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Mice deficient in Cu,Zn-superoxide dismutase are resistant to acetaminophen toxicity.

ABSTRACT: Although antioxidants are used to treat an overdose of the analgaesic/antipyretic drug APAP (acetaminophen), roles of antioxidant enzymes in APAP-induced hepatotoxicity remain controversial. Our objective was to determine impacts of knockout of SOD1 (superoxide dismutase; Cu,Zn-SOD) alone or in combination with selenium-dependent GPX1 (glutathione peroxidase-1) on APAP-induced hepatotoxicity. All SOD1-null (SOD1-/-) and SOD1- and GPX1-double-knockout mice survived an intraperitoneal injection of 600 mg of APAP per kg of body mass, whereas 75% of WT (wild-type) and GPX1-null mice died within 20 h. Survival time of SOD1-/- mice injected with 1200 mg of APAP per kg of body mass was longer than that of the WT mice (934 compared with 315 min, P<0.05). The APAP-treated SOD1-/- mice had less (P<0.05) plasma ALT (alanine aminotransferase) activity increase and attenuated (P<0.05) hepatic glutathione depletion than the WT mice. The protection conferred by SOD1 deletion was associated with a block of the APAP-mediated hepatic protein nitration and a 50% reduction (P<0.05) in activity of a key APAP metabolism enzyme CYP2E1 (cytochrome P450 2E1) in liver. The SOD1 deletion also caused moderate shifts in the APAP metabolism profiles. In conclusion, deletion of SOD1 alone or in combination with GPX1 greatly enhanced mouse resistance to APAP overdose. Our results suggest a possible pro-oxidant role for the physiological level of SOD1 activity in APAP-mediated hepatotoxicity.

SUBMITTER: Lei XG

PROVIDER: S-EPMC1615904 | biostudies-other | 2006 Nov

REPOSITORIES: biostudies-other

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Cu,Zn-superoxide dismutase increases toxicity of mutant and zinc-deficient superoxide dismutase by enhancing protein stability.

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| S-EPMC2962488 | biostudies-literature

Cu,Zn-superoxide dismutase without Zn is folded but catalytically inactive.

Project description:Amyotrophic lateral sclerosis has been linked to the gain of aberrant function of superoxide dismutase, Cu,Zn-SOD1 upon protein misfolding. The mechanism of SOD1 misfolding is thought to involve mutations leading to the loss of Zn, followed by protein unfolding and aggregation. We show that the removal of Zn from SOD1 may not lead to an immediate unfolding but immediately deactivates the enzyme through a combination of subtle structural and electronic effects. Using quantum mechanics/discrete molecular dynamics, we showed that both Zn-less wild-type (WT)-SOD1 and its D124N mutant that does not bind Zn have at least metastable folded states. In those states, the reduction potential of Cu increases, leading to the presence of detectable amounts of Cu(I) instead of Cu(II) in the active site, as confirmed experimentally. The Cu(I) protein cannot participate in the catalytic Cu(I)-Cu(II) cycle. However, even without the full reduction to Cu(I), the Cu site in the Zn-less variants of SOD1 is shown to be catalytically incompetent: unable to bind superoxide in a way comparable to the WT-SOD1. The changes are more radical and different in the D124N Zn-less mutant than in the Zn-less WT-SOD1, suggesting D124N being perhaps not the most adequate model for Zn-less SOD1. Overall, Zn in SOD1 appears to be influencing the Cu site directly by adjusting its reduction potential and geometry. Thus, the role of Zn in SOD1 is not just structural, as was previously thought; it is a vital part of the catalytic machinery.

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| S-EPMC3264780 | biostudies-literature

Expression, purification and crystallization of Chaetomium thermophilum Cu,Zn superoxide dismutase.

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Project description:The maturation and activation of the anti-oxidant Cu,Zn superoxide dismutase (SOD1) are highly regulated processes that require several post-translational modifications. The maturation of SOD1 is initiated by incorporation of zinc and copper ions followed by disulfide oxidation leading to the formation of enzymatically active homodimers. Our present data indicate that homodimer formation is a regulated final step in SOD1 maturation and implicate the recently characterized copper homeostasis protein COMMD1 in this process. COMMD1 interacts with SOD1, and this interaction requires CCS-mediated copper incorporation into SOD1. COMMD1 does not regulate disulfide oxidation of SOD1 but reduces the level of SOD1 homodimers. RNAi-mediated knockdown of COMMD1 expression results in a significant induction of SOD1 activity and a consequent decrease in superoxide anion concentrations, whereas overexpression of COMMD1 exerts exactly the opposite effects. Here, we identify COMMD1 as a novel protein regulating SOD1 activation and associate COMMD1 function with the production of free radicals.

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Project description:In the present study, we cloned and sequenced the mRNAs of the Sod3 [extracellular Cu Zn SOD (superoxide dismutase)] gene in Drosophila and identified two mRNA products formed by alternative splicing. These products code for a long and short protein derived from the four transcripts found in global expression studies (Flybase numbers Dmel\CG9027, FBgn0033631). Both mRNA process variants contain an extracellular signalling sequence, a region of high homology to the Sod1 (cytoplasmic Cu Zn SOD) including a conserved AUG start, with the longer form also containing a hydrophobic tail. The two fully processed transcripts are homologous to Caenorhabditis elegans Sod3 mRNA showing the same processing pattern. Using an established KG p-element+ insertion line (KG06029), we demonstrate that the Sod3 codes for an active Cu Zn SOD. We found differing expression patterns across sex with higher levels of expression of Sod3 in females. There is a correlation of Sod1 and Sod3 gene expression and activity that can explain why Sod3 was not seen in earlier studies of Sod1. Finally, we found no effect on lifespan with the Sod3 hypomorph mutation (Sod3KG06029) but did observe a significant increase in resistance to paraquat and H2O2 (hydrogen peroxide).

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Cu/Zn Superoxide Dismutase (Sod1) regulates the canonical Wnt signaling pathway.

Project description:Cu/Zn Superoxide Dismutase (Sod1) catalyzes the disproportionation of cytotoxic superoxide radicals (O2•-) into oxygen (O2) and hydrogen peroxide (H2O2), a key signaling molecule. In Saccharomyces cerevisiae, we previously discovered that Sod1 participates in an H2O2-mediated redox signaling circuit that links nutrient availability to the control of energy metabolism. In response to glucose and O2, Sod1-derived H2O2 stabilizes a pair of conserved plasma membrane kinases - yeast casein kinase 1 and 2 (Yck1/2) - that signal glycolytic growth and the repression of respiration. The Yck1/2 homolog in humans, casein kinase 1-γ (CK1γ), is an integral component of the Wingless and Int-1 (Wnt) signaling pathway, which is essential for regulating cell fate and proliferation in early development and adult tissue and is dysregulated in many cancers. Herein, we establish the conservation of the SOD1/YCK1 redox signaling axis in humans by finding that SOD1 regulates CK1γ expression in human embryonic kidney 293 (HEK293) cells and is required for canonical Wnt signaling and Wnt-dependent cell proliferation.

| S-EPMC7785591 | biostudies-literature

Preparation of reduced bovine Cu,Zn superoxide dismutase.

Project description:N.m.r. and e.p.r. were used to measure the oxidation state of copper in Cu,Zn superoxide dismutase treated with reducing agents such as NaBH4, K4Fe(CN)6, Na2S2O4 and H2O2. The activity and the electrophoretic pattern of the treated enzyme were also studied. On the basis of the reducing ability and of the absence of inactivating effects, NaBH4 was the most suitable reducer of those tested. Some characteristics of the reduction of superoxide dismutase by NaBH4 were further investigated. The results obtained indicate that NaBH4 can be used to prepare, in a few minutes, solutions of completely reduced enzyme without any apparent change of the activity and of the structure.

| S-EPMC1145153 | biostudies-other

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