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Frontiers in Bioscience (Landmark... Nov 2023As a chronic degenerative disorder of the central nervous system that affects both motor and non-motor systems, Parkinson's disease (PD) is very complex, and...
BACKGROUND
As a chronic degenerative disorder of the central nervous system that affects both motor and non-motor systems, Parkinson's disease (PD) is very complex, and explanations and models are needed to better understand how dopaminergic neurons are affected and microglia are activated.
METHODS
A theoretical protein-RNA recognition code that assumes that the second letter in codons is compatible with specific amino acids involved in protein-RNA recognition was used to search for compatibility of human α-synuclein (α-syn) with mRNAs in the human transcriptome (1-L transcription).
RESULTS
The 1-L transcription revealed compatible amino acid sequences with the ATTTA ARE (class I), PAS and polyA in α-syn, supporting a protein-RNA regulatory model. In PD, inflammatory microglia reactions, cognitive decline and motor circuit disturbances are observed. The model theoretically explains why α-syn producing neurons are less protected from inflammation and why microglia are activated. Consistent with knowledge of PD, the identified genes showed how the PI3K-AKT pathway is downregulated, how reactive oxygen species (ROS) production and sensitivity are increased, how mitochondria are destabilized, why autophagy is impaired, and why neuronal depigmentation is observed.
CONCLUSIONS
1-L transcription of α-syn leads to genes/proteins relevant to PD. When α-syn is accepted as a small RNA recognition protein involved in the post-transcriptional regulations, some identified genes indicate that its function is an important regulatory factor associated with intracellular and extracellular transport of RNA vesicles. These vesicles are extremely important in cellular communication. In addition, the spectrum of identified genes strongly indicates that α-syn produced by neuronal cells is required for proper regulation of inflammatory and immune responses.
Topics: Humans; Parkinson Disease; Phosphatidylinositol 3-Kinases; alpha-Synuclein; Gene Expression Regulation; Inflammation; Dopaminergic Neurons; RNA
PubMed: 38062843
DOI: 10.31083/j.fbl2811292 -
Molecular Neurodegeneration May 2024Synucleinopathies are a group of neurodegenerative diseases characterized by the accumulation of α-synuclein (α-syn) in the brain, leading to motor and...
Synucleinopathies are a group of neurodegenerative diseases characterized by the accumulation of α-synuclein (α-syn) in the brain, leading to motor and neuropsychiatric symptoms. Currently, there are no known cures for synucleinopathies, and treatments mainly focus on symptom management. In this study, we developed a single-domain antibody (sdAb)-based protein degrader with features designed to enhance proteasomal degradation of α-syn. This sdAb derivative targets both α-syn and Cereblon (CRBN), a substrate-receptor for the E3-ubiquitin ligase CRL4, and thereby induces α-syn ubiquitination and proteasomal degradation. Our results indicate that this therapeutic candidate enhances proteasomal degradation of α-syn, in addition to the endogenous lysosomal degradation machinery. By promoting proteasomal degradation of α-syn, we improved clearance of α-syn in primary culture and mouse models of synucleinopathy. These findings indicate that our sdAb-based protein degrader is a promising therapeutic candidate for synucleinopathies. Considering that only a small percentage of antibodies enter the brain, more potent sdAbs with greater brain entry than whole antibodies could enhance clinical benefits of antibody-based therapies.
Topics: Animals; Synucleinopathies; alpha-Synuclein; Mice; Humans; Single-Domain Antibodies; Disease Models, Animal; Brain; Proteasome Endopeptidase Complex
PubMed: 38816762
DOI: 10.1186/s13024-024-00730-y -
Nature Communications Apr 2023Accumulation of α-synuclein into toxic oligomers or fibrils is implicated in dopaminergic neurodegeneration in Parkinson's disease. Here we performed a high-throughput,...
Accumulation of α-synuclein into toxic oligomers or fibrils is implicated in dopaminergic neurodegeneration in Parkinson's disease. Here we performed a high-throughput, proteome-wide peptide screen to identify protein-protein interaction inhibitors that reduce α-synuclein oligomer levels and their associated cytotoxicity. We find that the most potent peptide inhibitor disrupts the direct interaction between the C-terminal region of α-synuclein and CHarged Multivesicular body Protein 2B (CHMP2B), a component of the Endosomal Sorting Complex Required for Transport-III (ESCRT-III). We show that α-synuclein impedes endolysosomal activity via this interaction, thereby inhibiting its own degradation. Conversely, the peptide inhibitor restores endolysosomal function and thereby decreases α-synuclein levels in multiple models, including female and male human cells harboring disease-causing α-synuclein mutations. Furthermore, the peptide inhibitor protects dopaminergic neurons from α-synuclein-mediated degeneration in hermaphroditic C. elegans and preclinical Parkinson's disease models using female rats. Thus, the α-synuclein-CHMP2B interaction is a potential therapeutic target for neurodegenerative disorders.
Topics: Male; Female; Animals; Rats; Humans; Parkinson Disease; alpha-Synuclein; Caenorhabditis elegans; Dopaminergic Neurons; Endosomal Sorting Complexes Required for Transport; Peptides
PubMed: 37076542
DOI: 10.1038/s41467-023-37464-2 -
Platelets Dec 2023Platelets play many roles in the vasculature ensuring proper hemostasis and maintaining integrity. These roles are facilitated, in part, by cargo molecules released from...
Platelets play many roles in the vasculature ensuring proper hemostasis and maintaining integrity. These roles are facilitated, in part, by cargo molecules released from platelet granules via oluble SF ttachment rotein eceptor (SNARE) mediated membrane fusion, which is controlled by several protein-protein interactions. Chaperones have been characterized for t-SNAREs (. Munc18b for Syntaxin-11), but none have been clearly identified for v-SNAREs. α-Synuclein has been proposed as a v-SNARE chaperone which may affect SNARE-complex assembly, fusion pore opening, and thus secretion. Despite its abundance and that it is the only isoform present, α-synuclein's role in platelet secretion is uncharacterized. In this study, immunofluorescence showed that α-synuclein was present on punctate structures that co-stained with markers for α-granules and lysosomes and in a cytoplasmic pool. We analyzed the phenotype of α-synuclein mice and their platelets. Platelets from knockout mice had a mild, agonist-dependent secretion defect but aggregation and spreading were unaffected. Consistently, thrombosis/hemostasis were unaffected in the tail-bleeding, FeCl carotid injury and jugular vein puncture models. None of the platelet secretory machinery examined, . the v-SNAREs, were affected by α-synuclein's loss. The results indicate that, despite its abundance, α-synuclein has only a limited role in platelet function and thrombosis.
Topics: Animals; Mice; alpha-Synuclein; Blood Platelets; Cytoplasmic Granules; Exocytosis; Mice, Knockout; Platelet Activation; Protein Isoforms; SNARE Proteins; Thrombosis
PubMed: 37927048
DOI: 10.1080/09537104.2023.2267147 -
Biomolecules Apr 2022Alpha-synuclein (α-syn) is a small protein composed of 140 amino acids and belongs to the group of intrinsically disordered proteins. It is a soluble protein that is... (Review)
Review
Alpha-synuclein (α-syn) is a small protein composed of 140 amino acids and belongs to the group of intrinsically disordered proteins. It is a soluble protein that is highly expressed in neurons and expressed at low levels in glial cells. The monomeric protein aggregation process induces the formation of oligomeric intermediates and proceeds towards fibrillar species. These α-syn conformational species have been detected in the extracellular space and mediate consequences on surrounding neurons and glial cells. In particular, higher-ordered α-syn aggregates are involved in microglial and oligodendrocyte activation, as well as in the induction of astrogliosis. These phenomena lead to mitochondrial dysfunction, reactive oxygen and nitrogen species formation, and the induction of an inflammatory response, associated with neuronal cell death. Several receptors participate in cell activation and/or in the uptake of α-syn, which can vary depending on the α-syn aggregated state and cell types. The receptors involved in this process are of outstanding relevance because they may constitute potential therapeutic targets for the treatment of PD and related synucleinopathies. This review article focuses on the mechanism associated with extracellular α-syn uptake in glial cells and the consequent glial cell activation that contributes to the neuronal death associated with synucleinopathies.
Topics: Humans; Neuroglia; Parkinson Disease; Protein Aggregates; Synucleinopathies; alpha-Synuclein
PubMed: 35625583
DOI: 10.3390/biom12050655 -
Nature Communications Jul 2022Pathogenic α-synuclein (α-syn) is a prion-like protein that drives the pathogenesis of Lewy Body Dementia (LBD) and Parkinson's Disease (PD). To target pathogenic...
Pathogenic α-synuclein (α-syn) is a prion-like protein that drives the pathogenesis of Lewy Body Dementia (LBD) and Parkinson's Disease (PD). To target pathogenic α-syn preformed fibrils (PFF), here we designed extracellular disulfide bond-free synthetic nanobody libraries in yeast. Following selection, we identified a nanobody, PFFNB2, that can specifically recognize α-syn PFF over α-syn monomers. PFFNB2 cannot inhibit the aggregation of α-syn monomer, but can significantly dissociate α-syn fibrils. Furthermore, adeno-associated virus (AAV)-encoding EGFP fused to PFFNB2 (AAV-EGFP-PFFNB2) can inhibit PFF-induced α-syn serine 129 phosphorylation (pS129) in mouse primary cortical neurons, and prevent α-syn pathology spreading to the cortex in the transgenic mice expressing human wild type (WT) α-syn by intrastriatal-PFF injection. The pS129 immunoreactivity is negatively correlated with the expression of AAV-EGFP-PFFNB2. In conclusion, PFFNB2 holds a promise for mechanistic exploration and therapeutic development in α-syn-related pathogenesis.
Topics: Animals; Humans; Lewy Body Disease; Mice; Parkinson Disease; Prions; Synucleinopathies; alpha-Synuclein
PubMed: 35853942
DOI: 10.1038/s41467-022-31787-2 -
Acta Neuropathologica Communications Nov 2023Misfolded α-synuclein (α-syn) is believed to contribute to neurodegeneration in Lewy body disease (LBD) based on considerable evidence including a gene-dosage effect...
Misfolded α-synuclein (α-syn) is believed to contribute to neurodegeneration in Lewy body disease (LBD) based on considerable evidence including a gene-dosage effect observed in relation to point mutations and multiplication of SNCA in familial Parkinson's disease. A contradictory concept proposes early loss of the physiological α-syn as the major driver of neurodegeneration. There is a paucity of data on SNCA transcripts in various α-syn immunoreactive cytopathologies. Here, the total cell body, nuclear, and cytoplasmic area density of SNCA transcripts in neurons without and with various α-syn immunoreactive cytopathologies in the substantia nigra and amygdala in autopsy cases of LBD (n = 5) were evaluated using RNAscope combined with immunofluorescence for disease-associated α-syn. Single-nucleus RNA sequencing was performed to elucidate cell-type specific SNCA expression in non-diseased frontal cortex (n = 3). SNCA transcripts were observed in the neuronal nucleus and cytoplasm in neurons without α-syn, those containing punctate α-syn immunoreactivity, irregular-shaped compact inclusion, and brainstem-type and cortical-type LBs. However, SNCA transcripts were only rarely found in the α-syn immunoreactive LB areas. The total cell body SNCA transcript area densities in neurons with punctate α-syn immunoreactivity were preserved but were significantly reduced in neurons with compact α-syn inclusions both in the substantia nigra and amygdala. This reduction was also observed in the cytoplasm but not in the nucleus. Only single SNCA transcripts were detected in astrocytes with or without disease-associated α-syn immunoreactivity in the amygdala. Single-nucleus RNA sequencing revealed that excitatory and inhibitory neurons, oligodendrocyte progenitor cells, oligodendrocytes, and homeostatic microglia expressed SNCA transcripts, while expression was largely absent in astrocytes and microglia. The preserved cellular SNCA expression in the more abundant non-Lewy body type α-syn cytopathologies might provide a pool for local protein production that can aggregate and serve as a seed for misfolded α-syn. Successful segregation of disease-associated α-syn is associated with the exhaustion of SNCA production in the terminal cytopathology, the Lewy body. Our observations inform therapy development focusing on targeting SNCA transcription in LBD.
Topics: Humans; alpha-Synuclein; Lewy Bodies; Parkinson Disease; Lewy Body Disease; Neurons
PubMed: 37996943
DOI: 10.1186/s40478-023-01687-7 -
Journal of Neurochemistry Apr 2020Protein aggregation plays a central role in numerous neurodegenerative diseases. The key proteins in these diseases are of significant importance, but their...
Disentangling aggregation-prone proteins: a new method for isolating α-synuclein species: An Editorial Highlight for "A simple, versatile and robust centrifugation-based filtration protocol for the isolation and quantification of α-synuclein monomers, oligomers and fibrils: Towards improving...
Protein aggregation plays a central role in numerous neurodegenerative diseases. The key proteins in these diseases are of significant importance, but their investigation can be challenging due to unique properties of protein misfolding and oligomerization. Alpha-synuclein protein (α-Syn) is the predominant component of Lewy Bodies in Parkinson's disease (PD) and is a member of this class of proteins. Many α-Syn studies are limited by the inability to separate various monomeric, oligomeric, and fibrillar forms of the protein from heterogeneous mixtures. This Editorial Highlight summarizes the impact of a study published in the current issue of Journal of Neurochemistry, in which Lashuel and colleagues developed a simple, rapid centrifugation- and filter-based method for separating, isolating, and quantifying different forms of α-Syn. The researchers used electron microscopy, SDS-PAGE, circular dichroism, and protein assays to carefully validate the method and quantitate α-Syn yields and loss. The publication of this new method will not only aid in future studies of α-Syn, but will likely extend to other proteins that underlie a variety of neurodegenerative diseases.
Topics: Centrifugation; Filtration; Humans; Parkinson Disease; Protein Aggregation, Pathological; Reproducibility of Results; alpha-Synuclein
PubMed: 32037541
DOI: 10.1111/jnc.14973 -
Translational Neurodegeneration Feb 2024It is now realized that Parkinson's disease (PD) pathology extends beyond the substantia nigra, affecting both central and peripheral nervous systems, and exhibits a...
BACKGROUND
It is now realized that Parkinson's disease (PD) pathology extends beyond the substantia nigra, affecting both central and peripheral nervous systems, and exhibits a variety of non-motor symptoms often preceding motor features. Neuroinflammation induced by activated microglia and astrocytes is thought to underlie these manifestations. α-Synuclein aggregation has been linked with sustained neuroinflammation in PD, aggravating neuronal degeneration; however, there is still a lack of critical information about the structural identity of the α-synuclein conformers that activate microglia and/or astrocytes and the molecular pathways involved.
METHODS
To investigate the role of α-synuclein conformers in the development and maintenance of neuroinflammation, we used primary quiescent microglia and astrocytes, post-mortem brain tissues from PD patients and A53T α-synuclein transgenic mice that recapitulate key features of PD-related inflammatory responses in the absence of cell death, i.e., increased levels of pro-inflammatory cytokines and complement proteins. Biochemical and -omics techniques including RNAseq and secretomic analyses, combined with 3D reconstruction of individual astrocytes and live calcium imaging, were used to uncover the molecular mechanisms underlying glial responses in the presence of α-synuclein oligomers in vivo and in vitro.
RESULTS
We found that the presence of SDS-resistant hyper-phosphorylated α-synuclein oligomers, but not monomers, was correlated with sustained inflammatory responses, such as elevated levels of endogenous antibodies and cytokines and microglial activation. Similar oligomeric α-synuclein species were found in post-mortem human brain samples of PD patients but not control individuals. Detailed analysis revealed a decrease in Iba1/CD68 microglia and robust alterations in astrocyte number and morphology including process retraction. Our data indicated an activation of the p38/ATF2 signaling pathway mostly in microglia and a sustained induction of the NF-κB pathway in astrocytes of A53T mice. The sustained NF-κB activity triggered the upregulation of astrocytic T-type Ca3.2 Ca channels, altering the astrocytic secretome and promoting the secretion of IGFBPL1, an IGF-1 binding protein with anti-inflammatory and neuroprotective potential.
CONCLUSIONS
Our work supports a causative link between the neuron-produced α-synuclein oligomers and sustained neuroinflammation in vivo and maps the signaling pathways that are stimulated in microglia and astrocytes. It also highlights the recruitment of astrocytic Ca3.2 channels as a potential neuroprotective mediator against the α-synuclein-induced neuroinflammation.
Topics: Humans; Mice; Animals; alpha-Synuclein; NF-kappa B; Astrocytes; Neuroinflammatory Diseases; Calcium Signaling; Parkinson Disease; Mice, Transgenic; Cytokines
PubMed: 38378800
DOI: 10.1186/s40035-024-00401-4 -
Nature Chemical Biology May 2024Amyloid-forming proteins such α-synuclein and tau, which are implicated in Alzheimer's and Parkinson's disease, can form different fibril structures or strains with...
Amyloid-forming proteins such α-synuclein and tau, which are implicated in Alzheimer's and Parkinson's disease, can form different fibril structures or strains with distinct toxic properties, seeding activities and pathology. Understanding the determinants contributing to the formation of different amyloid features could open new avenues for developing disease-specific diagnostics and therapies. Here we report that O-GlcNAc modification of α-synuclein monomers results in the formation of amyloid fibril with distinct core structure, as revealed by cryogenic electron microscopy, and diminished seeding activity in seeding-based neuronal and rodent models of Parkinson's disease. Although the mechanisms underpinning the seeding neutralization activity of the O-GlcNAc-modified fibrils remain unclear, our in vitro mechanistic studies indicate that heat shock proteins interactions with O-GlcNAc fibril inhibit their seeding activity, suggesting that the O-GlcNAc modification may alter the interactome of the α-synuclein fibrils in ways that lead to reduce seeding activity in vivo. Our results show that posttranslational modifications, such as O-GlcNAc modification, of α-synuclein are key determinants of α-synuclein amyloid strains and pathogenicity.
Topics: alpha-Synuclein; Amyloid; Humans; Animals; Mice; Parkinson Disease; Acetylglucosamine; Protein Processing, Post-Translational; Cryoelectron Microscopy; Neurons
PubMed: 38347213
DOI: 10.1038/s41589-024-01551-2