Exploring the Dopamine Transporter Utilizing a Two-Pronged Approach with Novel Cathinone Analogs and Mutant Dopamine Transporters

The dopamine transporter (DAT) is responsible for the removal of the neurotransmitter from the synaptic gap and a therapeutic target for a multitude of drugs. While the ortholog Drosophila melanogaster dopamine transporter (dDAT) and human serotonin transporter (hSERT) have resolved structures, the human dopamine transporter (hDAT) does not. A 3-D computational homology model of hDAT was constructed for the study of molecular interactions with agents within the central binding site (S1) of the transporter. Synthetic cathiones are a class of abused stimulant drugs that primarily target DAT. Greater than 150 cathinones have been identified on the clandestine market but there is not much known about the structure-activity relationship (SAR) of these abused compounds. A dichloro substituted benzoylpiperdine compound, part of novel series of benzoylpiperdine cathinones, was found to be a potent DAT inhibitor. Two new disubstituted compounds were computationally modelled, synthesized, and biologically evaluated to investigate the effect of these substituents in DAT inhibitor potency. It was found that all compounds were active and that the hybrids with electron donating substituents were weaker compared to the hybrids with electron withdrawing substituents tested. Cathinones based on the pyrrolidinophenone scaffold, such as 3,4-methylenedioxypyrovalerone (MDPV), a-pyrrolidinopentiophenone (a-PVP), and 3,4-methylenedioxy-a-pyrrolidinopropiophenone (MDPPP), are established illicit psychostimulants. These compounds are potent inhibitors of hDAT but have little to no activity at dDAT. In collaboration with Dr. Eltit’s lab (VCU) gain-of-function studies and in silico modeling using mutant DAT transporters were performed. Four non-conserved amino acid residues critical for MDPV’s high potency activity as a reuptake inhibitor at hDAT were identified. These residues can drive MDPV selectivity not only by stabilizing binding, but also by controlling access to its binding site