotic
signaling pathways that are Bcl-2 sensitive and that are
transduced through multiple mitochondrion-specific
protein interactions.
Department of Dermatology, § Department of Cell Biology and Anatomy,
Department of
Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; ¶ Department of Biochemistry and
Molecular Biology, Merck Frosst Center for Therapeutic Research, Pointe Claire-Dorval, Quebec, H9R 4P8, Canada; and ** Department of Biochemistry, Merck Research Laboratories, Rahway, New Jersey 07065
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