Snell Heather D, Gonzales Eric B
Department of Pharmacology and Neuroscience (H.D.S., E.B.G.), Institute for Aging and Alzheimer's Disease Research (E.B.G.), and Cardiovascular Research Institute (E.B.G.), University of North Texas Health Science Center, Fort Worth, Texas.
Department of Pharmacology and Neuroscience (H.D.S., E.B.G.), Institute for Aging and Alzheimer's Disease Research (E.B.G.), and Cardiovascular Research Institute (E.B.G.), University of North Texas Health Science Center, Fort Worth, Texas
J Pharmacol Exp Ther. 2015 Jun;353(3):551-9. doi: 10.1124/jpet.115.222802. Epub 2015 Mar 31.
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.
氨氯吡咪是一种用于治疗高血压和充血性心力衰竭的利尿剂，2-胍基-4-甲基喹唑啉（GMQ）是调节酸敏感离子通道的胍类化合物。这两种化合物都已证明对多种膜蛋白具有亲和力，包括半胱氨酸环家族配体门控离子通道的成员，如异聚GABA-Aαβγ受体。这些胍类化合物对同聚GABA-A ρ1受体的作用仍不清楚，尤其是考虑到许多GABA-Aαβγ受体调节剂在GABA-A ρ1受体中有不同的作用。我们试图使用全细胞膜片钳电生理学来表征氨氯吡咪和GMQ对人GABA-A ρ1受体的影响。利尿剂氨氯吡咪增强了人GABA-A ρ1介导的GABA电流，而GMQ则拮抗该受体。此外，GABA-A第二个跨膜结构域位点，即亚基间位点，负责异聚GABA-A受体中的变构调节，介导了氨氯吡咪的正变构作用。相比之下，该突变并未消除GMQ的拮抗作用，而只是改变了胍类化合物在人GABA-A ρ1受体中的效力。通过建模和点突变的引入，我们提出GABA-A ρ1亚基间位点在介导氨氯吡咪和GMQ的变构效应中起作用。
