Knieß Robert A, Mayer Matthias P
Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH-Alliance, Heidelberg, Germany.
NPJ Aging Mech Dis. 2016 Dec 15;2:16028. doi: 10.1038/npjamd.2016.28. eCollection 2016.
What is cause and what is consequence of aging and whether reactive oxygen species (ROS) contribute to this phenomenon is debated since more than 50 years. Notwithstanding, little is known about the cellular buffer and redox systems in aging , which is a model for aging stem cells. Using genetically encoded fluorescent sensors, we measured pH, HO levels and the glutathione redox potential compartment-specific in the cytosol of living, replicatively aging yeast cells, growing under fermenting and respiratory conditions until the end of their lifespan. We found that the pH decreases under both conditions at later stages of the replicative lifespan. HO levels increase in fermenting cells in the post-replicative stage, but increase continuously with age in respiring cells. The glutathione redox couple becomes also more oxidizing in respiring cells but surprisingly more reducing under fermenting conditions. In strains deleted for the gene encoding glutathione reductase Glr1, such a reduction of the glutathione redox couple with age is not observed. We demonstrate that Glr1 is activated at lower pH explaining the reduced glutathione potential. The deletion of dramatically increases the glutathione redox potential especially under respiratory conditions but does not reduce lifespan. Our data demonstrate that pH and the glutathione redox couple is linked through Glr1 and that yeast cells can cope with a high glutathione redox potential without impact on longevity. Our data further suggest that a breakdown of cellular energy metabolism marks the end of replicative lifespan in yeast.
衰老的原因和后果是什么，活性氧（ROS）是否促成了这一现象，五十多年来一直存在争议。尽管如此，关于衰老过程中的细胞缓冲和氧化还原系统，我们所知甚少，衰老过程是衰老干细胞的一个模型。我们使用基因编码的荧光传感器，测量了在发酵和呼吸条件下生长直至寿命结束的、处于复制性衰老状态的活酵母细胞胞质溶胶中特定区域的pH值、HO水平和谷胱甘肽氧化还原电位。我们发现，在复制寿命的后期，两种条件下pH值都会下降。在发酵细胞的复制后阶段，HO水平会升高，但在呼吸细胞中会随着年龄的增长持续升高。在呼吸细胞中，谷胱甘肽氧化还原对也会变得更具氧化性，但令人惊讶的是，在发酵条件下它会变得更具还原性。在缺失编码谷胱甘肽还原酶Glr1的基因的菌株中，未观察到谷胱甘肽氧化还原对随年龄增长而降低的情况。我们证明，Glr1在较低的pH值下被激活，这解释了谷胱甘肽电位的降低。缺失 会显著增加谷胱甘肽氧化还原电位，尤其是在呼吸条件下，但不会缩短寿命。我们的数据表明，pH值和谷胱甘肽氧化还原对通过Glr1联系在一起，酵母细胞可以应对高谷胱甘肽氧化还原电位而不影响寿命。我们的数据进一步表明，细胞能量代谢的崩溃标志着酵母复制寿命的结束。
