bims-proned Biomed News
on Proteostasis in neurodegeneration
Issue of 2024‒10‒27
sixteen papers selected by
Verena Kohler, Umeå University
  1. Dual Role of Anionic Lipids in Amyloid Aggregation.
  2. The role of polo-like kinases 2 in the proteasomal and lysosomal degradation of alpha-synuclein in neurons.
  3. Evaluation of Alpha-Synuclein and Tau Antiaggregation Activity of Urea and Thiourea-Based Small Molecules for Neurodegenerative Disease Therapeutics.
  4. A hydrophobic core stabilizes the residual structure in the RRM2 intermediate state of the ALS-linked protein TDP-43.
  5. A review of proposed mechanisms for neurodegenerative disease.
  6. Emerging role of microglia in inter-cellular transmission of α-synuclein in Parkinson's disease.
  7. Novel prospects in targeting neurodegenerative disorders via autophagy.
  8. RNA G-quadruplexes form scaffolds that promote neuropathological α-synuclein aggregation.
  9. Generation of nanobodies with conformational specificity for tau oligomers that recognize tau aggregates from human Alzheimer's disease samples.
  10. Binding of α-synuclein to ACO2 promotes progressive mitochondrial dysfunction in Parkinson's disease models.
  11. NDRG1 upregulation by ubiquitin proteasome system dysfunction aggravates neurodegeneration.
  12. Microglial Melatonin Receptor 1 Degrades Pathological Alpha-Synuclein Through Activating LC3-Associated Phagocytosis In Vitro.
  13. Investigation of Fibrillar Aggregates Formed by Pathogenic Pre-Pro-Vasopressin Mutants that Cause ADNDI.
  14. Morphological and Molecular Profiling of Amyloid-β Species in Alzheimer's Pathogenesis.
  15. Accelerated Alzheimer's Aβ-42 secondary nucleation chronologically visualized on fibril surfaces.
  16. CRBN modulates synuclein fibrillation via degradation of DNAJB1 in mouse model of Parkinson disease.
  1. J Phys Chem B. 2024 Oct 25.
    Dual Role of Anionic Lipids in Amyloid Aggregation.
    Meenal Jain, Silvina Matysiak.
      Neurodegenerative diseases, such as Alzheimer's, Parkinson's, and Huntington's, affect millions worldwide and share a common feature: the aggregation of intrinsically disordered proteins into toxic oligomers that interact with cell membranes. In Alzheimer's disease (AD), amyloid-beta (Aβ) peptides accumulate and bind to plasma membranes, potentially disrupting cellular function. The complex interplay between amyloidogenic peptides and lipid membranes, particularly the role of anionic lipids, is crucial in disease pathogenesis but challenging to characterize experimentally. The literature presents conflicting results on the influence of anionic lipids on peptide aggregation kinetics, highlighting a knowledge gap. To address this, we used coarse-grained molecular dynamics (CG-MD) simulations to study interactions between a model amyloidogenic peptide, amyloid-β's K16LVFFAE22 fragment (Aβ16-22), and mixed lipid bilayers. We used phosphatidylserine (PS) and phosphatidylcholine (PC) as representative anionic and zwitterionic lipids, respectively, examining the mixed bilayer compositions of 0% PS-100% PC, 10% PS-90% PC, and 30% PS-70% PC. Our simulations revealed that membranes enriched in anionic lipids enhance peptide adsorption and interaction kinetics. The aggregation dynamics was modulated by two competing factors: increased local peptide concentration near negatively charged membranes, which promoted aggregation, and peptide-lipid interactions, which slowed it down. Higher percentages of anionic lipids led to smaller and more ordered aggregates and enhanced lipid demixing, leading to the formation of PS clusters. These findings contribute to understanding membrane-mediated peptide aggregation in neurodegenerative disorders, potentially guiding new therapeutic strategies targeting the early stages of protein aggregation in various neurodegenerative diseases.
    DOI:  https://doi.org/10.1021/acs.jpcb.4c05636
  2. FASEB J. 2024 Oct;38(20): e70121
    The role of polo-like kinases 2 in the proteasomal and lysosomal degradation of alpha-synuclein in neurons.
    Chun Chau Sung, Wai Yun Lam, Kenny K K Chung.
      Parkinson's disease (PD) is a neurodegenerative disorder caused by the degeneration of dopaminergic neurons in the brain stem. PD is mostly sporadic, but familial PD (FPD) cases are recorded in different studies. The first gene mutation that is linked to FPD is α-synuclein (α-syn). It was then found that α-syn is also accumulated in Lewy body (LB), a classical pathological hallmark in PD patients. Different studies have shown that α-syn accumulation and aggregation can be a crucial factor contributing to the degeneration of dopaminergic neurons in PD. α-syn has been found to be degraded by the ubiquitin proteasomal system (UPS) and autophagy-lysosomal pathway (ALP). In this study, we initially explored how α-syn phosphorylation by GRK6, PLK2 and CK2α would facilitate its degradation in relation to the UPS or ALP. Unexpectedly, we found that the degradation of α-syn through PLK2 phosphorylation could be modulated by UPS and ALP in a novel mechanism. Specially, attenuation of UPS could increase the amount of PLK2 and then could facilitate the phosphorylation and degradation of α-syn through ALP. To test this further in vivo, we attenuate the proteasomal activity in a well-established A53T α-syn transgenic PD mouse model. We found that attenuation of proteasomal activity in the A53T α-syn transgenic mice could reduce the accumulation of α-syn in the striatum and midbrain. Based on our results, this study provides a new insight into how α-syn is degraded through the UPS and ALP.
    Keywords:  autophagy–lysosomal pathway; phosphorylation; protein degradation; ubiquitin‐proteasomal system; α‐synuclein
    DOI:  https://doi.org/10.1096/fj.202401035R
  3. ACS Chem Neurosci. 2024 Oct 22.
    Evaluation of Alpha-Synuclein and Tau Antiaggregation Activity of Urea and Thiourea-Based Small Molecules for Neurodegenerative Disease Therapeutics.
    Susantha K Ganegamage, Taiwo A Ademoye, Henika Patel, Heba Alnakhala, Arati Tripathi, Cuong Calvin Duc Nguyen, Khai Pham, Germán Plascencia-Villa, Xiongwei Zhu, George Perry, Shiliang Tian, Ulf Dettmer, Cristian Lasagna-Reeves, Jessica S Fortin.
      Alzheimer's disease (AD) and Parkinson's disease (PD) are multifactorial, chronic diseases involving neurodegeneration. According to recent studies, it is hypothesized that the intraneuronal and postsynaptic accumulation of misfolded proteins such as α-synuclein (α-syn) and tau, responsible for Lewy bodies (LB) and tangles, respectively, disrupts neuron functions. Considering the co-occurrence of α-syn and tau inclusions in the brains of patients afflicted with subtypes of dementia and LB disorders, the discovery and development of small molecules for the inhibition of α-syn and tau aggregation can be a potentially effective strategy to delay neurodegeneration. Urea is a chaotropic agent that alters protein solubilization and hydrophobic interactions and inhibits protein aggregation and precipitation. The presence of three hetero atoms (O/S and N) in proximity can coordinate with neutral, mono, or dianionic groups to form stable complexes in the biological system. Therefore, in this study, we evaluated urea and thiourea linkers with various substitutions on either side of the carbamide or thiocarbamide functionality to compare the aggregation inhibition of α-syn and tau. A thioflavin-T (ThT) fluorescence assay was used to evaluate the level of fibril formation and monitor the anti-aggregation effect of the different compounds. We opted for transmission electron microscopy (TEM) as a direct means to confirm the anti-fibrillar effect. The oligomer formation was monitored via the photoinduced cross-linking of unmodified proteins (PICUP). The anti-inclusion and anti-seeding activities of the best compounds were evaluated using M17D intracellular inclusion and biosensor cell-based assays, respectively. Disaggregation experiments were performed with amyloid plaques extracted from AD brains. The analogues with indole, benzothiazole, or N,N-dimethylphenyl on one side with halo-substituted aromatic moieties had shown less than 15% cutoff fluorescence obtained with the ThT assay. Our lead molecules 6T and 14T reduced α-syn oligomerization dose-dependently based on the PICUP assays but failed at inhibiting tau oligomer formation. The anti-inclusion effect of our lead compounds was confirmed using the M17D neuroblastoma cell model. Compounds 6T and 14T exhibited an anti-seeding effect on tau using biosensor cells. In contrast to the control, disaggregation experiments showed fewer Aβ plaques with our lead molecules (compounds 6T and 14T). Pharmacokinetics (PK) mice studies demonstrated that these two thiourea-based small molecules have the potential to cross the blood-brain barrier in rodents. Urea and thiourea linkers could be further improved for their PK parameters and studied for the anti-inclusion, anti-seeding, and disaggregation effects using transgenic mice models of neurodegenerative diseases.
    Keywords:  Alzheimer’s disease; Parkinson’s disease; anti-aggregation; neurodegeneration; thiourea; urea
    DOI:  https://doi.org/10.1021/acschemneuro.4c00282
  4. J Mol Biol. 2024 Oct 17. pii: S0022-2836(24)00445-5. [Epub ahead of print] 168823
    A hydrophobic core stabilizes the residual structure in the RRM2 intermediate state of the ALS-linked protein TDP-43.
    Brian C Mackness, Brittany R Morgan, Laura M Deveau, Sagar V Kathuria, Jill A Zitzewitz, Francesca Massi.
      Folding intermediates mediate both protein folding and the misfolding and aggregation observed in human diseases, including amyotrophic lateral sclerosis (ALS), and are prime targets for therapeutic interventions. In this study, we identified the core nucleus of structure for a folding intermediate in the second RNA recognition motif (RRM2) of the ALS-linked RNA-binding protein, TDP-43, using a combination of experimental and computational approaches. Urea equilibrium unfolding studies revealed that the RRM2 intermediate state consists of collapsed residual secondary structure localized to the N-terminal half of RRM2, while the C-terminus is largely disordered. Steered molecular dynamics simulations and mutagenesis studies yielded key stabilizing hydrophobic contacts that, when mutated to alanine, severely disrupt the overall fold of RRM2. In combination, these findings suggest a role for this RRM intermediate in normal TDP-43 function as well as serving as a template for misfolding and aggregation through the low stability and non-native secondary structure.
    Keywords:  neurodegenerative diseases; protein conformation; protein misfolding; protein stability; protein structure
    DOI:  https://doi.org/10.1016/j.jmb.2024.168823
  5. Front Aging Neurosci. 2024 ;16 1370580
    A review of proposed mechanisms for neurodegenerative disease.
    Benjamin M Kelser, Eric M Teichner, Robert C Subtirelu, Kevin N Hoss.
      Neurodegenerative diseases, such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis (ALS) affect millions and present significant challenges in healthcare and treatment costs. The debate in the field pivots around two hypotheses: synaptic spread and selective vulnerability. Pioneers like Virginia Lee and John Trojanowski have been instrumental in identifying key proteins (tau, alpha-synuclein, TDP-43) central to these diseases. The synaptic spread hypothesis suggests a cell-to-cell propagation of pathogenic proteins across neuronal synapses, influencing disease progression, with studies highlighting the role of proteins like alpha-synuclein and amyloid-beta in this process. In contrast, the selective vulnerability hypothesis proposes inherent susceptibility of certain neurons to degeneration due to factors like metabolic stress, leading to protein aggregation. Recent advancements in neuroimaging, especially PET/MRI hybrid imaging, offer new insights into these mechanisms. While both hypotheses offer substantial evidence, their relative contributions to neurodegenerative processes remain to be fully elucidated. This uncertainty underscores the necessity for continued research, with a focus on these hypotheses, to develop effective treatments for these devastating diseases.
    Keywords:  TDP-43; alpha-synuclein; neurodegenerative disease; neuroimaging advances; protein aggregation; selective vulnerability hypothesis; synaptic spread hypothesis; tau
    DOI:  https://doi.org/10.3389/fnagi.2024.1370580
  6. Front Aging Neurosci. 2024 ;16 1411104
    Emerging role of microglia in inter-cellular transmission of α-synuclein in Parkinson's disease.
    Xiangbo Zhang, Haiyang Yu, Juan Feng.
      Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, significantly prejudicing the health and quality of life of elderly patients. The main pathological characteristics of PD are the loss of dopaminergic neurons in the substantia nigra (SN) as well as abnormal aggregation of α-synuclein (α-syn) monomers and oligomers, which results in formation of Lewy bodies (LBs). Intercellular transmission of α-syn is crucial for PD progression. Microglia play diverse roles in physiological and pathological conditions, exhibiting neuroprotective or neurotoxic effects; moreover, they may directly facilitate α-syn propagation. Various forms of extracellular α-syn can be taken up by microglia through multiple mechanisms, degraded or processed into more pathogenic forms, and eventually released into extracellular fluid or adjacent cells. This review discusses current literature regarding the molecular mechanisms underlying the uptake, degradation, and release of α-syn by microglia.
    Keywords:  Parkinson’s disease; microglia; neurodegeneration; propagation; α-synuclein
    DOI:  https://doi.org/10.3389/fnagi.2024.1411104
  7. Eur J Pharmacol. 2024 Oct 18. pii: S0014-2999(24)00750-7. [Epub ahead of print]984 177060
    Novel prospects in targeting neurodegenerative disorders via autophagy.
    Shumayila Khan, Saurabh Upadhyay, Md Imtaiyaz Hassan.
      Protein aggregation occurs as a consequence of dysfunction in the normal cellular proteostasis, which leads to the accumulation of toxic fibrillar aggregates of certain proteins in the cell. Enhancing the activity of proteolytic pathways may serve as a way of clearing these aggregates in a cell, and consequently, autophagy has surfaced as a promising target for the treatment of neurodegenerative disorders. Several strategies involving small molecule compounds that stimulate autophagic pathway of cell have been discovered. However, despite many compounds having demonstrated favorable outcomes in experimental disease models, the translation of these findings into clinical benefits for patient's remains limited. Consequently, alternative strategies are actively being explored to effectively target neurodegeneration via autophagy modulation. Recently, newer approaches such as modulation of expression of autophagic genes have emerged as novel and interesting areas of research in this field, which hold promising potential in neuroprotection. Similarly, as discussed for the first time in this review, the use of autophagy-inducing nanoparticles by utilizing their physicochemical properties to stimulate the autophagic process, rather than relying on their role as drug carriers, offers a completely fresh avenue for targeting neurodegeneration without the risk of drug-associated adverse effects. This review provides fresh perspectives on developing autophagy-targeted therapies for neurodegenerative disorders. Additionally, it discusses the challenges and impediments of implementing these strategies to alleviate the pathogenesis of neurodegenerative disorders in clinical settings and highlights the prospects and directions of future research in this context.
    Keywords:  Alzheimer's disease; Autophagy; Huntington's disease; Neurodegeneration; Neuroprotection; Neurotherapeutics; Parkinson's disease; Protein aggregation
    DOI:  https://doi.org/10.1016/j.ejphar.2024.177060
  8. Cell. 2024 Oct 14. pii: S0092-8674(24)01134-6. [Epub ahead of print]
    RNA G-quadruplexes form scaffolds that promote neuropathological α-synuclein aggregation.
    Kazuya Matsuo, Sefan Asamitsu, Kohei Maeda, Hiroyoshi Suzuki, Kosuke Kawakubo, Ginji Komiya, Kenta Kudo, Yusuke Sakai, Karin Hori, Susumu Ikenoshita, Shingo Usuki, Shiori Funahashi, Hideki Oizumi, Atsushi Takeda, Yasushi Kawata, Tomohiro Mizobata, Norifumi Shioda, Yasushi Yabuki.
      Synucleinopathies, including Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy, are triggered by α-synuclein aggregation, triggering progressive neurodegeneration. However, the intracellular α-synuclein aggregation mechanism remains unclear. Herein, we demonstrate that RNA G-quadruplex assembly forms scaffolds for α-synuclein aggregation, contributing to neurodegeneration. Purified α-synuclein binds RNA G-quadruplexes directly through the N terminus. RNA G-quadruplexes undergo Ca2+-induced phase separation and assembly, accelerating α-synuclein sol-gel phase transition. In α-synuclein preformed fibril-treated neurons, RNA G-quadruplex assembly comprising synaptic mRNAs co-aggregates with α-synuclein upon excess cytoplasmic Ca2+ influx, eliciting synaptic dysfunction. Forced RNA G-quadruplex assembly using an optogenetic approach evokes α-synuclein aggregation, causing neuronal dysfunction and neurodegeneration. The administration of 5-aminolevulinic acid, a protoporphyrin IX prodrug, prevents RNA G-quadruplex phase separation, thereby attenuating α-synuclein aggregation, neurodegeneration, and progressive motor deficits in α-synuclein preformed fibril-injected synucleinopathic mice. Therefore, Ca2+ influx-induced RNA G-quadruplex assembly accelerates α-synuclein phase transition and aggregation, potentially contributing to synucleinopathies.
    Keywords:  5-aminolevulinic acid; Ca(2+) influx; RNA G-quadruplex; neurodegeneration; phase separation; sol-gel phase transition; synucleinopathies; α-synuclein
    DOI:  https://doi.org/10.1016/j.cell.2024.09.037
  9. Biomater Sci. 2024 Oct 22.
    Generation of nanobodies with conformational specificity for tau oligomers that recognize tau aggregates from human Alzheimer's disease samples.
    Nikki McArthur, Jay D Squire, Ogechukwu J Onyeachonam, Nemil N Bhatt, Cynthia Jerez, Abigail L Holberton, Peter M Tessier, Levi B Wood, Rakez Kayed, Ravi S Kane.
      Tauopathies are neurodegenerative diseases that involve tau misfolding and aggregation in the brain. These diseases, including Alzheimer's disease (AD), are some of the least understood and most difficult to treat neurodegenerative disorders. Antibodies and antibody fragments that target tau oligomers, which are especially toxic forms of tau, are promising options for immunotherapies and diagnostic tools for tauopathies. In this study, we have developed conformational, tau oligomer-specific nanobodies, or single-domain antibodies. We demonstrate that these nanobodies, OT2.4 and OT2.6, are highly specific for tau oligomers relative to tau monomers and fibrils. We used epitope mapping to verify that these nanobodies bind to discontinuous epitopes on tau and to support the idea that they interact with a conformation present in the oligomeric, and not monomeric or fibrillar, forms of tau. We show that these nanobodies interact with tau oligomers in brain samples from AD patients and from healthy older adults with primary age-related tauopathy. Our results demonstrate the potential of these nanobodies as tau oligomer-specific binding reagents and future tauopathy therapeutics and diagnostics.
    DOI:  https://doi.org/10.1039/d4bm00707g
  10. Redox Biol. 2024 Oct 17. pii: S2213-2317(24)00377-X. [Epub ahead of print]77 103399
    Binding of α-synuclein to ACO2 promotes progressive mitochondrial dysfunction in Parkinson's disease models.
    Jie Jiao, Ge Gao, Junge Zhu, Chaodong Wang, Lei Liu, Hui Yang.
      The accumulation of α-synuclein (α-syn), a key protein in Parkinson's disease (PD), contributes to progressive neuronal damage associated with mitochondrial dysfunction and interactions with various proteins. However, the precise mechanism by which α-syn affects energy metabolism remains unclear. In our study, we used human α-syn (hα-syn) transgenic mice, which exhibit progressive neuronal decline. Through an immunoprecipitation assay specific to hα-syn, we identified an enzyme in the mitochondrial tricarboxylic acid (TCA) cycle as a binding partner-mitochondrial aconitase 2 (ACO2), which converts citrate to isocitrate. Hα-syn increasingly interacted with ACO2 in mitochondria as mice aged, correlating with a progressive decrease in ACO2 activity. The overexpression of ACO2 and the addition of isocitrate, a downstream metabolite of ACO2, were observed to alleviate hα-syn-induced mitochondrial dysfunction and cytotoxicity. Furthermore, we designed an interfering peptide to block the interaction between ACO2 and hα-syn, which showed therapeutic effects in reducing hα-syn toxicity in vitro and in vivo. Our research establishes a direct link between α-syn and the TCA cycle and identifies ACO2 as a promising therapeutic target for improving mitochondrial function and reducing α-syn neurotoxicity in PD.
    Keywords:  Interfering peptides; Mitochondrial aconitase 2; Mitochondrial damage; Parkinson's disease; α-Synuclein
    DOI:  https://doi.org/10.1016/j.redox.2024.103399
  11. Mol Brain. 2024 Oct 23. 17(1): 77
    NDRG1 upregulation by ubiquitin proteasome system dysfunction aggravates neurodegeneration.
    Tomonori Hoshino, Atsushi Mukai, Hirofumi Yamashita, Hidemi Misawa, Makoto Urushitani, Yoshitaka Tashiro, Shu-Ichi Matsuzawa, Ryosuke Takahashi.
      Protein turnover is crucial for cell survival, and the impairment of proteostasis leads to cell death. Aging is associated with a decline in proteostasis, as the progressive accumulation of damaged proteins is a hallmark of age-related disorders such as neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). We previously discovered that the declining function of the ubiquitin-proteasome system (UPS) in motor neurons contributes to sporadic ALS pathologies, such as progressive motor neuron loss, protein accumulation, and glial activation. However, the mechanisms of UPS dysfunction-induced cell damage, such as cell death and aggregation, are not fully understood. This study used transcriptome analysis of motor neurons with UPS dysfunction and found that the expression of N-myc downstream regulated 1 (NDRG1) gets upregulated by UPS dysfunction. Additionally, the upregulation of NDRG1 induces cell death in the Neuro2a mouse neuroblastoma cell line. These results suggest that NDRG1 is a potential marker for UPS dysfunction and may play a role in neurodegeneration, such as that seen in ALS.
    Keywords:  Amyotrophic lateral sclerosis; Cell death; NDRG1; Neurodegeneration; Proteasome; Psmc4 (Rpt3)
    DOI:  https://doi.org/10.1186/s13041-024-01150-1
  12. CNS Neurosci Ther. 2024 Oct;30(10): e70088
    Microglial Melatonin Receptor 1 Degrades Pathological Alpha-Synuclein Through Activating LC3-Associated Phagocytosis In Vitro.
    Xiao-Yu Yao, Bing-Er Cao, Jun-Yi Liu, Qian-Kun Lv, Jia-Rui Zhang, Xiao-Yu Cheng, Cheng-Jie Mao, Quan-Hong Ma, Fen Wang, Chun-Feng Liu.
      AIMS: Parkinson's disease (PD) is characterized by the formation of Lewy bodies (LBs), primarily constituted of α-synuclein (α-Syn). Microglial cells exhibit specific reactivity toward misfolded proteins such as α-Syn. However, the exact clearance mechanism and related molecular targets remain elusive.METHODS: BV2 cells, primary microglia from wild-type and MT1 knockout mice, and primary cortical neurons were utilized as experimental models. The study investigated relevant mechanisms by modulating microglial MT1 expression through small RNA interference (RNAi) and lentiviral overexpression techniques. Furthermore, pathological aggregation of α-Syn was induced using pre-formed fibrils (PFF) α-Syn. Co-immunoprecipitation, immunofluorescence, Western blot (WB), and quantitative real-time PCR were used to elucidate the mechanisms of molecular regulation.
    RESULTS: In this study, we elucidated the regulatory role of the melatonin receptor 1 (MT1) in the microglial phagocytic process. Following MT1 knockout, the ability of microglial cells to engulf latex beads and zymosan particles decreased, subsequently affecting the phagocytic degradation of fibrillar α-Syn by microglial cells. Furthermore, the loss of MT1 receptors in microglial cells exacerbates the aggregation of α-Syn in neurons induced by pre-formed fibrils (PFF) α-Syn. Mechanistically, MT1 influences the phagocytic function of microglial cells by regulating the Rubicon-dependent LC3-associated phagocytosis (LAP) pathway.
    CONCLUSION: Taken together, the results suggest the neuroprotective function of microglial cells in clearing α-Syn through MT1-mediated LAP, highlighting the potential key role of MT1 in pathogenic mechanisms associated with α-Syn.
    Keywords:  LC3‐associated phagocytosis; Parkinson's disease; melatonin receptor 1; microglia; α‐synuclein
    DOI:  https://doi.org/10.1111/cns.70088
  13. J Clin Endocrinol Metab. 2024 Oct 25. pii: dgae749. [Epub ahead of print]
    Investigation of Fibrillar Aggregates Formed by Pathogenic Pre-Pro-Vasopressin Mutants that Cause ADNDI.
    Refika Dilara Vaizoglu, Beril Erdem, Mehmet Gul, Ceren Acar, Huseyin Ozgur Ozdemirel, Emel Saglar Ozer, Hatice Mergen.
      CONTEXT: Aggregations of unfolded or misfolded proteins, both inside and outside cells, are implicated in numerous diseases, collectively known as amyloidosis. Particularly, Autosomal dominant neurohypophyseal diabetes insipidus (ADNDI) is a rare disease caused by mutations in the AVP-NPII gene, leading to the inability to secrete arginine vasopressin (AVP). These misfolded proteins accumulate within the endoplasmic reticulum (ER), causing cellular dysfunction.OBJECTIVE: This study aimed to investigate the formation of amyloid-like aggregates within the cell resulting from misfolded mutant precursor proteins, which induce disulfide-linked oligomers due to the G45C, 207_209delGGC, G88V, C98X, C104F, E108D-1, E108D-2 and R122H mutations identified by our group in the AVP-NPII gene of ADNDI patients.
    METHODS: De-glycosylation studies were performed to analyze the glycosylation patterns of mutant protein precursors. The involvement of these precursors in the ER-related degradation pathway was studied by conducting protease inhibition experiments. Disulfide-linked oligomer analysis determined the oligomerization status of the mutant precursors. Immunofluorescence and electron microscopy studies provided evidence of aggregate structures in the ER lumen. In vitro studies involving bacterial expression and fibril formation in E. coli.
    RESULTS: Our findings demonstrated that the N-glycan structure of mutant precursors remains intact within the ER. Protease inhibition experiments indicated the involvement of these precursors in the ER-related degradation pathway. Disulfide-linked oligomer analysis revealed homo-oligomer structures in mutations. Immunofluorescence and electron microscopy studies confirmed the presence of aggregate structures in the ER lumen. In vitro studies showed that mutant precursors could form fibril structures in E. coli.
    CONCLUSION: Our study may support the idea that ADNDI belongs to the group of neurodegenerative diseases due to the formation of fibrillar amyloid aggregates in the cell.
    Keywords:   AVP-NPII ; ADNDI; Aggregates; Amyloid; Neurodegenerative Diseases
    DOI:  https://doi.org/10.1210/clinem/dgae749
  14. Mol Neurobiol. 2024 Oct 24.
    Morphological and Molecular Profiling of Amyloid-β Species in Alzheimer's Pathogenesis.
    Zaida L Almeida, Daniela C Vaz, Rui M M Brito.
      Alzheimer's disease (AD) is the most common form of dementia around the world (~ 65%). Here, we portray the neuropathology of AD, biomarkers, and classification of amyloid plaques (diffuse, non-cored, dense core, compact). Tau pathology and its involvement with Aβ plaques and cell death are discussed. Amyloid cascade hypotheses, aggregation mechanisms, and molecular species formed in vitro and in vivo (on- and off-pathways) are described. Aβ42/Aβ40 monomers, dimers, trimers, Aβ-derived diffusible ligands, globulomers, dodecamers, amylospheroids, amorphous aggregates, protofibrils, fibrils, and plaques are characterized (structure, size, morphology, solubility, toxicity, mechanistic steps). An update on AD-approved drugs by regulatory agencies, along with new Aβ-based therapies, is presented. Beyond prescribing Aβ plaque disruptors, cholinergic agonists, or NMDA receptor antagonists, other therapeutic strategies (RNAi, glutaminyl cyclase inhibitors, monoclonal antibodies, secretase modulators, Aβ aggregation inhibitors, and anti-amyloid vaccines) are already under clinical trials. New drug discovery approaches based on "designed multiple ligands", "hybrid molecules", or "multitarget-directed ligands" are also being put forward and may contribute to tackling this highly debilitating and fatal form of human dementia.
    Keywords:  Alzheimer’s disease (AD); Amyloid plaques; Amyloid-beta (Aβ) peptide; Aβ-based therapies; Protein aggregation; Tau protein
    DOI:  https://doi.org/10.1007/s12035-024-04543-4
  15. Sci Adv. 2024 Oct 25. 10(43): eadp5059
    Accelerated Alzheimer's Aβ-42 secondary nucleation chronologically visualized on fibril surfaces.
    Peter Niraj Nirmalraj, Shayon Bhattacharya, Damien Thompson.
      Protein fibril surfaces tend to generate toxic oligomers catalytically. To date, efforts to study the accelerated aggregation steps involved with Alzheimer's disease-linked amyloid-β (Aβ)-42 proteins on fibril surfaces have mainly relied on fluorophore-based analytics. Here, we visualize rare secondary nucleation events on the surface of Aβ-42 fibrils from embryonic to endpoint stages using liquid-based atomic force microscopy. Nanoscale imaging supported by atomic-scale molecular simulations tracked the adsorption and proliferation of oligomeric assemblies at nonperiodically spaced catalytic sites on the fibril surface. Upon confirming that fibril edges are preferential binding sites for oligomers during embryonic stages, the secondary fibrillar size changes were quantified during the growth stages. Notably, a small population of fibrils that displayed higher surface catalytic activity was identified as superspreaders. Profiling secondary fibrils during endpoint stages revealed a nearly threefold increase in their surface corrugation, a parameter we exploit to classify fibril subpopulations.
    DOI:  https://doi.org/10.1126/sciadv.adp5059
  16. NPJ Parkinsons Dis. 2024 Oct 23. 10(1): 194
    CRBN modulates synuclein fibrillation via degradation of DNAJB1 in mouse model of Parkinson disease.
    Uroos Akber, Jun-Hyung Jung, Heewoong Yoon, Jiwon Seo, Chul-Seung Park.
      Cereblon (CRBN) is a substrate recruiter for CRL4CRBN E3 ubiquitin ligase system playing a plethora of pivotal roles for biological systems. Here, we identified DNAJB1 (DJ1) as endogenous substrate of CRBN and report how CRBN influences the aggregation and toxicity of alpha-synuclein (α-SYN) via modulation of DJ1. CRBN interferes with molecular activities of DJ1 in vitro, in cells, and in vivo resulting in a reduced disaggregation of α-SYN fibrils, increased formation of preformed fibrils (PFFs) of α-SYN, and high susceptibility of mice to MPTP and PFF-induced neurotoxicity. Depletion of Crbn improves the behavioral and biochemical responses of mice towards neurotoxic insult. Finally, we designed a peptide inhibitor to inhibit the recruitment of DJ1 to CRBN for ubiquitination, resulting in an enhanced supply of DJ1 to counteract the toxicity of aggregated α-SYN. Our data has important implications for development of CRBN-targeting therapies that could prevent or delay progression of neurodegenerative synucleinopathy.
    DOI:  https://doi.org/10.1038/s41531-024-00801-3
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