Parkinson's disease (PD) affects over 12 million people worldwide and has the fastest-growing global impact. The pathological hallmark is the presence of Lewy bodies and Lewy neurites, which are intraneuronal lesions enriched in aggregated alpha-synuclein (αS) that is typically hyper-phosphorylated at serine 129. Therefore, lowering phosphoserine 129 (pS129) may be a viable therapeutic strategy to treat PD. However, pS129 has also been proposed to regulate synaptic transmission and αS degradation. In both cases, inhibiting pS129 could be detrimental. Here, we developed a sensitive assay in a human neuroblastoma model and utilized it to assess the relative expression levels and cytotoxicity of pS129 by comparing wild-type (WT) vs. S129A (pS129-deficient). We show that the S129A mutant does not affect the acute expression levels or toxicity of αS in this transient transfection paradigm. This provides new insight into the intricate interplay between αS, phosphorylation, toxicity, and degradation. Our assay provides a versatile platform for understanding disease-relevant mechanisms and opens novel avenues for the design of future therapeutic interventions in PD and other α-synucleinopathies.
Li et al. (2025) studied this question.