Blood Pressure Is Regulated by an α1D-Adrenergic Receptor/Dystrophin Signalosome

Abstract

Hypertension is a cardiovascular disease associated with increased plasma catecholamines, overactivation of the sympathetic nervous system, and increased vascular tone and total peripheral resistance. A key regulator of sympathetic nervous system function is the ␣ 1D -adrenergic receptor (AR), which belongs to the adrenergic family of G-protein-coupled receptors (GPCRs). Endogenous catecholamines norepinephrine and epinephrine activate ␣ 1D -ARs on vascular smooth muscle to stimulate vasoconstriction, which increases total peripheral resistance and mean arterial pressure. Indeed, ␣ 1D -AR KO mice display a hypotensive phenotype and are resistant to salt-induced hypertension. Unfortunately, little information exists about how this important GPCR functions because of an inability to obtain functional expression in vitro. Here, we identified the dystrophin proteins, syntrophin, dystrobrevin, and utrophin as essential GPCR-interacting proteins for ␣ 1D -ARs. We found that dystrophins complex with ␣ 1D -AR both in vitro and in vivo to ensure proper functional expression. More importantly, we demonstrate that knock-out of multiple syntrophin isoforms results in the complete loss of ␣ 1D -AR function in mouse aortic smooth muscle cells and abrogation of ␣ 1D -AR-mediated increases in blood pressure. Our findings demonstrate that syntrophin and utrophin associate with ␣ 1D

α-Dystrobrevin-1 recruits α-catulin to the α 1D -adrenergic receptor/dystrophin-associated protein complex signalosome

“…Clinical interest in the α 1D -AR as a drug target has recently increased with the discoveries that α 1D -ARs are the predominant subtype expressed in epicardial coronary arteries (11) and that α 1D -AR prostate expression increases in patients with benign prostatic hypertrophy (12). Through proteomic screening, we discovered that α 1D -ARs are scaffolded to the dystrophin-associated protein complex (DAPC) via the anchoring protein syntrophin (10). Coexpression with syntrophins increases α 1D -AR plasma membrane expression, drug binding, and activation of Gαq/11 signaling after agonist activation.…”

“…Coexpression with syntrophins increases α 1D -AR plasma membrane expression, drug binding, and activation of Gαq/11 signaling after agonist activation. Moreover, syntrophin knockout mice lose α 1D -ARstimulated increases in blood pressure, demonstrating the importance of these essential GIPs for α 1D -AR function in vivo (10).…”

“…A member of the adrenergic family (α 1 , α 2 , β), α 1D -ARs are ubiquitously expressed on blood vessels and are responsible for increasing blood pressure during exercise, injury, stress, or cardiovascular disease (6). α 1D -AR knockout mice are hypotensive and resistant to high salt diet-induced hypertension (7,8), yet this GPCR has been largely ignored over the past 20 y because after transfection into cell culture α 1D -ARs are sequestered in the endoplasmic reticulum (9,10). Clinical interest in the α 1D -AR as a drug target has recently increased with the discoveries that α 1D -ARs are the predominant subtype expressed in epicardial coronary arteries (11) and that α 1D -AR prostate expression increases in patients with benign prostatic hypertrophy (12).…”

“…4A) (9,26). To circumvent this technical issue, we used an α 1D -AR-syntrophin fusion protein separated by a six-glycine linker (10). We previously demonstrated that this molecular construct increases α 1D -AR receptor density and enhances signaling (10).…”

α1D-Adrenergic receptor insensitivity is associated with alterations in its expression and distribution in cultured vascular myocytes

“…For example, the truncation of 79 amino acids from the receptors' N-termini results in translocation of the α 1D -ARs from intracellular compartments onto the plasma membrane, and a three-to four-fold increase in IP 3 formation due to norepinephrine stimulation [41] . Additionally, dystrophin proteins, a type of intracellular anchor protein, have been identified as essential elements for α 1D -AR but not for α 1A -or α 1B -AR functional expression for both in vitro and in vivo situations [42] . Therefore, all the previous studies describe a clear picture indicating the complexity of regulating α 1D -AR expression at the cell membrane, a critical process for the receptor efficient functional performance.…”