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Changes in intramitochondrial and cytosolic pH: early events that modulate caspase activation during apoptosis.

机译:线粒体内和细胞质pH值的变化:凋亡过程中调节caspase激活的早期事件。

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Mitochondria trigger apoptosis by releasing caspase activators, including cytochrome c (cytC). Here we show, using a pH-sensitive green fluorescent protein (GFP), that mitochondria-dependent apoptotic stimuli (such as Bax, staurosporine and ultraviolet irradiation) induce rapid, Bcl-2-inhibitable mitochondrial alkalinization and cytosol acidification, followed by cytC release, caspase activation and mitochondrial swelling and depolarization. These events are not induced by mitochondria-independent apoptotic stimuli, such as Fas. Activation of cytosolic caspases by cytC in vitro is minimal at neutral pH, but maximal at acidic pH, indicating that mitochondria-induced acidification of the cytosol may be important for caspase activation; this finding is supported by results obtained from cells using protonophores. Cytosol acidification and cytC release are suppressed by oligomycin, a FoF1-ATPase/H +-pump inhibitor, but not by caspase inhibitors. Ectopic expression of Bax in wild-type, but not FoF1/H+-pump-deficient, yeast cells similarly results in mitochondrial matrix alkalinization, cytosol acidification and cell death. These findings indicate that mitochondria-mediated alteration of intracellular pH may be an early event that regulates caspase activation in the mitochondrial pathway for apoptosis.
机译:线粒体通过释放caspase激活剂(包括细胞色素c(cytC))来触发凋亡。在这里,我们显示了使用pH敏感的绿色荧光蛋白(GFP),线粒体依赖性凋亡刺激物(例如Bax,星形孢菌素和紫外线照射)诱导快速,Bcl-2抑制的线粒体碱化和细胞溶质酸化,然后cytC释放,胱天蛋白酶激活和线粒体肿胀和去极化。这些事件不是由独立于线粒体的凋亡刺激物如Fas诱导的。 cytC在体外在中性pH下对胞质胱天冬氨酸蛋白酶的激活作用最小,而在酸性pH下最大。这一发现得到了使用质子体从细胞中获得的结果的支持。寡霉素(一种FoF1-ATPase / H +泵抑制剂)可抑制细胞液酸化和cytC释放,而胱天蛋白酶抑制剂则不能。 Bax在野生型而非FoF1 / H +泵缺陷型酵母细胞中的异位表达类似地导致线粒体基质碱化,胞质溶胶酸化和细胞死亡。这些发现表明,线粒体介导的细胞内pH改变可能是调节细胞凋亡的线粒体途径中胱天蛋白酶激活的早期事件。

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