Dissimilar mechanisms of cytochrome c release induced by octyl glucoside-activated BAX and by BAX activated with truncated BID.
In the present study, we compared alkali-resistant BAX insertion into the outer mitochondrial membrane, mitochondrial remodeling, mitochondrial membrane potential changes, and cytochrome c (Cyt c) release from isolated brain mitochondria triggered by recombinant BAX oligomerized with 1% octyl glucoside (BAX(oligo)) and by a combination of monomeric BAX (BAX(mono)) and caspase 8-cleaved C-terminal fragment of recombinant BID (truncated BID, t(c)BID). We also examined whether the effects induced by BAX(oligo) or by BAX(mono) activated with t(c)BID depended on induction of the mitochondrial permeability transition. The results obtained in this study revealed that t(c)BID plus BAX(mono) produced BAX insertion and Cyt c release without overt changes in mitochondrial morphology. On the contrary, treatment of mitochondria with BAX(oligo) resulted in BAX insertion and Cyt c release, which were accompanied by gross distortion of mitochondrial morphology. The effects of BAX(oligo) could be at least partially suppressed by mitochondrial depolarization. The effects of t(c)BID plus BAX(mono) were insensitive to depolarization. BAX(oligo) produced similar BAX insertion, mitochondrial remodeling, and Cyt c release in KCl- and in N-methyl-D-glucamine-based incubation media indicating a non-essential role for K+ influx into mitochondria in these processes. A combination of cyclosporin A and ADP, inhibitors of the mitochondrial permeability transition, attenuated Cyt c release, mitochondrial remodeling, and depolarization induced by BAX(oligo), but failed to influence the effects produced by t(c)BID plus BAX(mono). Thus, our results suggest a significant difference in the mechanisms of the outer mitochondrial membrane permeabilization and Cyt c release induced by detergent-oligomerized BAX(oligo) and by BAX activated with t(c)BID.
Li
Tsyregma
T
Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Brustovetsky
Tatiana
T
Antonsson
Bruno
B
Brustovetsky
Nickolay
N
D000818:Animals; D051023:BH3 Interacting Domain Death Agonist Protein / Q000187:drug effects / Q000378:metabolism; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism*; D005960:Glucosides / Q000494:pharmacology*; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D016254:Mutagenesis, Insertional; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D051023:BH3 Interacting Domain Death Agonist Protein; C494816:Bid protein, rat; D005960:Glucosides; D010446:Peptide Fragments; D011994:Recombinant Proteins; D051028:bcl-2-Associated X Protein; C018619:octyl-beta-D-glucoside; D045304:Cytochromes c; D002118:Calcium