Biology subjects

Jasiqi, Y.

Publications and source records attributed to Jasiqi, Y..

7 recordsLinked to original sources

bioRxiv2026

Aggregate Deep Visual Proteomics reveals selective organization of α-synuclein inclusions

-Synuclein inclusions, the lesions typical of Parkinson's disease, have been interpreted as protective deposits, toxic species or failed degradation products, each predicting a different composition and correlating that enrichment with neuron dysfunction and eventual degeneration. Distinguishing them requires measuring what an inclusion concentrates relative to the cell that built it. Here we developed Aggregate Deep Visual Proteomics, which uses ultrasensitive mass spectrometry to profile laser-microdissected inclusions against the remainder of the same cell or a matched host. In HEK293 cells, iPSC-derived dopaminergic neurons and post-mortem patient brain, each inclusion concentrated a selective subset of its cell's proteome, independent of abundance and dominated by membrane, in neurons largely presynaptic. Inclusions took up whole assemblies, with subunits moving together in 421 of 438 complexes, and the V-ATPase alone was enriched in all three systems. Degradation cargo stayed with the receptors that route it, consistent with sequestration and failed degradation acting together. Neuritic and somatic inclusions differed, the former rich in UBQLN2 and the latter in intermediate filaments. In the cell line, phosphorylated -synuclein was tenfold higher in the inclusion than in the rest of the cell, with about one third of the rise already present before an inclusion was visible. Measured against its host, the composition of an inclusion becomes a readout of how it formed and a source of candidate markers and therapeutic targets.

biochemistry↗

bioRxiv2026

Fluorescent timer-based screening of protein turnover modulators in human neurons

Disturbances in protein homeostasis are a defining feature of aging and neurodegenerative diseases. However, current proteomics approaches do not enable screening-scale pharmacological interrogation of protein turnover in post-mitotic human neurons. Here we establish a Mammalian Cell-optimized Fluorescent Timer (MCFT)-based live-cell imaging platform to quantify global protein synthesis and degradation rates in human embryonic stem cell-derived neurons at screening scale. Among 5,897 tested compounds, 199 increased protein synthesis and degradation rates, and three selected compounds upregulated translation-associated genes in human neurons. We then tested their ability to suppress the accumulation of pathogenic -synuclein aggregates in models of Lewy body-like pathology. All three compounds induced efficient clearance of -synuclein aggregates in mouse primary neurons, and one compound demonstrated similar efficacy in human dopaminergic neurons. This platform provides a broadly applicable strategy for identifying biomedically-relevant compounds that enhance protein turnover across pluripotent stem cell-derived cellular models.

cell biology↗

bioRxiv2026

Viral rewiring of APC/C-CDC20 drives Aurora B hyperubiquitination, mitotic regression and polyploidy

Cytokinesis requires elaborate processes in the midbody, including the timely inactivation of Aurora B kinase (AurB) and membrane fission to separate the daughter cells. Here, we show that human adenovirus (AdV) perturbs midbody function, prevents daughter separation and induces cytoplasmic regression of both cancer cells and primary diploid human airway basal cells resulting in polyploidy. Infected cells undergo cleavage furrow regression after midbody formation driven by the viral protein E4orf4 independently of E4orf4 interaction with protein phosphatase 2A. The co-activator of the anaphase-promoting complex/cyclosome (APC/C), CDC20 is upregulated in AdV infection and required for regression. E4orf4 directly interacts with CDC20 and redirects the E3-ubiquitin ligase APC/C-CDC20 towards AurB, promoting hyperubiquitination and premature extraction of AurB from the midbody. Loss of midbody-associated AurB coincides with midbody collapse and furrow regression. Our findings reveal a previously unrecognized APC/C-CDC20-dependent pathway controlling late cytokinesis through AurB extraction from the midbody.

cell biology↗

bioRxiv2025

A Site-Specific Organometallic Approach for Installing Tyrosine Phosphorylation Mimics to Decipher the Role of Phosphorylation in Alpha-Synuclein (aSyn) Aggregation and Seeding

Several studies have identified phosphorylation of alpha-synuclein (aSyn) at multiple tyrosine residues (Y39, Y125, Y133, and Y136) within Lewy bodies, which are the pathological hallmarks of Parkinsons disease (PD). However, understanding the specific role of phosphorylation at each site, or how multiple phosphorylation sites interact, has been challenging. Herein, we present an efficient method that leverages an organometallic Pd-complex to site-specifically attach phosphomimetic groups via Cys-arylation, closely mimicking natural phosphorylation. Using this approach, we successfully incorporated native-like tyrosine phosphorylation mimics into cysteine-containing proteins like synthetic transcription factor Max and recombinant aSyn, in good yields. To demonstrate the methods versatility, we created a focused library of mono-, di-, and tri-phosphorylated aSyn analogues. This development enabled, for the first time, the investigation of the effect of site-specific phosphorylation at multiple C-terminal tyrosine residues on aSyn fibrillization and aggregation. Our results show that mono-phosphorylation at any of the C-terminal sites has little effect on aggregation, while di- and tri-phosphorylation slows down the process, extending the lag phase compared to wild-type aSyn. Additionally, phosphorylation at Y39 reduces the seeding activity of aSyn fibrils by almost threefold in both mammalian and neuronal models of synuclein pathology. Overall, our strategy provides a rapid, selective, and scalable way to introduce aromatic PTMs, producing homogeneous protein libraries essential for mechanistic studies, biomarker development, and exploring the therapeutic potential of targeting aSyn-phosphorylation for PD and related disorders.

biochemistry↗

bioRxiv2025

Recapitulating Parkinson's pathology in human iPSC dopaminergic neurons reveals new mechanistic insights into Lewy body formation and heterogeneity.

The accumulation of alpha-synuclein (aSyn) into intraneuronal inclusions of heterogeneous morphology, known as Lewy bodies (LB), is one of the defining diagnostic features of Parkinsons disease (PD); yet, our understanding of the mechanisms underpinning their formation and heterogeneity remains incomplete. Here, we present a human isogenic iPSC-derived dopaminergic neuron (iDA) model that faithfully recapitulates the diverse biochemical, morphological, and ultrastructural features of LB neuropathology in PD. Unlike other iDA seeding models, our model does not rely on aSyn overexpression, mutations, or genetic engineering, making it a more physiologically relevant system for studying PD. We demonstrate that the iDA model accurately reproduces the temporal relationships between neuritic and cell-body aSyn pathology, recapitulating the full biochemical spectrum, post-translational modifications (PTM), and morphological diversity of aSyn aggregates found in human PD tissue. Moreover, our work provides critical insight into how different pathways to aSyn fibrillization and the complex interaction between aSyn fibrils and membranous organelles influence the morphological diversity of LB-like inclusions. This model represents a versatile platform for investigating the mechanisms of pathology formation, maturation, and neuronal dysfunction, as well as supporting the development of diagnostics that capture the diversity of aSyn pathology in PD and related synucleinopathies.

neuroscience↗

bioRxiv2023

O-GlcNAc modification forces the formation of an α-Synuclein amyloid-strain with notably diminished seeding activity and pathology

The process of amyloid fibril formation remains one of the primary targets for developing diagnostics and treatments for several neurodegenerative diseases (NDDs). Amyloid-forming proteins such -Synuclein and Tau, which are implicated in the pathogenesis of Alzheimers and Parkinsons disease, can form different types of fibril structure, or strains, that exhibit distinct structures, toxic properties, seeding activities, and pathology spreading patterns in the brain. Therefore, understanding the molecular and structural determinants contributing to the formation of different amyloid strains or their distinct features could open new avenues for developing disease-specific diagnostics and therapies. In this work, we report that O-GlcNAc modification of -Synuclein monomers results in the formation of amyloid fibril with distinct core structure, as revealed by Cryo-EM, and diminished seeding activity in seeding-based neuronal and rodent models of Parkinsons disease. Although the mechanisms underpinning the seeding neutralization activity of the O-GlcNAc modified fibrils remain unclear, our in vitro mechanistic studies indicate that heat shock proteins interactions with O-GlcNAc fibril inhibit their seeding activity, suggesting that the O-GlcNAc modification may alter the interactome of the -Synuclein fibrils in ways that lead to reduce seeding activity in vivo. Our results show that post-translational modifications, such as O-GlcNAc modification, of -Synuclein are key determinants of -Synuclein amyloid strains and pathogenicity. These findings have significant implications for how we investigate and target amyloids in the brain and could possibly explain the lack of correlation between amyloid burden and neurodegeneration or cognitive decline in some subtypes of NDDs.

biochemistry↗

bioRxiv2022

Neighbouring modifications interfere with the detection of phosphorylated alpha-synuclein at Serine 129: Revisiting the specificity of pS129 antibodies

Alpha-synuclein (aSyn) within Lewy bodies, Lewy neurites, and other pathological hallmarks of Parkinsons disease and synucleinopathies have consistently been shown to accumulate in aggregated and phosphorylated forms of the protein, predominantly at Serine 129 (S129). Antibodies against phosphorylated S129 (pS129) have emerged as the primary tools to investigate, monitor, and quantify aSyn pathology in the brain and peripheral tissues. However, most of the antibodies and immunoassays aimed at detecting pS129-aSyn were developed based on the assumption that neighbouring post-translational modifications (PTMs) either do not co-occur with pS129 or do not influence its detection. Herein, we demonstrate that the co-occurrence of multiple pathology-associated C-terminal PTMs (e.g., phosphorylation at Tyrosine 125 or truncation at residue 133 or 135) differentially influences the detection of pS129-aSyn species by pS129-aSyn antibodies. These observations prompted us to systematically reassess the specificity of the most commonly used pS129 antibodies against monomeric and aggregated forms of pS129-aSyn in mouse brain slices, primary neurons, mammalian cells and seeding models of aSyn pathology formation. We identified two antibodies that are insensitive to pS129 neighbouring PTMs. However, consistent with previous reports, most pS129 antibodies showed cross-reactivity towards other proteins and often detected low and high molecular weight bands in aSyn knock-out samples that could be easily mistaken for monomeric or High Molecular Weight aggregates of aSyn. Our observations suggest that the pS129 antibodies do not capture the biochemical and morphological diversity of aSyn pathology. They also underscore the need for more specific pS129 antibodies, more thorough characterization and validation of existing antibodies, and the use of the appropriate protein standards and controls in future studies.

neuroscience↗