Browsing by keyword "Rit2"
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Conditional, inducible gene silencing in dopamine neurons reveals a sex-specific role for Rit2 GTPase in acute cocaine response and striatal function [preprint]Dopamine (DA) signaling is critical for movement, motivation, and addictive behavior. The neuronal GTPase, Rit2, is enriched in DA neurons (DANs), binds directly to the DA transporter (DAT), and is implicated in several DA-related neuropsychiatric disorders. However, it remains unknown whether Rit2 plays a role in either DAergic signaling and/or DA-dependent behaviors. Here, we leveraged the TET-OFF system to conditionally silence Rit2 in Pitx3IRES2-tTA mouse DANs. Following DAergic Rit2 knockdown (Rit2-KD), mice displayed an anxiolytic phenotype, with no change in baseline locomotion. Further, males exhibited increased acute cocaine sensitivity, whereas DAergic Rit2-KD suppressed acute cocaine sensitivity in females. DAergic Rit2-KD did not affect presynaptic TH and DAT protein levels in females, nor was TH was affected in males; however, DAT was significantly diminished in males. Paradoxically, despite decreased DAT levels in males, striatal DA uptake was enhanced, but was not due to enhanced DAT surface expression in either dorsal or ventral striatum. Finally, patch recordings in nucleus accumbens (NAcc) medium spiny neurons (MSNs) revealed reciprocal changes in spontaneous EPSP (sEPSP) frequency in male and female D1+ and D2+ MSNs following DAergic Rit2-KD. In males, sEPSP frequency was decreased in D1+, but not D2+, MSNs, whereas in females sEPSP frequency decreased in D2+, but not D1+, MSNs. Moreover, DAergic Rit2-KD abolished the ability of cocaine to reduce sEPSP frequency in D1+, but not D2+, male MSNs. Taken together, our studies are among the first to acheive AAV-mediated, conditional and inducible DAergic knockdown in vivo. Importantly, our results provide the first evidence that DAergic Rit2 expression differentially impacts striatal function and DA-dependent behaviors in males and females.
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Dopaminergic Signaling and Locomotor Behaviors are Regulated by Gq-Receptor-Mediated Dopamine Transporter Trafficking and the Parkinson's Risk Allele Rit2Dopamine (DA) is a modulatory neurotransmitter required for movement, learning, and reward. Several neuropsychiatric disorders exhibit DAergic dysfunction, including Parkinson’s disease (PD). The presynaptic DA transporter (DAT) constrains DAergic signaling via DA reuptake. Acute PKC activation drives DAT endocytosis, however, endogenous receptor-mediated DAT trafficking in striatal terminals remains ill-defined. Here, I present data supporting biphasic Gq-receptor-mediated DAT trafficking in striatum. Gq-receptor activation drives initial DAT insertion, which requires DA release, DAergic DRD2auto activation, and intact retromer. Subsequent DAT retrieval requires PKC and the neuronal GTPase Rit2. Furthermore, I demonstrate that the endogenous Gq-coupled metabotropic glutamate receptor, mGluR5, expressed on DAergic neurons exerts biphasic DAT regulation. DAergic mGluR5 silencing revealed that mGluR5 is required for motor learning and coordination. DAergic mGluR5 cKO motor deficits were rescued by DAT inhibition, suggesting mGluR5-mediated DAT trafficking is required for these behaviors. Apart from its requisite role in DAT trafficking, Rit2 is a PD associated risk allele. We previously demonstrated that Rit2 is required for psychostimulant response and generalized anxiety, but not basal locomotion. However, Rit2’s roles in more complex motor behaviors and PD pathology remain unknown. DAergic Rit2 silencing revealed that Rit2 is required for male motor learning and prolonged Rit2 suppression leads to progressive manifestation of PD biomarkers, coordination deficits, and decreased DAergic tone. Motor learning deficits were rescued by boosting DA availability, echoing Rit2-mediated hypodopaminergia. Together these results identify receptor-mediated DAT trafficking mechanisms in DA terminals, demonstrate that DAT surface dynamics are required for motor function, and implicate DAergic Rit2 loss in progressive PD-like phenotypes.
