期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：20
页码：7769-7774
DOI：10.1073/pnas.0400220101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Fast synaptic inhibitory transmission in the CNS is mediated by {gamma}-aminobutyric acid type A (GABAA) receptors. They belong to the ligand-gated ion channel receptor superfamily, and are constituted of five subunits surrounding a chloride channel. Their clinical interest is highlighted by the number of therapeutic drugs that act on them. It is well established that the subunit composition of a receptor subtype determines its pharmacological properties. We have investigated positional effects of two different {alpha}-subunit isoforms, {alpha}1 and {alpha}6, in a single pentamer. For this purpose, we used concatenated subunit receptors in which subunit arrangement is predefined. The resulting receptors were expressed in Xenopus oocytes and analyzed by using the two-electrode voltage-clamp technique. Thus, we have characterized {gamma}2{beta}2{alpha}1{beta}2{alpha}1, {gamma}2{beta}2{alpha}6{beta}2{alpha}6, {gamma}2{beta}2{alpha}1{beta}2{alpha}6, and {gamma}2{beta}2{alpha}6{beta}2{alpha}1 GABAA receptors. We investigated their response to the agonist GABA, to the partial agonist piperidine-4-sulfonic acid, to the noncompetitive inhibitor furosemide and to the positive allosteric modulator diazepam. Each receptor isoform is characterized by a specific set of properties. In this case, subunit positioning provides a functional signature to the receptor. We furthermore show that a single {alpha}6-subunit is sufficient to confer high furosemide sensitivity, and that the diazepam efficacy is determined exclusively by the {alpha}-subunit neighboring the {gamma}2-subunit. By using this diagnostic tool, it should become possible to determine the subunit arrangement of receptors expressed in vivo that contain {alpha}1- and {alpha}6-subunits. This method may also be applied to the study of other ion channels.
