Kappa Opioid Receptor Antagonism Restores Phosphorylation, Trafficking and Behavior induced by a Disease Associated Dopamine Transporter Variant

Abstract

Aberrant dopamine (DA) signaling is implicated in schizophrenia, bipolar disorder (BPD), autism spectrum disorder (ASD), substance use disorder, and attention-deficit/hyperactivity disorder (ADHD). Treatment of these disorders remains inadequate. We established that the human DA transporter (DAT) coding variant (DAT Val559), identified in individuals with ADHD, ASD, or BPD, exhibits anomalous DA efflux (ADE) that is blocked by therapeutic amphetamines and methylphenidate. As the latter agents have high abuse liability, we exploited DAT Val559 knock-in mice to identify non-addictive agents that can normalize DAT Val559 functional and behavioral effects ex vivo and in vivo. Kappa opioid receptors (KORs) are expressed by DA neurons and modulate DA release and clearance, suggesting that targeting KORs might offset the effects of DAT Val559. We establish that enhanced DAT Thr53 phosphorylation and increased DAT surface trafficking associated with DAT Val559 expression are mimicked by KOR agonism of wildtype preparations and rescued by KOR antagonism of DAT Val559 ex vivo preparations. Importantly, KOR antagonism also corrected in vivo DA release and sex-dependent behavioral abnormalities. Given their low abuse liability, our studies with a construct valid model of human DA associated disorders reinforce considerations of KOR antagonism as a pharmacological strategy to treat DA associated brain disorders.

Dopamine transporter threonine-53 phosphorylation dictates kappa opioid receptor mediated locomotor suppression and conditioned place aversion via transporter upregulation

“…Functional DAT activity on DA-terminals governs extracellular DA dynamics [19]. The fact that DAT kinetic properties and surface expression are dynamically regulated by kinase-mediated phosphorylation and that KOR activation triggers DAT-T53 phosphorylation to stimulate DAT function and surface expression in a heterologous cell culture model [24,25] reveals a potential role of in-vivo DAT-T53 phosphorylation in KOR-mediated DA clearance and KOR-induced aversive behavior and locomotor suppression. However, an investigation of this hypothesis is lacking to date.…”

“…However, the role of DAT phosphorylation in a physiologically relevant model system has yet to be determined. Given the fact that KOR is expressed as a heteroreceptor on DAT expressing DA terminals [11,12], using heterologous expression systems and native rat striatal tissue, we previously demonstrated that KOR agonists upregulate DAT function via ERK1/2 activation and that this regulation requires Thr53 phosphorylation of DAT (pT53-DAT) [24,25]. However, a causative relationship of endogenous pT53-DAT to KOR-mediated DAT upregulation has not yet been investigated, and its contribution to KOR agonist-induced aversion and locomotor suppression is also unknown.…”

Leaky lessons learned: Efflux prone dopamine transporter variant reveals sex and circuit specific contributions of D2 receptor signalling to neuropsychiatric disease

“…Systemic administration of a KOR antagonist restored vesicular DA release and responses to systemic cocaine in DAT Val559 mice (Figure 2). 60 Importantly, this pharmacological intervention normalized multiple behaviours in male and female mice that are affected by DAT Val559 expression 60 …”

“…Hyperphosphorylation of protein kinase C beta (PKCβ) and calmodulin‐dependent protein kinase II (CamKII) in cells expressing DAT Val559, relative to control cells expressing WT DAT. References: DA K M , DA V max and IC 50 values 29 ; Na + K M (DA efflux) and V max (DA efflux) 31 ; hyperphosphorylation (Ser7, Ser12, Ser13), 32 (Thr53) 36,38,60 ; clustering and lateral mobility 61 ; hyperphosphorylation CamKII 32 ; and PKCβII 27 …”