Infection and herbicide exposure implicate c-Abl kinase in α-Synuclein Ser129 phosphorylation

Parkinson's disease is a complex, multifactorial neurodegenerative disorder characterized by aggregation of α-Synuclein into Lewy bodies, with phosphorylation at serine 129 (pSer129), serving as a key regulatory site and pathological hallmark. However, the exact mechanisms by which environmental triggers lead to this disease phenotype remain poorly understood. In this study, we investigate the impact of representative infectious and pesticide exposures on pSer129 α-Synuclein, with a particular focus on the role of cellular kinases in mediating this process.

Neuronal cells were exposed to two distinct environmental stressors: the pesticide rotenone and the well-characterized gastric bacterium Helicobacter pylori (H. pylori). Phosphorylation of Ser129 α-Synuclein and mitochondrial damage were assessed by immunofluorescence staining or Western blotting. To investigate the involvement of c-Abl, cells were treated with mechanistically distinct c-Abl inhibitors and siRNA. Levels of pSer129 α-Synuclein were quantified by Western blotting, while the activities of the upstream serine/threonine kinase were predicted by kinase profiling and validated by Western blotting. Additionally, transcriptome analyses of treated cells were performed and ingenuity pathway analysis and DESeq2 were applied to identify neurodegenerative pathways affected by the infection/treatment.

The functional analysis of our RNA-sequencing data revealed that both H. pylori and rotenone induce neuroinflammatory and cellular stress response pathways. Although they likely activate c-Abl through distinct upstream mediators, both triggers ultimately promote α-synuclein phosphorylation. Treatment with the c-Abl inhibitors, Ponatinib and Asciminib, effectively prevented the accumulation of pSer129 α-synuclein and reversed the associated gene expression changes induced by H. pylori or rotenone. Additionally, GSK3β has been identified as a contributor to Ser129 phosphorylation occurring downstream of activated c-Abl signaling. Notably, the vacuolating cytotoxin (VacA) produced by H. pylori appears to play a critical role in c-Abl-mediated phosphorylation of α-synuclein at Ser129.

These findings highlight the pivotal role of c-Abl in α-Synucleinopathies and provide insights into shared mechanisms between infection and pesticide exposure, offering potential therapeutic targets for Parkinson's disease and related pathologies involving α-Synuclein modification.