RAB7L1-Mediated Relocalization of LRRK2 to the Golgi Complex Causes Centrosomal Deficits via RAB8A

Abstract

Mutations in the LRRK2 gene cause autosomal-dominant Parkinson’s disease (PD), and both LRRK2 as well as RAB7L1 have been implicated in increased susceptibility to idiopathic PD. RAB7L1 has been shown to increase membrane-association and kinase activity of LRRK2, and both seem to be mechanistically implicated in the same pathway. Another RAB protein, RAB8A, has been identified as a prominent LRRK2 kinase substrate, and our recent work demonstrates that aberrant LRRK2-mediated phosphorylation of RAB8A leads to centrosomal alterations. Here, we show that RAB7L1 recruits LRRK2 to the Golgi complex, which causes accumulation of phosphorylated RAB8A in a pericentrosomal/centrosomal location as well as centrosomal deficits identical to those observed with pathogenic LRRK2. The centrosomal alterations induced by wildtype LRRK2 in the presence of RAB7L1 depend on Golgi integrity. This is in contrast to pathogenic LRRK2 mutants, which cause centrosomal deficits independent of Golgi integrity or largely independent on RAB7L1 expression. Furthermore, centrosomal alterations in the presence of wildtype LRRK2 and RAB7L1 are at least in part mediated by aberrant LRRK2-mediated RAB8A phosphorylation, as abolished by kinase inhibitors and reduced upon knockdown of RAB8A. These results indicate that pathogenic LRRK2, as well as increased levels of RAB7L1, cause centrosomal deficits in a manner dependent on aberrant RAB8A phosphorylation and centrosomal/pericentrosomal accumulation, suggesting that centrosomal cohesion deficits may comprise a useful cellular readout for a broader spectrum of the disease.

Vesicular Dysfunction and the Pathogenesis of Parkinson’s Disease: Clues From Genetic Studies

“…This stabilizing function was mediated by the recruitment of LRRK2 and Rab7L1 from the Golgi onto the stressed lysosomes placing Rab7L1 further upstream on this pathway than Rab8A and Rab10 even as they serve a similar regulatory function . This is further confirmed by the finding that the centrosomal deficits caused by Rab8A phosphorylation by LRRK2 as it was recruited on to the Golgi by Rab7L1 (Madero-Pérez et al, 2018b). This taken together would indicate that relocalization of LRRK2 mediated by Rab7L1 may result in many of the previously discussed deleterious interactions with Rabs and other yet unknown effectors further downstream.…”

The Emerging Functions of LRRK2 and Rab GTPases in the Endolysosomal System

“…The observation that Rab29 acts upstream of LRRK2 was preceded by other studies showing that Rab29 recruits LRRK2 to the trans-Golgi network (TGN) or TGN-derived vesicles (MacLeod et al, 2013;Beilina et al, 2014) where Rab29 normally resides (Helip-Wooley and Thoene, 2004), and potently upregulates the LRRK2 kinase activity (Purlyte et al, 2018). Following this study, Madero-Perez et al (2018b) have also shown that Rab29 recruits LRRK2 to the Golgi complex and causes centrosomal deficits, although the recruitment of LRRK2 to the Golgi by Rab29 was observed solely under overexpressed conditions. As the above-noted studies commonly showed that the recruitment of LRRK2 by Rab29 in turn results in the recruitment of Rab8 and Rab10 that are phosphorylated by LRRK2, this tandem flow of recruitment may work as the central "Rab29-LRRK2-Rab8/10 cascade" in the LRRK2 pathobiology (Figure 2).…”

Membrane association but not identity is required for LRRK2 activation and phosphorylation of Rab GTPases

“…In addition, the Q67L mutant that in other Rabs would be expected to lock the protein in an active conformation was not localized to the Golgi and bound nucleotide more weakly than Rab29 WT protein (Beilina et al, 2014). Additionally, a small pool of T21N Rab29 localizes to the Golgi (Wang et al, 2014;Madero-Pérez et al, 2018b). This suggested that canonical mutations cannot be used to study Rab29 and that additional mutagenesis and careful characterization would be required.…”