Calphostin C-mediated translocation and integration of Bax into mitochondria induces cytochrome c release before mitochondrial dysfunction.
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.
Ikemoto
H
H
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
Tani
E
E
Ozaki
I
I
Kitagawa
H
H
Arita
N
N
D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism*; D019281:Dimerization; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D009281:Naphthalenes / Q000378:metabolism* / Q000494:pharmacology; D009840:Oligomycins; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D009840:Oligomycins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D011493:Protein Kinase C; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C058819:calphostin C