Bax and Bcl-xL 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 molecules such as cytochrome c and AlF, and some caspases, which are all regulated 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) leading to AIF release in the isolated mitochondria. We have previously shown 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 mitochondria triggered by Bas and by chemicals that induce permeability transition (PT), In rat and yeast mitochondria, Bas did not affect the ADP/ATP exchange activity of ANT. VDAC-deficient but not ANT-deficient feast mitochondria showed resistance to cytochrome c release, Delta psi loss, and swelling caused by Bas and PT inducers. Bcl-x(L) showed similar inhibition of all these changes in ANT-deficient and wild type yeast mitochondria, Furthermore, Bas induces cytochrome c release in wild type yeast cells but not VDAC1-deficient yeast cells. These data indicate that VDAC, but not ANT, is essential for apoptotic mitochondrial changes. The data also indicate that Bcl-xL acid Bas possess an ability to regulate mitochondrial membrane permeability independently of other Bcl-2 family members.