HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 92/2/883    most recent 01040.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (8) Citing Articles via Google Scholar Google Scholar Articles by Huang, R.-Q. Articles by Dillon, G. H. Search for Related Content PubMed PubMed Citation Articles by Huang, R.-Q. Articles by Dillon, G. H.

Molecular Basis for Modulation of Recombinant 122 GABA_A Receptors by Protons

Department of Pharmacology and Neuroscience, University of North Texas, Health Science Center at Fort Worth, Fort Worth, Texas 76107

Submitted 27 October 2003; accepted in final form 16 March 2004

We have previously shown that extracellular protons inhibit recombinant and native GABA_A receptors. In this report, we studied the site(s) and mechanism by which protons modulate the GABA_A receptor. Whole cell GABA-activated currents were recorded from human embryonic kidney (HEK) 293 cells expressing recombinant 122 GABA_A receptors. Protons competitively inhibited the response to GABA and bicuculline. In contrast, change in pH did not influence direct gating of the channel by pentobarbital, and it did not influence spontaneous channel openings in 1(L264T)22 receptors, suggesting pH does not modulate channel activity by affecting the channel gating process directly. To test the hypothesis that protons modulate GABA_A receptors at the ligand binding site, we systemically mutated N-terminal residues known to be involved in GABA binding and assessed effects of pH on these mutant receptors. Site-specific mutation of 2 Y205 to F or 1 F64 to A, both of which are known to influence GABA binding, significantly reduced pH sensitivity of the GABA response. These mutations did not affect Zn²⁺ sensitivity, suggesting that H⁺ and Zn²⁺ do not share a common site of action. Additional experiments further tested this possibility. Treatment with the histidine-modifying reagent diethylpyrocarbonate (DEPC) reduced Zn²⁺-mediated inhibition of GABA_A receptors but had no effect on proton-induced inhibition of GABA currents. In addition, mutation of residues known to be involved in Zn²⁺ modulation had no effect on pH modulation of GABA_A receptors. Our results support the hypothesis that protons inhibit GABA_A receptor function by direct or allosteric interaction with the GABA binding site. In addition, the sites of action of H⁺ and Zn²⁺ in GABA_A receptors are distinct.

This article has been cited by other articles:

				R. M. Kaminski, H. Marini, P. I. Ortinski, S. Vicini, and M. A. Rogawski The Pheromone Androstenol (5{alpha}-Androst-16-en-3{alpha}-ol) Is a Neurosteroid Positive Modulator of GABAA Receptors J. Pharmacol. Exp. Ther., May 1, 2006; 317(2): 694 - 703. [Abstract] [Full Text] [PDF]

				M. E. Wilkins, A. M. Hosie, and T. G. Smart Proton modulation of recombinant GABAA receptors: influence of GABA concentration and the {beta} subunit TM2-TM3 domain J. Physiol., September 1, 2005; 567(2): 365 - 377. [Abstract] [Full Text] [PDF]