bims-proned 2024-12-22 papers

bims-proned

Biomed News

on Proteostasis in neurodegeneration

Issue of 2024–12–22
sixteen papers selected by
Verena Kohler, Umeå University

Rapamycin Abrogates Aggregation of Human α-Synuclein Expressed in Fission Yeast via an Autophagy-Independent Mechanism.
Elucidation of cytotoxicity of α-Synuclein fibrils on immune cells.
Structures of Oligomeric States of Tau Protein, Amyloid-β, α-Synuclein and Prion Protein Implicated in Alzheimer's Disease, Parkinson's Disease and Prionopathies.
Detecting the Undetectable: Advances in Methods for Identifying Small Tau Aggregates in Neurodegenerative Diseases.
Targeting Tau in Alzheimer's and Beyond: Insights into Pathology and Therapeutic Strategies.
Mitochondria-targeted oligomeric α-synuclein induces TOM40 degradation and mitochondrial dysfunction in Parkinson's disease and parkinsonism-dementia of Guam.
GSK3β phosphorylation catalyzes the aggregation of tau into Alzheimer's disease-like filaments.
A model of inborn metabolism errors associated with adenine amyloid-like fiber formation reduces TDP-43 aggregation and toxicity in yeast.
An integrated machine learning approach delineates an entropic expansion mechanism for the binding of a small molecule to α-synuclein.
Salvianolic acid B prevents the amyloid transformation of A53T mutant of α-synuclein.
Examining the potential involvement of NONO in TDP-43 proteinopathy in Drosophila.
The Detection of Toxic Amyloid-β Fibril Fragments Through a Surface Plasmon Resonance Immunoassay.
Inhibitory Effects of Gliadin Hydrolysates on BACE1 Expression and APP Processing to Prevent Aβ Aggregation.
Autophagy and Protein Quality Control in Parkinson's Disease.
Modulating Amyloid-β Toxicity: In Vitro Analysis of Aβ42(G37V) Variant Impact on Aβ42 Aggregation and Cytotoxicity.
Multi-Site Red-Edge Excitation Shift Reveals the Residue-Specific Solvation Dynamics during the Native to Amyloid-like Transition of an Amyloidogenic Protein.

Genes Cells. 2025 Jan;30(1): e13185

Rapamycin Abrogates Aggregation of Human α-Synuclein Expressed in Fission Yeast via an Autophagy-Independent Mechanism.

Yoshitaka Sugimoto, Teruaki Takasaki, Ryuga Yamada, Ryo Kurosaki, Tomonari Yamane, Reiko Sugiura.

  Aggregation of alpha-synuclein (α-Syn) is implicated in the pathogenesis of several neurodegenerative disorders, such as Parkinson's disease and Dementia with Lewy bodies, collectively termed synucleinopathies. Thus, tremendous efforts are being made to develop strategies to prevent or inhibit α-Syn aggregation. Here, we genetically engineered fission yeast to express human α-Syn C-terminally fused to green fluorescent protein (GFP) at low and high levels. α-Syn was localized at the cell tips and septa at low-level expression. At high-level expression, α-Syn was observed to form cytoplasmic aggregates. Notably, rapamycin, a natural product that allosterically inhibits the mammalian target of rapamycin (mTOR) by forming a complex with FKBP12, and Torin1, a synthetic mTOR inhibitor that blocks ATP binding to mTOR, markedly reduced the number of cells harboring α-Syn aggregates. These mTOR inhibitors abrogate α-Syn aggregation without affecting α-Syn expression levels. Rapamycin, but not Torin1, failed to reduce α-Syn aggregation in the deletion cells of fkh1+, encoding FKBP12, indicating the requirement of FKBP12 for rapamycin-mediated inhibition of α-Syn aggregation. Importantly, the effect of rapamycin was also observed in the cells lacking atg1+, a key regulator of autophagy. Collectively, rapamycin abrogates human α-Syn aggregation expressed in fission yeast via an autophagy-independent mechanism mediated by FKBP12.

Keywords:  FKBP12; Parkinson's disease; fission yeast; mTOR; rapamycin; α‐Synuclein

DOI:  https://doi.org/10.1111/gtc.13185
Biochim Biophys Acta Proteins Proteom. 2024 Dec 16. pii: S1570-9639(24)00068-2. [Epub ahead of print] 141061

Elucidation of cytotoxicity of α-Synuclein fibrils on immune cells.

Mikhail Matveyenka, Abid Ali, Charles L Mitchell, Mikhail Sholukh, Dmitry Kurouski.

  Progressive aggregation of α-synuclein (α-Syn), a small cytosolic protein involved in cell vesicle trafficking, in the midbrain, hypothalamus, and thalamus is linked to Parkinson's disease (PD). Amyloid oligomers and fibrils formed as a result of such aggregation are highly toxic to neurons. However, it remains unclear whether amyloid-induced toxicity of neurons is the primary mechanism of the progressive neurodegeneration observed upon PD. In the current study, we investigated cytotoxicity exerted by α-Syn fibrils formed in the lipid-free environment, as well as in the presence of two phospholipids, on macrophages, dendritic cells, and microglia. We found that α-Syn fibrils are far more toxic to dendritic cells and microglia compared to neurons. We also observe low toxicity levels of such amyloids to macrophages. Real-time polymerase chain reaction (RT-PCR) results suggest that toxicity of amyloids aggregates is linked to the levels of autophagy in cells. These results suggest that a strong impairment of the immune system in the brain may be the first stop of neurodegenerative processes that are taking place upon the onset of PD.

Keywords:  Dendritic cells; Macrophages; Microglia; Neurons; Phospholipids; α-Synuclein

DOI:  https://doi.org/10.1016/j.bbapap.2024.141061
Int J Mol Sci. 2024 Dec 04. pii: 13049. [Epub ahead of print]25(23):

Structures of Oligomeric States of Tau Protein, Amyloid-β, α-Synuclein and Prion Protein Implicated in Alzheimer's Disease, Parkinson's Disease and Prionopathies.

Ondrej Cehlar, Stefana Njemoga, Marian Horvath, Erik Cizmazia, Zuzana Bednarikova, Exequiel E Barrera.

  In this review, we focus on the biophysical and structural aspects of the oligomeric states of physiologically intrinsically disordered proteins and peptides tau, amyloid-β and α-synuclein and partly disordered prion protein and their isolations from animal models and human brains. These protein states may be the most toxic agents in the pathogenesis of Alzheimer's and Parkinson's disease. It was shown that oligomers are important players in the aggregation cascade of these proteins. The structural information about these structural states has been provided by methods such as solution and solid-state NMR, cryo-EM, crosslinking mass spectrometry, AFM, TEM, etc., as well as from hybrid structural biology approaches combining experiments with computational modelling and simulations. The reliable structural models of these protein states may provide valuable information for future drug design and therapies.

Keywords:  amyloid-β; neurodegenerative diseases; oligomer; prion protein; tau protein; α-synuclein

DOI:  https://doi.org/10.3390/ijms252313049
Chembiochem. 2024 Dec 17. e202400877

Detecting the Undetectable: Advances in Methods for Identifying Small Tau Aggregates in Neurodegenerative Diseases.

David Klenerman, Dorothea Böken, Yunzhao Wu, Ziwei Zhang.

  Tau, a microtubule-associated protein, plays a critical role in maintaining neuronal structure and function. However, in neurodegenerative diseases such as Alzheimer's disease and other tauopathies, tau misfolds and aggregates into oligomers and fibrils, leading to neuronal damage. Soluble tau oligomers are increasingly recognised as the most neurotoxic species, inducing synaptic dysfunction and contributing to disease progression. Detecting these early-stage aggregates is challenging due to their low concentration and heterogeneity in biological samples. Traditional methods such as immunostaining and ELISA lack the sensitivity and specificity to reliably detect small tau aggregates. Advanced single-molecule approaches, including smFRET and SiMPull, offer improved sensitivity for studying tau aggregation at the molecular level. These emerging tools provide critical insights into tau pathology, enabling earlier detection and characterisation of disease-relevant aggregates, thereby offering potential for the development of targeted therapies and diagnostic approaches for tauopathies.

Keywords:  Tau; neurodegenerative disease; protein aggregation; single molecule fluorescence

DOI:  https://doi.org/10.1002/cbic.202400877
Ageing Res Rev. 2024 Dec 12. pii: S1568-1637(24)00457-4. [Epub ahead of print] 102639

Targeting Tau in Alzheimer's and Beyond: Insights into Pathology and Therapeutic Strategies.

Sunidhi Singh, Sumaiya Khan, Mohammad Shahid, Meryam Sardar, Md Imtaiyaz Hassan, Asimul Islam.

  Tauopathies encompass a group of approximately 20 neurodegenerative diseases characterized by the accumulation of the microtubule-associated protein tau in brain neurons. The pathogenesis of intracellular neurofibrillary tangles, a hallmark of tauopathies, is initiated by hyperphosphorylated tau protein isoforms that cause neuronal death and lead to diseases like Alzheimer's, Parkinson's disease, frontotemporal dementia, and other complex neurodegenerative diseases. Current applications of tau biomarkers, including imaging, cerebrospinal fluid, and blood-based assays, assist in the evaluation and diagnosis of tauopathies. Emerging research is uncovering various potential strategies to prevent cellular toxicity caused by tau aggregation: 1) suppressing toxic tau aggregation, 2) preventing post-translational modifications of tau, 3) stabilizing microtubules and 4) designing tau-directed immunogens. This review aims to discuss the role of tau in tauopathies along with neuropathological features of the different tauopathies and the new developments in treating tau aggregation with the therapeutics for treating and possibly preventing tauopathies.

Keywords:  Alzheimer's disease; Tau aggregation; hyperphosphorylation; microtubule dynamics; neurodegenerative complexities

DOI:  https://doi.org/10.1016/j.arr.2024.102639
Cell Death Dis. 2024 Dec 18. 15(12): 914

Mitochondria-targeted oligomeric α-synuclein induces TOM40 degradation and mitochondrial dysfunction in Parkinson's disease and parkinsonism-dementia of Guam.

Velmarini Vasquez, Manohar Kodavati, Joy Mitra, Indira Vedula, Dale J Hamilton, Ralph M Garruto, K S Rao, Muralidhar L Hegde.

Mitochondrial dysfunction is a central aspect of Parkinson's disease (PD) pathology, yet the underlying mechanisms are not fully understood. This study investigates the link between α-Synuclein (α-Syn) pathology and the loss of translocase of the outer mitochondrial membrane 40 (TOM40), unraveling its implications for mitochondrial dysfunctions in neurons. We discovered that TOM40 protein depletion occurs in the brains of patients with Guam Parkinsonism-Dementia (Guam PD) and cultured neurons expressing α-Syn proteinopathy, notably, without corresponding changes in TOM40 mRNA levels. Cultured neurons expressing α-Syn mutants, with or without a mitochondria-targeting signal (MTS) underscores the role of α-Syn's mitochondrial localization in inducing TOM40 degradation. PDe-related etiological factors, such as 6-hydroxydopamine or ROS/metal ions stress, which promotes α-Syn oligomerization, exacerbate TOM40 depletion in PD patient-derived cells with SNCA gene triplication. Although α-Syn interacts with both TOM40 and TOM20 in the outer mitochondrial membrane, degradation is selective for TOM40, which occurs via the ubiquitin-proteasome system (UPS) pathway. Our comprehensive analyses using Seahorse technology, mitochondrial DNA sequencing, and damage assessments, demonstrate that mutant α-Syn-induced TOM40 loss results in mitochondrial dysfunction, characterized by reduced membrane potential, accumulation of mtDNA damage, deletion/insertion mutations, and altered oxygen consumption rates. Notably, ectopic supplementation of TOM40 or reducing pathological forms of α-Syn using ADP-ribosylation inhibitors ameliorate these mitochondrial defects, suggesting potential therapeutic avenues. In conclusion, our findings provide crucial mechanistic insights into how α-Syn accumulation leads to TOM40 degradation and mitochondrial dysfunction, offering insights for targeted interventions to alleviate mitochondrial defects in PD.

DOI: https://doi.org/10.1038/s41419-024-07258-5
Proc Natl Acad Sci U S A. 2024 Dec 24. 121(52): e2414176121

GSK3β phosphorylation catalyzes the aggregation of tau into Alzheimer's disease-like filaments.

Pijush Chakraborty, Alain Ibáñez de Opakua, Jeffrey A Purslow, Simon A Fromm, Debdeep Chatterjee, Milan Zachrdla, Shannon Zhuang, Sambhavi Puri, Benjamin Wolozin, Markus Zweckstetter.

  The pathological deposition of proteins is a hallmark of several devastating neurodegenerative diseases. These pathological deposits comprise aggregates of proteins that adopt distinct structures named strains. However, the molecular factors responsible for the formation of distinct aggregate strains are unknown. Here, we show that the serine/threonine kinase GSK3β catalyzes the aggregation of the protein tau into Alzheimer's disease (AD)-like filaments. We demonstrate that phosphorylation by GSK3β, but not by several other kinases, promotes the aggregation of full-length tau as well as enhances phase separation into gel-like condensate structures. Cryoelectron microscopy further reveals that the fibrils formed by GSK3β-phosphorylated tau adopt a fold comparable to that of paired helical filaments isolated from the brains of AD patients. Our results elucidate the intricate relationship between posttranslational modification and the formation of tau strains in neurodegenerative diseases.

Keywords:  Alzheimer's disease; NMR; cryo-EM; phosphorylation; tau

DOI:  https://doi.org/10.1073/pnas.2414176121
bioRxiv. 2024 Dec 07. pii: 2024.12.03.626668. [Epub ahead of print]

A model of inborn metabolism errors associated with adenine amyloid-like fiber formation reduces TDP-43 aggregation and toxicity in yeast.

Sangeun Park, Sei-Kyoung Park, Susan W Liebman.

TDP-43 is linked to human diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal degeneration (FTD). Expression of TDP-43 in yeast is known to be toxic, cause cells to elongate, form liquid-like aggregates, and inhibit autophagy and TOROID formation. Here, we used the apt1Δ aah1Δ yeast model of disorders of inborn errors of metabolism, previously shown to lead to intracellular adenine accumulation and adenine amyloid-like fiber formation, to explore interactions with TDP-43. Results show that the double deletion shifts the TDP-43 aggregates from a liquid-like, toward a more amyloid-like, state. At the same time the deletions reduce TDP-43's effects on toxicity, cell morphology, autophagy, and TOROID formation without affecting the level of TDP-43. This suggests that the liquid-like and not amyloid-like TDP-43 aggregates are responsible for the deleterious effects in yeast. How the apt1Δ aah1Δ deletions alter TDP-43 aggregate formation is not clear. Possibly, it results from adenine/TDP-43 fiber interactions as seen for other heterologous fibers. The work offers new insights into the potential interactions between metabolite-based amyloids and pathological protein aggregates, with broad implications for understanding protein misfolding diseases.

DOI: https://doi.org/10.1101/2024.12.03.626668
Elife. 2024 Dec 18. pii: RP97709. [Epub ahead of print]13

An integrated machine learning approach delineates an entropic expansion mechanism for the binding of a small molecule to α-synuclein.

Sneha Menon, Subinoy Adhikari, Jagannath Mondal.

  The mis-folding and aggregation of intrinsically disordered proteins (IDPs) such as α-synuclein (αS) underlie the pathogenesis of various neurodegenerative disorders. However, targeting αS with small molecules faces challenges due to the lack of defined ligand-binding pockets in its disordered structure. Here, we implement a deep artificial neural network-based machine learning approach, which is able to statistically distinguish the fuzzy ensemble of conformational substates of αS in neat water from those in aqueous fasudil (small molecule of interest) solution. In particular, the presence of fasudil in the solvent either modulates pre-existing states of αS or gives rise to new conformational states of αS, akin to an ensemble-expansion mechanism. The ensembles display strong conformation-dependence in residue-wise interaction with the small molecule. A thermodynamic analysis indicates that small-molecule modulates the structural repertoire of αS by tuning protein backbone entropy, however entropy of the water remains unperturbed. Together, this study sheds light on the intricate interplay between small molecules and IDPs, offering insights into entropic modulation and ensemble expansion as key biophysical mechanisms driving potential therapeutics.

Keywords:  alpha synuclein; machine learning; molecular biophysics; none; small molecule; structural biology

DOI:  https://doi.org/10.7554/eLife.97709
Biophys Chem. 2024 Dec 13. pii: S0301-4622(24)00208-4. [Epub ahead of print]318 107379

Salvianolic acid B prevents the amyloid transformation of A53T mutant of α-synuclein.

Almas Akhtar, Payal Singh, Nikita Admane, Abhinav Grover.

  Parkinson's disease (PD) is a neurodegenerative disorder involving the progressive loss of dopaminergic neurons in the substantia nigra pars compacta triggered by the accumulation of amyloid aggregates of α-synuclein protein. This study investigates the potential of Salvianolic Acid B (SalB), a water-soluble polyphenol derived from Salvia miltiorrhiza Bunge, in modulating the aggregation of the A53T mutant of α-synuclein (A53T Syn). This mutation is associated with rapid aggregation and a higher rate of protofibril formation in early-onset familial PD. Computational and experimental approaches demonstrated Sal-B effectively prevents the amyloid fibrillation of A53T Syn by interacting with the N-terminal region and NAC domain. Sal-B particularly associates with the KTKEGV motif and NACore segment of A53T Syn by hydrophobic and hydrogen bonding interactions. Replica exchange molecular dynamics (REMD) simulations indicated that Sal-B reduces intramolecular hydrogen bonding and structural transitions into β-sheet rich conformations, thereby lowering the aggregation propensity of A53T Syn. Systematic analysis conducted using biophysical techniques and high-end microscopy has demonstrated significant inhibition in the amyloid transformation of A53T Syn corroborated by a 92 % decrease in ThT maxima at 100 μM Sal-B concentration and microscopic techniques validated the absence of mature fibrillar amyloids. DLS data revealed heterogeneous particle sizes, supporting the formation of smaller unstructured aggregates. These findings underscore Sal-B as a promising therapeutic candidate for PD and related synucleinopathies, warranting further investigation in cellular and animal models to advance potential treatments and early intervention strategies.

Keywords:  A53T Syn; Amyloid aggregation; Neurodegeneration; Parkinson's disease (PD); Salvianolic acid B; α-Synuclein

DOI:  https://doi.org/10.1016/j.bpc.2024.107379
Eur J Neurosci. 2024 Dec 17.

Examining the potential involvement of NONO in TDP-43 proteinopathy in Drosophila.

Rafael Koch, Emi Nagoshi.

  The misfolding and aggregation of TAR DNA binding protein-43 (TDP-43), leading to the formation of cytoplasmic inclusions, emerge as a key pathological feature in a spectrum of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar dementia (FTLD). TDP-43 shuttles between the nucleus and cytoplasm but forms nuclear bodies (NBs) in response to stress. These NBs partially colocalise with nuclear speckles and paraspeckles that sequester RNAs and proteins, thereby regulating many cellular functions. The laboratory of Steven Brown has recently found that the non-POU domain-containing octamer-binding protein (NONO), a component of paraspeckles, forms novel nuclear speckle-like structures in mouse cortical neurons in response to stress and sleep deprivation. These findings suggest the possibility of a functional link between NONO and TDP-43, potentially contributing to TDP-43 proteinopathy. Here, we demonstrate that pathological phenotypes caused by TDP-43 gain of function-locomotor defects and life span shortening-are exacerbated by silencing the Drosophila homolog of NONO, no on or off transient A (NonA). Additionally, NonA silencing results in an increase in nuclear TDP-43 NBs. These results provide supporting evidence for the functional link between NONO and TDP-43 and lay the foundation for dissecting underlying mechanisms.

Keywords:  lifespan; locomotor deficits; neurodegenerative disorders; nuclear bodies

DOI:  https://doi.org/10.1111/ejn.16632
Int J Mol Sci. 2024 Dec 04. pii: 13020. [Epub ahead of print]25(23):

The Detection of Toxic Amyloid-β Fibril Fragments Through a Surface Plasmon Resonance Immunoassay.

Marten Beeg, Beatrice Rocutto, Elisabetta Battocchio, Letizia Dacomo, Alessandro Corbelli, Fabio Fiordaliso, Claudia Balducci, Marco Gobbi.

  Amyloid-β1-42 (Aβ42) forms highly stable and insoluble fibrillar structures, representing the principal components of the amyloid plaques present in the brain of Alzheimer's disease (AD) patients. The involvement of Aβ42 in AD-associated neurodegeneration has also been demonstrated, in particular for smaller and soluble aggregates (oligomers). Based on these findings and on genetic evidence, Aβ42 aggregates are considered key players in the pathogenesis of AD and targets for novel therapies. Different approaches are currently used to detect the various aggregation states of Aβ peptide, including spectrophotometric methods, imaging techniques, and immunoassays, but all of these have specific limitations. To overcome them, we have recently exploited the peculiar properties of surface plasmon resonance (SPR) to develop an immunoassay capable of selectively detecting monomers and oligomers, discriminating them also from bigger fibrils in a mixture of different aggregated species, without any manipulation of the solution. In the present study, we extended these previous studies, showing that the SPR-based immunoassay makes it possible to unveil the fibril fragmentation induced mechanically, a result difficult to be conveniently and reliably assessed with other approaches. Moreover, we show that SPR-recognized fibril fragments are more toxic than the larger fibrillar structures, suggesting the relevance of the proposed SPR-based immunoassay.

Keywords:  Alzheimer’s disease (AD); Amyloid-β (Aβ); Aβ fibril fragmentation; immunoassay; neurotoxicity; surface plasmon resonance (SPR)

DOI:  https://doi.org/10.3390/ijms252313020
Int J Mol Sci. 2024 Dec 09. pii: 13212. [Epub ahead of print]25(23):

Inhibitory Effects of Gliadin Hydrolysates on BACE1 Expression and APP Processing to Prevent Aβ Aggregation.

Chin-Yu Lin, Cheng-Hong Hsieh, Pei-Yu Lai, Ching-Wei Huang, Yung-Hui Chung, Shang-Ming Huang, Kuo-Chiang Hsu.

  Alzheimer's disease (AD), a leading neurodegenerative disorder, is closely associated with the accumulation of amyloid-beta (Aβ) peptides in the brain. The enzyme β-secretase (BACE1), pivotal in Aβ production, represents a promising therapeutic target for AD. While bioactive peptides derived from food protein hydrolysates have neuroprotective properties, their inhibitory effects on BACE1 remain largely unexplored. In this study, we evaluated the inhibitory potential of protein hydrolysates from gliadin, whey, and casein proteins prepared using bromelain, papain, and thermolysin. Through in vitro and cellular assays, bromelain-hydrolyzed gliadin (G-Bro) emerged as the most potent BACE1 inhibitor, with an IC50 of 0.408 mg/mL. G-Bro significantly reduced BACE1 expression and amyloid precursor protein (APP) processing in N2a/PS/APP cell cultures, suggesting its potential to attenuate Aβ aggregation. The unique peptide profile of G-Bro likely contributes to its inhibitory effect, with proline residues disrupting β-sheets, lysine residues introducing positive charges that hinder aggregation, hydrophobic residues stabilizing binding interactions, and glutamine residues enhancing solubility and stability. These findings highlight gliadin hydrolysates, particularly G-Bro, as potential natural BACE1 inhibitors with applications in dietary interventions for AD prevention. However, further studies are warranted to elucidate specific peptide interactions and their bioactivity in neural pathways to better understand their therapeutic potential.

Keywords:  Alzheimer’s disease; BACE1; amyloid beta; gliadin; peptide

DOI:  https://doi.org/10.3390/ijms252313212
Cold Spring Harb Perspect Med. 2024 Dec 18. pii: a041619. [Epub ahead of print]

Autophagy and Protein Quality Control in Parkinson's Disease.

Marta Martinez-Vicente, Miquel Vila.

Autophagy is a vital cellular process responsible for the degradation of proteins, organelles, and other cellular components within lysosomes. In neurons, basal autophagy is indispensable for maintaining cellular homeostasis and protein quality control. Accordingly, lysosomal dysfunction has been proposed to be associated with neurodegeneration, and with Parkinson's disease (PD) in particular. Aging, dopamine metabolism, and PD-linked genetic mutations are thought to impair the autophagic-lysosomal pathway, disrupt cellular proteostasis, and contribute to PD pathogenesis. These alterations represent an opportunity to identify potential new therapeutic targets and disease biomarkers, thus laying the groundwork for the development of novel disease-modifying strategies for PD that are aimed at restoring cellular proteostasis and quality control systems.

DOI: https://doi.org/10.1101/cshperspect.a041619
Int J Mol Sci. 2024 Dec 09. pii: 13219. [Epub ahead of print]25(23):

Modulating Amyloid-β Toxicity: In Vitro Analysis of Aβ42(G37V) Variant Impact on Aβ42 Aggregation and Cytotoxicity.

Shu-Hsiang Huang, Shang-Ting Fang, Chin-Hao Yang, Je-Wen Liou, Yi-Cheng Chen.

  Alzheimer's disease (AD) is primarily driven by the formation of toxic amyloid-β (Aβ) aggregates, with Aβ42 being a pivotal contributor to disease pathology. This study investigates a novel agent to mitigate Aβ42-induced toxicity by co-assembling Aβ42 with its G37V variant (Aβ42(G37V)), where Gly at position 37 is substituted with valine. Using a combination of Thioflavin-T (Th-T) fluorescence assays, Western blot analysis, atomic force microscopy (AFM)/transmission electron microscopy (TEM), and biochemical assays, we demonstrated that adding Aβ42(G37V) significantly accelerates Aβ42 aggregation rate and mass while altering the morphology of the resulting aggregates. Consequently, adding Aβ42(G37V) reduces the Aβ42 aggregates-induced cytotoxicity, as evidenced by improved cell viability assays. The possible mechanism for this effect is that adding Aβ42(G37V) reduces the production of reactive oxygen species (ROS) and lipid peroxidation, typically elevated in response to Aβ42, indicating its protective effects against oxidative stress. These findings suggest that Aβ42(G37V) could be a promising candidate for modulating Aβ42 aggregation dynamics and reducing its neurotoxic effects, providing a new avenue for potential therapeutic interventions in AD.

Keywords:  Aβ42; Aβ42(G37V); aggregation; glycine-zipper motif; morphology; toxicity

DOI:  https://doi.org/10.3390/ijms252313219
J Phys Chem B. 2024 Dec 16.

Multi-Site Red-Edge Excitation Shift Reveals the Residue-Specific Solvation Dynamics during the Native to Amyloid-like Transition of an Amyloidogenic Protein.

Sonal R More, Santosh Kumar Jha.

Changes in water-protein interactions are crucial for proteins to achieve functional and nonfunctional conformations during structural transitions by modulating local stability. Amyloid-like protein aggregates in deteriorating neurons are hallmarks of neurodegenerative disorders. These aggregates form through significant structural changes, transitioning from functional native conformations to supramolecular cross-β-sheet structures via misfolded and oligomeric intermediates in a multistep process. However, the site-specific dynamics of water molecules from the native to misfolded conformations and further to oligomeric and compact amyloid structures remain poorly understood. In this study, we used the fluorescence method known as red-edge excitation shift (REES) to investigate the solvation dynamics at specific sites in various equilibrium conformations en route to the misfolding and aggregation of the functional domain of the TDP-43 protein (TDP-43tRRM). We generated three single tryptophan-single cysteine mutants of TDP-43tRRM, with the cysteines at different positions and tryptophan at a fixed position. Each sole cysteine was fluorescently labeled and used as a site-specific fluorophore along with the single tryptophan, creating four monitorable sites for REES studies. By investigating the site-specific extent of REES, we developed a residue-specific solvation dynamics map of TDP-43tRRM during its misfolding and aggregation. Our observations revealed that solvation dynamics progressively became more rigid and heterogeneous to varying extents at different sites during the transition from native to amyloid-like conformations.

DOI: https://doi.org/10.1021/acs.jpcb.4c07067