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Science Advances Mar 2024Stressed cells secret misfolded proteins lacking signaling sequence via an unconventional protein secretion (UcPS) pathway, but how misfolded proteins are targeted...
Stressed cells secret misfolded proteins lacking signaling sequence via an unconventional protein secretion (UcPS) pathway, but how misfolded proteins are targeted selectively in UcPS is unclear. Here, we report that misfolded UcPS clients are subject to modification by a ubiquitin-like protein named ubiquitin-fold modifier 1 (UFM1). Using α-synuclein (α-Syn) as a UcPS model, we show that mutating the UFMylation sites in α-Syn or genetic inhibition of the UFMylation system mitigates α-Syn secretion, whereas overexpression of UFBP1, a component of the endoplasmic reticulum-associated UFMylation ligase complex, augments α-Syn secretion in mammalian cells and in model organisms. UFM1 itself is cosecreted with α-Syn, and the serum UFM1 level correlates with that of α-Syn. Because UFM1 can be directly recognized by ubiquitin specific peptidase 19 (USP19), a previously established UcPS stimulator known to associate with several chaperoning activities, UFMylation might facilitate substrate engagement by USP19, allowing stringent and regulated selection of misfolded proteins for secretion and proteotoxic stress alleviation.
Topics: Animals; Humans; alpha-Synuclein; Protein Transport; Endoplasmic Reticulum; Mammals; Endopeptidases
PubMed: 38489364
DOI: 10.1126/sciadv.adk2542 -
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 -
International Journal of Molecular... Mar 2024Synucleins are a family of proteins consisting of α, β, and γ synuclein (syn) [...].
Synucleins are a family of proteins consisting of α, β, and γ synuclein (syn) [...].
Topics: alpha-Synuclein; beta-Synuclein; gamma-Synuclein
PubMed: 38542197
DOI: 10.3390/ijms25063223 -
Aging Cell Oct 2023Parkinson's disease (PD) is a neurodegenerative disorder associated with α-synuclein aggregation and dopaminergic neuron loss in the midbrain. There is evidence that...
Parkinson's disease (PD) is a neurodegenerative disorder associated with α-synuclein aggregation and dopaminergic neuron loss in the midbrain. There is evidence that psychological stress promotes PD progression by enhancing glucocorticoids-related oxidative damage, however, the mechanisms involved are unknown. The present study demonstrated that plasma membrane phospholipid peroxides, as determined by phospholipidomics, triggered ferroptosis in dopaminergic neurons, which in turn contributed to stress exacerbated PD-like motor disorder in mice overexpressing mutant human α-synuclein. Using hormonomics, we identified that stress stimulated corticosteroid release and promoted 15-lipoxygenase-1 (ALOX15)-mediated phospholipid peroxidation. ALOX15 was upregulated by α-synuclein overexpression and acted as a fundamental risk factor in the development of chronic stress-induced parkinsonism and neurodegeneration. Further, we demonstrated the mechanism by which corticosteroids activated the PKC pathway and induced phosphatidylethanolamine-binding protein-1 (PEBP1) to form a complex with ALOX15, thereby facilitating ALOX15 to locate on the plasma membrane phospholipids. A natural product isolated from herbs, leonurine, was screened with activities of inhibiting the ALOX15/PEBP1 interaction and thereby attenuating membrane phospholipid peroxidation. Collectively, our findings demonstrate that stress increases the susceptibility of PD by driving membrane lipid peroxidation of dopaminergic neurons and suggest the ALOX15/PEBP1 complex as a potential intervention target.
Topics: Mice; Humans; Animals; Parkinson Disease; alpha-Synuclein; Dopaminergic Neurons; Disease Susceptibility; Stress, Psychological
PubMed: 37622525
DOI: 10.1111/acel.13970 -
Nature Chemistry Sep 2023Protein liquid-liquid phase separation can lead to disease-related amyloid fibril formation. The mechanisms of conversion of monomeric protein into condensate droplets...
Protein liquid-liquid phase separation can lead to disease-related amyloid fibril formation. The mechanisms of conversion of monomeric protein into condensate droplets and of the latter into fibrils remain elusive. Here, using mass photometry, we demonstrate that the Parkinson's disease-related protein, α-synuclein, can form dynamic nanoscale clusters at physiologically relevant, sub-saturated concentrations. Nanoclusters nucleate in bulk solution and promote amyloid fibril formation of the dilute-phase monomers upon ageing. Their formation is instantaneous, even under conditions where macroscopic assemblies appear only after several days. The slow growth of the nanoclusters can be attributed to a kinetic barrier, probably due to an interfacial penalty from the charged C terminus of α-synuclein. Our findings reveal that α-synuclein phase separation occurs at much wider ranges of solution conditions than reported so far. Importantly, we establish mass photometry as a promising methodology to detect and quantify nanoscale precursors of phase separation. We also demonstrate its general applicability by probing the existence of nanoclusters of a non-amyloidogenic protein, Ddx4n1.
Topics: Humans; alpha-Synuclein; Amyloid; Parkinson Disease
PubMed: 37337111
DOI: 10.1038/s41557-023-01244-8 -
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 -
Cell Biochemistry and Biophysics Sep 2023α-Synucleinopathies are a group of neurodegenerative disorders characterized by alterations in α-synuclein (α-syn), a protein associated with membrane phospholipids,...
α-Synucleinopathies are a group of neurodegenerative disorders characterized by alterations in α-synuclein (α-syn), a protein associated with membrane phospholipids, whose precise function in normal cells is still unknown. These kinds of diseases are caused by multiple factors, but the regulation of the α-syn gene is believed to play a central role in the pathology of these disorders; therefore, the α-syn gene is one of the most studied genes. α-Synucleinopathies are complex disorders that derive from the interaction between genetic and environmental factors. Here, we offer an update on the landscape of the epigenetic regulation of α-syn gene expression that has been linked with α-synucleinopathies. We also delve into the reciprocal influence between epigenetic modifications and other factors related to these disorders, such as posttranslational modifications, microbiota participation, interactions with lipids, neuroinflammation and oxidative stress, to promote α-syn aggregation by acting on the transcription and/or translation of the α-syn gene.
Topics: Humans; Synucleinopathies; Epigenesis, Genetic; alpha-Synuclein
PubMed: 37526884
DOI: 10.1007/s12013-023-01154-z -
Gut Microbes Dec 2023Alpha-synuclein (α-syn) pathology is the hallmark of Parkinson's disease (PD). The leucine-rich repeat kinase 2 () gene is a major-effect risk gene for sporadic PD...
Alpha-synuclein (α-syn) pathology is the hallmark of Parkinson's disease (PD). The leucine-rich repeat kinase 2 () gene is a major-effect risk gene for sporadic PD (sPD). However, what environmental factors may trigger the formation of α-syn pathology in carriers of risk variants are still unknown. Here, we report that a markedly increased abundance of (. ) in the intestinal microbiota was detected in risk variant(R1628P or G2385R) carriers with sPD compared with carriers without sPD. Animal experiments showed that . administration triggered pathological α-syn accumulation in the colon and spread to the brain via the gut-brain axis in R1628P mice, due to the co-occurrence of variant-induced inhibition of α-syn autophagic degradation and increased phosphorylation of α-syn caused by curli in . -derived extracellular vesicles. Fecal microbiota transplantation (FMT) effectively ameliorated motor deficits and α-syn pathology in R1628P mice. Our findings elaborate on the mechanism that triggers α-syn pathology in R1628P mice, and highlight a novel gene-environment interaction pattern in risk variants. Even more importantly, the findings reveal the interplay between the specific risk gene and the matched environmental factors triggers the initiation of α-syn pathology in sPD.
Topics: Mice; Animals; Parkinson Disease; Mice, Transgenic; alpha-Synuclein; Escherichia coli; Gastrointestinal Microbiome
PubMed: 38010914
DOI: 10.1080/19490976.2023.2276296 -
Analytical Chemistry Dec 2023α-Synuclein is an intrinsically disordered protein that plays a critical role in the pathogenesis of neurodegenerative disorders, such as Parkinson's disease....
α-Synuclein is an intrinsically disordered protein that plays a critical role in the pathogenesis of neurodegenerative disorders, such as Parkinson's disease. Proteomics studies of human brain samples have associated the modification of the O-linked -acetyl-glucosamine (O-GlcNAc) to several synucleinopathies; in particular, the position of the O-GlcNAc can regulate protein aggregation and subsequent cell toxicity. There is a need for site specific O-GlcNAc α-synuclein screening tools to direct better therapeutic strategies. In the present work, for the first time, the potential of fast, high-resolution trapped ion mobility spectrometry (TIMS) preseparation in tandem with mass spectrometry assisted by an electromagnetostatic (EMS) cell, capable of electron capture dissociation (ECD), and ultraviolet photodissociation (213 nm UVPD) is illustrated for the characterization of α-synuclein positional glycoforms: T72, T75, T81, and S87 modified with a single O-GlcNAc. Top-down 213 nm UVPD and ECD MS/MS experiments of the intact proteoforms showed specific product ions for each α-synuclein glycoforms associated with the O-GlcNAc position with a sequence coverage of ∼68 and ∼82%, respectively. TIMS-MS profiles of α-synuclein and the four glycoforms exhibited large structural heterogeneity and signature patterns across the 8+-15+ charge state distribution; however, while the α-synuclein positional glycoforms showed signature mobility profiles, they were only partially separated in the mobility domain. Moreover, a middle-down approach based on the Val40-Phe94 (55 residues) chymotrypsin proteolytic product using tandem TIMS-q-ECD-TOF MS/MS permitted the separation of the parent positional isomeric glycoforms. The ECD fragmentation of the ion mobility and / separated isomeric Val40-Phe94 proteolytic peptides with single O-GlcNAc in the T72, T75, T81, and S87 positions provided the O-GlcNAc confirmation and positional assignment with a sequence coverage of ∼80%. This method enables the high-throughput screening of positional glycoforms and further enhances the structural mass spectrometry toolbox with fast, high-resolution mobility separations and 213 nm UVPD and ECD fragmentation capabilities.
Topics: Humans; alpha-Synuclein; Tandem Mass Spectrometry; Parkinson Disease; Peptides; Proteolysis; Peptide Hydrolases
PubMed: 38047498
DOI: 10.1021/acs.analchem.3c02405 -
Parkinsonism & Related Disorders May 2024These facts argue against the gain-of-function synucleinopathy hypothesis, which proposes that Lewy pathology causes Parkinson's disease: (1) most brains from people... (Review)
Review
These facts argue against the gain-of-function synucleinopathy hypothesis, which proposes that Lewy pathology causes Parkinson's disease: (1) most brains from people without neurological symptoms have multiple pathologies; (2) neither pathology type nor distribution correlate with disease severity or progression in Parkinson's disease; (3) aggregated α-synuclein in the form of Lewy bodies is not a space-occupying lesion but the insoluble fraction of its precursor, soluble monomeric α-synuclein; (4) pathology spread is passive, occurring by irreversible nucleation, not active replication; and (5) low cerebrospinal fluid α-synuclein levels predict brain atrophy and clinical disease progression. The transformation of α-synuclein into Lewy pathology may occur as a response to biological, toxic, or infectious stressors whose persistence perpetuates the nucleation process, depleting normal α-synuclein and eventually leading to Parkinson's symptoms from neuronal death. We propose testing the loss-of-function synucleinopenia hypothesis by evaluating the clinical and neurodegenerative rescue effect of replenishing the levels of monomeric α-synuclein.
Topics: Animals; Humans; alpha-Synuclein; Brain; Lewy Bodies; Parkinson Disease; Synucleinopathies
PubMed: 38461037
DOI: 10.1016/j.parkreldis.2024.106077