Cryo-EM structure of GABA transporter 1 reveals substrate recognition and transport mechanism

The GABA transporters (GATs) enforce spatiotemporal control of the inhibitory neurotransmitter GABA at neural synapses. Nayak et al. report the structure of substrate-bound GAT1 in an ion-bound cytosol-facing conformation, providing mechanistic insights into GABA selection and reuptake. The inhibitory neurotransmitter & gamma;-aminobutyric acid (GABA) is cleared from the synaptic cleft by the sodium- and chloride-coupled GABA transporter GAT1. Inhibition of GAT1 prolongs the GABAergic signaling at the synapse and is a strategy to treat certain forms of epilepsy. In this study, we present the cryo-electron microscopy structure of Rattus norvegicus GABA transporter 1 (rGAT1) at a resolution of 3.1 & ANGS;. The structure elucidation was facilitated by epitope transfer of a fragment-antigen binding (Fab) interaction site from the Drosophila dopamine transporter (dDAT) to rGAT1. The structure reveals rGAT1 in a cytosol-facing conformation, with a linear density in the primary binding site that accommodates a molecule of GABA, a displaced ion density proximal to Na site 1 and a bound chloride ion. A unique insertion in TM10 aids the formation of a compact, closed extracellular gate. Besides yielding mechanistic insights into ion and substrate recognition, our study will enable the rational design of specific antiepileptics.

Automated summary

The structure of GAT1 has been reported, providing insights into the mechanism of GABA selection and reuptake. This study is important for the development of strategies to treat certain forms of epilepsy and the rational design of specific antiepileptic drugs.