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.
Footnotes
- Received January 9, 2015.
- Accepted March 31, 2015.
H.D.S. is supported by a training grant from the National Institutes of Health National Institute on Aging [Grant T32-AG020494]. This study was supported by the Welch Foundation [Grant BK-1736]; and the American Heart Association [Beginning Grant-In-Aid Grant 12BGIA8820001].
This work was presented at the following workshops: Snell HD and Gonzales EB (2014) Amiloride and GMQ allosteric modulation of the GABA-A ρ1 receptor: influences of the intersubunit site. University of North Texas Health Science Center 21st annual Research Appreciation Day; 2014 Apr 12; Fort Worth, TX; Snell HD and Gonzales EB (2014) Amiloride and GMQ allosteric modulation of the GABA-A ρ1 receptor: influences of the intersubunit site. Experimental Biology (EB) National Conference; 2014 Apr 26–30; San Diego, CA; Snell HD and Gonzales EB (2014) Amiloride and GMQ allosteric modulation of the GABA-A ρ1 receptor: influences of the intersubunit site. Society for the Advancement of Chicanos and Native Americans in Science (SACNAS) National Conference; 2014 Oct 16–18; Los Angeles, CA; and Snell HD and Gonzales EB (2014) Amiloride and GMQ allosteric modulation of the GABA-A ρ1 receptor: influences of the intersubunit site. Society for Neuroscience (SFN) National Conference; 2014 Nov 15–19; Washington, DC.
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- Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics
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