Mechanisms of protein toxicity in neurodegenerative diseases

Imaging methods to monitor and quantify cell differentiation

The transition of a cell from a stem to a differentiated state involves an interrelated and complex series of events. These events include dynamic changes in cellular nucleic acid and protein content that are mediated by both intrinsic and extrinsic factors which ultimately lead to differentiation into specific lineage. Quantifying the parameters associated with differentiation and their changes under different conditions would not only allow for a better understanding of this process but also would enable the development of approaches that control differentiation. Here, we describe processes associated with the differentiation of two types of cultured cells, neurons and fibroblasts, and the tools to follow changes in real time. Specifically, we discuss methods to the identify cell lineage, changes in morphology, shifts in specific mRNA and miRNA levels as well as the changes in protein localization, interactions and assemblies that accompany differentiation.

Nanomaterial-based approaches to neurotoxin neutralization in neurodegenerative diseases

Neurodegenerative diseases (NDs) are intricately linked to the accumulation of various neurotoxins, mainly including toxic proteins, inflammatory mediators, excess metal ions, and viral pathogens. Biological neutralization strategies that use agents to competitively bind harmful substances and thus inhibit their pathogenic activity hold promise for direct removal of neurotoxins but face many limitations and challenges in NDs. Nanomaterials provide a potential solution for neurotoxin neutralization in NDs due to their unique physicochemical and biological properties. This review summarizes recent advancements in nanomaterial-based approaches to neurotoxin neutralization in NDs, highlighting the diverse design principles and mechanisms of action. We also discuss the critical role of targeted delivery to optimize neutralization efficiency and the advantages of combining different neutralization mechanisms or introducing other therapeutic components to exert the synergistic effects. Furthermore, we reveal current limitations and future research directions aimed at paving the way for nanomedicine development based on neurotoxin neutralization for the treatment of NDs.

Incidence of optic nerve kinking in a cohort of patients with Normal tension glaucoma

OBJECTIVES

To report on the incidence of optic nerve kinking in a series of patients diagnosed with normal-tension glaucoma (NTG) compared to an age- and gender matched control group without known optic nerve diseases.

SUBJECTS AND METHODS

All patients with NTG who underwent imaging (computed tomography cysternography (CTC) or magnetic resonance imaging (MRI)) of the orbits and cranium between 2012 and 2022 were included, totalling 57 patients (27 females and 30 males; 57 eyes; mean age 69 ± 10 years). 57 age- and gender matched subjects without known optic nerve diseases who underwent MRI of the orbits and cranium served as controls. Radiographic images of the orbits were analysed for the presence of optic nerve kinking.

RESULTS

In the axial plane at least one optic nerve kink was found in 49 of 57 (86%) optic nerves in patients with NTG and in 10 of 57 (18%) optic nerves in controls (p < 0.0001) while in the sagittal plane in 28 of 57 (49%) optic nerves in patients with NTG and in 1 of 57 (2%) optic nerves in controls (p < 0.0001) (Fisher's two-tailed exact test).

CONCLUSIONS

This study demonstrates a high statistically significant incidence of optic nerve kinking in patients with NTG compared to controls without known optic nerve diseases. Its possible role involved in the pathophysiology of NTG needs to be evaluated.

From Molecular Therapies to Lysosomal Transplantation and Targeted Drug Strategies: Present Applications, Limitations, and Future Prospects of Lysosomal Medications

Lysosomes are essential intracellular organelles involved in plentiful cellular processes such as cell signaling, metabolism, growth, apoptosis, autophagy, protein processing, and maintaining cellular homeostasis. Their dysfunction is linked to various diseases, including lysosomal storage disorders, inflammation, cancer, cardiovascular diseases, neurodegenerative conditions, and aging. This review focuses on current and emerging therapies for lysosomal diseases (LDs), including small medicines, enzyme replacement therapy (ERT), gene therapy, transplantation, and lysosomal drug targeting (LDT). This study was conducted through databases like PubMed, Google Scholar, Science Direct, and other research engines. To treat LDs, medicines target the lysosomal membrane, acidification processes, cathepsins, calcium signaling, mTOR, and autophagy. Moreover, small-molecule therapies using chaperones, macro-therapies like ERT, gene therapy, and gene editing technologies are used as therapy for LDs. Additionally, endosymbiotic therapy, artificial lysosomes, and lysosomal transplantation are promising options for LD management. LDT enhances the therapeutic outcomes in LDs. Extracellular vesicles and mannose-6-phosphate-tagged nanocarriers display promising approaches for improving LDT. This study concluded that lysosomes play a crucial role in the pathophysiology of numerous diseases. Thus, restoring lysosomal function is essential for treating a wide range of conditions. Despite endosymbiotic therapy, artificial lysosomes, lysosomal transplantation, and LDT offering significant potential for LD control, there are ample challenges regarding safety and ethical implications.

Mechanisms and early efficacy data of caloric restriction and caloric restriction mimetics in neurodegenerative disease

Neurodegenerative disorders (NDDs) have been prevalent for more than a decade, and the number of individuals affected per year has increased exponentially. Among these NDDs, Alzheimer's disease, which causes extreme cognitive impairment, and Parkinson's disease, characterized by impairments in motor activity, are the most prevalent. While few treatments are available for clinical practice, they have minimal effects on reversing the neurodegeneration associated with these debilitating diseases. Lifestyle modifications and dietary choices are emerging and promising approaches to combat these disorders. Of the lifestyle changes that one could adopt, a major habit is caloric restriction. Caloric restriction (CR) is a lifestyle modification in which the amount of calories ingested is reduced to a significant amount without resulting in malnutrition. However, maintaining such a lifestyle is challenging. As alternatives, certain compounds have been recognized to mimic the effects produced by CR. These compounds are called caloric restriction mimetics (CRMs). Among these compounds, some have been designated established CRMs, namely, resveratrol, metformin, and rapamycin, whereas several other candidates are termed potential CRMs because of a lack of conclusive evidence of their effects. The potential CRMs discussed in this review are quercetin, chrysin, astragalin, apigenin, curcumin, epigallocatechin-3-gallate, and NAD+ precursors. This review aims to provide an overview of these CRMs' effectiveness in preventing neurodegenerative disorders associated with aging. Moreover, we highlight the clinical relevance of these compounds by discussing in detail the results of clinical trials on them.

Emerging biophysical techniques for probing synaptic transmission in neurodegenerative disorders

Plethora of research has shed light on the critical role of synaptic dysfunction in various neurodegenerative disorders (NDDs), including Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). Synapses, the fundamental units for neural communication in the brain, are highly vulnerable to pathological conditions and are central to the progression of neurological diseases. The presynaptic terminal, a key component of synapses responsible for neurotransmitter release and synaptic communication, undergoes structural and functional alterations in these disorders. Understanding synaptic transmission abnormalities is crucial for unravelling the pathophysiological mechanisms underlying neurodegeneration. In the quest to probe synaptic transmission in NDDs, emerging biophysical techniques play a pivotal role. These advanced methods offer insights into the structural and functional changes occurring at nerve terminals in conditions like AD, PD, HD & ALS. By investigating synaptic plasticity and alterations in neurotransmitter release dynamics, researchers can uncover valuable information about disease progression and potential therapeutic targets. The review articles highlighted provide a comprehensive overview of how synaptic vulnerability and pathology are shared mechanisms across a spectrum of neurological disorders. In major neurodegenerative diseases, synaptic dysfunction is a common thread linking these conditions. The intricate molecular machinery involved in neurotransmitter release, synaptic vesicle dynamics, and presynaptic protein regulation are key areas of focus for understanding synaptic alterations in neurodegenerative diseases.

The Crucial Role of the Blood-Brain Barrier in Neurodegenerative Diseases: Mechanisms of Disruption and Therapeutic Implications

The blood-brain barrier (BBB) is a crucial structure that maintains brain homeostasis by regulating the entry of molecules and cells from the bloodstream into the central nervous system (CNS). Neurodegenerative diseases such as Alzheimer's and Parkinson's disease, as well as ischemic stroke, compromise the integrity of the BBB. This leads to increased permeability and the infiltration of harmful substances, thereby accelerating neurodegeneration. In this review, we explore the mechanisms underlying BBB disruption, including oxidative stress, neuroinflammation, vascular dysfunction, and the loss of tight junction integrity, in patients with neurodegenerative diseases. We discuss how BBB breakdown contributes to neuroinflammation, neurotoxicity, and the abnormal accumulation of pathological proteins, all of which exacerbate neuronal damage and facilitate disease progression. Furthermore, we discuss potential therapeutic strategies aimed at preserving or restoring BBB function, such as anti-inflammatory treatments, antioxidant therapies, and approaches to enhance tight junction integrity. Given the central role of the BBB in neurodegeneration, maintaining its integrity represents a promising therapeutic approach to slow or prevent the progression of neurodegenerative diseases.

Rosmarinic acid ameliorated oxidative stress, neuronal injuries, and mitochondrial dysfunctions mediated by polyglutamine and ɑ-synuclein in Caenorhabditis elegans models

Numerous natural antioxidants have been developed into agents for neurodegenerative diseases (NDs) treatment. Rosmarinic acid (RA), an excellent antioxidant, exhibits neuroprotective activity, but its anti-NDs efficacy remains puzzling. Here, Caenorhabditis elegans models were employed to systematically reveal RA-mediated mechanisms in delaying NDs from diverse facets, including oxidative stress, the homeostasis of neural and protein, and mitochondrial disorders. Firstly, RA significantly inhibited reactive oxygen species accumulation, reduced peroxide malonaldehyde production, and strengthened the antioxidant defense system via increasing superoxide dismutase activity. Besides, RA reduced neuronal loss and ameliorated polyglutamine and ɑ-synuclein-mediated dyskinesia in NDs models. Further, in combination with the data and molecular docking results, RA may bind specifically to Huntington protein and ɑ-synuclein to prevent toxic protein aggregation and thus enhance proteostasis. Finally, RA ameliorated mitochondrial dysfunction including increasing adenosine triphosphate and mitochondrial membrane potential levels and rescuing mitochondrial membrane proteins' expressions and mitochondrial structural abnormalities via regulating mitochondrial dynamics genes and improving the mitochondrial kinetic homeostasis. Thus, this study systematically revealed the RA-mediated neuroprotective mechanism and promoted RA as a promising nutritional intervention strategy to prevent NDs.

Bisdemethoxycurcumin, a novel potent polyphenolic compound, effectively inhibits the formation of amyloid aggregates in ALS-associated hSOD1 mutant (L38R)

Protein misfolding is a biological process that leads to protein aggregation. Anomalous misfolding and aggregation of human superoxide dismutase (hSOD1) into amyloid aggregates is a characteristic feature of amyotrophic lateral sclerosis (ALS), a neurodegenerative illness. Thus, focusing on the L38R mutant may be a wise decision to comprehend the SOD1 disease process in ALS. We suggest that Bisdemethoxycurcumin (BDMC) may be a strong anti-amyloidogenic polyphenol against L38R mutant aggregation. Protein stability, hydrophobicity, and flexibility were altered when BDMC was bound to the L38R mutant, as shown by molecular dynamic (MD) simulations and molecular docking. FTIR data shows α-Helix dominance in BDMC-containing samples, with reduced β-sheet and disordered peaks, indicating the decrease of aggregate species. ThT aggregation kinetics curves show BDMC reduces L38R mutant aggregation dose-dependently, with higher BDMC concentrations yielding greater reductions. TEM images showed various quantities of amorphous aggregates, but notably, 60 μM BDMC markedly reduced aggregate density, underscoring BDMC's inhibitory effect. Hemolysis tests revealed aggregate species in BDMC-treated samples were less toxic than in L38R mutant samples alone at the same concentrations and exposure times. Overall, BDMC has substantial potential to develop highly effective inhibitors that mitigate the risk of fatal ALS.

Age related cerebrospinal fluid flow dynamics in the subarachnoid space of the optic nerve in patients with normal tension glaucoma, measured by diffusion weighted MRI

BACKGROUND/OBJECTIVES

We aimed to measure cerebrospinal fluid (CSF) flow rates in the subarachnoid space (SAS) of the optic nerve (ON) by applying non-invasive diffusion-weighted MRI in patients with normal tension glaucoma (NTG) compared to age-matched controls.

SUBJECTS/METHODS

In this prospective study, an analysis of diffusion-weighted images of 26 patients with NTG (49ONs) and age-matched volunteers (52ONs) was conducted. Subjects were classified into 4 groups: group I (50-59 y., n = 12 eyes), group II (60-69 y., n = 16 eyes), group III (70-79 y., n = 18 eyes) and group IV ( > 80 y., n = 6 eyes) for NTGs and healthy volunteers, respectively. The flow-range ratio (FRR) between the frontal lobe SAS and the SAS of the ON was calculated for each age category group and then compared between age-categories as well as between NTGs and controls.

RESULTS

The mean FRR for age groups were (I) 0.54 ± 0.06 and 0.62 ± 0.03 (p < 0.05), (II) 0.56 ± 0.08 and 0.63 ± 0.03 (p < 0.05), (III) 0.54 ± 0.06 and 0.62 ± 0.02 (p < 0.001) as well as (IV) 0.61 ± 0.03 and 0.61 ± 0.04, for NTGs and controls, respectively. Using pooled data, the difference between the FRR in NTGs and controls was statistically significant (p < 0.0001). There were no statistically significant differences within the age categories of the control group. When comparing the FRR of NTGs by age categories, no statistically significant difference was found between the subgroups.

CONCLUSIONS

FRR was significantly reduced in NTGs compared to age-matched controls without any significant differences within the age groups themselves. Given the physiological importance of CSF for the integrity of neurons, axons and glial cells, reduced CSF flow dynamics might be part of the underlying neurodegenerative process of NTG.

A Drosophila model for mechanistic investigation of tau protein spread

Brain protein aggregates are a hallmark of neurodegenerative disease. Previous work indicates that specific protein components of these aggregates are toxic, including tau (encoded by MAPT) in Alzheimer's disease and related tauopathies. Increasing evidence also indicates that these toxic proteins traffic between cells in a prion-like fashion, thereby spreading pathology from one brain region to another. However, the mechanisms involved in trafficking are poorly understood. We therefore developed a transgenic Drosophila model to facilitate rapid evaluation of candidate tau trafficking modifiers. Our model uses the bipartite Q system to drive co-expression of tau and GFP in the fly eye. We found age-dependent spread of tau into the brain, represented by detection of tau, but not of GFP. We also found that tau trafficking was attenuated upon inhibition of the endocytic factor dynamin (encoded by shi) or knockdown of glycogen synthase kinase-3β (GSK-3β, encoded by sgg). Further work revealed that dynamin promoted tau uptake in recipient tissues, whereas GSK-3β appeared to promote tau spread via direct phosphorylation of tau. Our robust and flexible system will promote the identification of tau-trafficking components involved in the pathogenesis of neurodegenerative diseases.

Novel strategies in Parkinson's disease treatment: a review

An unprecedented extension of life expectancy observed during the past century drastically increased the number of patients diagnosed with Parkinson's diseases (PD) worldwide. Estimated costs of PD alone reached $52 billion per year, making effective neuroprotective treatments an urgent and unmet need. Current treatments of both AD and PD focus on mitigating the symptoms associated with these pathologies and are not neuroprotective. In this review, we discuss the most advanced therapeutic strategies that can be used to treat PD. We also critically review the shift of the therapeutic paradigm from a small molecule-based inhibition of protein aggregation to the utilization of natural degradation pathways and immune cells that are capable of degrading toxic amyloid deposits in the brain of PD patients.

Hetero-oligomerization of TDP-43 carboxy-terminal fragments with cellular proteins contributes to proteotoxicity

Carboxy terminal fragments (CTFs) of TDP-43 contain an intrinsically disordered region (IDR) and form cytoplasmic condensates containing amyloid fibrils. Such condensates are toxic and associated with pathogenicity in amyotrophic lateral sclerosis. However, the molecular details of how the domain of TDP-43 CTFs leads to condensation and cytotoxicity remain elusive. Here, we show that truncated RNA/DNA-recognition motif (RRM) at the N-terminus of TDP-43 CTFs leads to the structural transition of the IDR, whereas the IDR itself of TDP-43 CTFs is difficult to assemble even if they are proximate intermolecularly. Hetero-oligomers of TDP-43 CTFs that have recruited other proteins are more toxic than homo-oligomers, implicating loss-of-function of the endogenous proteins by such oligomers is associated with cytotoxicity. Furthermore, such toxicity of TDP-43 CTFs was cell-nonautonomously affected in the nematodes. Therefore, misfolding and oligomeric characteristics of the truncated RRM at the N-terminus of TDP-43 CTFs define their condensation properties and toxicity.

A Drosophila model for mechanistic investigation of tau protein spread

Brain protein aggregates are a hallmark of neurodegenerative disease. Previous work indicates that specific protein components of these aggregates are toxic, including tau in Alzheimer's disease and related tauopathies. Increasing evidence also indicates that these toxic proteins traffic between cells in a prion-like fashion, thereby spreading pathology from one brain region to another. However, the mechanisms involved in trafficking are poorly understood. We therefore developed a transgenic Drosophila model to facilitate rapid evaluation of candidate tau trafficking modifiers. Our model uses the bipartite Q system to drive co-expression of tau and GFP in the fly eye. We find age-dependent tau spread into the brain, represented by detection of tau, but not GFP in the brain. We also found that tau trafficking was attenuated upon inhibition of the endocytic factor dynamin or the kinase glycogen synthase kinase-3β ( GSK-3β ). Further work revealed that dynamin promotes tau uptake in recipient tissues, whereas GSK-3β appears to promote tau spread via direct phosphorylation of tau. Our robust and flexible system will promote the identification of tau trafficking components involved in the pathogenesis of neurodegenerative diseases.

SUMMARY STATEMENT

The trafficking of toxic proteins in neurodegenerative disease is well-known but poorly understood. Our model will allow rapid and new insight into molecular mechanisms underlying this process.

The hidden world of protein aggregation

Though the book's journey into The Hidden World of Protein Aggregation has come to an end, the search for knowledge, the development of healthier lives, and the discovery of nature's mysteries continue, promising new horizons and discoveries yet to be discovered. The intricacies of protein misfolding and aggregation remain a mystery in cellular biology, despite advances made in unraveling them. In this chapter, we will summarize the specific conclusions from the previous chapters and explore the persistent obstacles and unanswered questions that motivate scientists to pursue exploration of protein misfolding and aggregation.

Selective vulnerability and resilience to Alzheimer's disease tauopathy as a function of genes and the connectome

Brain regions in Alzheimer's (AD) exhibit distinct vulnerability to the disease's hallmark pathology, with the entorhinal cortex and hippocampus succumbing early to tau tangles while others like primary sensory cortices remain resilient. The quest to understand how local/regional genetic factors, pathogenesis, and network-mediated spread of pathology together govern this selective vulnerability (SV) or resilience (SR) is ongoing. Although many risk genes in AD are known from gene association and transgenic studies, it is still not known whether and how their baseline expression signatures confer SV or SR to brain structures. Prior analyses have yielded conflicting results, pointing to a disconnect between the location of genetic risk factors and downstream tau pathology. We hypothesize that a full accounting of genes' role in mediating SV/SR would require the modeling of network-based vulnerability, whereby tau misfolds, aggregates, and propagates along fiber projections. We therefore employed an extended network diffusion model (eNDM) and tested it on tau pathology PET data from 196 AD patients from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Thus the fitted eNDM model becomes a reference process from which to assess the role of innate genetic factors. Using the residual (observed - model-predicted) tau as a novel target outcome, we obtained its association with 100 top AD risk-genes, whose baseline spatial transcriptional profiles were obtained from the Allen Human Brain Atlas (AHBA). We found that while many risk genes at baseline showed a strong association with regional tau, many more showed a stronger association with residual tau. This suggests that both direct vulnerability, related to the network, as well as network-independent vulnerability, are conferred by risk genes. We then classified risk genes into four classes: network-related SV (SV-NR), network-independent SV (SV-NI), network-related SR (SR-NR), and network-independent SR (SR-NI). Each class has a distinct spatial signature and associated vulnerability to tau. Remarkably, we found from gene-ontology analyses, that genes in these classes were enriched in distinct functional processes and encompassed different functional networks. These findings offer new insights into the factors governing innate vulnerability or resilience in AD pathophysiology and may prove helpful in identifying potential intervention targets.

Neuroprotective mechanisms of defatted walnut powder against scopolamine-induced Alzheimer's disease in mice revealed through metabolomics and proteomics analyses

ETHNOPHARMACOLOGICAL RELEVANCE

Defatted walnut powder (DWP), the byproduct remaining after extracting oil from the walnut kernel, has the actions of nourishing liver and the kidney, replenishing blood, and calming the nerves, which is believed to be a brain-nourishing in Chinese medicine. DWP is rich in phenolic substances with demonstrated anti-inflammatory, antioxidant, lipid-lowering and neuroprotective effects. Despite these promising properties of DWP, its effectiveness in treating Alzheimer's disease (AD) remains unclear, and further research is needed to understand the mechanism of action.

AIM OF THE STUDY

This study aimed to investigate the potential mechanism of DWP on AD by constructing the overall metabolic profile of mice with an anti-scopolamine AD model and verification of the highly correlated pathway.

MATERIALS AND METHODS

The neuroprotective efficacy of DWP in a mouse model of AD established by scopolamine injection was examined. Spatial memory performance in the Morris water maze (MWM), markers of cholinergic function in hippocampus and cortex, and neuropathological changes were compared among control, model, and DWP-consuming model group mice. In addition, combined metabolomic and proteomic analyses were conducted to investigate changes in metabolite and protein expression profiles in AD model mice induced by DWP consumption. Differentially expressed proteins and metabolites were then analyzed for KEGG pathway enrichment and results confirmed through targeted amino acid metabolomics.

RESULTS

The results showed that consumption of DWP improved spatial learning and memory in the MWM, enhanced cholinergic function, and reduced histopathological damage in the cortex and hippocampus of AD model mice. Based on differentially abundant metabolites and proteins, 43 metabolic pathways modulated by DWP were identified, mainly involving in amino acid metabolic pathways strongly associated with cellular energetics and antioxidant capacity, and targeted amino acid metabolomics confirmed that DWPE significantly elevated the levels of Arginine (Arg), Histidine (His), Proline (Pro), Serine (Ser), and Tyrosine (Tyr), while reducing the levels of Glutamate (Glu). This ultimately resulted in an improvement in the progression of AD.

CONCLUSION

This study identified numerous metabolic networks modulated by DWP that can mitigate scopolamine-induced AD neuropathology and cognitive dysfunction. DWP is a promising resource to identify AD-related pathogenic pathways and therapeutic strategies.

Recombinant Full-Length TDP-43 Oligomers Retain Their Ability to Bind RNAs, Are Not Toxic, and Do Not Seed TDP-43 Aggregation in Vitro

TAR DNA-binding protein with 43 kD (TDP-43) is a partially disordered protein that misfolds and accumulates in the brains of patients affected by several neurodegenerative diseases. TDP-43 oligomers have been reported to form due to aberrant misfolding or self-assembly of TDP-43 monomers. However, very little is known about the molecular and structural basis of TDP-43 oligomerization and the toxic properties of TDP-43 oligomers due to several reasons, including the lack of conditions available for isolating native TDP-43 oligomers or producing pure TDP-43 oligomers in sufficient quantities for biophysical, cellular, and in vivo studies. To address these challenges, we developed new protocols to generate different stable forms of unmodified and small-molecule-induced TDP-43 oligomers. Our results showed that co-incubation of TDP-43 with small molecules, such as epigallocatechin gallate (EGCG), dopamine, and 4-hydroxynonenal (4-HNE), increased the production yield of TDP-43 stable oligomers, which could be purified by size-exclusion chromatography. Interestingly, despite significant differences in the morphology and size distribution of the TDP-43 oligomer preparations revealed by transmission electron microscopy (TEM) and dynamic light scattering (DLS), they all retained the ability to bind to nucleotide DNA. Besides, circular dichroism (CD) analysis of these oligomers did not show much difference in the secondary structure composition. Surprisingly, none of these oligomer preparations could seed the aggregation of TDP-43 core peptide 279-360. Finally, we showed that all four types of TDP-43 oligomers exert very mild cytotoxicity to primary neurons. Collectively, our results suggest that functional TDP-43 oligomers can be selectively stabilized by small-molecule compounds. This strategy may offer a new approach to halt TDP-43 aggregation in various proteinopathies.

The flavonoid luteolin reduces mutant huntingtin aggregation and cytotoxicity in huntingtin-mutated neuroblastoma cells

Background

Huntington's disease is an inherited progressive neurodegenerative disorder caused by an expansion of the polyglutamine tract leading to malformation and aggregation of the mutant huntingtin protein in the cell cytoplasm and nucleus of affected brain regions. The development of neuroprotective agents from plants has received considerable research attention.

Objective

Our study aims to investigate the neuroprotective effects of luteolin and the mechanisms that underline its potential mediated protection in the mutant htt neuroblastoma cells.

Methods

The mutant htt neuroblastoma cells were transfected with 160Q, and the control wild-type neuroblastoma cells were transfected with 20Q htt for 24 h and later treated with luteolin. Cell viability was determined by MTT and PI staining in both groups, while western blotting was used to evaluate caspase 3 protein expression. Aggregation formation was assessed via immunofluorescence microscopy. Also, western blotting was utilized to measure the protein expression of mutant htt aggregated and soluble protein, Nrf2 and HO-1. The impact of Nrf2 on luteolin-treated neuroblastoma cells was assessed using small interfering RNAs.

Results

Our study reports that luteolin can protect cultured cells from mutant huntingtin cytotoxicity, evidenced by increased viability and decreased apoptosis. Also, luteolin reduced the accumulation of soluble and insoluble mutant huntingtin aggregates in mutant htt neuroblastoma cells transfected with 160Q compared to the control wild-type. The mutant htt aggregate reduction mediated by luteolin appeared to be independent of the Nrf2 -HO-1 antioxidant pathway.

Conclusion

Luteolin presents a new potential therapeutic and protective agent for the treatment and decreasing the cytotoxicity in neurodegenerative diseases such as Huntington's disease.

Reduced coupling of global brain function and cerebrospinal fluid dynamics in Parkinson's disease

Dysfunction of the glymphatic system, an intracranial clearance pathway that drains misfolded proteins, has been implicated in the onset of Parkinson's disease (PD). Recently, the coupling strength of global blood-oxygen-level-dependent (gBOLD) signals and cerebrospinal fluid (CSF) inflow dynamics have been suggested to be an indicator of glymphatic function. Using resting-state functional magnetic resonance imaging (MRI), we quantified gBOLD-CSF coupling strength as the cross-correlation between baseline gBOLD and CSF inflow signals to evaluate glymphatic function and its association with the clinical manifestations of PD. We found that gBOLD-CSF coupling in drug-naïve PD patients was significantly weaker than that in normal controls, but significantly stronger in patients less affected by sleep disturbances than in those more affected by sleep disturbances, based on the PD sleep scale. Furthermore, we collected longitudinal data from patients and found that baseline gBOLD-CSF coupling negatively correlated with the rate of change over time, but positively correlated with the rate of change in UPDRS-III scores. In conclusion, severe gBOLD-CSF decoupling in PD patients may reflect longitudinal motor impairment, thereby providing a potential marker of glymphatic dysfunction in PD.

Polyphenols, Autophagy and Neurodegenerative Diseases: A Review

Polyphenols are secondary metabolites from plant origin and are shown to possess a wide range of therapeutic benefits. They are also reported as regulators of autophagy, inflammation and neurodegeneration. The autophagy pathway is vital in degrading outdated organelles, proteins and other cellular wastes. The dysregulation of autophagy causes proteinopathies, mitochondrial dysfunction and neuroinflammation thereby contributing to neurodegeneration. Evidence reveals that polyphenols improve autophagy by clearing misfolded proteins in the neurons, suppress neuroinflammation and oxidative stress and also protect from neurodegeneration. This review is an attempt to summarize the mechanism of action of polyphenols in modulating autophagy and their involvement in pathways such as mTOR, AMPK, SIRT-1 and ERK. It is evident that polyphenols cause an increase in the levels of autophagic proteins such as beclin-1, microtubule-associated protein light chain (LC3 I and II), sirtuin 1 (SIRT1), etc. Although it is apparent that polyphenols regulate autophagy, the exact interaction of polyphenols with autophagy markers is not known. These data require further research and will be beneficial in supporting polyphenol supplementation as a potential alternative treatment for regulating autophagy in neurodegenerative diseases.

Bioinformatics-based prediction and screening of immunogenic epitopes of Toxoplasma gondii rhoptry proteins 7, 21 and 22 as candidate vaccine target

INTRODUCTION

Toxoplasmosis is a well-known zoonotic disease caused by Toxoplasma gondii. The main causes of the disease range from eating undercooked or contaminated meat and shellfish to cleaning litter trays into which cats that excreted toxoplasma via faeces. This pathogen can live for a very long time, possibly a lifetime, within the bodies of humans and other animals.

AIMS AND OBJECTIVES

This study aimed to predict and analyse candidate immunogenic epitopes for vaccine development by evaluating the physio-chemical properties, multiple sequence alignment, secondary and tertiary structures, phosphorylation sites, transmembrane domains, and signal peptides, of T. gondii rhoptry proteins ROP7, ROP21, and ROP22 using bioinformatics tools.

METHODS

To find immunogenic epitopes of rhoptry proteins, numerous bioinformatics web servers were used containing multiple sequence alignment, physiochemical properties, antigenicity and allergenicity, post-translational modification sites (PTMs), signal peptides, transmembrane domains, secondary and tertiary structures, and screening of predicted epitopes. We evaluated immunogenic linear B-cell epitopes as candidate proteins for vaccine development.

RESULTS

Nine epitopes were identified for each protein, and analysis of immunogenicity, revealed three candidate epitopes for ROP7, one for ROP21, and four for ROP22. Among all candidate epitopes, ROP22 contained the most immunogenic epitopes with immunogenicity score of 0.50575.

CONCLUSION

We acquired detailed information on predicted immunogenic epitopes using in-silico methods. The results provide a foundation for further experimental analysis of toxoplasmosis, and potential vaccine development.

Tau liquid-liquid phase separation is modulated by the Ca2+ -switched chaperone activity of the S100B protein

Aggregation of the microtubule-associated protein tau is implicated in several neurodegenerative tauopathies including Alzheimer's disease (AD). Recent studies evidenced tau liquid-liquid phase separation (LLPS) into droplets as an early event in tau pathogenesis with the potential to enhance aggregation. Tauopathies like AD are accompanied by sustained neuroinflammation and the release of alarmins at early stages of inflammatory responses encompass protective functions. The Ca2+ -binding S100B protein is an alarmin augmented in AD that was recently implicated as a proteostasis regulator acting as a chaperone-type protein, inhibiting aggregation and toxicity through interactions of amyloidogenic clients with a regulatory surface exposed upon Ca2+ -binding. Here we expand the regulatory functions of S100B over protein condensation phenomena by reporting its Ca2+ -dependent activity as a modulator of tau LLPS induced by crowding agents (PEG) and metal ions (Zn2+ ). We observe that apo S100B has a negligible effect on PEG-induced tau demixing but that Ca2+ -bound S100B prevents demixing, resulting in a shift of the phase diagram boundary to higher crowding concentrations. Also, while incubation with apo S100B does not compromise tau LLPS, addition of Ca2+ results in a sharp decrease in turbidity, indicating that interactions with S100B-Ca2+ promote transition of tau to the mixed phase. Further, electrophoretic analysis and FLIM-FRET studies revealed that S100B incorporates into tau liquid droplets, suggesting an important stabilizing and chaperoning role contributing to minimize toxic tau aggregates. Resorting to Alexa488-labeled tau we observed that S100B-Ca2+ reduces the formation of tau fluorescent droplets, without compromising liquid-like behavior and droplet fusion events. The Zn2+ -binding properties of S100B also contribute to regulate Zn2+ -promoted tau LLPS as droplets are decreased by Zn2+ buffering by S100B, in addition to the Ca2+ -triggered interactions with tau. Altogether this work uncovers the versatility of S100B as a proteostasis regulator acting on protein condensation phenomena of relevance across the neurodegeneration continuum.

A general method for quantitative fractionation of mammalian cells

Subcellular fractionation in combination with mass spectrometry-based proteomics is a powerful tool to study localization of key proteins in health and disease. Here we offered a reliable and rapid method for mammalian cell fractionation, tuned for such proteomic analyses. This method proves readily applicable to different cell lines in which all the cellular contents are accounted for, while maintaining nuclear and nuclear envelope integrity. We demonstrated the method's utility by quantifying the effects of a nuclear export inhibitor on nucleoplasmic and cytoplasmic proteomes.

Itraconazole Confers Cytoprotection Against Neurodegenerative Disease-Associated Abnormal Protein Aggregation

Cells perform regular maintenance to avoid the accumulation of misfolded proteins. Prolonged accumulation of these proteotoxic inclusions generates potential risk of ageing-related diseases such as neurodegenerative diseases. Therefore, removal of such abnormal aggregates can ensure the re-establishment of proteostasis. Ubiquitin proteasome system (UPS) actively participates in the selective removal of aberrantly folded clients with the help of complex proteasome machinery. However, specific induction of proteasome functions to remove abnormal proteins remains an open challenge. Here, we show that Itraconazole treatment induces proteasome activities and degrades the accumulation of bonafide-misfolded proteins, including heat-denatured luciferase. Exposure of Itraconazole elevates the degradation of neurodegenerative disease-associated proteins, e.g. expanded polyglutamine, mutant SOD1, and mutant α-synuclein. Our results suggest that Itraconazole treatment prevents the accumulation of neurodegenerative disease-linked misfolded proteins and generates cytoprotection. These findings reveal that Itraconazole removes abnormal proteins through sequential proteasomal activation and represents a potential protective therapeutic role against protein-misfolding neurodegenerative diseases.

Integrated Bioinformatics Analysis of Shared Genes, miRNA, Biological Pathways and Their Potential Role as Therapeutic Targets in Huntington's Disease Stages

Huntington's Disease (HD) is a progressive neurodegenerative disease caused by CAG repeat expansion in the huntingtin gene (HTT). The HTT gene was the first disease-associated gene mapped to a chromosome, but the pathophysiological mechanisms, genes, proteins or miRNAs involved in HD remain poorly understood. Systems bioinformatics approaches can divulge the synergistic relationships of multiple omics data and their integration, and thus provide a holistic approach to understanding diseases. The purpose of this study was to identify the differentially expressed genes (DEGs), HD-related gene targets, pathways and miRNAs in HD and, more specifically, between the pre-symptomatic and symptomatic HD stages. Three publicly available HD datasets were analysed to obtain DEGs for each HD stage from each dataset. In addition, three databases were used to obtain HD-related gene targets. The shared gene targets between the three public databases were compared, and clustering analysis was performed on the common shared genes. Enrichment analysis was performed on (i) DEGs identified for each HD stage in each dataset, (ii) gene targets from the public databases and (iii) the clustering analysis results. Furthermore, the hub genes shared between the public databases and the HD DEGs were identified, and topological network parameters were applied. Identification of HD-related miRNAs and their gene targets was obtained, and a miRNA-gene network was constructed. Enriched pathways identified for the 128 common genes revealed pathways linked to multiple neurodegeneration diseases (HD, Parkinson's disease, Spinocerebellar ataxia), MAPK and HIF-1 signalling pathways. Eighteen HD-related hub genes were identified based on network topological analysis of MCC, degree and closeness. The highest-ranked genes were FoxO3 and CASP3, CASP3 and MAP2 were found for betweenness and eccentricity and CREBBP and PPARGC1A were identified for the clustering coefficient. The miRNA-gene network identified eleven miRNAs (mir-19a-3p, mir-34b-3p, mir-128-5p, mir-196a-5p, mir-34a-5p, mir-338-3p, mir-23a-3p and mir-214-3p) and eight genes (ITPR1, CASP3, GRIN2A, FoxO3, TGM2, CREBBP, MTHFR and PPARGC1A). Our work revealed that various biological pathways seem to be involved in HD either during the pre-symptomatic or symptomatic stages of HD. This may offer some clues for the molecular mechanisms, pathways and cellular components underlying HD and how these may act as potential therapeutic targets for HD.

The interactions of amyloid β aggregates with phospholipid membranes and the implications for neurodegeneration

Misfolding, aggregation and accumulation of Amyloid-β peptides (Aβ) in neuronal tissue and extracellular matrix are hallmark features of Alzheimer's disease (AD) pathology. Soluble Aβ oligomers are involved in neuronal toxicity by interacting with the lipid membrane, compromising its integrity, and affecting the function of receptors. These facts indicate that the interaction between Aβ oligomers and cell membranes may be one of the central molecular level factors responsible for the onset of neurodegeneration. The present review provides a structural understanding of Aβ neurotoxicity via membrane interactions and contributes to understanding early events in Alzheimer's disease.

Chemical Modifications and Design Influence the Potency of Huntingtin Anti-Gene Oligonucleotides

Huntington's disease is a neurodegenerative, trinucleotide repeat (TNR) disorder affecting both males and females. It is caused by an abnormal increase in the length of CAG•CTG TNR in exon 1 of the Huntingtin gene (HTT). The resultant, mutant HTT mRNA and protein cause neuronal toxicity, suggesting that reduction of their levels would constitute a promising therapeutic approach. We previously reported a novel strategy in which chemically modified oligonucleotides (ONs) directly target chromosomal DNA. These anti-gene ONs were able to downregulate both HTT mRNA and protein. In this study, various locked nucleic acid (LNA)/DNA mixmer anti-gene ONs were tested to investigate the effects of varying ON length, LNA content, and fatty acid modification on HTT expression. Altering the length did not significantly influence the ON potency, while LNA content was critical for activity. Utilization of palmitoyl-modified LNA monomers enhanced the ON activity relatively to the corresponding nonmodified LNA under serum starvation conditions. Furthermore, the number of palmitoylated LNA monomers and their positioning greatly affected ON potency. In addition, we performed RNA sequencing analysis, which showed that the anti-gene ONs affect the "immune system process, mRNA processing, and neurogenesis." Furthermore, we observed that for repeat containing genes, there is a higher tendency for antisense off-targeting. Taken together, our findings provide an optimized design of anti-gene ONs that could potentially be developed as DNA-targeting therapeutics for this class of TNR-related diseases.

Effect of the Enrichment in c-Kit Stem Cell Potential of Foetal Human Amniotic Fluid Cells: Characterization from Single Cell Analysis to the Secretome Content

Human amniotic fluid cells (hAFSCs) are a fascinating foetal cell-type that have important stem cell characteristics; however, they are a heterogeneous population that ranges from totally differentiated or progenitor cells to highly multipotent stem cells. There is no single approach to isolating the stem cell component, but the selection of a subpopulation of hAFSCs expressing c-Kit is widely employed, while a deep characterization of the two populations is still lacking. Here we performed single-cell and bulk RNAseq analysis to compare the gene expression profiles of adherent amniotic fluid cells and their subpopulation c-Kit⁺. Information deriving from this high throughput technology on the transcriptome was then confirmed for specific targets with protein expression experiments and functional analysis. In particular, transcriptome profiling identified changes in cellular distribution among the different clusters that correlated with significant differential expression in pathways related to stemness, proliferation, and cell cycle checkpoints. These differences were validated by RT-PCR, immunofluorescence, WB, and cell cycle assays. Interestingly, the two populations produced secretomes with different immune-modulating and pro-regenerative potentials. Indeed, the presence of TGFβ, HGF, IDO was higher in EVs deriving from c-Kit⁺ cells, unlike IL-6. These results suggest the existence of deep intra-population differences that can influence the stemness profile of hAFSCs. This study represents a proof-of-concept of the importance of selecting c-Kit positive fractions with higher potential in regenerative medicine applications.

Gene Alterations Induced by Glutamine (Q) Encoding CAG Repeats Associated with Neurodegeneration

Several studies have been reported linking the role of polyglutamine (polyQ) disease-associated proteins with altered gene regulation induced by an unstable trinucleotide (CAG) repeat. Owing to their dynamic nature of expansion, these DNA repeats form secondary structures interfering with the normal cellular mechanisms like replication and transcription and, thereby, have become the underlying cause of numerous neurodegenerative disorders involving mental retardation and/or muscular or neuronal degeneration. Despite the widespread expression of the disease-causing protein, specific subsets of neurons are susceptible to specific patterns of inheritance and clinical symptoms. Although this cell-type selectivity is still elusive and less understood, it has been found that aberrant transcriptional regulation is one of the primary causes of polyQ diseases where the functions of histone-modifying complexes are disrupted. Besides, epigenetic modifications play a critical role in the pathogenesis of these diseases. In this chapter, we will be delving into how these polyQ repeats induce the self-assembly and aggregation of altered carrier proteins based on gene alterations, causing neuronal toxicity and cellular deaths. Besides, genomic instability in CAG repeats due to altered chromatin-related enzymes will be highlighted, along with epigenetic changes present in many polyQ disorders. Understanding the underlying molecular mechanisms in the root cause of these disorders will culminate in identifying therapeutic approaches for the treatment of these neurodegenerative disorders.

Protein misfolding and related human diseases: A comprehensive review of toxicity, proteins involved, and current therapeutic strategies

Most of the cell's chemical reactions and structural components are facilitated by proteins. But proteins are highly dynamic molecules, where numerous modifications or changes in the cellular environment can affect their native conformational fold leading to protein aggregation. Various stress conditions, such as oxidative stress, mutations and metal toxicity may cause protein misfolding and aggregation by shifting the conformational equilibrium towards more aggregation-prone states. Most of the protein misfolding diseases (PMDs) involve aggregation of protein. We have discussed such proteins like Aβ peptide, α-synuclein, amylin and lysozyme involved in Alzheimer's, Parkinson's, type II diabetes and non-neuropathic systemic amyloidosis respectively. Till date, all advances in PMDs therapeutics help symptomatically but do not prevent the root cause of the disease, i.e., the aggregation of protein involved in the diseases. Current efforts focused on developing therapies for PMDs have employed diverse strategies; repositioning pre-existing drugs as it saves time and money; natural compounds that are touted as potential drug candidates have an advantage of being taken in diet normally and will induce lesser side effects. This review also covers recently developed therapeutic strategies like antisense drugs and disaggregases which has yielded therapeutic agents that have transitioned from preclinical studies into human clinical trials.

CBP-Mediated Acetylation of Importin α Mediates Calcium-Dependent Nucleocytoplasmic Transport of Selective Proteins in Drosophila Neurons

For proper function of proteins, their subcellular localization needs to be monitored and regulated in response to the changes in cellular demands. In this regard, dysregulation in the nucleocytoplasmic transport (NCT) of proteins is closely associated with the pathogenesis of various neurodegenerative diseases. However, it remains unclear whether there exists an intrinsic regulatory pathway(s) that controls NCT of proteins either in a commonly shared manner or in a target-selectively different manner. To dissect between these possibilities, in the current study, we investigated the molecular mechanism regulating NCT of truncated ataxin-3 (ATXN3) proteins of which genetic mutation leads to a type of polyglutamine (polyQ) diseases, in comparison with that of TDP-43. In Drosophila dendritic arborization (da) neurons, we observed dynamic changes in the subcellular localization of truncated ATXN3 proteins between the nucleus and the cytosol during development. Moreover, ectopic neuronal toxicity was induced by truncated ATXN3 proteins upon their nuclear accumulation. Consistent with a previous study showing intracellular calcium-dependent NCT of TDP-43, NCT of ATXN3 was also regulated by intracellular calcium level and involves Importin α3 (Imp α3). Interestingly, NCT of ATXN3, but not TDP-43, was primarily mediated by CBP. We further showed that acetyltransferase activity of CBP is important for NCT of ATXN3, which may acetylate Imp α3 to regulate NCT of ATXN3. These findings demonstrate that CBP-dependent acetylation of Imp α3 is crucial for intracellular calcium-dependent NCT of ATXN3 proteins, different from that of TDP-43, in Drosophila neurons.

SYK coordinates neuroprotective microglial responses in neurodegenerative disease

Recent studies have begun to reveal critical roles for the brain's professional phagocytes, microglia, and their receptors in the control of neurotoxic amyloid beta (Aβ) and myelin debris accumulation in neurodegenerative disease. However, the critical intracellular molecules that orchestrate neuroprotective functions of microglia remain poorly understood. In our studies, we find that targeted deletion of SYK in microglia leads to exacerbated Aβ deposition, aggravated neuropathology, and cognitive defects in the 5xFAD mouse model of Alzheimer's disease (AD). Disruption of SYK signaling in this AD model was further shown to impede the development of disease-associated microglia (DAM), alter AKT/GSK3β-signaling, and restrict Aβ phagocytosis by microglia. Conversely, receptor-mediated activation of SYK limits Aβ load. We also found that SYK critically regulates microglial phagocytosis and DAM acquisition in demyelinating disease. Collectively, these results broaden our understanding of the key innate immune signaling molecules that instruct beneficial microglial functions in response to neurotoxic material.

Does the Gut Microbial Metabolome Really Matter? The Connection between GUT Metabolome and Neurological Disorders

Herein we gathered updated knowledge regarding the alterations of gut microbiota (dysbiosis) and its correlation with human neurodegenerative and brain-related diseases, e.g., Alzheimer’s and Parkinson’s. This review underlines the importance of gut-derived metabolites and gut metabolic status as the main players in gut-brain crosstalk and their implications on the severity of neural conditions. Scientific evidence indicates that the administration of probiotic bacteria exerts beneficial and protective effects as reduced systemic inflammation, neuroinflammation, and inhibited neurodegeneration. The experimental results performed on animals, but also human clinical trials, show the importance of designing a novel microbiota-based probiotic dietary supplementation with the aim to prevent or ease the symptoms of Alzheimer’s and Parkinson’s diseases or other forms of dementia or neurodegeneration.

Senegenin alleviates Aβ1-42 induced cell damage through triggering mitophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Senegenin (SEN), an active compound extracted from the traditional Chinese herb Polygala tenuifolia Willd. (a species in the genus Polygala, family Polygalaceae), could nourish neurons and resist neuronal damage in mouse models of Alzheimer's disease (AD). Amyloid-β (Aβ) depositions in neuronal cells may cause pathological changes such as oxidative stress which one return could cause severe damage to mitochondria in AD patients or animal models. Mitophagy is an important mechanism to selectively remove damaged mitochondria. In neurons, this process is mainly mediated by PTEN-induced putative kinase 1 (PINK1)/Parkin pathway. Previous studies have shown that SEN could reduce mitochondrial damage and inhibit apoptosis in neurons. Therefore, this study speculated that SEN might activate mitophagy to clear damaged mitochondria, thereby mitigating Aβ-induced cell damage in neuronal cells.

AIM OF THE STUDY

This study aimed to determine the effects of SEN on Aβ-induced cell damage, and further to explore whether SEN could induce mitophagy. Moreover, the regulatory role of mitophagy in the neuroptrotective effect of SEN would be elucidated.

MATERIALS AND METHODS

This study established an in vitro cell damage model using Aβ_1-42 to treat mouse hippocampal neuron HT22 cells. The effects of SEN on cell damage were determined by MTT assay and lactate dehydrogenase (LDH) release assay. Reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were detected by Cytation™5 cell imaging microplate detection system. The apoptotic rate was analyzed by flow cytometry. The effects of SEN on mitophagy were detected by transmission electron microscope, immunofluorescence and immunoblotting.

RESULTS

Firstly, HT22 cells were treated with 30 μM Aβ_1-42 for 24 h to establish the damage model. It was found that 30 μM Aβ_1-42 caused neuronal damages as evidenced by reduced cell viability, increased LDH release and ROS, collapsed MMP and elevated apoptosis. Secondly, Aβ_1-42-incubated cells were treated with 10, 20, 40 and 60 μM SEN for 24 h. SEN significantly reduced the damage of Aβ_1-42-incubated cells as shown by recovered cell viability and MMP, reduced apoptosis and ROS. Notably, SEN induced the formation of mitophagosomes and mitolysosomes, and elevated the conversion of LC3 I to LC3 II. Moreover, SEN down-regulated the expression of p62, promoted the accumulation of full-length PINK1 and the translocation of Parkin to mitochondria, decreased the expression of mitochondrial matrix protein HSP60, thus activating the PINK1/Parkin-mediated mitophagy. However, when cells were pretreated with 5 μM CsA (Cyclosporine A, a mitophagy inhibitor) for 2 h and then co-treated with 20 and 40 μM SEN for 24 h, the protective effects of SEN were compromised.

CONCLUSIONS

The present study demonstrated that SEN could alleviate Aβ_1-42-induced cell damage through PINK1/Parkin-mediated mitophagy. Our findings justify the traditional use of P. tenuifolia in China with anti-aging or anti-neurodegenerative effects.

The Proteasome Activator PA200/PSME4: An Emerging New Player in Health and Disease

Proteasomes comprise a family of proteasomal complexes essential for maintaining protein homeostasis. Accordingly, proteasomes represent promising therapeutic targets in multiple human diseases. Several proteasome inhibitors are approved for treating hematological cancers. However, their side effects impede their efficacy and broader therapeutic applications. Therefore, understanding the biology of the different proteasome complexes present in the cell is crucial for developing tailor-made inhibitors against specific proteasome complexes. Here, we will discuss the structure, biology, and function of the alternative Proteasome Activator 200 (PA200), also known as PSME4, and summarize the current evidence for its dysregulation in different human diseases. We hereby aim to stimulate research on this enigmatic proteasome regulator that has the potential to serve as a therapeutic target in cancer.

Cellular Therapy Using Epitope-Imprinted Composite Nanoparticles to Remove α-Synuclein from an In Vitro Model

Several degenerative disorders of the central nervous system, including Parkinson’s disease (PD), are related to the pathological aggregation of proteins. Antibodies against toxic disease proteins, such as α-synuclein (SNCA), are therefore being developed as possible therapeutics. In this work, one peptide (YVGSKTKEGVVHGVA) from SNCA was used as the epitope to construct magnetic molecularly imprinted composite nanoparticles (MMIPs). These composite nanoparticles were characterized by dynamic light scattering (DLS), high-performance liquid chromatography (HPLC), isothermal titration calorimetry (ITC), Brunauer–Emmett–Teller (BET) analysis, and superconducting quantum interference device (SQUID) analysis. Finally, the viability of brain endothelial cells that were treated with MMIPs was measured, and the extraction of SNCA from CRISPR/dCas9a-activated HEK293T cells from the in vitro model system was demonstrated for the therapeutic application of MMIPs.

Machine learning predicts translation initiation sites in neurologic diseases with nucleotide repeat expansions

A number of neurologic diseases associated with expanded nucleotide repeats, including an inherited form of amyotrophic lateral sclerosis, have an unconventional form of translation called repeat-associated non-AUG (RAN) translation. It has been speculated that the repeat regions in the RNA fold into secondary structures in a length-dependent manner, promoting RAN translation. Repeat protein products are translated, accumulate, and may contribute to disease pathogenesis. Nucleotides that flank the repeat region, especially ones closest to the initiation site, are believed to enhance translation initiation. A machine learning model has been published to help identify ATG and near-cognate translation initiation sites; however, this model has diminished predictive power due to its extensive feature selection and limited training data. Here, we overcome this limitation and increase prediction accuracy by the following: a) capture the effect of nucleotides most critical for translation initiation via feature reduction, b) implement an alternative machine learning algorithm better suited for limited data, c) build comprehensive and balanced training data (via sampling without replacement) that includes previously unavailable sequences, and d) split ATG and near-cognate translation initiation codon data to train two separate models. We also design a supplementary scoring system to provide an additional prognostic assessment of model predictions. The resultant models have high performance, with ~85-88% accuracy, exceeding that of the previously published model by >18%. The models presented here are used to identify translation initiation sites in genes associated with a number of neurologic repeat expansion disorders. The results confirm a number of sites of translation initiation upstream of the expanded repeats that have been found experimentally, and predict sites that are not yet established.

TBK1 haploinsufficiency results in changes in the K63-ubiquitination profiles in brain and fibroblasts from affected and presymptomatic mutation carriers

BACKGROUND

Frontotemporal dementia (FTD) is a neurodegenerative disease, resulting in progressive problems in language and/or behaviour and is often diagnosed before 65 years of age. Ubiquitin positive protein aggregates in the brain are among the key pathologic hallmarks of frontotemporal lobar degeneration (FTLD) postmortem. The TANK-binding kinase 1 gene (TBK1) is on the list of genes that can contribute to the development of FTD as well as the related neurodegenerative disease amyotrophic lateral sclerosis (ALS).

METHODS

In this study, using an array of clinical and neuropathological data combined with biochemical and proteomics assays, we analyze the TBK1 splice-mutation (c.1340 + 1G > A) in a Swedish family with a history of FTD and ALS. We also explore the K63 ubiquitination landscape in post-mortem brain tissue and fibroblast cultures.

RESULTS

The intronic (c.1340 + 1G > A) mutation in TBK1 results in haploinsufficiency and affects the activity of the protein in symptomatic and pre-symptomatic mutation carriers.

CONCLUSION

Our results suggest that the mutation leads to a significant reduction of TBK1 activity and induce alterations in K63 ubiquitination profile of the cell already in the presymptomatic stages.

Deciphering the Structure and Formation of Amyloids in Neurodegenerative Diseases With Chemical Biology Tools

Protein aggregation into highly ordered, regularly repeated cross-β sheet structures called amyloid fibrils is closely associated to human disorders such as neurodegenerative diseases including Alzheimer's and Parkinson's diseases, or systemic diseases like type II diabetes. Yet, in some cases, such as the HET-s prion, amyloids have biological functions. High-resolution structures of amyloids fibrils from cryo-electron microscopy have very recently highlighted their ultrastructural organization and polymorphisms. However, the molecular mechanisms and the role of co-factors (posttranslational modifications, non-proteinaceous components and other proteins) acting on the fibril formation are still poorly understood. Whether amyloid fibrils play a toxic or protective role in the pathogenesis of neurodegenerative diseases remains to be elucidated. Furthermore, such aberrant protein-protein interactions challenge the search of small-molecule drugs or immunotherapy approaches targeting amyloid formation. In this review, we describe how chemical biology tools contribute to new insights on the mode of action of amyloidogenic proteins and peptides, defining their structural signature and aggregation pathways by capturing their molecular details and conformational heterogeneity. Challenging the imagination of scientists, this constantly expanding field provides crucial tools to unravel mechanistic detail of amyloid formation such as semisynthetic proteins and small-molecule sensors of conformational changes and/or aggregation. Protein engineering methods and bioorthogonal chemistry for the introduction of protein chemical modifications are additional fruitful strategies to tackle the challenge of understanding amyloid formation.

Nerve Growth Factor is a Potential Treated Target in Tg(SOD1*G93A)1Gur Mice

Nerve growth factor (NGF) is a protective factor of neural cells; the possible relationship between the NGF and the pathogenesis of amyotrophic lateral sclerosis (ALS) hasn't been completely known. In this study, we observed and analyzed the expression and distribution of NGF, as well as the possible relationship between the NGF expression and distribution and the neural cell death in both SOD1 wild-type (WT) and Tg(SOD1*G93A)1Gur (TG) mice applying the fluorescence immunohistochemistry method. The results showed that the expression and distribution of NGF in the anterior horn (AH), the lateral horn (LH), and the surrounding central canal (CC) significantly increased at the supper early stage of ALS (Pre-onset stage) and the early stage (Onset stage), but the NGF expression and distribution in the AH, the LH, and the surrounding CC significantly reduced at the progression stage. The astrocyte, neuron, and oligodendrocyte produced the NGF and the neural precursor cells (NPCs) produced the NGF. The neural cell death gradually increased accompanying with the reduction of NGF expression and distribution. Our data suggested that the NGF was a protective factor of neural cells, because the neural cells in the AH, the LH, and the surrounding CC produced more NGF at the supper early and early stage of ALS; moreover, the NPCs produced the NGF. It implied that the NGF exerted the protective effect of neural cells, prevented from the neural cell death and aroused the potential of self-repair in the development of ALS.

Targeted protein degradation: mechanisms, strategies and application

Traditional drug discovery mainly focuses on direct regulation of protein activity. The development and application of protein activity modulators, particularly inhibitors, has been the mainstream in drug development. In recent years, PROteolysis TArgeting Chimeras (PROTAC) technology has emerged as one of the most promising approaches to remove specific disease-associated proteins by exploiting cells’ own destruction machinery. In addition to PROTAC, many different targeted protein degradation (TPD) strategies including, but not limited to, molecular glue, Lysosome-Targeting Chimaera (LYTAC), and Antibody-based PROTAC (AbTAC), are emerging. These technologies have not only greatly expanded the scope of TPD, but also provided fresh insights into drug discovery. Here, we summarize recent advances of major TPD technologies, discuss their potential applications, and hope to provide a prime for both biologists and chemists who are interested in this vibrant field.

Neuroprotective activities of acai berries (Euterpe sp.): A review

Dietary interventions rich in fruits and vegetables in aging people can reverse or mitigate age-related cognitive declines, delay the onset of neurodegenerative diseases (NDDs), and provide long-term health dividends. The novel food, popularly known as "Acai", is a berry belonging to the Euterpe genus of tropical palms trees and natively found in South America. Euterpe oleracea has been given much attention among scientists due to its high antioxidant capacity compared to other fruits and berries. Additionally, acai pulp composition analysis found that it contains various biologically active phytochemicals. In this review, we focused on current evidence relating to acai berry neuroprotection mechanisms and its efficacy in preventing or reversing neurodegeneration and age-related cognitive decline. A number of studies have illustrated the potential neuroprotective properties of acai berries. They have shown that their chemical extracts have antioxidant and anti-inflammatory properties and maintain proteins, calcium homeostasis, and mitochondrial function. Moreover, acai berry extract offers other neuromodulatory mechanisms, including anticonvulsant, antidepressant, and anti-aging properties. This neuromodulation gives valuable insights into the acai pulp and its considerable pharmacological potential on critical brain areas involved in memory and cognition. The isolated chemical matrix of acai berries could be a new substitute in research for NDD medicine development. However, due to the limited number of investigations, there is a need for further efforts to establish studies that enable progressing to clinical trials to consequently prove and ratify the therapeutic potential of this berry for several incurable NDDs.

The Involvement of RAGE and Its Ligands during Progression of ALS in SOD1 G93A Transgenic Mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a progressive degeneration of upper and lower motor neurons that causes paralysis and muscle atrophy. The pathogenesis of the disease is still not elucidated. Receptor for Advanced Glycation End Product (RAGE) is a major component of the innate immune system and has implications in ALS pathogenesis. Multiple studies suggest the role of RAGE and its ligands in ALS. RAGE and its ligands are overexpressed in human and murine ALS motor neurons, astrocytes, and microglia. Here, we demonstrated the expression of RAGE and its ligands during the progression of the disease in the transgenic SOD1 G93A mouse lumbar spinal cord. We observed the highest expression of HMGB1 and S100b proteins at ALS onset. Our results highlight the potential role of RAGE and its ligands in ALS pathogenesis and suggest that some of the RAGE ligands might be used as biomarkers in early ALS diagnosis and potentially be useful in targeted therapeutic interventions at the early stage of this devastating disease.

Autophagy-independent cytoprotection by optineurin from toxicity of aggregates formed by mutant huntingtin and mutant ataxin-3

An important feature of several neurodegenerative diseases is the formation of pathological structures containing aggregated proteins. The autophagy receptor optineurin/OPTN is frequently observed in these structures. The role played by optineurin in these aggregates is not clear. In this study, we explored whether optineurin has a cytoprotective role in the cells having mutant protein aggregates. We overexpressed mutant huntingtin having 97 glutamine repeats (mHtt), and mutant ataxin-3 having 130 glutamine repeats (mAtax-3) in wild-type and optineurin-deficient neuronal (N2A) and non-neuronal cells (Optn-/- mouse embryonic fibroblasts), and determined the percentage of dead cells with mutant protein aggregates. Optineurin-deficient cells having mHtt or mAtax-3 aggregates showed higher cell death as compared to wild-type cells having mutant protein aggregates. Confocal microscopy revealed that optineurin formed a shell around mHtt and mAtax-3 aggregates through its C-terminal domain. The C-terminal domain of optineurin, which lacks LC3-interacting region required for autophagy, was necessary and sufficient to reduce cytotoxicity of mHtt and mAtax-3 aggregates. Our results show that in the absence of optineurin, mutant protein aggregates are highly toxic, revealing an autophagy-independent cytoprotective function of optineurin, which is mediated by its C-terminal domain.

Advances in Proteomic and Metabolomic Profiling of Neurodegenerative Diseases

Proteomics and metabolomics are two emerging fields that hold promise to shine light on the molecular mechanisms causing neurodegenerative diseases. Research in this area may reveal and quantify specific metabolites and proteins that can be targeted by therapeutic interventions intended at halting or reversing the neurodegenerative process. This review aims at providing a general overview on the current status of proteomic and metabolomic profiling in neurodegenerative diseases. We focus on the most common neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. We discuss the relevance of state-of-the-art metabolomics and proteomics approaches and their potential for biomarker discovery. We critically review advancements made so far, highlighting how metabolomics and proteomics may have a significant impact in future therapeutic and biomarker development. Finally, we further outline technologies used so far as well as challenges and limitations, placing the current information in a future-facing context.

Quality control of cytoplasmic proteins inside the nucleus

A complex network of molecular chaperones and proteolytic machinery safeguards the proteins which comprise the proteome, from the time they are synthesized on ribosomes to their destruction via proteolysis. Impaired protein quality control results in the accumulation of aberrant proteins, which may undergo unwanted spurious interactions with other proteins, thereby interfering with a broad range of cellular functions. To protect the cellular environment, such proteins are degraded or sequestered into inclusions in different subcellular compartments. Recent findings demonstrate that aberrant or mistargeted proteins from different cytoplasmic compartments are removed from their environment by transporting them into the nucleus. These proteins are degraded by the nuclear ubiquitin–proteasome system or sequestered into intra-nuclear inclusions. Here, we discuss the emerging role of the nucleus as a cellular quality compartment based on recent findings in the yeast Saccharomyces cerevisiae. We describe the current knowledge on cytoplasmic substrates of nuclear protein quality control, the mechanism of nuclear import of such proteins, as well as possible advantages and risks of nuclear sequestration of aberrant proteins.

Polyglutamine-Specific Gold Nanoparticle Complex Alleviates Mutant Huntingtin-Induced Toxicity

Huntington's disease (HD) belongs to protein misfolding disorders associated with polyglutamine (polyQ)-rich mutant huntingtin (mHtt) protein inclusions. Currently, it is indicated that the aggregation of polyQ-rich mHtt participates in neuronal toxicity and dysfunction. Here, we designed and synthesized a polyglutamine-specific gold nanoparticle (AuNP) complex, which specifically targeted mHtt and alleviated its toxicity. The polyglutamine-specific AuNPs were prepared by decorating the surface of AuNPs with an amphiphilic peptide (JLD1) consisting of both polyglutamine-binding sequences and negatively charged sequences. By applying the polyQ aggregation model system, we demonstrated that AuNPs-JLD1 dissociated the fibrillary aggregates from the polyQ peptide and reduced its β-sheet content in a concentration-dependent manner. By further integrating polyethyleneimine (PEI) onto AuNPs-JLD1, we generated a complex (AuNPs-JLD1-PEI). We showed that this complex could penetrate cells, bind to cytosolic mHtt proteins, dissociate mHtt inclusions, reduce mHtt oligomers, and ameliorate mHtt-induced toxicity. AuNPs-JLD1-PEI was also able to be transported to the brain and improved the functional deterioration in the HD Drosophila larva model. Our results revealed the feasibility of combining AuNPs, JLD1s, and cell-penetrating polymers against mHtt protein aggregation and oligomerization, which hinted on the early therapeutic strategies against HD.

Phosphoinositide-3-kinase regulatory subunit 4 participates in the occurrence and development of amyotrophic lateral sclerosis by regulating autophagy

The development of amyotrophic lateral sclerosis (ALS) may be related to the abnormal alterations of multiple proteins. Our previous study revealed that the expression of phosphoinositide-3-kinase regulatory subunit 4 (PIK3R4) was decreased in ALS. However, the role of PIK3R4 in ALS pathogenesis remains unknown. This study was the first to find that transfection of PC12 cells with small interfering RNA against the PIK3R4 gene significantly decreased the expression levels of PIK3R4 and the autophagy-related proteins p62 and LC3. Additionally, in vivo experiments revealed that the PIK3R4 protein was extensively expressed in the anterior horn, posterior horn, central canal, and areas surrounding the central canal in cervical, thoracic, and lumbar segments of the spinal cord in adult mice. PIK3R4 protein was mainly expressed in the neurons within the spinal lumbar segments. PIK3R4 and p62 expression levels were significantly decreased at both the pre-onset and onset stages of ALS disease in Tg(SOD1*G93A)1Gur mice compared with control mice, but these proteins were markedly increased at the progression stage. LC3 protein expression did not change during progression of ALS. These findings suggest that PIK3R4 likely participates in the prevention of ALS progression. This study was approved by the Ethics Committee for Animal Care and Use of Jiangxi Provincial People's Hospital, Affiliated People's Hospital of Nanchang University (approval No. 2020025) on March 26, 2020.

Mitochondria-Endoplasmic Reticulum Crosstalk in Parkinson's Disease: The Role of Brain Renin Angiotensin System Components

The past few decades have seen an increased emphasis on the involvement of the mitochondrial-associated membrane (MAM) in various neurodegenerative diseases, particularly in Parkinson's disease (PD) and Alzheimer's disease (AD). In PD, alterations in mitochondria, endoplasmic reticulum (ER), and MAM functions affect the secretion and metabolism of proteins, causing an imbalance in calcium homeostasis and oxidative stress. These changes lead to alterations in the translocation of the MAM components, such as IP3R, VDAC, and MFN1 and 2, and consequently disrupt calcium homeostasis and cause misfolded proteins with impaired autophagy, distorted mitochondrial dynamics, and cell death. Various reports indicate the detrimental involvement of the brain renin-angiotensin system (RAS) in oxidative stress, neuroinflammation, and apoptosis in various neurodegenerative diseases. In this review, we attempted to update the reports (using various search engines, such as PubMed, SCOPUS, Elsevier, and Springer Nature) demonstrating the pathogenic interactions between the various proteins present in mitochondria, ER, and MAM with respect to Parkinson's disease. We also made an attempt to speculate the possible involvement of RAS and its components, i.e., AT1 and AT2 receptors, angiotensinogen, in this crosstalk and PD pathology. The review also collates and provides updated information on the role of MAM in calcium signaling, oxidative stress, neuroinflammation, and apoptosis in PD.