Loss of NAD(H) from swollen yeast mitochondria.
Loss of NAD(H) from swollen yeast mitochondria.
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酵母肿胀的NAD（H）损失。
DOI：
10.1186/1471-2091-7-3
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发表时间：
2006-01-24
期刊：
影响因子：
--
通讯作者：
Pfeiffer, Douglas R
中科院分区：
文献类型：
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作者：
Bradshaw, Patrick C;Pfeiffer, Douglas R
作为氧化磷酸化过程的一部分，线粒体电子传递链氧化基质空间NADH。线粒体含有穿梭体，用于将细胞质NADH还原当量转运到线粒体基质中。因此，很长一段时间以来，人们认为NAD(H)本身并没有被运输到线粒体中。然而，已经获得了NAD(H)进出植物和哺乳动物线粒体的证据。由于酿酒酵母线粒体可以直接氧化细胞质NADH，因此线粒体NAD(H)运输是否发生在该生物体中仍然值得怀疑。肿胀的酵母线粒体基质空间中NAD(H)的丢失比正常的、浓缩的酵母线粒体中NAD(H)的丢失更多。当乙醇或其他基质空间NAD连接底物被氧化时，肿胀细胞器中NAD(H)的损失导致呼吸速率大大降低。将NAD重新添加到培养基中，即使存在不含膜的NADH脱氢酶抑制剂，肿胀的线粒体氧化乙醇的呼吸速率也会恢复，这表明NAD被转运到基质空间。添加NAD不能恢复氧化苹果酸、谷氨酸和丙酮酸组合的肿胀线粒体的呼吸速率下降。因此，基质空间代谢物的损失并不完全是NAD(H)所特有的。然而，在NAD(H)丢失期间，大多数其他核苷酸的线粒体水平保持不变。在甘露醇培养基中，酵母线粒体非特异性通道（YMUC）的打开导致低渗肿胀或胶体渗透性肿胀导致nad相关呼吸减少。然而，NAD(H)从基质空间的损失并不是由YMUC介导的，因为YMUC抑制剂并不能阻止肿胀期间NAD相关呼吸的减少，并且YMUC打开而不肿胀也不会导致NAD相关呼吸的减少。分离酵母线粒体内源性NAD(H)的损失受到基质空间扩张的极大刺激。NAD(H)的损失极大地限制了肿胀线粒体中与nadd相关的呼吸，而不会降低正常浓缩细胞器中与nadd相关的呼吸速率。添加NAD可以完全恢复肿胀线粒体的呼吸减少。在活酵母细胞中，线粒体肿胀在线粒体降解和细胞死亡之前已被观察到。因此，线粒体肿胀可能刺激NAD(H)转运，以调节这些条件下的代谢。
The mitochondrial electron transport chain oxidizes matrix space NADH as part of the process of oxidative phosphorylation. Mitochondria contain shuttles for the transport of cytoplasmic NADH reducing equivalents into the mitochondrial matrix. Therefore for a long time it was believed that NAD(H) itself was not transported into mitochondria. However evidence has been obtained for the transport of NAD(H) into and out of plant and mammalian mitochondria. Since Saccharomyces cerevisiae mitochondria can directly oxidize cytoplasmic NADH, it remained questionable if mitochondrial NAD(H) transport occurs in this organism. NAD(H) was lost more extensively from the matrix space of swollen than normal, condensed isolated yeast mitochondria from Saccharomyces cerevisiae. The loss of NAD(H) in swollen organelles caused a greatly decreased respiratory rate when ethanol or other matrix space NAD-linked substrates were oxidized. Adding NAD back to the medium, even in the presence of a membrane-impermeant NADH dehydrogenase inhibitor, restored the respiratory rate of swollen mitochondria oxidizing ethanol, suggesting that NAD is transported into the matrix space. NAD addition did not restore the decreased respiratory rate of swollen mitochondria oxidizing the combination of malate, glutamate, and pyruvate. Therefore the loss of matrix space metabolites is not entirely specific for NAD(H). However, during NAD(H) loss the mitochondrial levels of most other nucleotides were maintained. Either hypotonic swelling or colloid-osmotic swelling due to opening of the yeast mitochondrial unspecific channel (YMUC) in a mannitol medium resulted in decreased NAD-linked respiration. However, the loss of NAD(H) from the matrix space was not mediated by the YMUC, because YMUC inhibitors did not prevent decreased NAD-linked respiration during swelling and YMUC opening without swelling did not cause decreased NAD-linked respiration. Loss of endogenous NAD(H) from isolated yeast mitochondria is greatly stimulated by matrix space expansion. NAD(H) loss greatly limits NAD-linked respiration in swollen mitochondria without decreasing the NAD-linked respiratory rate in normal, condensed organelles. NAD addition can totally restore the decreased respiration in swollen mitochondria. In live yeast cells mitochondrial swelling has been observed prior to mitochondrial degradation and cell death. Therefore mitochondrial swelling may stimulate NAD(H) transport to regulate metabolism during these conditions.