Amyloid Protein Aggregates Research Articles

Biomarker Detection and Therapy of Parkinson's and Alzheimer's disease using upconversion based approach: A Comprehensive Review.

Neurodegenerative diseases (NDs) are debilitating disorders characterized by the progressive and selective loss of function or structure in the brain and spinal cord. Both chronic and acute forms of these diseases are associated with significant morbidity and mortality, as they involve the degeneration of neurons in various brain regions. Misfolding and aggregation of amyloid proteins into oligomer and β-sheet rich fibrils share as common hallmark and lead to neurotoxicity. Unfortunately, effective curative therapies remain limited, underscoring the urgent need for early diagnosis and differentiation among disorders with overlapping symptoms to guide optimal clinical treatment strategies. Lack of selective probes for detecting soluble amyloid β-oligomer and insoluble amyloid deposits, for example, amyloid β1-42, α-synuclein or Tau proteins, promotes the onset of disease. A variety of sensors are being developed using the Förster resonance transfer mechanism (FRET) effect. However, its efficacy depends on fluorophore donors. Dyes also suffer several drawbacks, including photobleaching, interference from the aggregates, overlapping and blinking effects. Upconversion nanoparticles (UCNPs) solve such issues by acting as alternative fluorescence donors and helping in treating and diagnosing NDs at early stages. In this article, we present the theranostic potential of UCNPs and their critical challenges, along with the future direction. We begin with upconversion sensing mechanism followed with different biomarker detection of NDs using upconversion approach.

HSP110 is a modulator of amyloid beta (Aβ) aggregation and proteotoxicity.

Chaperones safeguard protein homeostasis by promoting folding and preventing aggregation. HSP110 is a cytosolic chaperone that functions as a nucleotide exchange factor for the HSP70 cycle. Together with HSP70 and a J-domain protein (JDP), HSP110 maintains protein folding and resolubilizes aggregates. Interestingly, HSP110 is vital for the HSP70/110/JDP-mediated disaggregation of amyloidogenic proteins implicated in neurodegenerative diseases (i.e., α-synuclein, HTT, and tau). However, despite its abundance, HSP110 remains still an enigmatic chaperone, and its functional spectrum is not very well understood. Of note, the disaggregation activity of neurodegenerative disease-associated amyloid fibrils showed both beneficial and detrimental outcomes invivo. To gain a more comprehensive understanding of the chaperone HSP110 invivo, we analyzed its role in neuronal proteostasis and neurodegeneration in C. elegans. Specifically, we investigated the role of HSP110 in the regulation of amyloid beta peptide (Aβ) aggregation using an established Aβ-C. elegans model that mimics Alzheimer's disease pathology. We generated a novel C. elegans model that over-expresses hsp-110pan-neuronally, and we also depleted hsp-110 by RNAi-mediated knockdown. We assessed Aβ aggregation invivo and insitu by fluorescence lifetime imaging. We found that hsp-110 over-expression exacerbated Aβ aggregation and appeared to reduce the conformational variability of the Aβ aggregates, whereas hsp-110 depletion reduced aggregation more significantly in the IL2 neurons, which marked the onset of Aβ aggregation. HSP-110 also plays a central role in growth and fertility as its over-expression compromises nematode physiology. In addition, we found that HSP-110 modulation affects the autophagy pathway. While hsp-110 over-expression impairs the autophagic flux, a depletion enhances it. Thus, HSP-110 regulates multiple nodes of the proteostasis network to control amyloid protein aggregation, disaggregation, and autophagic clearance.

Saponins Effect on Human Insulin Amyloid Aggregation.

The misfolding and amyloid aggregation of proteins have been attracting scientific interest for a few decades, due to their link with several diseases, particularly neurodegenerative diseases. Proteins can assemble and result in insoluble aggregates that, together with intermediate oligomeric species, modify the extracellular environment. Many efforts have been and are devoted to the search for cosolvents and cosolutes able to interfere with amyloid aggregation. In this work, we intensively study the effect of saponins, bioactive compounds, on human insulin aggregation. To monitor the kinetic of amyloid aggregation following secondary structure changes, we perform fluorescence and UV-Visible absorption spectroscopies, using Thioflavin T and Congo Red as amyloid specific probes, and Circular Dichroism. To study the overall structural features and size of aggregates, we perform Synchrotron Small-Angle X-ray Scattering and Dynamic Light Scattering experiments. The morphology of the aggregates was assessed by Atomic Force Microscopy. To deepen the understanding of the saponins interaction with insulin, a Molecular Dynamics investigation is performed, too. The reported data demonstrate that saponins interfere with the amyloid aggregation by inducing a strong inhibition on the formation of insulin fibrils, likely through specific interactions with insulin monomers. A dose-dependent effect is evident, and amyloid inhibition is already clear when saponins are just 0.01% w/w in solution. We suggest that saponins, which are natural metabolites present in a wide range of foods ranging from grains, pulses, and green leaves to sea stars and cucumbers, can be promising metabolites to inhibit human insulin aggregation. This basic research work can pave the way to further investigations concerning insulin amyloidosis, suggesting the use of saponins as amyloid inhibitors and/or stabilizing agents in solution.

Fluid flow and amyloid transport and aggregation in the brain interstitial space.

The driving mechanisms at the base of the clearance of biological wastes in the brain interstitial space (ISS) are still poorly understood and an actively debated subject. A complete comprehension of the processes that lead to the aggregation of amyloid proteins in such environment, hallmark of the onset and progression of Alzheimer's disease, is of crucial relevance. Here we employ combined computational fluid dynamics and molecular dynamics techniques to uncover the role of fluid flow and proteins transport in the brain ISS. Our work identifies diffusion as the principal mechanism for amyloid-β proteins clearance, whereas fluid advection may lead transport for larger molecular bodies, like amyloid-β aggregates or extracellular vesicles. We also clearly quantify the impact of large nascent prefibrils on the fluid flowing and shearing. Finally, we show that, even in the irregular brain interstitial space (ISS), hydrodynamic interactions enhance amyloid-β aggregation at all stages of the aggregation pathway. Our results are key to understand the role of fluid flow and solvent-solute interplay on therapeutics like antibodies acting in the brain ISS.

Massively parallel genetic perturbation reveals the energetic architecture of an amyloid beta nucleation reaction.

Amyloid protein aggregates are pathological hallmarks of more than fifty human diseases but how soluble proteins nucleate to form amyloids is poorly understood. Here we use combinatorial mutagenesis, a kinetic selection assay, and machine learning to massively perturb the energetics of the nucleation reaction of amyloid beta (Aβ42), the protein that aggregates in Alzheimer's disease. In total, we quantify the nucleation rates of >140,000 variants of Aβ42. This allows us to accurately quantify the changes in reaction activation energy for all possible amino acid substitutions in a protein for the first time and, in addition, to quantify >600 energetic interactions between mutations. The data reveal the simple and interpretable genetic architecture of an amyloid nucleation reaction. Strikingly, strong energetic couplings are rare and identify a subset of structural contacts in mature fibrils. Together with the activation energy changes, this strongly suggests that the Aβ42 nucleation reaction transition state is structured in a short C-terminal region, providing a structural model for the reaction that may initiate Alzheimer's disease. We believe this approach can be widely applied to probe the energetics and transition state structures of protein reactions.

Anti-amyloid activity of amino acid functionalized magnetic nanoparticles on αLactalbumin aggregation

Protein amyloid aggregation involves structural changes in native protein conformers and the formation of amyloid fibrils that accumulate in deposits in the human body. This study explores the effect of magnetic nanoparticles functionalized with amino acids (aaMNPs)—cysteine (Cys), poly-L-lysine (PLL), or proline (Pro)—on the amyloid aggregation of α-lactalbumin (αLA) and its amyloid fibrils (LAF). Our results from thioflavin T fluorescence assay (ThT), atomic force microscopy (AFM), and infrared spectroscopy revealed that the studied aaMNPs inhibit αLA fibrillization and destruct LAF in a concentration-dependent manner. The type of amino acid used for nanoparticle functionalization significantly influences the anti-amyloid efficacy. ProMNPs exhibit the highest inhibitory activity, with the timing of their addition being crucial Conversely, CysMNPs demonstrate the highest destructing activity. AFM image analysis through grain mapping was employed to quantify the anti-amyloid effects of aaMNPs. Cytotoxicity testing on kidney cells identified PLLMNPs as the only cytotoxic nanoparticles in our study. These findings clarify the mechanisms of inhibition and destruction of LAF in the presence of aaMNPs, which could inform the design of nanoparticles for therapeutic purposes in the future.

SARS-CoV-2 and HSV-1 Induce Amyloid Aggregation in Human CSF Resulting in Drastic Soluble Protein Depletion.

The corona virus (SARS-CoV-2) pandemic and the resulting long-term neurological complications in patients, known as long COVID, have renewed interest in the correlation between viral infections and neurodegenerative brain disorders. While many viruses can reach the central nervous system (CNS) causing acute or chronic infections (such as herpes simplex virus 1, HSV-1), the lack of a clear mechanistic link between viruses and protein aggregation into amyloids, a characteristic of several neurodegenerative diseases, has rendered such a connection elusive. Recently, we showed that viruses can induce aggregation of purified amyloidogenic proteins via the direct physicochemical mechanism of heterogeneous nucleation (HEN). In the current study, we show that the incubation of HSV-1 and SARS-CoV-2 with human cerebrospinal fluid (CSF) leads to the amyloid aggregation of several proteins known to be involved in neurodegenerative diseases, such as APLP1 (amyloid β precursor like protein 1), ApoE, clusterin, α2-macroglobulin, PGK-1 (phosphoglycerate kinase 1), ceruloplasmin, nucleolin, 14-3-3, transthyretin, and vitronectin. Importantly, UV-inactivation of SARS-CoV-2 does not affect its ability to induce amyloid aggregation, as amyloid formation is dependent on viral surface catalysis via HEN and not its ability to replicate. Additionally, viral amyloid induction led to a dramatic drop in the soluble protein concentration in the CSF. Our results show that viruses can physically induce amyloid aggregation of proteins in human CSF and result in soluble protein depletion, thus providing a potential mechanism that may account for the association between persistent and latent/reactivating brain infections and neurodegenerative diseases.

Thioflavin-T: application as a neuronal body and nucleolar stain and the blue light photo enhancement effect

Thioflavin-T (THT) is a common and indispensable tool for the study of amyloid pathologies and protein aggregation, both in vitro and for histological samples. In this study we expand the use of THT beyond its canonical usage for staining amyloid plaques and demonstrate its novel use as an easy and rapid stain comparable to fluorescent Nissl staining, allowing for clear discernment of neuronal cell bodies and also nucleoli in fixed tissue and live cells. We believe that this is of value for any lab that studies central nervous system (CNS) tissues. Furthermore, we show that THT could potentially be used as a an alternative to the use of fluorescent reporters or other more costly RNA binding compounds in the study of nucleolar dynamics owing to its ability to clearly stain nucleoli in live cells. We also discovered the previously unreported effect of blue light exposure on the photo enhancement of THT excited by a 488 nm laser in stained tissue sample and how to avoid complications arising from this effect. Finally, we provide a simple protocol that can be easily adjusted either for using THT as a neuronal cell body and nucleoli stain, compatible with antibody based staining methods tested up to 4 fluorophores, or alternatively by using an additional washing step the protocol may be used for amyloid plaque detection in fixed brain tissue.

A novel biomimetic nanovesicle containing caffeic acid-coupled carbon quantum dots for the the treatment of Alzheimer's disease via nasal administration.

Alzheimer's disease (AD) is a common neurodegenerative disease characterized by progressive cognitive and physical impairment. Neuroinflammation is related to AD, and the misfolding and aggregation of amyloid protein in the brain creates an inflammatory microenvironment. Microglia are the predominant contributors to neuroinflammation, and abnormal activation of microglia induces the release of a large amount of inflammatory factors, promotes neuronal apoptosis, and leads to cognitive impairment. In this study, we used microglial membranes containing caffeic acid-coupled carbon quantum dots to prepare a novel biomimetic nanocapsule (CDs-CA-MGs) for the treatment of AD. The application of CDs-CA-MGs via nasal administration can bypass the blood‒brain barrier (BBB) and directly target the site of inflammation. After treatment with CDs-CA-MGs, AD mice showed reduced inflammation in the brain, decreased neuronal apoptosis, and significantly improved learning and memory abilities. In addition, CDs-CA-MGs affect inflammation-related JAK-STAT and Toll-like receptor signaling pathways in AD mice. CDs-CA-MGs significantly downregulated interleukins (IL-1β and IL-6) and tumor necrosis factor (TNF-α). This finding suggested that CDs-CA-MGs may improve cognitive impairment by modulating inflammatory responses. In conclusion, the use of CDs-CA-MGs provides a possible therapeutic strategy for the treatment of AD.

Structural features of skeletal muscle titin aggregates

Titin is a multidomain protein of striated and smooth muscles of vertebrates. The protein consists of repeating immunoglobulin-like (Ig) and fibronectin-like (FnIII) domains, which are β-sandwiches with a predominant β-structure, and also contains disordered regions. In this work, the methods of atomic force microscopy (AFM), X-ray diffraction and Fourier transform infrared spectroscopy were used to study the morphology and structure of aggregates of rabbit skeletal muscle titin obtained in two different solutions: 0.15 M glycine-KOH, pH 7.0 and 200 mM KCl, 10 mM imidazole, pH 7.0. According to AFM data, skeletal muscle titin formed amorphous aggregates of different morphology in the above two solutions. Amorphous aggregates of titin formed in a solution containing glycine consisted of much larger particles than aggregates of this protein formed in a solution containing KCl. The “KCl-aggregates” according to AFM data had the form of a “sponge”-like structure, while amorphous “glycine-aggregates” of titin formed “branching” structures. Spectrofluorometry revealed the ability of titin “glycine aggregates” to bind to the dye thioflavin T (TT), and X-ray diffraction revealed the presence of one of the elements of the amyloid cross β-structure, a reflection of ~4.6 Å, in these aggregates. These data indicate that the “glycine-aggregates” of titin are amyloid or amyloid-like. No similar structural features were found in titin “KCl-aggregates”; they also did not show the ability to bind to thioflavin T, indicating the non-amyloid nature of these titin aggregates. Fourier transform infrared spectroscopy revealed differences in the secondary structure of the two types of titin aggregates. The data obtained demonstrate the features of structural changes during the formation of intermolecular bonds between molecules of the giant titin protein during its aggregation. The data expand the understanding of the process of amyloid protein aggregation.

Temperature-Driven Stopped-Flow Experiments for Investigating the Initial Aggregation of the α-Synuclein Amyloid Protein, Focusing on Active and Inactive Phases.

The primary objective of this research is to further examine the events occurring during the active or burst phase by focusing on the aggregation of the Syn amyloid protein. Regarding this aspect, it was initially conducted rapid temperature variations using stopped-flow spectrometry and tyrosyl group fluorescence emission detection, within the initial 500 milliseconds in buffered Syn solutions at pH 7, exploring various temperature ranges to investigate protein aggregation. The results obtained were contrasted with results obtained for the Nα-acetyl-L-tyrosinamide (NAYA) parent compound in the same conditions. The utilization of the NAYA compound is suitable as it mimics the peptide bonds in proteins and contains a tyrosyl group resembling the four tyrosyl groups found in the Syn protein structure (the protein has no tryptophan residues). Furthermore, the NAYA compound adopts an intramolecularly hydrogen-bonded structure even in an aqueous solution, similar to the interactions seen in the hydrophilic face of β-sheets. Additionally, the Syn protein system can exhibit the presence of β-sheets as a result of the existence of very low abundant Syn amyloid precursor forms or nuclei during the initial stages of the protein aggregation. Thus, a relationship is present between the molecular processes in the NAYA and Syn protein systems, making the NAYA's application crucial in this research. Moreover, to aid in understanding the results, it was also compared the events during the quiescent or inactive phase (30-500 milliseconds) with those in the burst phase (up to 10 milliseconds) using stopped-flow spectrometry conditions. Steady-state measurements were beneficial in comprehending the occurrences in both the quiescent and burst phases examined. Although protein aggregation and disaggregation were observed during the quiescent phase, determining these processes in the burst phase was more challenging. In the latter case, the aggregation of the Syn protein is actually initiated by the interaction of the intrinsically disordered Syn monomers. In the quiescent phase, first-order rate constants were measured and analysis showed that Syn protein aggregation and disaggregation occur simultaneously. At lower temperatures, early protein disaggregation outweighs protein aggregation whereas at higher temperatures protein disaggregation and aggregation are rather similar. It is also need to highlight that the burst phase, while distinct from the quiescent phase, can be considered as a possible structural phase for obtaining details about the aggregation of this specific disordered protein in solution on a very short timescale.

Study of Insulin Aggregation and Fibril Structure under Different Environmental Conditions.

Protein amyloid aggregation is linked with widespread and fatal neurodegenerative disorders as well as several amyloidoses. Insulin, a small polypeptide hormone, is associated with injection-site amyloidosis and is a popular model protein for in vitro studies of amyloid aggregation processes as well as in the search for potential anti-amyloid compounds. Despite hundreds of studies conducted with this specific protein, the procedures used have employed a vast array of different means of achieving fibril formation. These conditions include the use of different solution components, pH values, ionic strengths, and other additives. In turn, this variety of conditions results in the generation of fibrils with different structures, morphologies and stabilities, which severely limits the possibility of cross-study comparisons as well as result interpretations. In this work, we examine the condition-structure relationship of insulin amyloid aggregation under a range of commonly used pH and ionic strength conditions as well as solution components. We demonstrate the correlation between the reaction solution properties and the resulting aggregation kinetic parameters, aggregate secondary structures, morphologies, stabilities and dye-binding modes.

Moment dynamics of oligomer formation in protein amyloid aggregation with secondary nucleation

The abnormal aggregation of proteins into amyloid fibrils, usually implemented by a series of biochemical reactions, is associated with various neurodegenerative disorders. Considering the intrinsic stochasticity in the involving biochemical reactions, a general chemical master equation model for describing the process from oligomer production to fibril formation is established, and then the lower-order statistical moments of different molecule species are captured by the derivative matching closed system, and the long-time accuracy is verified using the Gillespie algorithm. It is revealed that the aggregation of monomers into oligomers is highly dependent on the initial number of misfolded monomers; the formation of oligomers can be effectively inhibited by reducing the misfolding rate, the primary nucleation rate, elongation rate, and secondary nucleation rate; as the conversion rate decreases, the number of oligomers increases over a long time scale. In particular, sensitivity analysis shows that the quantities of oligomers are more sensitive to monomer production and protein misfolding; the secondary nucleation is more important than the primary nucleation in oligomer formation. These findings are helpful for understanding and predicting the dynamic mechanism of amyloid aggregation from the viewpoint of quantitative analysis.

Multifunctional carbonized polymer dots: Synthesis and applications in retarding protein amyloid aggregation, capturing free radicals and cell imaging

In this study, a series of carbonized polymer dots were synthesized using Congo red and tryptophan as carbon source by changing their molar ratio through simple one-step method in microwave oven. The prepared carbonized polymer dots could emit red fluorescence. All prepared carbonized polymer dots could inhibit the amyloid aggregation of human lysozyme and the CPDs-3 showed the best inhibition capability. The inhibition ratio of the CPDs-3 reached 95.8% at concentration of 40 μg/mL and the IC50 was 0.41 μg/mL, which may be attributed to the highest content of Congo red on the periphery of the CPDs-3. The CPDs-3 could easily interact with β-sheet structure of human lysozyme through π-π stacking and hydrophobic interaction, which helped to retard the amyloid aggregation. The CPDs-3 also displayed good anti-oxidative property and the highest elimination efficiency for hydroxyl free radical. In addition, the CPDs-3 showed nontoxicity on bEnd.3 cell by CCK-8 assay and could be used in cell imaging.

Amyloid‐based functional materials and their application in flexible sensors

AbstractFlexible electronic devices have garnered increasing attention for their applications in wearable devices, biomedical systems, soft robots, and flexible displays. However, the current sensors face limitations regarding low sensitivity, poor stability, and inadequate adhesion bonding between stimuli‐responsive functional materials and flexible substrates. To overcome these challenges and enable the further development of sensor devices, surface modification of stimuli‐responsive materials with amyloid aggregates has emerged as a promising approach to enhance functionality and create superior multifunctional sensors. This review presents recent research advancements in the flexible sensors based on protein amyloid aggregation. The article begins by explaining the basic principles of protein amyloid aggregation, followed by outlining the process of preparing 1D to 3D amyloid‐based composite materials. Finally, it discusses the utilization of protein amyloid aggregation as a surface modification technique for developing flexible sensors. Based on this foundation, we identify the shortcomings associated with protein amyloid aggregate composites and propose possible solutions to address them. We believe that comprehensive investigations in this area will expedite the development of high‐performance flexible sensors with high sensitivity, high structural stability, and strong interface adhesion, especially the implantable flexible sensors for health monitoring.

The Brain-Gut Axis, an Important Player in Alzheimer and Parkinson Disease: A Narrative Review.

Neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), are severe age-related disorders with complex and multifactorial causes. Recent research suggests a critical link between neurodegeneration and the gut microbiome, via the gut-brain communication pathway. This review examines the role of trimethylamine N-oxide (TMAO), a gut microbiota-derived metabolite, in the development of AD and PD, and investigates its interaction with microRNAs (miRNAs) along this bidirectional pathway. TMAO, which is produced from dietary metabolites like choline and carnitine, has been linked to increased neuroinflammation, protein misfolding, and cognitive decline. In AD, elevated TMAO levels are associated with amyloid-beta and tau pathologies, blood-brain barrier disruption, and neuronal death. TMAO can cross the blood-brain barrier and promote the aggregation of amyloid and tau proteins. Similarly, TMAO affects alpha-synuclein conformation and aggregation, a hallmark of PD. TMAO also activates pro-inflammatory pathways such as NF-kB signaling, exacerbating neuroinflammation further. Moreover, TMAO modulates the expression of various miRNAs that are involved in neurodegenerative processes. Thus, the gut microbiome-miRNA-brain axis represents a newly discovered mechanistic link between gut dysbiosis and neurodegeneration. MiRNAs regulate the key pathways involved in neuroinflammation, oxidative stress, and neuronal death, contributing to disease progression. As a direct consequence, specific miRNA signatures may serve as potential biomarkers for the early detection and monitoring of AD and PD progression. This review aims to elucidate the complex interrelationships between the gut microbiota, trimethylamine-N-oxide (TMAO), microRNAs (miRNAs), and the central nervous system, and the implications of these connections in neurodegenerative diseases. In this context, an overview of the current neuroradiology techniques available for studying neuroinflammation and of the animal models used to investigate these intricate pathologies will also be provided. In summary, a bulk of evidence supports the concept that modulating the gut-brain communication pathway through dietary changes, the manipulation of the microbiome, and/or miRNA-based therapies may offer novel approaches for implementing the treatment of debilitating neurological disorders.

Exercise to Counteract Alzheimer's Disease: What Do Fluid Biomarkers Say?

Neurodegenerative diseases (NDs) represent an unsolved problem to date with an ever-increasing population incidence. Particularly, Alzheimer's disease (AD) is the most widespread ND characterized by an accumulation of amyloid aggregates of beta-amyloid (Aβ) and Tau proteins that lead to neuronal death and subsequent cognitive decline. Although neuroimaging techniques are needed to diagnose AD, the investigation of biomarkers within body fluids could provide important information on neurodegeneration. Indeed, as there is no definitive solution for AD, the monitoring of these biomarkers is of strategic importance as they are useful for both diagnosing AD and assessing the progression of the neurodegenerative state. In this context, exercise is known to be an effective non-pharmacological management strategy for AD that can counteract cognitive decline and neurodegeneration. However, investigation of the concentration of fluid biomarkers in AD patients undergoing exercise protocols has led to unclear and often conflicting results, suggesting the need to clarify the role of exercise in modulating fluid biomarkers in AD. Therefore, this critical literature review aims to gather evidence on the main fluid biomarkers of AD and the modulatory effects of exercise to clarify the efficacy and usefulness of this non-pharmacological strategy in counteracting neurodegeneration in AD.

Aggregation Mechanisms and Molecular Structures of Amyloid-β in Alzheimer's Disease.

Amyloid plaques are a major pathological hallmark involved in Alzheimer's disease and consist of deposits of the amyloid-β peptide (Aβ). The aggregation process of Aβ is highly complex, which leads to polymorphous aggregates with different structures. In addition to aberrant aggregation, Aβ oligomers can undergo liquid-liquid phase separation (LLPS) and form dynamic condensates. It has been hypothesized that these amyloid liquid droplets affect and modulate amyloid fibril formation. In this review, we briefly introduce the relationship between stress granules and amyloid protein aggregation that is associated with neurodegenerative diseases. Then we highlight the regulatory role of LLPS in Aβ aggregation and discuss the potential relationship between Aβ phase transition and aggregation. Furthermore, we summarize the current structures of Aβ oligomers and amyloid fibrils, which have been determined using nuclear magnetic resonance (NMR) and cryo-electron microscopy (cryo-EM). The structural variations of Aβ aggregates provide an explanation for the different levels of toxicity, shed light on the aggregation mechanism and may pave the way towards structure-based drug design for both clinical diagnosis and treatment.

An NMR Toolkit to Probe Amyloid Oligomer Inhibition in Neurodegenerative Diseases: From Ligand Screening to Dissecting Binding Topology and Mechanisms of Action.

The aggregation of amyloid peptides and proteins into toxic oligomers is a hallmark of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Machado-Joseph's disease, and transmissible spongiform encephalopathies. Inhibition of amyloid oligomers formation and interactions with biological counterparts, as well as the triggering of non-toxic amorphous aggregates, are strategies towards preventive interventions against these pathologies. NMR spectroscopy addresses the need for structural characterization of amyloid proteins and their aggregates, their binding to inhibitors, and rapid screening of compound libraries for ligand identification. Here we briefly discuss the solution experiments constituting the NMR spectroscopist's toolkit and provide examples of their application.

Screening Carbon Nano Materials for Preventing Amyloid Protein Aggregation by Adopting a Facile Method.

The soluble-to-toxic transformation of intrinsically disordered amyloidogenic proteins such as amyloid beta (Aβ), α-synuclein, mutant Huntingtin Protein (mHTT) and islet amyloid polypeptide (IAPP) among others are associated with disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and Type 2 Diabetes (T2D), respectively. The dissolution of mature fibrils and toxic amyloidogenic intermediates, including oligomers, continues to be the pinnacle in the treatment of neurodegenerative disorders. Yet, methods to effectively and quantitatively report on the interconversion between amyloid monomers, oligomers and mature fibrils fall short. Here we describe a simplified method that implements the use of gel electrophoresis to address the transformation between soluble monomeric amyloid proteins and mature amyloid fibrils. The technique implements an optimized but well-known, simple, inexpensive, and quantitative assessment previously used to assess the oligomerization of amyloid monomers and subsequent amyloid fibrils. This method facilitates the screening of small molecules that disintegrate oligomers and fibrils into monomers, dimers, and trimers and/or retain amyloid proteins in their monomeric forms. Most importantly, our optimized method diminishes existing barriers associated with existing (alternative) techniques to evaluate fibril formation and intervention.