Expression of Bcl-x(S) in Xenopus oocytes induces BH3-dependent and caspase-dependent cytochrome c release and apoptosis.
The mechanism of action of pro-apoptotic proteins is difficult to study in vivo because of their death effect, which makes it problematic to obtain sufficient homogeneous experimental material for biochemical analysis. We show here that pro-apoptotic genes expressed in Xenopus oocytes constitute a useful in vivo system for studying their mechanism of action. In the present study, we used this system to study the death effects of Bcl-x(S), a pro-apoptotic member of the Bcl-2 family. The results showed that expression of Bcl-x(S) in oocytes induces oocyte death by a caspase-dependent mechanism, which includes BH3-dependent cytochrome c release and is inhibited by co-expression of the anti-apoptotic proteins Bcl-2 and Bcl-x(L). The release of cytochrome c was found to be dependent on caspase activity. Bcl-x(S) was localized mainly in the mitochondria, and Bcl-x(S) transmembrane and BH3 domains were required for its apoptotic effect. These findings suggest that Bcl-x(S) induces apoptosis in Xenopus oocytes mainly by its presence in the mitochondria, where it induces BH3- and caspase-dependent release of cytochrome c, which leads to oocyte death.
Braun
Tali
T
Department of Neurobiochemistry, George S. Wise Faculty of Life Sciences, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
Dar
Shachar
S
Vorobiov
Dmitry
D
Lindenboim
Liora
L
Dascal
Nathan
N
Stein
Reuven
R
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism*; D004789:Enzyme Activation / Q000502:physiology; D005260:Female; D015870:Gene Expression / Q000502:physiology; D009842:Oligopeptides / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000235:genetics*; D029867:Xenopus Proteins; D014982:Xenopus laevis; D051020:bcl-X Protein
C494809:BCL2L1 protein, Xenopus; C474007:Bax protein (53-86); D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D003574:Cytochrome c Group; D009842:Oligopeptides; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D029867:Xenopus Proteins; D051020:bcl-X Protein; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; D020169:Caspases