Bax and Bcl-x(L) independently regulate apoptotic changes of yeast mitochondria that require VDAC but not adenine nucleotide translocator

Mitochondria play an essential role in apoptosis by releasing apoptogenic m olecules such as cytochrome c and AlF, and some caspases, which are all reg ulated by Bcl-2 family proteins. Pro-apoptotic Pas and Bah have been shown to induce cytochrome c release and loss of membrane potential (Delta psi) l eading to AIF release in the isolated mitochondria. We have previously show n that Bas and Bah open the voltage-dependent anion channel (VDAC) allowing cytochrome c to pass through the channel, and Bcl-x(L) closes the channel. However, it has been reported that it is adenine nucleotide translocator ( ANT) with which Bax/Bcl-x(L) interacts that modulate the channel activity. Here, we investigated the role of ANT and VDAC in the changes of isolated m itochondria triggered by Bas and by chemicals that induce permeability tran sition (PT), In rat and yeast mitochondria, Bas did not affect the ADP/ATP exchange activity of ANT. VDAC-deficient but not ANT-deficient feast mitoch ondria showed resistance to cytochrome c release, Delta psi loss, and swell ing caused by Bas and PT inducers. Bcl-x(L) showed similar inhibition of al l these changes in ANT-deficient and wild type yeast mitochondria, Furtherm ore, Bas induces cytochrome c release in wild type yeast cells but not VDAC 1-deficient yeast cells. These data indicate that VDAC, but not ANT, is ess ential for apoptotic mitochondrial changes. The data also indicate that Bcl -xL acid Bas possess an ability to regulate mitochondrial membrane permeabi lity independently of other Bcl-2 family members.