bims-proned Biomed News
on Proteostasis in neurodegeneration
Issue of 2024‒02‒11
sixteen papers selected by
Verena Kohler, Umeå University
  1. Modulation of α-synuclein in vitro aggregation kinetics by its alternative splice isoforms.
  2. Ensemble-based design of tau to inhibit aggregation while preserving biological activity.
  3. Discovery of small molecule benzothiazole and indole derivatives tackling tau 2N4R and α-synuclein fibrils.
  4. Aquaporin-4 and Parkinson's Disease.
  5. Intra-condensate demixing of TDP-43 inside stress granules generates pathological aggregates.
  6. C9orf72-associated dipeptide protein repeats form A11-positive oligomers in amyotrophic lateral sclerosis and frontotemporal dementia.
  7. Computational investigation on the conformational dynamics of C-terminal truncated α-synuclein bound to membrane.
  8. A label-free high-throughput protein solubility assay and its application to Aβ40.
  9. RNA and the RNA-binding protein FUS act in concert to prevent TDP-43 spatial segregation.
  10. Secondary Modification of S100B Influences Anti Amyloid-β Aggregation Activity and Alzheimer's Disease Pathology.
  11. The Inhibition Effect of Epigallocatechin-3-Gallate on the Co-Aggregation of Amyloid-β and Human Islet Amyloid Polypeptide Revealed by Replica Exchange Molecular Dynamics Simulations.
  12. RACK1 and IRE1 participate in the translational quality control of amyloid precursor protein in Drosophila models of Alzheimer's disease.
  13. TDP-43 dysregulation of polyadenylation site selection is a defining feature of RNA misprocessing in ALS/FTD and related disorders.
  14. Crosstalk between tau protein autoproteolysis and amyloid fibril formation.
  15. Dysregulation of stress granule dynamics by DCTN1 deficiency exacerbates TDP-43 pathology in Drosophila models of ALS/FTD.
  16. Lysosomal stress drives the release of pathogenic α-synuclein from macrophage lineage cells via the LRRK2-Rab10 pathway.
  1. Proc Natl Acad Sci U S A. 2024 Feb 13. 121(7): e2313465121
    Modulation of α-synuclein in vitro aggregation kinetics by its alternative splice isoforms.
    Alexander Röntgen, Zenon Toprakcioglu, James E Tomkins, Michele Vendruscolo.
      The misfolding and aggregation of α-synuclein is linked to a family of neurodegenerative disorders known as synucleinopathies, the most prominent of which is Parkinson's disease (PD). Understanding the aggregation process of α-synuclein from a mechanistic point of view is thus of key importance. SNCA, the gene encoding α-synuclein, comprises six exons and produces various isoforms through alternative splicing. The most abundant isoform is expressed as a 140-amino acid protein (αSyn-140), while three other isoforms, αSyn-126, αSyn-112, and αSyn-98, are generated by skipping exon 3, exon 5, or both exons, respectively. In this study, we performed a detailed biophysical characterization of the aggregation of these four isoforms. We found that αSyn-112 and αSyn-98 exhibit accelerated aggregation kinetics compared to αSyn-140 and form distinct aggregate morphologies, as observed by transmission electron microscopy. Moreover, we observed that the presence of relatively small amounts of αSyn-112 accelerates the aggregation of αSyn-140, significantly reducing the aggregation half-time. These results indicate a potential role of alternative splicing in the pathological aggregation of α-synuclein and provide insights into how this process could be associated with the development of synucleinopathies.
    Keywords:  alpha-synuclein; proteoforms; splice isoforms
    DOI:  https://doi.org/10.1073/pnas.2313465121
  2. Res Sq. 2024 Jan 16. pii: rs.3.rs-3796916. [Epub ahead of print]
    Ensemble-based design of tau to inhibit aggregation while preserving biological activity.
    Lukasz Joachimiak, Sofia Bali, Ruhar Singh, Pawel Wydorski, Aleksandra Wosztyl, Valerie Perez, Dailu Chen, Josep Rizo.
      The microtubule-associated protein tau is implicated in neurodegenerative diseases characterized by amyloid formation. Mutations associated with frontotemporal dementia increase tau aggregation propensity and disrupt its endogenous microtubule-binding activity. The structural relationship between aggregation propensity and biological activity remains unclear. We employed a multi-disciplinary approach, including computational modeling, NMR, cross-linking mass spectrometry, and cell models to design tau sequences that stabilize its structural ensemble. Our findings reveal that substitutions near the conserved 'PGGG' beta-turn motif can modulate local conformation, more stably engaging in interactions with the 306 VQIVYK 311 amyloid motif to decrease aggregation in vitro and in cells. Designed tau sequences maintain microtubule binding and explain why 3R isoforms of tau exhibit reduced pathogenesis over 4R isoforms. We propose a simple mechanism to reduce the formation of pathogenic species while preserving biological function, offering insights for therapeutic strategies aimed at reducing protein misfolding in neurodegenerative diseases.
    DOI:  https://doi.org/10.21203/rs.3.rs-3796916/v1
  3. Bioorg Med Chem. 2024 Jan 28. pii: S0968-0896(24)00027-0. [Epub ahead of print]100 117613
    Discovery of small molecule benzothiazole and indole derivatives tackling tau 2N4R and α-synuclein fibrils.
    Ahmed A Elbatrawy, Taiwo A Ademoye, Heba Alnakhala, Arati Tripathi, Ashique Zami, Raluca Ostafe, Ulf Dettmer, Jessica S Fortin.
      Tau and α-synuclein aggregates are the main histopathological hallmarks present in Alzheimer's disease (AD), Parkinson's disease (PD), and other neurodegenerative disorders. Intraneuronal hyperphosphorylated tau accumulation is significantly connected to the degree of cognitive impairment in AD patients. In particular, the longest 2N4R tau isoform has a propensity to rapidly form oligomers and mature fibrils. On the other hand, misfolding of α-synuclein (α-syn) is the characteristic feature in PD and dementia with Lewy bodies (DLB). There is a strong crosstalk between the two prone-to-aggregation proteins as they coprecipitated in some brains of AD, PD, and DLB patients. Simultaneous targeting of both proteinaceous oligomers and aggregates is still challenging. Here, we rationally designed and synthesized benzothiazole- and indole-based compounds using the structural hybridization strategy between the benzothiazole N744 cyanine dye and the diphenyl pyrazole Anle138b that showed anti-aggregation activity towards 2N4R tau and α-syn, respectively. The anti-aggregation effect of the prepared compounds was monitored using the thioflavin-T (ThT) fluorescence assay, while transmission electron microscopy (TEM) was employed to detect fibrils upon the completion of a time-course study with the ThT assay. Moreover, the photo-induced crosslinking of unmodified protein (PICUP) assay was used to determine the formation of oligomers. Specifically, compounds 46 and 48 demonstrated the highest anti-aggregation activity by decreasing the ThT fluorescence to 4.0 and 14.8%, respectively, against α-syn. Although no noticeable effect on 2N4R tau oligomers, 46 showed promising anti-oligomer activity against α-syn. Both compounds induced a significantly high anti-aggregation effect against the two protein fibrils as visualized by TEM. Moreover, compound 48 remarkably inhibited α-syn inclusion and cell confluence using M17D cells. Collectively, compounds 46 and 48 could serve as a basic structure for further optimization to develop clinically active AD and PD disease-modifying agents.
    Keywords:  Alpha-synuclein; Alzheimer’s disease; Anti-oligomer agents; Parkinson’s disease; Tau isoforms
    DOI:  https://doi.org/10.1016/j.bmc.2024.117613
  4. Int J Mol Sci. 2024 Jan 30. pii: 1672. [Epub ahead of print]25(3):
    Aquaporin-4 and Parkinson's Disease.
    Ksenia V Lapshina, Irina V Ekimova.
      The water-selective channel aquaporin-4 (AQP4) is implicated in water homeostasis and the functioning of the glymphatic system, which eliminates various metabolites from the brain tissue, including amyloidogenic proteins. Misfolding of the α-synuclein protein and its post-translational modifications play a crucial role in the development of Parkinson's disease (PD) and other synucleopathies, leading to the formation of cytotoxic oligomers and aggregates that cause neurodegeneration. Human and animal studies have shown an interconnection between AQP4 dysfunction and α-synuclein accumulation; however, the specific role of AQP4 in these mechanisms remains unclear. This review summarizes the current knowledge on the role of AQP4 dysfunction in the progression of α-synuclein pathology, considering the possible effects of AQP4 dysregulation on brain molecular mechanisms that can impact α-synuclein modification, accumulation and aggregation. It also highlights future directions that can help study the role of AQP4 in the functioning of the protective mechanisms of the brain during the development of PD and other neurodegenerative diseases.
    Keywords:  Parkinson’s disease; aquaporin-4; drug target; glymphatic system; neurodegeneration; pathophysiology; α-synuclein
    DOI:  https://doi.org/10.3390/ijms25031672
  5. bioRxiv. 2024 Jan 24. pii: 2024.01.23.576837. [Epub ahead of print]
    Intra-condensate demixing of TDP-43 inside stress granules generates pathological aggregates.
    Xiao Yan, David Kuster, Priyesh Mohanty, Jik Nijssen, Karina Pombo-García, Azamat Rizuan, Titus M Franzmann, Aleksandra Sergeeva, Patricia M Passos, Leah George, Szu-Huan Wang, Jayakrishna Shenoy, Helen L Danielson, Alf Honigmann, Yuna M Ayala, Nicolas L Fawzi, Jeetain Mittal, Simon Alberti, Anthony A Hyman.
      Cytosolic aggregation of the nuclear protein TDP-43 is associated with many neurodegenerative diseases, but the triggers for TDP-43 aggregation are still debated. Here, we demonstrate that TDP-43 aggregation requires a double event. One is up-concentration in stress granules beyond a threshold, and the other is oxidative stress. These two events collectively induce intra-condensate demixing, giving rise to a dynamic TDP-43 enriched phase within stress granules, which subsequently transitions into pathological aggregates. Mechanistically, intra-condensate demixing is triggered by local unfolding of the RRM1 domain for intermolecular disulfide bond formation and by increased hydrophobic patch interactions in the C-terminal domain. By engineering TDP-43 variants resistant to intra-condensate demixing, we successfully eliminate pathological TDP-43 aggregates in cells. We conclude that up-concentration inside condensates and simultaneous exposure to environmental stress could be a general pathway for protein aggregation, with intra-condensate demixing constituting a key intermediate step.
    DOI:  https://doi.org/10.1101/2024.01.23.576837
  6. J Biol Chem. 2024 Jan 10. pii: S0021-9258(24)00004-8. [Epub ahead of print]300(2): 105628
    C9orf72-associated dipeptide protein repeats form A11-positive oligomers in amyotrophic lateral sclerosis and frontotemporal dementia.
    Nemil Bhatt, Nicha Puangmalai, Urmi Sengupta, Cynthia Jerez, Madison Kidd, Shailee Gandhi, Rakez Kayed.
      Hexanucleotide repeat expansion in C9orf72 is one of the most common causes of amyotrophic lateral sclerosis and frontotemporal dementia. The hexanucleotide expansion, formed by GGGGCC (G4C2) repeats, leads to the production of five dipeptide protein repeats (DPRs) via repeat-associated non-AUG translation. Among the five dipeptide repeats, Gly-Arg, Pro-Arg, and Gly-Ala form neuronal inclusions that contain aggregates of the peptides. Several studies have attempted to model DPR-associated toxicity using various repeat lengths, which suggests a unique conformation that is cytotoxic and is independent of the repeat length. However, the structural characteristics of DPR aggregates have yet to be determined. Increasing evidence suggests that soluble species, such as oligomers, are the main cause of toxicity in proteinopathies, such as Alzheimer's and Parkinson's disease. To investigate the ability of DPRs to aggregate and form toxic oligomers, we adopted a reductionist approach using small dipeptide repeats of 3, 6, and 12. This study shows that DPRs, particularly glycine-arginine and proline-arginine, form oligomers that exhibit distinct dye-binding properties and morphologies. Importantly, we also identified toxic DPR oligomers in amyotrophic lateral sclerosis and frontotemporal dementia postmortem brains that are morphologically similar to those generated recombinantly. This study demonstrates that, similar to soluble oligomers formed by various amyloid proteins, DPR oligomers are toxic, independent of their repeat length.
    Keywords:  ALS; C9orf72; FTD; amyloids; dipeptide protein repeats; neurodegeneration
    DOI:  https://doi.org/10.1016/j.jbc.2024.105628
  7. J Biomol Struct Dyn. 2024 Feb 07. 1-13
    Computational investigation on the conformational dynamics of C-terminal truncated α-synuclein bound to membrane.
    Dorothy Das, Venkata Satish Kumar Mattaparthi.
      Accelerated progression rates in Parkinson's disease (PD) have been linked to C-terminal domain (CTD) truncations of monomeric α-Synuclein (α-Syn), which have been suggested to increase amyloid aggregation in vivo and in vitro. In the brain of PD patients, CTD truncated α-Syn was found to have lower cell viability and tends to increase in the formation of fibrils. The CTD of α-Syn acts as a guard for regulating the normal functioning of α-Syn. The absence of the CTD may allow the N-terminal of α-Syn to interact with the membrane thereby affecting the normal functioning of α-Syn, and all of which will affect the etiology of PD. In this study, the conformational dynamics of CTD truncated α-Syn (1-99 and 1-108) monomers and their effect on the protein-membrane interactions were demonstrated using the all-atom molecular dynamics (MD) simulation method. From the MD analyses, it was noticed that among the two truncated monomers, α-Syn (1-108) was found to be more stable, shows rigidness at the N-terminal region and contains a significant number of intermolecular hydrogen bonds between the non-amyloid β-component (NAC) region and membrane, and lesser number of extended strands. Further, the bending angle in the N-terminal domain was found to be lesser in the α-Syn (1-108) in comparison with the α-Syn (1-99). Our findings suggest that the truncation on the CTD of α-Syn affects its interaction with the membrane and subsequently has an impact on the aggregation.Communicated by Ramaswamy H. Sarma.
    Keywords:  aggregation; membrane dynamics; molecular dynamics simulation; truncation; α-Synuclein
    DOI:  https://doi.org/10.1080/07391102.2024.2310788
  8. Biophys Chem. 2024 Jan 02. pii: S0301-4622(23)00216-8. [Epub ahead of print]307 107165
    A label-free high-throughput protein solubility assay and its application to Aβ40.
    Max Lindberg, Emil Axell, Emma Sparr, Sara Linse.
      A major hallmark of Alzheimer's disease is the accumulation of aggregated amyloid β peptide (Aβ) in the brain. Here we develop a solubility assay for proteins and measure the solubility of Aβ40. In brief, the method utilizes 96-well filter plates to separate monomeric Aβ from aggregated Aβ, and the small species are quantified with the amine reactive dye o-phthalaldehyde (OPA). This procedure ensures that solubility is measured for unlabeled species, and makes the assay high-throughput and inexpensive. We demonstrate that the filter plates successfully separate fibrils from monomer, with negligible monomer adsorption, and that OPA can quantify Aβ peptides in a concentration range from 40 nM to 20 μM. We also show that adding a methionine residue to the N-terminus of Aβ1-40 decreases the solubility by <3-fold. The method will facilitate further solubility studies, and contribute to the understanding of the thermodynamics of amyloid fibril formation.
    Keywords:  Abeta; Amyloid beta; Critical aggregation concentration; Equilibrium; Method development; Self-assembly
    DOI:  https://doi.org/10.1016/j.bpc.2023.107165
  9. J Biol Chem. 2024 Feb 02. pii: S0021-9258(24)00092-9. [Epub ahead of print] 105716
    RNA and the RNA-binding protein FUS act in concert to prevent TDP-43 spatial segregation.
    Clément Demongin, Samuel Tranier, Vandana Joshi, Léa Ceschi, Bénédicte Desforges, David Pastré, Loic Hamon.
      FUS and TDP-43 are two self-adhesive aggregation-prone mRNA-binding proteins whose pathological mutations have been linked to neurodegeneration. While TDP-43 and FUS form reversible mRNA-rich compartments in the nucleus, pathological mutations promote their respective cytoplasmic aggregation in neurons with no apparent link between the two proteins except their intertwined function in mRNA processing. By combining analyses in cellular context and at high-resolution in vitro, we unraveled that TDP-43 is specifically recruited in FUS assemblies to form TDP-43 rich sub-compartments but without reciprocity. The presence of mRNA provides an additional scaffold to promote the mixing between TDP-43 and FUS. Accordingly, we also found that the pathological truncated form of TDP-43, TDP-25, which has an impaired RNA binding ability, no longer mixes with FUS. Together, these results suggest that the binding of FUS along nascent mRNAs enables TDP-43, which is highly aggregation-prone, to mix with FUS phase to form mRNA-rich sub-compartments. A functional link between FUS and TDP-43 may explain their common implication in Amyotrophic Lateral Sclerosis (ALS).
    DOI:  https://doi.org/10.1016/j.jbc.2024.105716
  10. Int J Mol Sci. 2024 Feb 01. pii: 1787. [Epub ahead of print]25(3):
    Secondary Modification of S100B Influences Anti Amyloid-β Aggregation Activity and Alzheimer's Disease Pathology.
    Romina Coelho, Chiara A De Benedictis, Ann Katrin Sauer, António J Figueira, Hélio Faustino, Andreas M Grabrucker, Cláudio M Gomes.
      Proteinaceous aggregates accumulate in neurodegenerative diseases such as Alzheimer's Disease (AD), inducing cellular defense mechanisms and altering the redox status. S100 pro-inflammatory cytokines, particularly S100B, are activated during AD, but recent findings reveal an unconventional molecular chaperone role for S100B in hindering Aβ aggregation and toxicity. This suggests a potential protective role for S100B at the onset of Aβ proteotoxicity, occurring in a complex biochemical environment prone to oxidative damage. Herein, we report an investigation in which extracellular oxidative conditions are mimicked to test if the susceptibility of S100B to oxidation influences its protective activities. Resorting to mild oxidation of S100B, we observed methionine oxidation as inferred from mass spectrometry, but no cysteine-mediated crosslinking. Structural analysis showed that the folding, structure, and stability of oxidized S100B were not affected, and nor was its quaternary structure. However, studies on Aβ aggregation kinetics indicated that oxidized S100B was more effective in preventing aggregation, potentially linked to the oxidation of Met residues within the S100:Aβ binding cleft that favors interactions. Using a cell culture model to analyze the S100B functions in a highly oxidative milieu, as in AD, we observed that Aβ toxicity is rescued by the co-administration of oxidized S100B to a greater extent than by S100B. Additionally, results suggest a disrupted positive feedback loop involving S100B which is caused by its oxidation, leading to the downstream regulation of IL-17 and IFN-α2 expression as mediated by S100B.
    Keywords:  Alzheimer’s; S100 proteins; amyloid beta; cytokine; molecular chaperones; neurodegeneration; neuroinflammation; oxidation
    DOI:  https://doi.org/10.3390/ijms25031787
  11. Int J Mol Sci. 2024 Jan 29. pii: 1636. [Epub ahead of print]25(3):
    The Inhibition Effect of Epigallocatechin-3-Gallate on the Co-Aggregation of Amyloid-β and Human Islet Amyloid Polypeptide Revealed by Replica Exchange Molecular Dynamics Simulations.
    Xuhua Li, Yu Zhang, Zhiwei Yang, Shengli Zhang, Lei Zhang.
      Alzheimer's disease and Type 2 diabetes are two epidemiologically linked diseases which are closely associated with the misfolding and aggregation of amyloid proteins amyloid-β (Aβ) and human islet amyloid polypeptide (hIAPP), respectively. The co-aggregation of the two amyloid proteins is regarded as the fundamental molecular mechanism underlying their pathological association. The green tea extract epigallocatechin-3-gallate (EGCG) has been extensively demonstrated to inhibit the amyloid aggregation of Aβ and hIAPP proteins. However, its potential role in amyloid co-aggregation has not been thoroughly investigated. In this study, we employed the enhanced-sampling replica exchange molecular dynamics simulation (REMD) method to investigate the effect of EGCG on the co-aggregation of Aβ and hIAPP. We found that EGCG molecules substantially diminish the β-sheet structures within the amyloid core regions of Aβ and hIAPP in their co-aggregates. Through hydrogen-bond, π-π and cation-π interactions targeting polar and aromatic residues of Aβ and hIAPP, EGCG effectively attenuates both inter-chain and intra-chain interactions within the co-aggregates. All these findings indicated that EGCG can effectively inhibit the co-aggregation of Aβ and hIAPP. Our study expands the potential applications of EGCG as an anti-amyloidosis agent and provides therapeutic options for the pathological association of amyloid misfolding disorders.
    Keywords:  amyloid-β; co-aggregation; epigallocatechin-3-gallate; human islet amyloid polypeptide; replica exchange molecular dynamics simulation
    DOI:  https://doi.org/10.3390/ijms25031636
  12. J Biol Chem. 2024 Feb 02. pii: S0021-9258(24)00095-4. [Epub ahead of print] 105719
    RACK1 and IRE1 participate in the translational quality control of amyloid precursor protein in Drosophila models of Alzheimer's disease.
    Yu Li, Dongyue Liu, Xuejing Zhang, Suman Rimal, Bingwei Lu, Shuangxi Li.
      Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by dysregulation of the expression and processing of the amyloid precursor protein (APP). Protein quality control systems are dedicated to remove faulty and deleterious proteins to maintain cellular protein homeostasis (proteostasis). Identidying mechanisms underlying APP protein regulation is crucial for understanding AD pathogenesis. However, the factors and associated molecular mechanisms regulating APP protein quality control remain poorly defined. In this study, we show that mutant APP with its mitochondrial-targeting sequence ablated exhibited predominant endoplasmic reticulum (ER) distribution and led to aberrant ER morphology, deficits in locomotor activity, and shortened lifespan. We searched for regulators that could counteract the toxicity caused by the ectopic expression of this mutant APP. Genetic removal of the ribosome-associated quality control (RQC) factor RACK1 resulted in reduced levels of ectopically expressed mutant APP. By contrast, gain of RACK1 function increased mutant APP level. Additionally, overexpression of the ER stress regulator (IRE1) resulted in reduced levels of ectopically expressed mutant APP. Mechanistically, the RQC related ATPase VCP/p97 and the E3 ubiquitin ligase Hrd1 were required for the reduction of mutant APP level by IRE1. These factors also regulated the expression and toxicity of ectopically expressed wild type APP, supporting their relevance to APP biology. Our results reveal functions of RACK1 and IRE1 in regulating the quality control of APP homeostasis and mitigating its pathogenic effects, with implications for the understanding and treatment of AD.
    Keywords:  Drosophila; ER; IRE1; Proteostasis; RACK1; amyloid precursor protein (APP); ribosome-associated quality control (RQC)
    DOI:  https://doi.org/10.1016/j.jbc.2024.105719
  13. bioRxiv. 2024 Jan 22. pii: 2024.01.22.576709. [Epub ahead of print]
    TDP-43 dysregulation of polyadenylation site selection is a defining feature of RNA misprocessing in ALS/FTD and related disorders.
    Frederick J Arnold, Ya Cui, Sebastian Michels, Michael R Colwin, Cameron Stockford, Wenbin Ye, Oliver H Tam, Sneha Menon, Wendy G Situ, Kean C K Ehsani, Sierra Howard, Molly Gale Hammell, Wei Li, Albert R La Spada.
      Nuclear clearance and cytoplasmic aggregation of the RNA-binding protein TDP-43 are observed in many neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and fronto- temporal dementia (FTD). Although TDP-43 dysregulation of splicing has emerged as a key event in these diseases, TDP-43 can also regulate polyadenylation; yet, this has not been adequately studied. Here, we applied the dynamic analysis of polyadenylation from RNA-seq (DaPars) tool to ALS/FTD transcriptome datasets, and report extensive alternative polyadenylation (APA) upon TDP-43 alteration in ALS/FTD cell models and postmortem ALS/FTD neuronal nuclei. Importantly, many identified APA genes highlight pathways implicated in ALS/FTD pathogenesis. To determine the functional significance of APA elicited by TDP-43 nuclear depletion, we examined microtubule affinity regulating kinase 3 (MARK3). Nuclear loss of TDP-43 yielded increased expression of MARK3 transcripts with longer 3'UTRs, resulting in greater transcript stability and elevated MARK3 protein levels, which promotes increased neuronal tau S262 phosphorylation. Our findings define changes in polyadenylation site selection as a previously unrecognized feature of TDP-43-driven disease pathology in ALS/FTD and highlight a potentially novel mechanistic link between TDP-43 dysfunction and tau regulation.
    DOI:  https://doi.org/10.1101/2024.01.22.576709
  14. Int J Biol Macromol. 2024 Feb 05. pii: S0141-8130(24)00756-6. [Epub ahead of print] 129953
    Crosstalk between tau protein autoproteolysis and amyloid fibril formation.
    Mohammad Reza Ashrafi-Kooshk, Fatemeh Norouzi, Ashkan Zare Karizak, Shahin Ahmadian, Ali Akabar Moosavi-Movahedi, Gholamhossein Riazi.
      Tau cleavage has been shown to have a significant effect on protein aggregation. Tau truncation results in the formation of aggregation-prone fragments leading to toxic aggregates and also causes the formation of harmful fragments that do not aggregate. Thus, targeting proteolysis of tau would be beneficial for the development of therapeutics for Alzheimer's disease and related tauopathies. In this study, amino-terminal quantification and ThT fluorimetry were respectively used to analyze the kinetics of tau fragmentation and fibril formation. SDS-PAGE analysis of tau protein incubated with a disulfide-reducing agent demonstrated that the cysteines of tau have a crucial role in the fibrillation and autoproteolysis. However, the structures converted to amyloid fibrils were different with conformations that led to autoproteolysis. The quantification of the amino terminal indicated that the double-disulfide parallel structures formed in the presence of heparin did not have protease activity. The survey of possible tau disulfide-mediated dimer configurations suggested that the non-register single disulfide bound conformations were involved in the tau autoproteolysis process. Moreover, the inhibition of autoproteolysis resulted in the increment of aggregation rate; hence it seems that the tau auto-cleavage is the cellular defense mechanism against protein fibrillation.
    Keywords:  Amyloid; Autoproteolysis; Tau
    DOI:  https://doi.org/10.1016/j.ijbiomac.2024.129953
  15. Acta Neuropathol Commun. 2024 Feb 04. 12(1): 20
    Dysregulation of stress granule dynamics by DCTN1 deficiency exacerbates TDP-43 pathology in Drosophila models of ALS/FTD.
    Tetsuhiro Ueda, Toshihide Takeuchi, Nobuhiro Fujikake, Mari Suzuki, Eiko N Minakawa, Morio Ueyama, Yuzo Fujino, Nobuyuki Kimura, Seiichi Nagano, Akio Yokoseki, Osamu Onodera, Hideki Mochizuki, Toshiki Mizuno, Keiji Wada, Yoshitaka Nagai.
      The abnormal aggregation of TDP-43 into cytoplasmic inclusions in affected neurons is a major pathological hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Although TDP-43 is aberrantly accumulated in the neurons of most patients with sporadic ALS/FTD and other TDP-43 proteinopathies, how TDP-43 forms cytoplasmic aggregates remains unknown. In this study, we show that a deficiency in DCTN1, a subunit of the microtubule-associated motor protein complex dynactin, perturbs the dynamics of stress granules and drives the formation of TDP-43 cytoplasmic aggregation in cultured cells, leading to the exacerbation of TDP-43 pathology and neurodegeneration in vivo. We demonstrated using a Drosophila model of ALS/FTD that genetic knockdown of DCTN1 accelerates the formation of ubiquitin-positive cytoplasmic inclusions of TDP-43. Knockdown of components of other microtubule-associated motor protein complexes, including dynein and kinesin, also increased the formation of TDP-43 inclusions, indicating that intracellular transport along microtubules plays a key role in TDP-43 pathology. Notably, DCTN1 knockdown delayed the disassembly of stress granules in stressed cells, leading to an increase in the formation of pathological cytoplasmic inclusions of TDP-43. Our results indicate that a deficiency in DCTN1, as well as disruption of intracellular transport along microtubules, is a modifier that drives the formation of TDP-43 pathology through the dysregulation of stress granule dynamics.
    Keywords:  Aggregation; DCTN1; Microtubule-dependent transport; Stress granule; TDP-43
    DOI:  https://doi.org/10.1186/s40478-024-01729-8
  16. iScience. 2024 Feb 16. 27(2): 108893
    Lysosomal stress drives the release of pathogenic α-synuclein from macrophage lineage cells via the LRRK2-Rab10 pathway.
    Tetsuro Abe, Tomoki Kuwahara, Shoichi Suenaga, Maria Sakurai, Sho Takatori, Takeshi Iwatsubo.
      α-Synuclein and LRRK2 are associated with both familial and sporadic Parkinson's disease (PD), although the mechanistic link between these two proteins has remained elusive. Treating cells with lysosomotropic drugs causes the recruitment of LRRK2 and its substrate Rab10 onto overloaded lysosomes and induces extracellular release of lysosomal contents. Here we show that lysosomal overload elicits the release of insoluble α-synuclein from macrophages and microglia loaded with α-synuclein fibrils. This release occurred specifically in macrophage lineage cells, was dependent on the LRRK2-Rab10 pathway and involved exosomes. Also, the uptake of α-synuclein fibrils enhanced the LRRK2 phosphorylation of Rab10, which was accompanied by an increased recruitment of LRRK2 and Rab10 onto lysosomal surface. Our data collectively suggest that α-synuclein fibrils taken up in lysosomes activate the LRRK2-Rab10 pathway, which in turn upregulates the extracellular release of α-synuclein aggregates, leading to a vicious cycle that could enhance α-synuclein propagation in PD pathology.
    Keywords:  Cell biology; Molecular biology
    DOI:  https://doi.org/10.1016/j.isci.2024.108893
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