Dynamic reversibility of α‐synuclein serine‐129 phosphorylation is impaired in synucleinopathy models

Abstract

Abstractα‐Synuclein phosphorylation at serine‐129 (pS129) is a widely used surrogate marker of pathology in Parkinson's disease and other synucleinopathies. However, we recently demonstrated that phosphorylation of S129 is also a physiological activator of synaptic transmission. In a feed‐forward fashion, neuronal activity triggers reversible pS129. Here, we show that Parkinson's disease‐linked missense mutations in SNCA impact activity‐dependent pS129. Under basal conditions, cytosol‐enriched A30P, H50Q, and G51D mutant forms of α‐synuclein exhibit reduced pS129 levels in rat primary cortical neurons. A53T pS129 levels are similar to wild‐type, and E46K pS129 levels are higher. A30P and E46K mutants show impaired reversibility of pS129 after stimulation. For the engineered profoundly membrane‐associated α‐synuclein mutant “3K” (E35K + E46K + E61K), de‐phosphorylation was virtually absent after blocking stimulation, implying that reversible pS129 is severely compromised. Importantly, pS129 excess resulting from proteasome inhibition is also associated with reduced reversibility by neuronal inhibition, kinase inhibition, or phosphatase activation. Our findings suggest that perturbed pS129 dynamics are probably a shared characteristic of pathology‐associated α‐synuclein, with possible implications for synucleinopathy treatment and diagnosis.

α-Synuclein serine129 phosphorylation – the physiology of pathology

“…The reality may be more complicated: compared to WT αS, the reversibility of activity-triggered pS129 is reduced for both E46K and A30P, indicating protein dyshomeostasis in both mutants. In addition, proteasomal inhibition also increases pS129, similar to neuronal activity, but with reduced reversibility [10]. More work is needed to establish and understand physiological vs. pathological pS129 (Fig.…”

“…Several lines of evidence, in our view, support the occurrence of physiological pS129 (in addition to the widely documented pathological pS129 associated with αS aggregates). In a recent publication [10], we systematically studied effects of familial PD (fPD) αS missense mutations on basal pS129 in cultured αS knock-out rat neurons. The cultures were transduced with human αS WT, A30P, E46K, H50Q, G51D and A53T.…”