DAPK1-Mediated Parkin Inactivation Enhances Neurotoxicity via MITOL-Dependent Degradation.

Parkinson's disease (PD) is characterised by progressive neurodegeneration and is marked by the formation of Lewy bodies, which are intracellular aggregates primarily composed of α-synuclein. Mitochondrial dysfunction and impaired protein degradation pathways are thought to play critical roles in PD progression, contributing to the loss of dopaminergic neurons in the substantia nigra. Phosphorylation of α-synuclein has been shown to promote its aggregation, underscoring its potential role in disease progression. Parkin, an E3 ubiquitin ligase, is widely regarded as a pleiotropic neuroprotective protein that modulates the mitochondrial quality control, as well as metabolic turnover and the accumulation of α-synuclein. Death-associated protein kinase 1 (DAPK1), which is involved in the regulation of apoptosis and autophagy, has recently emerged as an important factor in neurodegeneration. While DAPK1 has been implicated in Alzheimer's disease through its role in tau aggregation and amyloid-β production, our findings suggest that DAPK1 may also influence PD-related pathways by phosphorylating parkin at Ser136 and Ser198. This phosphorylation promotes the mitochondrial transport of parkin, enhancing interaction with mitochondria-localised E3 ubiquitin ligase MITOL and consequently leading to the degradation of parkin. Given the neuroprotective role of parkin, its reduction increases the vulnerability of neurons to 6-hydroxydopamine-induced toxicity, potentially contributing to decreased neuronal survival. Together, these findings suggest that DAPK1 functions as a previously unrecognised modulator of parkin and could potentially influence PD-related neurodegenerative processes. This pathway may provide a mechanistic link between mitochondrial dysfunction, α-synuclein pathology and neuronal cell death.