bims-proned 2025-01-05 papers

bims-proned

Biomed News

on Proteostasis in neurodegeneration

Issue of 2025–01–05
sixteen papers selected by
Verena Kohler, Umeå University

Autophagy receptor-inspired chimeras: a novel approach to facilitate the removal of protein aggregates and organelle by autophagy degradation.
Advances in Aggrephagy: Mechanisms, Disease Implications, and Therapeutic Strategies.
Basic Science and Pathogenesis.
Basic Science and Pathogenesis.
Basic Science and Pathogenesis.
Microcystin-LR Exposure Damages Neurons by Inducing α-Syn Aggregation via MAPK4/GATA2/SNCA and PP2A/GRKs Pathways.
Basic Science and Pathogenesis.
Basic Science and Pathogenesis.
Basic Science and Pathogenesis.
Decoding TDP-43: the molecular chameleon of neurodegenerative diseases.
Basic Science and Pathogenesis.
Topological confinement by a membrane anchor suppresses phase separation into protein aggregates: Implications for prion diseases.
Increased α-synuclein phosphorylation and oligomerization and altered enzymes in plasma of patients with Parkinson's disease.
NLS-binding deficient Kapβ2 reduces neurotoxicity via selective interaction with C9orf72-ALS/FTD dipeptide repeats.
Localized molecular chaperone synthesis maintains neuronal dendrite proteostasis.
Distinct regulation of Tau Monomer and aggregate uptake and intracellular accumulation in human neurons.

J Zhejiang Univ Sci B. 2024 Sep 25. pii: 1673-1581(2024)12-1115-05. [Epub ahead of print]25(12): 1115-1119

Autophagy receptor-inspired chimeras: a novel approach to facilitate the removal of protein aggregates and organelle by autophagy degradation.

Liwen Wang, Huimei Liu, Lanfang Li.

  Neurodegenerative diseases (NDDs), mainly including Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), and Alzheimer's disease (AD), are sporadic and rare genetic disorders of the central nervous system. A key feature of these conditions is the slow accumulation of misfolded protein deposits in brain neurons, the excessive aggregation of which leads to neurotoxicity and further disorders of the nervous system.

Keywords:  Autophagy; Organelle; Protein aggregates; Synthetic autophagy receptors; p62

DOI:  https://doi.org/10.1631/jzus.B2300853
J Cell Physiol. 2025 Jan;240(1): e31512

Advances in Aggrephagy: Mechanisms, Disease Implications, and Therapeutic Strategies.

Haixia Zhuang, Xinyu Ma.

  The accumulation of misfolded proteins within cells leads to the formation of protein aggregates that disrupt normal cellular functions and contribute to a range of human pathologies, notably neurodegenerative disorders. Consequently, the investigation into the mechanisms of aggregate formation and their subsequent clearance is of considerable importance for the development of therapeutic strategies. The clearance of protein aggregates is predominantly achieved via the autophagy-lysosomal pathway, a process known as aggrephagy. In this pathway, autophagosome biogenesis and lysosomal digestion provide necessary conditions for the clearance of protein aggregates, while autophagy receptors such as P62, NBR1, TAX1BP1, TOLLIP, and CCT2 facilitate the recognition of protein aggregates by the autophagy machinery, playing a pivotal role in their degradation. This review will introduce the mechanisms of aggregate formation, progression, and degradation, with particular emphasis on advances in aggrephagy, providing insights for aggregates-related diseases and the development of novel therapeutic strategies.

Keywords:  aggrephagy; aggrephagy receptors; autophagy; neurodegeneration; protein aggregates

DOI:  https://doi.org/10.1002/jcp.31512
Alzheimers Dement. 2024 Dec;20 Suppl 1 e093234

Basic Science and Pathogenesis.

Nemil Bhatt, Nicha Puangmalai, Cynthia Jerez, Nikita Shchankin, Rakez Kayed.

BACKGROUND: Tauopathies, including Alzheimer's Disease and Frontotemporal Dementia, are characterized as intracellular lesions composed of aggregated tau proteins. Soluble tau oligomers are shown to be one of the most toxic species and are responsible for the spread of tau pathology. Recent studies have found that several proteins such as amyloid b, a-synuclein, and TDP-43 can aggregate tau. In this study, we investigated the ability of small metabolites like C9orf72 associated dipeptide protein repeats (DPRs) to interact with and aggregate tau to form toxic soluble tau oligomers.
METHOD: We have developed various models which express dipeptide protein repeats to understand the interaction between short peptides and tau. The dipeptide protein repeat induced tau aggregates were characterized using biophysical, as well as biochemical assays in vitro and in cellular models. Furthermore, we evaluated their toxicity, and seeding potency to understand the biological effects of this interaction.
RESULT: Our results suggest the propensity for DPRs, especially glycine-arginine and proline-arginine repeats to form oligomeric structures which interact and seed tau in a prion like fashion. This leads to the production of tau oligomers causing alterations in the microtubule dynamics in cell lines as well as primary neuronal culture systems.
CONCLUSION: Many studies have investigated the toxicity of small protein repeats, however, the role of DPR oligomers in inducing tau aggregation is still unclear. Thus, the ability to understand the toxic interplay between small peptide repeats and tau oligomers has great potential to further the understanding of tau progression and aid in the development of targeted therapeutics.

DOI: https://doi.org/10.1002/alz.093234
Alzheimers Dement. 2024 Dec;20 Suppl 1 e086931

Basic Science and Pathogenesis.

Muhammad I Abeer, Michael A Gitcho.

BACKGROUND: Aggregation of transactive response DNA binding protein 43 (TDP-43) is the major pathological feature of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Recently, in up to 50% of Alzheimer's disease (AD) cases TDP-43 pathology was discovered and this pathology has been referred to as limbic-predominant age-related TDP43 encephalopathy (LATE). Several studies reported that TDP-43 binds to heat shock protein family B (small) member 1 (HSPB1 or HSP27) but no functional evaluation of this interaction has been explored. Inducing expression of HSP27 has been shown to be protective of many other disease conditions and has been shown to reduce aggregation of amyloid in AD. In general, the goal is to utilize both primary neuronal cultures and mice that are selectively expressing pathogenic TDP-43, HSP27, and apolipoprotein E (APOE) in the brain to characterize the effect of HSP27 overexpression on TDP-43 and APOE. This will give us a better model to understand TDP-43 proteinopathies. In the present study, we hypothesize that increased expression of HSP27 may reduce TDP-43 aggregation and alter mitochondrial morphology.
METHOD: A new transgenic mouse model was developed to selectively drive human HSP27 and pathological TDP-43 with a defective nuclear localization signal (DNLS) in the hippocampus and neocortex using the Ca2+/calmodulin protein kinase (Camk2a) tetracycline inducible system. The following genotypes have been evaluated for immunohistochemistry, biochemistry (solubility fractionation), and Western blot: wild-type, Camk2a/DNLS, Camk2a/HSP27 and Camk2a/HSP27/TDP43DNLS at 4 months of age.
RESULT: Preliminary in vitro results show that cells overexpressing HSP27 reduce aggregation and protein levels of TDP43. However, mice overexpressing HSP27 in a TDP43DNLS background in the hippocampus and cortex does not show any reduction in the soluble fraction. Interestingly, increased expression of HSP27 in the hippocampus of Camk2a/HSP27 mice showed a significant reduction of endogenous APOE expression. Immunohistochemical and bioenergetic experiments are currently being carried out to evaluate the brain and mitochondrial morphology upon HSP27 overexpression.
CONCLUSION: Overall, our initial data suggests that modifying HSP27 expression modulates endogenous APOE level.

DOI: https://doi.org/10.1002/alz.086931
Alzheimers Dement. 2024 Dec;20 Suppl 1 e087557

Basic Science and Pathogenesis.

Vaishnavi Jadhav, Randall Eck, Samuel Smukowski, Laura Garcia Toscano, Caitlin S Latimer, Paul N Valdmanis, Brian C Kraemer, Nicole F Liachko.

BACKGROUND: Alzheimer's disease (AD), the most common aging-associated neurodegenerative dementia disorder, is defined by the presence of amyloid beta (Aβ) and tau aggregates in the brain. However, more than half of patients also exhibit aggregates of the protein TDP-43 as a secondary pathology. Clinically, AD patients with secondary TDP-43 pathology have more severe cognitive impairment, more rapid cognitive decline, worse brain atrophy, and a shorter disease course. TDP-43 is already implicated in neurodegenerative disease as the major pathological protein aggregate in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP), two other devastating neurodegenerative diseases. In patients with mixed Aβ, tau and TDP-43 pathology, TDP-43 dysfunction may synergize with neurodegenerative processes in AD, worsening disease. Using C. elegans models of mixed pathology in AD, we have shown that TDP-43 specifically synergizes with tau but not Aβ, resulting in enhanced neuronal dysfunction, selective neurodegeneration, and increased accumulation of pathological tau.
METHOD: To identify cellular responses to mixed tau and TDP-43, we have identified distinct transcriptomic signatures from two disease-relevant timepoints preceding frank neuronal loss in C. elegans.
RESULT: We find that early disease associated changes are driven by tau, but a unique gene expression signature characteristic of co-morbid tau and TDP-43 emerges during aging. Using gene ontology and differential splicing analyses, we find significant changes in genes and pathways including lysosomal mediated degradation, lipid metabolism. We have characterized novel modifiers of tau and TDP-43 identified from their responsive gene expression profiles in tau and TDP-43 co-expressing C. elegans.
CONCLUSION: Establishing early cellular responses to co-morbid tau and TDP-43 is critical for understanding protective and pathogenic responses to mixed proteinopathies, and an important step in developing therapeutic strategies protecting against pathological tau and TDP-43 in AD.

DOI: https://doi.org/10.1002/alz.087557
Mol Neurobiol. 2024 Dec 30.

Microcystin-LR Exposure Damages Neurons by Inducing α-Syn Aggregation via MAPK4/GATA2/SNCA and PP2A/GRKs Pathways.

Minghao Yan, Huifang Wu, Tong Wu, Yuhan Wang, Chengxiang Su, Dongmei Li, Xiaodong Han.

  Microcystin-LR (MC-LR) is a natural neurotoxin with strong toxicity, and studies have demonstrated that chronic MC-LR exposure generated Parkinson-like dyskinesia in mice. Parkinson's disease (PD) is a neurologic degenerative disease mostly occurring in elderly people, and the progressive loss of dopaminergic neurons and the formation of Lewy bodies are the hallmark pathological features. The main component of Lewy bodies is α-synuclein (α-syn) encoded by the SNCA gene, and the copy number mutation of SNCA gene can promote the overexpression of α-syn. A mouse model of MC-LR exposure for 15 months was established to confirm the deposition of Lewy bodies. SH-SY5Y cells exposed to MC-LR were constructed as an in vitro model of PD, and the transcription factor that regulated the SNCA gene (the encoding gene of α-syn) was identified through the database. MC-LR enhanced the transcription level of SNCA gene and upregulated α-syn protein expression by promoting MAPK4 into the nucleus and binding to GATA2 295-480 fragment. In addition, MC-LR inhibited PP2A activity and activated GRKs kinase to promote α-syn phosphorylation at Ser129. These results suggest that MC-LR is involved in α-syn aggregate formation and PD pathogenesis by enhancing SNCA transcriptional activity to promote α-syn elevation via the MAPK4/GATA2 pathway and inducing α-syn phosphorylation via the PP2A/GRKs pathway.

Keywords:  GATA2/MAPK4/SNCA pathway; Microcystin-LR; Neuronal apoptosis; PP2A/GRKs pathway; α-Synuclein

DOI:  https://doi.org/10.1007/s12035-024-04683-7
Alzheimers Dement. 2024 Dec;20 Suppl 1 e087744

Basic Science and Pathogenesis.

David Lynch, Nemil Bhatt, Madison Samples, Madeline Demny, Phanourios Tamamis, Rakez Kayed.

BACKGROUND: The oligomers and fibrils of tau are well known as an indicator of Alzheimer's disease (AD). Recently, other protein aggregates have been shown to be potentially involved in the development of the disease. One of these proteins is p53, involved in DNA repair. Prior studies in our lab show that p53 will form oligomers and fibrils in AD cases but not healthy controls, and has even been observed as a co-aggregate with tau protein. Owing to the importance of p53 in mitigating damage from diseased cells, it is possible that loss of function or even misfunction of p53 due to aggregation or mislocalisation could be an early contributing factor to AD, having been shown as a potential early biomarker for AD. Because of the co-aggregation of p53 and tau, it is possible that aggregate-specific antibodies will bind to both p53 and tau. Besides giving mechanistic insights into the proteins' aggregation, this would also suggest that these antibodies could inhibit aggregation in vivo. This study examines this common epitope.
METHOD: • Using recombinant wild-type and mutant p53 and tau proteins, the interaction of p53 and tau specific antibodies with each other was determined based around their immunoreactivity, and compared to amyloid-β. • Co-staining of AD mouse model and AD patient samples for both misfolded tau and p53 was used to determine if this conformation cross-reactivity could also be observed in patient samples.
RESULT: Despite the lack of sequence homology, an in-house conformation and aggregation specific p53 antibody was found to be able to react with tau protein, and vice versa. It was also observed that the p53 mutant proteins had different reactions to these aggregate-specific antibodies. As these antibodies are conformation-specific, this provides information on the similar conformation both proteins must adopt in order to react with MDM2.
CONCLUSION: The common epitope recognised by the p53 and tau antibodies suggests that this is a potential target for antibody therapy, as the ability to prevent the formation of the co-aggregates may permit p53 to continue its role as the 'guardian of the genome', a role which, if inhibited, could be a contributing factor to AD.

DOI: https://doi.org/10.1002/alz.087744
Alzheimers Dement. 2024 Dec;20 Suppl 1 e090359

Basic Science and Pathogenesis.

Yixiang Jiang.

BACKGROUND: Synucleinopathies lack cures. Antibody therapies targeting α-synuclein aim to inhibit aggregation and enhance degradation, but have limited brain entry because of size (150kDa). Smaller single-domain antibodies (sdAbs, 15kDa) have substantially improved brain uptake. Previously, we developed sdAb-based probes (2D10 and 2D8) enabling specific α-synuclein imaging in mice post i.v. injection, correlating with lesion burden, indicating therapeutic and diagnostic potential (Jiang Y et al Sci Adv 2023).
METHOD: To enhance sdAbs' efficacy, we developed 2D8-PEGn-T (n = 2,4,6), linking 2D8 sdAb and thalidomide (T) with different PEG linkers to promote proteasomal degradation (sdAb-PROTAC). We assessed sdAb binding affinity to α-synuclein preparations by biolayer interferometry, examined α-synuclein degradation in M83-mouse primary culture, and evaluated therapeutic efficacy in M83-synucleinopathy mouse model (n = 17). Using 2D10 sdAb linked to a near-infrared-tag and In-Vivo-Imaging-System, we assessed brain α-synuclein burden pre-treatment. Mice with similar burden received 3 i.v. sdAb injections (molar equivalent: 100 µg of 2D8) 3 days apart, with re-imaging after 3 days, followed by brain extraction for analyses of α-synuclein clearance and potential toxicity.
RESULT: 2D8-PEGn-T's affinity after conjugation was comparable to 2D8's affinity. 2D8-PEG4-T targeted α-synuclein and Cereblon, inducing ubiquitination and proteasomal degradation. In the culture, 2D8-PEG4-T prevented α-synuclein-induced toxicity and reduced α-synuclein levels via lysosomal- and proteasomal-pathways, outperforming unmodified 2D8 sdAb that mainly cleared α-synuclein via the lysosomal-pathway. In the M83-synucleinopathy mouse model, 2D8-PEG4-T significantly (81%, p = 0.0049) reduced α-synuclein brain signal, surpassing 32% for 2D8 (p = 0.3195) vs PBS control. Western blots showed 2D8-PEG4-T to be more efficacious (89-93% reduction, p<0.0001) in reducing insoluble total and pS129 α-synuclein, compared to 2D8 (59-69% reduction, p = 0.0015 and 0.0016) vs PBS control. Additionally, 2D8-PEG4-T decreased soluble total and pS129 α-synuclein levels by 70% (p = 0.0072) and 90% (p = 0.0001), surpassing 2D8 that did not significantly reduce soluble total (p = 0.8643) or pS129 α-synuclein (reduced by 34%, p = 0.1018), compared to PBS control.
CONCLUSION: 2D8-PEG4-T enhances α-synuclein proteasomal degradation while maintaining 2D8's lysosomal clearance. Its superior α-synuclein clearance, compared to unmodified 2D8 sdAb in vitro and in vivo, highlights its therapeutic potential for synucleinopathies. Small sdAbs with improved brain entry and potency may enhance clinical benefits in antibody-based therapies.

DOI: https://doi.org/10.1002/alz.090359
Alzheimers Dement. 2024 Dec;20 Suppl 1 e092752

Basic Science and Pathogenesis.

Andre Direito Goulart Leitao, Rijwan Uddin Ahammad, Brian Spencer, Chengbiao Wu, Robert A Rissman.

BACKGROUND: Neurodegenerative disorders of aging are characterized by the progressive accumulation of proteins such as α-synuclein (α-syn) and amyloid beta (Aβ). Misfolded and aggregated α-syn has been implicated in neurological disorders such as Parkinson's disease (PD), and Dementia with Lewy Bodies (DLB), but less so in Alzheimer's Disease (AD) despite the fact that synuclein pathology is present in over 50% of postmortem brains of AD patients. We are now expanding on our previous studies which showed positive therapeutic effects of downregulating α-syn in AD mice to understand the overall brain transcriptomic and mechanistic changes induced by treatment.
METHOD: We first treated AD mice systemically with a α-syn antisense oligonucleotide (ASO-syn) conjugated with a LDLR-specific peptide (ApoB11) that allows for transport across the blood-brain barrier and measured the presence of the ASO in the brain by immunohistochemistry. We then treated both neurons in culture and 6 months-old AD mice with the ApoB:ASO conjugates and measured α-syn levels in both cells and brains by immunohistochemistry and Western blot to test the feasibility of this treatment to downregulate α-syn. Finally, we performed single-cell RNAseq to ask the question of how α-syn interferes with neuropathology in AD, i.e. which genomic pathways are changed when mice are treated with ApoB:ASO-syn conjugates.
RESULT: We found that treatment of APP transgenic (AD) mice with ApoB11:ASO-syn leads to a significant reduction of Aβ plaques burden, rescued neuronal loss and prevented astrogliosis, as compared to untreated AD mice. Importantly, we found that AD mice treated with the ASO-syn had significantly improved spatial memory function. We found specific single-cell transcriptomic changes associated with this downregulation of α-syn, highlighting possible pathways for α-syn-mediated vulnerability.
CONCLUSION: Collectively, our data supports the use of ApoB11:ASO α-syn conjugates delivered systemically to downregulate α-syn as a promising future therapeutic strategy in AD. Our work suggests that knocking down α-syn could be necessary to prevent neuropathology in AD.

DOI: https://doi.org/10.1002/alz.092752
Acta Neuropathol Commun. 2024 Dec 31. 12(1): 205

Decoding TDP-43: the molecular chameleon of neurodegenerative diseases.

Jixiang Zeng, Chunmei Luo, Yang Jiang, Tao Hu, Bixia Lin, Yuanfang Xie, Jiao Lan, Jifei Miao.

  TAR DNA-binding protein 43 (TDP-43) has emerged as a critical player in neurodegenerative disorders, with its dysfunction implicated in a wide spectrum of diseases including amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTLD), and Alzheimer's disease (AD). This comprehensive review explores the multifaceted roles of TDP-43 in both physiological and pathological contexts. We delve into TDP-43's crucial functions in RNA metabolism, including splicing regulation, mRNA stability, and miRNA biogenesis. Particular emphasis is placed on recent discoveries regarding TDP-43's involvement in DNA interactions and chromatin dynamics, highlighting its broader impact on gene expression and genome stability. The review also examines the complex pathogenesis of TDP-43-related disorders, discussing the protein's propensity for aggregation, its effects on mitochondrial function, and its non-cell autonomous impacts on glial cells. We provide an in-depth analysis of TDP-43 pathology across various neurodegenerative conditions, from well-established associations in ALS and FTLD to emerging roles in diseases such as Huntington's disease and Niemann-Pick C disease. The potential of TDP-43 as a therapeutic target is explored, with a focus on recent developments in targeting cryptic exon inclusion and other TDP-43-mediated processes. This review synthesizes current knowledge on TDP-43 biology and pathology, offering insights into the protein's central role in neurodegeneration and highlighting promising avenues for future research and therapeutic interventions.

Keywords:  RNA metabolism; TDP-43; chromatin regulation; cryptic exons; mitochondrial dysfunction; neurodegeneration; therapeutic targets

DOI:  https://doi.org/10.1186/s40478-024-01914-9
Alzheimers Dement. 2024 Dec;20 Suppl 1 e088566

Basic Science and Pathogenesis.

Laura Garcia Toscano, Joshua C Hincks, Pamela J McMillan, Misa Baum, Sarah M Waldherr, Brian C Kraemer, Nicole F Liachko.

BACKGROUND: Alzheimer's disease (AD) is the leading cause of dementia and one of the most devastating neurodegenerative diseases. In the last decades, a large proportion of AD patients have been described as having aberrant accumulation of TDP-43 protein, a well-established driver of neurodegeneration. This TDP-43 proteinopathy in AD can co-occur in neurons with the main hallmarks of the disease, toxic amyloid oligomers and neurofibrillary tangles containing hyperphosphorylated Tau, and correlates with rapid progression and worse prognosis. However, the underlying mechanisms of pathogenic TDP-43 contributing to AD and its possible involvement as a trigger of neurotoxicity remain unclear.
METHOD: We aimed to explore the role of TDP-43 in a mouse model of tau-mediated toxicity. To this end, we created a new mouse model of tau and TDP-43 co-pathology that combines the constitutive transgenic expression of wild-type human tau with adeno-associated virus (AAV) driven expression of wild-type human TDP-43. Using a stereotaxic device, we performed a unilateral intrahippocampal injection of AAV-9 carrying the human TDP-43 cDNA (or green fluorescent protein as a control) into 3-month-old transgenic mice expressing the most abundant brain isoform (1N4R) of Tau in neurons. Animals were then perfused 2, 4, and 12 weeks after injection, and brains were collected for immunohistochemistry.
RESULT: Our results showed that although TDP 43 overexpression was similar in both transgenic and control mice, the presence of hTDP-43 promoted an increase in phosphorylated tau species. These data suggest a possible interaction between human tau protein and TDP-43 proteins leading to the spread of phosphorylated Tau species, thus contributing to the pathology in our mouse model of the disease. Additionally, the co-expression of both TDP-43 and Tau proteins induced a transient inflammatory state in transgenic animals, sustained 4 weeks after injury. However, 12 weeks after injury, inflammation was resolved, and the presence of phosphorylated Tau species was significantly reduced.
CONCLUSION: This new mouse model provides a vehicle to explore causes and consequences of co-pathological tau and TDP-43. Further studies will be necessary to determine mechanisms underlying TDP-43 promotion of pathological accumulation of toxic Tau species and neuroinflammation in this experimental model of TDP-43- Tau co-expression.

DOI: https://doi.org/10.1002/alz.088566
Proc Natl Acad Sci U S A. 2025 Jan 07. 122(1): e2415250121

Topological confinement by a membrane anchor suppresses phase separation into protein aggregates: Implications for prion diseases.

Kalpshree Gogte, Fatemeh Mamashli, Maria Georgina Herrera, Simon Kriegler, Verian Bader, Janine Kamps, Prerna Grover, Roland Winter, Konstanze F Winklhofer, Jörg Tatzelt.

  Protein misfolding and aggregation are a hallmark of various neurodegenerative disorders. However, the underlying mechanisms driving protein misfolding in the cellular context are incompletely understood. Here, we show that the two-dimensional confinement imposed by a membrane anchor stabilizes the native protein conformation and suppresses liquid-liquid phase separation (LLPS) and protein aggregation. Inherited prion diseases in humans and neurodegeneration in transgenic mice are linked to the expression of anchorless prion protein (PrP), suggesting that the C-terminal glycosylphosphatidylinositol (GPI) anchor of native PrP impedes spontaneous formation of neurotoxic and infectious PrP species. Combining unique in vitro and in vivo approaches, we demonstrate that anchoring to membranes prevents LLPS and spontaneous aggregation of PrP. Upon release from the membrane, PrP undergoes a conformational transition to detergent-insoluble aggregates. Our study demonstrates an essential role of the GPI anchor in preventing spontaneous misfolding of PrPC and provides a mechanistic basis for inherited prion diseases associated with anchorless PrP.

Keywords:  liquid-liquid phase separation; membrane; neurodegenerative diseases; prion; protein aggregation

DOI:  https://doi.org/10.1073/pnas.2415250121
Neuroscience. 2024 Dec 30. pii: S0306-4522(24)00763-2. [Epub ahead of print]

Increased α-synuclein phosphorylation and oligomerization and altered enzymes in plasma of patients with Parkinson's disease.

Na Yin, Pengjie Li, Xuran Li, Xin Li, Yiming Wang, Xiaohan Yu, Yeyun Deng, Chaodong Wang, Shun Yu.

  The brain of patients with Parkinson's disease (PD) was characterized by increased phosphorylation and oligomerization of α-synuclein (α-syn) and altered activity of enzymes regulating α-syn phosphorylation and oligomerization. Whether increased α-syn phosphorylation and oligomerization as well as related enzyme changes can be detected in the plasma of PD patients remains unclear. Here, we showed that human α-syn proteins incubated in PD plasma formed more oligomerized α-syn (O-α-syn) and phosphorylated α-syn (pS-α-syn) than those in healthy control (HC) plasma. Receiver operating characteristic (ROC) curve indicated that α-syn oligomerization rate and phosphorylation rate discriminated PD patients well from HC subjects. Moreover, they were both positively correlated with Hoehn and Yahr staging and polo-like kinase 2 (PLK2, an enzyme promoting α-syn phosphorylation) levels, and negatively correlated with protein phosphatase 2A levels (PP2A, an enzyme dephosphorylating α-syn) and glucocerebrosidase (GCase, an enzyme whose deficiency causes α-syn oligomerization) activity and ceramide (a product of GCase and a natural PP2A activator) levels. The above results suggest that increased α-syn oligomerization and phosphorylation rates and related enzyme changes can be detected in PD plasma and used to discriminate PD patients from HC subjects and predict PD progression.

Keywords:  Enzyme; Oligomerization; Parkinson’s disease; Phosphorylation; α-synuclein

DOI:  https://doi.org/10.1016/j.neuroscience.2024.12.056
Commun Biol. 2025 Jan 02. 8(1): 2

NLS-binding deficient Kapβ2 reduces neurotoxicity via selective interaction with C9orf72-ALS/FTD dipeptide repeats.

Kevin M Kim, Amandeep Girdhar, Maria E Cicardi, Vaishnavi Kankate, Miyuki Hayashi, Ruoyu Yang, Jenny L Carey, Charlotte M Fare, James Shorter, Gino Cingolani, Davide Trotti, Lin Guo.

Arginine-rich dipeptide repeat proteins (R-DPRs) are highly toxic proteins found in patients with C9orf72-linked amyotrophic lateral sclerosis and frontotemporal dementia (C9-ALS/FTD). R-DPRs can cause toxicity by disrupting the natural phase behavior of RNA-binding proteins (RBPs). Mitigating this abnormal phase behavior is, therefore, crucial to reduce R-DPR-induced toxicity. Here, we use FUS as a model RBP to investigate the mechanism of R-DPR-induced aberrant RBP phase transition. We find that this phase transition can be mitigated by Kapβ2. However, as a nuclear import receptor and phase modifier for PY-NLS-containing RBPs, the function of WT Kapβ2 could lead to undesired interaction with its native substrates when used as therapeutics for C9-ALS/FTD. To address this issue, it is crucial to devise effective strategies that allow Kapβ2 to selectively target its binding to the R-DPRs, instead of the RBPs. We show that NLS-binding deficient Kapβ2W460A:W730A can indeed selectively interact with R-DPRs in FUS assembly without affecting normal FUS phase separation. Importantly, Kapβ2W460A:W730A prevents enrichment of poly(GR) in stress granules and mitigates R-DPR neurotoxicity. Thus, NLS-binding deficient Kapβ2 may be implemented as a potential therapeutic for C9-ALS/FTD.

DOI: https://doi.org/10.1038/s42003-024-07412-x
Nat Commun. 2024 Dec 30. 15(1): 10796

Localized molecular chaperone synthesis maintains neuronal dendrite proteostasis.

Célia Alecki, Javeria Rizwan, Phuong Le, Suleima Jacob-Tomas, Mario Fernandez Comaduran, Morgane Verbrugghe, Jia Ming Stella Xu, Sandra Minotti, James Lynch, Jeetayu Biswas, Tad Wu, Heather D Durham, Gene W Yeo, Maria Vera.

Proteostasis is maintained through regulated protein synthesis and degradation and chaperone-assisted protein folding. However, this is challenging in neuronal projections because of their polarized morphology and constant synaptic proteome remodeling. Using high-resolution fluorescence microscopy, we discover that hippocampal and spinal cord motor neurons of mouse and human origin localize a subset of chaperone mRNAs to their dendrites and use microtubule-based transport to increase this asymmetric localization following proteotoxic stress. The most abundant dendritic chaperone mRNA encodes a constitutive heat shock protein 70 family member (HSPA8). Proteotoxic stress also enhances HSPA8 mRNA translation efficiency in dendrites. Stress-mediated HSPA8 mRNA localization to the dendrites is impaired by depleting fused in sarcoma-an amyotrophic lateral sclerosis-related protein-in cultured spinal cord mouse motor neurons or by expressing a pathogenic variant of heterogenous nuclear ribonucleoprotein A2/B1 in neurons derived from human induced pluripotent stem cells. These results reveal a neuronal stress response in which RNA-binding proteins increase the dendritic localization of HSPA8 mRNA to maintain proteostasis and prevent neurodegeneration.

DOI: https://doi.org/10.1038/s41467-024-55055-7
Mol Neurodegener. 2024 Dec 31. 19(1): 100

Distinct regulation of Tau Monomer and aggregate uptake and intracellular accumulation in human neurons.

Amir T Marvian, Tabea Strauss, Qilin Tang, Benjamin J Tuck, Sophie Keeling, Daniel Rüdiger, Negar Mirzazadeh Dizaji, Hossein Mohammad-Beigi, Brigitte Nuscher, Pijush Chakraborty, Duncan S Sutherland, William A McEwan, Thomas Köglsperger, Stefan Zahler, Markus Zweckstetter, Stefan F Lichtenthaler, Wolfgang Wurst, Sigrid Schwarz, Günter Höglinger.

   BACKGROUND: The prion-like spreading of Tau pathology is the leading cause of disease progression in various tauopathies. A critical step in propagating pathologic Tau in the brain is the transport from the extracellular environment and accumulation inside naïve neurons. Current research indicates that human neurons internalize both the physiological extracellular Tau (eTau) monomers and the pathological eTau aggregates. However, similarities or differences in neuronal transport mechanisms between Tau species remain elusive.
METHOD: Monomers, oligomers, and fibrils of recombinant 2N4R Tau were produced and characterized by biochemical and biophysical methods. A neuronal eTau uptake and accumulation assay was developed for human induced pluripotent stem cell-derived neurons (iPSCNs) and Lund human mesencephalic cells (LUHMES)-derived neurons. Mechanisms of uptake and cellular accumulation of eTau species were studied by using small molecule inhibitors of endocytic mechanisms and siRNAs targeting Tau uptake mediators.
RESULTS: Extracellular Tau aggregates accumulated more than monomers in human neurons, mainly due to the higher efficiency of small fibrillar and soluble oligomeric aggregates in intraneuronal accumulation. A competition assay revealed a distinction in the neuronal accumulation between physiological eTau Monomers and pathology-relevant aggregates, suggesting differential transport mechanisms. Blocking heparan sulfate proteoglycans (HSPGs) with heparin only inhibited the accumulation of eTau aggregates, whereas monomers' uptake remained unaltered. At the molecular level, the downregulation of genes involved in HSPG synthesis exclusively blocked neuronal accumulation of eTau aggregates but not monomers, suggesting its role in the transport of pathologic Tau. Moreover, the knockdown of LRP1, as a receptor of Tau, mainly reduced the accumulation of monomeric form, confirming its involvement in Tau's physiological transport.
CONCLUSION: These data propose that despite the similarity in the cellular mechanism, the uptake and accumulation of eTau Monomers and aggregates in human neurons are regulated by different molecular mediators. Thus, they address the possibility of targeting the pathological spreading of Tau aggregates without disturbing the probable physiological or non-pathogenic transport of Tau Monomers.

Keywords:  Cell-to-cell spreading; Extracellular Tau; HSPGs; LRP1; Neurodegeneration; Uptake; VPS35

DOI:  https://doi.org/10.1186/s13024-024-00786-w