Tumor necrosis factor α inhibits oxidative phosphorylation through tyrosine phosphorylation at subunit I of cytochrome c oxidase
Tumor necrosis factor α inhibits oxidative phosphorylation through tyrosine phosphorylation at subunit I of cytochrome c oxidase
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DOI：
10.1074/jbc.m801954200
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发表时间：
2008-07-25
影响因子：
4.8
通讯作者：
Huttemann, Maik
中科院分区：
文献类型：
--
作者：
Samavati, Lobelia;Lee, Icksoo;Huttemann, Maik
线粒体氧化磷酸化为细胞提供了大部分能量。作为这一过程的一部分，细胞色素c氧化酶(CcO)将质子泵过线粒体内膜，有助于线粒体膜电位的产生，而线粒体膜电位被ATP合成酶用来产生ATP。在急性炎症期间，就像脓毒症一样，有氧代谢似乎出现故障，并切换到糖酵解能量产生。促炎症细胞因子肿瘤坏死因子-α(TNF-α)已被证明在炎症中起中心作用。我们假设，肿瘤坏死因子α触发的细胞信号以CcO为靶标，CcO是有氧能量代谢的中心酶，可以通过磷酸化来调节。使用牛和小鼠肝细胞总匀浆，肿瘤坏死因子α处理导致CcO活性降低约60%。相反，使用分离的线粒体和纯化的CcO，肿瘤坏死因子α对CcO活性没有直接影响，表明由TNFα触发的细胞内信号级联介导了CcO的抑制。经肿瘤坏死因子α处理后分离的CCO显示CcO催化亚基I上的酪氨酸磷酸化，与在变构激活剂ADP和抑制剂ATP存在下，高浓度细胞色素c分别抑制50%和70%相似。CCO磷酸化发生在酪氨酸304上，如磷酸表位特异性抗体所证明的那样。此外，H2.35细胞线粒体膜电位降低是对肿瘤坏死因子α的反应。同时，在小鼠肝细胞和H2.35细胞中，细胞三磷酸腺苷含量超过35%，%降低。我们推测，在肿瘤坏死因子α介导的病理过程中，例如脓毒症，一个重要的因素是能量缺乏，这与在这些患者中发现的组织氧提取和利用不良是平行的。
Mitochondrial oxidative phosphorylation provides most cellular energy. As part of this process, cytochrome c oxidase (CcO) pumps protons across the inner mitochondrial membrane, contributing to the generation of the mitochondrial membrane potential, which is used by ATP synthase to produce ATP. During acute inflammation, as in sepsis, aerobic metabolism appears to malfunction and switches to glycolytic energy production. The pro-inflammatory cytokine tumor necrosis factor alpha(TNF alpha) has been shown to play a central role in inflammation. We hypothesized that TNF alpha-triggered cell signaling targets CcO, which is a central enzyme of the aerobic energy metabolism and can be regulated through phosphorylation. Using total bovine and murine hepatocyte homogenates TNF alpha treatment led to an similar to 60% reduction in CcO activity. In contrast, there was no direct effect of TNF alpha on CcO activity using isolated mitochondria and purified CcO, indicating that a TNF alpha-triggered intracellular signaling cascade mediates CcO inhibition. CcO isolated after TNF alpha treatment showed tyrosine phosphorylation on CcO catalytic subunit I and was similar to 50 and 70% inhibited at high cytochrome c concentrations in the presence of allosteric activator ADP and inhibitor ATP, respectively. CcO phosphorylation occurs on tyrosine 304 as demonstrated with a phosphoepitope-specific antibody. Furthermore, the mitochondrial membrane potential was decreased in H2.35 cells in response to TNF alpha. Concomitantly, cellular ATP was more than 35 and 64% reduced in murine hepatocytes and H2.35 cells. We postulate that an important contributor in TNF alpha-mediated pathologies, such as sepsis, is energy paucity, which parallels the poor tissue oxygen extraction and utilization found in such patients.