Koeck Thomas, Fu Xiaoming, Hazen Stanley L, Crabb John W, Stuehr Dennis J, Aulak Kulwant S
Department of Immunology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
J Biol Chem. 2004 Jun 25;279(26):27257-62. doi: 10.1074/jbc.M401586200. Epub 2004 Apr 14.
Growing evidence connects a cumulative formation of 3-nitrotyrosyl adducts in proteins as a marker for oxidative damage with the pathogenesis of various diseases and pathological conditions associated with oxidative stress. A physiological signaling role for protein nitration has also been suggested. Controlled "denitration" would be essential for such a contribution of protein nitration to cellular regulatory processes. Thus, we further characterized such a potentially controlled, reversible tyrosine nitration that occurs in respiring mitochondria during oxygen deprivation followed by reoxygenation, which we recently discovered. Mitochondria constitute cellular centers of protein nitration and are leading candidates for a "nitrative" regulation. Mitochondria are capable of completely eliminating 3-nitrotyrosyl adducts during 20 min of hypoxia-anoxia and undergoing a selective partial reduction after only 5 min. This denitration is independent of protein degradation but depends on the oxygen tension. Reoxygenation re-establishes protein tyrosine nitration patterns that are almost identical to the pattern that occurs before hypoxia-anoxia, with nitration levels that depend on the duration of hypoxia-anoxia. The identified mitochondrial targets of this process are critical for energy and antioxidant homeostasis and, therefore, cell and tissue viability. This cycle of protein nitration and denitration shows analogies to protein phosphorylation, and we demonstrate that the cycle meets most of the criteria for a cellular signaling mechanism. Taken together, our data reveal that protein tyrosine nitration in mitochondria can be controlled, is target-selective and rapid, and is dynamic enough to serve as a nitrative regulatory signaling process that likely affects cellular energy, redox homeostasis, and pathological conditions when these features become disturbed.
越来越多的证据表明，蛋白质中3-硝基酪氨酸加合物的累积形成作为氧化损伤的标志物，与各种与氧化应激相关的疾病和病理状况的发病机制有关。也有人提出蛋白质硝化具有生理信号传导作用。对于蛋白质硝化对细胞调节过程的这种作用而言，可控的“脱硝化”至关重要。因此，我们进一步表征了这样一种潜在可控的、可逆的酪氨酸硝化作用，它发生在缺氧后再给氧的呼吸线粒体中，这是我们最近发现的。线粒体是蛋白质硝化的细胞中心，是“硝化”调节的主要候选者。线粒体能够在缺氧-无氧20分钟内完全消除3-硝基酪氨酸加合物，并且仅在5分钟后就会发生选择性部分还原。这种脱硝化作用与蛋白质降解无关，但取决于氧张力。再给氧可重新建立与缺氧-无氧前几乎相同的蛋白质酪氨酸硝化模式，硝化水平取决于缺氧-无氧的持续时间。该过程中确定的线粒体靶点对于能量和抗氧化稳态至关重要，因此对细胞和组织的活力也至关重要。这种蛋白质硝化和脱硝化循环类似于蛋白质磷酸化，并且我们证明该循环符合细胞信号传导机制的大多数标准。综上所述，我们的数据表明线粒体中的蛋白质酪氨酸硝化作用是可控的，可以靶向选择且快速，并且具有足够的动态性，能够作为一种硝化调节信号传导过程，当这些特征受到干扰时，可能会影响细胞能量、氧化还原稳态和病理状况。
