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Hongli Wu, Kuiyi Xing, Ye-Shih Ho, Marjorie F. Lou; Glutaredoxin2 (grx2) Can Protect Mitochondrial Proteins From Oxidative Damage By Its Dethiolase Activity. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5294.
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Oxidation damage of mitochondrial proteins is one of the leading causes for apoptosis. Previously we have reported that mitochondrial glutaredoxin2 (Grx2), an isozyme of thioltransferase (TTase or Grx1), has both dethiolase and peroxidase activities with an anti-apoptotic function. This study is to examine if Grx2 may protect mitochondrial proteins from oxidative damage via its dethiolase capability.
Primary lens epithelial cell cultures (LECs) were established from wild-type (WT) and Grx2-knockout (Grx2 KO) mice. LECs were treated with 150 µM H2O2 for 6 h and apoptosis was determined by caspase3/7 activity assay. ATP level and Complex I activity were measured by spectrophotometric assays. Purified recombinant Grx2 (rGrx2) and its C70S-C73S double mutants were loaded into LECs by transfection. Oxidation of mitochondrial proteins was monitored by protein glutathionylation (PSSG) after treating isolated mitochondria from the liver of WT and Grx2 KO mice with and without 1 mM H2O2 for 30 min. Some Grx2 KO mitochondria were pretreated with 10 µM rGrx2 plus 5 mM GSH before oxidation. Complex I was pull down from mitochondria with an immunocaptured kit. PSSG was measured by immunoblotting using anti-PSSG antibody.
Grx2 KO cells grew normally as the WT cells with the same basal ATP level and complex I activity, however they were more sensitive to oxidative stress as indicated by more caspase3/7 activation, ATP loss, complex I inhibition and more PSSG formation. Importing rGrx2, but not its mutated protein could normalize these H2O2-induced changes. Deletion of Grx2 caused a marked increase in glutathionylation of the total liver mitochondrial proteins upon exposure to H2O2, in particular the p75 subunit of complex I, which could be dethiolated when the mitochondria was pretreated with rGrx2.
Grx2 can protect the mitochondrial proteins in the lens epithelial cells or the liver against oxidative damage via its dethiolase capability.
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