Novel Mutations that Enhance or Repress the Aggregation Potential of SOD1

Krishnan, Uma Maheswari; Son, Marjatta; Rajendran, Bhagya; Elliott, Jeffrey L.

doi:10.1007/s11010-005-9112-4

Cited by 13 publications

(16 citation statements)

References 35 publications

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“…These multimers are SDS-resistant complexes, andremain intact after being boiled in Laemelli's sample buffer (typically containing 0.1-2.0% SDS and 5% b-mercaptoethanol). Other studies have also identified high molecular weight structures in denaturing SDS-PAGE in tissues from G93A mutant transgenic mice [31,32]. The SOD1 SDS-resistant complexes seen in SDS-PAGE generally ranges in size from dimers up to small oligomers (Fig.…”

Section: Discussionmentioning

confidence: 88%

Oxidative Modification of Cysteine 111 Promotes Disulfide Bond-Independent Aggregation of SOD1

et al. 2012

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Converging evidence indicates that SOD1 aggregation is a common feature of mutant SOD1-linked fALS, and seems to be directly related to the gain-of-function toxic property. However, the mechanism inducing the aggregation is not understood. To study the contribution of oxidative modification of cysteine residues in SOD1 aggregation, we systematically examined the redox state of SOD1 cysteine residues in the G37R transgenic mouse model at different stages of the disease and under oxidative stress induced by H₂O₂. Our data suggest that under normal circumstance, cysteine 111 residue in SOD1 is free; however, under oxidative stress, it is prone to oxidative modification by providing the thiolate anion (S-). With the progression of the disease, increased levels of oxidative insults facilitated the oxidation of thiol groups of cysteine residues; human mutant SOD1 could generate an upper shift band in reducing SDS-PAGE, which turned out to be a Cys111-peroxidized SOD1 species. We also detected the formation of SOD1 multimers at different stages of the disease, and found that accumulated oxidative stress facilitated the formation of aggregates, which were not mediated by disulfide bond. This oxidative modification of cysteine 111 therefore promotes the formation of disulfide bond-independent aggregation of SOD1.

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Section: Discussionmentioning

confidence: 88%

Oxidative Modification of Cysteine 111 Promotes Disulfide Bond-Independent Aggregation of SOD1

et al. 2012

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“…The D83 residue coordinates zinc binding to SOD1, and is required for the correct folding of human SOD1 (37). Thus, mutating the D83 residue is likely to interfere with the correct folding of SOD1 and potentially affect SOD1 activity.…”

Section: Resultsmentioning

confidence: 99%

“…It has been previously reported that mutant SOD1 has decreased half-life compared with WT SOD1 (42), and potentially the inability of D83G SOD1 to coordinate zinc may contribute to its instability (37,43,44). …”

Section: Discussionmentioning

confidence: 99%

A novel SOD1-ALS mutation separates central and peripheral effects of mutant SOD1 toxicity

Joyce

McGoldrick

Saccon

et al. 2014

Human Molecular Genetics

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Transgenic mouse models expressing mutant superoxide dismutase 1 (SOD1) have been critical in furthering our understanding of amyotrophic lateral sclerosis (ALS). However, such models generally overexpress the mutant protein, which may give rise to phenotypes not directly relevant to the disorder. Here, we have analysed a novel mouse model that has a point mutation in the endogenous mouse Sod1 gene; this mutation is identical to a pathological change in human familial ALS (fALS) which results in a D83G change in SOD1 protein. Homozgous Sod1D83G/D83G mice develop progressive degeneration of lower (LMN) and upper motor neurons, likely due to the same unknown toxic gain of function as occurs in human fALS cases, but intriguingly LMN cell death appears to stop in early adulthood and the mice do not become paralyzed. The D83 residue coordinates zinc binding, and the D83G mutation results in loss of dismutase activity and SOD1 protein instability. As a result, Sod1D83G/D83G mice also phenocopy the distal axonopathy and hepatocellular carcinoma found in Sod1 null mice (Sod1−/−). These unique mice allow us to further our understanding of ALS by separating the central motor neuron body degeneration and the peripheral effects from a fALS mutation expressed at endogenous levels.

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“…Prior studies of mutant SOD1 in tissues from G93A mice had identified high molecular weight structures in denaturing SDS-PAGE that were interpreted to represent SDS-resistant complexes (16,41,42). The SDS-resistant high molecular weight SOD1 seen in SDS-PAGE generally ranges in size from dimers to molecules of a mass no larger than relatively small oligomers (no more than 10 -20 subunits).…”

Section: Discussionmentioning

confidence: 99%

A Limited Role for Disulfide Cross-linking in the Aggregation of Mutant SOD1 Linked to Familial Amyotrophic Lateral Sclerosis

Karch

Borchelt

2008

Journal of Biological Chemistry

135

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One of the mechanisms by which mutations in superoxide dismutase 1 (SOD1) cause familial amyotrophic lateral sclerosis (fALS) is proposed to involve the accumulation of detergentinsoluble, disulfide-cross-linked, mutant protein. Recent studies have implicated cysteine residues at positions 6 and 111 as critical in mediating disulfide cross-linking and promoting aggregation. In the present study, we used a panel of experimental and disease-linked mutations at cysteine residues of SOD1 (positions 6, 57, 111, and 146) in cell culture assays for aggregation to demonstrate that extensive disulfide cross-linking is not required for the formation of mutant SOD1 aggregates. Experimental mutants possessing only a single cysteine residue or lacking cysteine entirely were found to retain high potential to aggregate. Furthermore we demonstrate that aggregate structures in symptomatic SOD1-G93A mice can be dissociated such that they no longer sediment upon ultracentrifugation (i.e. appear soluble) under relatively mild conditions that leave disulfide bonds intact. Similar to other recent work, we found that cysteines 6 and 111, particularly the latter, play interesting roles in modulating the aggregation of human SOD1. However, we did not find that extensive disulfide cross-linking via these residues, or any other cysteine, is critical to aggregate structure. Instead we suggest that these residues participate in other features of the protein that, in some manner, modulate aggregation.Amyotrophic lateral sclerosis (ALS), 2 a progressive neurodegenerative disease characterized by the loss of upper and lower motor neurons, typically presents with unknown etiology (sporadic ALS). Rarely cases of ALS exhibit dominant patterns of inheritance (familial ALS), and a subset of these cases are caused by mutations in SOD1 (1). More than 100 mutations in SOD1 have been identified in cases of fALS. The majority of these fALS-linked SOD1 mutations are point mutations. A subset of fALS mutations causes shifts in the reading frame or introduces early termination codons, resulting in the production of C-terminally truncated proteins.SOD1 is a metalloenzyme responsible for metabolizing oxygen radicals that are produced during normal cellular metabolism. The active enzyme is a homodimer of two 153-amino acid subunits with each subunit containing eight ␤-strands, an active site that binds copper, a binding site for zinc, an electrostatic loop that directs the substrate into the active site, and an intramolecular disulfide bond between cysteine 57 and cysteine 146 (2). Together these structural aspects of SOD1 produce an extremely stable protein, retaining its structure in 1% SDS and 8 M urea (3). SOD1 is primarily located in the cytosol but has been found at lower levels in nuclei, peroxisomes, and mitochondria (4 -6).The effects of fALS mutations on the normal enzyme activity, turnover, and folding of SOD1 vary considerably (7-9). In cell culture and in vitro models, enzyme activity ranges from undetectable to near normal (7, 10 -13); most muta...

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Novel Mutations that Enhance or Repress the Aggregation Potential of SOD1

Cited by 13 publications

References 35 publications

Oxidative Modification of Cysteine 111 Promotes Disulfide Bond-Independent Aggregation of SOD1

Oxidative Modification of Cysteine 111 Promotes Disulfide Bond-Independent Aggregation of SOD1

A novel SOD1-ALS mutation separates central and peripheral effects of mutant SOD1 toxicity

A Limited Role for Disulfide Cross-linking in the Aggregation of Mutant SOD1 Linked to Familial Amyotrophic Lateral Sclerosis

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