Abstract
Mutations that enhance LRRK2 protein kinase activity cause inherited Parkinson’s disease. LRRK2 phosphorylates a group of Rab GTPase proteins, including Rab10, within the effector-binding switch-II motif. Previous work has indicated that the PARK16 locus, which harbors the gene encoding for Rab29, is mutated in Parkinson’s, and that Rab29 operates in a common pathway with LRRK2. Co-expression of Rab29 and LRRK2 stimulates LRRK2 activity by recruiting LRRK2 to the surface of the trans-Golgi network. Pathogenic mutations including LRRK2[R1441C] promote GTP-binding are more readily activated by Rab29. As previous work was based on overexpression approaches, we were curious to define the importance of endogenous Rab29 in regulating basal LRRK2 activity. We report that knock-out of Rab29 does not influence endogenous LRRK2 activity, based on assessment of Rab10 phosphorylation, in wildtype LRRK2, LRRK2[R1441C] as well as in VPS35[D620N] knock-in mouse tissues and embryonic fibroblasts. We also generated a transgenic mouse model that moderately overexpresses Rab29, and found that this was not sufficient to stimulate basal LRRK2 activity. Our data suggest that the bulk of the basal LRRK2 activity measured in whole cell and tissue extracts is not controlled by Rab29. LRRK2 is not associated with the Golgi unless Rab29 is highly overexpressed, which could account for the lack of effect that Rab29 knock-out or moderate overexpression has on basal LRRK2 activity. Further work is required to establish how basal LRRK2 activity is regulated, and whether other Rab proteins control basal LRRK2 by targeting it to diverse membranes.
Competing Interest Statement
The authors have declared no competing interest.