Calphostin C-mediated translocation and integration of Bax into mitochondria induces cytochrome c release before mitochondrial dysfunction |
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Authors: | Ikemoto H Tani E Ozaki I Kitagawa H Arita N |
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Institution: | Molecular Biology Research Laboratory, Department of Neurosurgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan. ike-ns@hyo-med.ac.jp |
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Abstract: | Calphostin C-mediated apoptosis in glioma cells was reported previously to be associated with down-regulation of Bcl-2 and Bcl-xL. In this study, we report that 100 nM calphostin C also induces translocation and integration of monomeric Bax into mitochondrial membrane, followed by cytochrome c release into cytosol and subsequent decrease of mitochondrial inner membrane potential (DeltaPsim) before activation of caspase-3. The integration of monomeric Bax was associated with acquirement of alkali-resistance. The translocated monomeric Bax was partly homodimerized after cytochrome c release and decrease of DeltaPsim. The translocation and homodimerization of Bax, cytochrome c release, and decrease of DeltaPsim were not blocked by 100 microM z-VAD.fmk, a pan-caspase inhibitor, but the homodimerization of Bax and decrease of DeltaPsim were inhibited by 10 microM oligomycin, a mitochondrial F0F1-ATPase inhibitor. Therefore, it would be assumed that mitochondrial release of cytochrome c results from translocation and integration of Bax and is independent of permeability transition of mitochondria and caspase activation, representing a critical step in calphostin C-induced cell death. |
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