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Special Issue "Proteotoxicity and Neurodegenerative Diseases"

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Toxicology".

Deadline for manuscript submissions: closed (31 July 2020).

Special Issue Editors

Dr. Gessica Sala
E-Mail Website
Guest Editor
Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Monza (MB), Italy
Interests: neurodegenerative diseases; Parkinson’s disease; chaperone-mediated autophagy; macroautophagy; oxidative stress; excitotoxicity; peripheral cells; biomarkers
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Lucio Tremolizzo
E-Mail Website
Guest Editor
1. School of Medicine and Surgery, Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Monza (MB), Italy
2. Departmentof Neurology, San Gerardo Hospital, Monza (MB), Italy
Interests: neurodegenerative diseases; amyotrophic lateral sclerosis; dementia, oxidative stress; excitotoxicity; peripheral cells; biomarkers
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Many neurodegenerative diseases including Parkinson’s disease (PD), Alzheimer’s disease (AD), and amyotrophic lateral sclerosis (ALS) belong to the large category of proteinopathies, conditions characterized by the presence of proteinaceous inclusions within and/or outside the degenerating neurons. The identification of such aggregates supports the view that misfolded proteins represent a basic requirement for the neurodegenerative process and provides input to verify the existence of possible dysfunctions of the biological systems influencing protein homeostasis.

In neurodegenerative diseases, both environmental and genetic factors contribute to altering the physiological processes involved in the synthesis of disease-specific proteins, resulting in a protein over-production or in the generation of post-translationally modified protein forms more prone to aggregation. Furthermore, the impairment of intracellular protein catabolic systems plays a crucial role in proteotoxicity, and the prion-like spreading of pathological proteins further amplifies neuronal damage.

A better comprehension of the molecular mechanisms responsible for proteotoxicity in neurodegenerative diseases can allow the identification of both new therapeutic targets and useful biomarkers for these devastating disorders.

Dr. Gessica Sala
Prof. Dr. Lucio Tremolizzo
Guest Editors

Manuscript Submission Information

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Keywords

  • Parkinson’s disease
  • amyotrophic lateral sclerosis
  • Alzheimer’s disease
  • neurodegenerative diseases
  • alpha-synuclein
  • TDP-43
  • beta-amyloid
  • tau
  • genetics
  • catabolism

Published Papers (10 papers)

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Research

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Article
Dietary Wheat Amylase Trypsin Inhibitors Impact Alzheimer’s Disease Pathology in 5xFAD Model Mice
Int. J. Mol. Sci. 2020, 21(17), 6288; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21176288 - 31 Aug 2020
Cited by 5 | Viewed by 1285
Abstract
Wheat amylase trypsin inhibitors (ATIs) represent a common dietary protein component of gluten-containing cereals (wheat, rye, and barley). They act as toll-like receptor 4 ligands, and are largely resistant to intestinal proteases, eliciting a mild inflammatory response within the intestine after oral ingestion. [...] Read more.
Wheat amylase trypsin inhibitors (ATIs) represent a common dietary protein component of gluten-containing cereals (wheat, rye, and barley). They act as toll-like receptor 4 ligands, and are largely resistant to intestinal proteases, eliciting a mild inflammatory response within the intestine after oral ingestion. Importantly, nutritional ATIs exacerbated inflammatory bowel disease and features of fatty liver disease and the metabolic syndrome in mice. For Alzheimer’s disease (AD), both inflammation and altered insulin resistance are major contributing factors, impacting onset as well as progression of this devastating brain disorder in patients. In this study, we evaluated the impact of dietary ATIs on a well-known rodent model of AD (5xFAD). We assessed metabolic, behavioral, inflammatory, and microbial changes in mice consuming different dietary regimes with and without ATIs, consumed ad libitum for eight weeks. We demonstrate that ATIs, with or without a gluten matrix, had an impact on the metabolism and gut microbiota of 5xFAD mice, aggravating pathological hallmarks of AD. If these findings can be translated to patients, an ATI-depleted diet might offer an alternative therapeutic option for AD and warrants clinical intervention studies. Full article
(This article belongs to the Special Issue Proteotoxicity and Neurodegenerative Diseases)
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Article
Rapid Alpha-Synuclein Toxicity in a Neural Cell Model and Its Rescue by a Stearoyl-CoA Desaturase Inhibitor
Int. J. Mol. Sci. 2020, 21(15), 5193; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21155193 - 22 Jul 2020
Cited by 3 | Viewed by 906
Abstract
Genetic and biochemical evidence attributes neuronal loss in Parkinson’s disease (PD) and related brain diseases to dyshomeostasis of the 14 kDa protein α-synuclein (αS). There is no consensus on how αS exerts toxicity. Explanations range from disturbed vesicle biology to proteotoxicity caused by [...] Read more.
Genetic and biochemical evidence attributes neuronal loss in Parkinson’s disease (PD) and related brain diseases to dyshomeostasis of the 14 kDa protein α-synuclein (αS). There is no consensus on how αS exerts toxicity. Explanations range from disturbed vesicle biology to proteotoxicity caused by fibrillar aggregates. To probe these mechanisms further, robust cellular toxicity models are needed, but their availability is limited. We previously reported that a shift from dynamic multimers to monomers is an early event in αS dyshomeostasis, as caused by familial PD (fPD)-linked mutants such as E46K. Excess monomers accumulate in round, lipid-rich inclusions. Engineered αS ‘3K’ (E35K+E46K+E61K) amplifies E46K, causing a PD-like, L-DOPA-responsive motor phenotype in transgenic mice. Here, we present a cellular model of αS neurotoxicity after transducing human neuroblastoma cells to express yellow fluorescent protein (YFP)-tagged αS 3K in a doxycycline-dependent manner. αS-3K::YFP induction causes pronounced growth defects that accord with cell death. We tested candidate compounds for their ability to restore growth, and stearoyl-CoA desaturase (SCD) inhibitors emerged as a molecule class with growth-restoring capacity, but the therapeutic window varied among compounds. The SCD inhibitor MF-438 fully restored growth while exerting no apparent cytotoxicity. Our αS bioassay will be useful for elucidating compound mechanisms, for pharmacokinetic studies, and for compound/genetic screens. Full article
(This article belongs to the Special Issue Proteotoxicity and Neurodegenerative Diseases)
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Article
Human Neural Stem Cells Encoding ChAT Gene Restore Cognitive Function via Acetylcholine Synthesis, Aβ Elimination, and Neuroregeneration in APPswe/PS1dE9 Mice
Int. J. Mol. Sci. 2020, 21(11), 3958; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21113958 - 31 May 2020
Cited by 4 | Viewed by 1431
Abstract
In Alzheimer disease (AD) patients, degeneration of the cholinergic system utilizing acetylcholine for memory acquisition is observed. Since AD therapy using acetylcholinesterase (AChE) inhibitors are only palliative for memory deficits without slowing or reversing disease progress, there is a need for effective therapies, [...] Read more.
In Alzheimer disease (AD) patients, degeneration of the cholinergic system utilizing acetylcholine for memory acquisition is observed. Since AD therapy using acetylcholinesterase (AChE) inhibitors are only palliative for memory deficits without slowing or reversing disease progress, there is a need for effective therapies, and stem cell-based therapeutic approaches targeting AD should fulfill this requirement. We established a human neural stem cell (NSC) line encoding choline acetyltransferase (ChAT) gene, an acetylcholine-synthesizing enzyme. APPswe/PS1dE9 AD model mice transplanted with the F3.ChAT NSCs exhibited improved cognitive function and physical activity. Transplanted F3.ChAT NSCs in the AD mice differentiated into neurons and astrocytes, produced ChAT protein, increased the ACh level, and improved the learning and memory function. F3.ChAT cell transplantation reduced Aβ deposits by recovering microglial function; i.e., the down-regulation of β-secretase and inflammatory cytokines and up-regulation of Aβ-degrading enzyme neprilysin. F3.ChAT cells restored growth factors (GFs) and neurotrophic factors (NFs), and they induced the proliferation of NSCs in the host brain. These findings indicate that NSCs overexpressing ChAT can ameliorate complex cognitive and physical deficits of AD animals by releasing ACh, reducing Aβ deposit, and promoting neuroregeneration by the production of GFs/NFs. It is suggested that NSCs overexpressing ChAT could be a candidate for cell therapy in advanced AD therapy. Full article
(This article belongs to the Special Issue Proteotoxicity and Neurodegenerative Diseases)
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Article
Enhanced Clearance of Neurotoxic Misfolded Proteins by the Natural Compound Berberine and Its Derivatives
Int. J. Mol. Sci. 2020, 21(10), 3443; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21103443 - 13 May 2020
Cited by 2 | Viewed by 1539
Abstract
Background: Accumulation of misfolded proteins is a common hallmark of several neurodegenerative disorders (NDs) which results from a failure or an impairment of the protein quality control (PQC) system. The PQC system is composed by chaperones and the degradative systems (proteasome and autophagy). [...] Read more.
Background: Accumulation of misfolded proteins is a common hallmark of several neurodegenerative disorders (NDs) which results from a failure or an impairment of the protein quality control (PQC) system. The PQC system is composed by chaperones and the degradative systems (proteasome and autophagy). Mutant proteins that misfold are potentially neurotoxic, thus strategies aimed at preventing their aggregation or at enhancing their clearance are emerging as interesting therapeutic targets for NDs. Methods: We tested the natural alkaloid berberine (BBR) and some derivatives for their capability to enhance misfolded protein clearance in cell models of NDs, evaluating which degradative pathway mediates their action. Results: We found that both BBR and its semisynthetic derivatives promote degradation of mutant androgen receptor (ARpolyQ) causative of spinal and bulbar muscular atrophy, acting mainly via proteasome and preventing ARpolyQ aggregation. Overlapping effects were observed on other misfolded proteins causative of amyotrophic lateral sclerosis, frontotemporal-lobar degeneration or Huntington disease, but with selective and specific action against each different mutant protein. Conclusions: BBR and its analogues induce the clearance of misfolded proteins responsible for NDs, representing potential therapeutic tools to counteract these fatal disorders. Full article
(This article belongs to the Special Issue Proteotoxicity and Neurodegenerative Diseases)
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Review

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Review
Heterogeneity of Neuroinflammatory Responses in Amyotrophic Lateral Sclerosis: A Challenge or an Opportunity?
Int. J. Mol. Sci. 2020, 21(21), 7923; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21217923 - 25 Oct 2020
Cited by 4 | Viewed by 1347
Abstract
Amyotrophic Lateral Sclerosis (ALS) is a complex pathology: (i) the neurodegeneration is chronic and progressive; it starts focally in specific central nervous system (CNS) areas and spreads to different districts; (ii) multiple cell types further than motor neurons (i.e., glial/immune system cells) are [...] Read more.
Amyotrophic Lateral Sclerosis (ALS) is a complex pathology: (i) the neurodegeneration is chronic and progressive; it starts focally in specific central nervous system (CNS) areas and spreads to different districts; (ii) multiple cell types further than motor neurons (i.e., glial/immune system cells) are actively involved in the disease; (iii) both neurosupportive and neurotoxic neuroinflammatory responses were identified. Microglia cells (a key player of neuroinflammation in the CNS) attracted great interest as potential target cell population that could be modulated to counteract disease progression, at least in preclinical ALS models. However, the heterogeneous/multifaceted microglia cell responses occurring in different CNS districts during the disease represent a hurdle for clinical translation of single-drug therapies. To address this issue, over the past ten years, several studies attempted to dissect the complexity of microglia responses in ALS. In this review, we shall summarize these results highlighting how the heterogeneous signature displayed by ALS microglia reflects not only the extent of neuronal demise in different regions of the CNS, but also variable engagement in the attempts to cope with the neuronal damage. We shall discuss novel avenues opened by the advent of single-cell and spatial transcriptomics technologies, underlining the potential for discovery of novel therapeutic targets, as well as more specific diagnostic/prognostic not-invasive markers of neuroinflammation. Full article
(This article belongs to the Special Issue Proteotoxicity and Neurodegenerative Diseases)
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Review
Proteostasis and Proteotoxicity in the Network Medicine Era
Int. J. Mol. Sci. 2020, 21(17), 6405; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21176405 - 03 Sep 2020
Cited by 3 | Viewed by 1117
Abstract
Neurodegenerative proteinopathies are complex diseases that share some pathogenetic processes. One of these is the failure of the proteostasis network (PN), which includes all components involved in the synthesis, folding, and degradation of proteins, thus leading to the aberrant accumulation of toxic protein [...] Read more.
Neurodegenerative proteinopathies are complex diseases that share some pathogenetic processes. One of these is the failure of the proteostasis network (PN), which includes all components involved in the synthesis, folding, and degradation of proteins, thus leading to the aberrant accumulation of toxic protein aggregates in neurons. The single components that belong to the three main modules of the PN are highly interconnected and can be considered as part of a single giant network. Several pharmacological strategies have been proposed to ameliorate neurodegeneration by targeting PN components. Nevertheless, effective disease-modifying therapies are still lacking. In this review article, after a general description of the PN and its failure in proteinopathies, we will focus on the available pharmacological tools to target proteostasis. In this context, we will discuss the main advantages of systems-based pharmacology in contrast to the classical targeted approach, by focusing on network pharmacology as a strategy to innovate rational drug design. Full article
(This article belongs to the Special Issue Proteotoxicity and Neurodegenerative Diseases)
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Review
Proteotoxicity and Neurodegenerative Diseases
Int. J. Mol. Sci. 2020, 21(16), 5646; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21165646 - 06 Aug 2020
Cited by 6 | Viewed by 1099
Abstract
Neurodegenerative diseases are a major burden for our society, affecting millions of people worldwide. A main goal of past and current research is to enhance our understanding of the mechanisms underlying proteotoxicity, a common theme among these incurable and debilitating conditions. Cell proteome [...] Read more.
Neurodegenerative diseases are a major burden for our society, affecting millions of people worldwide. A main goal of past and current research is to enhance our understanding of the mechanisms underlying proteotoxicity, a common theme among these incurable and debilitating conditions. Cell proteome alteration is considered to be one of the main driving forces that triggers neurodegeneration, and unraveling the biological complexity behind the affected molecular pathways constitutes a daunting challenge. This review summarizes the current state on key processes that lead to cellular proteotoxicity in Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis, providing a comprehensive landscape of recent literature. A foundational understanding of how proteotoxicity affects disease etiology and progression may provide essential insight towards potential targets amenable of therapeutic intervention. Full article
(This article belongs to the Special Issue Proteotoxicity and Neurodegenerative Diseases)
Review
Cell-Clearing Systems Bridging Repeat Expansion Proteotoxicity and Neuromuscular Junction Alterations in ALS and SBMA
Int. J. Mol. Sci. 2020, 21(11), 4021; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21114021 - 04 Jun 2020
Cited by 6 | Viewed by 1383
Abstract
The coordinated activities of autophagy and the ubiquitin proteasome system (UPS) are key to preventing the aggregation and toxicity of misfold-prone proteins which manifest in a number of neurodegenerative disorders. These include proteins which are encoded by genes containing nucleotide repeat expansions. In [...] Read more.
The coordinated activities of autophagy and the ubiquitin proteasome system (UPS) are key to preventing the aggregation and toxicity of misfold-prone proteins which manifest in a number of neurodegenerative disorders. These include proteins which are encoded by genes containing nucleotide repeat expansions. In the present review we focus on the overlapping role of autophagy and the UPS in repeat expansion proteotoxicity associated with chromosome 9 open reading frame 72 (C9ORF72) and androgen receptor (AR) genes, which are implicated in two motor neuron disorders, amyotrophic lateral sclerosis (ALS) and spinal-bulbar muscular atrophy (SBMA), respectively. At baseline, both C9ORF72 and AR regulate autophagy, while their aberrantly-expanded isoforms may lead to a failure in both autophagy and the UPS, further promoting protein aggregation and toxicity within motor neurons and skeletal muscles. Besides proteotoxicity, autophagy and UPS alterations are also implicated in neuromuscular junction (NMJ) alterations, which occur early in both ALS and SBMA. In fact, autophagy and the UPS intermingle with endocytic/secretory pathways to regulate axonal homeostasis and neurotransmission by interacting with key proteins which operate at the NMJ, such as agrin, acetylcholine receptors (AChRs), and adrenergic beta2 receptors (B2-ARs). Thus, alterations of autophagy and the UPS configure as a common hallmark in both ALS and SBMA disease progression. The findings here discussed may contribute to disclosing overlapping molecular mechanisms which are associated with a failure in cell-clearing systems in ALS and SBMA. Full article
(This article belongs to the Special Issue Proteotoxicity and Neurodegenerative Diseases)
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Review
Shared Genomic and Proteomic Contribution of Amyloid and Tau Protein Characteristic of Alzheimer’s Disease to Brain Ischemia
Int. J. Mol. Sci. 2020, 21(9), 3186; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21093186 - 30 Apr 2020
Cited by 9 | Viewed by 1010
Abstract
Post-ischemic brain damage is associated with the deposition of folding proteins such as the amyloid and tau protein in the intra- and extracellular spaces of brain tissue. In this review, we summarize the protein changes associated with Alzheimer’s disease and their gene expression [...] Read more.
Post-ischemic brain damage is associated with the deposition of folding proteins such as the amyloid and tau protein in the intra- and extracellular spaces of brain tissue. In this review, we summarize the protein changes associated with Alzheimer’s disease and their gene expression (amyloid protein precursor and tau protein) after ischemia-reperfusion brain injury and their role in the post-ischemic injury. Recent advances in understanding the post-ischemic neuropathology have revealed dysregulation of amyloid protein precursor, α-secretase, β-secretase, presenilin 1 and 2, and tau protein genes after ischemic brain injury. However, reduced expression of the α-secretase in post-ischemic brain causes neurons to be less resistant to injury. In this review, we present the latest evidence that proteins associated with Alzheimer’s disease and their genes play a key role in progressive brain damage due to ischemia and reperfusion, and that an ischemic episode is an essential and leading supplier of proteins and genes associated with Alzheimer’s disease in post-ischemic brain. Understanding the underlying processes of linking Alzheimer’s disease-related proteins and their genes in post-ischemic brain injury with the risk of developing Alzheimer’s disease will provide the most significant goals for therapeutic development to date. Full article
(This article belongs to the Special Issue Proteotoxicity and Neurodegenerative Diseases)
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Review
Promiscuous Roles of Autophagy and Proteasome in Neurodegenerative Proteinopathies
Int. J. Mol. Sci. 2020, 21(8), 3028; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms21083028 - 24 Apr 2020
Cited by 25 | Viewed by 1898
Abstract
Alterations in autophagy and the ubiquitin proteasome system (UPS) are commonly implicated in protein aggregation and toxicity which manifest in a number of neurological disorders. In fact, both UPS and autophagy alterations are bound to the aggregation, spreading and toxicity of the so-called [...] Read more.
Alterations in autophagy and the ubiquitin proteasome system (UPS) are commonly implicated in protein aggregation and toxicity which manifest in a number of neurological disorders. In fact, both UPS and autophagy alterations are bound to the aggregation, spreading and toxicity of the so-called prionoid proteins, including alpha synuclein (α-syn), amyloid-beta (Aβ), tau, huntingtin, superoxide dismutase-1 (SOD-1), TAR-DNA-binding protein of 43 kDa (TDP-43) and fused in sarcoma (FUS). Recent biochemical and morphological studies add to this scenario, focusing on the coordinated, either synergistic or compensatory, interplay that occurs between autophagy and the UPS. In fact, a number of biochemical pathways such as mammalian target of rapamycin (mTOR), transcription factor EB (TFEB), Bcl2-associated athanogene 1/3 (BAG3/1) and glycogen synthase kinase beta (GSk3β), which are widely explored as potential targets in neurodegenerative proteinopathies, operate at the crossroad between autophagy and UPS. These biochemical steps are key in orchestrating the specificity and magnitude of the two degradation systems for effective protein homeostasis, while intermingling with intracellular secretory/trafficking and inflammatory pathways. The findings discussed in the present manuscript are supposed to add novel viewpoints which may further enrich our insight on the complex interactions occurring between cell-clearing systems, protein misfolding and propagation. Discovering novel mechanisms enabling a cross-talk between the UPS and autophagy is expected to provide novel potential molecular targets in proteinopathies. Full article
(This article belongs to the Special Issue Proteotoxicity and Neurodegenerative Diseases)
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