The absence of the SOD1 gene causes abnormal monoaminergic neurotransmission and motivational impairment-like behavior in mice

The Ile35 Residue of the ALS-Associated Mutant SOD1 Plays a Crucial Role in the Intracellular Aggregation of the Molecule

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with an unknown pathogenesis. It has been reported that mutations in the gene for Cu/Zn superoxide dismutase (SOD1) cause familial ALS. Mutant SOD1 undergoes aggregation and forms amyloid more easily, and SOD1-immunopositive inclusions have been observed in the spinal cords of ALS patients. Because of this, SOD1 aggregation is thought to be related to the pathogenesis of ALS. Some core regions of amyloid have been identified, but the issue of whether these regions form aggregates in living cells remains unclear, and the mechanism responsible for intracellular SOD1 aggregation also remains unclear. The findings reported in this study indicate that the aggregation of the ALS-linked mutant SOD1-EGFP was significantly enhanced when the BioID2 gene was fused to the N-terminus of the mutant SOD1-EGFP plasmid for cellular expression. Expression of a series of BioID2-(C-terminal deletion peptides of SOD1)-EGFP permitted us to identify 1-35 as a minimal N-terminal sequence and Ile35 as an essential amino acid residue that contributes to the intracellular aggregation of SOD1. The findings also showed that an additional substitution of Ile35 with Ser into the ALS mutant SOD1 resulted in the significant suppression of aggregate formation. The fact that no Ile35 mutations have been reported to date in ALS patients indicates that all ALS mutant SOD1s contain Ile35. Taken together, we propose that Ile35 plays a pivotal role in the aggregation of the ALS-linked SOD1 and that this study will contribute to our understanding of the mechanism responsible for SOD1 aggregation.

Urinary and Plasma Antioxidants in Behavioral Symptoms of Individuals With Autism Spectrum Disorder

The balance between antioxidant capacity and oxidative stress-induced free radicals may be crucial in the pathophysiological development factor of autism spectrum disorder (ASD). We measured the following urinary and plasma biomarker levels of oxidative stress and antioxidants. As urinary biomarkers, (1) hexanoyl-lysine (HEL), which is a new biomarker of oxidative stress, (2) the total antioxidant capacity (TAC), and (3) 8-hydroxy-2'-deoxyguanosine (8-OHdG), as a product of oxidative modifications to DNA; and the plasma levels of (4) the antioxidant protein superoxide dismutase (SOD), which is the crucial defense again oxygen reactive species, and (5) transferrin and (6) ceruloplasmin, which are biomarkers of iron and copper neurotransmission and oxidant-antioxidant systems. We examined the relationship between these urinary and plasma biomarkers and behavioral symptoms in 19 individuals with ASD (mean age, 10.8 ± 5.2 years) and 10 age-matched healthy controls (mean age, 14.2 ± 7.0 years). Behavioral symptoms were estimated using the Aberrant Behavior Checklist (ABC). Urinary TAC levels were significantly lower, whereas urinary HEL levels were significantly increased in the ASD group as compared with the control group. The five ABC subscale and total scores were significantly raised in the autism group than in the control group. The results of a linear regression analysis revealed that plasma SOD levels may be a more accurate predictor of differences in ABC scores between individuals with ASD and control individuals. The present study firstly revealed the important findings that the cooperation between the urinary antioxidant TAC and plasma SOD levels may contribute to the ABC subscale scores of stereotypy. Urinary TAC activity and antioxidant protein SOD may be associated with incomplete mineral body store and antioxidant-related transcription factor and browning reactions. Consequently, a critical imbalance between TAC urinary levels and plasma SOD levels may be an important contributor to autistic behavioral symptoms.

Highly Stable Pyrimidine Based Luminescent Copper Nanoclusters with Superoxide Dismutase Mimetic and Nitric Oxide Releasing Activity

Copper nanoclusters (CuNCs) are emerging as an interesting class of materials for various biomedical applications. In this work, we have designed highly stable nucleobase-capped luminescent CuNCs and studied the effect of substituents on the cluster composition and photophysical properties. The NCs exhibit exceptional stability in ambient atmosphere and show significant variation in the emission properties with a change in position of substituents on the ligand, thiouracil. This study represents the first example of a nanocluster that functionally mimics the activity of a major antioxidant enzyme, superoxide dismutase (SOD). In addition to their enzyme-mimetic activity, the CuNCs evince controlled release of nitric oxide (NO), a key gaseous molecule of endothelial system from S-nitrosothiol, S-nitrosoglutathione (GSNO). Further, to a greater significance, these luminescent CuNCs are readily taken up by the mammalian cells and exhibit low toxicity. The superoxide dismutase and NO releasing activity of the fluorescent, biocompatible copper nanoclusters suggest their potential application in both therapeutics and bioimaging.

Neuron-glia: understanding cellular copper homeostasis, its cross-talk and their contribution towards neurodegenerative diseases

Over the years, the mechanism of copper homeostasis in various organ systems has gained importance. This is owing to the involvement of copper in a wide range of genetic disorders, most of them involving neurological symptoms. This highlights the importance of copper and its tight regulation in a complex organ system like the brain. It demands understanding the mechanism of copper acquisition and delivery to various cell types overcoming the limitation imposed by the blood brain barrier. The present review aims to investigate the existing work to understand the mechanism and complexity of cellular copper homeostasis in the two major cell types of the CNS - the neurons and the astrocytes. It investigates the mechanism of copper uptake, incorporation and export by these cell types. Furthermore, it brings forth the common as well as the exclusive aspects of neuronal and glial copper homeostasis including the studies from copper-based sensors. Glia act as a mediator of copper supply between the endothelium and the neurons. They possess all the qualifications of acting as a 'copper-sponge' for supply to the neurons. The neurons, on the other hand, require copper for various essential functions like incorporation as a cofactor for enzymes, synaptogenesis, axonal extension, inhibition of postsynaptic excitotoxicity, etc. Lastly, we also aim to understand the neuronal and glial pathology in various copper homeostasis disorders. The etiology of glial pathology and its contribution towards neuronal pathology and vice versa underlies the complexity of the neuropathology associated with the copper metabolism disorders.

Cu/Zn-superoxide dismutase forms fibrillar hydrogels in a pH-dependent manner via a water-rich extended intermediate state

Under certain conditions, amyloid-like fibrils can develop into three-dimensional networks and form hydrogels by a self-assembly process. When Cu/Zn superoxide dismutase (SOD1), an anti-oxidative enzyme, undergoes misfolding, fibrillar aggregates are formed, which are a hallmark of a certain form of familial amyotrophic lateral sclerosis (ALS). However, the issue of whether SOD1 fibrils can be assembled into hydrogels remains to be tested. Here, we show that the SOD1 polypeptides undergo hydrogelation accompanied by the formation of thioflavin T-positive fibrils at pH 3.0 and 4.0, but not at pH 5.0 where precipitates are formed. The results of viscoelastic analyses indicate that the properties of SOD1 hydrogels (2%) were similar to and slightly more fragile than a 0.25% agarose gel. In addition, monitoring by a quartz crystal microbalance with admittance analysis showed that the denaturing of immobilized SOD1 on a sensor under the hydrogelation conditions at pH 3.0 and 4.0 resulted in an increase in the effective acoustic thickness from ~3.3 nm (a folded rigid form) to ~50 and ~100 nm (an extended water-rich state), respectively. In contrast, when SOD1 was denatured under the same conditions at pH 5.0, a compact water-poor state with an effective acoustic thickness of ~10 nm was formed. The addition of physiological concentrations of NaCl to the pH 4.0 sample induced a further extension of the SOD1 with larger amounts of water molecules (with an effective acoustic thickness of ~200 nm) but suppressed hydrogel formation. These results suggest that different denatured intermediate states of the protein before self-assembly play a major role in determining the characteristics of the resulting aggregates and that a conformational change to a suitable level of extended water-rich intermediate state before and/or during intermolecular assembling is required for fibrillation and hydrogelation in the case of globular proteins.

Superoxide dismutases: Dual roles in controlling ROS damage and regulating ROS signaling

Wang et al. review the dual role of superoxide dismutases in controlling reactive oxygen species (ROS) damage and regulating ROS signaling across model systems as well as their involvement in human diseases.

Superoxide dismutases (SODs) are universal enzymes of organisms that live in the presence of oxygen. They catalyze the conversion of superoxide into oxygen and hydrogen peroxide. Superoxide anions are the intended product of dedicated signaling enzymes as well as the byproduct of several metabolic processes including mitochondrial respiration. Through their activity, SOD enzymes control the levels of a variety of reactive oxygen species (ROS) and reactive nitrogen species, thus both limiting the potential toxicity of these molecules and controlling broad aspects of cellular life that are regulated by their signaling functions. All aerobic organisms have multiple SOD proteins targeted to different cellular and subcellular locations, reflecting the slow diffusion and multiple sources of their substrate superoxide. This compartmentalization also points to the need for fine local control of ROS signaling and to the possibility for ROS to signal between compartments. In this review, we discuss studies in model organisms and humans, which reveal the dual roles of SOD enzymes in controlling damage and regulating signaling.