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Activation of brain calcineurin (Cn) by Cu-Zn superoxide dismutase (SOD1) depends on direct SOD1-Cn protein interactions occurring in vitro and in vivo.

ABSTRACT: Cn (calcineurin) activity is stabilized by SOD1 (Cu-Zn superoxide dismutase), a phenomenon attributed to protection from superoxide (O2*-). The effects of O2*- on Cn are still controversial. We found that O2*-, generated either in vitro or in vivo did not affect Cn activity. Yet native bovine, recombinant human or rat, and two chimaeras of human SOD1-rat SOD1, all activated Cn, but SOD2 (Mn-superoxide dismutase) did not affect Cn activity. There was also a poor correlation between SOD1 dismutase activity and Cn activation. A chimaera of human N-terminal SOD1 and rat C-terminal SOD1 had little detectable dismutase activity, yet stimulated Cn activity the same as full-length human or rat SOD1. Nevertheless, there was evidence that the active site of SOD1 was involved in Cn activation based on the loss of activation following chelation of Cu from the active site of SOD1. Also, SOD1 engaged in the catalysis of O2*- dismutation was ineffective in activating Cn. SOD1 activation of Cn resulted from a 90-fold decrease in phosphatase K(m) without a change in V(max). A possible mechanism for the activation of Cn was identified in our studies as the prevention of Fe and Zn losses from the active site of Cn, suggesting a conformation-dependent SOD1-Cn interaction. In neurons, SOD1 and Cn were co-localized in cytoplasm and membranes, and SOD1 co-immunoprecipitated with Cn from homogenates of brain hippocampus and was present in immunoprecipitates as large multimers. Pre-incubation of pure SOD1 with Cn caused SOD1 multimer formation, an indication of an altered conformational state in SOD1 upon interaction with Cn.

SUBMITTER: Agbas A

PROVIDER: S-EPMC1925239 | biostudies-other | 2007 Jul

REPOSITORIES: biostudies-other

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

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| S-EPMC7785591 | biostudies-literature

Impaired Cu-Zn Superoxide Dismutase (SOD1) and Calcineurin (Cn) Interaction in ALS: A Presumed Consequence for TDP-43 and Zinc Aggregation in Tg SOD1G93A Rodent Spinal Cord Tissue.

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Project description:Resistance of the snail Biomphalaria glabrata to the trematode Schistosoma mansoni is correlated with allelic variation at copper-zinc superoxide dismutase (sod1). We tested whether there is a fitness cost associated with carrying the most resistant allele in three outbred laboratory populations of snails. These three populations were derived from the same base population, but differed in average resistance. Under controlled laboratory conditions we found no cost of carrying the most resistant allele in terms of fecundity, and a possible advantage in terms of growth and mortality. These results suggest that it might be possible to drive resistant alleles of sod1 into natural populations of the snail vector for the purpose of controlling transmission of S. mansoni. However, we did observe a strong effect of genetic background on the association between sod1 genotype and resistance. sod1 genotype explained substantial variance in resistance among individuals in the most resistant genetic background, but had little effect in the least resistant genetic background. Thus, epistatic interactions with other loci may be as important a consideration as costs of resistance in the use of sod1 for vector manipulation.

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Project description:When replete with zinc and copper, amyotrophic lateral sclerosis (ALS)-associated mutant SOD proteins can protect motor neurons in culture from trophic factor deprivation as efficiently as wild-type SOD. However, the removal of zinc from either mutant or wild-type SOD results in apoptosis of motor neurons through a copper- and peroxynitrite-dependent mechanism. It has also been shown that motor neurons isolated from transgenic mice expressing mutant SODs survive well in culture but undergo apoptosis when exposed to nitric oxide via a Fas-dependent mechanism. We combined these two parallel approaches for understanding SOD toxicity in ALS and found that zinc-deficient SOD-induced motor neuron death required Fas activation, whereas the nitric oxide-dependent death of G93A SOD-expressing motor neurons required copper and involved peroxynitrite formation. Surprisingly, motor neuron death doubled when Cu,Zn-SOD protein was either delivered intracellularly to G93A SOD-expressing motor neurons or co-delivered with zinc-deficient SOD to nontransgenic motor neurons. These results could be rationalized by biophysical data showing that heterodimer formation of Cu,Zn-SOD with zinc-deficient SOD prevented the monomerization and subsequent aggregation of zinc-deficient SOD under thiol-reducing conditions. ALS mutant SOD was also stabilized by mutating cysteine 111 to serine, which greatly increased the toxicity of zinc-deficient SOD. Thus, stabilization of ALS mutant SOD by two different approaches augmented its toxicity to motor neurons. Taken together, these results are consistent with copper-containing zinc-deficient SOD being the elusive "partially unfolded intermediate" responsible for the toxic gain of function conferred by ALS mutant SOD.

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| S-EPMC1145153 | biostudies-other

Post-translational modification of Cu/Zn superoxide dismutase under anaerobic conditions.

Project description:In eukaryotic organisms, the largely cytosolic copper- and zinc-containing superoxide dismutase (Cu/Zn SOD) enzyme represents a key defense against reactive oxygen toxicity. Although much is known about the biology of this enzyme under aerobic conditions, less is understood regarding the effects of low oxygen levels on Cu/Zn SOD enzymes from diverse organisms. We show here that like bakers' yeast (Saccharomyces cerevisiae), adaptation of the multicellular Caenorhabditis elegans to growth at low oxygen levels involves strong downregulation of its Cu/Zn SOD. Much of this regulation occurs at the post-translational level where CCS-independent activation of Cu/Zn SOD is inhibited. Hypoxia inactivates the endogenous Cu/Zn SOD of C. elegans Cu/Zn SOD as well as a P144 mutant of S. cerevisiae Cu/Zn SOD (herein denoted Sod1p) that is independent of CCS. In our studies of S. cerevisiae Sod1p, we noted a post-translational modification to the inactive enzyme during hypoxia. Analysis of this modification by mass spectrometry revealed phosphorylation at serine 38. Serine 38 represents a putative proline-directed kinase target site located on a solvent-exposed loop that is positioned at one end of the Sod1p ?-barrel, a region immediately adjacent to residues previously shown to influence CCS-dependent activation. Although phosphorylation of serine 38 is minimal when the Sod1p is abundantly active (e.g., high oxygen level), up to 50% of Sod1p can be phosphorylated when CCS activation of the enzyme is blocked, e.g., by hypoxia or low-copper conditions. Serine 38 phosphorylation can be a marker for inactive pools of Sod1p.

| S-EPMC3264780 | biostudies-literature

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