7sk2
Human wildtype GABA reuptake transporter 1 in complex with tiagabine, inward-open conformation
Structural highlights
DiseaseSC6A1_HUMAN Myoclonic-astatic epilepsy;Autosomal dominant non-syndromic intellectual disability. The disease is caused by variants affecting the gene represented in this entry. FunctionSC6A1_HUMAN Mediates transport of gamma-aminobutyric acid (GABA) together with sodium and chloride and is responsible for the reuptake of GABA from the synapse (PubMed:30132828). The translocation of GABA, however, may also occur in the reverse direction leading to the release of GABA (By similarity). The direction and magnitude of GABA transport is a consequence of the prevailing thermodynamic conditions, determined by membrane potential and the intracellular and extracellular concentrations of Na(+), Cl(-) and GABA (By similarity). Can also mediate sodium- and chloride-dependent transport of hypotaurine but to a much lower extent as compared to GABA (By similarity).[UniProtKB:P23978][UniProtKB:P31648][1] Publication Abstract from PubMedgamma-Aminobutyric acid (GABA) transporter 1 (GAT1)(1) regulates neuronal excitation of the central nervous system by clearing the synaptic cleft of the inhibitory neurotransmitter GABA upon its release from synaptic vesicles. Elevating the levels of GABA in the synaptic cleft, by inhibiting GABA reuptake transporters, is an established strategy to treat neurological disorders, such as epilepsy(2). Here we determined the cryo-electron microscopy structure of full-length, wild-type human GAT1 in complex with its clinically used inhibitor tiagabine(3), with an ordered part of only 60 kDa. Our structure reveals that tiagabine locks GAT1 in the inward-open conformation, by blocking the intracellular gate of the GABA release pathway, and thus suppresses neurotransmitter uptake. Our results provide insights into the mixed-type inhibition of GAT1 by tiagabine, which is an important anticonvulsant medication. Its pharmacodynamic profile, confirmed by our experimental data, suggests initial binding of tiagabine to the substrate-binding site in the outward-open conformation, whereas our structure presents the drug stalling the transporter in the inward-open conformation, consistent with a two-step mechanism of inhibition(4). The presented structure of GAT1 gives crucial insights into the biology and pharmacology of this important neurotransmitter transporter and provides blueprints for the rational design of neuromodulators, as well as moving the boundaries of what is considered possible in single-particle cryo-electron microscopy of challenging membrane proteins. Structural basis of GABA reuptake inhibition.,Motiwala Z, Aduri NG, Shaye H, Han GW, Lam JH, Katritch V, Cherezov V, Gati C Nature. 2022 Jun;606(7915):820-826. doi: 10.1038/s41586-022-04814-x. Epub 2022 , Jun 8. PMID:35676483[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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