Therapeutic effects of immunization with mutant superoxide dismutase in mice models of amyotrophic lateral sclerosis

Hypothermia Shifts Neurodegeneration Phenotype in Neonatal Human Hypoxic-Ischemic Encephalopathy but Not in Related Piglet Models: Possible Relationship to Toxic Conformer and Intrinsically Disordered Prion-like Protein Accumulation

Hypothermia (HT) is used clinically for neonatal hypoxic-ischemic encephalopathy (HIE); however, the brain protection is incomplete and selective regional vulnerability and lifelong consequences remain. Refractory damage and impairment with HT cooling/rewarming could result from unchecked or altered persisting cell death and proteinopathy. We tested two hypotheses: (1) HT modifies neurodegeneration type, and (2) intrinsically disordered proteins (IDPs) and encephalopathy cause toxic conformer protein (TCP) proteinopathy neonatally. We studied postmortem human neonatal HIE cases with or without therapeutic HT, neonatal piglets subjected to global hypoxia-ischemia (HI) with and without HT or combinations of HI and quinolinic acid (QA) excitotoxicity surviving for 29-96 h to 14 days, and human oligodendrocytes and neurons exposed to QA for cell models. In human and piglet encephalopathies with normothermia, the neuropathology by hematoxylin and eosin staining was similar; necrotic cell degeneration predominated. With HT, neurodegeneration morphology shifted to apoptosis-necrosis hybrid and apoptotic forms in human HIE, while neurons in HI piglets were unshifting and protected robustly. Oligomers and putative TCPs of α-synuclein (αSyn), nitrated-Syn and aggregated αSyn, misfolded/oxidized superoxide dismutase-1 (SOD1), and prion protein (PrP) were detected with highly specific antibodies by immunohistochemistry, immunofluorescence, and immunoblotting. αSyn and SOD1 TCPs were seen in human HIE brains regardless of HT treatment. αSyn and SOD1 TCPs were detected as early as 29 h after injury in piglets and QA-injured human oligodendrocytes and neurons in culture. Cell immunophenotyping by immunofluorescence showed αSyn detected with antibodies to aggregated/oligomerized protein; nitrated-Syn accumulated in neurons, sometimes appearing as focal dendritic aggregations. Co-localization also showed aberrant αSyn accumulating in presynaptic terminals. Proteinase K-resistant PrP accumulated in ischemic Purkinje cells, and their target regions had PrP-positive neuritic plaque-like pathology. Immunofluorescence revealed misfolded/oxidized SOD1 in neurons, axons, astrocytes, and oligodendrocytes. HT attenuated TCP formation in piglets. We conclude that HT differentially affects brain damage in humans and piglets. HT shifts neuronal cell death to other forms in human while blocking ischemic necrosis in piglet for sustained protection. HI and excitotoxicity also acutely induce formation of TCPs and prion-like proteins from IDPs globally throughout the brain in gray matter and white matter. HT attenuates proteinopathy in piglets but seemingly not in humans. Shifting of cell death type and aberrant toxic protein formation could explain the selective system vulnerability, connectome spreading, and persistent damage seen in neonatal HIE leading to lifelong consequences even after HT treatment.

Amyotrophic lateral sclerosis caused by SOD1 variants: from genetic discovery to disease prevention

Pathogenic variants in the superoxide dismutase 1 (SOD1) gene were the first identified genetic cause of amyotrophic lateral sclerosis (ALS), in 1993. This discovery enabled the development of transgenic rodent models for studying the biology of SOD1 ALS. The understanding that SOD1 ALS is driven by a toxic gain-of-function mutation has led to therapeutic strategies that aim to lower concentrations of SOD1 protein, an endeavour that has been complicated by the phenotypic heterogeneity of SOD1 ALS. The successful development of genetically targeted therapies to reduce SOD1 expression, together with a better understanding of pre-symptomatic disease and the discovery of neurofilament light protein as a susceptibility/risk biomarker that predicts phenoconversion, has ushered in a new era of trials that aim to prevent clinically manifest SOD1 ALS. The 30-year journey from gene discovery to gene therapy has not only uncovered the pathophysiology of SOD1 ALS, but has also facilitated the development of biomarkers that should aid therapy development for all forms of ALS.

Disulfide-mediated oligomerization of mutant Cu/Zn-superoxide dismutase associated with canine degenerative myelopathy

A homozygous E40K mutation in the gene coding canine Cu/Zn-superoxide dismutase (cSOD1) causes degenerative myelopathy (DM) in dogs. A pathological hallmark of DM with the cSOD1 mutation is the aggregation of mutant cSOD1 proteins in neurons. The amino acid substitution E40K disrupts a salt bridge between Glu40 and Lys91 and is considered to destabilize the native state of cSOD1; however, the mechanism by which mutant cSOD1 aggregates remains unclear. Here, we show that mutant cSOD1 losing a copper and zinc ion forms oligomers crosslinked via disulfide bonds. The E40K substitution was found to result in the increased solvent exposure of the Cys7 side chain, which then attacked the disulfide bond (Cys57-Cys146) in cSOD1 to form disulfide-linked oligomers. We also successfully prevented the Cys7 exposure and thus the oligomerization of mutant cSOD1 by a fragment antibody that specifically recognizes the region around the mutation site. The fragment antibody covered the β-plug region, reinforcing the interactions compromised by the E40K substitution and thus contributing to the maintenance of the structural integrity of the β-barrel core of cSOD1. Taken together, we propose that the Cys7 exposure in cSOD1 upon the salt bridge disruption plays a central role in the aggregation mechanism of DM-associated mutant cSOD1.

Ebselen analogues delay disease onset and its course in fALS by on-target SOD-1 engagement

Amyotrophic lateral sclerosis (ALS) selectively affects motor neurons. SOD1 is the first causative gene to be identified for ALS and accounts for at least 20% of the familial (fALS) and up to 4% of sporadic (sALS) cases globally with some geographical variability. The destabilisation of the SOD1 dimer is a key driving force in fALS and sALS. Protein aggregation resulting from the destabilised SOD1 is arrested by the clinical drug ebselen and its analogues (MR6-8-2 and MR6-26-2) by redeeming the stability of the SOD1 dimer. The in vitro target engagement of these compounds is demonstrated using the bimolecular fluorescence complementation assay with protein-ligand binding directly visualised by co-crystallography in G93A SOD1. MR6-26-2 offers neuroprotection slowing disease onset of SOD1G93A mice by approximately 15 days. It also protected neuromuscular junction from muscle denervation in SOD1G93A mice clearly indicating functional improvement.

MS785-MS27 Reactive Misfolded/Non-Native Zn-Deficient SOD1 Species Exhibit Cytotoxicity and Adopt Heterozygous Conformations in Motor Neurons

Misfolding of superoxide dismutase-1 (SOD1) is a pathological hallmark of amyotrophic lateral sclerosis (ALS) with SOD1 mutations. The development of antibodies specific for misfolded SOD1 deepens our understanding of how the protein participates in ALS pathogenesis. Since the term "misfolding" refers to various disordered conformers other than the natively folded one, which misfolded species are recognized by specific antibodies should be determined. Here, we molecularly characterized the recognition by MS785-MS27, an antibody cocktail experimentally confirmed to recognize over 100 ALS-linked SOD1 mutants. Indirect ELISA revealed that the antibody cocktail recognized Zn-deficient wild-type and mutated SOD1 species. It also recognized conformation-disordered wild-type and mutated SOD1 species, such as unfolded and oligomeric forms, but had less affinity for the aggregated form. Antibody-reactive SOD1 exhibited cytotoxicity to a motor neuron cell model, which was blocked by Zn treatment with Zn-deficient SOD1. Immunohistochemistry revealed antibody-reactive SOD1 mainly in spinal motor neurons of SOD1G93A mice throughout the disease course, and the distribution after symptomatic stages differed from that of other misfolded SOD1 species. This suggests that misfolded/non-native SOD1 species exist as heterogeneous populations. In conclusion, MS785-MS27 recognizes various conformation-disordered SOD1 species lacking the Zn ion.

Blocking an epitope of misfolded SOD1 ameliorates disease phenotype in a model of amyotrophic lateral sclerosis

The current strategies to mitigate the toxicity of misfolded superoxide dismutase 1 (SOD1) in familial amyotrophic lateral sclerosis via blocking SOD1 expression in the CNS are indiscriminative for misfolded and intact proteins, and as such, entail a risk of depriving CNS cells of their essential antioxidant potential. As an alternative approach to neutralize misfolded and spare unaffected SOD1 species, we developed scFv-SE21 antibody that blocks the β6/β7 loop epitope exposed exclusively in misfolded SOD1. The β6/β7 loop epitope has previously been proposed to initiate amyloid-like aggregation of misfolded SOD1 and mediate its prion-like activity. The adeno-associated virus-mediated expression of scFv-SE21 in the CNS of hSOD1G37R mice rescued spinal motor neurons, reduced the accumulation of misfolded SOD1, decreased gliosis and thus delayed disease onset and extended survival by 90 days. The results provide evidence for the role of the exposed β6/β7 loop epitope in the mechanism of neurotoxic gain-of-function of misfolded SOD1 and open avenues for the development of mechanism-based anti-SOD1 therapeutics, whose selective targeting of misfolded SOD1 species may entail a reduced risk of collateral oxidative damage to the CNS.

Selective removal of misfolded SOD1 delays disease onset in a mouse model of amyotrophic lateral sclerosis

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease. There is no cure currently. The discovery that mutations in the gene SOD1 are a cause of ALS marks a breakthrough in the search for effective treatments for ALS. SOD1 is an antioxidant that is highly expressed in motor neurons. Human SOD1 is prone to aberrant modifications. Familial ALS-linked SOD1 variants are particularly susceptible to aberrant modifications. Once modified, SOD1 undergoes conformational changes and becomes misfolded. This study aims to determine the effect of selective removal of misfolded SOD1 on the pathogenesis of ALS.

METHODS

Based on the chaperone-mediated protein degradation pathway, we designed a fusion peptide named CT4 and tested its efficiency in knocking down intracellularly misfolded SOD1 and its efficacy in modifying the pathogenesis of ALS.

RESULTS

Expression of the plasmid carrying the CT4 sequence in human HEK cells resulted in robust removal of misfolded SOD1 induced by serum deprivation. Co-transfection of the CT4 and the G93A-hSOD1 plasmids at various ratios demonstrated a dose-dependent knockdown efficiency on G93A-hSOD1, which could be further increased when misfolding of SOD1 was enhanced by serum deprivation. Application of the full-length CT4 peptide to primary cultures of neurons expressing the G93A variant of human SOD1 revealed a time course of the degradation of misfolded SOD1; misfolded SOD1 started to decrease by 2 h after the application of CT4 and disappeared by 7 h. Intravenous administration of the CT4 peptide at 10 mg/kg to the G93A-hSOD1 reduced human SOD1 in spinal cord tissue by 68% in 24 h and 54% in 48 h in presymptomatic ALS mice. Intraperitoneal administration of the CT4 peptide starting from 60 days of age significantly delayed the onset of ALS and prolonged the lifespan of the G93A-hSOD1 mice.

CONCLUSIONS

The CT4 peptide directs the degradation of misfolded SOD1 in high efficiency and specificity. Selective removal of misfolded SOD1 significantly delays the onset of ALS, demonstrating that misfolded SOD1 is the toxic form of SOD1 that causes motor neuron death. The study proves that selective removal of misfolded SOD1 is a promising treatment for ALS.

Intercellular transmission of pathogenic proteins in ALS: Exploring the pathogenic wave

In patients with amyotrophic lateral sclerosis (ALS), disease symptoms and pathology typically spread in a predictable spatiotemporal pattern beginning at a focal site of onset and progressing along defined neuroanatomical tracts. Like other neurodegenerative diseases, ALS is characterized by the presence of protein aggregates in postmortem patient tissue. Cytoplasmic, ubiquitin-positive aggregates of TDP-43 are observed in approximately 97% of sporadic and familial ALS patients, while SOD1 inclusions are likely specific to cases of SOD1-ALS. Additionally, the most common subtype of familial ALS, caused by a hexanucleotide repeat expansion in the first intron of the C9orf72 gene (C9-ALS), is further characterized by the presence of aggregated dipeptide repeat proteins (DPRs). As we will describe, cell-to-cell propagation of these pathological proteins tightly correlates with the contiguous spread of disease. While TDP-43 and SOD1 are capable of seeding protein misfolding and aggregation in a prion-like manner, C9orf72 DPRs appear to induce (and transmit) a 'disease state' more generally. Multiple mechanisms of intercellular transport have been described for all of these proteins, including anterograde and retrograde axonal transport, extracellular vesicle secretion, and macropinocytosis. In addition to neuron-to-neuron transmission, transmission of pathological proteins occurs between neurons and glia. Given that the spread of ALS disease pathology corresponds with the spread of symptoms in patients, the various mechanisms by which ALS-associated protein aggregates propagate through the central nervous system should be closely examined.

Efficacy of oligodendrocyte precursor cells as delivery vehicles for single-chain variable fragment to misfolded SOD1 in ALS rat model

Superoxide dismutase1 (SOD 1) mutation is a leading cause of familial amyotrophic lateral sclerosis (ALS). Growing evidence suggests that antibody therapy against misfolded SOD1 protein can be therapeutic. However, the therapeutic effects are limited, partly because of the delivery system. Therefore, we investigated the efficacy of oligodendrocyte precursor cells (OPCs) as a drug delivery vehicle of single-chain variable fragments (scFv). Using a Borna disease virus vector that is pharmacologically removable and episomally replicable in the recipient cells, we successfully transformed wild-type OPCs to secrete scFv of a novel monoclonal antibody (D3-1), specific for misfolded SOD1. Single intrathecal injection of OPCs scFvD3-1, but not OPCs alone, significantly delayed disease onset and prolonged the lifespan of ALS rat models expressing SOD1 ^H46R . The effect of OPC scFvD3-1 surpassed that of a 1 month intrathecal infusion of full-length D3-1 antibody alone. scFv-secreting OPCs suppressed neuronal loss and gliosis, reduced levels of misfolded SOD1 in the spinal cord, and suppressed the transcription of inflammatory genes, including Olr1, an oxidized low-density lipoprotein receptor 1. The use of OPCs as a delivery vehicle for therapeutic antibodies is a new option for ALS in which misfolded protein and oligodendrocyte dysfunction are implicated in the pathogenesis.

The Neuroprotective Activities of the Novel Multi-Target Iron-Chelators in Models of Alzheimer's Disease, Amyotrophic Lateral Sclerosis and Aging

The concept of chelation therapy as a valuable therapeutic approach in neurological disorders led us to develop multi-target, non-toxic, lipophilic, brain-permeable compounds with iron chelation and anti-apoptotic properties for neurodegenerative diseases, such as Parkinson's disease (PD), Alzheimer's disease (AD), age-related dementia and amyotrophic lateral sclerosis (ALS). Herein, we reviewed our two most effective such compounds, M30 and HLA20, based on a multimodal drug design paradigm. The compounds have been tested for their mechanisms of action using animal and cellular models such as APP/PS1 AD transgenic (Tg) mice, G93A-SOD1 mutant ALS Tg mice, C57BL/6 mice, Neuroblastoma × Spinal Cord-34 (NSC-34) hybrid cells, a battery of behavior tests, and various immunohistochemical and biochemical techniques. These novel iron chelators exhibit neuroprotective activities by attenuating relevant neurodegenerative pathology, promoting positive behavior changes, and up-regulating neuroprotective signaling pathways. Taken together, these results suggest that our multifunctional iron-chelating compounds can upregulate several neuroprotective-adaptive mechanisms and pro-survival signaling pathways in the brain and might function as ideal drugs for neurodegenerative disorders, such as PD, AD, ALS, and aging-related cognitive decline, in which oxidative stress and iron-mediated toxicity and dysregulation of iron homeostasis have been implicated.

Therapeutic tools for familial ALS

Familial ALS (FALS) accounts for 10 to 15% of ALS cases. In more than 70% of FALS patients, a causal gene is identified and animal models have been developed for a subset of them, mainly for the most frequently mutated genes. Therapeutic tools to treat those patients are dominated by gene-specific therapy and the most advanced approaches target the SOD1 gene mutations. Either by direct delivery of antisense oligonucleotides (ASO) or using viral vectors such as adenoviruses (AAV) to deliver ASOs, gene specific therapies have shown promising results in animal models. The recent use of subpial injections of AAV9+anti SOD1 ASO now shows that the disease is completely prevented or stopped in the animal, depending on the moment of injection, e.g., before or after disease onset. However, the use of viral vectors in humans seems to be limited at least by their immunogenicity. Antibody-based therapies are also efficient to treat animal models, but to a lesser extent. Most of the experiments targeted the SOD1 protein in its misfolded conformation. This approach seems better tolerated than the AAV one, an important limit being the choice of the epitope. Unexpectedly, some advances in treating the C9ORF72 animal model have been obtained using a modulation of microbiota, and this strategy has the great advantage to have an easy route of administration and a good safety profile. The landscape of experimental FALS treatment is rapidly evolving and results are promising. This is an important unmet need for ALS patients and several human phase I, II and III trials are ongoing.

Anti-SOD1 Nanobodies That Stabilize Misfolded SOD1 Proteins Also Promote Neurite Outgrowth in Mutant SOD1 Human Neurons

ALS-linked mutations induce aberrant conformations within the SOD1 protein that are thought to underlie the pathogenic mechanism of SOD1-mediated ALS. Although clinical trials are underway for gene silencing of SOD1, these approaches reduce both wild-type and mutated forms of SOD1. Here, we sought to develop anti-SOD1 nanobodies with selectivity for mutant and misfolded forms of human SOD1 over wild-type SOD1. Characterization of two anti-SOD1 nanobodies revealed that these biologics stabilize mutant SOD1 in vitro. Further, SOD1 expression levels were enhanced and the physiological subcellular localization of mutant SOD1 was restored upon co-expression of anti-SOD1 nanobodies in immortalized cells. In human motor neurons harboring the SOD1 A4V mutation, anti-SOD1 nanobody expression promoted neurite outgrowth, demonstrating a protective effect of anti-SOD1 nanobodies in otherwise unhealthy cells. In vitro assays revealed that an anti-SOD1 nanobody exhibited selectivity for human mutant SOD1 over endogenous murine SOD1, thus supporting the preclinical utility of anti-SOD1 nanobodies for testing in animal models of ALS. In sum, the anti-SOD1 nanobodies developed and presented herein represent viable biologics for further preclinical testing in human and mouse models of ALS.

Protein citrullination marks myelin protein aggregation and disease progression in mouse ALS models

Increased protein citrullination (PC) and dysregulated protein arginine deiminase (PAD) activity have been observed in several neurodegenerative diseases. PC is a posttranslational modification catalyzed by the PADs. PC converts peptidyl-arginine to peptidyl-citrulline, thereby reducing the positive charges and altering structure and function of proteins. Of the five PADs, PAD2 is the dominant isoform in the central nervous system (CNS). Abnormal PC and PAD dysregulation are associated with numerous pathological conditions, including inflammatory diseases and neurodegeneration. Animal model studies have shown therapeutic efficacy from inhibition of PADs, thus suggesting a role of PC in pathogenesis. To determine whether PC contribute to amyotrophic lateral sclerosis (ALS), a deadly neurodegenerative disease characterized by loss of motor neurons, paralysis, and eventual death, we investigated alterations of PC and PAD2 in two different transgenic mouse models of ALS expressing human mutant SOD1^G93A and PFN1^C71G, respectively. PC and PAD2 expression are altered dynamically in the spinal cord during disease progression in both models. PC and PAD2 increase progressively in astrocytes with the development of reactive astrogliosis, while decreasing in neurons. Importantly, in the spinal cord white matter, PC accumulates in protein aggregates that contain the myelin proteins PLP and MBP. PC also accumulates progressively in insoluble protein fractions during disease progression. Finally, increased PC and PAD2 expression spatially correlate with areas of the CNS with the most severe motor neuron degeneration. These results suggest that altered PC is an integral part of the neurodegenerative process and potential biomarkers for disease progression in ALS. Moreover, increased PC may contribute to disease-associated processes such as myelin protein aggregation, myelin degeneration, and astrogliosis.

Prionoids in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the third most frequent neurodegenerative disease after Alzheimer’s and Parkinson’s disease. ALS is characterized by the selective and progressive loss of motoneurons in the spinal cord, brainstem and cerebral cortex. Clinical manifestations typically occur in midlife and start with focal muscle weakness, followed by the rapid and progressive wasting of muscles and subsequent paralysis. As with other neurodegenerative diseases, the condition typically begins at an initial point and then spreads along neuroanatomical tracts. This feature of disease progression suggests the spreading of prion-like proteins called prionoids in the affected tissues, which is similar to the spread of prion observed in Creutzfeldt-Jakob disease. Intensive research over the last decade has proposed the ALS-causing gene products Cu/Zn superoxide dismutase 1, TAR DNA-binding protein of 43 kDa, and fused in sarcoma as very plausible prionoids contributing to the spread of the pathology. In this review, we will discuss the molecular and cellular mechanisms leading to the propagation of these prionoids in ALS.

Accumulation of misfolded SOD1 outlines distinct patterns of motor neuron pathology and death during disease progression in a SOD1G93A mouse model of amyotrophic lateral sclerosis

Early misfolded superoxide dismutase 1 (mfSOD1) accumulation, motor neuron (MN) degeneration, and microgliosis are hallmark pathological features in SOD1^G93A amyotrophic lateral sclerosis (ALS) mice. Because of the different vulnerabilities of distinct MN subtypes, degenerating and surviving MNs coexist in different proportions during disease progression. By examining the expression of misfolded conformers of SOD1 using specific antibodies, we defined distinct MN phenotypes that were evaluated during disease progression and the local neuroinflammatory reaction. The most severe phenotype corresponded to somata of fast‐twitch subtype MNs, which exhibited highly positive mfSOD1 immunostaining and an extreme degree of vacuolar degeneration. Vacuoles, which are of mitochondrial origin, contain mfSOD1 in conjunction with nonmitochondrial proteins, such as chromogranin, CD81, and flotillin. The fusion of ER‐derived vesicles enriched in mfSOD1 with outer mitochondrial membranes is thought to be the primary mechanism for vacuole formation. In addition, the ulterior coalescence of enlarged mitochondria may lead to the formation of giant vacuoles. Vacuolar degeneration is a transient degenerative process occurring early during the presymptomatic stages of the disease in ALS mice. Some vacuolated MNs are also positive for pMLKL, the effector protein of necroptosis. This indicates a newly described mechanism in which extracellular vesicles derived from damaged MNs, via cellular secretion or necroptotic disruption, may be the triggers for initiating neuroinflammation, glial‐mediated neurotoxicity, and disease spreading. Furthermore, as MN degeneration in mutant SOD1 mice is noncell autonomous, the effects of experimentally increasing or decreasing the microglial response on the expression of MN phenotypes were also evaluated, demonstrating bidirectional cross talk signaling between the degree of expression of mfSOD1 and local neuroinflammation. More detailed knowledge regarding these processes occurring long before the end stages of the disease is necessary to identify novel molecular targets for future preclinical testing.

TDP-43 stabilizes G3BP1 mRNA: relevance to amyotrophic lateral sclerosis/frontotemporal dementia

TDP-43 nuclear depletion and concurrent cytoplasmic accumulation in vulnerable neurons is a hallmark feature of progressive neurodegenerative proteinopathies such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Cellular stress signalling and stress granule dynamics are now recognized to play a role in ALS/FTD pathogenesis. Defective stress granule assembly is associated with increased cellular vulnerability and death. Ras-GAP SH3-domain-binding protein 1 (G3BP1) is a critical stress granule assembly factor. Here, we define that TDP-43 stabilizes G3BP1 transcripts via direct binding of a highly conserved cis regulatory element within the 3' untranslated region. Moreover, we show in vitro and in vivo that nuclear TDP-43 depletion is sufficient to reduce G3BP1 protein levels. Finally, we establish that G3BP1 transcripts are reduced in ALS/FTD patient neurons bearing TDP-43 cytoplasmic inclusions/nuclear depletion. Thus, our data indicate that, in ALS/FTD, there is a compromised stress granule response in disease-affected neurons due to impaired G3BP1 mRNA stability caused by TDP-43 nuclear depletion. These data implicate TDP-43 and G3BP1 loss of function as contributors to disease.

Antibody-Based Therapeutic Interventions for Amyotrophic Lateral Sclerosis: A Systematic Literature Review

Amyotrophic Lateral Sclerosis (ALS) is a mid-life onset neurodegenerative disease that manifests its symptomatology with motor impairments and cognitive deficits overlapping with Frontotemporal Lobar Degeneration (FTLD). The etiology of ALS remains elusive, with various mechanisms and cellular targets implicated, and no treatment can reverse or stop the progression of the pathology. Therapeutic interventions based on passive immunization are gaining attention for neurodegenerative diseases, and FDA recently approved the first antibody-based approach for Alzheimer's disease. The present systematic review of the literature aims to highlight the efforts made over the past years at developing antibody-based strategies to cure ALS. Thirty-one original research papers have been selected where the therapeutic efficacy of antibodies were investigated and described in patients and animal models of ALS. Antibody-based interventions analyzed, target both extracellular molecules implicated in the pathology and intracellular pathogenic proteins known to drive the disease, such as SOD1, TDP-43 or C9ORF72 repeats expansions. The potentials and limitations of these therapeutic interventions have been described and discussed in the present review.

Protein clearance strategies for disease intervention

Protein homeostasis, or proteostasis, is essential for cell function and viability. Unwanted, damaged, misfolded and aggregated proteins are degraded by the ubiquitin–proteasome system (UPS) and the autophagy-lysosome pathway. Growing evidence indicates that alterations in these major proteolytic mechanisms lead to a demise in proteostasis, contributing to the onset and development of distinct diseases. Indeed, dysregulation of the UPS or autophagy is linked to several neurodegenerative, infectious and inflammatory disorders as well as cancer. Thus, modulation of protein clearance pathways is a promising approach for therapeutics. In this review, we discuss recent findings and open questions on how targeting proteolytic mechanisms could be applied for disease intervention.

Immunotherapies for Neurodegenerative Diseases

The current treatments for neurodegenerative diseases are mostly symptomatic without affecting the underlying cause of disease. Emerging evidence supports a potential role for immunotherapy in the management of disease progression. Numerous reports raise the exciting prospect that either the immune system or its derivative components could be harnessed to fight the misfolded and aggregated proteins that accumulate in several neurodegenerative diseases. Passive and active vaccinations using monoclonal antibodies and specific antigens that induce adaptive immune responses are currently under evaluation for their potential use in the development of immunotherapies. In this review, we aim to shed light on prominent immunotherapeutic strategies being developed to fight neuroinflammation-induced neurodegeneration, with a focus on innovative immunotherapies such as vaccination therapy.

A Metal-Free, Disulfide Oxidized Form of Superoxide Dismutase 1 as a Primary Misfolded Species with Prion-Like Properties in the Extracellular Environments Surrounding Motor Neuron-Like Cells

Superoxide dismutase 1 (SOD1) is a metalloenzyme with high structural stability, but a lack of Cu and Zn ions decreases its stability and enhances the likelihood of misfolding, which is a pathological hallmark of amyotrophic lateral sclerosis (ALS). A growing body of evidence has demonstrated that misfolded SOD1 has prion-like properties such as transmissibility between cells and intracellular propagation of misfolding of natively folded SOD1. Recently, we found that SOD1 is misfolded in the cerebrospinal fluid of sporadic ALS patients, providing a route by which misfolded SOD1 spreads via the extracellular environment of the central nervous system. Unlike intracellular misfolded SOD1, it is unknown which extracellular misfolded species is most relevant to prion-like properties. Here, we determined a conformational feature of extracellular misfolded SOD1 that is linked to prion-like properties. Using culture media from motor neuron-like cells, NSC-34, extracellular misfolded wild-type, and four ALS-causing SOD1 mutants were characterized as a metal-free, disulfide oxidized form of SOD1 (apo-SOD1^S-S). Extracellular misfolded apo-SOD1^S-S exhibited cell-to-cell transmission from the culture medium to recipient cells as well as intracellular propagation of SOD1 misfolding in recipient cells. Furthermore, culture medium containing misfolded apo-SOD1^S-S exerted cytotoxicity to motor neuron-like cells, which was blocked by removal of misfolded apo-SOD1^S-S from the medium. We conclude that misfolded apo-SOD1^S-S is a primary extracellular species that is linked to prion-like properties.

Novel SOD1 monoclonal antibodies against the electrostatic loop preferentially detect misfolded SOD1 aggregates

Amyotrophic lateral sclerosis (ALS) is a progressive neurological disease that leads to motor neuron degeneration and paralysis. Superoxide dismutase (SOD1) mutations are the second most common cause of familial ALS and are responsible for up to 20 % of familial ALS cases. In ALS patients, SOD1 can form toxic misfolded aggregates that deposit in the brain and spinal cord. To better detect SOD1 aggregates and expand the repertoire of conformational SOD1 antibodies, SOD1 monoclonal antibodies were generated by immunizing SOD1 knockout mice with an SOD1 fragment consisting of amino acids 129-146, which make up part of the electrostatic loop. A series of hybridomas secreting antibodies were screened and five different SOD1 monoclonal antibodies (2C10, 2F8, 4B11, 5H5, and 5A10) were found to preferentially detect denatured or aggregated SOD1 by enzyme-linked immunosorbent assay (ELISA), filter trap assay, and immunohistochemical analysis in SOD1 mouse models. The staining with these antibodies was compared to Campbell-Switzer argyrophilic reactivity of pathological inclusions. These new conformational selective SOD1 antibodies will be useful for clinical diagnosis of SOD1 ALS and potentially for passive immunotherapy.

Recent advances in understanding amyotrophic lateral sclerosis and emerging therapies

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that is characterized by degeneration of both upper and lower motor neurons and subsequent progressive loss of muscle function. Within the last decade, significant progress has been made in the understanding of the etiology and pathobiology of the disease; however, treatment options remain limited and only two drugs, which exert a modest effect on survival, are approved for ALS treatment in the US. Therefore, the search for effective ALS therapies continues, and over 60 clinical trials are in progress for patients with ALS and other therapeutics are at the pre-clinical stage of development. Recent advances in understanding the genetics, pathology, and molecular mechanisms of ALS have led to the identification of novel targets and strategies that are being used in emerging ALS therapeutic interventions. Here, we review the current status and mechanisms of action of a selection of emerging ALS therapies in pre-clinical or early clinical development, including gene therapy, immunotherapy, and strategies that target neuroinflammation, phase separation, and protein clearance.

Monoclonal full-length antibody against TAR DNA binding protein 43 reduces related proteinopathy in neurons

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD), 2 incurable neurodegenerative disorders, share the same pathological hallmark named TDP43 (TAR DNA binding protein 43) proteinopathy. This event is characterized by a consistent cytoplasmic mislocalization and aggregation of the protein TDP43, which loses its physiological properties, leading neurons to death. Antibody-based approaches are now emerging interventions in the field of neurodegenerative disorders. Here, we tested the target specificity, in vivo distribution, and therapeutic efficacy of a monoclonal full-length antibody, named E6, in TDP43-related conditions. We observed that the antibody recognizes specifically the cytoplasmic fraction of TDP43. We demonstrated its ability in targeting large neurons in the spinal cord of mice and in reducing TDP43 mislocalization and NF-κB activation. We also recognized the proteasome as well as the lysosome machineries as possible mechanisms used by the antibody to reduce TDP43 proteinopathy. To our knowledge, this is the first report showing the therapeutic efficacy and feasibility of a full-length antibody against TDP43 in reducing TDP43 proteinopathy in spinal neurons of an ALS/FTLD mouse model.

A full-length antibody against TDP43 reduces TDP43 proteinopathy in spinal neurons of an amyotrophic lateral sclerosis/Frontotemporal lobar degeneration mouse model.

Trifluoroethanol Partially Unfolds G93A SOD1 Leading to Protein Aggregation: A Study by Native Mass Spectrometry and FPOP Protein Footprinting

Misfolding of Cu, Zn superoxide dismutase (SOD1) variants may lead to protein aggregation and ultimately amyotrophic lateral sclerosis (ALS). The mechanism and protein conformational changes during this process are complex and remain unclear. To study SOD1 variant aggregation at the molecular level and in solution, we chemically induced aggregation of a mutant variant (G93A SOD1) with trifluoroethanol (TFE) and used both native mass spectrometry (MS) to analyze the intact protein and fast photochemical oxidation of proteins (FPOP) to characterize the structural changes induced by TFE. We found partially unfolded G93A SOD1 monomers prior to oligomerization and identified regions of the N-terminus, C-terminus, and strands β5, β6 accountable for the partial unfolding. We propose that exposure of hydrophobic interfaces of these unstructured regions serves as a precursor to aggregation. Our results provide a possible mechanism and molecular basis for ALS-linked SOD1 misfolding and aggregation.

Aggregate-selective antibody attenuates seeded aggregation but not spontaneously evolving disease in SOD1 ALS model mice

Increasing evidence suggests that propagation of the motor neuron disease amyotrophic lateral sclerosis (ALS) involves the pathogenic aggregation of disease-associated proteins that spread in a prion-like manner. We have identified two aggregate strains of human superoxide dismutase 1 (hSOD1) that arise in the CNS of transgenic mouse models of SOD1-mediated ALS. Both strains transmit template-directed aggregation and premature fatal paralysis when inoculated into the spinal cord of adult hSOD1 transgenic mice. This spread of pathogenic aggregation could be a potential target for immunotherapeutic intervention. Here we generated mouse monoclonal antibodies (mAbs) directed to exposed epitopes in hSOD1 aggregate strains and identified an aggregate selective mAb that targets the aa 143-153 C-terminal extremity of hSOD1 (αSOD1^143-153). Both pre-incubation of seeds with αSOD1^143-153 prior to inoculation, and weekly intraperitoneal (i.p.) administration attenuated transmission of pathogenic aggregation and prolonged the survival of seed-inoculated hSOD1^G85R Tg mice. In contrast, administration of a mAb targeting aa 65-72 (αSOD1^65-72), which exhibits high affinity towards monomeric disordered hSOD1, had an adverse effect and aggravated seed induced premature ALS-like disease. Although the mAbs reached similar concentrations in CSF, only αSOD1^143-153 was found in association with aggregated hSOD1 in spinal cord homogenates. Our results suggest that an aggregate-selective immunotherapeutic approach may suppress seeded transmission of pathogenic aggregation in ALS. However, long-term administration of αSOD1^143-153 was unable to prolong the lifespan of non-inoculated hSOD1^G85R Tg mice. Thus, spontaneously initiated hSOD1 aggregation in spinal motor neurons may be poorly accessible to therapeutic antibodies.

Novel therapeutic targets for amyotrophic lateral sclerosis: ribonucleoproteins and cellular autonomy

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a devastating disease with a lifetime risk of approximately 1:400. It is incurable and invariably fatal. Average survival is between 3 and 5 years and patients become increasingly paralyzed, losing the ability to speak, eat, and breathe. Therapies in development either (i) target specific familial forms of ALS (comprising a minority of around 10% of cases) or ii) emanate from (over)reliance on animal models or non-human/non-neuronal cell models. There is a desperate and unmet clinical need for effective treatments. Deciphering the primacy and relative contributions of defective protein homeostasis and RNA metabolism in ALS across different model systems will facilitate the identification of putative therapeutic targets.

AREAS COVERED

This review examines the putative common primary molecular events that lead to ALS pathogenesis. We focus on deregulated RNA metabolism, protein mislocalization/pathological aggregation and the role of glia in ALS-related motor neuron degeneration. Finally, we describe promising targets for therapeutic evaluation.

EXPERT OPINION

Moving forward, an effective strategy could be achieved by a poly-therapeutic approach which targets both deregulated RNA metabolism and protein dyshomeostasis in the relevant cell types, at the appropriate phase of disease.

Does wild-type Cu/Zn-superoxide dismutase have pathogenic roles in amyotrophic lateral sclerosis?

Amyotrophic lateral sclerosis (ALS) is characterized by adult-onset progressive degeneration of upper and lower motor neurons. Increasing numbers of genes are found to be associated with ALS; among those, the first identified gene, SOD1 coding a Cu/Zn-superoxide dismutase protein (SOD1), has been regarded as the gold standard in the research on a pathomechanism of ALS. Abnormal accumulation of misfolded SOD1 in affected spinal motor neurons has been established as a pathological hallmark of ALS caused by mutations in SOD1 (SOD1-ALS). Nonetheless, involvement of wild-type SOD1 remains quite controversial in the pathology of ALS with no SOD1 mutations (non-SOD1 ALS), which occupies more than 90% of total ALS cases. In vitro studies have revealed post-translationally controlled misfolding and aggregation of wild-type as well as of mutant SOD1 proteins; therefore, SOD1 proteins could be a therapeutic target not only in SOD1-ALS but also in more prevailing cases, non-SOD1 ALS. In order to search for evidence on misfolding and aggregation of wild-type SOD1 in vivo, we reviewed pathological studies using mouse models and patients and then summarized arguments for and against possible involvement of wild-type SOD1 in non-SOD1 ALS as well as in SOD1-ALS.

TNF receptor-associated factor 6 interacts with ALS-linked misfolded superoxide dismutase 1 and promotes aggregation

Amyotrophic lateral sclerosis (ALS) is a fatal disease, characterized by the selective loss of motor neurons leading to paralysis. Mutations in the gene encoding superoxide dismutase 1 (SOD1) are the second most common cause of familial ALS, and considerable evidence suggests that these mutations result in an increase in toxicity due to protein misfolding. We previously demonstrated in the SOD1^G93A rat model that misfolded SOD1 exists as distinct conformers and forms deposits on mitochondrial subpopulations. Here, using SOD1^G93A rats and conformation-restricted antibodies specific for misfolded SOD1 (B8H10 and AMF7-63), we identified the interactomes of the mitochondrial pools of misfolded SOD1. This strategy identified binding proteins that uniquely interacted with either AMF7-63 or B8H10-reactive SOD1 conformers as well as a high proportion of interactors common to both conformers. Of this latter set, we identified the E3 ubiquitin ligase TNF receptor-associated factor 6 (TRAF6) as a SOD1 interactor, and we determined that exposure of the SOD1 functional loops facilitates this interaction. Of note, this conformational change was not universally fulfilled by all SOD1 variants and differentiated TRAF6 interacting from TRAF6 noninteracting SOD1 variants. Functionally, TRAF6 stimulated polyubiquitination and aggregation of the interacting SOD1 variants. TRAF6 E3 ubiquitin ligase activity was required for the former but was dispensable for the latter, indicating that TRAF6-mediated polyubiquitination and aggregation of the SOD1 variants are independent events. We propose that the interaction between misfolded SOD1 and TRAF6 may be relevant to the etiology of ALS.

Tryptophan residue 32 in human Cu-Zn superoxide dismutase modulates prion-like propagation and strain selection

Mutations in Cu/Zn superoxide dismutase 1 (SOD1) associated with familial amyotrophic lateral sclerosis cause the protein to aggregate via a prion-like process in which soluble molecules are recruited to aggregates by conformational templating. These misfolded SOD1 proteins can propagate aggregation-inducing conformations across cellular membranes. Prior studies demonstrated that mutation of a Trp (W) residue at position 32 to Ser (S) suppresses the propagation of misfolded conformations between cells, whereas other studies have shown that mutation of Trp 32 to Phe (F), or Cys 111 to Ser, can act in cis to attenuate aggregation of mutant SOD1. By expressing mutant SOD1 fused with yellow fluorescent protein (YFP), we compared the relative ability of these mutations to modulate the formation of inclusions by ALS-mutant SOD1 (G93A and G85R). Only mutation of Trp 32 to Ser persistently reduced the formation of the amorphous inclusions that form in these cells, consistent with the idea that a Ser at position 32 inhibits templated propagation of aggregation prone conformations. To further test this idea, we produced aggregated fibrils of recombinant SOD1-W32S in vitro and injected them into the spinal cords of newborn mice expressing G85R-SOD1: YFP. The injected mice developed an earlier onset paralysis with a frequency similar to mice injected with WT SOD1 fibrils, generating a strain of misfolded SOD1 that produced highly fibrillar inclusion pathology. These findings suggest that the effect of Trp 32 in modulating the propagation of misfolded SOD1 conformations may be dependent upon the “strain” of the conformer that is propagating.

The Matrisome during Aging and Longevity: A Systems-Level Approach toward Defining Matreotypes Promoting Healthy Aging

Accumulation of damage is generally considered the cause of aging. Interventions that delay aging mobilize mechanisms that protect and repair cellular components. Consequently, research has been focused on studying the protective and homeostatic mechanisms within cells. However, in humans and other multicellular organisms, cells are surrounded by extracellular matrices (ECMs), which are important for tissue structure, function, and intercellular communication. During aging, components of the ECM become damaged through fragmentation, glycation, crosslinking, and accumulation of protein aggregation, all of which contribute to age-related pathologies. Interestingly, placing senescent cells into a young ECM rejuvenates them. Furthermore, we found that many longevity-assurances pathways reactivate de novo synthesis of ECM proteins during aging. This raises the question of what constitutes a young ECM to reverse aging or maintain health? In order to make inroads to answering this question, I suggest a systems-level approach of quantifying the matrisome or ECM compositions reflecting health, pathology, or phenotype and propose a novel term, the "matreotype," to describe this. The matreotype is defined as the composition and modification of ECM or matrisome proteins associated with or caused by a phenotype, such as longevity, or a distinct and acute physiological state, as observed during aging or disease. Every cell type produces its unique ECM. Intriguingly, cancer-cell types can even be identified based on their unique ECM composition. Thus, the matreotype reflects cellular identity and physiological status. Defined matreotypes could be used as biomarkers or prognostic factors for disease or health status during aging with potential relevance for personalized medicine. Treatment with biologics that alter ECM-to-cell mechanotransduction might be a strategy to reverse age-associated pathologies. An understanding of how to reverse from an old to a young matreotype might point toward novel strategies to rejuvenate cells and help maintain tissue homeostasis to promote health during aging.

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.

Wild-type Cu/Zn-superoxide dismutase is misfolded in cerebrospinal fluid of sporadic amyotrophic lateral sclerosis

Background

A subset of familial forms of amyotrophic lateral sclerosis (ALS) are caused by mutations in the gene coding Cu/Zn-superoxide dismutase (SOD1). Mutant SOD1 proteins are susceptible to misfolding and abnormally accumulated in spinal cord, which is most severely affected in ALS. It, however, remains quite controversial whether misfolding of wild-type SOD1 is involved in more prevalent sporadic ALS (sALS) cases without SOD1 mutations.

Methods

Cerebrospinal fluid (CSF) from patients including sALS as well as several other neurodegenerative diseases and non-neurodegenerative diseases was examined with an immunoprecipitation assay and a sandwich ELISA using antibodies specifically recognizing misfolded SOD1.

Results

We found that wild-type SOD1 was misfolded in CSF from all sALS cases examined in this study. The misfolded SOD1 was also detected in CSF from a subset of Parkinson’s disease and progressive supranuclear palsy, albeit with smaller amounts than those in sALS. Furthermore, the CSF samples containing the misfolded SOD1 exhibited significant toxicity toward motor neuron-like NSC-34 cells, which was ameliorated by removal of the misfolded wild-type SOD1 with immunoprecipitation.

Conclusions

Taken together, we propose that misfolding of wild-type SOD1 in CSF is a common pathological process of ALS cases regardless of SOD1 mutations.

First-in-human trial of blood-brain barrier opening in amyotrophic lateral sclerosis using MR-guided focused ultrasound

MR-guided focused ultrasound (MRgFUS) is an emerging technology that can accurately and transiently permeabilize the blood-brain barrier (BBB) for targeted drug delivery to the central nervous system. We conducted a single-arm, first-in-human trial to investigate the safety and feasibility of MRgFUS-induced BBB opening in eloquent primary motor cortex in four volunteers with amyotrophic lateral sclerosis (ALS). Here, we show successful BBB opening using MRgFUS as demonstrated by gadolinium leakage at the target site immediately after sonication in all subjects, which normalized 24 hours later. The procedure was well-tolerated with no serious clinical, radiologic or electroencephalographic adverse events. This study demonstrates that non-invasive BBB permeabilization over the motor cortex using MRgFUS is safe, feasible, and reversible in ALS subjects. In future, MRgFUS can be coupled with promising therapeutics providing a targeted delivery platform in ALS.

Stem cell-derived cranial and spinal motor neurons reveal proteostatic differences between ALS resistant and sensitive motor neurons

In amyotrophic lateral sclerosis (ALS) spinal motor neurons (SpMN) progressively degenerate while a subset of cranial motor neurons (CrMN) are spared until late stages of the disease. Using a rapid and efficient protocol to differentiate mouse embryonic stem cells (ESC) to SpMNs and CrMNs, we now report that ESC-derived CrMNs accumulate less human (h)SOD1 and insoluble p62 than SpMNs over time. ESC-derived CrMNs have higher proteasome activity to degrade misfolded proteins and are intrinsically more resistant to chemically-induced proteostatic stress than SpMNs. Chemical and genetic activation of the proteasome rescues SpMN sensitivity to proteostatic stress. In agreement, the hSOD1 G93A mouse model reveals that ALS-resistant CrMNs accumulate less insoluble hSOD1 and p62-containing inclusions than SpMNs. Primary-derived ALS-resistant CrMNs are also more resistant than SpMNs to proteostatic stress. Thus, an ESC-based platform has identified a superior capacity to maintain a healthy proteome as a possible mechanism to resist ALS-induced neurodegeneration.

Transgenic and physiological mouse models give insights into different aspects of amyotrophic lateral sclerosis

A wide range of genetic mouse models is available to help researchers dissect human disease mechanisms. Each type of model has its own distinctive characteristics arising from the nature of the introduced mutation, as well as from the specific changes to the gene of interest. Here, we review the current range of mouse models with mutations in genes causative for the human neurodegenerative disease amyotrophic lateral sclerosis. We focus on the two main types of available mutants: transgenic mice and those that express mutant genes at physiological levels from gene targeting or from chemical mutagenesis. We compare the phenotypes for genes in which the two classes of model exist, to illustrate what they can teach us about different aspects of the disease, noting that informative models may not necessarily mimic the full trajectory of the human condition. Transgenic models can greatly overexpress mutant or wild-type proteins, giving us insight into protein deposition mechanisms, whereas models expressing mutant genes at physiological levels may develop slowly progressing phenotypes but illustrate early-stage disease processes. Although no mouse models fully recapitulate the human condition, almost all help researchers to understand normal and abnormal biological processes, providing that the individual characteristics of each model type, and how these may affect the interpretation of the data generated from each model, are considered and appreciated.

A human-derived antibody targets misfolded SOD1 and ameliorates motor symptoms in mouse models of amyotrophic lateral sclerosis

Mutations in the gene encoding superoxide dismutase 1 (SOD1) lead to misfolding and aggregation of SOD1 and cause familial amyotrophic lateral sclerosis (FALS). However, the implications of wild-type SOD1 misfolding in sporadic forms of ALS (SALS) remain unclear. By screening human memory B cells from a large cohort of healthy elderly subjects, we generated a recombinant human monoclonal antibody (α-miSOD1) that selectively bound to misfolded SOD1, but not to physiological SOD1 dimers. On postmortem spinal cord sections from 121 patients with ALS, α-miSOD1 antibody identified misfolded SOD1 in a majority of cases, regardless of their SOD1 genotype. In contrast, the α-miSOD1 antibody did not bind to its epitope in most of the 41 postmortem spinal cord sections from non-neurological control (NNC) patients. In transgenic mice overexpressing disease-causing human SOD1G37R or SOD1G93A mutations, treatment with the α-miSOD1 antibody delayed the onset of motor symptoms, extended survival by up to 2 months, and reduced aggregation of misfolded SOD1 and motor neuron degeneration. These effects were obtained whether α-miSOD1 antibody treatment was administered by direct brain infusion or peripheral administration. These results support the further development of α-miSOD1 antibody as a candidate treatment for ALS involving misfolding of SOD1.

Loss of charge mutations in solvent exposed Lys residues of superoxide dismutase 1 do not induce inclusion formation in cultured cell models

Mutations in superoxide dismutase 1 (SOD1) associated with familial amyotrophic lateral sclerosis (fALS) induce the protein to misfold and aggregate. Missense mutations at more than 80 different amino acid positions have been associated with disease. How these mutations heighten the propensity of SOD1 to misfold and aggregate is unclear. With so many mutations, it is possible that more than one mechanism of aggregation may be involved. Of many possible mechanisms to explain heightened aggregation, one that has been suggested is that mutations that eliminate charged amino acids could diminish repulsive forces that would inhibit aberrant protein:protein interactions. Mutations at twenty-one charged residues in SOD1 have been associated with fALS, but of the 11 Lys residues in the protein, only 1 has been identified as mutated in ALS patients. Here, we examined whether loss of positively charged surface Lys residues in SOD1 would induce misfolding and formation of intracellular inclusions. We mutated four different Lys residues (K30, K36, K75, K91) in SOD1 that are not particularly well conserved, and expressed these variants as fusion proteins with yellow fluorescent protein (YFP) to assess inclusion formation. We also assessed whether these mutations induced binding to a conformation-restricted SOD1 antibody, designated C4F6, which recognizes non-natively folded protein. Although we observed some mutations to cause enhanced C4F6 binding, we did not observe that mutations that reduce charge at these positions caused the protein to form intracellular inclusions. Our findings may have implications for the low frequency of mutations at Lys residues SOD1 in ALS patients.

Misfolded SOD1 pathology in sporadic Amyotrophic Lateral Sclerosis

Aggregation of mutant superoxide dismutase 1 (SOD1) is a pathological hallmark of a subset of familial ALS patients. However, the possible role of misfolded wild type SOD1 in human ALS is highly debated. To ascertain whether or not misfolded SOD1 is a common pathological feature in non-SOD1 ALS, we performed a blinded histological and biochemical analysis of post mortem brain and spinal cord tissues from 19 sporadic ALS, compared with a SOD1 A4V patient as well as Alzheimer’s disease (AD) and non-neurological controls. Multiple conformation- or misfolded-specific antibodies for human SOD1 were compared. These were generated independently by different research groups and were compared using standardized conditions. Five different misSOD1 staining patterns were found consistently in tissue sections from SALS cases and the SOD1 A4V patient, but were essentially absent in AD and non-neurological controls. We have established clear experimental protocols and provide specific guidelines for working, with conformational/misfolded SOD1-specific antibodies. Adherence to these guidelines will aid in the comparison of the results of future studies and better interpretation of staining patterns. This blinded, standardized and unbiased approach provides further support for a possible pathological role of misSOD1 in SALS.

Dynamic assessment of tau immunotherapies in the brains of live animals by two-photon imaging

Our original findings, showing the effectiveness of active and passive tau immunizations in mouse models, have now been confirmed and extended by many groups, with several clinical trials underway in Alzheimer's disease and progressive supranuclear palsy. Here, we report on a unique and sensitive two-photon imaging approach to concurrently study the dynamics of brain and neuronal uptake and clearance of tau antibodies as well as the acute removal of their pathological target in live animals. This in vivo technique is more sensitive to detect clearance of pathological tau protein than western blot tau analysis of brain tissue. In addition to providing an insight into the mechanisms involved, it allows for an efficient in vivo assessment of the therapeutic potential of tau antibodies, and may be applied to related protein misfolding diseases.

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Two-photon imaging approach to study uptake and clearance of tau antibodies, and removal of their target in live animals.

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This technique is more sensitive to detect clearance of pathological tau protein than western blot analysis of brain tissue.

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It allows for an acute in vivo determination of the therapeutic potential of tau antibodies.

Endoplasmic reticulum stress leads to accumulation of wild-type SOD1 aggregates associated with sporadic amyotrophic lateral sclerosis

Abnormal modifications to mutant superoxide dismutase 1 (SOD1) are linked to familial amyotrophic lateral sclerosis (fALS). Misfolding of wild-type SOD1 (SOD1WT) is also observed in postmortem tissue of a subset of sporadic ALS (sALS) cases, but cellular and molecular mechanisms generating abnormal SOD1WT species are unknown. We analyzed aberrant human SOD1WT species over the lifetime of transgenic mice and found the accumulation of disulfide-cross-linked high-molecular-weight SOD1WT aggregates during aging. Subcellular fractionation of spinal cord tissue and protein overexpression in NSC-34 motoneuron-like cells revealed that endoplasmic reticulum (ER) localization favors oxidation and disulfide-dependent aggregation of SOD1WT We established a pharmacological paradigm of chronic ER stress in vivo, which recapitulated SOD1WTaggregation in young transgenic mice. These species were soluble in nondenaturing detergents and did not react with a SOD1 conformation-specific antibody. Interestingly, SOD1WT aggregation under ER stress correlated with astrocyte activation in the spinal cord of transgenic mice. Finally, the disulfide-cross-linked SOD1WT species were also found augmented in spinal cord tissue of sALS patients, correlating with the presence of ER stress markers. Overall, this study suggests that ER stress increases the susceptibility of SOD1WT to aggregate during aging, operating as a possible risk factor for developing ALS.

Defective daily temperature regulation in a mouse model of amyotrophic lateral sclerosis

Current understanding of the pathogenesis of the familial form of amyotrophic lateral sclerosis has been aided by the study of transgenic mice that over-express mutated forms of the human CuZn-superoxide dismutase (SOD1) gene. While mutant SOD1 in motor neurons determines disease onset, other non-cell autonomous factors are critical for disease progression, and altered energy metabolism has been implicated as a contributing factor. Since most energy expended by laboratory mice is utilized to defend body temperature (T_b), we analyzed thermoregulation in transgenic mice carrying the G93A mutation of the human SOD1 gene, using implantable temperature data loggers to continuously record T_b for up to 85 days. At room (22 °C) ambient temperature, G93A mice exhibited a diminished amplitude of the daily T_b rhythm compared to C57BL/6J controls, secondary to decreased T_b values during the dark (behaviorally active) phase of the light-dark cycle. The defect arose at 85-99 days of age, around the age of symptom onset (as assessed by grip strength), well before observable weakness and weight loss, and could not be accounted for by decreased levels of locomotor activity or food consumption. Housing under thermoneutral (29 °C) ambient temperature partially rescued the defect, but age-dependently (only in animals >100 days of age), suggesting that the deficit in older mice was due in part to inadequate thermogenesis by "peripheral" thermogenic organs as the disease progressed. In younger mice, we found that cold-induced thermogenesis and energy expenditure were intact, hinting that an initial "central" defect might localize to the subparaventricular zone, involving neural output pathways from the circadian clock in the hypothalamic suprachiasmatic nucleus to forebrain thermoregulatory circuitry.

Antisense oligonucleotides extend survival and reverse decrement in muscle response in ALS models

Mutations in superoxide dismutase 1 (SOD1) are responsible for 20% of familial ALS. Given the gain of toxic function in this dominantly inherited disease, lowering SOD1 mRNA and protein is predicted to provide therapeutic benefit. An early generation antisense oligonucleotide (ASO) targeting SOD1 was identified and tested in a phase I human clinical trial, based on modest protection in animal models of SOD1 ALS. Although the clinical trial provided encouraging safety data, the drug was not advanced because there was progress in designing other, more potent ASOs for CNS application. We have developed next-generation SOD1 ASOs that more potently reduce SOD1 mRNA and protein and extend survival by more than 50 days in SOD1G93A rats and by almost 40 days in SOD1G93A mice. We demonstrated that the initial loss of compound muscle action potential in SOD1G93A mice is reversed after a single dose of SOD1 ASO. Furthermore, increases in serum phospho-neurofilament heavy chain levels, a promising biomarker for ALS, are stopped by SOD1 ASO therapy. These results define a highly potent, new SOD1 ASO ready for human clinical trial and suggest that at least some components of muscle response can be reversed by therapy.

Systemic overexpression of SQSTM1/p62 accelerates disease onset in a SOD1H46R-expressing ALS mouse model

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by a selective loss of upper and lower motor neurons. Recent studies have shown that mutations in SQSTM1 are linked to ALS. SQSTM1 encodes SQSTM1/p62 that regulates not only autophagy via the association with MAP1LC3/LC3 and ubiquitinated proteins but also the KEAP1-NFE2L2/Nrf2 anti-oxidative stress pathway by interacting with KEAP1. Previously, we have demonstrated that loss of SQSTM1 exacerbates disease phenotypes in a SOD1^H46R-expressing ALS mouse model. To clarify the effects of SQSTM1 overexpression in this model, we generated SQSTM1 and SOD1 ^H46R double-transgenic (SQSTM1;SOD1 ^H46R ) mice. SQSTM1;SOD1 ^H46R mice exhibited earlier disease onset and shorter lifespan than did SOD1 ^H46R mice. Conversely, disease progression after the onset rather slightly but significantly slowed in SQSTM1;SOD1 ^H46R mice. However, there were observable differences neither in the number of Nissl positive neurons nor in the distribution of ubiquitin-positive and/or SQSTM1-positive aggregates between SOD1 ^H46R and SQSTM1;SOD1 ^H46R mice. It was noted that these protein aggregates were mainly observed in neuropil, and partly localized to astrocytes and/or microglia, but not to MAP2-positive neuronal cell bodies and dendrites at the end-stage of disease. Nonetheless, the biochemically-detectable insoluble SQSTM1 and poly-ubiquitinated proteins were significantly and progressively increased in the spinal cord of SQSTM1;SOD1 ^H46R mice compared to SOD1 ^H46R mice. These results suggest that overexpression of SQSTM1 in SOD1 ^H46R mice accelerates disease onset by compromising the protein degradation pathways.

[An early history of Japanese amyotrophic lateral sclerosis (ALS)-related diseases and the current development]

The present review focuses an early history of Japanese amyotrophic lateral sclerosis (ALS)-related diseases and the current development. In relation to foreign previous reports, five topics are introduced and discussed on ALS with dementia, ALS/Parkinsonism dementia complex (ALS/PDC), familial ALS (FALS), spinal bulbar muscular atrophy (SBMA), and multisystem involvement especially in cerebellar system of ALS including ALS/SCA (spinocerebellar ataxia) crossroad mutation Asidan. This review found the great contribution of Japanese reports on the above five topics, and confirmed the great development of ALS-related diseases over the past 120 years.

A copper-deficient form of mutant Cu/Zn-superoxide dismutase as an early pathological species in amyotrophic lateral sclerosis

Dominant mutations in the gene encoding copper and zinc-binding superoxide dismutase (SOD1) cause amyotrophic lateral sclerosis (ALS). Abnormal accumulation of misfolded SOD1 proteins in spinal motoneurons is a major pathological hallmark in SOD1-related ALS. Dissociation of copper and/or zinc ions from SOD1 has been shown to trigger the protein aggregation/oligomerization in vitro, but the pathological contribution of such metal dissociation to the SOD1 misfolding still remains obscure. Here, we tested the relevance of the metal-deficient SOD1 in the misfolding in vivo by developing a novel antibody (anti-apoSOD), which exclusively recognized mutant SOD1 deficient in metal ions at its copper-binding site. Notably, anti-apoSOD-reactive species were detected specifically in the spinal cords of the ALS model mice only at their early pre-symptomatic stages but not at the end stage of the disease. The cerebrospinal fluid as well as the spinal cord homogenate of one SOD1-ALS patient also contained the anti-apoSOD-reactive species. Our results thus suggest that metal-deficiency in mutant SOD1 at its copper-binding site is one of the earliest pathological features in SOD1-ALS.