Neurodegenerative diseases represent the most common cause of dementia. Protein aggregation is upstream in the pathological mechanisms and is a therapeutic target in the development of disease-modifying drugs in this patient population. Notably, α-synuclein or DNA-binding protein of 43kDa (TDP-43) is commonly involved in the pathomechanisms that contribute to non-Alzheimer neurodegenerative diseases. Several immunotherapy clinical trials on α-synuclein have progressed to phase 2, and small-molecule therapeutics are ongoing. With regard to TDP-43, immunotherapies that target protein aggregates are currently being developed, and research is underway to investigate several drugs that target the associated causative gene. Further research is warranted for deeper insight into both disease-modifying drugs; biomarker tests need to be developed to determine their efficacy. However, both proteins aggregate and accumulate in the brain in many neurodegenerative diseases and dementia; therefore, they are therapeutically significant, and future progress is expected in research and development.

BACKGROUND: Alpha-synuclein (αSyn) is believed to play a central role in the pathogenesis of Parkinson\'s disease (PD). Cerebrospinal fluid (CSF) total αSyn were significantly lower in PD patients, whereas the aggregates were higher, and this phenomenon was further exacerbated with longer disease duration. However, whether CSF αSyn can be the cause and/or a consequence in PD is not fully elucidated.
METHODS: We administered 2 ng or 200 ng αSyn preformed fibrils (PFFs) by intracerebroventricular injection for consecutive 7 days in C57BL/6 mice. The olfactory function was assessed by the olfactory discrimination test and buried food-seeking test. The locomotor function was assessed by the rotarod test, pole test, open field test and CatWalk gait analysis. Phosphorylated αSyn at serine 129 was detected by the immunohistochemistry staining. Iron levels was determined by Perl\'s-DAB iron staining and synchrotron-based X-ray fluorescence.
RESULTS: The mice did not exhibit any diffuse synucleinopathy in the brain for up to 30 weeks, although αSyn PFFs induced aggregation in SH-SY5Y cells and in the substantia nigra and striatum of mice with stereotactic injection. No impairment of motor behaviors or olfactory functions were observed, although there was a temporary motor enhancement at 1 week. We then demonstrated iron levels were comparable in certain brain regions, suggesting there was no iron deposition/redistribution occurred.
CONCLUSIONS: The intraventricular injection of αSyn PFFs does not induce synucleinopathy or behavioral symptoms. These findings have implications that CSF αSyn aggregates may not necessarily contribute to the onset or progression in PD.

BACKGROUND: Parkinson\'s disease (PD), the most prevalent type of Parkinsonism, is a progressive neurological condition characterized by a range of motor and non-motor symptoms. The complicated etiology of PD is thought to involve a summation of aging, genetic predisposition, and environmental variables. However, the α-synuclein protein plays a significant role in the disease\'s pathophysiology.
METHODS: The UAS-α-Syn and Ddc-Gal4 strains were crossed to produce offspring referred to as PD flies. The entire population of flies was divided into five groups, each having about 100 flies and five replicates. The control group (w1118) and the PD group not receiving treatment were exposed to lauric acid (LA)/levodopa (LD)-free diet, while the PD groups that received treatments were fed with either a 250 mg/kg LA diet, a 250 mg/kg LD diet, or a combination of the two for 21 days. Longevity, geotaxis, and olfactory assays were performed in addition to other biochemical tests.
RESULTS: As a result of the overexpression of α-synuclein, the locomotive capacity, lifespan, and antioxidant status were all significantly (p < .05) reduced, and the apoptotic and neuroinflammatory activities were increased. Nevertheless, the majority of the treated flies improved significantly (p < .05).
CONCLUSIONS: LA, whether combined with LD or not, elicited a significant response in α-synuclein/dopa decarboxylase genetically modified Drosophila melanogaster Parkinsonism models.

BACKGROUND: GALNTs (UDP-GalNAc; polypeptide N-acetylgalactosaminyltransferases) initiate mucin-type O-GalNAc glycosylation by adding N-GalNAc to protein serine/threonine residues. Abnormalities in O-GalNAc glycosylation are involved in various disorders such as Parkinson\'s disease (PD), a neurodegenerative disorder. GALNT9 is potentially downregulated in PD patients.
METHODS: To determine whether GALNT9 enrichment ameliorates cytotoxicity related to PD-like variations, a pcDNA3.1-GALNT9 plasmid was constructed and transfected into SH-SY5Y cells to establish a GALNT9-overexpressing cell model.
RESULTS: Downregulation of GALNT9 and O-GalNAc glycosylation was confirmed in our animal and cellular models of PD-like variations. GALNT9 supplementation greatly attenuated cytotoxicity induced by MPP+ (1-Methyl-4-phenylpyridinium iodide) since it led to increased levels of tyrosine hydroxylase and dopamine, reduced rates of apoptosis, and significantly ameliorated MPP+-induced mitochondrial dysfunction by alleviating abnormal levels of mitochondrial membrane potential and reactive oxygen species. A long-lasting mPTP (mitochondrial permeability transition pores) opening and calcium efflux resulted in significantly lower activity in the cytochrome C-associated apoptotic pathway and mitophagy process, signifying that GALNT9 supplementation maintained neuronal cell health under MPP+ exposure. Additionally, it was found that glycans linked to proteins influenced the formation of protein aggregates containing α-synuclein, and GALNT9 supplement dramatically reduced such insoluble protein aggregations under MPP+ treatment. Glial GALNT9 predominantly appears under pathological conditions like PD-like variations.
CONCLUSIONS: GALNT9 enrichment improved cell survival, and glial GALNT9 potentially represents a pathogenic index for PD patients. This study provides insights into the development of therapeutic strategies for the treatment of PD.

The aggregation of the protein α-synuclein into amyloid deposits is associated with multiple neurological disorders, including Parkinson\'s disease. Soluble amyloid oligomers are reported to exhibit higher toxicity than insoluble amyloid fibrils, with dimers being the smallest toxic oligomer. Small molecule drugs, such as fasudil, have shown potential in targeting α-synuclein aggregation and reducing its toxicity. In this study, we use atomistic molecular dynamics simulations to demonstrate how fasudil affects the earliest stage of aggregation, namely dimerization. Our results show that the presence of fasudil reduces the propensity for intermolecular contact formation between protein chains. Consistent with previous reports, our analysis confirms that fasudil predominantly interacts with the negatively charged C-terminal region of α-synuclein. However, we also observe transient interactions with residues in the charged N-terminal and hydrophobic NAC regions. Our simulations indicate that while fasudil prominently interacts with the C-terminal region, it is the transient interactions with residues in the N-terminal and NAC regions that effectively block the formation of intermolecular contacts between protein chains and prevent early dimerization of this disordered protein.

Parkinson\'s disease (PD) is a prevalent neurodegenerative disorder, affecting around 500,000 to 1 million Americans, with a significant portion diagnosed before age 50. Despite advances in treatments such as dopamine replacement therapy and deep brain stimulation, no therapies currently exist to halt or slow disease progression in advanced stages. Research is increasingly focused on identifying early biomarkers for PD to enable earlier intervention. Alpha-synuclein (α-Syn), a key protein implicated in PD pathology, is studied using various proteomics techniques like mass spectrometry, gel electrophoresis, and chromatography, to understand its role and alterations in PD. These techniques help in extracting, analyzing, and characterizing α-Syn from brain samples, providing insights into disease mechanisms and potential diagnostic and therapeutic applications.

Alpha-synuclein (α-syn) aggregation plays a critical role in the pathogenicity of Parkinson\'s Disease (PD). This study aims to evaluate the aggregation propensity of α-syn fragment peptides designed using the variability found in humans and animals. Thioflavin T (ThT) and transmission electron microscopy (TEM) were used to validate the formation of fibrils to identify important amino acid residues. Human α-syn fragments 51-75, 37-61, 62-86, 76-100, and 116-140 demonstrate a significantly higher tendency to aggregate compared to fragments 1-25, 26-50, and 91-115. All species analyzed of the α-syn 37-61 and 62-86 regions were shown to form fibrils on both ThT and TEM. The α-syn 37-61 and 62-86 fragment regions exhibited a high susceptibility to aggregation, with fibril formation observed in all species. The A53T mutation in several α-syn 37-61 fragments may enhance their propensity for aggregation, suggesting a correlation between this mutation and the capacity for fibril formation. Furthermore, the presence of the non-amyloid-β component (NAC) region, specifically in α-syn 62-86, was consistently observed in several fragments that displayed fibril formation, indicating a potential correlation between the NAC region and the process of fibril formation in α-syn. Finally, the combination of a high quantity of valine and a low quantity of acidic amino acids in these fragments may serve as indicators of α-syn fibril formation.

BACKGROUND: Parkinson\'s disease (PD) is a neurodegenerative condition characterized by the loss of dopaminergic neurons and the accumulation of Lewy-body protein aggregates containing misfolded α-synuclein (α-syn) in a phosphorylated form. The lack of effective models for drug screens has hindered drug development studies for PD. However, the recent development of in vitro brain-like organoids provides a new opportunity for evaluating therapeutic agents to slow the progression of this chronic disease.
METHODS: In this study, we used a 3D brain-like organoid model to investigate the potential of repurposing Tilorone, an anti-viral drug, for impeding the propagation of α-synucleinopathy. We assessed the effect of Tilorone on the uptake of fluorescently labeled α-syn preformed fibrils (sPFF) and sPFF-induced apoptosis using confocal microscopy. We also examined Tilorone\'s impact on the phosphorylation of endogenous α-syn induced by pathogenic sPFF by immunoblotting midbrain-like organoid extracts. Additionally, quantitative RT-PCR and proteomic profiling of sPFF-treated organoids were conducted to evaluate the global impact of Tilorone treatment on tissue homeostasis in the 3D organoid model.
RESULTS: Tilorone inhibits the uptake of sPFF in both mouse primary neurons and human midbrain-like organoids. Tilorone also reduces the phosphorylation of endogenous α-syn induced by pathogenic α-syn fibrils and mitigates α-syn fibril-induced apoptosis in midbrain-like organoids. Proteomic profiling of fibril-treated organoids reveals substantial alterations in lipid homeostasis by α-syn fibrils, which are reversed by Tilorone treatment. Given its safety profile in clinics, Tilorone may be further developed as a therapeutic intervention to alleviate the propagation of synucleinopathy in PD patients.

In orchestrating cell signaling, facilitating plasma membrane repair, supervising protein secretion, managing waste elimination, and regulating energy consumption, lysosomes are indispensable guardians that play a crucial role in preserving intracellular homeostasis. Neurons are terminally differentiated post-mitotic cells. Neuronal function and waste elimination depend on normal lysosomal function. Converging data suggest that lysosomal dysfunction is a critical event in the etiology of Parkinson\'s disease (PD). Mutations in Glucosylceramidase Beta 1 (GBA1) and leucine-rich repeat kinase 2 (LRRK2) confer an increased risk for the development of parkinsonism. Furthermore, lysosomal dysfunction has been observed in the affected neurons of sporadic PD (sPD) patients. Given that lysosomal hydrolases actively contribute to the breakdown of impaired organelles and misfolded proteins, any compromise in lysosomal integrity could incite abnormal accumulation of proteins, including α-synuclein, the major component of Lewy bodies in PD. Clinical observations have shown that lysosomal protein levels in cerebrospinal fluid may serve as potential biomarkers for PD diagnosis and as signs of lysosomal dysfunction. In this review, we summarize the current evidence regarding lysosomal dysfunction in PD and discuss the intimate relationship between lysosomal dysfunction and pathological α-synuclein. In addition, we discuss therapeutic strategies that target lysosomes to treat PD.

We probed the mechanism by which the Parkinson\'s disease-associated protein α-synuclein (α-syn)/SNCA promotes the pathogenesis and progression of melanoma. We found that the human melanoma cell line SK-MEL-28 in which SNCA is knocked out (SNCA-KO) has low levels of tetraspanin CD81, which is a cell-surface protein that promotes invasion, migration, and immune suppression. Analyzing data from the Cancer Genome Atlas, we show that SNCA and CD81 mRNA levels are positively correlated in melanoma; melanoma survival is inversely related to the levels of SNCA and CD81; and SNCA/CD81 are inversely related to the expression of key cytokine genes (IL12A, IL12B, IFN, IFNG, PRF1 and GZMB) for immune activation and immune cell-mediated killing of melanoma cells. We propose that high levels of α-syn and CD81 in melanoma and in immune cells drive invasion and migration and in parallel cause an immunosuppressive microenvironment; these contributing factors lead to aggressive melanomas.