Vacuolar protein sorting 35 (Vps35) is a component of the retromer complex and plays a role for vesicular trafficking. LRRK2 is a member of the leucine-rich repeat kinase family, which is involved in endosomal trafficking. It has been found that mutations in Vps35 and LRRK2 are linked to autosomal dominant forms of Parkinson's disease. However, how the mutations of Vps35 and LRRK2 affect the neuronal functions and survival are largely unknown. In this study, we examined the effects of Drosophila Vps35 (dVps35) loss-of-function and its pathogenic mutation in the presence or absence of a Drosophila LRRK2 homolog dLRRK using Drosophila.
Ectopic expression of both dVps35 wild-type (WT) and its pathogenic mutant dVps35 D647N in the central dopaminergic (DA) neurons did not lead to loss of neurons whereas ubiquitous expression of dVps35 D647N in the vps35 heterozygous genetic background mildly reduced lifespan. Removal of one copy of the dVps35 gene caused abnormal sleep and locomotor behaviors, which were completely rescued by the expression of dVps35 WT but not D645N mutant. Abnormal synaptogenesis in the larval synaptic neuromuscular junction was observed by motoneuron-specific inactivation of dVps35. Spontaneous dopamine release of adult DA neurons was enhanced by DA expression of dVps35 WT while dVps35 D645N did not affect it.
We further found that a genetic interaction between dvps35 and dLRRK in Drosophila. Loss of dLRRK activity exacerbated defects of wing morphogenesis and abnormal synaptogenesis by dVps35 knockdown. The amounts of dopamine in the adult brain tissues increased by suppression of both dVps35 and dLRRK activities.
Our results suggest that the etiologies of PD linked to Vps35 and LRRK2 converge with disturbance of the vesicular trafficking in neurons.