Secondary Nucleation of Aβ Revealed by Single-Molecule and Computational Approaches.

Understanding the mechanisms underlying amyloid-β (Aβ) aggregation is pivotal in the context of Alzheimer's disease. This study aims to elucidate the secondary nucleation process of Aβ42 peptides by combining experimental and computational methods. Using a newly developed nanopipette-based amyloid seeding and translocation assay, confocal fluorescence spectroscopy, and molecular dynamics simulations, the influence of the seed properties on Aβ aggregation is investigated.

Characterizing Prion-Like Protein Aggregation: Emerging Nanopore-Based Approaches.

Prion-like protein aggregation is characteristic of numerous neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. This process involves the formation of aggregates ranging from small and potentially neurotoxic oligomers to highly structured self-propagating amyloid fibrils. Various approaches are used to study protein aggregation, but they do not always provide continuous information on the polymorphic, transient, and heterogeneous species formed.

Ultrasensitive Detection of Aβ42 Seeds in Cerebrospinal Fluid with a Nanopipette-Based Real-Time Fast Amyloid Seeding and Translocation Assay.

In this work, early-stage Aβ42 aggregates were detected using a real-time fast amyloid seeding and translocation (RT-FAST) assay. Specifically, Aβ42 monomers were incubated in buffer solution with and without preformed Aβ42 seeds in a quartz nanopipette coated with L-DOPA. Then, formed Aβ42 aggregates were analyzed on flyby resistive pulse sensing at various incubation time points.

Aβ42 fibril and non-fibril oligomers characterization using a nanopipette.

The Aβ42 aggregates with different structures and morphology was investigated through a single molecule label-free technique. To this end, the quartz nanopipettes were functionalized with polyethylene glycol. The set of Aβ42- epigallocatechin-3-gallate fibrils with length (from 85 nm to 250 nm) obtained by sonication was detected.

Investigation of α-Synuclein and Amyloid-β(42)-E22Δ Oligomers Using SiN Nanopore Functionalized with L-Dopa.

Solid-state nanopores are an emerging technology used as a high-throughput, label-free analytical method for the characterization of protein aggregation in an aqueous solution. In this work, we used Levodopamine to coat a silicon nitride nanopore surface that was fabricated through a dielectric breakdown in order to reduce the unspecific adsorption. The coating of inner nanopore wall by investigation of the translocation of heparin.

Reg-1α, a New Substrate of Calpain-2 Depending on Its Glycosylation Status.

Reg-1α/lithostathine, a protein mainly associated with the digestive system, was previously shown to be overexpressed in the pre-clinical stages of Alzheimer's disease. In vitro, the glycosylated protein was reported to form fibrils at physiological pH following the proteolytic action of trypsin. However, the nature of the protease able to act in the central nervous system is unknown.

Loss of glucocorticoid receptor phosphorylation contributes to cognitive and neurocentric damages of the amyloid-β pathway.

Aberrant cortisol and activation of the glucocorticoid receptor (GR) play an essential role in age-related progression of Alzheimer's disease (AD). However, the GR pathways required for influencing the pathobiology of AD dementia remain unknown. To address this, we studied an early phase of AD-like progression in the well-established APP/PS1 mouse model combined with targeted mutations in the BDNF-dependent GR phosphorylation sites (serines 134/267) using molecular, behavioral and neuroimaging approaches.

Real-Time Fast Amyloid Seeding and Translocation of α-Synuclein with a Nanopipette.

The detection to α-synuclein (αS) assemblies as a biomarker of synucleinopathies is an important challenge for further development of an early diagnosis tool. Here, we present proof of concept real-time fast amyloid seeding and translocation (RT-FAST) based on a nanopipette that combines in one unique system a reaction vessel to accelerate the seed amplification and nanopore sensor for single-molecule αS assembly detection. RT-FAST allows the detection of the presence αS seeds WT and A53T variant in a given sample in only 90 min by adding a low quantity (35 μL at 100 nM) of recombinant αS for amplification.

Solid-state and polymer nanopores for protein sensing: A review.

In two decades, the solid state and polymer nanopores became attractive method for the protein sensing with high specificity and sensitivity. They also allow the characterization of conformational changes, unfolding, assembly and aggregation as well the following of enzymatic reaction. This review aims to provide an overview of the protein sensing regarding the technique of detection: the resistive pulse and ionic diodes.

Conical nanopores highlight the pro-aggregating effects of pyrimethanil fungicide on Aβ(1-42) peptides and dimeric splitting phenomena.

The Aβ(1-42) aggregation is a key event in the physiopathology of Alzheimer's disease (AD). Exogenous factors such as environmental pollutants, and more particularly pesticides, can corrupt Aβ(1-42) assembly and could influence the occurrence and pathophysiology of AD. However, pesticide involvement in the early stages of Aβ(1-42) aggregation is still unknown.

Detection of Amyloid-β Fibrils Using Track-Etched Nanopores: Effect of Geometry and Crowding.

Several neurodegenerative diseases have been linked to proteins or peptides that are prone to aggregate in different brain regions. Aggregation of amyloid-β (Aβ) peptides is recognized as the main cause of Alzheimer's disease (AD) progression, leading to the formation of toxic Aβ oligomers and amyloid fibrils. The molecular mechanism of Aβ aggregation is complex and still not fully understood.

Deconstructing Alzheimer's Disease: How to Bridge the Gap between Experimental Models and the Human Pathology?

Discovered more than a century ago, Alzheimer's disease (AD) is not only still present in our societies but has also become the most common dementia, with 50 million people worldwide affected by the disease. This number is expected to double in the next generation, and no cure is currently available to slow down or stop the disease progression. Recently, some advances were made due to the approval of the aducanumab treatment by the American Food and Drug Administration.

Prenatal exposure to low doses of fungicides corrupts neurogenesis in neonates.

Neurogenesis plays a crucial role during neurodevelopment and its dysfunction can lead to neurodevelopmental disorders. A recent hypothesis stipulates that exogenous factors could corrupt this process and predispose to neurodegenerative disorders later in life. The presence of pesticide residues in the diet represents a threat of which we have recently become aware of.

Machine Learning to Improve the Sensing of Biomolecules by Conical Track-Etched Nanopore.

Single nanopore is a powerful platform to detect, discriminate and identify biomacromolecules. Among the different devices, the conical nanopores obtained by the track-etched technique on a polymer film are stable and easy to functionalize. However, these advantages are hampered by their high aspect ratio that avoids the discrimination of similar samples.

Fungicide Residues Exposure and Aggregation in a Mouse Model of Alzheimer's Disease.

Background: Pesticide residues have contaminated our environment and nutrition over the last century. Although these compounds are present at very low concentrations, their long-term effects on human health is of concern. The link between pesticide residues and Alzheimer's disease is not clear and difficult to establish.

Glucocorticoid receptors signaling impairment potentiates amyloid-β oligomers-induced pathology in an acute model of Alzheimer's disease.

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis occurs early in Alzheimer's disease (AD), associated with elevated circulating glucocorticoids (GC) and glucocorticoid receptors (GR) signaling impairment. However, the precise role of GR in the pathophysiology of AD remains unclear. Using an acute model of AD induced by the intracerebroventricular injection of amyloid-β oligomers (oAβ), we analyzed cellular and behavioral hallmarks of AD, GR signaling pathways, processing of amyloid precursor protein, and enzymes involved in Tau phosphorylation.

High-Pressure Response of Amyloid Folds.

The abnormal protein aggregates in progressive neurodegenerative disorders, such as Alzheimer's, Parkinson's and prion diseases, adopt a generic structural form called amyloid fibrils. The precise amyloid fold can differ between patients and these differences are related to distinct neuropathological phenotypes of the diseases. A key focus in current research is the molecular mechanism governing such structural diversity, known as amyloid polymorphism.

Pressure Reveals Unique Conformational Features in Prion Protein Fibril Diversity.

The prion protein (PrP) misfolds and assembles into a wide spectrum of self-propagating quaternary structures, designated PrP. These various PrP superstructures can be functionally different, conferring clinically distinctive symptomatology, neuropathology and infectious character to the associated prion diseases. However, a satisfying molecular basis of PrP structural diversity is lacking in the literature.

Low doses of bioherbicide favour prion aggregation and propagation in vivo.

Public concerns over the use of synthetic pesticides are growing since many studies have shown their impact on human health. A new environmental movement in occidental countries promoting an organic agriculture favours the rebirth of botanical pesticides. These products confer an effective alternative to chemical pesticides such as glyphosate.

A Fluorescent Oligothiophene-Bis-Triazine ligand interacts with PrP fibrils and detects SDS-resistant oligomers in human prion diseases.

Background: Prion diseases are characterized by the accumulation in the central nervous system of an abnormally folded isoform of the prion protein, named PrP(Sc). Aggregation of PrP(Sc) into oligomers and fibrils is critically involved in the pathogenesis of prion diseases. Oligomers are supposed to be the key neurotoxic agents in prion disease, so modulation of prion aggregation pathways with small molecules can be a valuable strategy for studying prion pathogenicity and for developing new diagnostic and therapeutic approaches.

Getting to the core of prion superstructural variability.

The phenomenon of protein superstructural polymorphism has become the subject of increased research activity. Besides the relevance to explain the existence of multiple prion strains, such activity is partly driven by the recent finding that in many age-related neurodegenerative diseases highly ordered self-associated forms of peptides and proteins might be the structural basis of prion-like processes and strains giving rise to different disease phenotypes. Biophysical studies of prion strains have been hindered by a lack of tools to characterize inherently noncrystalline, heterogeneous and insoluble proteins.

The Volumetric Diversity of Misfolded Prion Protein Oligomers Revealed by Pressure Dissociation.

Protein oligomerization has been associated with a wide range of diseases. High pressure approaches offer a powerful tool for deciphering the underlying molecular mechanisms by revealing volume changes associated with the misfolding and assembly reactions. We applied high pressure to induce conformational changes in three distinct β-sheet-rich oligomers of the prion protein PrP, a protein characterized by a variety of infectious quaternary structures that can propagate stably and faithfully and cause diseases with specific phenotypic traits.

Interaction of prion protein with acetylcholinesterase: potential pathobiological implications in prion diseases.

Introduction: The prion protein (PrP) binds to various molecular partners, but little is known about their potential impact on the pathogenesis of prion diseases

Results: Here, we show that PrP can interact in vitro with acetylcholinesterase (AChE), a key protein of the cholinergic system in neural and non-neural tissues. This heterologous association induced aggregation of monomeric PrP and modified the structural properties of PrP amyloid fibrils. Following its recruitment into PrP fibrils, AChE loses its enzymatic activity and enhances PrP-mediated cytotoxicity.