Glycation proceeds faster in mutated Cu, Zn-superoxide dismutases related to familial amyotrophic lateral sclerosis

Receptors for Advanced Glycation End Products (RAGE): Promising Targets Aiming at the Treatment of Neurodegenerative Conditions

Advanced glycation end products (AGEs) are compounds formed after the non-enzymatic addition of reducing sugars to lipids, proteins, and nucleic acids. They are associated with the development of various clinical complications observed in diabetes and cardiovascular diseases, such as retinopathy, nephropathy, diabetic neuropathy, and others. In addition, compelling evidence indicates that these molecules participate in the progression of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Multiple cellular and molecular alterations triggered by AGEs that could alter homeostasis have been identified. One of the main targets for AGE signaling is the receptor for advanced glycation end-products (RAGE). Importantly, this receptor is the target of not only AGEs, but also amyloid β peptides, HMGB1 (high-mobility group box-1), members of the S100 protein family, and glycosaminoglycans. The activation of this receptor induces intracellular signaling cascades that are involved in pathological processes and cell death. Therefore, RAGE represents a key target for pharmacological interventions in neurodegenerative diseases. This review will discuss the various effects of AGEs and RAGE activation in the pathophysiology of neurodegenerative diseases, as well as the currently available pharmacological tools and promising drug candidates.

Role of glycosyltransferases in carcinogenesis; growth factor signaling and EMT/MET programs

The glycosylation of cell surface receptors has been shown to regulate each step of signal transduction, including receptor trafficking to the cell surface, ligand binding, dimerization, phosphorylation, and endocytosis. In this review we focus on the role of glycosyltransferases that are involved in the modification of N-glycans, such as the effect of branching and elongation in signaling by various cell surface receptors. In addition, the role of those enzymes in the EMT/MET programs, as related to differentiation and cancer development, progress and therapy resistance is discussed.

The Taming of Nuclear Factor Erythroid-2-Related Factor-2 (Nrf2) Deglycation by Fructosamine-3-Kinase (FN3K)-Inhibitors-A Novel Strategy to Combat Cancers

Simple Summary

Aim of this review is to provide an overview on (a) Fructosamine-3-Kinase (FN3K) and its role in regulating Nuclear Factor Erythorid-2-Related Factor-2 (Nrf2); (b) the role of glycation and deglycation mechanisms in modulating the functional properties of proteins, in particular, the Nrf2; (c) the dual role of Nrf2 in the prevention and treatment of cancers. Since controlling the glycation of Nrf2 is one of the key mechanisms determining the fate of a cell; whether to get transformed into a cancerous one or to stay as a normal one, it is important to regulate Nrf2 and deglycating FN3K using pharmacological agents. Inhibitors of FN3K are being explored currently to modulate Nrf2 activity thereby control the cancers.

Abstract

Glycated stress is mediated by the advanced glycation end products (AGE) and the binding of AGEs to the receptors for advanced glycation end products (RAGEs) in cancer cells. RAGEs are involved in mediating tumorigenesis of multiple cancers through the modulation of several downstream signaling cascades. Glycated stress modulates various signaling pathways that include p38 mitogen-activated protein kinase (p38 MAPK), nuclear factor kappa–B (NF-κB), tumor necrosis factor (TNF)-α, etc., which further foster the uncontrolled proliferation, growth, metastasis, angiogenesis, drug resistance, and evasion of apoptosis in several cancers. In this review, a balanced overview on the role of glycation and deglycation in modulating several signaling cascades that are involved in the progression of cancers was discussed. Further, we have highlighted the functional role of deglycating enzyme fructosamine-3-kinase (FN3K) on Nrf2-driven cancers. The activity of FN3K is attributed to its ability to deglycate Nrf2, a master regulator of oxidative stress in cells. FN3K is a unique protein that mediates deglycation by phosphorylating basic amino acids lysine and arginine in various proteins such as Nrf2. Deglycated Nrf2 is stable and binds to small musculoaponeurotic fibrosarcoma (sMAF) proteins, thereby activating cellular antioxidant mechanisms to protect cells from oxidative stress. This cellular protection offered by Nrf2 activation, in one way, prevents the transformation of a normal cell into a cancer cell; however, in the other way, it helps a cancer cell not only to survive under hypoxic conditions but also, to stay protected from various chemo- and radio-therapeutic treatments. Therefore, the activation of Nrf2 is similar to a double-edged sword and, if not controlled properly, can lead to the development of many solid tumors. Hence, there is a need to develop novel small molecule modulators/phytochemicals that can regulate FN3K activity, thereby maintaining Nrf2 in a controlled activation state.

Promiscuous Roles of Autophagy and Proteasome in Neurodegenerative Proteinopathies

Alterations in autophagy and the ubiquitin proteasome system (UPS) are commonly implicated in protein aggregation and toxicity which manifest in a number of neurological disorders. In fact, both UPS and autophagy alterations are bound to the aggregation, spreading and toxicity of the so-called prionoid proteins, including alpha synuclein (α-syn), amyloid-beta (Aβ), tau, huntingtin, superoxide dismutase-1 (SOD-1), TAR-DNA-binding protein of 43 kDa (TDP-43) and fused in sarcoma (FUS). Recent biochemical and morphological studies add to this scenario, focusing on the coordinated, either synergistic or compensatory, interplay that occurs between autophagy and the UPS. In fact, a number of biochemical pathways such as mammalian target of rapamycin (mTOR), transcription factor EB (TFEB), Bcl2-associated athanogene 1/3 (BAG3/1) and glycogen synthase kinase beta (GSk3β), which are widely explored as potential targets in neurodegenerative proteinopathies, operate at the crossroad between autophagy and UPS. These biochemical steps are key in orchestrating the specificity and magnitude of the two degradation systems for effective protein homeostasis, while intermingling with intracellular secretory/trafficking and inflammatory pathways. The findings discussed in the present manuscript are supposed to add novel viewpoints which may further enrich our insight on the complex interactions occurring between cell-clearing systems, protein misfolding and propagation. Discovering novel mechanisms enabling a cross-talk between the UPS and autophagy is expected to provide novel potential molecular targets in proteinopathies.

Glycation With Fructose: The Bitter Side of Nature's Own Sweetener

Fructose is a ketohexose and sweetest among all the natural sugars. Like other reducing sugars, it reacts readily with the amino- and nucleophilic groups of proteins, nucleic acids and other biomolecules resulting in glycation reactions. The non-enzymatic glycation reactions comprise Schiff base formation, their Amadori rearrangement followed by complex and partly incompletely understood reactions culminating in the formation of Advance Glycation End products (AGEs). The AGEs are implicated in complications associated with diabetes, cardiovascular disorders, Parkinson's disease, etc. Fructose is highly reactive and forms glycation products that differ both in structure and reactivity as compared to those formed from glucose. Nearly all tissues of higher organisms utilize fructose but only a few like the ocular lens, peripheral nerves erythrocytes and testis have polyol pathway active for the synthesis of fructose. Fructose levels rarely exceed those of glucose but, in tissues that operate the polyol pathway, its concentration may rise remarkably during diabetes and related disorders. Diet contributes significantly to the body fructose levels however, availability of technologies for the large scale and inexpensive production of fructose, popularity of high fructose syrups as well as the promotion of vegetarianism have resulted in a remarkable increase in the consumption of fructose. In vivo glycation reactions by fructose, therefore, assume remarkable significance. The review, therefore, aims to highlight the uniqueness of glycation reactions with fructose and its role in some pathophysiological situations.

The biophysics of superoxide dismutase-1 and amyotrophic lateral sclerosis

Few proteins have come under such intense scrutiny as superoxide dismutase-1 (SOD1). For almost a century, scientists have dissected its form, function and then later its malfunction in the neurodegenerative disease amyotrophic lateral sclerosis (ALS). We now know SOD1 is a zinc and copper metalloenzyme that clears superoxide as part of our antioxidant defence and respiratory regulation systems. The possibility of reduced structural integrity was suggested by the first crystal structures of human SOD1 even before deleterious mutations in the sod1 gene were linked to the ALS. This concept evolved in the intervening years as an impressive array of biophysical studies examined the characteristics of mutant SOD1 in great detail. We now recognise how ALS-related mutations perturb the SOD1 maturation processes, reduce its ability to fold and reduce its thermal stability and half-life. Mutant SOD1 is therefore predisposed to monomerisation, non-canonical self-interactions, the formation of small misfolded oligomers and ultimately accumulation in the tell-tale insoluble inclusions found within the neurons of ALS patients. We have also seen that several post-translational modifications could push wild-type SOD1 down this toxic pathway. Recently we have come to view ALS as a prion-like disease where both the symptoms, and indeed SOD1 misfolding itself, are transmitted to neighbouring cells. This raises the possibility of intervention after the initial disease presentation. Several small-molecule and biologic-based strategies have been devised which directly target the SOD1 molecule to change the behaviour thought to be responsible for ALS. Here we provide a comprehensive review of the many biophysical advances that sculpted our view of SOD1 biology and the recent work that aims to apply this knowledge for therapeutic outcomes in ALS.

Food advanced glycation end products as potential endocrine disruptors: An emerging threat to contemporary and future generation

Mankind exposure to chemicals in the past century has increased dramatically throughout environment. There is no question that chemicals interfere with the physiology of biological system. Abundance of chemicals is documented to be detrimental to human and wildlife. The mammalian endocrine system is comprised of many interacting tissues mediate themselves through hormones that are essential for metabolism, growth and development. Humans secrete over fifty different hormones to orchestrate major physiological functions however; these vital functions can be intervened by huge number of internal and external chemical stressors that are identified as endocrine disruptors. Advanced glycation end products (AGEs), familiarly known as Maillard products, formed through non-enzymatic glycation whose production is augmented on aging as well as environmental stressors. Processed foods have become very popular today due to their taste, convenience, and inexpensiveness. Manufacture of these day-to-day foods involves extreme temperatures on processing results in the formation of AGEs could independently promote oxidative stress, aging, diabetes, cancer, degenerative diseases, more fascinatingly hormonal disruption is the subject of interest of this review. Based on some substantial observations documented till time, we discuss the emergence of dietary AGEs as potential endocrine disruptors by emphasizing their occurrence, mechanisms and participation in endocrine interruption. Both economically and in terms of human life, AGEs may represent an enormous cost for the future society. Therefore, by explicating their novel role in endocrine diseases, the review strives to make an impact on AGEs and their exposure among public as well as scientific communities.

An insight on the association of glycation with hepatocellular carcinoma

Hepato-cellular carcinoma (HCC) is one of the frequent cause of cancer-related death worldwide and dominant form of primary liver cancer. However, the reason behind a steady increase in the incidence of this form of cancer remains elusive. Glycation has been reported to play a significant role in the induction of several chronic diseases including cancer. Several risk factors that could induce HCC have been reported in the literature. Deciphering the complex patho-physiology associated with HCC is expected to provide new targets for the early detection, prevention, progression and recurrence. Even-though, some of the causative aspects of HCC is known, the advanced glycation end products (AGEs) related mechanism still needs further research. In the current manuscript, we have tried to uncover the possible role of glycation in the induction of HCC. In the light of the available scientific literature, we advocate in-depth comprehensive studies which will shed light towards mechanistic association of glycation with HCC.

Glycation in Demetalated Superoxide Dismutase 1 Prevents Amyloid Aggregation and Produces Cytotoxic Ages Adducts

Superoxide dismutase 1 (SOD1) has been implicated with familial amyotrophic lateral sclerosis (fALS) through accumulation of protein amyloid aggregates in motor neurons of patients. Amyloid aggregates and protein inclusions are a common pathological feature of many neurological disorders in which protein aggregation seems to be directly related to neurotoxicity. Although, extensive studies performed on the aggregation process of several amyloidogenic proteins in vitro allowed the identification of many physiological factors involved, the molecular mechanisms underlying the formation of amyloid aggregates in vivo and in pathological conditions are still poorly understood. Post-translational modifications are known to affect protein structure and function and, recently, much attention has been devoted to the role played by non-enzymatic glycation in stimulating amyloid aggregation and cellular toxicity. In particular, glycation seems to have a determining role both in sporadic and familial forms of ALS and SOD1 has been shown to be glycated in vivo The aim of this study was to investigate the role of glycation on the amyloid aggregation process of both wild-type SOD1 and its ALS-related mutant G93A. To this aim, the glycation kinetics of both native and demetalated SOD have been followed using two different glycating agents, i.e., D-ribose and methylglyoxal. The effect of glycation on the structure and the amyloid aggregation propensity of native and ApoSOD has been also investigated using a combination of biophysical and biochemical techniques. In addition, the effect of SOD glycated species on cellular toxicity and reactive oxygen species (ROS) production has been evaluated in different cellular models. The results provided by this study contribute to clarify the role of glycation in amyloid aggregation and suggest a direct implication of glycation in the pathology of fALS.

Receptor for advanced glycation end-products in neurodegenerative diseases

This review, for the first time, aims to summarize the current knowledge in the emerging field of RAGE (receptor for advanced glycation end-products) studies in neurodegeneration and neurodegenerative diseases. RAGE, a member of the multiligand cell surface immunoglobulin family, has been implicated in numerous pathological conditions - from diabetes and cardiovascular diseases to tumors and neurodegenerative disorders, such as Alzheimer's disease, familial amyloid polyneuropathy, diabetic neuropathy, Parkinson's disease, and Huntington's disease. Until now, the detailed mechanisms of the contribution of RAGE to neurodegeneration remain elusive; however, mounting evidence suggests that its detrimental actions are triggered by its ligand interactions and contribute to increased neuroinflammation, neuronal degeneration, and apoptosis. Deciphering the role of RAGE in neurodegenerative disorders will be a milestone in our basic understanding of the mechanisms involved in the pathogenesis of neurodegeneration, helping to delineate molecular links between complex RAGE signaling pathways and neuronal dysfunction and neurodegeneration.

Goji fruit (Lycium barbarum) protects sciatic nerve function against crush injury in a model of diabetic stress

Excess fructose consumption causes changes in functioning of the central and peripheral nervous systems, which increase the vulnerability of peripheral nerves to traumatic injury. The aim of this study was to evaluate the electrophysiological parameters of responses of motoneurons of the spinal cord at high-frequency stimulation of the distal part of the injured sciatic nerve in a model of diabetic stress under action of Lycium barbarum (LB). Male albino rats were given with drinking water with 50% concentration of dietary fructose for 6 weeks. Starting on the 7th week a crush injury of the left sciatic nerve was carried out. Some of the animals received fructose post-injury for 3 weeks and some of the animals received fructose+dry LB fruits for 3 weeks. In the fructose+crush+LВ group a relatively proportional division of tetanic and posttetanic potentiation and depression in responses of ipsilateral and contralateral motoneurons was observed, which would suggest the modulatory role of LB in short-term synaptic plasticity formation. Generally, LB fruit is able to modulate central nervous system reorganization, amplifying positive adaptive changes that improve functional recovery and promote selective target reinnervation in high fructose-diet rats with sciatic nerve crush-injury.

Glycation vs. glycosylation: a tale of two different chemistries and biology in Alzheimer's disease

In our previous studies, we reported that the activity of an anti-oxidant enzyme, Cu,Zn-superoxide dismutase (Cu,Zn-SOD) became decreased as the result of glycation in vitro and in vivo. Glycated Cu,Zn-SOD produces hydroxyl radicals in the presence of transition metals due to the formation of a Schiff base adduct and a subsequent Amadori product. This results in the site-specific cleavage of the molecule, followed by random fragmentation. The glycation of other anti-oxidant enzymes such as glutathione peroxidase and thioredoxin reductase results in a loss or decrease in enzyme activity under pathological conditions, resulting in oxidative stress. The inactivation of anti-oxidant enzymes induces oxidative stress in aging, diabetes and neurodegenerative disorders. It is well known that the levels of Amadori products and N(e)-(carboxylmethyl)lysine (CML) and other carbonyl compounds are increased in diabetes, a situation that will be discussed by the other authors in this special issue. We and others, reported that the glycation products accumulate in the brains of patients with Alzheimer's disease (AD) patients as well as in cerebrospinal fluid (CSF), suggesting that glycation plays a pivotal role in the development of AD. We also showed that enzymatic glycosylation is implicated in the pathogenesis of AD and that oxidative stress is also important in this process. Specific types of glycosylation reactions were found to be up- or downregulated in AD patients, and key AD-related molecules including the amyloid-precursor protein (APP), tau, and APP-cleaving enzymes were shown to be functionally modified as the result of glycosylation. These results suggest that glycation as well as glycosylation are involved in oxidative stress that is associated with aging, diabetes and neurodegenerative diseases such as AD.

Seeking homeostasis: temporal trends in respiration, oxidation, and calcium in SOD1 G93A Amyotrophic Lateral Sclerosis mice

Impairments in mitochondria, oxidative regulation, and calcium homeostasis have been well documented in numerous Amyotrophic Lateral Sclerosis (ALS) experimental models, especially in the superoxide dismutase 1 glycine 93 to alanine (SOD1 G93A) transgenic mouse. However, the timing of these deficiencies has been debatable. In a systematic review of 45 articles, we examine experimental measurements of cellular respiration, mitochondrial mechanisms, oxidative markers, and calcium regulation. We evaluate the quantitative magnitude and statistical temporal trend of these aggregated assessments in high transgene copy SOD1 G93A mice compared to wild type mice. Analysis of overall trends reveals cellular respiration, intracellular adenosine triphosphate, and corresponding mitochondrial elements (Cox, cytochrome c, complex I, enzyme activity) are depressed for the entire lifespan of the SOD1 G93A mouse. Oxidant markers (H2O2, 8OH2'dG, MDA) are initially similar to wild type but are double that of wild type by the time of symptom onset despite early post-natal elevation of protective heat shock proteins. All aspects of calcium regulation show early disturbances, although a notable and likely compensatory convergence to near wild type levels appears to occur between 40 and 80 days (pre-onset), followed by a post-onset elevation in intracellular calcium. The identified temporal trends and compensatory fluctuations provide evidence that the "cause" of ALS may lay within failed homeostatic regulation, itself, rather than any one particular perturbing event or cellular mechanism. We discuss the vulnerabilities of motoneurons to regulatory instability and possible hypotheses regarding failed regulation and its potential treatment in ALS.

The role of advanced glycation end products in various types of neurodegenerative disease: a therapeutic approach

Protein glycation is initiated by a nucleophilic addition reaction between the free amino group from a protein, lipid or nucleic acid and the carbonyl group of a reducing sugar. This reaction forms a reversible Schiff base, which rearranges over a period of days to produce ketoamine or Amadori products. The Amadori products undergo dehydration and rearrangements and develop a cross-link between adjacent proteins, giving rise to protein aggregation or advanced glycation end products (AGEs). A number of studies have shown that glycation induces the formation of the β-sheet structure in β-amyloid protein, α-synuclein, transthyretin (TTR), copper-zinc superoxide dismutase 1 (Cu, Zn-SOD-1), and prion protein. Aggregation of the β-sheet structure in each case creates fibrillar structures, respectively causing Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, familial amyloid polyneuropathy, and prion disease. It has been suggested that oligomeric species of glycated α-synuclein and prion are more toxic than fibrils. This review focuses on the pathway of AGE formation, the synthesis of different types of AGE, and the molecular mechanisms by which glycation causes various types of neurodegenerative disease. It discusses several new therapeutic approaches that have been applied to treat these devastating disorders, including the use of various synthetic and naturally occurring inhibitors. Modulation of the AGE-RAGE axis is now considered promising in the prevention of neurodegenerative diseases. Additionally, the review covers several defense enzymes and proteins in the human body that are important anti-glycating systems acting to prevent the development of neurodegenerative diseases.

Reactive carbonyl species in vivo: generation and dual biological effects

Reactive carbonyls are widespread species in living organisms and mainly known for their damaging effects. The most abundant reactive carbonyl species (RCS) are derived from oxidation of carbohydrates, lipids, and amino acids. Chemical modification of proteins, nucleic acids, and aminophospholipids by RCS results in cytotoxicity and mutagenicity. In addition to their direct toxicity, modification of biomolecules by RCS gives rise to a multitude of adducts and cross links that are increasingly implicated in aging and pathology of a wide range of human diseases. Understanding of the relationship between metabolism of RCS and the development of pathological disorders and diseases may help to develop effective approaches to prevent a number of disorders and diseases. On the other hand, constant persistence of RCS in cells suggests that they perform some useful role in living organisms. The most beneficial effects of RCS are their establishment as regulators of cell signal transduction and gene expression. Since RCS can modulate different biological processes, new tools are required to decipher the precise mechanisms underlying dual effects of RCS.

Fructation in vivo: detrimental and protective effects of fructose

There is compelling evidence that long-term intake of excessive fructose can have deleterious side effects in different experimental models. However, the role of fructose in vivo remains controversial, since acute temporary application of fructose is found to protect yeast as well as animal tissues against exogenous oxidative stress. This review suggests the involvement of reactive carbonyl and oxygen species in both the cytotoxic and defensive effects of fructose. Potential mechanisms of the generation of reactive species by fructose in the nonenzymatic reactions, their implication in the detrimental and protective effects of fructose are discussed.

Hyperglycemia and glycation in diabetic complications

Diabetes mellitus is a multifactorial disease, classically influenced by genetic determinants of individual susceptibility and by environmental accelerating factors, such as lifestyle. It is considered a major health concern,as its incidence is increasing at an alarming rate, and the high invalidating effects of its long-term complications affect macro- and microvasculature, heart, kidney, eye, and nerves. Increasing evidence indicates that hyperglycemia is the initiating cause of the tissue damage occurring in diabetes, either through repeated acute changes in cellular glucose metabolism, or through the long-term accumulation of glycated biomolecules and advanced glycation end products (AGEs). AGEs represent a heterogeneous group of chemical products resulting from a nonenzymatic reaction between reducing sugars and proteins, lipids, nucleic acids, or a combination of these.The glycation process (glucose fixation) affects circulating proteins (serum albumin, lipoprotein, insulin, hemoglobin),whereas the formation of AGEs implicates reactive intermediates such as methylglyoxal. AGEs form cross-links on long-lived extracellular matrix proteins or react with their specific receptor RAGE, resulting inoxidative stress and proinflammatory signaling implicated in endothelium dysfunction, arterial stiffening, and microvascular complications. This review summarizes the mechanism of glycation and of AGEs formation and the role of hyperglycemia, AGEs, and oxidative stress in the pathophysiology of diabetic complications.

Amyotrophic lateral sclerosis: from current developments in the laboratory to clinical implications

Amyotrophic lateral sclerosis (ALS) is a late-onset progressive degeneration of motor neurons occurring both as a sporadic and a familial disease. The etiology of ALS remains unknown, but one fifth of instances are due to specific gene defects, the best characterized of which is point mutations in the gene coding for Cu/Zn superoxide dismutase (SOD1). Because sporadic and familial ALS affect the same neurons with similar pathology, it is hoped that understanding these gene defects will help in devising therapies effective in both forms. A wealth of evidence has been collected in rodents made transgenic for mutant SOD1, which represent the best available models for familial ALS. Mutant SOD1 likely induces selective vulnerability of motor neurons through a combination of several mechanisms, including protein misfolding, mitochondrial dysfunction, oxidative damage, cytoskeletal abnormalities and defective axonal transport, excitotoxicity, inadequate growth factor signaling, and inflammation. Damage within motor neurons is enhanced by noxious signals originating from nonneuronal neighboring cells, where mutant SOD1 induces an inflammatory response that accelerates disease progression. The clinical implication of these findings is that promising therapeutic approaches can be derived from multidrug treatments aimed at the simultaneous interception of damage in both motor neurons and nonmotor neuronal cells.

Oxidized/misfolded superoxide dismutase-1: the cause of all amyotrophic lateral sclerosis?

The identification in 1993 of superoxide dismutase-1 (SOD1) mutations as the cause of 10 to 20% of familial amyotrophic lateral sclerosis cases, which represents 1 to 2% of all amyotrophic lateral sclerosis (ALS) cases, prompted a substantial amount of research into the mechanisms of SOD1-mediated toxicity. Recent experiments have demonstrated that oxidation of wild-type SOD1 leads to its misfolding, causing it to gain many of the same toxic properties as mutant SOD1. In vitro studies of oxidized/misfolded SOD1 and in vivo studies of misfolded SOD1 have indicated that these protein species are selectively toxic to motor neurons, suggesting that oxidized/misfolded SOD1 could lead to ALS even in individuals who do not carry an SOD1 mutation. It has also been reported that glial cells secrete oxidized/misfolded mutant SOD1 to the extracellular environment, where it can trigger the selective death of motor neurons, offering a possible explanation for the noncell autonomous nature of mutant SOD1 toxicity and the rapid progression of disease once the first symptoms develop. Therefore, considering that sporadic (SALS) and familial ALS (FALS) cases are clinically indistinguishable, the toxic properties of mutated SOD1 are similar to that of oxidized/misfolded wild-type SOD1 (wtSOD1), and secreted/extracellular misfolded SOD1 is selectively toxic to motor neurons, we propose that oxidized/misfolded SOD1 is the cause of most forms of classic ALS and should be a prime target for the design of ALS treatments.

Different Immunoreactivity against Monoclonal Antibodies between Wild-type and Mutant Copper/Zinc Superoxide Dismutase Linked to Amyotrophic Lateral Sclerosis

Although more than 100 mutations have been identified in the copper/zinc superoxide dismutase (Cu/Zn-SOD) in familial amyotrophic lateral sclerosis (FALS), the mechanism responsible for FALS remains unclear. The finding of the present study shows that FALS-causing mutant Cu/Zn-SOD proteins (FALS mutant SODs), but not wild-type SOD, are barely detected by three monoclonal antibodies (mAbs) in Western blot analyses. The enzyme-linked immunosorbent assay for denatured FALS mutant SODs by dithiothreitol, SDS, or heat treatment also showed a lowered immunoreactivity against the mAbs compared with wild-type SOD. Because all the epitopes of these mAbs are mapped within the Greek key loop (residues 102-115 in human Cu/Zn-SOD), these data suggest that different conformational changes occur in the loop between wild-type and FALS mutant SODs during the unfolding process. Circular dichroism measurements revealed that the FALS mutant SODs are sensitive to denaturation by dithiothreitol, SDS, or heat treatment, but these results do not completely explain the different recognition by the mAbs between wild-type and FALS mutant SODs under the denatured conditions. The study on the conformational changes in local areas monitoring with mAbs may provide a new insight into the etiology of FALS.

Overexpression of mutated Cu,Zn-SOD in neuroblastoma cells results in cytoskeletal change

Amyotrophic lateral sclerosis (ALS) involves the progressive degeneration of motor neurons in the spinal cord and the motor cortex. It has been shown that 15–20% of patients with familial ALS (FALS) have defects in the Sod1 gene, which encodes Cu,Zn-superoxide dismutase (SOD). To elucidate the pathological role of mutated Cu,Zn-SOD, we examined the issue of whether mutated Cu,Zn-SOD affects the cell cycle. Mouse neuroblastoma Neuro-2a cells were transfected with human wild-type or mutated (G37R, G93A) Cu,Zn-SOD. Mutated, Cu,Zn-SOD-transfected cells exhibited marked retardation in cell growth and G2/M arrest. They also displayed lower reactivity to phalloidin, indicating that the cytoskeleton was disrupted. Immunoprecipitation, two-dimensional gel electrophoresis, and Western blot analysis indicated that mutated Cu,Zn-SOD associates with actin. Similar results were obtained by in vitro incubation experiments with purified actin and mutated Cu,Zn-SOD (G93A). These results suggest that mutated Cu,Zn-SOD in FALS causes cytoskeletal changes by associating with actin, which subsequently causes G2/M arrest and growth retardation.