Inhibition of vascular smooth muscle G protein-coupled receptor kinase 2 enhances α_1D-adrenergic receptor constriction

Abstract

G protein-coupled receptor kinase 2 (GRK2) is a serine/theorinine kinase that phosphorylates and desensitizes agonist-bound G protein-coupled receptors. GRK2 is increased in expression and activity in lymphocytes and vascular smooth muscle (VSM) in human hypertension and animal models of the disease. Inhibition of GRK2 using the carboxyl-terminal portion of the protein (GRK2ct) has been an effective tool to restore compromised beta-adrenergic receptor (AR) function in heart failure and improve outcome. A well-characterized dysfunction in hypertension is attenuation of betaAR-mediated vasodilation. Therefore, we tested the role of inhibition of GRK2 using GRK2ct or VSM-selective GRK2 gene ablation in a renal artery stenosis model of elevated blood pressure (BP) [the two-kidney, one-clip (2K1C) model]. Use of the 2K1C model resulted in a 30% increase in conscious BP, a threefold increase in plasma norepinephrine levels, and a 50% increase in VSM GRK2 mRNA levels. BP remained increased despite VSM-specific GRK2 inhibition by either GRK2 knockout (GRK2KO) or peptide inhibition (GRK2ct). Although betaAR-mediated dilation in vivo and in situ was enhanced, alpha(1)AR-mediated vasoconstriction was also increased. Further pharmacological experiments using alpha(1)AR antagonists revealed that GRK2 inhibition of expression (GRK2KO) or activity (GRK2ct) enhanced alpha(1D)AR vasoconstriction. This is the first study to suggest that VSM alpha(1D)ARs are a GRK2 substrate in vivo.

Increased Nitric Oxide Bioavailability in Adult GRK2 Hemizygous Mice Protects Against Angiotensin II–Induced Hypertension

“…They better maintain endothelial function and display an attenuated AngII-induced decline in the Akt-eNOS route and in eNOS levels. These data further build on previous results describing a role for GRK2 in the control of portal hypertension 9,11 and in diabetes mellitus/obesity-triggered mild hypertensive conditions. 13 This report is the first to characterize the role of an overall selective inhibition of GRK2 function in the development of systemic hypertension and in the structure and biomechanics of the vessels.…”

“…6 GRK2 downregulates the in vivo effects of key vasoconstrictor receptors, such as ET 7 and AngII 8 receptors and α1 D adrenoceptors. 9 Therefore, the increase in vascular GRK2 could have represented a protective mechanism for adaptation against a hypertensive phenotype. However, transgenic mice overexpressing GRK2 in the vascular smooth muscle cells (VSMC) show increased resting blood pressure.…”

“…11 Another important emerging question is the relative importance of endothelial GRK2 as compared with VSMC-GRK2 because depletion of GRK2 in VSMC is unable to prevent portal hypertension. 9 Our work tries to shed some light on these issues describing for the first time that a global reduction in GRK2 causes resistance to the development of systemic hypertension in adult mice. This antihypertensive effect of GRK2 downregulation prevails even when responses to both vasodilator and vasoconstrictor receptors are enhanced and this is because of the increased NO bioavailability detected in GRK2 +/− mice.…”

Developmental and tumoral vascularization is regulated by G protein–coupled receptor kinase 2

“…Strikingly, the endothelia of GRK2-deficient mice were almost devoid of mural cell recruitment, which is determinant for vessel maturation. Such defects in pericyte and smooth muscle cell coating appear to be secondary to a general endothelial dysfunction and not a result of defects in pericyte specification, proliferations or mobilization, since Grk2 +/-VSMCs display even higher migration rates toward PDGF than WT cells, in agreement with previous data (13), and no angiogenic phenotype has been described in mice with specific GRK2 deletion in VSMCs (15). Moreover, endothelium-specific ablation of GRK2 also results in a leaky vasculature with defective covering of SMCs and pericytes.…”

“…Besides regulating chemokine GPCRs, GRK2 phosphorylates PDGF receptors (10) and also modulates TGF-β signaling in epithelial cells (11) or cardiac fibroblasts (12). GRK2 inhibits PDGF-dependent chemotactic signaling in VSMCs (13) and modulates both vasoconstrictory and vasodilatory responses of VSMCs (14,15), whereas increased GRK2 attenuates NO production by sinusoidal ECs in the context of liver injury (16). However, the role of GRK2 in vessel formation and stability in other pathophysiological settings has not been addressed.…”