Abstract 24071: A Peptide Of The Amino-terminus Of Grk2 Induces Hypertrophy And Yet Elicits Cardioprotection After Pressure Overload.

Abstract

Heart failure (HF) is a leading cause of death worldwide and a growing burden on public health, and the underlying mechanisms of cardiac remodeling and decompensation to HF remain a focus of research efforts towards therapeutic development. Signaling via G protein-coupled receptors (GPCRs) is critical for normal heart function and is tightly controlled by GPCR kinases (GRKs) with GRK2 (originally βARK1), being intimately involved in HF progression. In addition to its well-characterized role in regulating GPCRs, ongoing research has demonstrated great diversity in the functional roles of GRK2. I have recently investigated GRK2 amino terminal binding interactions through the generation of transgenic (Tg) mice with cardiac-targeted expression of the amino-terminal peptide βARKnt (residues 50-145). In a murine model of trans-aortic constriction (TAC)-induced pressure overload, echocardiography revealed increased left ventricular (LV) posterior wall thickness (1.57 versus 1.37 ± 0.02; n = 16) and LV mass in TgβARKnt compared to non-transgenic littermate controls (NLC) 4 weeks after TAC or Sham surgery. Interestingly, despite enhanced hypertrophy at baseline and after acute pressure overload, the progression to HF was paradoxically inhibited in TgβARKnt mice during chronic pressure overload with preserved cardiac function (% Ejection Fraction 57.3 versus 37.3 ± 2.0; n = 11, 10). Further, βARKnt expression limited adverse left ventricular remodeling, with reduced interstitial fibrosis (% area fibrosis 4.1 versus 9.2 ± 0.8; n = 11, 9 hearts) and preserved β-adrenergic receptor density 4 weeks after surgery. The effect of cardiac βARKnt expression was not consistent with alterations in GRK2 activity at GPCRs as neither GRK2 peptide inhibition (TgβARKct) nor GRK2 overexpression alter hypertrophy, and overexpression hastens HF development. Further, TgβARKnt mice exhibit reduced epididymal white adipose content and altered mitochondrial respiration, suggesting altered cardiac metabolism. These data support the idea that the βARKnt peptide embodies a distinct functional interaction and that βARKnt-mediated regulation of β-adrenergic receptor density may provide a novel means of cardioprotection during pressure-overload induced HF.