Allosteric Modulator KM822 Attenuates Behavioral Actions of Amphetamine in Caenorhabditis elegans through Interactions with the Dopamine Transporter DAT-1

Abstract

Aberrant dopamine (DA) signaling is associated with several psychiatric disorders such as autism, bipolar disorder, addiction, and Parkinson's disease, and several medications that target the DA transporter (DAT) can induce or treat these disorders. In addition, psychostimulants, such as cocaine and D-amphetamine (AMPH), rely on the competitive interactions with the transporter's substrate binding site to produce their rewarding effects. Agents that exhibit noncompetitive, allosteric modulation of DAT remain an important topic of investigation, owing to their potential therapeutic applications. We previously identified a novel allosteric modulator of human DAT, KM822, that can decrease the affinity of cocaine for DAT and attenuate cocaineelicited behaviors, though whether DAT is the sole mediator of KM822 actions in vivo is unproven given the large number of potential off-target sites. Here, we provide in silico and in vitro evidence that the allosteric site engaged by KM822 is conserved between human DAT and C. elegans DAT-1. KM822 binds to a similar pocket in DAT-1 as previously identified in human DAT. In functional dopamine uptake assays, KM822 affects the interaction between AMPH and DAT-1 by reducing the affinity of AMPH for DAT-1. Finally, through a combination of genetic and pharmacological in vivo approaches we provide evidence that KM822 diminish the behavioral actions of AMPH on swimming-induced paralysis (SWIP) through a direct allosteric modulation of DAT-1. More broadly, our findings demonstrate allosteric modulation of DAT as a behavior modifying strategy and suggests that C. elegans can be operationalized to identify and investigate the interactions of DAT allosteric modulators.

Long-Lasting Epigenetic Changes in the Dopamine Transporter in Adult Animals Exposed to Amphetamine during Embryogenesis: Investigating Behavioral Effects

“…To test if Amph causes physiological changes during embryogenesis without the interference of possible effects from Amph-induced changes in maternal care, we used the simple model Caenorhabditis elegans (C. elegans). This model lacks maternal care but retains a conserved dopaminergic response to Amph [16,17]. In fact, previous data showed that when forced to swim in solutions containing 0.3-1 mM Amph, C. elegans exhibits a unique behavior named Swimming-Induced Paralysis (SWIP), and we demonstrated that Amph-induced SWIP is caused by an overload of DA in the synapses through DAT-1 reversal function.…”

Substance Addiction Rehabilitation Drugs

“…These knocked-out mice treated with cocaine displayed diminished behavioral cocaine responses [21]. But all known DAT modulators [22] or Vav2 antagonists are non-FDA-approved drugs. Interestingly, recent evidence highlighted that piRNAs induced by L-methionine down-regulate the Vav2 gene via a miRNA-like mechanism (Figure 1).…”

Allosteric modulation of serotonin and dopamine transporters: New insights from computations and experiments

“…In an animal model, we demonstrated that the compound did not affect the locomotion of planarians but inhibited cocaine-induced hyperlocomotion. In a follow up study our group in collaboration with the Blakely group also demonstrated that KM822 attenuates an amphetamine-induced behavior in C. elegans roundworms and does not induce this behavior by itself ( Refai et al, 2022 ). Furthermore, we found that this did not occur in an animal with DAT genetically removed, supporting that this behavioral effect is elicited through the specific allosteric modulation of DAT function.…”