Pharmacological LRRK2 kinase inhibition induces LRRK2 protein destabilization and proteasomal degradation

Area of Science:

• Neuroscience
• Molecular Biology
• Pharmacology

Background:

• Leucine-rich repeat kinase 2 (LRRK2) kinase activity is implicated in Parkinson's disease (PD) pathogenesis, particularly with the G2019S mutation.
• LRRK2 kinase inhibitors are a promising therapeutic strategy for PD, but their precise molecular effects require further elucidation.

Purpose of the Study:

• To investigate the molecular consequences of LRRK2 kinase inhibition on LRRK2 protein levels and degradation pathways.
• To assess the impact of LRRK2 inhibition on different LRRK2 mutations and endogenous LRRK2 in various tissues.

Main Methods:

• Treatment of cells and mouse tissues with six distinct LRRK2 kinase inhibitors.
• Analysis of LRRK2 protein levels, dephosphorylation, and degradation pathways using proteasomal and lysosomal inhibitors.
• Utilized LRRK2 phosphorylation mutants (S910A, S935A) to examine the role of specific phosphorylation sites in degradation.

Main Results:

• LRRK2 kinase inhibition led to LRRK2 dephosphorylation and reduced LRRK2 protein levels in wild-type and G2019S mutants, but not A2016T or K1906M mutants.
• The reduction in LRRK2 levels was dependent on proteasomal degradation, as it was reversed by proteasomal inhibition.
• mRNA levels of LRRK2 remained unaffected, indicating post-transcriptional regulation. Dephosphorylation of S910/S935 sites was not essential for degradation.

Conclusions:

• LRRK2 kinase inhibition triggers a proteasomal degradation pathway for LRRK2, offering a potential disease-modifying mechanism for PD.
• Understanding these degradation pathways is crucial for optimizing LRRK2-targeted therapies and advancing Parkinson's disease treatment strategies.