Protein aggregate spreading in neurodegenerative diseases: problems and perspectives

Effects of an OX2R agonist on migration and removal of tau from mouse brain

Pathological proteins including tau are produced in neurons and released into interstitial fluid (ISF) in a neural activity-dependent manner during wakefulness. Pathological proteins in ISF can be removed from the brain via the glymphatic pathway during nighttime. Thus, in individuals with Alzheimer's disease (AD) that have dysregulated sleep/wake rhythm, application of orexin receptor 2 (OX2R) agonists during daytime could recover the efflux of pathological proteins to ISF and indirectly promote the glymphatic pathway by improving the quality of nighttime sleep after proper daytime arousal, resulting in increased removal of these proteins from the brain. We investigated this hypothesis using OX-201, a novel OX2R-selective agonist with a 50% effective concentration of 8.0 nM. Diurnal rhythm of tau release into hippocampal ISF correlated well with neuronal activity and wakefulness in wild-type mice. In both wild-type and human P301S tau transgenic mice, OX-201 induced wakefulness and promoted tau release into hippocampal ISF. Human P301S tau transgenic mice, tested under our conditions, showed longer wakefulness time, which differs from individuals with AD. OX-201 treatment over 2 months did not alter hippocampal tau levels. Although further studies are required, at a minimum OX2R agonists may not exacerbate tau accumulation in individuals with tauopathy, including AD.

Executive Summary of 2023 International Conference of the Korean Dementia Association (IC-KDA 2023): A Report From the Academic Committee of the Korean Dementia Association

The Korean Dementia Association (KDA) has been organizing biennial international academic conferences since 2019, with the International Conference of the KDA (IC-KDA) 2023 held in Busan under the theme 'Beyond Boundaries: Advancing Global Dementia Solutions.' The conference comprised 6 scientific sessions, 3 plenary lectures, and 4 luncheon symposiums, drawing 804 participants from 35 countries. Notably, a Korea-Taiwan Joint Symposium addressed insights into Alzheimer's disease (AD). Plenary lectures by renowned scholars explored topics such as microbiome-related AD pathogenesis, social cognition in neurodegenerative diseases, and genetic frontotemporal dementia (FTD). On the first day, specific presentations covered subjects like the gut-brain axis and neuroinflammation in dementia, blood-based biomarkers in AD, and updates in AD therapeutics. The second day's presentations addressed recent issues in clinical neuropsychology, FTD cohort studies, and the pathogenesis of non-AD dementia. The Academic Committee of the KDA compiles lecture summaries to provide comprehensive understanding of the advanced dementia knowledge presented at IC-KDA 2023.

Microbiota, Tryptophan and Aryl Hydrocarbon Receptors as the Target Triad in Parkinson's Disease-A Narrative Review

In the era of a steadily increasing lifespan, neurodegenerative diseases among the elderly present a significant therapeutic and socio-economic challenge. A properly balanced diet and microbiome diversity have been receiving increasing attention as targets for therapeutic interventions in neurodegeneration. Microbiota may affect cognitive function, neuronal survival and death, and gut dysbiosis was identified in Parkinson's disease (PD). Tryptophan (Trp), an essential amino acid, is degraded by microbiota and hosts numerous compounds with immune- and neuromodulating properties. This broad narrative review presents data supporting the concept that microbiota, the Trp-kynurenine (KYN) pathway and aryl hydrocarbon receptors (AhRs) form a triad involved in PD. A disturbed gut-brain axis allows the bidirectional spread of pro-inflammatory molecules and α-synuclein, which may contribute to the development/progression of the disease. We suggest that the peripheral levels of kynurenines and AhR ligands are strongly linked to the Trp metabolism in the gut and should be studied together with the composition of the microbiota. Such an approach can clearly delineate the sub-populations of PD patients manifesting with a disturbed microbiota-Trp-KYN-brain triad, who would benefit from modifications in the Trp metabolism. Analyses of the microbiome, Trp-KYN pathway metabolites and AhR signaling may shed light on the mechanisms of intestinal distress and identify new targets for the diagnosis and treatment in early-stage PD. Therapeutic interventions based on the combination of a well-defined food regimen, Trp and probiotics seem of potential benefit and require further experimental and clinical research.

A comprehensive review on therapeutic potentials of photobiomodulation for neurodegenerative disorders

A series of experimental trials over the past two centuries has put forth Photobiomodulation (PBM) as a treatment modality that utilizes colored lights for various conditions. While in its cradle, PBM was used for treating simple conditions such as burns and wounds, advancements in recent years have extended the use of PBM for treating complex neurodegenerative diseases (NDDs). PBM has exhibited the potential to curb several symptoms and signs associated with NDDs. While several of the currently used therapeutics cause adverse side effects alongside being highly invasive, PBM on the contrary, seems to be broad-acting, less toxic, and non-invasive. Despite being projected as an ideal therapeutic for NDDs, PBM still isn't considered a mainstream treatment modality due to some of the challenges and knowledge gaps associated with it. Here, we review the advantages of PBM summarized above with an emphasis on the common mechanisms that underlie major NDDs and how PBM helps tackle them. We also discuss important questions such as whether PBM should be considered a mainstay treatment modality for these conditions and if PBM's properties can be harnessed to develop prophylactic therapies for high-risk individuals and also highlight important animal studies that underscore the importance of PBM and the challenges associated with it. Overall, this review is intended to bring the major advances made in the field to the spotlight alongside addressing the practicalities and caveats to develop PBM as a major therapeutic for NDDs.

In Silico Structural Analysis Exploring Conformational Folding of Protein Variants in Alzheimer's Disease

Accurate protein structure prediction using computational methods remains a challenge in molecular biology. Recent advances in AI-powered algorithms provide a transformative effect in solving this problem. Even though AlphaFold's performance has improved since its release, there are still limitations that apply to its efficacy. In this study, a selection of proteins related to the pathology of Alzheimer's disease was modeled, with Presenilin-1 (PSN1) and its mutated variants in the foreground. Their structural predictions were evaluated using the ColabFold implementation of AlphaFold, which utilizes MMseqs2 for the creation of multiple sequence alignments (MSAs). A higher number of recycles than the one used in the AlphaFold DB was selected, and no templates were used. In addition, prediction by RoseTTAFold was also applied to address how structures from the two deep learning frameworks match reality. The resulting conformations were compared with the corresponding experimental structures, providing potential insights into the predictive ability of this approach in this particular group of proteins. Furthermore, a comprehensive examination was performed on features such as predicted regions of disorder and the potential effect of mutations on PSN1. Our findings consist of highly accurate superpositions with little or no deviation from experimentally determined domain-level models.

The Dynamic Relationship between the Glymphatic System, Aging, Memory, and Sleep

The process of memory entails the activation of numerous neural networks and biochemical pathways throughout the brain. The phenomenon of memory decline in relation to aging has been the subject of extensive research for several decades. The correlation between the process of aging and memory is intricate and has various aspects to consider. Throughout the aging process, there are various alterations that take place within the brain and, as expected, affect other functions that have already been linked to memory and its function such as involving microcirculation and sleep. Recent studies provide an understanding of how these mechanisms may be interconnected through the relatively new concept of the glymphatic system. The glymphatic system is strongly correlated to sleep processes. Sleep helps the glymphatic system remove brain waste solutes. Astrocytes expand and contract to form channels for cerebrospinal fluid (CSF) to wash through the brain and eliminate waste. However, the details have not been totally elusive, but the discovery of what we call the glymphatic system enables us to connect many pieces of physiology to understand how such factors are interconnected and the interplay between them. Thus, the purpose of this review is to discuss how the glymphatic system, sleep, memory, and aging are interconnected through a network of complex mechanisms and dynamic interactions.

In vivo effects of the alpha-synuclein misfolding inhibitor minzasolmin supports clinical development in Parkinson's disease

Direct targeting of alpha-synuclein (ASYN) has emerged as a disease-modifying strategy for Parkinson's disease and other synucleinopathies which is being approached using both small molecule compounds and ASYN-targeted biologics. Minzasolmin (UCB0599) is an orally bioavailable and brain-penetrant small molecule ASYN misfolding inhibitor in clinical development as a disease-modifying therapeutic for Parkinson's disease. Herein the results of preclinical evaluations of minzasolmin that formed the basis for subsequent clinical development are described. Pharmacokinetic evaluations of intraperitoneal 1 and 5 mg/kg minzasolmin in wildtype mice revealed parallel and dose-proportional exposures in brain and plasma. Three-month administration studies in the Line 61 transgenic mouse model of PD were conducted to measure ASYN pathology and other PD-relevant endpoints including markers of CNS inflammation, striatal DAT labeling and gait. Reductions in ASYN pathology were correlated with improved aspects of gait and balance, reductions in CNS inflammation marker abundance, and normalized striatal DAT levels. These findings provide support for human dose determinations and have informed the translational strategy for clinical trial design and biomarker selection for the ongoing clinical studies of minzasolmin in patients living with early-stage Parkinson's disease (ClinicalTrials.gov ID: NCT04658186; EudraCT Number 2020-003265).

Molecular mechanisms of cellular senescence in neurodegenerative diseases

Neurodegenerative diseases, such as Alzheimer's and Parkinson's, are characterized by several pathological features, including selective neuronal loss, aggregation of specific proteins, and chronic inflammation. Aging is the most critical risk factor of these disorders. However, the mechanism by which aging contributes to the pathogenesis of neurodegenerative diseases is not clearly understood. Cellular senescence is a cell state or fate in response to stimuli. It is typically associated with a series of changes in cellular phenotypes such as abnormal cellular metabolism and proteostasis, reactive oxygen species (ROS) production, and increased secretion of certain molecules via senescence-associated secretory phenotype (SASP). In this review, we discuss how cellular senescence contributes to brain aging and neurodegenerative diseases, and the relationship between protein aggregation and cellular senescence. Finally, we discuss the potential of senescence modifiers and senolytics in the treatment of neurodegenerative diseases.

Neuronal growth on high-aspect-ratio diamond nanopillar arrays for biosensing applications

Monitoring neuronal activity with simultaneously high spatial and temporal resolution in living cell cultures is crucial to advance understanding of the development and functioning of our brain, and to gain further insights in the origin of brain disorders. While it has been demonstrated that the quantum sensing capabilities of nitrogen-vacancy (NV) centers in diamond allow real time detection of action potentials from large neurons in marine invertebrates, quantum monitoring of mammalian neurons (presenting much smaller dimensions and thus producing much lower signal and requiring higher spatial resolution) has hitherto remained elusive. In this context, diamond nanostructuring can offer the opportunity to boost the diamond platform sensitivity to the required level. However, a comprehensive analysis of the impact of a nanostructured diamond surface on the neuronal viability and growth was lacking. Here, we pattern a single crystal diamond surface with large-scale nanopillar arrays and we successfully demonstrate growth of a network of living and functional primary mouse hippocampal neurons on it. Our study on geometrical parameters reveals preferential growth along the nanopillar grid axes with excellent physical contact between cell membrane and nanopillar apex. Our results suggest that neuron growth can be tailored on diamond nanopillars to realize a nanophotonic quantum sensing platform for wide-field and label-free neuronal activity recording with sub-cellular resolution.

Current Treatments and New, Tentative Therapies for Parkinson’s Disease

Parkinson’s disease (PD) is a neurodegenerative pathology, the origin of which is associated with the death of neuronal cells involved in the production of dopamine. The prevalence of PD has increased exponentially. The aim of this review was to describe the novel treatments for PD that are currently under investigation and study and the possible therapeutic targets. The pathophysiology of this disease is based on the formation of alpha-synuclein folds that generate Lewy bodies, which are cytotoxic and reduce dopamine levels. Most pharmacological treatments for PD target alpha-synuclein to reduce the symptoms. These include treatments aimed at reducing the accumulation of alpha-synuclein (epigallocatechin), reducing its clearance via immunotherapy, inhibiting LRRK2, and upregulating cerebrosidase (ambroxol). Parkinson’s disease continues to be a pathology of unknown origin that generates a significant social cost for the patients who suffer from it. Although there is still no definitive cure for this disease at present, there are numerous treatments available aimed at reducing the symptomatology of PD in addition to other therapeutic alternatives that are still under investigation. However, the therapeutic approach to this pathology should include a combination of pharmacological and non-pharmacological strategies to maximise outcomes and improve symptomatological control in these patients. It is therefore necessary to delve deeper into the pathophysiology of the disease in order to improve these treatments and therefore the quality of life of the patients.

Tunneling Nanotubes Facilitate Intercellular Protein Transfer and Cell Networks Function

The past decade witnessed a huge interest in the communication machinery called tunneling nanotubes (TNTs) which is a novel, contact-dependent type of intercellular protein transfer (IPT). As the IPT phenomenon plays a particular role in the cross-talk between cells, including cancer cells as well as in the immune and nervous systems, it therefore participates in remodeling of the cellular networks. The following review focuses on the placing the role of tunneling nanotube-mediated protein transfer between distant cells. Firstly, we describe different screening methods used to study IPT including tunneling nanotubes. Further, we present various examples of TNT-mediated protein transfer in the immune system, cancer microenvironment and in the nervous system, with particular attention to the methods used to verify the transfer of individual proteins.

Proteomics for comprehensive characterization of extracellular vesicles in neurodegenerative disease

Extracellular vesicles (EVs) are small lipid bilayer particles ubiquitously released by almost every cell type. A specific and selective constituents of EVs loaded with variety of proteins, lipids, small noncoding RNAs, and long non-coding RNAs are reflective of cellular events, type, and physiologic/pathophysiologic status of the cell of origin. Moreover, these molecular contents carry information from the cell of origin to recipient cells, modulating intercellular communication. Recent studies demonstrated that EVs not only play a neuroprotective role by mediating the removal of toxic proteins, but also emerge as an important player in various neurodegenerative disease onset and progression through facilitating of misfolded proteins propagation. For this reason, neurodegenerative disease-associated differences in EV proteome relative to normal EVs can be used to fulfil diagnostic, prognostic, and therapeutic purposes. Nonetheless, characterizing EV proteome obtained from biological samples (brain tissue and body fluids, including urea, blood, saliva, and CSF) is a challenging task. Herein, we review the status of EV proteome profiling and the updated discovery of potential biomarkers for the diagnosis of neurodegenerative disease with an emphasis on the integration of high-throughput advanced mass spectrometry (MS) technologies for both qualitative and quantitative analysis of EVs in different clinical tissue/body fluid samples in past five years.

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.

The Role of Extracellular Matrix Components in the Spreading of Pathological Protein Aggregates

Several neurodegenerative diseases are characterized by the accumulation of aggregated misfolded proteins. These pathological agents have been suggested to propagate in the brain via mechanisms similar to that observed for the prion protein, where a misfolded variant is transferred from an affected brain region to a healthy one, thereby inducing the misfolding and/or aggregation of correctly folded copies. This process has been characterized for several proteins, such as α-synuclein, tau, amyloid beta (Aβ) and less extensively for huntingtin and TDP-43. α-synuclein, tau, TDP-43 and huntingtin are intracellular proteins, and their aggregates are located in the cytosol or nucleus of neurons. They have been shown to spread between cells and this event occurs, at least partially, via secretion of these protein aggregates in the extracellular space followed by re-uptake. Conversely, Aβ aggregates are found mainly extracellularly, and their spreading occurs in the extracellular space between brain regions. Due to the inherent nature of their spreading modalities, these proteins are exposed to components of the extracellular matrix (ECM), including glycans, proteases and core matrix proteins. These ECM components can interact with or process pathological misfolded proteins, potentially changing their properties and thus regulating their spreading capabilities. Here, we present an overview of the documented roles of ECM components in the spreading of pathological protein aggregates in neurodegenerative diseases with the objective of identifying the current gaps in knowledge and stimulating further research in the field. This could potentially lead to the identification of druggable targets to slow down the spreading and/or progression of these pathologies.

Unveiling the effect of Withania somnifera on neuronal cytoarchitecture and synaptogenesis: A combined in vitro and network pharmacology approach

Withania somnifera (WS), is known for its remarkable contribution in herbal medicine and Ayurveda, which is therapeutically applied to improve memory and anxiety in patients. However, the pharmacological details of this plant on memory boosting yet remained undefined. This study provides mechanistic insights on the effect of ethanol solution extract of the whole plant of WS (WSEE) on neuritogenesis by combining in vitro and in silico network pharmacology approaches. WSEE promoted significant neuronal growth through early differentiation, axodendritic arborization, and synaptogenesis on primary hippocampal neurons. The network pharmacological study confirmed that the neuritogenic activity is potentially mediated by modulating the neurotrophin signaling pathway, where NRTK1 (TrkA) was revealed as the primary target of WS secondary metabolites. This neurotrophic activity of WSEE was significantly stifled by the presence of TrkA inhibitor, which further confirms the TrkA-dependent activity of WSEE. In addition, a molecular docking study suggested steroidal lactones present in the WS might act as nerve growth factor (NGF)-mimetics, activating TrkA by binding to the NGF-binding domain. As a whole, the findings of the study suggest a significant role of WSEE on neuritogenesis and its potential to function as a therapeutic agent and in drug designing for the prevention and treatment of memory-related neurological disorders.

Syndecan-3 as a Novel Biomarker in Alzheimer's Disease

Early diagnosis of Alzheimer’s disease (AD) is of paramount importance in preserving the patient’s mental and physical health in a fairly manageable condition for a longer period. Reliable AD detection requires novel biomarkers indicating central nervous system (CNS) degeneration in the periphery. Members of the syndecan family of transmembrane proteoglycans are emerging new targets in inflammatory and neurodegenerative disorders. Reviewing the growing scientific evidence on the involvement of syndecans in the pathomechanism of AD, we analyzed the expression of the neuronal syndecan, syndecan-3 (SDC3), in experimental models of neurodegeneration. Initial in vitro studies showed that prolonged treatment of tumor necrosis factor-alpha (TNF-α) increases SDC3 expression in model neuronal and brain microvascular endothelial cell lines. In vivo studies revealed elevated concentrations of TNF-α in the blood and brain of APPSWE-Tau transgenic mice, along with increased SDC3 concentration in the brain and the liver. Primary brain endothelial cells and peripheral blood monocytes isolated from APPSWE-Tau mice exhibited increased SDC3 expression than wild-type controls. SDC3 expression of blood-derived monocytes showed a positive correlation with amyloid plaque load in the brain, demonstrating that SDC3 on monocytes is a good indicator of amyloid pathology in the brain. Given the well-established role of blood tests, the SDC3 expression of monocytes could serve as a novel biomarker for early AD detection.

Cell Death Related Proteins Beyond Apoptosis in the CNS

Cell death related (CDR) proteins are a diverse group of proteins whose original function was ascribed to apoptotic cell death signaling. Recently, descriptions of non-apoptotic functions for CDR proteins have increased. In this minireview, we comment on recent studies of CDR proteins outside the field of apoptosis in the CNS, encompassing areas such as the inflammasome and non-apoptotic cell death, cytoskeleton reorganization, synaptic plasticity, mitophagy, neurodegeneration and calcium signaling among others. Furthermore, we discuss the evolution of proteomic techniques used to predict caspase substrates that could potentially explain their non-apoptotic roles. Finally, we address new concepts in the field of non-apoptotic functions of CDR proteins that require further research such the effect of sexual dimorphism on non-apoptotic CDR protein function and the emergence of zymogen-specific caspase functions.

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.

Endosomal sorting drives the formation of axonal prion protein endoggresomes

The pathogenic aggregation of misfolded prion protein (PrP) in axons underlies prion disease pathologies. The molecular mechanisms driving axonal misfolded PrP aggregate formation leading to neurotoxicity are unknown. We found that the small endolysosomal guanosine triphosphatase (GTPase) Arl8b recruits kinesin-1 and Vps41 (HOPS) onto endosomes carrying misfolded mutant PrP to promote their axonal entry and homotypic fusion toward aggregation inside enlarged endomembranes that we call endoggresomes. This axonal rapid endosomal sorting and transport-dependent aggregation (ARESTA) mechanism forms pathologic PrP endoggresomes that impair calcium dynamics and reduce neuronal viability. Inhibiting ARESTA diminishes endoggresome formation, rescues calcium influx, and prevents neuronal death. Our results identify ARESTA as a key pathway for the regulation of endoggresome formation and a new actionable antiaggregation target to ameliorate neuronal dysfunction in the prionopathies.

The Interplay of the Unfolded Protein Response in Neurodegenerative Diseases: A Therapeutic Role of Curcumin

Abnormal accumulation of misfolded proteins in the endoplasmic reticulum and their aggregation causes inflammation and endoplasmic reticulum stress. This promotes accumulation of toxic proteins in the body tissues especially brain leading to manifestation of neurodegenerative diseases. The studies suggest that deregulation of proteostasis, particularly aberrant unfolded protein response (UPR) signaling, may be a common morbific process in the development of neurodegeneration. Curcumin, the mixture of low molecular weight polyphenolic compounds from turmeric, Curcuma longa has shown promising response to prevents many diseases including current global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and neurodegenerative disorders. The UPR which correlates positively with neurodegenerative disorders were found affected by curcumin. In this review, we examine the evidence from many model systems illustrating how curcumin interacts with UPR and slows down the development of various neurodegenerative disorders (ND), e.g., Alzheimer's and Parkinson's diseases. The recent global increase in ND patients indicates that researchers and practitioners will need to develop a new pharmacological drug or treatment to manage and cure these neurodegenerative diseases.

Abnormal Enhancement of Protein Disulfide Isomerase-like Activity of a Cyclic Diselenide Conjugated with a Basic Amino Acid by Inserting a Glycine Spacer

In a previous study, we reported that (S)-1,2-diselenane-4-amine (1) catalyzes oxidative protein folding through protein disulfide isomerase (PDI)-like catalytic mechanisms and that the direct conjugation of a basic amino acid (Xaa: His, Lys, or Arg) via an amide bond improves the catalytic activity of 1 by increasing its diselenide (Se–Se) reduction potential (E′°). In this study, to modulate the Se–Se redox properties and the association of the compounds with a protein substrate, new catalysts, in which a Gly spacer was inserted between 1 and Xaa, were synthesized. Exhaustive comparison of the PDI-like catalytic activities and E′° values among 1, 1-Xaa, and 1-Gly-Xaa showed that the insertion of a Gly spacer into 1-Xaa either did not change or slightly reduced the PDI-like activity and the E′° values. Importantly, however, only 1-Gly-Arg deviated from this generality and showed obviously increased E°′ value and PDI-like activity compared to the corresponding compound with no Gly spacer (1-Arg); on the contrary, its catalytic activity was the highest among the diselenide compounds employed in this study, while this abnormal enhancement of the catalytic activity of 1-Gly-Arg could not be fully explained by the thermodynamics of the Se–Se bond and its association ability with protein substrates.

Sodium fusidate prevents protein aggregation of silk fibroin and offers new perspectives for human lens material disaggregation

Silk fibroin (SF) is a non-pathological amyloidogenic protein prone, in solution, to the formation of amyloid-like aggregated species, displaying similarities in fibrillation kinetics with pathological amyloids, as widely reported in the literature. We show here, on the basis of different biophysical approaches (turbidity, Congo Red assays, CD, DLS and fluorescence), that fusidic acid (FA), a well-known antibiotic, acts on SF as an anti-aggregating agent in a dose-dependent manner, being also able to revert SF aggregation. FA binds to SF inducing changes in the environment of SF aromatic residues. We further provide the proof of principle that FA, already approved as drug on humans and used in ophthalmic preparations, displays its anti-aggregation properties also on lens material derived from cataract surgery and is capable of reducing aggregation. Thus it is suggested that FA can be foreseen as a therapeutic treatment for cataract and other protein aggregation disorders.

Viral Induced Protein Aggregation: A Mechanism of Immune Evasion

Various intrinsic and extrinsic factors can interfere with the process of protein folding, resulting in protein aggregates. Usually, cells prevent the formation of aggregates or degrade them to prevent the cytotoxic effects they may cause. However, during viral infection, the formation of aggregates may serve as a cellular defense mechanism. On the other hand, some viruses are able to exploit the process of aggregate formation and removal to promote their replication or evade the immune response. This review article summarizes the process of cellular protein aggregation and gives examples of how different viruses exploit it. Particular emphasis is placed on the ribonucleotide reductases of herpesviruses and how their additional non-canonical functions in viral immune evasion are closely linked to protein aggregation.

Direct visualization and profiling of protein misfolding and aggregation in live cells

Over the past few years, research tools have been developed to monitor the multistep protein aggregation process in live cells, a process that has been associated with a growing number of human diseases. Herein, we describe recent advances in methods that can either survey the distribution of aggregation at the level of the cellular proteome using mass spectroscopy or discern the multistep aggregation process of specific proteins of interest via fluorescence signals. Future development and application of such technologies are expected to provide insights on mechanisms, diagnosis, and treatment of diseases rooted in protein aggregation.

Curcumin: A small molecule with big functionality against amyloid aggregation in neurodegenerative diseases and type 2 diabetes

Amyloidosis is a concept that implicates disorders and complications that are due to abnormal protein accumulation in different cells and tissues. Protein aggregation-associated diseases are classified according to the type of aggregates and deposition sites, such as neurodegenerative disorders and type 2 diabetes mellitus. Polyphenolic phytochemicals such as curcumin and its derivatives have anti-amyloid effects both in vitro and in animal models; however, the underlying mechanisms are not understood. In this review, we summarized possible mechanisms by which curcumin could interfere with self-assembly processes and reduce amyloid aggregation in amyloidosis. Furthermore, we discuss clinical trials in which curcumin is used as a therapeutic agent for the treatment of diseases linking to protein aggregates.

Alpha-Synuclein as a Prominent Actor in the Inflammatory Synaptopathy of Parkinson's Disease

Parkinson’s disease (PD) is considered the most common disorder of synucleinopathy, which is characterised by intracellular inclusions of aggregated and misfolded α-synuclein (α-syn) protein in various brain regions, and the loss of dopaminergic neurons. During the early prodromal phase of PD, synaptic alterations happen before cell death, which is linked to the synaptic accumulation of toxic α-syn specifically in the presynaptic terminals, affecting neurotransmitter release. The oligomers and protofibrils of α-syn are the most toxic species, and their overexpression impairs the distribution and activation of synaptic proteins, such as the SNARE complex, preventing neurotransmitter exocytosis and neuronal synaptic communication. In the last few years, the role of the immune system in PD has been increasingly considered. Microglial and astrocyte activation, the gene expression of proinflammatory factors, and the infiltration of immune cells from the periphery to the central nervous system (CNS) represent the main features of the inflammatory response. One of the actors of these processes is α-syn accumulation. In light of this, here, we provide a systematic review of PD-related α-syn and inflammation inter-players.

Phosphorylated tau targeted small-molecule PROTACs for the treatment of Alzheimer's disease and tauopathies

Tau is a microtubule-stabilizing protein that plays an important role in the formation of axonal microtubules in neurons. Phosphorylated tau (p-Tau) has received great attention in the field of Alzheimer's disease (AD) as a potential therapeutic target due to its involvement with synaptic damage and neuronal dysfunction. Mounting evidence suggests that amyloid beta (Aβ)-targeted clinical trials continuously failed; therefore, it is important to consider alternative therapeutic strategies such as p-tau-PROTACs targeted small molecules for AD and other tauopathies. The present article describes the characteristics of tau biology, structure, and function in both healthy and pathological states in AD. It also explains data from studies that have identified the involvement of p-tau in neuronal damage and synaptic and cognitive functions in AD. Current article also covers several aspects, including small molecule inhibitors, and the development of p-tau-PROTACs targeted drug molecules to treat patients with AD and other tauopathies.

Role of triggering receptor expressed on myeloid cells 2 (TREM2) in neurodegenerative dementias

Neurodegeneration is a debilitating condition that causes nerve cell degeneration or death. Neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), frontotemporal dementia (FTD), and Lewy body dementia (LBD) are posing a larger population burden of dementia worldwide. Neurodegenerative dementia is one of the main challenges in public health with its main characteristics being permanent loss of memory, impairment in cognition, and impaired daily functions. The published literature about genetic studies of these disorders suggests genetic underpinning in the pathogenesis of neurodegenerative dementia. In the process of underlining the pathogenesis of NDD, growing evidence has related genetic variations in the triggering receptor expressed on myeloid cells 2 (TREM2). This review paper aims to provide a detailed information regarding the association of TREM2 and NDDs leading to dementia. A central consideration is AD that accounts for almost 50%-70% of all late-life dementias alone or in combination with other neurological disorders. Other prevalent neurodegenerative conditions that lead to dementia are also discussed. Such studies are important as they can give a comprehensive knowledge of TREM2's role in various NDDs, in order to maximize the potential for developing new therapeutic approaches.

Dendrimer Architectonics to Treat Cancer and Neurodegenerative Diseases with Implications in Theranostics and Personalized Medicine

Integration of diagnostic and therapeutic functions in a single platform namely theranostics has become a cornerstone for personalized medicine. Theranostics platform facilitates noninvasive detection and treatment while allowing the monitoring of disease progression and therapeutic efficacy in case of chronic conditions of cancer and Alzheimer's disease (AD). Theranostic tools function by themselves or with the aid of carrier, viz. liposomes, micelles, polymers, or dendrimers. The dendrimer architectures (DA) are well-characterized molecular nanoobjects with a large number of terminal functional groups to enhance solubility and offer multivalency and multifunctional properties. Various noninvasive diagnostic tools like magnetic resonance imaging (MRI), computed tomography (CT), gamma scintigraphy, and optical techniques have been accomplished utilizing DAs for simultaneous imaging and drug delivery. Obstacles in the formulation design, drug loading, payload delivery, biocompatibility, overcoming cellular membrane and blood-brain barrier (BBB), and systemic circulation remain a bottleneck in translational efforts. This review focuses on the diagnostic, therapeutic and theranostic potential of DA-based nanocarriers in treating cancer and neurodegenerative disorders like AD and Parkinson's disease (PD), among others. In view of the inverse relationship between cancer and AD, designing suitable DA-based theranostic nanodrug with high selectivity has tremendous implications in personalized medicine to treat cancer and neurodegenerative disorders.

ROS networks: designs, aging, Parkinson's disease and precision therapies

How the network around ROS protects against oxidative stress and Parkinson's disease (PD), and how processes at the minutes timescale cause disease and aging after decades, remains enigmatic. Challenging whether the ROS network is as complex as it seems, we built a fairly comprehensive version thereof which we disentangled into a hierarchy of only five simpler subnetworks each delivering one type of robustness. The comprehensive dynamic model described in vitro data sets from two independent laboratories. Notwithstanding its five-fold robustness, it exhibited a relatively sudden breakdown, after some 80 years of virtually steady performance: it predicted aging. PD-related conditions such as lack of DJ-1 protein or increased α-synuclein accelerated the collapse, while antioxidants or caffeine retarded it. Introducing a new concept (aging-time-control coefficient), we found that as many as 25 out of 57 molecular processes controlled aging. We identified new targets for "life-extending interventions": mitochondrial synthesis, KEAP1 degradation, and p62 metabolism.

Amelioration of Tau pathology and memory deficits by targeting 5-HT7 receptor

Tauopathies comprise a heterogeneous family of neurodegenerative diseases characterized by pathological accumulation of hyperphosphorylated Tau protein. Pathological changes in serotonergic signaling have been associated with tauopathy etiology, but the underlying mechanisms remain poorly understood. Here, we studied the role of the serotonin receptor 7 (5-HT7R), in a mouse model of tauopathy induced by overexpressing the human Tau[R406W] mutant associated with inherited forms of frontotemporal dementia. We showed that the constitutive 5-HT7R activity is required for Tau hyperphosphorylation and formation of highly bundled Tau structures (HBTS) through G-protein-independent, CDK5-dependent mechanism. We also showed that 5-HT7R physically interacts with CDK5. At the systemic level, 5-HT7R-mediated CDK5 activation induces HBTS leading to neuronal death, reduced long-term potentiation (LTP), and impaired memory in mice. Specific blockade of constitutive 5-HT7R activity in neurons that overexpressed Tau[R406W] prevents Tau hyperphosphorylation, aggregation, and neurotoxicity. Moreover, 5-HT7R knockdown in the prefrontal cortex fully abrogates Tau[R406W]-induced LTP deficits and memory impairments. Thus, 5-HT7R/CDK5 signaling emerged as a new, promising target for tauopathy treatments.

Basic Amino Acid Conjugates of 1,2-Diselenan-4-amine with Protein Disulfide Isomerase-like Functions as a Manipulator of Protein Quality Control

Protein disulfide isomerase (PDI) can assist immature proteins to correctly fold by controlling cysteinyl disulfide (SS)-relating reactions (i. e., SS-formation, SS-cleavage, and SS-isomerization). PDI controls protein quality by suppressing protein aggregation, as well as functions as an oxidative folding catalyst. Following the amino acid sequence of the active center in PDI, basic amino acid conjugates of 1,2-diselenan-4-amine (1), which show oxidoreductase- and isomerase-like activities for SS-relating reactions, were designed as a novel PDI model compound. By conjugating the amino acids, the diselenide reduction potential of compound 1 was significantly increased, causing improvement of the catalytic activities for all SS-relating reactions. Furthermore, these compounds, especially histidine-conjugated one, remarkably suppressed protein aggregation even at low concertation (0.3 mM∼). Thus, it was demonstrated that the conjugation of basic amino acids into 1 simultaneously achieves the enhancement of the redox reactivity and the capability to suppress protein aggregation.

Clinical implications of extracellular vesicles in neurodegenerative diseases

Introduction: Extracellular vesicles (EVs) released by neural cells play a crucial role in intracellular communication in both physiological and pathological states. Recent studies have shown that the neuropathogenic manifestation of many progressive nervous system diseases including Parkinson's disease (PD), Alzheimer's diseases (AD), and amyotrophic lateral sclerosis (ALS). These diseases are frequently found to be associated with the accumulation of misfolded proteins, exploit EVs for the spread of aggregates to naive cells in a prion-like mechanism. Therefore, characterization of EVs and understanding their mechanism of action could open a window of opportunity to discover biomarkers and therapeutic targets in a disease-specific manner. Areas covered: In this review, we discuss the role of neural cells-derived EVs in normal and disease states. We also highlight their biomedical potential in modern medicine, including the use of circulating EVs as biomarkers for diagnosis with a special focus on newly-identified potential biomarkers in neurodegenerative disease, and novel methodologies in EVs isolation. Expert opinion: Systematic and comprehensive analysis of EVs in different biofluid sources is needed. Considering the potential for tremendous clinical benefits of EVs research in neurodegenerative disease, there is also an urgent need to standardize neural cells-derived EV enrichment protocols for consensus results.

Proteasome Activation to Combat Proteotoxicity

Loss of proteome fidelity leads to the accumulation of non-native protein aggregates and oxidatively damaged species: hallmarks of an aged cell. These misfolded and aggregated species are often found, and suggested to be the culpable party, in numerous neurodegenerative diseases including Huntington's, Parkinson's, Amyotrophic Lateral Sclerosis (ALS), and Alzheimer's Diseases (AD). Many strategies for therapeutic intervention in proteotoxic pathologies have been put forth; one of the most promising is bolstering the efficacy of the proteasome to restore normal proteostasis. This strategy is ideal as monomeric precursors and oxidatively damaged proteins, so called "intrinsically disordered proteins" (IDPs), are targeted by the proteasome. This review will provide an overview of disorders in proteins, both intrinsic and acquired, with a focus on susceptibility to proteasomal degradation. We will then examine the proteasome with emphasis on newly published structural data and summarize current known small molecule proteasome activators.

Neurotheranostics as personalized medicines

The discipline of neurotheranostics was forged to improve diagnostic and therapeutic clinical outcomes for neurological disorders. Research was facilitated, in largest measure, by the creation of pharmacologically effective multimodal pharmaceutical formulations. Deployment of neurotheranostic agents could revolutionize staging and improve nervous system disease therapeutic outcomes. However, obstacles in formulation design, drug loading and payload delivery still remain. These will certainly be aided by multidisciplinary basic research and clinical teams with pharmacology, nanotechnology, neuroscience and pharmaceutic expertise. When successful the end results will provide "optimal" therapeutic delivery platforms. The current report reviews an extensive body of knowledge of the natural history, epidemiology, pathogenesis and therapeutics of neurologic disease with an eye on how, when and under what circumstances neurotheranostics will soon be used as personalized medicines for a broad range of neurodegenerative, neuroinflammatory and neuroinfectious diseases.

Biocompatible Inhibitor Based on Chitosan and Amphiphilic Peptide against Mutant Huntingtin Toxicity

Huntington's disease (HD) is classified as a protein-misfolding disease correlated with the mutant Huntingtin (mHtt) protein with abnormally expanded polyglutamine (polyQ) domains. Because no effective drugs have yet been reported, attempts to develop better therapy to delay the age of onset are in urgent demand. In this study, an amphiphilic peptide consisting of negatively charged hexaglutamic acid and a stretch of decaglutamine (E₆ Q₁₀ ) was chemically synthesized as an inhibitor against polyQ and mHtt toxicity. It is found that E₆ Q₁₀ selfassembles into spherical vesicles, as shown by means of TEM, cryoelectron microscopy, and dynamic light scattering. Assembled E₆ Q₁₀ prevented the polyQ-rich peptide (KKWQ₂₀ AKK) from forming amyloid fibrils. To enable the cell-penetration ability of E₆ Q₁₀ , the E₆ Q₁₀ ⋅chitosan complex was generated. It is demonstrated that the complex penetrates cells, interferes with the mHtt oligomerization and aggregation process, and prevents mHtt cytotoxicity. By combining positively charged chitosan and amphiphilic peptides with a negatively charge moiety, a new strategy is provided to develop biocompatible and biodegradable inhibitors against mHtt toxicity.

Systemic peptide mediated delivery of an siRNA targeting α-syn in the CNS ameliorates the neurodegenerative process in a transgenic model of Lewy body disease

Neurodegenerative disorders of the aging population are characterized by progressive accumulation of neuronal proteins such as α-synuclein (α-syn) in Parkinson's Disease (PD) and Amyloid ß (Aß) and Tau in Alzheimer's disease (AD) for which no treatments are currently available. The ability to regulate the expression at the gene transcription level would be beneficial for reducing the accumulation of these proteins or regulating expression levels of other genes in the CNS. Short interfering RNA molecules can bind specifically to target RNAs and deliver them for degradation. This approach has shown promise therapeutically in vitro and in vivo in mouse models of PD and AD and other neurological disorders; however, delivery of the siRNA to the CNS in vivo has been achieved primarily through intra-cerebral or intra-thecal injections that may be less amenable for clinical translation; therefore, alternative approaches for delivery of siRNAs to the brain is needed. Recently, we described a small peptide from the envelope protein of the rabies virus (C2-9r) that was utilized to deliver an siRNA targeting α-syn across the blood brain barrier (BBB) following intravenous injection. This approach showed reduced expression of α-syn and neuroprotection in a toxic mouse model of PD. However, since receptor-mediated delivery is potentially saturable, each allowing the delivery of a limited number of molecules, we identified an alternative peptide for the transport of nucleotides across the BBB based on the apolipoprotein B (apoB) protein targeted to the family of low-density lipoprotein receptors (LDL-R). We used an 11-amino acid sequence from the apoB protein (ApoB11) that, when coupled with a 9-amino acid arginine linker, can transport siRNAs across the BBB to neuronal and glial cells. To examine the value of this peptide mediated oligonucleotide delivery system for PD, we delivered an siRNA targeting the α-syn (siα-syn) in a transgenic mouse model of PD. We found that ApoB11 was effective (comparable to C2-9r) at mediating the delivery of siα-syn into the CNS, co-localized to neurons and glial cells and reduced levels of α-syn protein translation and accumulation. Delivery of ApoB11/siα-syn was accompanied by protection from degeneration of selected neuronal populations in the neocortex, limbic system and striato-nigral system and reduced neuro-inflammation. Taken together, these results suggest that systemic delivery of oligonucleotides targeting α-syn using ApoB11 might be an interesting alternative strategy worth considering for the experimental treatment of synucleinopathies.

Protein Misfolding and ER Stress in Huntington's Disease

Increasing evidence in recent years indicates that protein misfolding and aggregation, leading to ER stress, are central factors of pathogenicity in neurodegenerative diseases. This is particularly true in Huntington's disease (HD), where in contrast with other disorders, the cause is monogenic. Mutant huntingtin interferes with many cellular processes, but the fact that modulation of ER stress and of the unfolded response pathways reduces the toxicity, places these mechanisms at the core and gives hope for potential therapeutic approaches. There is currently no effective treatment for HD and it has a fatal outcome a few years after the start of symptoms of cognitive and motor impairment. Here we will discuss recent findings that shed light on the mechanisms of protein misfolding and aggregation that give origin to ER stress in neurodegenerative diseases, focusing on Huntington's disease, on the cellular response and on how to use this knowledge for possible therapeutic strategies.

RNA as a key factor in driving or preventing self-assembly of the TAR DNA-binding protein 43

Amyotrophic lateral sclerosis and frontotemporal lobar degeneration are incurable motor neuron diseases associated with muscle weakness, paralysis and respiratory failure. Accumulation of TAR DNA-binding protein 43 (TDP-43) as toxic cytoplasmic inclusions is one of the hallmarks of these pathologies. TDP-43 is an RNA-binding protein responsible for regulating RNA transcription, splicing, transport and translation. Aggregated TDP-43 does not retain its physiological function.

Here, we exploit the ability of TDP-43 to bind specific RNA sequences to validate our hypothesis that the native partners of a protein can be used to interfere with its ability to self-assemble into aggregates. We propose that binding of TDP-43 to specific RNA can compete with protein aggregation. This study provides a solid proof of concept to the hypothesis that natural interactions can be exploited to increase protein solubility and could be adopted as a more general rational therapeutic strategy.

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We found that binding of the RRM domains of TDP-43 to specific RNA competes with protein aggregation.

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This study provides a solid proof of concept to the hypothesis that natural interactions can be exploited to increase protein solubility.

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The concept could be adopted as a more general rationale for protein-specific drug design.

AQAMAN, a bisamidine-based inhibitor of toxic protein inclusions in neurons, ameliorates cytotoxicity in polyglutamine disease models

Polyglutamine (polyQ) diseases are a group of dominantly inherited neurodegenerative disorders caused by the expansion of an unstable CAG repeat in the coding region of the affected genes. Hallmarks of polyQ diseases include the accumulation of misfolded protein aggregates, leading to neuronal degeneration and cell death. PolyQ diseases are currently incurable, highlighting the urgent need for approaches that inhibit the formation of disaggregate cytotoxic polyQ protein inclusions. Here, we screened for bisamidine-based inhibitors that can inhibit neuronal polyQ protein inclusions. We demonstrated that one inhibitor, AQAMAN, prevents polyQ protein aggregation and promotes de-aggregation of self-assembled polyQ proteins in several models of polyQ diseases. Using immunocytochemistry, we found that AQAMAN significantly reduces polyQ protein aggregation and specifically suppresses polyQ protein-induced cell death. Using a recombinant and purified polyQ protein (thioredoxin-Huntingtin-Q46), we further demonstrated that AQAMAN interferes with polyQ self-assembly, preventing polyQ aggregation, and dissociates preformed polyQ aggregates in a cell-free system. Remarkably, AQAMAN feeding of Drosophila expressing expanded polyQ disease protein suppresses polyQ-induced neurodegeneration in vivo In addition, using inhibitors and activators of the autophagy pathway, we demonstrated that AQAMAN's cytoprotective effect against polyQ toxicity is autophagy-dependent. In summary, we have identified AQAMAN as a potential therapeutic for combating polyQ protein toxicity in polyQ diseases. Our findings further highlight the importance of the autophagy pathway in clearing harmful polyQ proteins.

Pharmacophore-based models for therapeutic drugs against phosphorylated tau in Alzheimer's disease

Phosphorylated tau (P-tau) has received much attention in the field of Alzheimer's disease (AD), as a potential therapeutic target owing to its involvement with synaptic damage and neuronal dysfunction. The continuous failure of amyloid β (Aβ)-targeted therapeutics highlights the urgency to consider alternative therapeutic strategies for AD. The present review describes the latest developments in tau biology and function. It also explains abnormal interactions between P-tau with Aβ and the mitochondrial fission protein Drp1, leading to excessive mitochondrial fragmentation and synaptic damage in AD neurons. This article also addresses 3D pharmacophore-based drug models designed to treat patients with AD and other tauopathies.

Neurodegenerative Diseases: Regenerative Mechanisms and Novel Therapeutic Approaches

Regeneration refers to regrowth of tissue in the central nervous system. It includes generation of new neurons, glia, myelin, and synapses, as well as the regaining of essential functions: sensory, motor, emotional and cognitive abilities. Unfortunately, regeneration within the nervous system is very slow compared to other body systems. This relative slowness is attributed to increased vulnerability to irreversible cellular insults and the loss of function due to the very long lifespan of neurons, the stretch of cells and cytoplasm over several dozens of inches throughout the body, insufficiency of the tissue-level waste removal system, and minimal neural cell proliferation/self-renewal capacity. In this context, the current review summarized the most common features of major neurodegenerative disorders; their causes and consequences and proposed novel therapeutic approaches.

Exogenous α-synuclein hinders synaptic communication in cultured cortical primary rat neurons

Amyloid aggregates of the protein α-synuclein (αS) called Lewy Bodies (LB) and Lewy Neurites (LN) are the pathological hallmark of Parkinson's disease (PD) and other synucleinopathies. We have previously shown that high extracellular αS concentrations can be toxic to cells and that neurons take up αS. Here we aimed to get more insight into the toxicity mechanism associated with high extracellular αS concentrations (50-100 μM). High extracellular αS concentrations resulted in a reduction of the firing rate of the neuronal network by disrupting synaptic transmission, while the neuronal ability to fire action potentials was still intact. Furthermore, many cells developed αS deposits larger than 500 nm within five days, but otherwise appeared healthy. Synaptic dysfunction clearly occurred before the establishment of large intracellular deposits and neuronal death, suggesting that an excessive extracellular αS concentration caused synaptic failure and which later possibly contributed to neuronal death.

Overexpression of a conserved HSP40 chaperone reduces toxicity of several neurodegenerative disease proteins

TDP-43 and FUS are DNA/RNA binding proteins associated with neuronal inclusions in amyotrophic lateral sclerosis (ALS) patients. Other neurodegenerative diseases are also characterized by neuronal protein aggregates, e.g. Huntington's disease, associated with polyglutamine (polyQ) expansions in the protein huntingtin. Here we discuss our recent paper establishing similarities between aggregates of TDP-43 that have short glutamine and asparagine (Q/N)-rich modules and are soluble in detergents, with those of polyQ and PIN4C that have large Q/N-rich domains and are detergent-insoluble. We also present new, similar data for FUS. Together, we show that like overexpression of polyQ or PIN4C, overexpression of FUS or TDP-43 causes inhibition of the ubiquitin proteasome system (UPS) and toxicity, both of which are mitigated by overexpression of the Hsp40 chaperone Sis1. Also, in all cases toxicity is enhanced by the [PIN⁺] prion. In addition, we show that the Sis1 mammalian homolog DNAJBI reduces toxicity arising from overexpressed FUS and TDP-43 respectively in human embryonic kidney cells and primary rodent neurons. The common properties of these proteins suggest that heterologous aggregates may enhance the toxicity of a variety of disease-related aggregating proteins, and further that chaperones and the UPS may be key therapeutic targets for diseases characterized by protein inclusions.

Critical appraisal of pathology transmission in the α-synuclein fibril model of Lewy body disorders

Lewy body disorders are characterized by the emergence of α-synucleinopathy in many parts of the central and peripheral nervous systems, including in the telencephalon. Dense α-synuclein+ pathology appears in regio inferior of the hippocampus in both Parkinson's disease and dementia with Lewy bodies and may disturb cognitive function. The preformed α-synuclein fibril model of Parkinson's disease is growing in use, given its potential for seeding the self-propagating spread of α-synucleinopathy throughout the mammalian brain. Although it is often assumed that the spread occurs through neuroanatomical connections, this is generally not examined vis-à-vis the uptake and transport of tract-tracers infused at precisely the same stereotaxic coordinates. As the neuronal connections of the hippocampus are historically well defined, we examined the first-order spread of α-synucleinopathy three months following fibril infusions centered in the mouse regio inferior (CA2+CA3), and contrasted this to retrograde and anterograde transport of the established tract-tracers FluoroGold and biotinylated dextran amines (BDA). Massive hippocampal α-synucleinopathy was insufficient to elicit memory deficits or loss of cells and synaptic markers in this model of early disease processes. However, dense α-synuclein+ inclusions in the fascia dentata were negatively correlated with memory capacity. A modest compensatory increase in synaptophysin was evident in the stratum radiatum of cornu Ammonis in fibril-infused animals, and synaptophysin expression correlated inversely with memory function in fibril but not PBS-infused mice. No changes in synapsin I/II expression were observed. The spread of α-synucleinopathy was somewhat, but not entirely consistent with FluoroGold and BDA axonal transport, suggesting that variables other than innervation density also contribute to the materialization of α-synucleinopathy. For example, layer II entorhinal neurons of the perforant pathway exhibited somal α-synuclein+ inclusions as well as retrogradely labeled FluoroGold+ somata. However, some afferent brain regions displayed dense retrograde FluoroGold label and no α-synuclein+ inclusions (e.g. medial septum/diagonal band), supporting the selective vulnerability hypothesis. The pattern of inclusions on the contralateral side was consistent with specific spread through commissural connections (e.g. stratum pyramidale of CA3), but again, not all commissural projections exhibited α-synucleinopathy (e.g. hilar mossy cells). The topographical extent of inclusions is displayed here in high-resolution images that afford viewers a rich opportunity to dissect the potential spread of pathology through neural circuitry. Finally, the results of this expository study were leveraged to highlight the challenges and limitations of working with preformed α-synuclein fibrils.

Brains with sporadic Creutzfeldt-Jakob disease and copathology showed a prolonged end-stage of disease

AIMS

To investigate the expression of major proteins related to primary neurodegenerative diseases and their prognostic significance in brains with Creutzfeldt-Jakob disease (CJD).

MATERIALS AND METHODS

Thirty consecutive cases of confirmed CJD during the period 2010-2015 at Basque Brain bank were retrospectively reviewed. Moreover, major neurodegenerative-associated proteins (phosphorylated Tau, 4R tau, 3R tau, alpha-synuclein, TDP43, amyloid beta) were tested. Clinical data were reviewed. Cases were divided according to the presence or absence of copathology. Survival curves were also determined.

RESULTS

Copathology was significantly associated with survival in brains with CJD (4.2±1.2 vs 9.2±1.9; P=0.019) and in brains with MM1/MV1 CJD (2.1±1.0 vs 6.7±2.8; P=0.012). Besides, the presence of more than one major neurodegenerative-associated protein was significantly associated with survival (4.2±1.2 vs 10.7±2.6; P=0.017). Thus, univariate analyses further pointed out variables significantly associated with better survival: copathology in CJD (HR=0.430; P=0.033); more than one neurodegenerative-associated protein in CJD (HR=0.369; P=0.036) and copathology in MM1/MV1 CJD (HR=0.525; P=0.032).

CONCLUSION

The existence of copathology significantly prolongs survival in patients with rapidly progressive dementia due to CJD. The study of major neurodegenerative-associated proteins in brains with CJD could allow us to further understand the molecular mechanisms behind prion diseases.

Oxidative Stress Modifies the Levels and Phosphorylation State of Tau Protein in Human Fibroblasts

Since the tau protein is closely involved in the physiopathology of Alzheimer's disease (AD), studying its behavior in cellular models might lead to new insights on understanding this devastating disease at molecular levels. In the present study, primary cultures of human fibroblasts were established and used to determine the expression and localization of the tau protein in distinct phosphorylation states in both untransfected and tau gene-transfected cells subjected to oxidative stress. Higher immunopositivity to phospho-tau was observed in cell nuclei in response to oxidative stress, while the levels of total tau in the cytosol remained unchanged. These findings were observed in both untransfected cells and those transfected with the tau gene. The present work represents a useful model for studying the physiopathology of AD at the cellular level in terms of tau protein implications.