G protein-coupled receptor kinase 5: exploring its hype in cardiac hypertrophy

KR-39038, a Novel GRK5 Inhibitor, Attenuates Cardiac Hypertrophy and Improves Cardiac Function in Heart Failure

G protein-coupled receptor kinase 5 (GRK5) has been considered as a potential target for the treatment of heart failure as it has been reported to be an important regulator of pathological cardiac hypertrophy. To discover novel scaffolds that selectively inhibit GRK5, we have identified a novel small molecule inhibitor of GRK5, KR-39038 [7-((3-((4-((3-aminopropyl)amino)butyl)amino)propyl)amino)-2-(2-chlorophenyl)-6-fluoroquinazolin-4(3H)-one]. KR-39038 exhibited potent inhibitory activity (IC₅₀ value=0.02 µM) against GRK5 and significantly inhibited angiotensin II-induced cellular hypertrophy and HDAC5 phosphorylation in neonatal cardiomyocytes. In the pressure overload-induced cardiac hypertrophy mouse model, the daily oral administration of KR-39038 (30 mg/kg) for 14 days showed a 43% reduction in the left ventricular weight. Besides, KR-39038 treatment (10 and 30 mg/kg/day, p.o.) showed significant preservation of cardiac function and attenuation of myocardial remodeling in a rat model of chronic heart failure following coronary artery ligation. These results suggest that potent GRK5 inhibitor could effectively attenuate both cardiac hypertrophy and dysfunction in experimental heart failure, and KR-39038 may be useful as an effective GRK5 inhibitor for pharmaceutical applications.

GRK2 and GRK5 as therapeutic targets and their role in maladaptive and pathological cardiac hypertrophy

INTRODUCTION

One in every four deaths in the United States is attributed to cardiovascular disease, hence the development and employment of novel and effective therapeutics are necessary to improve the quality of life and survival of affected patient. Pathological hypertrophy is a maladaptive response by the heart to relieve wall stress that could result from cardiovascular disease. Maladaptive hypertrophy can lead to further disease progression and complications such as heart failure; hence, efforts to target hypertrophy to prevent and treat further morbidity and mortality are necessary. Areas covered: This review summarizes the compelling literature that describes the mechanistic role of GRK2 and GRK5 in maladaptive cardiac hypertrophy; it examines the approaches to inhibit these kinases in hypertrophic animal models and furthermore, it assesses the potential of GRK2 and GRK5 as therapeutic targets for hypertrophy. Expert opinion: GRK2 and GRK5 are novel therapeutic targets for pathological hypertrophy and may have added benefits of ameliorating morbidity and mortality. Despite the lesser researched role of GRK2 in cardiac hypertrophy, it may be the advantageous strategy for treating cardiac hypertrophy because of its role in other maladaptive pathways. Anti-GRK2 therapy optimization and the discovery and development of specific GRK2 and GRK5 small-molecule inhibitors is necessary for the eventual application of successful, effective therapeutics.

The Amino-Terminal Domain of GRK5 Inhibits Cardiac Hypertrophy through the Regulation of Calcium-Calmodulin Dependent Transcription Factors

We have recently demonstrated that the amino-terminal domain of G protein coupled receptor kinase (GRK) type 5, (GRK5-NT) inhibits NFκB activity in cardiac cells leading to a significant amelioration of LVH. Since GRK5-NT is known to bind calmodulin, this study aimed to evaluate the functional role of GRK5-NT in the regulation of calcium-calmodulin-dependent transcription factors. We found that the overexpression of GRK5-NT in cardiomyoblasts significantly reduced the activation and the nuclear translocation of NFAT and its cofactor GATA-4 in response to phenylephrine (PE). These results were confirmed in vivo in spontaneously hypertensive rats (SHR), in which intramyocardial adenovirus-mediated gene transfer of GRK5-NT reduced both wall thickness and ventricular mass by modulating NFAT and GATA-4 activity. To further verify in vitro the contribution of calmodulin in linking GRK5-NT to the NFAT/GATA-4 pathway, we examined the effects of a mutant of GRK5 (GRK5-NTPB), which is not able to bind calmodulin. When compared to GRK5-NT, GRK5-NTPB did not modify PE-induced NFAT and GATA-4 activation. In conclusion, this study identifies a double effect of GRK5-NT in the inhibition of LVH that is based on the regulation of multiple transcription factors through means of different mechanisms and proposes the amino-terminal sequence of GRK5 as a useful prototype for therapeutic purposes.