Centrosomal defects caused by the Parkinson’s disease associated protein kinase LRRK2 and Rab proteins

Résumé

Mutations in the leucine rich repeat kinase 2 (LRRK2) gene are the most common cause of familial Parkinson’s disease (PD), with autosomal-dominant inheritance, and variants in this gene also confer risk to develop sporadic PD. Whilst the cellular and molecular mechanisms underlying LRRK2-PD remain largely unknown, recent studies have identified a subset of Rab GTPases as physiological LRRK2 kinase substrates. In the present study, we identify centrosomal alterations caused by pathogenic LRRK2 using different cell lines and confirmed in patient-derived samples. In non-dividing cells, pathogenic LRRK2 causes deficits in centrosome positioning with downstream consequences for cell differentiation, polarity and directional migration. In dividing cells, pathogenic LRRK2 causes centrosomal cohesion defects. Importantly, we demonstrate that these defects are dependent on the LRRK2 kinase activity. We confirm that Rab8a, a small Rab GTPase with described roles in centrosome-related events, is a LRRK2 kinase substrate, and corroborate that pathogenic LRRK2 increases Rab8a phosphorylation. For the first time, we identify the cellular localization and consequences of LRRK2-mediated Rab8a phosphorylation. We demonstrate that pathogenic LRRK2 causes an abnormal accumulation of phosphorylated Rab8a around the centrosome, which is, at least partially, responsible for the centrosomal cohesion defects. We also evaluate the effects of Rab7L1, a gene that modifies risk for sporadic PD, on the centrosome phenotype. Remarkably, we observe that when increasing Rab7L1 levels, wildtype LRRK2 mimicks the effects of pathogenic LRRK2 on Rab8a phosphorylation and centrosomal cohesion deficits, suggesting that both phenotypes may be a common readout for a broader spectrum of PD. Whilst the downstream consequences of the centrosomal defects and its relevance for PD remain to be elucidated, the data presented here identify a new role for LRRK2 in the context of centrosomal functioning, and indicate the important role of Rab proteins for understanding PD pathogenesis.