Bax‐induced cell death in yeast depends on mitochondrial lipid oxidation

Abstract

The oxidant function of pro-apoptotic protein Bax was investigated through heterologous expression in yeast. Direct measurements of fatty acid content show that Baxexpression induces oxidation of mitochondrial lipids. This effect is prevented by the coexpression of Bcl-x L . The oxidation actually could be followed on isolated mitochondria as respiration-induced peroxidation of polyunsaturated cisparinaric acid and on whole cells as the increase in the amount of thiobarbituric acid-reactive products. Treatments that increase the unsaturation ratio of lipids, making them more sensitive to oxidation, increase kinetics of Bax-induced death. Conversely, inhibitors of lipid oxidation and treatments that decrease the unsaturation ratio of fatty acids decrease kinetics of Bax-induced death. Taken together, these results show that Bax-induced mitochondrial lipid oxidation is relevant to Bax-induced cell death. Conversely, lipid oxidation is poorly related to the massive Bax-induced superoxide and hydrogen peroxide accumulation, which occurs at the same time, as chemical or enzymatic scavenging of ROS does not prevent lipid oxidation nor has any effects on kinetics of Bax-induced cell death. Whatever the origin of mitochondrial lipid oxidation, these data show that it represents a major step in the cascade of events leading to Baxinduced cell death. These results are discussed in the light of the role of lipid oxidation both in mammalian apoptosis and in other forms of cell death in other organisms.

Role of cardiolipin on tBid and tBid/Bax synergistic effects on yeast mitochondria

“…29 It has also been shown that Bax expression, even at low-expression levels, induced the oxidation of mitochondrial lipid, including CL, an effect which is prevented by hydrophobic antioxidants, such as a-tocopherol and resveratrol. 37 It is important to notice that yeast expression of tBid alone has no effects on the whole yeast cell respiration (data not shown) nor on cell growth. 34 However, in the presence of Bax-c-myc, the expression of tBid increased the kinetics of Bax-c-myc-induced cell death, 34 showing that tBid is able to amplify the killing function of an active form of Bax.…”

Interplay between bax, reactive oxygen species production, and cardiolipin oxidation during apoptosis

“…The specific molecular mechanisms through which Bax may be involved in regulation of cardiolipin peroxidation have not been established yet, although previous studies have elucidated that Bax acts upstream of accumulation of ROS [3,4,26] that required for lipid peroxidation. Recently, we reported that mitochondria targeted electron scavengers -hemigramicidin S conjugated nitroxides -prevented both superoxide accumulation and CL peroxidation and apoptosis initiated by ActD or irradiation without affecting Bax translocation [27,28].…”

“…It has been reported that Bax acts upstream of increased reactive oxygen species (ROS) production in nerve growth factor-deprived neurons and that Bax induced ROS burst is both necessary and sufficient for cyt c redistribution in these cells [3]. Priault et al [4] suggested that Bax induced cell death is related to generation of ROS and membrane lipid peroxidation.…”

“…While the link between Bax/Bak activation and CL oxidation in the regulation of cyt c release during apoptosis remains unspecified [4,6,12], two processes -generation of ROS and activation of cyt c into a CL-specific peroxidase [11] -are essential requisites for the oxidation of CL. Here, we report that Bax/Bak controls CL oxidation by affecting both of these processes.…”

Manganese superoxide dismutase gene dosage affects chromosomal instability and tumor onset in a mouse model of T cell lymphoma

“…Other studies link pro-apoptotic Bax to increased oxidative stress. In one study, Bax expression increased mitochondrial lipid oxidation and this event was necessary for Bax-induced cell death [13]. In studies of sympathetic neurons, Bax expression was required for ROS generation after nerve growth factor (NGF) withdrawal and the ROS production was upstream of the cell death commitment point [14].…”