Oxidative Bax dimerization promotes its translocation to mitochondria independently of apoptosis

ABSTRACTBax is a cytosolic protein, which in response to stressing apoptotic stimuli, is activated and translocates to mitochondria, thus initiating the intrinsic apoptotic pathway. In spite of many studies and the importance of the issue, the molecular mechanisms that trigger Bax translocation are...

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Published in:The FASEB journal 2005-09, Vol.19 (11), p.1504-1506
Main Authors: D'Alessio, M, De Nicola, M, Coppola, S, Gualandi, G, Pugliese, L, Cerella, C, Cristofanon, S, Civitareale, P, Ciriolo, M. R, Bergamaschi, A, Magrini, A, Ghibelli, L
Format: Article
Language:English
Subjects:
Apoptosis
bcl-2-Associated X Protein - chemistry
bcl-2-Associated X Protein - metabolism
Caspase 8
Caspases - physiology
Cells, Cultured
Dimerization
disulfide
Disulfides - chemistry
Endoplasmic Reticulum - physiology
glutathione
Glutathione - metabolism
Humans
Hydrogen Peroxide - pharmacology
Hydrogen-Ion Concentration
Mitochondria - metabolism
Models, Molecular
Oxidation-Reduction
oxidative stress
Protein Transport
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Summary:ABSTRACTBax is a cytosolic protein, which in response to stressing apoptotic stimuli, is activated and translocates to mitochondria, thus initiating the intrinsic apoptotic pathway. In spite of many studies and the importance of the issue, the molecular mechanisms that trigger Bax translocation are still obscure. We show by computer simulation that the two cysteine residues of Bax may form disulfide bridges, producing conformational changes that favor Bax translocation. Oxidative, nonapoptogenic treatments produce an up‐shift of Bax migration compatible with homodimerization, which is reverted by reducing agents; this is accompanied by translocation to mitochondria. Dimers also appear in pure cytosolic fractions of cell lysates treated with H2O2, showing that Bax dimerization may take place in the cytosol. Bax dimer‐enriched lysates support Bax translocation to isolated mitochondria much more efficiently than untreated lysates, indicating that dimerization may promote Bax translocation. The absence of apoptosis in our system allows the demonstration that Bax moves because of oxidations, even in the absence of apoptosis. This provides the first evidence that Bax dimerization and translocation respond to oxidative stimuli, suggesting a novel role for Bax as a sensor of redox imbalance.
ISSN:0892-6638
1530-6860
DOI:10.1096/fj.04-3329fje