Endogenous Rab38 regulates LRRK2's membrane recruitment and substrate Rab phosphorylation in melanocytes

Area of Science:

• Cell Biology
• Neuroscience
• Genetics

Background:

• Point mutations in leucine-rich repeat kinase 2 (LRRK2) are linked to Parkinson's disease, increasing its kinase activity.
• Endogenous cellular pathways that physiologically enhance LRRK2 kinase function remain largely unidentified.
• While Rab29 can recruit LRRK2 to Golgi membranes when overexpressed, its role in endogenous LRRK2 regulation is unclear.

Purpose of the Study:

• To identify novel physiological regulators of LRRK2 kinase activity in melanocytes.
• To investigate the role of Rab GTPases, specifically Rab38, Rab32, and Rab29, in modulating LRRK2 function.
• To elucidate the mechanism by which Rab38 influences LRRK2 localization and activity.

Main Methods:

• Knockdown and CRISPR knockout of Rab38, Rab32, and Rab29 in mouse melanocytes.
• Assessment of LRRK2 substrate phosphorylation (e.g., Rab10, Rab12) using Western blotting.
• Analysis of LRRK2 membrane association and pericentriolar recruitment in B16-F10 melanoma cells.
• Investigation of the role of BLOC-3 (guanine nucleotide exchange factor) and LRRK2's Rab38-binding site.

Main Results:

• Knockdown of Rab38, but not Rab32 or Rab29, significantly decreased LRRK2 substrate phosphorylation in mouse melanocytes.
• Rab38 was found to drive LRRK2 membrane association and pericentriolar recruitment in melanoma cells.
• This LRRK2 recruitment by Rab38 was dependent on the presence of endogenous Rab38 and BLOC-3.
• Disruption of the LRRK2 Rab38-binding site impaired LRRK2 membrane association and phosphorylation activity.

Conclusions:

• Rab38 is identified as a novel physiological regulator of LRRK2 kinase activity in melanocytes.
• LRRK2 plays a significant role in coordinating Rab GTPase function in vesicular trafficking.
• These findings provide insights into the molecular mechanisms underlying LRRK2 regulation in health and Parkinson's disease.