Ras-like without CAAX 2 (RIT2): a susceptibility gene for autism spectrum disorder

et al. 2019

Neuropsychopharmacol.

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 Pitx3 IRES2-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.

Section: Introductionmentioning

confidence: 99%

Conditional, inducible gene silencing in dopamine neurons reveals a sex-specific role for Rit2 GTPase in acute cocaine response and striatal function

et al. 2019

Neuropsychopharmacol.

“…Rit2 activity is required for NGFmediated p38 MAP kinase and ERK activation in neuroendocrine cells (Shi, Han, and Andres 2005;Uenaka et al 2018). Moreover, Rit2 gene expression is enriched specifically in DA neurons (Zhou et al 2011), and several recent GWAS studies identified Rit2 SNPs and long tandem repeat variants associated with multiple DArelated disorders, including Parkinson's disease, ASD, and schizophrenia (Glessner et al 2010;Pankratz et al 2012;Zhang et al 2015;Emamalizadeh et al 2017;Foo et al 2017;Hamedani et al 2017). However, despite its disease association, relatively little is known about endogenous DAergic Rit2 function.…”

Section: Introductionmentioning

confidence: 99%

“…Rit2 (AKA: Rin) is a neuronal small GTPase that lacks a CAAX domain, and associates with the plasma membrane in a phosphoinositide-dependent manner (28)(29)(30). Rit2 gene expression is highly enriched in DA neurons (31), and several recent GWAS studies identified Rit2 SNPs and long tandem repeat variants associated with multiple DA-related disorders, including PD, ASD, and schizophrenia (32)(33)(34)(35)(36)(37). However, despite its disease association, relatively little is known about endogenous DAergic Rit2 function.…”

mentioning

confidence: 99%

Dopamine transporter trafficking and Rit2 GTPase: Mechanism of action and in vivo impact

et al. 2019

Preprint

Following its evoked release, DA signaling is rapidly terminated by presynaptic reuptake, mediated by the cocaine-sensitive DAT. DAT surface availability is dynamically regulated by endocytic trafficking, and direct PKC activation acutely diminishes DAT surface expression by accelerating DAT internalization. Previous cell line studies demonstrated that PKC-stimulated DAT endocytosis requires both Ack1 inactivation, which releases a DAT-specific endocytic brake, and the neuronal GTPase, Rit2, which binds DAT. However, it is unknown whether Rit2 is required for PKC-stimulated DAT endocytosis in DAergic terminals, or whether there are region-and/or sexdependent differences in PKC-stimulated DAT trafficking. Moreover, the mechanisms by which Rit2 controls PKC-stimulated DAT endocytosis are unknown. Here, we directly examined these important questions. Ex vivo studies revealed that PKC activation acutely decreased DAT surface expression selectively in ventral, but not dorsal, striatum. AAV-mediated, conditional Rit2 knockdown in DAergic neurons impacted baseline DAT surface:intracellular distribution in DAergic terminals from female ventral, but not dorsal, striatum. Further, Rit2 was required for PKCstimulated DAT internalization in both male and female ventral striatum. FRET and surface pulldown studies in cell lines revealed that PKC activation drives DAT-Rit2 surface dissociation, and that the DAT N-terminus is required for both PKC-mediated DAT-Rit2 dissociation and DAT internalization. Finally, we found that Rit2 and Ack1 independently converge on DAT to facilitate PKC-stimulated DAT endocytosis. Together, our data provide greater insight into mechanisms that mediate PKC-regulated DAT internalization, and reveal unexpected region-specific differences in PKC-stimulated DAT trafficking in bona fide DAergic terminals. _______________________________________ DA neurotransmission is required for motor control, learning, memory, motivation, and reward (1,2). DAergic dysregulation is evidenced in numerous neuropsychiatric disorders, including ADHD, ASD, schizophrenia, bipolar disorder, addiction, and PD (3-8). DA signaling is tightly controlled by the presynaptic DAT, which rapidly clears synaptically released DA. DAT is also the primary target for addictive and therapeutic

mentioning

confidence: 99%

Dopamine transporter trafficking and Rit2 GTPase: Mechanism of action and in vivo impact

Journal of Biological Chemistry

et al. 2020

Following its evoked release, dopamine (DA) signaling is rapidly terminated by presynaptic reuptake, mediated by the cocaine-sensitive DA transporter (DAT). DAT surface availability is dynamically regulated by endocytic trafficking, and direct protein kinase C (PKC) activation acutely diminishes DAT surface expression by accelerating DAT internalization. Previous cell line studies demonstrated that PKC-stimulated DAT endocytosis requires both Ack1 inactivation, which releases a DAT-specific endocytic brake, and the neuronal GTPase, Rit2, which binds DAT. However, it is unknown whether Rit2 is required for PKC-stimulated DAT endocytosis in DAergic terminals or whether there are region- and/or sex-dependent differences in PKC-stimulated DAT trafficking. Moreover, the mechanisms by which Rit2 controls PKC-stimulated DAT endocytosis are unknown. Here, we directly examined these important questions. Ex vivo studies revealed that PKC activation acutely decreased DAT surface expression selectively in ventral, but not dorsal, striatum. AAV-mediated, conditional Rit2 knockdown in DAergic neurons impacted baseline DAT surface:intracellular distribution in DAergic terminals from female ventral, but not dorsal, striatum. Further, Rit2 was required for PKC-stimulated DAT internalization in both male and female ventral striatum. FRET and surface pulldown studies in cell lines revealed that PKC activation drives DAT-Rit2 surface dissociation and that the DAT N terminus is required for both PKC-mediated DAT-Rit2 dissociation and DAT internalization. Finally, we found that Rit2 and Ack1 independently converge on DAT to facilitate PKC-stimulated DAT endocytosis. Together, our data provide greater insight into mechanisms that mediate PKC-regulated DAT internalization and reveal unexpected region-specific differences in PKC-stimulated DAT trafficking in bona fide DAergic terminals.