GRK2-Mediated Crosstalk Between β-Adrenergic and Angiotensin II Receptors Enhances Adrenocortical Aldosterone Production In Vitro and In Vivo.

Celina Pollard,Jainika Patel,Arianna Perez,Janelle Pereyra,Anastasios Lymperopoulos,Jennifer Ghandour,Shelby Wertz,Krysten Ferraino,Victoria Desimine,Natalie Cora,Barbara Parker

doi:10.3390/ijms21020574

Abstract

Aldosterone is produced by adrenocortical zona glomerulosa (AZG) cells in response to angiotensin II (AngII) acting through its type I receptors (AT1Rs). AT1R is a G protein-coupled receptor (GPCR) that induces aldosterone via both G proteins and the adapter protein βarrestin1, which binds the receptor following its phosphorylation by GPCR-kinases (GRKs) to initiate G protein-independent signaling. β-adrenergic receptors (ARs) also induce aldosterone production in AZG cells. Herein, we investigated whether GRK2 or GRK5, the two major adrenal GRKs, is involved in the catecholaminergic regulation of AngII-dependent aldosterone production. In human AZG (H295R) cells in vitro, the βAR agonist isoproterenol significantly augmented both AngII-dependent aldosterone secretion and synthesis, as measured by the steroidogenic acute regulatory (StAR) protein and CYP11B2 (aldosterone synthase) mRNA inductions. Importantly, GRK2, but not GRK5, was indispensable for the βAR-mediated enhancement of aldosterone in response to AngII. Specifically, GRK2 inhibition with Cmpd101 abolished isoproterenol’s effects on AngII-induced aldosterone synthesis/secretion, whereas the GRK5 knockout via CRISPR/Cas9 had no effect. It is worth noting that these findings were confirmed in vivo, since rats overexpressing GRK2, but not GRK5, in their adrenals had elevated circulating aldosterone levels compared to the control animals. However, treatment with the β-blocker propranolol prevented hyperaldosteronism in the adrenal GRK2-overexpressing rats. In conclusion, GRK2 mediates a βAR-AT1R signaling crosstalk in the adrenal cortex leading to elevated aldosterone production. This suggests that adrenal GRK2 may be a molecular link connecting the sympathetic nervous and renin-angiotensin systems at the level of the adrenal cortex and that its inhibition might be therapeutically advantageous in hyperaldosteronism-related conditions.

Highlights

Aldosterone is an adrenocortical mineralocorticoid hormone with significant cardiovascular toxicity when produced in excess, as it contributes to hypertension, heart failure, and other heart conditions [1,2,3]
AT1R is a G protein-coupled receptor (GPCR) that signals through G protein-independent pathways, a plethora of which are mediated by the scaffolding actions of βarrestins, which were originally discovered as terminators of GPCR signaling following receptor phosphorylation by a GPCR-kinase (GRK) [6]
In an effort to delineate the signaling mechanisms that underlie the catecholaminergic modulation of angiotensin II (AngII)-dependent aldosterone production in the adrenal cortex, we investigated, in the present study, the effects of βAR stimulation on AngII-dependent aldosterone production in the human adrenocortical zona glomerulosa (AZG) cell line H295R, as well as the potential involvement of the most abundant GRK isoforms in the adrenal gland, GRK2 and GRK5 [19], in this process

Summary

Introduction

Aldosterone is an adrenocortical mineralocorticoid hormone with significant cardiovascular toxicity when produced in excess, as it contributes to hypertension, heart failure, and other heart conditions [1,2,3] It is produced and secreted by the adrenal cortex, mainly in response to elevated serum potassium levels or angiotensin II (AngII) acting through AngII type I receptors (AT1Rs), which are endogenously expressed in adrenocortical zona glomerulosa (AZG) cells [4,5]. ERKs transcriptionally upregulate the steroidogenic acute regulatory (StAR) protein, the rate-limiting enzyme of aldosterone biosynthesis responsible for mitochondrial uptake of cholesterol, and the precursor of all adrenal steroids [8,9] Catecholamines, such as the sympathetic nervous system hormones norepinephrine and epinephrine, are known to potentiate AngII actions in various tissues, including the adrenal cortex [10,11,12,13]. In an effort to delineate the signaling mechanisms that underlie the catecholaminergic modulation of AngII-dependent aldosterone production in the adrenal cortex, we investigated, in the present study, the effects of βAR stimulation on AngII-dependent aldosterone production in the human AZG cell line H295R, as well as the potential involvement of the most abundant GRK isoforms in the adrenal gland, GRK2 and GRK5 [19], in this process

Methods

Results

Conclusion