Damage-induced Bax N-terminal change, translocation to mitochondria and formation of Bax dimers/complexes occur regardless of cell fate.
Sequential steps in the activation of the pro-apoptotic protein Bax are described for cells with different sensitivity to cytotoxins. SH-EP1 and SH-SY5Y human neuroblastoma cells, derived from a single precursor cell line, differed in their sensitivity to taxol but showed the same sensitivity to cisplatin. Both drugs, in both cell lines, induced exposure of a constitutively occluded N-terminal epitope of Bax. This was reversible and occurred before the translocation of cytosolic Bax to mitochondria. The N-terminal change in Bax, its subsequent movement to mitochondria and its dimerization/complex formation were insufficient for commitment to death, occurring in the same proportion of cells that either maintained (SH-SY5Y) or lost (SH-EP1) clonogenic survival after taxol treatment. Suppression of taxol-induced apoptosis occurred upstream of cytochrome c release from mitochondria in SH-SY5Y cells. The data suggest that a further drug damage-induced event occurs after Bax dimerization/complex formation but prior to cytochrome c release. This event was absent in the taxol-resistant cells.
Makin
G W
GW
Cancer Research Campaign Cellular and Molecular Pharmacology Group, School of Biological Sciences, University of Manchester, Manchester M13 9PT, UK.
Corfe
B M
BM
Griffiths
G J
GJ
Thistlethwaite
A
A
Hickman
J A
JA
Dive
C
C
D000970:Antineoplastic Agents / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D019070:Cell Lineage; D002470:Cell Survival; D002945:Cisplatin / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D000939:Epitopes; D005434:Flow Cytometry; D006801:Humans; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D009447:Neuroblastoma / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000235:genetics*; D019253:Proto-Oncogene Proteins c-bcl-2; D013347:Subcellular Fractions; D013997:Time Factors; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein
D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; C494826:BAX protein, human; D003574:Cytochrome c Group; D000939:Epitopes; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D020169:Caspases; D017239:Paclitaxel; D002945:Cisplatin