Amiloride and GMQ Allosteric Modulation of the GABA-A ρ1 Receptor: Influences of the Intersubunit Site.

Abstract

Amiloride, a diuretic used in the treatment of hypertension and congestive heart failure, and 2-guanidine-4-methylquinazoline (GMQ) are guanidine compounds that modulate acid-sensing ion channels. Both compounds have demonstrated affinity for a variety of membrane proteins, including members of the Cys-loop family of ligand-gated ion channels, such as the heteromeric GABA-A αβγ receptors. The actions of these guanidine compounds on the homomeric GABA-A ρ1 receptor remains unclear, especially in light of how many GABA-A αβγ receptor modulators have different effects in the GABA-A ρ1 receptors. We sought to characterize the influence of amiloride and GMQ on the human GABA-A ρ1 receptors using whole-cell patch-clamp electrophysiology. The diuretic amiloride potentiated the human GABA-A ρ1 GABA-mediated current, whereas GMQ antagonized the receptor. Furthermore, a GABA-A second transmembrane domain site, the intersubunit site, responsible for allosteric modulation in the heteromeric GABA-A receptors mediated amiloride's positive allosteric actions. In contrast, the mutation did not remove GMQ antagonism but only changed the guanidine compound's potency within the human GABA-A ρ1 receptor. Through modeling and introduction of point mutations, we propose that the GABA-A ρ1 intersubunit site plays a role in mediating the allosteric effects of amiloride and GMQ.

• Authors: Heather D Snell, Eric B Gonzales
• Journal: The Journal of pharmacology and experimental therapeutics (J Pharmacol Exp Ther) Vol. 353 Issue 3 Pg. 551-9 (Jun 2015) ISSN: 1521-0103 [Electronic] United States
• PMID: 25829529 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

Chemical References

• 2-guanidine-4-methylquinazoline
• Diuretics
• Guanidines
• Histamine H2 Antagonists
• Quinazolines
• Receptors, GABA-A
• Amiloride

Topics

• Amiloride (pharmacology)
• Amino Acid Sequence
• Cells, Cultured
• Diuretics (pharmacology)
• Guanidines (pharmacology)
• Histamine H2 Antagonists (pharmacology)
• Humans
• Models, Molecular
• Molecular Sequence Data
• Mutagenesis, Site-Directed
• Patch-Clamp Techniques
• Quinazolines (pharmacology)
• Receptors, GABA-A (drug effects, genetics)