Identification of pyrimidine structure-based compounds as allosteric ligands of the dopamine transporter as therapeutic agents for NeuroHIV.

ABSTRACT

The disruption of dopamine neurotransmission by the HIV-1 Transactivator of transcription (Tat) during HIV-1 infection has been linked to the development of neurocognitive disorders, even under combined antiretroviral therapy (cART) treatment. We have demonstrated that SRI-32742, a novel allosteric modulator of dopamine (DA) transporter (DAT), attenuates cocaine- and Tat-binding to DAT, alleviates Tat-induced cognitive deficits and potentiation of cocaine reward in inducible Tat transgenic mice. The current study determined the in vitro pharmacological profile of SRI-32743 and its optimized second-generation analogs and their effects as allosteric modulators. Through structure-activity relationship studies of SRI-32743, 170 compounds were synthesized and evaluated for their ability to modulate DAT function. We identified 21 analogs as atypical competitors of DAT (Emax {less than or equal to}60%). Four compounds, SRI-46564, SRI-47056, SRI-46286 and SRI-47867, displayed IC50 values for [3H]DA uptake inhibition from 9.33 {plus minus} 0.50 to 0.96 {plus minus} 0.05 µM and from 3.96 {plus minus} 1.36 to 1.29 {plus minus} 0.19 for DAT binding, respectively. The four analogs also displayed high potency at two different concentrations (0.5 nM and 0.05 nM) to attenuate Tat-induced inhibition of [3H]DA uptake and cocaine-mediated dissociation of [3H]WIN35,428 binding in CHO cells expressing hDAT, suggesting that the effects occur through an allosteric mechanism. In further ex vivo studies using Fast-Scan Cyclic Voltammetry, we demonstrated that the analogs do not disrupt the baseline phasic-like DA release. These findings provide a new insight into the potential for development of novel therapeutic agents to attenuate DAT-Tat interactions to normalize DA neurotransmission in NeuroHIV. Significance Statement The allosteric inhibition of the dopamine (DA) transporter by the HIV-1 Transactivator of transcription (Tat) disrupts dopamine homeostasis, leading to HIV-associated neurocognitive disorders (HANDs). Analogs of SRI-32743, a novel allosteric modulator of the Tat-DAT interaction, were evaluated in the current study and characterized as atypical ligands of DA uptake. Four novel lead compounds demonstrated high potency to attenuate Tat-induced inhibition of hDAT-mediated DA uptake in an allosteric modulatory manner with no effects on the dynamics of DA uptake-release in DAT.