Stimulation of the Epithelial Na+ Channel in Renal Principal Cells by Gs-Coupled Designer Receptors Exclusively Activated by Designer Drugs

Antonio G Soares; Jorge Contreras; Crystal R Archer; Elena Mironova; Rebecca Berdeaux; James D Stockand; Tarek Mohamed Abd El-Aziz

doi:10.3389/fphys.2021.725782

Stimulation of the Epithelial Na⁺ Channel in Renal Principal Cells by Gs-Coupled Designer Receptors Exclusively Activated by Designer Drugs

Front Physiol. 2021 Aug 25:12:725782. doi: 10.3389/fphys.2021.725782. eCollection 2021.

Authors

Antonio G Soares¹, Jorge Contreras¹, Crystal R Archer¹, Elena Mironova¹, Rebecca Berdeaux², James D Stockand¹, Tarek Mohamed Abd El-Aziz^{1

3}

Affiliations

¹ Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States.
² Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX, United States.
³ Zoology Department, Faculty of Science, Minia University, Minya, Egypt.

Abstract

The activity of the Epithelial Na⁺ Channel (ENaC) in renal principal cells (PC) fine-tunes sodium excretion and consequently, affects blood pressure. The Gs-adenylyl cyclase-cAMP signal transduction pathway is believed to play a central role in the normal control of ENaC activity in PCs. The current study quantifies the importance of this signaling pathway to the regulation of ENaC activity in vivo using a knock-in mouse that has conditional expression of Gs-DREADD (designer receptors exclusively activated by designer drugs; GsD) in renal PCs. The GsD mouse also contains a cAMP response element-luciferase reporter transgene for non-invasive bioluminescence monitoring of cAMP signaling. Clozapine N-oxide (CNO) was used to selectively and temporally stimulate GsD. Treatment with CNO significantly increased luciferase bioluminescence in the kidneys of PC-specific GsD but not control mice. CNO also significantly increased the activity of ENaC in principal cells in PC-specific GsD mice compared to untreated knock-in mice and CNO treated littermate controls. The cell permeable cAMP analog, 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate, significantly increased the activity and expression in the plasma membrane of recombinant ENaC expressed in CHO and COS-7 cells, respectively. Treatment of PC-specific GsD mice with CNO rapidly and significantly decreased urinary Na⁺ excretion compared to untreated PC-specific GsD mice and treated littermate controls. This decrease in Na⁺ excretion in response to CNO in PC-specific GsD mice was similar in magnitude and timing as that induced by the selective vasopressin receptor 2 agonist, desmopressin, in wild type mice. These findings demonstrate for the first time that targeted activation of Gs signaling exclusively in PCs is sufficient to increase ENaC activity and decrease dependent urinary Na⁺ excretion in live animals.

Keywords: epithelial sodium channel; hypertension; sodium excretion; sodium transport; vasopressin.