Biology subjects

Klementieva, O.

Publications and source records attributed to Klementieva, O..

10 recordsLinked to original sources

bioRxiv2026

Structural and Functional Plasticity of the Staphylococcus aureus Virulence-Associated Amyloid Peptide PSMα1

Phenol-soluble modulin 1 (PSM1) is a cytolytic peptide secreted by Staphylococcus aureus that contributes to host-cell damage and biofilm stability, yet the relationship between its assembly behavior and function remains incompletely understood. Here, we combine cellular assays, molecular spectroscopy, and high-resolution structural approaches to elucidate how environmental conditions govern PSM1 activity and supramolecular organization. Live-cell imaging and cytotoxicity assays show that PSM1 accumulates at the plasma membrane of human cells prior to membrane permeabilization, linking membrane association to cytotoxic outcomes. This process is strongly attenuated by epigallocatechin gallate (EGCG). Cryogenic electron microscopy (cryo-EM) reveals two polymorphic canonical amyloid fibril architectures that share a conserved hydrophobic core and protofilament interface. In parallel, we identify pH as a key determinant of PSM1 assembly pathways, driving a bifurcation between cross-{beta} amyloid fibrils at extreme acidic and alkaline conditions and heterogeneous, long-lived, thermally stable -helical nanotubular assemblies at acidic, near-neutral, and slightly alkaline conditions, which act as transient intermediates under highly acidic conditions. Together, these findings demonstrate that PSM1 is not a single amyloid structure but a condition-dependent structural system in which environmental cues dictate assembly, membrane interaction, and cytotoxic function. This work provides a framework for understanding how polymorphic assembly of bacterial virulence peptides interfaces with host-cell interactions and suggests new avenues for targeting PSM-mediated pathogenicity. Statement of significanceStaphylococcus aureus causes severe infections and uses the peptide PSM1 to damage host cells and strengthen protective biofilms. Like many disease-associated proteins, PSM1 self-assembles into amyloid fibrils, though their role in virulence remains unclear. We show that PSM1 does not adopt a single architecture. Instead, environmental changes, such as those at infection sites, drive the peptide into distinct assemblies, including cross-{beta} amyloid fibrils and unexpectedly stable nanotubes with -helical features. Live-cell imaging shows PSM1 accumulates at the plasma membrane before cell death, and that epigallocatechin gallate reduces membrane association and toxicity. These findings show that bacterial virulence can be regulated through environmentally controlled transitions between protein assemblies, identifying membrane accumulation as a promising anti-virulence target.

biophysics↗

bioRxiv2026

Low-abundance αSyn-112 promotes αSyn-140 aggregation in vitro and forms immunoreactive deposits in Parkinson's disease brain tissue

The aggregation of -synuclein (Syn) is a molecular hallmark of Parkinsons disease (PD) and other synucleinopathies. Understanding the molecular mechanisms that determine the aggregation of this protein may thus facilitate the development of disease-modifying therapies. While Syn is most commonly expressed as a 140-residue protein (Syn-140), recent evidence suggests an involvement of alternatively spliced Syn isoforms in disease onset and progression. Here, we report and characterise the interaction between Syn-140 and the aggregation-prone Syn-112 variant, one of the most abundant Syn splice isoforms. We found that amounts as low as 1% of Syn-112 accelerate the nucleation and aggregation of Syn-140. To further investigate this phenomenon, we employed MALDI-MS and NMR spectroscopy, confirming that Syn-140 and Syn-112 monomers interact strongly with one another. Furthermore, to assess the association of Syn-112 with disease pathology, we performed immunohistochemical staining combined with confocal microscopy on PD brain samples. Thereby, we found an increase in the number as well as the area of Syn-112 immunoreactive aggregates compared to healthy controls. These results illustrate how low-abundance Syn splice isoforms can modulate the aggregation landscape of Syn-140 and in turn contribute to the molecular heterogeneity of synucleinopathies.

biophysics↗

bioRxiv2026

Neuronal age drives β-sheet accumulation and, together with ApoE4, enhances synaptic Aβ localization in APPNL-F neurons

Amyloid-{beta} (A{beta}) accumulation and aggregation are defining features of Alzheimers disease (AD), but the earliest cellular events driving these processes remain poorly understood. Here, we investigate A{beta} dynamics in primary neurons derived from APPNL-F knock-in mice, which express human APP and A{beta} at endogenous (non-overexpressed) levels. Using correlative optical photothermal infrared (OPTIR) spectromicroscopy and immunofluorescence, we show that physiological APPNL-F expression is sufficient to drive intraneuronal A{beta} accumulation at synapses. Modelling neuronal aging through prolonged culture reveals a marked increase in synaptic A{beta} burden accompanied by {beta}-sheet-rich structural transitions Supplementation with astrocyte-derived apolipoprotein E (ApoE) isoforms demonstrates that ApoE4 markedly increases synaptic A{beta} accumulation while reducing {beta}-sheet content relative to untreated cultures, suggesting a potential shift toward less fibrillar species. Together, these findings establish APPNL-F neurons as a physiologically relevant system for dissecting early A{beta} pathology and show that both A{beta} quantity (accumulation) and quality (structural maturation) are regulated by aging and ApoE genotype. This work provides mechanistic insight into the earliest molecular events that may underlie synaptic vulnerability in AD.

neuroscience↗

bioRxiv2025

Microplastic Exposure Promotes Amyloid Misfolding and Metabolic Impairment at Sub-Lethal Doses in an In Vitro Cellular Model of Alzheimer's Disease

Microplastics and nanoplastics (MNPs) are ubiquitous environmental pollutants with increasing implications for human health. While their presence in human tissues is established, the molecular mechanisms driving their potential neurotoxicity remain unclear. This study investigates the impact of polystyrene (PS) on amyloid protein misfolding and cellular metabolism using Optical Photothermal Infrared (O-PTIR) spectroscopy, a label-free, sub-diffraction imaging technique. Our results reveal that PS exposure promotes pathological protein misfolding, specifically increasing {beta}-sheet-rich conformations, and disrupts metabolic homeostasis at sub-lethal doses. These suggest that the microplastic surface acts as a catalytic scaffold for amyloid aggregation, driving cellular dysfunction prior to acute toxicity. This identifies a plausible molecular pathway by which environmental MNP pollution contributes to the risk and progression of neurodegenerative diseases, highlighting the need for risk assessments that look beyond simple cell survival.

biochemistry↗

bioRxiv2025

Mid-Infrared Photothermal Mesoscopy with Millimeter Field of View and Sub-micron Spatial Resolution

By optically sensing mid-infrared absorption through a visible probe beam, mid-infrared photothermal (MIP) microscopy has emerged as a powerful tool for chemical imaging with micromolar sensitivity and submicron spatial resolution. The adoption of spatially multiplexed camera-based widefield detection further enhanced the imaging speed. However, current widefield MIP systems suffer from a small field of view (FOV)--typically tens of square micrometers, which constrains their utility in large-area tissue imaging applications. Here, we report a laser-scan MIP mesoscope that achieves millimeter-scale FOV while preserving submicron resolution. By leveraging an all-reflective laser scanning architecture, low-magnification and medium numerical-aperture objectives, and a defocused signal collection scheme, our MIP mesoscope achieves a 1.2 x 1.2 mm2 FOV, 650 nm lateral resolution, and microsecond-scale pixel dwell time. In vivo chemical imaging of whole Caenorhabditis elegans and high-throughput detection of beta-amyloids in both mouse and human brain tissues associated with Alzheimers disease are demonstrated.

bioengineering↗

bioRxiv2025

Galectin-3 deletion modulates microglial phenotype and Aβ response via TREM2 activation while attenuating neuroinflammation

Neuroinflammation is a hallmark of Alzheimers disease (AD), yet the molecular mediators driving microglial dysfunction and neurotoxicity remain poorly understood. Here, we identify Galectin-3 (Gal3) as a central regulator of plaque-associated microglial responses, linking amyloid-beta (A{beta}) aggregation, lysosomal function and plaque-associated neuritic damage. Using postmortem brain tissue from AD patients, we demonstrated that Gal3 microglia are selectively enriched around highly immunogenic dense-core plaques, and correlate with increased LAMP1+ dystrophic neurites. Notably, Gal3 was also detected in extra-microglial dystrophic structures and in close association with extracellular amyloid fibrils, suggesting a role in both intracellular and extracellular A{beta} dynamics. In APP mice, Gal3 deficiency resulted in more compact plaques, reduced neuronal dystrophies and increased TREM2 expression around amyloid plaques, suggesting altered plaque-associated microglial responses. Mechanistically, in vitro studies revealed that Gal3 modulates A{beta} uptake and its intracellular processing while lysosomal stress conditions showed increased A{beta} fibrillation from monomeric species in Gal3-deficient microglia. In parallel, cell-free assays demonstrated that Gal3 directly interacts with A{beta} and selectively inhibits secondary nucleation, thereby stabilizing intermediate assemblies associated with increased neurotoxic potential. Finally, in silico and transcriptomic analysis revealed that Gal3 interacts with key immune receptor patterns, having leucine-rich repeats as well as immunoglobulin-like domains. Moreover, Gal3 favors pro-inflammatory microglial programs, while its deletion suppresses type I interferon and microglial neurodegenerative (MGnD) signatures. Together, these findings position Gal3 as a central regulator of amyloid aggregation, lysosomal dysfunction, and microglial activation, driving a neurotoxic phase of AD and highlighting a potential therapeutic window for intervention. Significance StatementNeuroinflammation and amyloid-beta (A{beta}) plaques drive Alzheimers disease progression, but the molecular bridges between plaque formation, microglial dysfunction, and neurodegeneration remain unclear. This study identifies Galectin-3 (Gal3) as a pivotal regulator at this interface. We demonstrate that Gal3 is enriched around amyloid dense-core plaques in human brains and directly shapes A{beta} aggregation into highly neurotoxic intermediate structures. Genetic deletion of Gal3 in Alzheimers mouse models reduces nerve cell damage and change microglial cells toward a protective, less inflammatory state. By linking extracellular protein aggregation with intracellular lysosomal stress and inflammatory gene expression, these findings establish Gal3 as a major driver of Alzheimers neurotoxicity and highlight it as a promising therapeutic target

neuroscience↗

bioRxiv2024

Generating human parvalbumin interneurons through 3D glia reprogramming

Parvalbumin (PV) interneurons are crucial for synaptic plasticity, and their damage or loss is linked to various neurological disorders. Yet, generating these cells of human source in vitro is challenging, limiting advancements in cell repair and disease modelling. We introduce a novel approach to derive human PV neurons through direct reprogramming of glial precursor cells (GPCs). Using ectopic expression of GABAergic neuronal genes, GPCs efficiently convert into GABAergic interneurons in 3D culture environment within weeks and achieve functional neuronal maturity. Single-nuclei RNA sequencing identified a distinct PV neuronal cluster with high maturity and characteristics of PV chandelier subclass that are equivalent to bona fide human interneurons. Trajectory analysis revealed a distinct glia-to-PV interneuron conversion pathway, involving several new transitory genes, with potential for functional importance for PV derivation. Our data introduces a new strategy for generating human PV interneurons, promising significant implications for future generation of patient-specific PV neurons both in vitro and in vivo. HighlightsO_LIA novel approach to derive human PV interneurons by direct glia reprogramming. C_LIO_LIFirst comprehensive transcriptomic profiling of induced human PV interneurons. C_LIO_LIInduced PV interneurons are of chandelier subtype with transcriptional similarity to bona fide interneurons. C_LIO_LISuccessful glia-to-PV interneuron conversion passes through a specific reprogramming trajectory and involves key genes with functional potential. C_LI

neuroscience↗

bioRxiv2023

Proteomic analysis across patient iPSC-based models and human post-mortem hippocampal tissue reveals early cellular dysfunction, progression, and prion-like spread of Alzheimer s disease pathogenesis

The hippocampus is a primary region affected in Alzheimers disease (AD). Because AD postmortem brain tissue is not available prior to symptomatic stage, we lack understanding of early cellular pathogenic mechanisms. To address this issue, we examined the cellular origin and progression of AD pathogenesis in patient-based model systems including iPSC-derived brain cells transplanted into the mouse brain hippocampus. Notably, proteomic analysis of the graft enabled the identification of proteomic alterations in AD patient brain cells, associated with increased levels of {beta}-sheet structures and A{beta}42 peptides. Interestingly, the host cells surrounding the AD graft also presented alterations in cellular biological pathways. Furthermore, proteomic analysis across human iPSC-based models and human post-mortem hippocampal tissue projected coherent longitudinal cellular changes indicative of disease progression from early to end stage AD. Our data showcase patient-based models to study the cellular origin, progression, and prion-like spread of AD pathogenesis. Highlights- AD patient iPSC-derived brain cells survive in the hippocampus of immunodeficient mice 6 months post-transplantation. - Proteomic analysis of the grafts reveals profound alterations in cellular biological pathways in iPSC-derived hippocampal cells despite absence of senile plaques. - Proteomic alterations within transplanted AD iPSC-derived hippocampal cells are reminiscent of early/prodromal AD. - AD-grafted cells induce proteomic changes in host mouse cells.

neuroscience↗

bioRxiv2023

Label-free high-resolution infrared spectroscopy for spatiotemporal analysis of complex living systems

Label-free chemical and structural imaging of complex living tissue and biological systems is the holy grail of biomedical research and clinical diagnostics. The current analysis techniques are time-consuming and/or require extensive sample preparation, often due to the presence of interfering molecules such as water, making them unsuitable for the analysis of such systems. Here, we demonstrate a proof-of-principle study using label-free optical photothermal mid-infrared microspectroscopy (O-PTIR) for fast, direct spatiotemporal chemical analysis of complex living biological systems at submicron resolution. While other analytical methods can provide only static snapshots of molecular structures, our O-PTIR approach enables time-resolved and in situ investigation of chemical and structural changes of diverse biomolecules in their native conditions. This comprises a technological breakthrough in infrared spectroscopy to analyze biomolecules under native conditions over time: in fresh unprocessed biopsies, living brain tissue, and vertebrates without compromising their viability. One-Sentence SummaryProof-of-principle application of non-destructive O-PTIR for high-resolution spatiotemporal chemical and structural analysis of unprocessed biopsies, living brain tissue, and vertebrates.

molecular biology↗

bioRxiv2022

INFLAMMATORY BOWEL DISEASE INDUCES α-SYNUCLEIN AGGREGATION IN GUT AND BRAIN

According to Braaks hypothesis, it is plausible that Parkinso[n]s disease (PD) starts in the enteric nervous system (ENS) to spread the brain via the vagus nerve. Thus, we were wondering whether human inflammatory bowel diseases (IBD) can progress with appearance of pathogenic -synuclein (-syn) in the gastrointestinal tract and midbrain dopaminergic neurons. Analysis of human gastrointestinal tract sections from IBD patients demonstrated the presence of pathogenic phosphorylated -syn in both myenteric (Auerbachs) and submucosal (Meissners) plexuses. Remarkably, PD subjects exhibit -syn pathology in identical gastrointestinal locations. Analysis of human midbrain sections from IBD subjects revealed a clear displacement of neuromelanin in some nigral neurons from the ventral mesencephalon, which were inherently associated with presence of -syn aggregates reminiscent of pale bodies. We also used different dextran sodium sulfate (DSS)-based rat models of gut inflammation (subchronic and chronic) to study the appearance of phosphorylated -syn inclusions in both Auerbachs and Meissners plexuses (gut), and in dopaminergic neuritic processes (brain) along with degeneration of nigral dopaminergic neurons, which are considered classical hallmarks of PD. Vagotomized DSS-treated animals exhibited pathological -syn in the gut but failed to show dopaminergic cells degeneration and -syn aggregation in the ventral mesencephalon. Taken together, these results strongly suggest that Braaks hypothesis is plausible.

neuroscience↗