Targeted degradation of alpha-synuclein impedes PFF-induced aggregation

Rebalancing α-Synuclein Clearance: Novel Therapeutic Frontiers in Parkinson’s Disease

Aquaporin-4 mis-localization decreases glymphatic clearance of α-synuclein in an alpha-syntrophin knock out mouse model and promotes α-synuclein pathology and aggregate propagation.

The appearance of misfolded and aggregated proteins is a pathological hallmark of numerous neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. Sleep disruption is proposed to contribute to these pathological processes and is a common early feature among neurodegenerative disorders. Synucleinopathies are a subclass of neurodegenerative conditions defined by the presence of α-synuclein aggregates, which may not only enhance cell death but also contribute to disease progression by seeding the formation of additional aggregates in neighbouring cells. The mechanisms driving intercellular transmission of aggregates remain unclear. We propose that disruption of sleep-active glymphatic function, caused by loss of precise perivascular aquaporin-4 localization, inhibits α-synuclein clearance and facilitates α-synuclein propagation and seeding. We examined human post-mortem frontal cortex and found that neocortical α-synuclein pathology was associated with aquaporin-4 mis-localization throughout the grey matter. Using a transgenic mouse model lacking the adapter protein α-syntrophin, we observed that loss of perivascular aquaporin-4 localization impairs the glymphatic clearance of α-synuclein from intersititial to cerebrospinal fluid. Using a mouse model of α-synuclein propagation using pre-formed fibril injection, we observed that loss of perivascular aquaporin-4 localization increased α-synuclein aggregates. Our results indicate α-synuclein clearance and propagation are mediated by glymphatic function and that aquaporin-4 mis-localization observed in the presence of human synucleinopathy may contribute to the development and propagation of Lewy body pathology in conditions such as Lewy body dementia and Parkinson's disease.

Seed amplification of released alpha-synuclein strains reveals genotype-specific differences in Parkinson’s disease neurons

Parkinson’s disease is one of a group of diseases collectively termed α-synucleinopathies, all of which are characterized by abnormal accumulation of toxic α-synuclein (α-syn) assemblies which are thought to follow a prion-like propagation model and drive neuronal death. Both intrinsic strain properties and the genetic background of affected individuals are hypothesized to influence α-syn aggregate accumulation, propagation, and extracellular release. As such, the aim of this study is to characterize how different genetic backgrounds modulate α-syn aggregate accumulation and release in response to treatment with different α-syn strains. iPSC-derived neurons from five different groups were employed (healthy non-PD controls (NPC), idiopathic PD (iPD), GBA1 N370S, LRRK2 G2019S and SNCA A53T) ( n = 15 cell lines, three lines per group). Individual aggregates in conditioned medium (CM) were measured using a single-particle detection system to quantify released α-syn species and assess strain persistence across genotype groups. Seed amplification assay (SAA) was then applied and linear discriminant analysis (LDA) of single particle properties from CM of α-syn fibril-treated neurons was used to discriminate between groups. α-Syn released into CM showed strain persistence in LRRK2 G2019S and GBA1 N370S genotype groups, while SNCA A53T neurons exhibited evidence of strain remodeling. Interestingly, amplification-response Δ-feature analysis of single particle properties showed group discrimination beyond either pre- or post- amplification measurements independently, reaching a maximum LOO-CV accuracy of 66.7% (3.3 × chance level) at day 10 post-treatment in CM from fibrils-treated neurons. These findings indicate that genotype-specific cellular responses differentially shape the structural properties of released α-syn in a manner that determines amplification responses, enabling inter-group discrimination at the single-molecule level.

Translational Insights into α-Synuclein Aggregation and Proteostasis Dysfunction in Parkinson’s Disease

This review focuses on translational insights linking α-syn pathology to dysregulated stress-response and protein quality-control pathways, intending to identify potential targets for disease-modifying intervention.

Structural basis of α-synuclein and DJ-1 complex.

The structure of α-synuclein is predominantly α-helical when bound to cellular membranes. However, under pathological or destabilizing conditions, this α-helical structure transitions into β-sheet-rich conformations, promoting protein aggregation and formation of Lewy bodies (LBs) in neurodegenerative disorders such as Parkinson's disease dementia (PDD), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), and Alzheimer's disease (AD). DJ-1 is a multifunctional brain protein acting as a chaperone or protease under oxidative stress and associating with abnormal protein aggregates. Although previous studies suggested DJ-1 inhibits α-synuclein aggregation, the structural basis remained elusive. Here, we elucidate the direct interaction between α-synuclein and DJ-1 using size-exclusion chromatography (SEC), fluorescence spectroscopy, and multi-angle light scattering (MALS), and determined their crystal structure by X-ray diffraction. The interaction interface was mapped to residues Q24, E28, A29, and N65 of α-synuclein and K148, N173, and Q180 of DJ-1, with Q180 forming strong hydrogen bonds (2.60-2.97 Å) with α-synuclein. Transmission electron microscopy (TEM) demonstrated DJ-1 suppresses α-synuclein fibril formation. Based on the structure, we designed a DJ-1-derived peptide (173-180) that significantly inhibited α-synuclein aggregation in TEM and ELISA assays, suggesting its potential as a therapeutic candidate for α-synucleinopathies.

Aβ42-Driven α-synuclein Fibril Polymorphism and Distinct Intracellular Aggregation