Zinc-dependent multi-conductance channel activity in mitochondria isolated from ischemic brain
Zinc-dependent multi-conductance channel activity in mitochondria isolated from ischemic brain
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DOI：
10.1523/jneurosci.5444-05.2006
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发表时间：
2006-06-21
影响因子：
5.3
通讯作者：
Jonas, Elizabeth A.
中科院分区：
文献类型：
--
作者：
Bonanni, Laura;Chachar, Mushtaque;Jonas, Elizabeth A.
短暂性全脑缺血是一种神经元损伤，可诱导迟发性细胞死亡。缺血后早期的标志性事件是线粒体膜的渗透性增强。线粒体功能被破坏的确切机制尚不清楚。在这里，我们表明，全球缺血促进线粒体膜接触点的改变，线粒体内Zn 2+的上升，并激活大，多电导通道的线粒体外膜损伤后1小时。线粒体通道活性与BCL-xL的增强的蛋白酶活性和蛋白水解切割相关，以产生其促死亡对应物Delta N-BCL-xL。这些发现暗示Delta N-BCL-xL参与了大型多电导通道活动。与此一致，通过引入重组Δ N-BCL-xL来模拟大通道活性以控制线粒体，并通过经由贴片移液管将功能性BCL-xL抗体引入缺血后线粒体来阻断大通道活性。通道活性也被烟酰胺腺嘌呤二核苷酸抑制，表明线粒体外膜的电压依赖性阴离子通道（VDAC）的作用。在缺血或在体外应用的膜渗透的Zn 2+螯合剂四-（2-吡啶基甲基）乙二胺衰减通道活性之前，在体内给药的膜不渗透的Zn 2+螯合剂CaEDTA，这表明需要Zn 2+。这些发现揭示了一种新的机制，通过这种机制，缺血性损伤破坏了线粒体外膜的功能完整性，并将Delta N-BCLxL和VDAC牵连到缺血后海马线粒体中观察到的大的Zn 2+依赖性线粒体通道中。
Transient global ischemia is a neuronal insult that induces delayed cell death. A hallmark event in the early post-ischemic period is enhanced permeability of mitochondrial membranes. The precise mechanisms by which mitochondrial function is disrupted are, as yet, unclear. Here we show that global ischemia promotes alterations in mitochondrial membrane contact points, a rise in intramitochondrial Zn2+, and activation of large, multi-conductance channels in mitochondrial outer membranes by 1 h after insult. Mitochondrial channel activity was associated with enhanced protease activity and proteolytic cleavage of BCL-xL to generate its pro-death counterpart, Delta N-BCL-xL. The findings implicate Delta N-BCL-xL in large, multi-conductance channel activity. Consistent with this, large channel activity was mimicked by introduction of recombinant Delta N-BCL-xL to control mitochondria and blocked by introduction of a functional BCL-xL antibody to post-ischemic mitochondria via the patch pipette. Channel activity was also inhibited by nicotinamide adenine dinucleotide, indicative of a role for the voltage-dependent anion channel (VDAC) of the outer mitochondrial membrane. In vivo administration of the membrane-impermeant Zn2+ chelator CaEDTA before ischemia or in vitro application of the membrane-permeant Zn2+ chelator tetrakis-(2-pyridylmethyl) ethylenediamine attenuated channel activity, suggesting a requirement for Zn2+. These findings reveal a novel mechanism by which ischemic insults disrupt the functional integrity of the outer mitochondrial membrane and implicate Delta N-BCLxL and VDAC in the large, Zn2+-dependent mitochondrial channels observed in post-ischemic hippocampal mitochondria.