Discovery of a subtype selective inhibitor of the human betaine/GABA transporter 1 (BGT-1) with a non-competitive pharmacological profile

Abstract

The γ-aminobutyric acid (GABA) transporters (GATs) are essential regulators of the activity in the GABAergic system through their continuous uptake of the neurotransmitter from the synaptic cleft and extrasynaptic space. Four GAT subtypes have been identified to date, each displaying different pharmacological properties and expression patterns. The present study focus on the human betaine/GABA transporter 1 (BGT-1), which has recently emerged as a new target for treatment of epilepsy. However, the lack of selective inhibitors of this transporter has impaired the exploration of this potential considerably. With the objective of identifying novel compounds displaying selectivity for BGT-1, we performed a screening of a small compound library at cells expressing BGT-1 using a [(3)H]GABA uptake assay. The screening resulted in the identification of the compound N-(1-benzyl-4-piperidinyl)-2,4-dichlorobenzamide (BPDBA), a selective inhibitor of the human BGT-1 transporter with a non-competitive profile exhibiting no significant inhibitory activity at the other three human GAT subtypes. The selectivity profile of the compound was subsequently confirmed at cells expressing the four mouse GAT subtypes. Thus, BPDBA constitutes a potential useful pharmacological tool compound for future explorations of the function of the BGT-1 subtype.

Keywords: (R)-N-[4,4-bis(3-methyl-2-thienyl)-3-butenyl]nipecotic acid; 1-[2-[tris(4-methoxyphenyl)methoxy]ethyl]-(S)-3-piperidine carboxylic acid; BGT-1; BPDBA; CHO; CNS; Chinese hamster ovary; DMEM; DPBS; Dulbecco's Modified Eagle Medium; Dulbecco's Phosphate Buffered Saline; EF-1502; FLIPR™ Membrane Potential; FMP; GABA; GABA transporter; GABA transporters; GAT; HBSS; HEK; Hanks’ Balanced Saline Solution; N-(1-benzyl-4-piperidinyl)-2,4-dichlorobenzamide; N-[4,4-bis(3-methyl-2-thienyl)-3-butenyl]-3-hydroxy-4-(methylamino)-4,5,6,7-tetrahydrobenzo[d]isoxazol-3-ol; Non-competitive inhibition profile; SNAP-5114; betaine/GABA transporter 1; central nervous system; human embryonic kidney; tiagabine; γ-aminobutyric acid.