Lysine myristoylation as a novel mechanism for regulating PKA in the heart

University Of Colorado Denver, Aurora CO

Investigators

Abstract

ABSTRACT Cardiovascular disease is a leading cause of death, with an uptick in cardiovascular disease mortality rates in recent years, due in part to the growing obesity crisis. Obesity is associated with many cardiovascular risk factors and increased adiposity can lead to cardiac remodeling and heart failure. One strategy to increase weight loss and improve cardiovascular outcomes is to target beta-adrenergic receptors (β-ARs) in adipose tissue to increase activation of protein kinase A (PKA) and increase energy expenditure. PKA also has important regulatory roles in cardiac tissue. PKA activation increases calcium cycling and contractility in the cardiomyocyte, thus increasing heart function. β-AR agonists, however, were not beneficial for long-term use in heart failure patients. We therefore need alternative mechanisms to activate and regulate PKA in the heart. We recently published that inhibiting histone deacetylase 11 (HDAC11) in adipocytes increased PKA activity and improved metabolic health. HDAC11 does not act like a classic HDAC, but rather, regulates protein function through lysine demyristoylation. Lysine demyristoylation is an understudied post-translational modification, and the biological functional consequences of lysine myristoylation/demyristoylation remain mostly unknown. Our preliminary data demonstrate that inhibition of HDAC11 increases the phosphorylation of PKA substrates in the cardiomyocytes. Our central hypothesis is that increasing lysine myristoylation in the cardiomyocyte (facilitated by HDAC11 inhibition) will beneficially increase heart function by increasing PKA activity. Aim 1 will determine the mechanism of HDAC11 inhibition-mediated increase in PKA activation by quantifying the myristoylation of the A kinase anchoring protein, gravin-α, which is known to facilitate HDAC11 inhibition-mediated PKA activation in adipocytes, through myristoyl-tag click chemistry and gain- and loss-of-function assays. We will also look for novel HDAC11 demyristoylation targets in the cardiomyocyte using click chemistry and mass spectrometry. Aim 2 will determine the functional effects of HDAC11 inhibition in the cardiomyocyte. We will evaluate the effect of HDAC11 inhibition at the cellular level by measuring calcium transients and function in isolated cardiomyocytes. We will generate a novel, inducible, cardiomyocyte-specific HDAC11 knockout mouse and assess cardiac structure and function in vivo using echocardiography, pressure-volume loop hemodynamics, and histological approaches. Finally, we will determine the functional effect of HDAC11 inhibition-mediated increase in PKA activation on disease pathogenesis and measure cardiac structure and function of wild-type and HDAC11 cardiomyocyte specific knockout mice before and after transverse aortic constriction. Together, successful completion of these aims will support the development of HDAC11 inhibitors as a novel therapeutic mechanism to regulate PKA activation and beneficially increase heart function.