Alpha1a-Adrenoceptor Genetic Variant Triggers Vascular Smooth Muscle Cell Hyperproliferation and Agonist Induced Hypertrophy via EGFR Transactivation Pathway

Abstract

α1a Adrenergic receptors (α1aARs) are the predominant AR subtype in human vascular smooth muscle cells (SMCs). α1aARs in resistance vessels are crucial in the control of blood pressure, yet the impact of naturally occurring human α1aAR genetic variants in cardiovascular disorders remains poorly understood. To this end, we present novel findings demonstrating that 3D cultures of vascular SMCs expressing human α1aAR-247R (247R) genetic variant demonstrate significantly increased SMC contractility compared with cells expressing the α1aAR-WT (WT) receptor. Stable expression of 247R genetic variant also triggers MMP/EGFR-transactivation dependent serum- and agonist-independent (constitutive) hyperproliferation and agonist-dependent hypertrophy of SMCs. Agonist stimulation reduces contractility Using pathway-specific inhibitors we determined that the observed hyperproliferation of 247R-expressing cells is triggered via β-arrestin1/Src/MMP-2/EGFR/ERK-dependent mechanism. MMP-2-specific siRNA inhibited 247R-triggered hyperproliferation indicating MMP-2 involvement in 247R-triggered hyperproliferation in SMCs. β-arrestin1-specific shRNA also inhibited 247R-triggered hyperproliferation but did not affect hypertrophy in 247R-expressing SMCs, indicating that agonist-dependent hypertrophy is independent of β-arrestin1. Our data reveal that in different cardiovascular cells the same human receptor genetic variant can activate alternative modulators of the same signaling pathway. Thus, our findings in SMCs demonstrate that depending on the type of cells expressing the same receptor (or receptor variant), different target-specific inhibitors could be used to modulate aberrant hyperproliferative or hypertrophic pathways in order to restore normal phenotype.

G Protein–Coupled Receptor Signaling Through β-Arrestin–Dependent Mechanisms

“…87 On the other hand, β-arrestins promote sphingosine-1-phosphate-induced transactivation of Fetal Liver Kinase 1 (Flk-1) through S1P1/S1P3 receptors, resulting in mouse embryonic stem cell proliferation. 88 β-arrestins also mediate EGFR transactivation by the β 1 AR, 89 a genetic variant of α 1 AR, 90 ET 1A R, 91 urotensin II receptor (UTR), 92 GPR39 93 and GPR54. 94 β-arrestin mediated EGFR transactivation may induce diverse cellular responses such as cardioprotection when provoked by β 1 AR and UTR, cardiomyoblast hyperproliferation and hypertrophy in the case of α 1 AR, myogenesis for GPR39 and cancer cell invasiveness for ET 1A R and GPR54.…”

Calcium/calmodulin regulates signaling at the α1A adrenoceptor

“…Activation of the α 1A adrenoceptor triggers vasoconstriction (Minneman, 1988), hypertrophy and proliferation (Gradinaru et al, 2015;Lei et al, 2013). In the heart, the α 1A adrenoreceptor is more abundant than the α 1B or α 1D isoform (Jensen et al, 2009), and constitutes ~16% total adrenergic response.…”

alpha1A‐adrenoceptor is involved in norepinephrine‐induced proliferation of pulmonary artery smooth muscle cells via CaMKII signaling

“…All three subtypes of α 1 ‐AR are expressed in vascular smooth muscle cells (VSMCs) and their activation with NE stimulates cells migration, proliferation, and protein synthesis . Among them, α 1A ‐ AR is the predominant subtype of α 1 ‐AR in human VSMCs and crucial in the control of blood pressure in resistance vessels . However, less is known about the detailed mechanisms of stimulation of α 1A ‐AR by NE causing PASMCs proliferation.…”

“…20,21 Among them, α 1A -AR is the predominant subtype of α 1 -AR in human VSMCs and crucial in the control of blood pressure in resistance vessels. 22 However, less is known about the detailed mechanisms of stimulation of α 1A -AR by NE causing PASMCs proliferation. The aim of this study was to investigate whether NE induced proliferation of PASMCs by stimulation of α 1A -AR.…”