A Novel Fluorescent Analog of the Dopamine Reuptake Inhibitor GBR12909

Dopamine transporter is a transmembrane protein associated with regulation of dopaminergic signal transmission by dopamine reuptake from the synaptic cleft back into cytosol. Some neurological disorders, for example Parkinson's disease, are characterized by dopaminergic neuron degeneration resulting in dopamine level decrease in synapses. Therefore, dopamine transporter may be considered as a potential target in therapy of neurodegenerative disorders. However, the development of molecular tools based on dopamine transporter inhibitors remains challenging, as there is a lack of knowledge about dopamine transporter regulation and distribution in the brain. The sets of tropane and piperazine derivatives synthesized previously are the most common compounds among a number of dopamine reuptake inhibitors. It should be noted that the highest affinity and selectivity to dopamine transporter (compared with serotonin and norepinephrine ones) were demonstrated by an N-substituted piperazine derivative GBR12909. As GBR12909 has high affinity and selectivity, its structure may serve as a base for the development of novel functionalized derivatives. Design of a new fluorescent derivative based on the structure of dopamine transporter antagonist GBR12909 to investigate the transporter localization and dynamics in presynaptic membrane is the aim of this paper. We synthesized a novel fluorescent analog of dopamine transporter derivative GBR12909 labeled by the BODIPY-FL fluorophore. In order to synthesize this compound, a module synthesis scheme was developed. According to this scheme, the basic scaffold contains a linker fragment with protected amino group on the distal end of the molecule. Such scheme allows us to synthesize a set of variable GBR12909 derivatives through conjugation of various functionally significant fragments at the amino group. The first step of the target compound synthesis includes production of 1-(2-(bis(4-fluorophenyl)methoxy)ethyl)piperazine and tert-butyl(6-((4-(3-iodopropyl)phenyl)amino)-6-oxohexyl)carbamate) followed by their 'assembly' into one molecule. After the deprotection of the amino group, it was acylated by fluorescent BODIPY-FL-C3 acid. The fluorescent analog was used to investigate its internalization in an experiment with the PC12 pheochromocytoma cells expressing dopamine transporter. Specific accumulation of the fluorescent analog by the cells via the dopamine transporter was demonstrated, the transporter was rather sensitive to GBR12909 inhibition.