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Robin A J Smith,
Victoria J Adlam,
Frances H Blaikie,
Abdul-Rahman B Manas,
Carolyn M Porteous,
Andrew M James,
Meredith F Ross,
Angela Logan,
Helena M Cochemé,
Jan Trnka,
Tracy A Prime,
Irina Abakumova,
Bruce A Jones, Aleksandra Filipovska,
Michael P Murphy
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ABSTRACT: Mitochondrial oxidative damage is thought to contribute to a wide range of human diseases; therefore, the development of approaches to decrease this damage may have therapeutic potential. Mitochondria-targeted antioxidants that selectively block mitochondrial oxidative damage and prevent some types of cell death have been developed. These compounds contain antioxidant moieties, such as ubiquinone, tocopherol, or nitroxide, that are targeted to mitochondria by covalent attachment to a lipophilic triphenylphosphonium cation. Because of the large mitochondrial membrane potential, the cations are accumulated within the mitochondria inside cells. There, the conjugated antioxidant moiety protects mitochondria from oxidative damage. Here, we outline some of the work done to date on these compounds and how they may be developed as therapies.
Annals of the New York Academy of Sciences 01/2009; 1147:105-11. · 3.15 Impact Factor
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ABSTRACT: Complex I has reactive thiols on its surface that interact with the mitochondrial glutathione pool and are implicated in oxidative
damage in many pathologies. However, the Cys residues and the thiol modifications involved are not known. Here we investigate
complex I thiol modification within oxidatively stressed mammalian mitochondria, containing physiological levels of glutathione
and glutaredoxin 2. In mitochondria incubated with the thiol oxidant diamide, complex I is only glutathionylated on the 75-kDa
subunit. Of the 17 Cys residues on the 75-kDa subunit, 6 are not involved in iron-sulfur centers, making them plausible candidates
for glutathionylation. Mass spectrometry of complex I from oxidatively stressed bovine heart mitochondria showed that only
Cys-531 and Cys-704 were glutathionylated. The other four non-iron-sulfur center Cys residues remained as free thiols. Complex
I glutathionylation also occurred in response to relatively mild oxidative stress caused by increased superoxide production
from the respiratory chain. Although complex I glutathionylation within oxidatively stressed mitochondria correlated with
loss of activity, it did not increase superoxide formation, and reversal of glutathionylation did not restore complex I activity.
Comparison with the known structure of the 75-kDa ortholog Nqo3 from Thermus thermophilus complex I suggested that Cys-531 and Cys-704 are on the surface of mammalian complex I, exposed to the mitochondrial glutathione
pool. These findings suggest that Cys-531 and Cys-704 may be important in preventing oxidative damage to complex I by reacting
with free radicals and other damaging species, with subsequent glutathionylation recycling the thiyl radicals and sulfenic
acids formed on the Cys residues back to free thiols.
Journal of Biological Chemistry 09/2008; 283(36):24801-24815. · 4.77 Impact Factor
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ABSTRACT: Complex I has reactive thiols on its surface that interact with the mitochondrial glutathione pool and are implicated in oxidative damage in many pathologies. However, the Cys residues and the thiol modifications involved are not known. Here we investigate complex I thiol modification within oxidatively stressed mammalian mitochondria, containing physiological levels of glutathione and glutaredoxin 2. In mitochondria incubated with the thiol oxidant diamide, complex I is only glutathionylated on the 75-kDa subunit. Of the 17 Cys residues on the 75-kDa subunit, 6 are not involved in iron-sulfur centers, making them plausible candidates for glutathionylation. Mass spectrometry of complex I from oxidatively stressed bovine heart mitochondria showed that only Cys-531 and Cys-704 were glutathionylated. The other four non-iron-sulfur center Cys residues remained as free thiols. Complex I glutathionylation also occurred in response to relatively mild oxidative stress caused by increased superoxide production from the respiratory chain. Although complex I glutathionylation within oxidatively stressed mitochondria correlated with loss of activity, it did not increase superoxide formation, and reversal of glutathionylation did not restore complex I activity. Comparison with the known structure of the 75-kDa ortholog Nqo3 from Thermus thermophilus complex I suggested that Cys-531 and Cys-704 are on the surface of mammalian complex I, exposed to the mitochondrial glutathione pool. These findings suggest that Cys-531 and Cys-704 may be important in preventing oxidative damage to complex I by reacting with free radicals and other damaging species, with subsequent glutathionylation recycling the thiyl radicals and sulfenic acids formed on the Cys residues back to free thiols.
Journal of Biological Chemistry 08/2008; 283(36):24801-15. · 4.77 Impact Factor
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ABSTRACT: Many proteins contain free thiols that can be modified by the reversible formation of mixed disulfides with glutathione. Protein glutathionylation is of significance for defense against oxidative damage and in redox signaling. Here we outline the mechanisms and possible significance of protein glutathionylation.
Current protocols in toxicology 06/2006; Chapter 6:Unit6.10.
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ABSTRACT: Proteins contain free, exposed thiols that can be glutathionylated in the native state as a result of thiol-disulfide exchange reactions with glutathione disulfide, catalyzed by glutaredoxin. A number of other reactions can also lead to protein glutathionylation. The modification of proteins by glutathionylation is important in oxidative damage and may be an important post-translational modification to proteins involved in redox signaling. This unit describes methods for the identification of glutathionylated proteins and quantification of the extent of glutathionylation. The protocols described use isolated mitochondrial protein complexes, mitochondrial membranes, and intact mitochondria, but can be easily adapted to other systems.
Current protocols in toxicology 06/2006; Chapter 6:Unit6.11.
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ABSTRACT: Mitochondrial production of peroxides is a critical event in both pathology and redox signaling. Consequently their selective degradation within mitochondria is of considerable interest. Here we have explored the interaction of the peroxidase mimetic ebselen with mitochondria. We were particularly interested in whether ebselen was activated by mitochondrial glutathione (GSH) and thioredoxin, in determining whether an ebselen moiety could be targeted to mitochondria by conjugating it to a lipophilic cation, and in exploring the nature of ebselen binding to mitochondrial proteins. To achieve these goals we synthesized 2-[4-(4-triphenylphosphoniobutoxy) phenyl]-1,2-benzisoselenazol)-3(2H)-one iodide (MitoPeroxidase), which contains an ebselen moiety covalently linked to a triphenylphosphonium (TPP) cation. The fixed positive charge of TPP facilitated mass spectrometric analysis, which showed that the ebselen moiety was reduced by GSH to the selenol form and that subsequent reaction with a peroxide reformed the ebselen moiety. MitoPeroxidase and ebselen were effective antioxidants that degraded phospholipid hydroperoxides, prevented lipid peroxidation, and protected mitochondria from oxidative damage. Both peroxidase mimetics required activation by mitochondrial GSH or thioredoxin to be effective antioxidants. Surprisingly, conjugation to the TPP cation led to only a slight increase in the uptake of ebselen by mitochondria due to covalent binding of the ebselen moiety to proteins. Using antiserum against the TPP moiety we visualized those proteins covalently attached to the ebselen moiety. This analysis indicated that much of the ebselen present within mitochondria is bound to protein thiols through reversible selenenylsulfide bonds. Both MitoPeroxidase and ebselen decreased apoptosis induced by oxidative stress, suggesting that they can decrease mitochondrial oxidative stress. This exploration has led to new insights into the behavior of peroxidase mimetics within mitochondria and to their use in investigating mitochondrial oxidative damage.
Journal of Biological Chemistry 07/2005; 280(25):24113-26. · 4.77 Impact Factor
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ABSTRACT: CPPs (cell-penetrating peptides) facilitate the cellular uptake of covalently attached oligonucleotides, proteins and other macromolecules, but the mechanism of their uptake is disputed. Two models are proposed: direct movement through the phospholipid bilayer and endocytic uptake. Mitochondria are a good model system to distinguish between these possibilities, since they have no vesicular transport systems. Furthermore, CPP-mediated delivery of macromolecules to the mitochondrial matrix would be a significant breakthrough in the study of mitochondrial function and dysfunction, and could also lead to new therapies for diseases caused by mitochondrial damage. Therefore we investigated whether two CPPs, penetratin and Tat, could act as mitochondrial delivery vectors. We also determined whether conjugation of the lipophilic cation TPP (triphenylphosphonium) to penetratin or Tat facilitated their uptake into mitochondria, since TPP leads to uptake of attached molecules into mitochondria driven by the membrane potential. Neither penetratin nor Tat, nor their TPP conjugates, are internalized by isolated mitochondria, indicating that these CPPs cannot cross mitochondrial phospholipid bilayers. Tat and TPP-Tat are taken up by cells, but they accumulate in endosomes and do not reach mitochondria. We conclude that CPPs cannot cross mitochondrial phospholipid bilayers, and therefore cannot deliver macromolecules directly to mitochondria. Our findings shed light on the mechanism of uptake of CPPs by cells. The lack of direct movement of CPPs through mitochondrial phospholipid bilayers, along with the observed endosomal accumulation of Tat and TPP-Tat in cells, makes it unlikely that CPPs enter cells by direct membrane passage, and instead favours cellular uptake via an endocytic pathway.
Biochemical Journal 12/2004; 383(Pt. 3):457-68. · 4.90 Impact Factor
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ABSTRACT: Peptide nucleic acids (PNAs) are effective antisense reagents that bind specific mRNAs preventing their translation. However, PNAs cannot cross cell membranes, hampering delivery to cells. To overcome this problem we made PNAs membrane-permeant by conjugation to the lipophilic triphenylphosphonium (TPP) cation through a disulphide bond. The TPP cation led to efficient PNA uptake into the cytoplasm where the disulphide bond was reduced, releasing the antisense PNA to block expression of its target gene. This method of directing PNAs into cells is a significant improvement on current procedures and will facilitate in vitro and pharmacological applications of PNAs.
FEBS Letters 02/2004; 556(1-3):180-6. · 3.54 Impact Factor
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ABSTRACT: Many proteins contain free thiols that can be modified by the reversible formation of mixed disulfides with low-molecular-weight thiols through a process called S-thiolation. As the majority of these modifications result from the interaction of protein thiols with the endogenous glutathione pool, protein glutathionylation is the predominant alteration. Protein glutathionylation is of significance both for defense against oxidative damage and in redox signaling. As mitochondria are at the heart of both oxidative damage and redox signaling within the cell, the glutathionylation of mitochondrial proteins is of particular importance. Here we review the mechanisms and physiological significance of the glutathionylation of mitochondrial thiol proteins.
Antioxidants and Redox Signaling 7(7-8):999-1010. · 8.46 Impact Factor
