The role of RAB10 and RAB29 in endolysosomal trafficking alterations mediated by pathogenic LRRK2

Point mutations in the gene encoding the Leucine-Rich Repeat Kinase 2 (LRRK2) are the most common cause of autosomal dominant familial Parkinson’s Disease, while certain variants can also increase risk of developing sporadic PD. LRRK2 has been implicated in several cellular processes including mitochondrial function, cytoskeletal dynamics and vesicular trafficking events. The latter include endocytosis, autophagy, retromer-mediated recycling and endolysosomal trafficking pathways. The exact molecular mechanisms responsible for the LRRK2-mediated defects in these trafficking pathways remain largely unknown. A subset of the RAB family of small GTPases including RAB8A and RAB10 have been identified to act as LRRK2 substrates, and RAB29 is an important LRRK2 interacting protein. Previous work showed that pathogenic LRRK2 mediates defects in the endolysosomal degradation and recycling of the Epidermal Growth Factor Receptor (EGFR) by phosphorylating and inactivating RAB8A, which causes a decrease in RAB7A activity. Here, we analyzed the role of the most prominent LRRK2 kinase substrate RAB10 and the role of the LRRK2 interactor RAB29 in the trafficking defects mediated by pathogenic G2019S LRRK2. We find that expression of active RAB10 rescues the G2019S LRRK2-mediated phenotypes on endolysosomal trafficking, while RAB10 knockdown mimics those defects which correlates with a decrease in RAB7A activity, identical to that previously described for RAB8A. The EGFR endolysosomal trafficking impairments caused by either G2019S LRRK2 expression or RAB10 knockdown results in the accumulation of EGF in a RAB4-positive endocytic recycling compartment, which is reversed by active RAB7A, active RAB8A or active RAB10 expression but not by either of their WT or inactive versions. Furthermore, we find that WT RAB29, previously reported to recruit LRRK2 to the Golgi Apparatus (GA), efficiently rescues G2019S LRRK2-caused impairments in EGFR degradation and reverts the accumulation of EGF in a RAB4-positive endocytic recycling ...