bims-proned 2024-06-16 papers

bims-proned

Biomed News

on Proteostasis in neurodegeneration

Issue of 2024–06–16
fiveteen papers selected by
Verena Kohler, Umeå University

Protein aggregation and therapeutic strategies in SOD1- and TDP-43- linked ALS.
5-Phenyl valeric acid attenuates α-synuclein aggregation and endoplasmic reticulum stress in rotenone-induced Parkinson's disease rats: A molecular mechanistic study.
[Mechanisms Underlying the Propagation of α-Synuclein Seeds Derived from the Blood of Patients with α-Synucleinopathies].
Modeling Parkinson's Disease in Primates.
Single-molecule characterization of salivary protein aggregates from Parkinson's disease patients: a pilot study.
Native State Stabilization of Amyloidogenic Proteins by Kinetic Stabilizers: Inhibition of Protein Aggregation and Clinical Relevance.
A Review of the Protective Effects of Alkaloids Against Alpha-synuclein toxicity in Parkinson's disease.
Frontotemporal dementia-like disease progression elicited by seeded aggregation and spread of FUS.
The role of shear forces in primary and secondary nucleation of amyloid fibrils.
Fully Human Bifunctional Intrabodies Achieve Graded Reduction of Intracellular Tau and Rescue Survival of MAPT Mutation iPSC-derived Neurons.
Protein Disulfide Isomerase Endoplasmic Reticulum Protein 57 (ERp57) is Protective Against ALS-Associated Mutant TDP-43 in Neuronal Cells.
Elucidating the Molecular Basis of 14-3-3 Interaction with α-Synuclein: Insights from Molecular Dynamics Simulations and the Design of a Novel Protein-Protein Interaction Inhibitor.
Tau fibrils evade autophagy by excessive p62 coating and TAX1BP1 exclusion.
Human tNeurons reveal aging-linked proteostasis deficits driving Alzheimer's phenotypes.
Altered Autophagic Flux in GNE mutant cells of Indian Origin: potential drug target for GNE Myopathy.

Front Mol Biosci. 2024 ;11 1383453

Protein aggregation and therapeutic strategies in SOD1- and TDP-43- linked ALS.

Maria Tsekrekou, Maria Giannakou, Katerina Papanikolopoulou, Georgios Skretas.

  Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with severe socio-economic impact. A hallmark of ALS pathology is the presence of aberrant cytoplasmic inclusions composed of misfolded and aggregated proteins, including both wild-type and mutant forms. This review highlights the critical role of misfolded protein species in ALS pathogenesis, particularly focusing on Cu/Zn superoxide dismutase (SOD1) and TAR DNA-binding protein 43 (TDP-43), and emphasizes the urgent need for innovative therapeutic strategies targeting these misfolded proteins directly. Despite significant advancements in understanding ALS mechanisms, the disease remains incurable, with current treatments offering limited clinical benefits. Through a comprehensive analysis, the review focuses on the direct modulation of the misfolded proteins and presents recent discoveries in small molecules and peptides that inhibit SOD1 and TDP-43 aggregation, underscoring their potential as effective treatments to modify disease progression and improve clinical outcomes.

Keywords:  SOD1; TDP-43; amyotrophic lateral sclerosis; neurotoxicity; protein aggregation; protein misfolding; therapeutics

DOI:  https://doi.org/10.3389/fmolb.2024.1383453
Biochem Pharmacol. 2024 Jun 07. pii: S0006-2952(24)00326-5. [Epub ahead of print] 116343

5-Phenyl valeric acid attenuates α-synuclein aggregation and endoplasmic reticulum stress in rotenone-induced Parkinson's disease rats: A molecular mechanistic study.

Navpreet Kaur, Rimaljot Singh, Neelima Dhingra, Tanzeer Kaur.

  The abnormal accumulation of fibrillar α-synuclein in the substantia nigra contributes to Parkinson's disease (PD). Chemical chaperones like 4-phenyl butyric acid (4PBA) show neuroprotective potential, but high doses are required. A derivative, 5-phenyl valeric acid (5PVA), has reported therapeutic potential for PD by reducing Pael-R expression. This study assessed 5PVA's efficacy in PD animals and its molecular mechanism. In vitro studies revealed 5PVA's anti-aggregation ability against alpha-synuclein and neuroprotective effects on SHSY5Y neuroblastoma cells exposed to rotenone. PD-like symptoms were induced in SD rats with rotenone, followed by 5PVA treatment at 100 mg/kg and 130 mg/kg. Behavioral analysis showed significant improvement in memory and motor activity with 5PVA administration. Histopathological studies demonstrated normal neuronal histoarchitecture in mid-brain tissue sections of 5PVA-treated animals compared to the PD group. mRNA studies revealed significant suppression in the expression of various protein folding and heat-shock protein markers in the 5PVA-treated group. In conclusion, 5PVA, with its anti-aggregation ability against alpha-synuclein, acts as a chemical chaperone, showing potential as a therapeutic candidate for PD treatment.

Keywords:  5-Phenyl valeric acid; Chemical chaperone; Endoplasmic reticulum stress; Parkinson’s disease; α-synuclein aggregation

DOI:  https://doi.org/10.1016/j.bcp.2024.116343
Brain Nerve. 2024 Jun;76(6): 767-772

[Mechanisms Underlying the Propagation of α-Synuclein Seeds Derived from the Blood of Patients with α-Synucleinopathies].

Ayami Okuzumi, Taku Hatano, Nobutaka Hattori.

The aggregation of α-synuclein (α-syn), associated with Parkinson's disease (PD) extends from the peripheral autonomic nervous system to the cerebral cortex, indicating a neural circuit-based mechanism of spread. However, recent studies, have proposed alternative propagation routes beyond neural pathways, including transmission via bodily fluids, such as the blood. This notion expands our understanding of PD progression, underscoring the complexity of α-syn spread and its implications in disease management and therapeutic strategies.

DOI: https://doi.org/10.11477/mf.1416202676
Cold Spring Harb Perspect Med. 2024 Jun 10. pii: a041612. [Epub ahead of print]

Modeling Parkinson's Disease in Primates.

Erwan Bezard, Margaux Teil, Marie-Laure Arotcarena, Gregory Porras, Qin Li, Benjamin Dehay.

Decades of research have identified the pathological and pathophysiological hallmarks of Parkinson's disease (PD): profound deficit in brain dopamine and other monoamines, pathological α-synuclein aggregation, synaptic and neuronal network dysfunction, aberrant proteostasis, altered energy homeostasis, inﬂammation, and neuronal cell death. The purpose of this contribution is to present the phenocopy aspect, pathogenic, and etiologic nonhuman primate (NHP) models of PD to readers with limited prior knowledge of PD so that they are ready to start working on PD. How NHPs, the closest species to man on which we can model diseases, contribute to the knowledge progress and how these models represent an invaluable translational step in therapeutic development are highlighted.

DOI: https://doi.org/10.1101/cshperspect.a041612
Brain Commun. 2024 ;6(3): fcae178

Single-molecule characterization of salivary protein aggregates from Parkinson's disease patients: a pilot study.

Martin Furlepa, Yu P Zhang, Evgeniia Lobanova, Lakmini Kahanawita, Giorgio Vivacqua, Caroline H Williams-Gray, David Klenerman.

  Saliva is a convenient and accessible biofluid that has potential as a future diagnostic tool for Parkinson's disease. Candidate diagnostic tests for Parkinson's disease to date have predominantly focused on measurements of α-synuclein in CSF, but there is a need for accurate tests utilizing more easily accessible sample types. Prior studies utilizing saliva have used bulk measurements of salivary α-synuclein to provide diagnostic insight. Aggregate structure may influence the contribution of α-synuclein to disease pathology. Single-molecule approaches can characterize the structure of individual aggregates present in the biofluid and may, therefore, provide greater insight than bulk measurements. We have employed an antibody-based single-molecule pulldown assay to quantify salivary α-synuclein and amyloid-β peptide aggregate numbers and subsequently super-resolved captured aggregates using direct Stochastic Optical Reconstruction Microscopy to describe their morphological features. We show that the salivary α-synuclein aggregate/amyloid-β aggregate ratio is increased almost 2-fold in patients with Parkinson's disease (n = 20) compared with controls (n = 20, P < 0.05). Morphological information also provides insight, with saliva from patients with Parkinson's disease containing a greater proportion of larger and more fibrillar amyloid-β aggregates than control saliva (P < 0.05). Furthermore, the combination of count and morphology data provides greater diagnostic value than either measure alone, distinguishing between patients with Parkinson's disease (n = 17) and controls (n = 18) with a high degree of accuracy (area under the curve = 0.87, P < 0.001) and a larger dynamic range. We, therefore, demonstrate for the first time the application of highly sensitive single-molecule imaging techniques to saliva. In addition, we show that aggregates present within saliva retain relevant structural information, further expanding the potential utility of saliva-based diagnostic methods.

Keywords:  Parkinson’s disease; amyloid-β; saliva; single-molecule imaging; α-synuclein

DOI:  https://doi.org/10.1093/braincomms/fcae178
ChemMedChem. 2024 Jun 11. e202400244

Native State Stabilization of Amyloidogenic Proteins by Kinetic Stabilizers: Inhibition of Protein Aggregation and Clinical Relevance.

Priyanka Xx, Bitta Raymandal, Santanu Mondal.

  Proteinopathies or amyloidoses are a group of life-threatening disorders that result from misfolding of proteins and aggregation into toxic insoluble amyloid aggregates. Amyloid aggregates have low clearance from the body due to the insoluble nature, leading to their deposition in various organs and consequent organ dysfunction. While amyloid deposition in the central nervous system leads to neurodegenerative diseases that mostly cause dementia and difficulty in movement, several other organs, including heart, liver and kidney are also affected by systemic amyloidoses. Regardless of the site of amyloid deposition, misfolding and structural alteration of the precursor proteins play the central role in amyloid formation. Kinetic stabilizers are an emerging class of drugs, which act like pharmacological chaperones to stabilize the native state structure of amyloidogenic proteins and to increase the activation energy barrier that is required for adopting a misfolded structure or conformation, ultimately leading to the inhibition of protein aggregation. In this review, we discuss the kinetic stabilizers that stabilize the native quaternary structure of transthyretin, immunoglobulin light chain and superoxide dismutase 1 that cause transthyretin amyloidoses, light chain amyloidosis and familial amyotrophic lateral sclerosis, respectively.

Keywords:  Immunoglobulin light chain, Kinetic stabilizers, Protein aggregation, Superoxide dismutase, Transthyretin

DOI:  https://doi.org/10.1002/cmdc.202400244
Mini Rev Med Chem. 2024 Jun 13.

A Review of the Protective Effects of Alkaloids Against Alpha-synuclein toxicity in Parkinson's disease.

Behjat Javadi, Mahdi Khodadadi.

   BACKGROUND: Alpha-synuclein (α-syn) aggregation products may cause neural injury and several neurodegenerative disorders (NDs) known as α-synucleinopathies. Alkaloids are secondary metabolites present in a variety of plant species and may positively affect human health, particularly α-synucleinopathy-associated NDs.
AIM: To summarize the latest scientific data on the inhibitory properties of alkaloids in α- synucleinopathies, especially in Parkinson's disease.
METHODS: Literature search was performed using web-based databases including Web of Science, PubMed, and Scopus up to January 2024, in the English language.
RESULTS: Harmala alkaloids, caffein, lycorine, piperin, acetylcorynoline, berberin, papaverine, squalamine, trodusquemine and nicotin have been found to be the most active natural alkaloids against synucleinopathy. The underlying mechanisms that contribute to this effect would be the inhibition of α-syn aggregation; elimination of formed aggregates; improvement in autophagy activation; promotion of the activity and expression of antioxidative enzymes; and prevention of oxidative injury and apoptosis in dopaminergic neurons.
CONCLUSION: The findings of the present study highlight the inhibitory activities of alkaloids against synucleinopathy. However, no clinical data supports the reported activities in humans, which calls attention to the need for conducting clinical trials to elucidate the efficacy, safety, proper dosage, unwanted effects and pharmacokinetics aspects of alkaloids in humans.

Keywords:  Synuclein; alkaloids; neurodegeneration; parkinson’s disease; plants.

DOI:  https://doi.org/10.2174/0113895575306884240604065754
Mol Neurodegener. 2024 Jun 11. 19(1): 46

Frontotemporal dementia-like disease progression elicited by seeded aggregation and spread of FUS.

Sonia Vazquez-Sanchez, Britt Tilkin, Fatima Gasset-Rosa, Sitao Zhang, Diana Piol, Melissa McAlonis-Downes, Jonathan Artates, Noe Govea-Perez, Yana Verresen, Lin Guo, Don W Cleveland, James Shorter, Sandrine Da Cruz.

  RNA binding proteins have emerged as central players in the mechanisms of many neurodegenerative diseases. In particular, a proteinopathy of fused in sarcoma (FUS) is present in some instances of familial Amyotrophic lateral sclerosis (ALS) and about 10% of sporadic Frontotemporal lobar degeneration (FTLD). Here we establish that focal injection of sonicated human FUS fibrils into brains of mice in which ALS-linked mutant or wild-type human FUS replaces endogenous mouse FUS is sufficient to induce focal cytoplasmic mislocalization and aggregation of mutant and wild-type FUS which with time spreads to distal regions of the brain. Human FUS fibril-induced FUS aggregation in the mouse brain of humanized FUS mice is accelerated by an ALS-causing FUS mutant relative to wild-type human FUS. Injection of sonicated human FUS fibrils does not induce FUS aggregation and subsequent spreading after injection into naïve mouse brains containing only mouse FUS, indicating a species barrier to human FUS aggregation and its prion-like spread. Fibril-induced human FUS aggregates recapitulate pathological features of FTLD including increased detergent insolubility of FUS and TAF15 and amyloid-like, cytoplasmic deposits of FUS that accumulate ubiquitin and p62, but not TDP-43. Finally, injection of sonicated FUS fibrils is shown to exacerbate age-dependent cognitive and behavioral deficits from mutant human FUS expression. Thus, focal seeded aggregation of FUS and further propagation through prion-like spread elicits FUS-proteinopathy and FTLD-like disease progression.

Keywords:  Aggregation; Amyotrophic lateral sclerosis (ALS); FUS-proteinopathy; Frontotemporal lobar degeneration (FTLD); Spreading

DOI:  https://doi.org/10.1186/s13024-024-00737-5
Proc Natl Acad Sci U S A. 2024 Jun 18. 121(25): e2322572121

The role of shear forces in primary and secondary nucleation of amyloid fibrils.

Emil Axell, Jing Hu, Max Lindberg, Alexander J Dear, Lei Ortigosa-Pascual, Ewa A Andrzejewska, Greta Šneiderienė, Dev Thacker, Tuomas P J Knowles, Emma Sparr, Sara Linse.

  Shear forces affect self-assembly processes ranging from crystallization to fiber formation. Here, the effect of mild agitation on amyloid fibril formation was explored for four peptides and investigated in detail for A[Formula: see text]42, which is associated with Alzheimer's disease. To gain mechanistic insights into the effect of mild agitation, nonseeded and seeded aggregation reactions were set up at various peptide concentrations with and without an inhibitor. First, an effect on fibril fragmentation was excluded by comparing the monomer-concentration dependence of aggregation kinetics under idle and agitated conditions. Second, using a secondary nucleation inhibitor, Brichos, the agitation effect on primary nucleation was decoupled from secondary nucleation. Third, an effect on secondary nucleation was established in the absence of inhibitor. Fourth, an effect on elongation was excluded by comparing the seeding potency of fibrils formed under idle or agitated conditions. We find that both primary and secondary nucleation steps are accelerated by gentle agitation. The increased shear forces facilitate both the detachment of newly formed aggregates from catalytic surfaces and the rate at which molecules are transported in the bulk solution to encounter nucleation sites on the fibril and other surfaces. Ultrastructural evidence obtained with cryogenic transmission electron microscopy and free-flow electrophoresis in microfluidics devices imply that agitation speeds up the detachment of nucleated species from the fibril surface. Our findings shed light on the aggregation mechanism and the role of detachment for efficient secondary nucleation. The results inform on how to modulate the relative importance of different microscopic steps in drug discovery and investigations.

Keywords:  acceleration; aggregation; amyloid beta peptide; convection; double nucleation

DOI:  https://doi.org/10.1073/pnas.2322572121
bioRxiv. 2024 Jun 01. pii: 2024.05.28.596248. [Epub ahead of print]

Fully Human Bifunctional Intrabodies Achieve Graded Reduction of Intracellular Tau and Rescue Survival of MAPT Mutation iPSC-derived Neurons.

Lianna D'Brant, Natasha Rugenstein, Su Kyoung Na, Michael J Miller, Timothy F Czajka, Nicole Trudeau, Emily Fitz, Lindsay Tomaszek, Elizabeth S Fisher, Ethan Mash, Shona Joy, Steven Lotz, Susan Borden, Katherine Stevens, Susan K Goderie, Yue Wang, Taylor Bertucci, Celeste M Karch, Sally Temple, David C Butler.

Tau protein aggregation is a hallmark of several neurodegenerative diseases, including Alzheimer's disease, frontotemporal dementia (FTD) and progressive supranuclear palsy (PSP), spurring development of tau-lowering therapeutic strategies. Here, we report fully human bifunctional anti-tau-PEST intrabodies that bind the mid-domain of tau to block aggregation and degrade tau via the proteasome using the ornithine decarboxylase (ODC) PEST degron. They effectively reduced tau protein in human iPSC-derived cortical neurons in 2D cultures and 3D organoids, including those with the disease-associated tau mutations R5L, N279K, R406W, and V337M. Anti-tau-hPEST intrabodies facilitated efficient ubiquitin-independent proteolysis, in contrast to tau-lowering approaches that rely on the cell's ubiquitination system. Importantly, they counteracted the proteasome impairment observed in V337M patient-derived cortical neurons and significantly improved neuronal survival. By serial mutagenesis, we created variants of the PEST degron that achieved graded levels of tau reduction. Moderate reduction was as effective as high reduction against tau V337M-induced neural cell death.

DOI: https://doi.org/10.1101/2024.05.28.596248
Neuromolecular Med. 2024 Jun 11. 26(1): 23

Protein Disulfide Isomerase Endoplasmic Reticulum Protein 57 (ERp57) is Protective Against ALS-Associated Mutant TDP-43 in Neuronal Cells.

Sonam Parakh, Emma R Perri, Marta Vidal, Zeinab Takalloo, Cyril J Jagaraj, Prachi Mehta, Shu Yang, Colleen J Thomas, Ian P Blair, Yuning Hong, Julie D Atkin.

  Amyotrophic Lateral Sclerosis (ALS) is a severe neurodegenerative disease affecting motor neurons. Pathological forms of Tar-DNA binding protein-43 (TDP-43), involving its mislocalisation to the cytoplasm and the formation of misfolded inclusions, are present in almost all ALS cases (97%), and ~ 50% cases of the related condition, frontotemporal dementia (FTD), highlighting its importance in neurodegeneration. Previous studies have shown that endoplasmic reticulum protein 57 (ERp57), a member of the protein disulphide isomerase (PDI) family of redox chaperones, is protective against ALS-linked mutant superoxide dismutase (SOD1) in neuronal cells and transgenic SOD1G93A mouse models. However, it remains unclear whether ERp57 is protective against pathological TDP-43 in ALS. Here, we demonstrate that ERp57 is protective against key features of TDP-43 pathology in neuronal cells. ERp57 inhibited the mislocalisation of TDP-43M337V from the nucleus to the cytoplasm. In addition, ERp57 inhibited the number of inclusions formed by ALS-associated variant TDP-43M337V and reduced the size of these inclusions. ERp57 was also protective against ER stress and induction of apoptosis. Furthermore, ERp57 modulated the steady-state expression levels of TDP-43. This study therefore demonstrates a novel mechanism of action of ERp57 in ALS. It also implies that ERp57 may have potential as a novel therapeutic target to prevent the TDP-43 pathology associated with neurodegeneration.

Keywords:  ALS—Amyotrophic lateral sclerosis; ER stress; ERp57—Endoplasmic reticulum protein 57; PDI—Protein disulphide isomerase; TDP-43 pathology

DOI:  https://doi.org/10.1007/s12017-024-08787-0
J Phys Chem B. 2024 Jun 10.

Elucidating the Molecular Basis of 14-3-3 Interaction with α-Synuclein: Insights from Molecular Dynamics Simulations and the Design of a Novel Protein-Protein Interaction Inhibitor.

Gourav Chakraborty, Niladri Patra.

Parkinson's disease is a widespread age-related neurodegenerative disorder characterized by the loss of dopaminergic neurons in the midbrain along with the appearance of protein aggregates, termed as "Lewy bodies" in the surviving neuronal cells. The components of Lewy bodies include proteins such as α-synuclein, 14-3-3, Parkin, and LRRK2, along with other cellular organelles, which, in their native state, perform a plethora of vital biological functions within the human biome. Formation of these aggregates renders these components inactive, thereby interfering with homeostasis. In this regard, the current study attempts to investigate the complexation behavior of all human-based 14-3-3 isoforms with α-synuclein via a combination of classical and enhanced sampling techniques and thereby determine the causality of these protein-protein interactions. The study indicated that upon complexation, the aggregation propensity of both 14-3-3 and α-synuclein increases, and this increment is propelled by the interfacial residues on either protein. Furthermore, mutagenesis studies revealed that Lys214 of 14-3-3 (henceforth termed K214A) is crucial for the formation of this binary complex. Principal component analysis combined with clustering studies unveiled the stability of these complexes in terms of their conformational distribution across the entire MD trajectory. For K214A, these clustered states were sparsely located, thereby making the transitions between them slightly difficult. Dynamic cross-correlation maps (DCCM) revealed the role of residues in the range 80-130 of 14-3-3 having a potential allosteric role in driving this complexation process. Finally, a novel peptide-based supramolecular inhibitor was designed, which exhibited higher proficiency in limiting the 14-3-3/α-synuclein interaction compared to the previous inhibitor model. It was also revealed that the presence of this inhibitor induces structural rigidity in α-synuclein, making changes in its conformations extremely difficult, as observed through Umbrella Sampling studies. Based on available information, the current study provides an insight into the molecular-level understanding of protein-protein interactions underlying Parkinson's disease and adds on to the methods of devising novel therapeutic approaches to treat the same.

DOI: https://doi.org/10.1021/acs.jpcb.4c01743
Sci Adv. 2024 Jun 14. 10(24): eadm8449

Tau fibrils evade autophagy by excessive p62 coating and TAX1BP1 exclusion.

Luca Ferrari, Bernd Bauer, Yue Qiu, Martina Schuschnig, Sigrid Klotz, Dorothea Anrather, Thomas Juretschke, Petra Beli, Ellen Gelpi, Sascha Martens.

The accumulation of protein aggregates is a hallmark of many diseases, including Alzheimer's disease. As a major pillar of the proteostasis network, autophagy mediates the degradation of protein aggregates. The autophagy cargo receptor p62 recognizes ubiquitin on proteins and cooperates with TAX1BP1 to recruit the autophagy machinery. Paradoxically, protein aggregates are not degraded in various diseases despite p62 association. Here, we reconstituted the recognition by the autophagy receptors of physiological and pathological Tau forms. Monomeric Tau recruits p62 and TAX1BP1 via the sequential actions of the chaperone and ubiquitylation machineries. In contrast, Tau fibrils from Alzheimer's disease brains are recognized by p62 but fail to recruit TAX1BP1. This failure is due to the masking of fibrils ubiquitin moieties by p62. Tau fibrils are resistant to deubiquitylation, and, thus, this nonproductive interaction of p62 with the fibrils is irreversible. Our results shed light on the mechanism underlying autophagy evasion by protein aggregates and their consequent accumulation in disease.

DOI: https://doi.org/10.1126/sciadv.adm8449
Res Sq. 2024 May 30. pii: rs.3.rs-4407236. [Epub ahead of print]

Human tNeurons reveal aging-linked proteostasis deficits driving Alzheimer's phenotypes.

Judith Frydman, Ching-Chieh Chou, Ryan Vest, Miguel Prado, Joshua Wilson-Grady, Joao Paulo, Yohei Shibuya, Patricia Moran Losada, Ting-Ting Lee, Jian Luo, Steven Gygi, Jeffrey Kelly, Daniel Finley, Marius Wernig, Tony Wyss-Coray.

Aging is a prominent risk factor for Alzheimer's disease (AD), but the cellular mechanisms underlying neuronal phenotypes remain elusive. Both accumulation of amyloid plaques and neurofibrillary tangles in the brain1 and age-linked organelle deficits 2-7 are proposed as causes of AD phenotypes but the relationship between these events is unclear. Here, we address this question using a transdifferentiated neuron (tNeuron) model directly from human dermal fibroblasts. Patient-derived tNeurons retain aging hallmarks and exhibit AD-linked deficits. Quantitative tNeuron proteomic analyses identify aging and AD-linked deficits in proteostasis and organelle homeostasis, particularly affecting endosome-lysosomal components. The proteostasis and lysosomal homeostasis deficits in aged tNeurons are exacerbated in sporadic and familial AD tNeurons, promoting constitutive lysosomal damage and defects in ESCRT-mediated repair. We find deficits in neuronal lysosomal homeostasis lead to inflammatory cytokine secretion, cell death and spontaneous development of Aß and phospho-Tau deposits. These proteotoxic inclusions co-localize with lysosomes and damage markers and resemble inclusions in brain tissue from AD patients and APP-transgenic mice. Supporting the centrality of lysosomal deficits driving AD phenotypes, lysosome-function enhancing compounds reduce AD-associated cytokine secretion and Aβ deposits. We conclude that proteostasis and organelle deficits are upstream initiating factors leading to neuronal aging and AD phenotypes.

DOI: https://doi.org/10.21203/rs.3.rs-4407236/v1
Exp Cell Res. 2024 Jun 07. pii: S0014-4827(24)00209-X. [Epub ahead of print] 114118

Altered Autophagic Flux in GNE mutant cells of Indian Origin: potential drug target for GNE Myopathy.

Jyoti Oswalia, Shagun Singh, Vaishali Gautam, Ranjana Arya.

  Autophagy phenomenon in the cell maintains proteostasis balance by eliminating damaged organelles and protein aggregates. Imbalance in autophagic flux may cause accumulation of protein aggregates in various neurodegenerative disorders. Regulation of autophagy by either calcium or chaperone play a key role in the removal of protein aggregates from the cell. The neuromuscular rare genetic disorder, GNE Myopathy, is characterized by accumulation of rimmed vacuoles having protein aggregates of β-amyloid and tau that may result from altered autophagic flux. In the present study, the autophagic flux was deciphered in HEK cell-based model for GNE Myopathy harbouring GNE mutations of Indian origin. The refolding activity of HSP70 chaperone was found to be reduced in GNE mutant cells compared to wild type controls. The autophagic markers LC3II/I ratio was altered with increased number of autophagosome formation in GNE mutant cells compared to wild type cells. The cytosolic calcium levels were also increased in GNE mutant cells of Indian origin. Interestingly, treatment of GNE mutant cells with HSP70 activator, BGP-15, restored the expression and refolding activity of HSP70 along with autophagosome formation. Treatment with calcium chelator, BAPTA-AM restored the cytoplasmic calcium levels and autophagosome formation but not LC3II/I ratio significantly. Our study provides insights towards GNE mutation specific response for autophagy regulation and opens up a therapeutic advancement area in calcium signalling and HSP70 function for GNE related Myopathy.

Keywords:  GNE Myopathy; autophagy; calcium homeostasis; rare genetic disease

DOI:  https://doi.org/10.1016/j.yexcr.2024.114118