No abstract

Parkinsons disease (PD) is the second most prevalent neurodegenerative disease and arises from dopamine (DA) neuron death selectively in the substantia nigra pars compacta (SNc). Rit2 is a reported PD risk allele, and recent single cell transcriptomic studies identified a major RIT2 cluster in PD DA neurons, potentially linking Rit2 expression anomalies to a PD patient cohort. However, it is still unknown whether Rit2 loss itself is causative for PD or PD-like symptoms. Here we report that conditional Rit2 silencing in mouse DA neurons drove a progressive motor dysfunction that was more rapid in males than females and was rescued at early stages by either inhibiting the DA transporter (DAT) or with L-DOPA treatment. Motor dysfunction was accompanied by decreases in DA release, striatal DA content, phenotypic DAergic markers, and a loss of DA neurons, with increased pSer129-alpha synuclein expression. These results provide the first evidence that Rit2 loss is causal for SNc cell death and a PD-like phenotype, and reveal key sex-specific differences in the response to Rit2 loss.

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disease and arises from dopamine (DA) neuron death selectively in the substantia nigra pars compacta (SNc) . Rit2 is a reported PD risk allele, and recent single cell transcriptomic studies identified a major RIT2 cluster in PD DA neurons, potentially linking Rit2 expression anomalies to a PD patient cohort. However, it is still unknown whether Rit2 loss itself is causative for PD or PD-like symptoms. Here we report that conditional Rit2 silencing in mouse DA neurons drove a progressive motor dysfunction that was more rapid in males than females and was rescued at early stages by either inhibiting the DA transporter (DAT) or with L-DOPA treatment. Motor dysfunction was accompanied by decreases in DA release, striatal DA content, phenotypic DAergic markers, and a loss of DA neurons, with increased pSer129-alpha synuclein expression. These results provide the first evidence that Rit2 loss is causal for SNc cell death and a PD-like phenotype, and reveal key sex-specific differences in the response to Rit2 loss.

Extracellular dopamine (DA) levels are tightly constrained by presynaptic reuptake mediated by the DA transporter (DAT). Despite its necessity for DA neurotransmission, DAT regulation in situ is poorly understood, and it is unknown whether DAT regulation impacts dopaminergic signaling and/or behaviors. Here, we leveraged chemogenetics and conditional gene silencing and found that presynaptic Gq-coupled receptor activation, induced by either hM3Dq or mGluR5 activation, drives biphasic DAT trafficking in striatum. Two PD risk alleles, Vps35 and Rit2, were required for mGluR5-stimulated DAT insertion and retrieval, respectively. Conditional dopaminergic mGluR5 silencing abolished DAT trafficking and resulted in motor dysfunction. Moreover, ex vivo voltammetric studies demonstrate that DAT trafficking significantly impacts DA clearance. These studies reveal that presynaptic DAT trafficking is complex, multimodal, and region-specific, and identify cell autonomous mechanisms required for DAT trafficking. Importantly, the findings suggest that regulated DAT trafficking likely impacts both DA clearance and motor function.