INTRODUCTION: Parkinson’s disease (PD) is the second most common neurodegenerative disorder, characterized by motor symptoms such as rigidity and bradykinesia, which occur after the loss of approximately 50% of dopaminergic neurons in the SN/VTA region. This neuronal loss is a slow, progressive process that begins years before the onset of motor symptoms. Currently, no available treatment can halt this progression, and a lack of understanding of the mechanisms potentially responsible for neurodegeneration in PD hinders the development of effective therapies. The pathological aggregation and prion-like spreading of misfolded α-synuclein, and the formation of Lewy bodies, are considered key mechanisms. Therefore, elucidating the molecular mechanisms behind α-synuclein aggregation and its clearance may reveal promising therapeutic targets.

AIM(S): We aimed to examine the role of disruption of the endolysosomal pathway (ELP) in pathological α-synuclein aggregation and cell survival.

METHOD(S): We utilized an α-synuclein preformed fibrils (PFF) in vitro model in primary neuronal cultures. Disruption of the ELP was achieved by increasing endolysosomal pH using chloroquine (CQ; 5 μM, 10 μM, 12.5 μM). Additionally, we applied CRISPR-Cas9-mediated deletion of the lysosomal ion channel TMEM175, responsible for maintaining optimal lysosomal pH. Immunofluorescence staining for pS129-α-synuclein-positive aggregates and NeuN was used for analysis.

RESULTS: As expected, CQ at 10 μM and 12.5 μM decreased neuronal survival and impaired degradation of α-synuclein aggregates. Interestingly, 5 μM CQ showed potential neuroprotective effects. Surprisingly, TMEM175 ablation reduced the accumulation of pathological α-synuclein threefold.

CONCLUSIONS: The ELP appears to be an important factor in α-synuclein aggregation; however, the role of TMEM175 is complex and requires further investigation.

FINANCIAL SUPPORT: Funding: This research was funded by the National Science Centre, Poland (grant no. 2019/35/D/N27/03200, Sonata 15).