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Updated: Jun 28, 2025
Author Spotlight: Establishing a New Fluorescence-Based Protocol for In Vivo Mitochondrial Morphology Analysis in Parkinson's Disease
Published on: June 23, 2023
Elevated α-synuclein levels inhibit mitophagic flux
Inge Kinnart1, Liselot Manders1, Thibaut Heyninck1
1Department of Neurosciences, Laboratory for Parkinson Research, KU Leuven, Leuven, Belgium.
Abstract:
The pathogenic effect of SNCA gene multiplications indicates that elevation of wild-type α-synuclein levels is sufficient to cause Parkinson's disease (PD). Mitochondria have been proposed to be a major target of α-synuclein-induced damage. PINK1/parkin/DJ-1-mediated mitophagy is a defense strategy that allows cells to selectively eliminate severely damaged mitochondria. Here, we quantified mitophagic flux and non-mitochondrial autophagic flux in three models of increased α-synuclein expression: 1/Drosophila melanogaster that transgenically express human wild-type and mutant α-synuclein in flight muscle; 2/human skin fibroblasts transfected with α-synuclein or β-synuclein; and 3/human induced pluripotent stem cell (iPSC)-derived neurons carrying an extra copy of wild-type SNCA under control of a doxycycline-inducible promoter, allowing titratable α-synuclein upregulation. In each model, elevated α-synuclein levels potently suppressed mitophagic flux, while non-mitochondrial autophagy was preserved. In human neurons, a twofold increase in wild-type α-synuclein was already sufficient to induce this effect. PINK1 and parkin activation and mitochondrial translocation of DJ-1 after mitochondrial depolarization were not affected by α-synuclein upregulation. Overexpression of the actin-severing protein cofilin or treatment with CK666, an inhibitor of the actin-related protein 2/3 (Arp2/3) complex, rescued mitophagy in neurons with increased α-synuclein, suggesting that excessive actin network stabilization mediated the mitophagy defect. In conclusion, elevated α-synuclein levels inhibit mitophagic flux. Disruption of actin dynamics may play a key role in this effect.
Insights
Elevated alpha-synuclein (α-synuclein) levels impair mitophagy, a cellular process for clearing damaged mitochondria, contributing to Parkinson's disease (PD). This disruption is linked to altered actin dynamics, not impaired PINK1/parkin signaling.
Area of Science:
- Neuroscience
- Cell Biology
- Genetics
Background:
- Parkinson's disease (PD) is linked to alpha-synuclein (α-synuclein) gene multiplications, suggesting elevated α-synuclein causes PD.
- Mitochondria are implicated as a key target of α-synuclein-induced cellular damage.
- Mitophagy, mediated by PINK1/parkin/DJ-1, is a critical cellular defense for removing damaged mitochondria.
Purpose of the Study:
- To investigate the impact of elevated α-synuclein levels on mitophagic flux and non-mitochondrial autophagy.
- To determine if α-synuclein affects the PINK1/parkin/DJ-1 mitophagy pathway.
- To explore the role of actin dynamics in α-synuclein-induced mitophagy defects.
Main Methods:
- Quantification of mitophagic and non-mitochondrial autophagic flux in three distinct models: Drosophila melanogaster, human skin fibroblasts, and human induced pluripotent stem cell (iPSC)-derived neurons.
- Transgenic expression and transfection of wild-type and mutant α-synuclein, as well as β-synuclein.
- Doxycycline-inducible upregulation of wild-type SNCA in iPSC-derived neurons.
Main Results:
- Elevated α-synuclein levels significantly suppressed mitophagic flux across all three models, while non-mitochondrial autophagy remained unaffected.
- A twofold increase in wild-type α-synuclein in human neurons was sufficient to induce mitophagy suppression.
- PINK1/parkin activation and DJ-1 mitochondrial translocation were not impaired by α-synuclein upregulation.
- Overexpression of cofilin or inhibition of the Arp2/3 complex rescued mitophagy, indicating excessive actin network stabilization mediates the defect.
Conclusions:
- Elevated α-synuclein levels potently inhibit mitophagic flux, a crucial process in Parkinson's disease pathogenesis.
- The observed mitophagy defect is mediated by disruptions in actin dynamics, specifically excessive actin network stabilization.
- Targeting actin dynamics may offer a novel therapeutic strategy for Parkinson's disease associated with α-synucleinopathies.
