bims-proned 2026-05-10 papers

bims-proned

Biomed News

on Proteostasis in neurodegeneration

Issue of 2026–05–10
eleven papers selected by
Verena Kohler, Umeå University

Condensate State as Determinant of Amyloid Pathology in Neurodegeneration.
Amyloid-β, Tau Protein, α-Synuclein, TDP-43, and FUS in Mixed Pathology: And Intrinsic Disorder to Rule Them All.
Copper Overload Affects α-Synuclein Clearance Mechanisms in a Parkinson's Disease In Vitro Model.
Mitochondria serve as a holdout compartment for aggregation-prone proteins hindering efficient degradation.
Mutational Scanning of α-Synuclein using a Clickable Protein Tag Reveals Determinants of Membrane-Induced Aggregation.
Modulation of Biomolecular Aggregate Morphology and Condensate Infectivity.
Exploring the role of phase separation in TDP-43 pathogenesis with ArtiTDP43.
A high-content imaging workflow to screen for molecules that reduce cellular uptake of α-synuclein preformed fibrils.
Complement Dysregulation During the Early Phases of Synucleinopathy.
Cysteines are critical determinants of spontaneous and seeded tau aggregation in cells.
The Role of Phospho-ubiquitin in Mitochondrial Health and Diseases.

Biomolecules. 2026 Apr 10. pii: 560. [Epub ahead of print]16(4):

Condensate State as Determinant of Amyloid Pathology in Neurodegeneration.

Lathan Lucas, Josephine C Ferreon, Allan Chris M Ferreon.

  Neurodegenerative diseases arise when normally functional aggregation-prone proteins transition into stable cross-β amyloid fibrils. Although these fibrils share a conserved architecture, the pathways that lead to fibrillation vary across proteins and cellular environments. Liquid-liquid phase separation is now recognized as a central organizer of intracellular biochemistry that modulates protein aggregation. Physiological condensation can buffer aggregation by maintaining macromolecular solubility and providing partner interactions that compete against pathological protein-protein interactions. However, condensates can transform and age into gel-like states that can favor the emergence of β-rich oligomers and solid-state fibrils. Across six disease-linked proteins that include Tau, α-synuclein, amyloid-β, TDP-43, FUS, and hnRNPA1, we compare how sequence-encoded interaction motifs, cellular cofactors, and interfacial microenvironments shape the balance between physiological condensates and pathological amyloids. Here, we highlight the unifying drivers of aggregation and intervention points that preserve native function while limiting toxic amyloid formation.

Keywords:  FUS; TDP-43; Tau; amyloid-β; amyloids; biomolecular condensates; fibrillation; hnRNPA1; neurodegeneration; α-synuclein

DOI:  https://doi.org/10.3390/biom16040560
Int J Mol Sci. 2026 Apr 20. pii: 3669. [Epub ahead of print]27(8):

Amyloid-β, Tau Protein, α-Synuclein, TDP-43, and FUS in Mixed Pathology: And Intrinsic Disorder to Rule Them All.

Alex S Siebner, Vladimir N Uversky.

  Neurodegenerative diseases, including Alzheimer's Disease (AD), Parkinson's Disease (PD), Lewy Body Disease (LBD), and related dementias, represent a global health challenge, particularly in aging populations. The simultaneous occurrence of neurodegenerative diseases in an aging population suggests a potential link between causative proteins. Such neurodegenerative proteins, including amyloid-β (Aβ), τ-protein (tau), α-synuclein, TAR DNA-binding protein 43 (TDP-43), and Fused in Sarcoma (FUS), share key characteristics of intrinsically disordered proteins (IDPs), which can explain promiscuous physical interactions, cross-seeding, co-occurrence, pathological synergy, and shared upstream and downstream mechanisms. This review synthesizes current evidence on (1) shared biophysical features of neurodegeneration-associated proteins, (2) mechanisms driving mixed neuropathology, (3) therapeutic implications of disorder-driven interactions, and (4) key unresolved questions shaping future research. By framing neurodegeneration as a network of interacting, disorder-driven proteinopathies rather than isolated entities, this perspective highlights the need for integrative, systems-level approaches to better understand disease heterogeneity and to identify novel targets for intervention.

Keywords:  FUS; TDP-43; amyloid-β; liquid–liquid phase separation; neurodegeneration; protein intrinsic disorder; proteinopathies; tau; α-synuclein

DOI:  https://doi.org/10.3390/ijms27083669
Adv Biol (Weinh). 2026 May;10(5): e00274

Copper Overload Affects α-Synuclein Clearance Mechanisms in a Parkinson's Disease In Vitro Model.

Debora Musarò, Marina Damato, Chiara Coppola, Marco Greco, Michele Maffia.

  Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta and the formation of Lewy bodies, abnormal protein aggregates primarily composed of α-synuclein. Copper, an essential trace element, plays a role in α-synuclein aggregation and PD pathogenesis. This study examines the effects of copper overload on α-synuclein clearance pathways, focusing on autophagy and the ubiquitin-proteasome system (UPS) in dopaminergic SH-SY5Y neuroblastoma cells. Copper exposure enhances autophagosome formation, as indicated by increased Beclin-1 and LC3-II levels, and impairs autophagic flux, evidenced by LC3-II accumulation in the presence of chloroquine. Concurrently, copper increases polyubiquitinated proteins, suggesting UPS dysfunction, which is confirmed through MG132 treatment. These disruptions lead to the accumulation and aggregation of α-synuclein, particularly in its phosphorylated form. Immunofluorescence reveals neurite-localized α-synuclein aggregates, consistent with copper's role in α-synuclein pathology. This study highlights copper dyshomeostasis as a contributor to impaired α-synuclein clearance through autophagy and UPS dysfunction, advancing the understanding of PD's molecular basis.

Keywords:  Parkinson's disease; alpha‐synuclein; autophagy; copper

DOI:  https://doi.org/10.1002/adbi.202500274
Nat Commun. 2026 05 07. pii: 4195. [Epub ahead of print]17(1):

Mitochondria serve as a holdout compartment for aggregation-prone proteins hindering efficient degradation.

Maria E Gierisch, Enrica Barchi, Mirco Marogna, Moritz H Wallnöfer, Maria Ankarcrona, Luana Naia, Florian A Salomons, Nico P Dantuma.

The accumulation of protein aggregates has been causatively linked to the pathogenesis of neurodegenerative diseases. Here, we conduct a genome-wide CRISPR-Cas9 screen to identify cellular factors that regulate the degradation of an aggregation-prone reporter. Genes encoding proteins involved in mitochondrial homeostasis, including the translation factor eIF5A, are enriched among suppressors of the degradation of the reporter. Genetic or chemical inhibition of eIF5A leads to dissociation of the aggregation-prone substrate from mitochondria, which is accompanied by enhanced ubiquitin-dependent proteasomal degradation. The presence of an aggregation-prone, amphipathic helix that localizes the reporter to mitochondria is crucial for the stimulatory effect of eIF5A inhibition on proteasomal degradation. Additionally, inhibition of eIF5A also enhances degradation of mutant huntingtin and α-synuclein, two disease-associated proteins that contain amphipathic helices and mislocalize to mitochondria. We propose that mitochondria serve as a holdout compartment for aggregation-prone proteins. Therefore, preventing mitochondrial localization of aggregation-prone proteins may offer a viable therapeutic strategy for reducing disease-associated proteins in neurodegenerative disorders.

DOI: https://doi.org/10.1038/s41467-026-72783-0
bioRxiv. 2026 Apr 23. pii: 2026.04.20.719647. [Epub ahead of print]

Mutational Scanning of α-Synuclein using a Clickable Protein Tag Reveals Determinants of Membrane-Induced Aggregation.

Daeun Noh, Robert W Newberry.

The cellular environment plays a critical role in shaping protein conformations, including aggregated states implicated in disease. One challenge to studying this relationship is that most techniques offering high-resolution insight into the nature of these aggregates cannot be deployed in living cells. Systematic mutagenesis presents an opportunity to bridge this gap but requires general and robust methods to detect protein aggregation across large numbers of variants. Here, we use clickable protein tags to generate FRET pairs in situ that can report protein aggregation in high throughput in living cells. We applied this strategy to probe the nature of cellular inclusions of α-synuclein in a popular yeast model. Our results demonstrate that cellular aggregates of α-synuclein in yeast are likely dominated by protein-membrane interactions, making the aggregation pathway in this cellular model very different than in many in vitro experiments. Furthermore, our comprehensive mutational data reveal the molecular determinants of membrane-induced aggregation. For example, residues that control membrane affinity have a profound effect on membrane-induced aggregation both in vitro and in cells. Furthermore, we discovered that glycine residues, particularly in the central region of the protein, act as gatekeepers to reduce membrane-induced aggregation. Mutational scanning with a clickable protein tag therefore provides high-resolution insights into cellular protein aggregates.

DOI: https://doi.org/10.64898/2026.04.20.719647
Biomolecules. 2026 Mar 25. pii: 492. [Epub ahead of print]16(4):

Modulation of Biomolecular Aggregate Morphology and Condensate Infectivity.

Josephine C Ferreon, Kyoung-Jae Choi, My Diem Quan, Phoebe S Tsoi, Cristopher C Ferreon, Ulas Coskun, Shih-Chu Jeff Liao, Allan Chris M Ferreon.

  Neurodegenerative diseases feature diverse pathological protein aggregates, including Lewy bodies in Alzheimer's disease (AD) and skein-like filaments in amyotrophic lateral sclerosis (ALS). The physical mechanisms underlying this morphological diversity remain unclear. Here, we demonstrate that aggregation of the prion-like domain of hnRNPA1 (A1PrD), implicated in AD and ALS, is driven by solution composition and phase transition dynamics. Utilizing 3D timelapse and fluorescence lifetime imaging microscopy, we show that solution conditions modulate phase separation, gelation, and fibrillation, resulting in distinct structures such as fibril, gel, and starburst morphologies. Homotypic and heterotypic interactions between A1PrD and RNA were observed to shift the balance between pathological and physiological condensates. Importantly, amyloid-rich starbursts displayed prion-like infection capabilities toward amyloid-poor condensates. Our findings highlight how the interplay between solution composition and kinetic balances of liquid-liquid phase separation, gelation, and fibrillation shapes the diverse pathological aggregate morphologies characteristic of neurodegenerative diseases.

Keywords:  ALS; Alzheimer’s disease; FLIM; LLPS; aggregation; biomolecular condensates; fibrillation; hnRNPA1; phase transitions; prion-like domain

DOI:  https://doi.org/10.3390/biom16040492
FEBS J. 2026 May 02.

Exploring the role of phase separation in TDP-43 pathogenesis with ArtiTDP43.

Eric Chevet.

  TDP-43 is a nuclear RNA-binding protein implicated in neurodegenerative diseases such as ALS and FTLD, where it becomes mislocalized to the cytoplasm and forms pathological aggregates. These aggregates are thought to arise through liquid-liquid phase separation, a process by which proteins form dynamic, membrane-less condensates that can mature into solid structures. To better understand this process, the authors developed ArtiTDP43, a chemically controllable system that enables reversible formation of TDP-43 condensates in cells. Using this tool, they showed that TDP-43 forms different structures depending on its concentration: small liquid-like puncta, intermediate condensates associated with stress granules, and large solid aggregates resembling disease pathology. These transitions are reversible at early stages but become irreversible as aggregates solidify. The study by Combe et al. demonstrates that increasing cytoplasmic TDP-43 concentration drives a liquid-to-solid transition, while oxidative stress accelerates this process and promotes pathological features such as phosphorylation and p62 recruitment. Importantly, formation of cytoplasmic aggregates leads to depletion of nuclear TDP-43 and increased cell death, indicating toxicity. Overall, the findings establish a mechanistic link between phase separation, aggregation, and cytotoxicity in TDP-43 proteinopathies. ArtiTDP43 provides a powerful tool to study early disease mechanisms and explore therapeutic strategies aimed at preventing pathological aggregation or maintaining normal TDP-43 dynamics.

Keywords:  ALS; ArtiTDP‐43; FTLD; LLPS; TDP‐43; aggregation; condensates; cytotoxicity; oxidative stress; phase separation

DOI:  https://doi.org/10.1111/febs.70577
Methods. 2026 May 05. pii: S1046-2023(26)00113-1. [Epub ahead of print]

A high-content imaging workflow to screen for molecules that reduce cellular uptake of α-synuclein preformed fibrils.

Wolfgang E Reintsch, Andrea I Krahn, Chanshuai Han, Emmanuelle Nguyen-Renou, Carol X-Q Chen, Wen Luo, Irina Shlaifer, Tom Pfeifer, Edward A Fon, Thomas M Durcan.

  A classical pathological hallmark of many neurodegenerative diseases is the formation of protein-rich aggregates and inclusions. In Parkinson's disease (PD), α-synuclein (α-syn) constitutes a major protein component of pathological inclusions, termed Lewy bodies. These α-syn aggregates are hypothesized to spread throughout the nervous system by cell-to-cell transmission acting as templates to amplify aggregate formation. In vitro generated α-syn aggregates, commonly called preformed fibrils (PFFs), have been used to investigate a number of aspects related to α-syn mediated pathology across different model systems. Here we describe a semi-automated assay to screen for small molecules that interfere with the cellular uptake and accumulation of PFFs. The assay uses dopaminergic progenitor cells (DPCs), derived from human induced pluripotent stem cells (hiPSCs). In an initial screen, we tested 1520 small molecules and identified several molecules that strongly reduce intracellular PFF load in DPCs. From these hits, candidate compounds were validated in dopaminergic neurons (DNs) to demonstrate the utility of the assay. This assay provides a robust, scalable and adaptable tool to screen for molecules that affect PFF uptake in hiPSC-derived cell models. Within the scope of this screen, it led to the identification of a set of compounds with diverse annotated targets that effectively reduce the accumulation of α-syn aggregates in DPCs and DNs.

Keywords:  Dopaminergic neurons; High content screening; Human induced pluripotent stem cells; PFF uptake; Parkinson; α-Synuclein preformed fibrils (PFF)

DOI:  https://doi.org/10.1016/j.ymeth.2026.05.001
bioRxiv. 2026 Apr 30. pii: 2026.04.27.720696. [Epub ahead of print]

Complement Dysregulation During the Early Phases of Synucleinopathy.

Hina Khan, Mary Gifford, Arash Kordbacheh, Asher Bury, Spencer Panoushek, Allyson Cole-Strauss, Christopher J Kemp, Kelvin C Luk, Kathy Steece-Collier, Nathan C Kuhn, Nicholas M Kanaan, Caryl E Sortwell, Joseph R Patterson, Matthew J Benskey.

Parkinson's disease (PD) is characterized by progressive degeneration of nigrostriatal dopamine neurons and synucleinopathy, which is the accumulation of aggregated α-synuclein (α-syn). Increasing evidence implicates α-syn-associated neuroinflammation as a contributor to PD pathogenesis; however, immune mechanisms linking synucleinopathy to neurodegeneration remain incompletely defined. Activation of the complement cascade occurs in PD and other neurodegenerative disorders, but most studies report complement activation after overt neurodegeneration, making it difficult to conclude if complement is directly activated by pathological α-syn or secondarily following neurodegeneration. We used the rat α-syn preformed fibril (PFF) mode, in vitro complement assays and human postmortem PD tissue to test whether pathological α-syn directly activates complement prior to overt neurodegeneration. The α-syn PFF model exhibits a protracted pathological time course and distinct temporal separation between peak α-syn aggregation and nigrostriatal degeneration; thus we quantified complement expression, activation, and regulation during the aggregation phase. Synucleinopathy induced complement activation prior to nigrostriatal degeneration, including upregulation of components of both the classical ( C1qa, C1r, C4b ) and alternative ( Cfd, Cfb ) pathways, the anaphylatoxin ( C3aR, C5aR ) and phagocytic ( CR3 ) complement receptors, and activation of complement C3. During early synucleinopathy, microglia upregulated C3 which significantly correlated with synucleinopathy burden across several brain regions, including the substantia nigra pars compacta (SNc) and cortex. Concurrently, complement regulatory proteins, including CD55, CD59, neuronal pentraxin-1 (Nptx1), and the neuronal pentraxin receptor were downregulated in the synucleinopathy-affected SNc. Importantly, increased levels of C1q and iC3b along with downregulation of CD55 and NPTX1 were also observed in human postmortem PD SNc, supporting the translational relevance of our findings. Mechanistically, we demonstrate that aggregated, but not monomeric, α-syn directly binds C1q and activates the complement cascade in a C1q-dpendent manner. These data provide the first in vivo evidence that synucleinopathy triggers complement activation and dysregulation prior to neurodegeneration.

DOI: https://doi.org/10.64898/2026.04.27.720696
Res Sq. 2026 Apr 23. pii: rs.3.rs-9217102. [Epub ahead of print]

Cysteines are critical determinants of spontaneous and seeded tau aggregation in cells.

Lukasz Joachimiak, Parvathy Jayan, Simran Rastogi, Vaibhav Bommareddy, Chad Dashnaw, Jaime Iii Vaquer-Alicea, Binh An Nguyen, Lorena Saelices Gomez, Sarah Shahmoradian, Charles White, Marc Diamond.

The frontotemporal dementia-linked S320F mutation in the microtubule-associated protein tau promotes spontaneous aggregation, yet the structural basis of its amyloidogenesis remains unclear. Using cryo-electron microscopy, we determined the structure of an S320F 295-330 tau fibril composed of parallel chains stabilized by the 306 VQIVYK 311 amyloid motif, with S320F buried in the fibril core and a C322-C322 disulfide linking two protofilaments. Although cysteines are dispensable for fibril formation by isolated peptide fragments in vitro, tau repeat domain constructs containing both C291 and C322 generate more potent seeds in cellular assays. In contrast, the C322S mutation suppresses spontaneous aggregation of S320F tau in cells, and combined C291S and C322S mutations inhibit seeded aggregation in both wild-type and S320F contexts. Systematic alanine mutagenesis coupled with seeding by tauopathy-derived material identifies cysteine residues as critical determinants of tau seeding, comparable in importance to core amyloid motifs. Together, these findings establish cysteines as central chemical regulators of tau aggregation and propagation.

DOI: https://doi.org/10.21203/rs.3.rs-9217102/v1
J Biol Chem. 2026 May 06. pii: S0021-9258(26)02000-4. [Epub ahead of print] 113128

The Role of Phospho-ubiquitin in Mitochondrial Health and Diseases.

Kumar Suresh, Christopher Rainvillee, David E Sterner, Matthew S Goldberg, Tauseef R Butt.

  Mitochondria play a major role in cellular health, yet their contribution to chronic diseases has been underestimated. Mitochondria are essential for all tissues, and a major source of ATP in high-energy-demand organs such as brain and heart being vulnerable to mitochondrial dysfunction. Failure to repair or remove damaged mitochondria contributes to aging and chronic diseases. Cells have evolved quality control mechanisms, including mitophagy to eliminate damaged mitochondria and mitobiogenesis to replenish them. The ubiquitin-proteasome system (UPS) is responsible for removing misfolded proteins, a process that is highly ATP dependent and therefore reliant on mitochondrial function. In turn, damaged mitochondria are eliminated through coordinated actions of the UPS and lysosomal degradation through mitophagy. Many neurodegenerative diseases are characterized by the presence of disease-specific protein aggregates, such as α-synuclein aggregates in Parkinson's disease and tau neurofibrillary tangles in Alzheimer's disease. These aggregates impair mitochondrial function, while dysfunctional mitochondria generate reactive oxygen species that further exacerbate proteotoxic stress, creating a pathogenic cycle. This highlights the functional interplay between mitochondria and the UPS. Recent studies have uncovered phosphorylation of ubiquitin at Serine 65 by the mitochondrial kinase PINK1 as a key signal of mitochondrial dysfunction. Phospho-Ser65-Ubiquitin (pUb) has emerged as an indicator of mitochondrial health and a potential biomarker for aging and neurodegenerative disease. However, due largely to a lack of tools, little is known about the role of pUb in cellular physiology. Here we review the current landscape of pUb biology, the phospho-ubiquitome, and its role as biomarker for mitochondrial health, and neurodegeneration.

Keywords:  (10): mitochondria; PINK1; Parkin; aging; autophagy; biomarker; mitophagy; neurodegeneration; phospho-ubiquitin; proteasome

DOI:  https://doi.org/10.1016/j.jbc.2026.113128