Objective: This study aims to investigate the role of karyopherin abnormalities in the onset and progression of synucleinopathies.

Background: Despite differences in clinical manifestations, Parkinson’s Disease (PD), Dementia with Lewy Bodies (DLB), and Parkinson’s Disease Dementia (PDD) are all characterised by the accumulation of alpha-synuclein (aSyn), which are therefore called synucleinopathies. aSyn is an intrinsically disordered protein prone to liquid-liquid phase separation (LLPS) from soluble monomers to irreversible aggregates that deposit as Lewy Bodies. Previous studies showed that LLPS is associated with nuclear transport receptors called karyopherins which can act as disaggregases against misfolding proteins. Moreover, karyopherin abnormalities and aSyn have been implicated in synucleinopathies, but the role of karyopherins in disease formation remains enigmatic.

Method: Using a multi-disciplinary approach, we characterised the levels and localisations of karyopherins and aSyn in human post-mortem brain tissue of Healthy Controls (HC) and patient samples of PD, DLB, and PDD. Furthermore, we used human differentiated SH-SY5Y cells and Drosophila to model the accumulation of wildtype and mutant aSyn and established its effects on the levels and localisation of karyopherins.

Results: Here we report the nuclear accumulation of monomeric and aggregated forms of aSyn in the prefrontal cortex BA9 of PD, PDD and DLB but not in HC. Karyopherin alpha 3 (KPNA3) colocalised with aSyn in the nucleus of synucleinopathies but not in HC, accompanied by cytoplasmic depletion and nuclear accumulation of KPNA3. Proteomics analysis and quantitative Western Blotting of BA9 tissue identified karyopherin alterations in PD, DLB and PDD but not in HC or AD cases. Drosophila and SH-SY5Y cell culture experiments further demonstrated that accumulating aSyn caused downregulation and mislocalisation of KPNA3 and progressive motor impairment in Drosophila, that were exacerbated by A30P mutant aSyn. Moreover, SH-SY5Y cell experiments revealed that A30P mutant aSyn formed spontaneous intracellular aggregates which sequestered and mislocalised KPNA3, a pathogenic process that was accelerated in the presence of prefibrillar aSyn.

Conclusion: Our findings establish the pathological accumulation of nuclear aSyn and KPNA3 alterations in PD, PDD and DLB, suggesting a vicious cycle of disaggregase function that propagates protein aggregation in synucleinopathies.

« Back to 2023 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/a-vicious-cycle-of-karyopherin-abnormalities-in-synucleinopathies/