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Ion Binding and Permeation at the GABA Transporter GAT1

Mager, Sela and Kleinberger-Doron, Nurit and Keshet, Gilmor I. and Davidson, Norman and Kanner, Baruch I. and Lester, Henry A. (1996) Ion Binding and Permeation at the GABA Transporter GAT1. Journal of Neuroscience, 16 (17). pp. 5405-5414. ISSN 0270-6474. PMCID PMC6578888. doi:10.1523/jneurosci.16-17-05405.1996.

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This study addresses the binding of ions and the permeation of substrates during function of the GABA transporter GAT1. GAT1 was expressed in Xenopus oocytes and studied electrophysiologically as well as with [³H]GABA flux; GAT1 was also expressed in mammalian cells and studied with [³H]GABA and [³H]tiagabine binding. Voltage jumps, Na⁺ and Cl⁻ concentration jumps, and exposure to high-affinity blockers (NO-05-711 and SKF-100330A) all produce capacitive charge movements. Occlusive interactions among these three types of perturbations show that they all measure the same population of charges. The concentration dependences of the charge movements reveal (1) that two Na⁺ ions interact with the transporter even in the absence of GABA, and (2) that Cl⁻ facilitates the binding of Na⁺. Comparison between the charge movements and the transport-associated current shows that this initial Na⁺-transporter interaction limits the overall transport rate when [GABA] is saturating. However, two classes of manipulation—treatment with high-affinity uptake blockers and the W68L mutation—“lock” Na⁺ onto the transporter by slowing or preventing the subsequent events that release the substrates to the intracellular medium. The Na⁺ substitutes Li⁺ and Cs⁺ do not support charge movements, but they can permeate the transporter in an uncoupled manner. Our results (1) support the hypothesis that efficient removal of synaptic transmitter by the GABA transporter GAT1 depends on the previous binding of Na⁺ and Cl⁻, and (2) indicate the important role of the conserved putative transmembrane domain 1 in interactions with the permeant substrates.

Item Type:Article
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URLURL TypeDescription CentralArticle
Lester, Henry A.0000-0002-5470-5255
Additional Information:© 1996 Society for Neuroscience. Received April 26, 1996; revised June 14, 1996; accepted June 18, 1996. This work was supported by grants from the National Institute of Neurological Diseases and Stroke and the U.S./Israel Binational Science Foundation, and by fellowships from the Lester Deutsch Foundation and the Muscular Dystrophy Association (S.M.). We thank G. Rudnick for help with the [3H]tiagabine binding assay, C. Armstrong and A. Finkelstein for discussion of charge movements and membrane dielectrics, and J. Li and M. Nowak for comments on this manuscript.
Funding AgencyGrant Number
National Institute of Neurological Disorders and Stroke (NINDS)UNSPECIFIED
Binational Science Foundation (USA-Israel)UNSPECIFIED
Lester Deutsch FoundationUNSPECIFIED
Muscular Dystrophy AssociationUNSPECIFIED
Subject Keywords:sodium; chloride; GAT1; GABA; transporter; Xenopus oocyte
Issue or Number:17
PubMed Central ID:PMC6578888
Record Number:CaltechAUTHORS:20191030-155045434
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Official Citation:Ion Binding and Permeation at the GABA Transporter GAT1. Sela Mager, Nurit Kleinberger-Doron, Gilmor I. Keshet, Norman Davidson, Baruch I. Kanner, Henry A. Lester. Journal of Neuroscience 1 September 1996, 16 (17) 5405-5414; DOI: 10.1523/JNEUROSCI.16-17-05405.1996
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99571
Deposited By: Tony Diaz
Deposited On:31 Oct 2019 01:47
Last Modified:17 Feb 2022 00:24

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