The neuropathological hallmarks of Parkinson's disease include preferential vulnerability of dopaminergic neurons of the substantia nigra pars compacta, and accumulation of intraneuronal protein ...inclusions known as Lewy bodies. These inclusions contain, among other proteins, aggregated alpha-synuclein and histone deacetylase 6 (HDAC6). In our study we found that selective inhibition of HDAC6 activity by Tubastatin A has protective effects in a rat model of Parkinson's disease. We provide evidence that this protection may be due to the activation of chaperone-mediated autophagy through the up-regulation of key members of this pathway. Moreover, Tubastatin A significantly inhibited the expression of a toxic form of alpha-synuclein that is phosphorylated at serine position 129. Tubastatin A treatment also permitted to partially modulate neuroinflammation. Taken together, our study highlights the neuroprotective effects of Tubastatin A in a rat model of Parkinson's disease and provides mechanistic insight in Tubastatin A-mediated protection against alpha-synuclein toxicity and substantia nigra degeneration. These findings are of potential therapeutic value in Parkinson's disease and other synucleinopathies.
Sirtuin genes have been associated with aging and are known to affect multiple cellular pathways. Sirtuin 2 was previously shown to modulate proteotoxicity associated with age-associated ...neurodegenerative disorders such as Alzheimer and Parkinson disease (PD). However, the precise molecular mechanisms involved remain unclear. Here, we provide mechanistic insight into the interplay between sirtuin 2 and α-synuclein, the major component of the pathognomonic protein inclusions in PD and other synucleinopathies. We found that α-synuclein is acetylated on lysines 6 and 10 and that these residues are deacetylated by sirtuin 2. Genetic manipulation of sirtuin 2 levels in vitro and in vivo modulates the levels of α-synuclein acetylation, its aggregation, and autophagy. Strikingly, mutants blocking acetylation exacerbate α-synuclein toxicity in vivo, in the substantia nigra of rats. Our study identifies α-synuclein acetylation as a key regulatory mechanism governing α-synuclein aggregation and toxicity, demonstrating the potential therapeutic value of sirtuin 2 inhibition in synucleinopathies.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Huntington's disease (HD) is an inherited neurodegenerative disease characterized by motor, cognitive and psychiatric symptoms. Atrophy of the striatum has been proposed for several years as a ...biomarker to assess disease progression in HD gene carriers. However, it does not provide any information about the biological mechanisms linked to HD pathogenesis. Changes in brain metabolites have been also consistently seen in HD patients and animal models using Magnetic Resonance Spectroscopy (MRS), but metabolite measurements are generally limited to a single voxel. In this study, we used Chemical Exchange Saturation Transfer imaging of glutamate (gluCEST) in order to map glutamate distribution in the brain of a knock-in mouse model (Ki140CAG) with a precise anatomical resolution. We demonstrated that both heterozygous and homozygous mice with pathological CAG repeat expansion in gene encoding huntingtin exhibited an atrophy of the striatum and a significant alteration of their metabolic profile in the striatum as compared to wild type littermate controls. The striatal decrease was then confirmed by gluCEST imaging. Surprisingly, CEST imaging also revealed that the corpus callosum was the most affected structure in both genotype groups, suggesting that this structure could be highly vulnerable in HD. We evaluated for the first time gluCEST imaging as a potential biomarker of HD and demonstrated its potential for characterizing metabolic defects in neurodegenerative diseases in specific regions.
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•A knock-in mouse model of Huntington's disease Ki140CAG is characterized.•Behavioral tests, MRS and glutamate imaging reveal significant alterations in mice.•The glutamate distribution is mapped in vivo into the brain using gluCEST imaging.•GluCEST imaging is proposed as a potential biomarker of Huntington's disease.
Tau abnormalities play a central role in several neurodegenerative diseases, collectively known as tauopathies. In the present study, we examined whether mutant huntingtin (mHtt), which causes ...Huntington's disease (HD), modifies Tau phosphorylation and subcellular localization using cell and mouse HD models. Initially, we used novel bimolecular fluorescence complementation assays in live cells to evaluate Tau interactions with either wild type (25QHtt) or mutant huntingtin (103QHtt). While 25QHtt and Tau interacted at the level of the microtubule network, 103QHtt and Tau interacted and formed 'ring-like' inclusions localized in the vicinity of the microtubular organizing center (MTOC). Fluorescence recovery after photobleaching experiments also indicated that, whereas homomeric 103QHtt/103QHtt pairs rapidly re-entered into inclusions, heteromeric 103QHtt/Tau pairs remained excluded from the 'ring-like' inclusions. Interestingly, in vitro Tau relocalization was associated to Tau hyperphosphorylation. Consistent with this observation, we found strong Tau hyperphosphorylation in brain samples from two different mouse models of HD, R6/2 and 140CAG knock-in. This was associated with a significant reduction in the levels of Tau phosphatases (PP1, PP2A and PP2B), with no apparent involvement of major Tau kinases. Thus, the present study strongly suggests that expression of mHtt leads to Tau hyperphosphorylation, relocalization and sequestration through direct protein-protein interactions in inclusion-like compartments in the vicinity of the MTOC. Likewise, our data also suggest that Tau alterations may also contribute to HD pathogenesis.
Expression of the neuronal kinase DCLK3 is reduced in Huntington's disease. Galvan et al. report that DCLK3 silencing in the mouse striatum exacerbates the toxicity of mutant huntingtin, whereas ...DCLK3 overexpression is neuroprotective, and show that DCLK3 regulates the expression of many genes involved in transcription regulation and chromatin remodelling.
Abstract
The neurobiological functions of a number of kinases expressed in the brain are unknown. Here, we report new findings on DCLK3 (doublecortin like kinase 3), which is preferentially expressed in neurons in the striatum and dentate gyrus. Its function has never been investigated. DCLK3 expression is markedly reduced in Huntington's disease. Recent data obtained in studies related to cancer suggest DCLK3 could have an anti-apoptotic effect. Thus, we hypothesized that early loss of DCLK3 in Huntington's disease may render striatal neurons more susceptible to mutant huntingtin (mHtt). We discovered that DCLK3 silencing in the striatum of mice exacerbated the toxicity of an N-terminal fragment of mHtt. Conversely, overexpression of DCLK3 reduced neurodegeneration produced by mHtt. DCLK3 also produced beneficial effects on motor symptoms in a knock-in mouse model of Huntington's disease. Using different mutants of DCLK3, we found that the kinase activity of the protein plays a key role in neuroprotection. To investigate the potential mechanisms underlying DCLK3 effects, we studied the transcriptional changes produced by the kinase domain in human striatal neurons in culture. Results show that DCLK3 regulates in a kinase-dependent manner the expression of many genes involved in transcription regulation and nucleosome/chromatin remodelling. Consistent with this, histological evaluation showed DCLK3 is present in the nucleus of striatal neurons and, protein-protein interaction experiments suggested that the kinase domain interacts with zinc finger proteins, including the transcriptional activator adaptor TADA3, a core component of the Spt-ada-Gcn5 acetyltransferase (SAGA) complex which links histone acetylation to the transcription machinery. Our novel findings suggest that the presence of DCLK3 in striatal neurons may play a key role in transcription regulation and chromatin remodelling in these brain cells, and show that reduced expression of the kinase in Huntington's disease could render the striatum highly vulnerable to neurodegeneration.
The mechanisms underlying preferential atrophy of the striatum in Huntington's disease (HD) are unknown. One hypothesis is that a set of gene products preferentially expressed in the striatum could ...determine the particular vulnerability of this brain region to mutant huntingtin (mHtt). Here, we studied the striatal protein µ-crystallin (Crym). Crym is the NADPH-dependent p38 cytosolic T3-binding protein (p38CTBP), a key regulator of thyroid hormone (TH) T3 (3,5,3'-triiodo-l-thyronine) transportation. It has been also recently identified as the enzyme that reduces the sulfur-containing cyclic ketimines, which are potential neurotransmitters. Here, we confirm the preferential expression of the Crym protein in the rodent and macaque striatum. Crym expression was found to be higher in the macaque caudate than in the putamen. Expression of Crym was reduced in the BACHD and Knock-in 140CAG mouse models of HD before onset of striatal atrophy. We show that overexpression of Crym in striatal medium-size spiny neurons using a lentiviral-based strategy in mice is neuroprotective against the neurotoxicity of an N-terminal fragment of mHtt in vivo. Thus, reduction of Crym expression in HD could render striatal neurons more susceptible to mHtt suggesting that Crym may be a key determinant of the vulnerability of the striatum. In addition our work points to Crym as a potential molecular link between striatal degeneration and the THs deregulation reported in HD patients.
The SARS-CoV-2 virus has triggered a worldwide pandemic. According to the BioGrid database, CLN7 (MFSD8) is thought to interact with several viral proteins. The aim of this work was to investigate a ...possible involvement of CLN7 in the infection process. Experiments on a CLN7-deficient HEK293T cell line exhibited a 90% reduced viral load compared to wild-type cells. This observation may be linked to the finding that CLN7 ko cells have a significantly reduced GM1 content in their cell membrane. GM1 is found highly enriched in lipid rafts, which are thought to play an important role in SARS-CoV-2 infection. In contrast, overexpression of CLN7 led to an increase in viral load. This study provides evidence that CLN7 is involved in SARS-CoV-2 infection. This makes it a potential pharmacological target for drug development against COVID-19. Furthermore, it provides insights into the physiological function of CLN7 where still only little is known about.
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•CLN7 knockout protects cells from SARS-CoV-2 infection•CLN7 knockout leads to a strong reduction of cellular GM1 content•A reduced GM1 content might lead to a reduced lipid raft function in CLN7-deficient cells
Virology; Cell biology
•Distinct molecular subtypes of microglia and astrocytes exist in the brain that have deleterious or beneficial effects on neurons.•Neuroinflammatory processes play an important role in ...neurodegenerative process of lysosomal diseases.•Common genetic, pathological, and molecular features exist that link rare lysosomal diseases to common age-related neurodegeneration.
Lysosomal storage diseases (LSDs) are rare genetic disorders caused by a disruption in cellular clearance, resulting in pathological storage of undegraded lysosomal substrates. Recent clinical and genetic studies have uncovered links between multiple LSDs and common neurodegenerative diseases such as Parkinson’s disease (PD). Here, we review recent literature describing the role of glia cells and neuroinflammation in PD and LSDs, including Gaucher disease (GD) and neuronal ceroid lipofuscinosis (NCL), and highlight converging inflammation pathways that lead to neuron loss. Recent data indicates that lysosomal dysfunction and accumulation of storage materials can initiate the activation of glial cells, through interaction with cell surface or cytosolic pattern recognition receptors that detect pathogenic aggregates of cellular debris. Activated glia cells could act to protect neurons through the elimination of toxic protein or lipid aggregates early in the disease process. However prolonged glial activation that occurs over several decades in chronic-age related neurodegeneration could induce the inappropriate elimination of synapses, leading to neuron loss. These studies provide mechanistic insight into the relationship between lysosomal dysfunction and glial activation, and offer novel therapeutic pathways for the treatment of PD and LSDs focused on reducing neuroinflammation and mitigating cell loss.
Neurodegenerative disorders are characterized by a collapse in proteostasis, as shown by the accumulation of insoluble protein aggregates in the brain. Proteostasis involves a balance of protein ...synthesis, folding, trafficking, and degradation, but how aggregates perturb these pathways is unknown. Using Parkinson’s disease (PD) patient midbrain cultures, we find that aggregated α-synuclein induces endoplasmic reticulum (ER) fragmentation and compromises ER protein folding capacity, leading to misfolding and aggregation of immature lysosomal β-glucocerebrosidase. Despite this, PD neurons fail to initiate the unfolded protein response, indicating perturbations in sensing or transducing protein misfolding signals in the ER. Small molecule enhancement of ER proteostasis machinery promotes β-glucocerebrosidase solubility, while simultaneous enhancement of trafficking improves ER morphology, lysosomal function, and reduces α-synuclein. Our studies suggest that aggregated α-synuclein perturbs the ability of neurons to respond to misfolded proteins in the ER, and that synergistic enhancement of multiple proteostasis branches may provide therapeutic benefit in PD.
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•α-Synuclein accumulation induces ER fragmentation in patient-derived midbrain neurons•α-Synuclein perturbs the neuron's ability to recognize and respond to misfolded proteins in the ER•Parkinson's neurons develop pathogenic aggregates of immature lysosomal GCase•GCase solubility/function is rescued by enhancing ER folding and downstream trafficking
Stojkovska et al. found that Parkinson’s patient neurons accumulate α-synuclein and are deficient at recognizing misfolded proteins in the endoplasmic reticulum (ER), inducing pathogenic aggregation of immature lysosomal hydrolases. This phenotype is rescued by combined enhancement of ER proteostasis and protein trafficking, leading to lysosomal activation and reduction of α-synuclein.
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