Neurodegeneration caused by LRRK2-G2019S requires Rab10 in select dopaminergic neurons
AbstractInherited mutations in the LRRK2 protein are the commonest known cause of Parkinson’s, but the molecular link from increased kinase activity to pathological neurodegeneration remains to be determined.In vitro(biochemical and cell culture) assays led to the hypothesis that several Rab GTPases might be LRRK2 substrates. Here we show that Rab10 potently modifiesLRRK2-G2019Smediated electrophysiological responses in anin vivoscreen, in which each Rab was overexpressed inDrosophiladopaminergic neurons. We therefore tested the effect ofRab10loss of function on threeLRRK2-G2019Sphenotypes (vision, movement and sleep) that rely on dopaminergic circuits in both flies and mammals. The knock-out of Rab10in vivofully rescues the reduced responses induced by dopaminergicLRRK2-G2019Sin visual and motor (reaching, proboscis extension) assays, but the sleep phenotype is unaffected. We show that Rab10 is expressed in dopaminergic (tyrosine hydroxylase positive) neurons controlling vision and proboscis movement, but undetectable in those controlling sleep, indicating that anatomical and physiological patterns of Rab10 are related. Our results support the idea that LRRK2 phosphorylates separate targets in distinct neurons and confirm that one degenerative pathway starts with Rab10. Although Rab3 is another putative substrate of LRRK2, it shows no synergy with G2019S and localises to a different subset of dopaminergic neurons from Rab10. We propose that variations inRabexpression may contribute to differences in the rate of neurodegeneration seen in different dopaminergic nuclei in Parkinson’s.Significance StatementA key question in Parkinson’s is why dopamine neurons die particularly fast in some parts of thesubstantia nigra. We focused on the commonest Parkinson’s-related mutation, LRRK2-G2019S.In vitroassays suggested that neurodegeneration may start by LRRK2-G2019S increasing phosphorylation of Rab10. We found Rab10 in fly dopamine neurons in visual and motor pathways, but not in the sleep system. Rab10 knock-out rescues G2019S-induced visual and movement degeneration, leaving sleep dysfunction unaffected. Thus, LRRK2 activates at least two pathways, one Rab10-dependent, leading to neurodegenerationin vivo. Rab3 is found in a different subset of dopaminergic neurons and shows no synergy withLRRK2-G2019S. We propose that variations inRabexpression contribute to differences in neurodegeneration seen in Parkinson’s.
