Priault Muriel, Bessoule Jean-Jacques, Grelaud-Coq Angela, Camougrand Nadine, Manon Stéphen
UMR5095 C.N.R.S./Université de Bordeaux 2, Bordeaux, France; UMR5544 C.N.R.S./Université de Bordeaux 2, Bordeaux, France.
Eur J Biochem. 2002 Nov;269(22):5440-50. doi: 10.1046/j.1432-1033.2002.03234.x.
The oxidant function of pro-apoptotic protein Bax was investigated through heterologous expression in yeast. Direct measurements of fatty acid content show that Bax-expression induces oxidation of mitochondrial lipids. This effect is prevented by the coexpression of Bcl-xL. The oxidation actually could be followed on isolated mitochondria as respiration-induced peroxidation of polyunsaturated cis-parinaric 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 Bax-induced 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.
通过在酵母中的异源表达研究了促凋亡蛋白Bax的氧化功能。对脂肪酸含量的直接测量表明，Bax的表达会诱导线粒体脂质的氧化。Bcl-xL的共表达可阻止这种效应。实际上，在分离的线粒体上可观察到这种氧化，表现为呼吸诱导的多不饱和顺式-十八碳四烯酸的过氧化，在完整细胞上则表现为硫代巴比妥酸反应产物量的增加。增加脂质不饱和度从而使其对氧化更敏感的处理，会加快Bax诱导的死亡动力学。相反，脂质氧化抑制剂和降低脂肪酸不饱和度的处理会减缓Bax诱导的死亡动力学。综上所述，这些结果表明，Bax诱导的线粒体脂质氧化与Bax诱导的细胞死亡相关。相反，脂质氧化与同时发生的大量Bax诱导的超氧化物和过氧化氢积累关系不大，因为活性氧的化学或酶促清除并不能阻止脂质氧化，也对Bax诱导的细胞死亡动力学没有任何影响。无论线粒体脂质氧化的来源如何，这些数据表明它是导致Bax诱导的细胞死亡的一系列事件中的一个主要步骤。根据脂质氧化在哺乳动物细胞凋亡以及其他生物体中其他形式的细胞死亡中的作用，对这些结果进行了讨论。
