Abstract 481: GRK5 as a Novel DNA-Binding Protein in Cardiomyocyte Hypertrophic Stress

Abstract

Introduction: The pathogenesis and progression of heart failure (HF) encompasses aberrations in gene regulation, leading to ventricular remodeling and maladaptive cardiac hypertrophy. A common maladaptation in HF is an increase in the expression level of the G protein-coupled receptor kinase, GRK5. Recently, non-canonical roles for GRK5 have been uncovered that are crucial for the development of maladaptive hypertrophy and these are due to nuclear translocation and accumulation of GRK5. We have shown that GRK5 is a histone deacetylase kinase promoting de-repression of hypertrophic gene transcription through MEF2 and can also facilitate transcriptional activity of NFAT through DNA-binding. The latter is consistent with studies revealing that GRK5 contains a DNA-binding domain. Hypothesis: We hypothesize that the DNA-dependent roles of GRK5 are a mechanism by which GRK5 contributes to gene reprogramming in myocardial hypertrophic stress. Methods: To further study this, neonatal rat ventricular cardiomyocytes overexpressing GRK5 were subjected to α-adrenergic stress with 50μM phenylephrine (PE) or vehicle for 30 minutes to induce nuclear accumulation of GRK5. Chromatin was isolated and GRK5 immunoprecipitation (ChIP) employed to pull-down DNA associated with GRK5 (n=3 PE, n=4 vehicle). Next generation sequencing of this DNA provides an unbiased view of GRK5 DNA binding. Results: The GRK5 ChIP-Seq revealed that GRK5 translocation upon hypertrophic stress leads to multiple promoter, exon, and enhancer DNA-binding events. Gene ontology revealed enrichment of pathways known to be involved in hypertrophy, including the NFAT and Ras pathways. Promoters for genes relevant to cardiac hypertrophy, such as bone natriuretic peptide and early growth response 1 were also found to be enriched by GRK5 immunoprecipitation with PE treatment. In conclusion, we show that during hypertrophic stress, GRK5 mobilizes to the nucleus of myocytes and localizes around diverse genes involved in cardiomyocyte hypertrophy. Further studies in vivo will reveal whether GRK5 has a causal DNA-dependent role in gene reprogramming in HF.