Nuclear Translocation of Cardiac G Protein-Coupled Receptor Kinase 5 Downstream of Select Gq-Activating Hypertrophic Ligands Is a Calmodulin-Dependent Process

Jessica I Gold,Donald M Bers,J Kurt Chuprun,Walter J Koch,Linda Lee,Erhe Gao,Julie Bossuyt,Douglas G Tilley,Jonathan Hullmann,Joseph E Rabinowitz,Jeffrey S Martini

doi:10.1371/journal.pone.0057324

Jessica I Gold, Donald M Bers + Show 9 more

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https://doi.org/10.1371/journal.pone.0057324

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Abstract

G protein-Coupled Receptors (GPCRs) kinases (GRKs) play a crucial role in regulating cardiac hypertrophy. Recent data from our lab has shown that, following ventricular pressure overload, GRK5, a primary cardiac GRK, facilitates maladaptive myocyte growth via novel nuclear localization. In the nucleus, GRK5’s newly discovered kinase activity on histone deacetylase 5 induces hypertrophic gene transcription. The mechanisms governing the nuclear targeting of GRK5 are unknown. We report here that GRK5 nuclear accumulation is dependent on Ca2+/calmodulin (CaM) binding to a specific site within the amino terminus of GRK5 and this interaction occurs after selective activation of hypertrophic Gq-coupled receptors. Stimulation of myocytes with phenylephrine or angiotensinII causes GRK5 to leave the sarcolemmal membrane and accumulate in the nucleus, while the endothelin-1 does not cause nuclear GRK5 localization. A mutation within the amino-terminus of GRK5 negating CaM binding attenuates GRK5 movement from the sarcolemma to the nucleus and, importantly, overexpression of this mutant does not facilitate cardiac hypertrophy and related gene transcription in vitro and in vivo. Our data reveal that CaM binding to GRK5 is a physiologically relevant event that is absolutely required for nuclear GRK5 localization downstream of hypertrophic stimuli, thus facilitating GRK5-dependent regulation of maladaptive hypertrophy.

Highlights

G protein-coupled receptor (GPCR) kinases (GRKs) desensitize G protein-Coupled Receptors (GPCRs) via agonist-dependent phosphorylation
To further advance our understanding of hypertrophic agonist-induced nuclear GRK5 localization, we investigated select Gq-coupled receptor ligands known to induce cardiac hypertrophy
Immunostaining was used to assess the subcellular localization of GRK5 in adult rabbit ventricular myocytes (AdRbM) following stimulation with PE (50 mM), ET-1 (100 nM) or AngII (10 mM)

Summary

Introduction

G protein-coupled receptor (GPCR) kinases (GRKs) desensitize GPCRs via agonist-dependent phosphorylation. Seven members of the GRK family have been identified to date with GRK2 and GRK5 being the most abundant in the heart [1,2] These kinases have been shown to play important roles in physiological cardiac signaling, via regulation of badrenergic receptor (bAR)-mediated contractility [2,3,4,5]. Transgenic mice with cardiac-specific overexpression of GRK5 demonstrate intolerance to ventricular pressure-overload, as evidenced by augmented cardiac hypertrophy and accelerated HF following aortic banding [12]. This accelerated pathological phenotype differs greatly from mice overexpressing GRK2, which respond to pressure-overload to wild-type mice [12]. This phenotypic disparity is rooted in differences between the structure and subcellular localization of GRK2 and GRK5, predominantly the ability of GRK5 to enter the nucleus [12,13,14,15]

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