Phosphorylation by the c-Abl protein tyrosine kinase inhibits parkin's ubiquitination and protective function

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Mutations in PARK2/Parkin cause autosomal recessive Parkinson disease (PD).
• Parkin functions as a ubiquitin E3 ligase, crucial for neuronal protection.
• Dopaminergic stress and toxins activate c-Abl kinase.

Purpose of the Study:

• To investigate the role of c-Abl in regulating parkin activity.
• To determine if c-Abl-mediated parkin inhibition contributes to Parkinson disease pathogenesis.
• To explore c-Abl inhibition as a potential therapeutic strategy for PD.

Main Methods:

• In vitro and in vivo experiments using dopaminergic neurotoxins (MPP(+), MPTP).
• Analysis of parkin phosphorylation and activity.
• Assessment of parkin substrates (AIMP2, FBP1) accumulation.
• Pharmacological inhibition of c-Abl using STI-571.
• Gene silencing (shRNA knockdown) and conditional knockout of c-Abl.
• Examination of human postmortem PD brain tissue.

Main Results:

• c-Abl phosphorylates parkin at tyrosine 143, inhibiting its E3 ligase activity.
• Dopaminergic stress activates c-Abl, leading to parkin inactivation.
• Parkin inactivation results in accumulation of substrates AIMP2 and FBP1, causing cell death.
• STI-571 prevents parkin phosphorylation and protects neurons; this effect requires parkin.
• Conditional c-Abl knockout prevents MPTP-induced neurotoxicity.
• Human PD brains show active c-Abl, phosphorylated parkin, and accumulated substrates.

Conclusions:

• Tyrosine phosphorylation of parkin by c-Abl is a key inhibitory mechanism.
• This pathway contributes to Parkinson disease pathogenesis, potentially including sporadic PD.
• Inhibition of c-Abl represents a promising neuroprotective therapeutic approach for Parkinson disease.