Superoxide activates mitochondrial uncoupling protein 2 from the matrix side - Studies using targeted antioxidants
Superoxide activates mitochondrial uncoupling protein 2 from the matrix side - Studies using targeted antioxidants
复制标题
DOI：
10.1074/jbc.m208262200
复制
发表时间：
2002-12-06
影响因子：
4.8
通讯作者：
Brand, MD
中科院分区：
文献类型：
--
作者：
Echtay, KS;Murphy, MP;Brand, MD
超氧化物通过解偶联蛋白UCP1、UCP2和UCP3激活核苷酸敏感的线粒体质子运输(Echtay，K.S.，等人)。(2002)《自然》415,1482-1486)。提出了两种可能的机制：一种是超氧化物或其产物直接激活UCP质子传输机制，另一种是UCP催化的超氧阴离子输出与氢过氧自由基进入的循环耦合。在这里，我们提供了第一种机制的证据，并表明超氧化物从线粒体内膜的基质侧激活大鼠肾线粒体UCP2：(I)外源超氧化物抑制基质乌头酸酶，表明外部超氧化物进入基质。(Ii)低浓度的线粒体靶向抗氧化剂10(6‘-泛喹诺基)癸基三苯基膦(MitoQ)或2-[2-(triphenylphosphonio)ethyl]-3，4-dihydro-2，5，7，8-tetramethyl-2H-1-benzopyran-6-ol溴化物(MitoVitE)可消除超氧化物诱导的解偶联，这些抗氧化剂是泛醌(Q)或生育酚衍生物，通过共价结合到三苯基膦阳离子上靶向基质。然而，类似浓度的非靶向抗氧化剂Q(O)、Q(1)、去环联苯二酚、维生素E或6-羟基-2，5，7，8-四甲基色满2-羧酸(TROLOX)或线粒体靶向但氧化还原不活跃的类似物十烷基三苯基膦或4-氯丁基三苯基膦对超氧化物诱导的解偶联没有影响。因此，基质超氧化物似乎是外源超氧化物激活UCP2所必需的。(3)抑制细胞色素氧化酶使线粒体积累的MitoQ还原氧化比增加时，可引起核苷酸敏感解偶联，而这种解偶联不受外部超氧化物歧化酶的抑制。在这些条件下，已知对苯二酚会产生超氧化物，由于MitoQ定位于线粒体基质中，这表明基质中超氧化物的产生足以激活UCP2。此外，超氧化物不需要输出，也不需要循环通过内膜来引起解偶联。我们的结论是，超氧化物(或其产物)通过激活线粒体内膜基质侧解偶联蛋白的质子传输机制来发挥其解偶联作用。
Superoxide activates nucleotide-sensitive mitochondrial proton transport through the uncoupling proteins UCP1, UCP2, and UCP3 (Echtay, K. S., et al. (2002) Nature 415, 1482-1486). Two possible mechanisms were proposed: direct activation of the UCP proton transport mechanism by superoxide or its products and a cycle of hydroperoxyl radical entry coupled to UCP-catalyzed superoxide anion export. Here we provide evidence for the first mechanism and show that superoxide activates UCP2 in rat kidney mitochondria from the matrix side of the mitochondrial inner membrane: (i) Exogenous superoxide inhibited matrix aconitase, showing that external superoxide entered the matrix. (ii) Superoxide-induced uncoupling was abolished by low concentrations of the mitochondrially targeted antioxidants 10(6'-ubiquinonyl)decyltriphenylphosphonium (mitoQ) or 2- [2-(triphenylphosphonio)ethyl]-3,4-dihydro-2,5,7,8-tetramethyl-2H-1-benzopyran-6-ol bromide (mitoVit E), which are ubiquinone (Q) or tocopherol derivatives targeted to the matrix by covalent attachment to triphenylphosphonium cation. However, superoxide-induced uncoupling was not affected by similar concentrations of the nontargeted antioxidants Q(o), Q(1), decylubiquinone, vitamin E, or 6-hydroxy-2,5,7,8-tetramethylchroman 2-carboxylic acid (TROLOX) or of the mitochondrially targeted but redox-inactive analogs decyltriphenylphosphonium or 4-chlorobutyltriphenylphosphonium. Thus matrix superoxide appears to be necessary for activation of UCP2 by exogenous superoxide. (iii) When the reduced to oxidized ratio of mitoQ accumulated by mitochondria was increased by inhibiting cytochrome oxidase, it induced nucleotide-sensitive uncoupling that was not inhibited by external superoxide dismutase. Under these conditions quinols are known to produce superoxide, and because mitoQ is localized within the mitochondrial matrix this suggests that production of superoxide in the matrix was sufficient to activate UCP2. Furthermore, the superoxide did not need to be exported or to cycle across the inner membrane to cause uncoupling. We conclude that superoxide (or its products) exerts its uncoupling effect by activating the proton transport mechanism of uncoupling proteins at the matrix side of the mitochondrial inner membrane.