Targeting Specific Kinase Substrates Rescues Increased Colitis Severity Induced by the Crohn's Disease-Linked...

Area of Science:

• Genetics and Molecular Biology
• Immunology
• Gastroenterology

Background:

• The Leucine-Rich Repeat Kinase 2 (LRRK2) gene harbors variants associated with distinct diseases, including Crohn's disease (CD) risk (N2081D) and Parkinson's disease (PD) pathogenesis (G2019S).
• The precise mechanisms by which the LRRK2 N2081D variant contributes to CD pathogenesis and how adjacent mutations lead to different diseases remain poorly understood.

Purpose of the Study:

• To investigate the pathophysiological mechanisms of the CD-associated LRRK2 N2081D variant.
• To compare the effects of the LRRK2 N2081D variant with the well-characterized LRRK2 G2019S mutation using a mouse model.

Main Methods:

• Generation of a knock-in (KI) mouse model expressing the LRRK2 N2081D variant (Lrrk2^2081 KI).
• Comparison of Lrrk2^2081 KI mice with LRRK2 G2019S KI and wild-type mice in induced colitis models.
• Analysis of colonic tissue, cellular LRRK2 activity, RAB substrate phosphorylation (specifically RAB10), and inflammatory responses in dendritic cells; assessment of therapeutic interventions including Rab12 knockout and LRRK2 kinase inhibition.

Main Results:

• Lrrk2^2081 KI mice exhibited heightened sensitivity to induced colitis, with increased intestinal inflammation and damage compared to controls.
• Distinct mutation-dependent LRRK2 substrate phosphorylation was observed, with significantly elevated levels of phosphorylated RAB10 in Lrrk2^2081 KI mice.
• The N2081D mutation activates LRRK2 via a distinct mechanism compared to G2019S, and this activation is further enhanced by proinflammatory stimuli, leading to differential RAB phosphorylation and inflammatory responses in dendritic cells. Genetic knockout of Rab12, but not LRRK2 kinase inhibition, attenuated colitis severity in Lrrk2^2081 KI mice.

Conclusions:

• This study elucidates the pathogenic mechanisms linking LRRK2 N2081D to Crohn's disease.
• Significant structural and functional differences exist between disease-associated LRRK2 variants (N2081D and G2019S).
• RAB proteins, particularly RAB10 and RAB12, represent promising therapeutic targets for LRRK2-mediated inflammatory diseases like Crohn's disease.