The Importance of the Fibril Fuzzy Coat for α-Synuclein Pathological Transmission Activity

Neurology Medicine
α-synuclein pathological transmission fibril fuzzy coat neurodegenerative diseases therapeutic target

Academic Background

Neurodegenerative diseases, such as Parkinson’s disease (PD) and Alzheimer’s disease (AD), are often accompanied by abnormal aggregation and propagation of pathological proteins. The abnormal aggregation of α-synuclein is a central pathological feature of Parkinson’s disease and other synucleinopathies. Although extensive research has revealed the relationship between the core structure of α-synuclein fibrils and their pathological transmission capabilities, the role of the outer “fuzzy coat” region of the fibrils in pathological transmission remains unclear. This fuzzy coat, composed of the N- and C-termini of the protein, is highly flexible, making it difficult to capture its detailed structure using traditional structural analysis techniques. Therefore, the authors aimed to explore the specific role of the fuzzy outer layer of α-synuclein fibrils in pathological transmission and reveal its underlying molecular mechanisms.

Source of the Paper

This study was conducted by Yuliang Han, Juan Li, Wencheng Xia, and other researchers from renowned institutions such as the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, the University of Science and Technology of China, and the University of Pennsylvania. The paper was published on June 4, 2025, in the journal Neuron, titled “Fibril Fuzzy Coat is Important for α-Synuclein Pathological Transmission Activity.”

Research Process

1. Preparation and Fibrillation of the Research Object

The study began with the preparation of α-synuclein preformed fibrils (PFFs) through in vitro fibrillation experiments. Specific steps included shaking α-synuclein monomers for 5 days to form initial fibrils (P1), followed by high-speed centrifugation to isolate the fibrils. The P1 fibrils were then mixed with fresh monomers for multiple rounds of amplification, ultimately yielding P2 to P8 fibrils.

2. Evaluation of Fibril Pathological Transmission Capability

By inoculating different rounds of fibrils (P1 to P8) into primary neurons of wild-type mice, the researchers found that the pathological transmission capability of the fibrils gradually decreased with increasing rounds of amplification. This phenomenon was validated in vivo: injecting P1 and P8 fibrils into the hippocampus of mice revealed that P1 fibrils induced significantly more pathological changes than P8 fibrils after 3 months.

3. Separation and Identification of Fibril Polymorphs

The study discovered two distinct polymorphic fibrils in P1 fibrils: mini-p and mini-s. Mini-p fibrils exhibited higher neuronal transmission activity, while mini-s fibrils accelerated the aggregation of recombinant α-synuclein. Using cryo-electron microscopy (cryo-EM) and solid-state nuclear magnetic resonance (ssNMR) techniques, the researchers found that although the core structures of mini-p and mini-s fibrils were similar, their fuzzy outer layers exhibited significant differences in flexibility.

4. Interaction of Fibrils with Neuronal Receptors

Further research revealed that mini-p fibrils were more readily taken up by neurons and were more resistant to protease degradation. Through biolayer interferometry (BLI) experiments, the researchers found that mini-p fibrils had significantly higher binding affinity to the neuronal receptor HSPG (heparan sulfate proteoglycan) compared to mini-s fibrils.

5. Interaction Between the Fuzzy Coat and Core Region

Using hydrogen/deuterium exchange mass spectrometry (HDX-MS), the researchers discovered that the C-terminal fuzzy coat of mini-p fibrils interacted more closely with the core region, resulting in reduced flexibility of the fuzzy coat. This finding explained why mini-p fibrils were more prone to forming aggregates and exhibited higher pathological transmission capabilities.

6. Antibody Inhibition Experiments

The researchers also developed specific antibodies targeting mini-p fibrils and found that these antibodies effectively inhibited the pathological transmission activity of mini-p fibrils, further validating the critical role of the fuzzy coat in pathological transmission.

Main Results

  1. Decline in Fibril Transmission Capability: The pathological transmission capability of α-synuclein fibrils gradually decreased with increasing rounds of amplification, a phenomenon validated in both in vitro and in vivo experiments.
  2. Discovery of Fibril Polymorphs: Two polymorphic fibrils (mini-p and mini-s) were identified in P1 fibrils, with mini-p fibrils exhibiting higher neuronal transmission activity and mini-s fibrils accelerating the aggregation of recombinant α-synuclein.
  3. Flexibility Differences in the Fuzzy Coat: The core structures of mini-p and mini-s fibrils were similar, but their fuzzy outer layers exhibited significant differences in flexibility, with the fuzzy coat of mini-p fibrils interacting more closely with the core region.
  4. Neuronal Uptake and Protease Resistance: Mini-p fibrils were more readily taken up by neurons and were more resistant to protease degradation, contributing to their higher pathological transmission capability.
  5. Antibody Inhibition Efficacy: Specific antibodies targeting mini-p fibrils effectively inhibited their pathological transmission activity, providing new insights for future therapeutic strategies.

Conclusion and Significance

This study is the first to reveal the critical role of the fuzzy outer layer of α-synuclein fibrils in pathological transmission and elucidate its molecular mechanisms. The findings indicate that the flexibility of the fuzzy coat and its interaction with the core region are key factors determining the pathological transmission capability of fibrils. This discovery not only provides new perspectives for understanding the pathological transmission mechanisms of neurodegenerative diseases but also offers potential therapeutic targets for interventions targeting the fuzzy coat. Additionally, the development of specific antibodies provides new tools for future disease interventions.

Research Highlights

  1. First to Reveal the Role of the Fuzzy Coat: This study is the first to systematically explore the role of the fuzzy outer layer of α-synuclein fibrils in pathological transmission, filling a research gap in this field.
  2. Multidisciplinary Research Approach: The study combined advanced techniques such as cryo-EM, ssNMR, and HDX-MS to comprehensively analyze the structure and function of fibrils.
  3. Development of Specific Antibodies: The study developed specific antibodies targeting mini-p fibrils, providing new tools for future therapeutic strategies.
  4. Potential Therapeutic Target: The fuzzy coat serves as a new therapeutic target, offering new directions for interventions in neurodegenerative diseases.

Other Valuable Information

The study also found that negatively charged residues in the fuzzy coat play an important role in fibril self-aggregation and neuronal uptake. By altering the pH of the fibrillation reaction or mutating the negatively charged residues in the fuzzy coat, the researchers were able to regulate the aggregation behavior and pathological transmission capability of the fibrils. This discovery provides new directions for future drug design and disease interventions.

This study not only deepens our understanding of the pathological transmission mechanisms of α-synuclein but also provides new insights and tools for the treatment of neurodegenerative diseases.