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1. The SOD1 Inhibitor, LCS-1, Oxidizes H2S to Reactive Sulfur Species, Directly and Indirectly, through Conversion of SOD1 to an Oxidase

   https://doi.org/10.3390/antiox13080991  

   Olson, Kenneth R ; Takata, Tsuyoshi ; Clear, Kasey J ; Gao, Yan ; Ma, Zhilin ; Pfaff, Ella ; Mouli, Karthik ; Kent, Thomas A ; Jones, Prentiss ; Fukuto, Jon ; et al ( August 2024 , Antioxidants)

   LCS-1, a putative selective inhibitor of SOD1, is a substituted pyridazinone with rudimentary similarity to quinones and naphthoquinones. As quinones catalytically oxidize H2S to biologically active reactive sulfur species (RSS), we hypothesized LCS-1 might have similar attributes. Here, we examine LCS-1 reactions with H2S and SOD1 using thiol-specific fluorophores, liquid chromatography–mass spectrometry, electron paramagnetic resonance (EPR), UV–vis spectrometry, and oxygen consumption. We show that LCS-1 catalytically oxidizes H2S in buffer solutions to form RSS, namely per- and polyhydrosulfides (H2Sn, n = 2–6). These reactions consume oxygen and produce hydrogen peroxide, but they do not have an EPR signature, nor do they affect the UV–vis spectrum. Surprisingly, LCS-1 synergizes with SOD1, but not SOD2, to oxidize H2S to H2S3-6. LCS-1 forms monothiol adducts with H2S, glutathione (GSH), and cysteine (Cys), but not with oxidized glutathione or cystine; both thiol adducts inhibit LCS-1-SOD1 synergism. We propose that LCS-1 forms an adduct with SOD1 that disrupts the intramolecular Cys57-Cys146 disulfide bond and transforms SOD1 from a dismutase to an oxidase. This would increase cellular ROS and polysulfides, the latter potentially affecting cellular signaling and/or cytoprotection.

    

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2. Comparing therapeutic modulators of the SOD1 G93A Amyotrophic Lateral Sclerosis mouse pathophysiology

   https://doi.org/10.3389/fnins.2022.1111763  

   Lee, Albert J. ; Kittel, Tyler E. ; Kim, Renaid B. ; Bach, Thao-Nguyen ; Zhang, Tian ; Mitchell, Cassie S. ( January 2023 , Frontiers in Neuroscience)

   Introduction Amyotrophic Lateral Sclerosis (ALS) is a paralyzing, multifactorial neurodegenerative disease with limited therapeutics and no known cure. The study goal was to determine which pathophysiological treatment targets appear most beneficial. Methods A big data approach was used to analyze high copy SOD1 G93A experimental data. The secondary data set comprised 227 published studies and 4,296 data points. Treatments were classified by pathophysiological target: apoptosis, axonal transport, cellular chemistry, energetics, neuron excitability, inflammation, oxidative stress, proteomics, or systemic function. Outcome assessment modalities included onset delay, health status (rotarod performance, body weight, grip strength), and survival duration. Pairwise statistical analysis (two-tailed t -test with Bonferroni correction) of normalized fold change (treatment/control) assessed significant differences in treatment efficacy. Cohen’s d quantified pathophysiological treatment category effect size compared to “all” (e.g., all pathophysiological treatment categories combined). Results Inflammation treatments were best at delaying onset ( d = 0.42, p > 0.05). Oxidative stress treatments were significantly better for prolonging survival duration ( d = 0.18, p < 0.05). Excitability treatments were significantly better for prolonging overall health status ( d = 0.22, p < 0.05). However, the absolute best pathophysiological treatment category for prolonging health status varied with disease progression: oxidative stress was best for pre-onset health ( d = 0.18, p > 0.05); excitability was best for prolonging function near onset ( d = 0.34, p < 0.05); inflammation was best for prolonging post-onset function ( d = 0.24, p > 0.05); and apoptosis was best for prolonging end-stage function ( d = 0.49, p > 0.05). Finally, combination treatments simultaneously targeting multiple pathophysiological categories (e.g., polytherapy) performed significantly ( p < 0.05) better than monotherapies at end-stage. Discussion In summary, the most effective pathophysiological treatments change as function of assessment modality and disease progression. Shifting pathophysiological treatment category efficacy with disease progression supports the homeostatic instability theory of ALS disease progression. 

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3. Oxidation of Dueling Cysteine Promotes Subunit Exchange in SOD1

   https://doi.org/10.1021/acschemneuro.3c00174  

   Zhang, Ao Yun ; Dashnaw, Chad M. ; Gonzalez, Mayte ; Koone, Jordan C. ; Wells, Nick A. ; Smith, Colin A. ; Guberman-Pfeffer, Matthew J. ; Shaw, Bryan F. ( April 2023 , ACS Chemical Neuroscience)

   The heterodimerization of wild-type (WT) Cu, Zn superoxide dismutase-1 (SOD1) and mutant SOD1 might be a critical step in the pathogenesis of SOD1-linked amyotrophic lateral sclerosis (ALS). Post-translational modifications that accelerate SOD1 heterodimerization remain unidentified. Here, we used capillary electrophoresis to quantify the effect of cysteine-111 oxidation on the rate and free energy of ALS mutant/WT SOD1 heterodimerization. The oxidation of Cys111-β-SH to sulfinic and sulfonic acid (by hydrogen peroxide) increased rates of heterodimerization (with unoxidized protein) by ∼3-fold. Cysteine oxidation drove the equilibrium free energy of SOD1 heterodimerization by up to ΔΔG = −5.11 ± 0.36 kJ mol–1. Molecular dynamics simulations suggested that this enhanced heterodimerization, between oxidized homodimers and unoxidized homodimers, was promoted by electrostatic repulsion between the two “dueling” Cys111-SO2–/SO3–, which point toward one another in the homodimeric state. Together, these results suggest that oxidation of Cys-111 promotes subunit exchange between oxidized homodimers and unoxidized homodimers, regardless of whether they are mutant or WT dimers. 

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4. Kinetic Variability in Seeded Formation of ALS-Linked SOD1 Fibrils Across Multiple Generations

   https://doi.org/10.1021/acschemneuro.9b00464  

   Baumer, Katelyn M. ; Koone, Jordan C. ; Shaw, Bryan F. ( January 2020 , ACS Chemical Neuroscience)
5. Free energy calculations of ALS‐causing SOD1 mutants reveal common perturbations to stability and dynamics along the maturation pathway

   https://doi.org/10.1002/pro.4132  

   Wells, Nicholas G. M. ; Tillinghast, Grant A. ; O'Neil, Alison L. ; Smith, Colin A. ( June 2021 , Protein Science)

   With over 150 heritable mutations identified as disease‐causative, superoxide dismutase 1 (SOD1) has been a main target of amyotrophic lateral sclerosis (ALS) research and therapeutic efforts. However, recent evidence has suggested that neither loss of function nor protein aggregation is responsible for promoting neurotoxicity. Furthermore, there is no clear pattern to the nature or the location of these mutations that could suggest a molecular mechanism behind SOD1‐linked ALS. Here, we utilize reliable and accurate computational techniques to predict the perturbations of 10 such mutations to the free energy changes of SOD1 as it matures from apo monomer to metallated dimer. We find that the free energy perturbations caused by these mutations strongly depend on maturational progress, indicating the need for state‐specific therapeutic targeting. We also find that many mutations exhibit similar patterns of perturbation to native and non‐native maturation, indicating strong thermodynamic coupling between the dynamics at various sites of maturation within SOD1. These results suggest the presence of an allosteric network in SOD1 which is vulnerable to disruption by these mutations. Analysis of these perturbations may contribute to uncovering a unifying molecular mechanism which explains SOD1‐linked ALS and help to guide future therapeutic efforts.

    

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