AKT-mTOR signaling-mediated rescue of PRKAG2 R302Q mutant-induced familial hypertrophic cardiomyopathy by treatment with β-adrenergic receptor (β-AR) blocker metoprolol

Abstract

Background: Protein kinase AMP-activated non-catalytic subunit gamma 2 gene (PRKAG2) cardiac syndrome, caused by mutations in PRKAG2, often shows myocardial hypertrophy and abnormal glycogen deposition in cardiomyocytes. However, it remains incurable due to a lack of a management guideline for treatment. Methods: We constructed a fluorescently labeled adenovirus carrying the wild-type or R302Q mutant of the PRKAG2 gene, infected neonatal rat cardiomyocytes (NRCMs) and H9C2 cell lines, and then analyzed changes in AMP-activated protein kinase (AMPK) activity, cell hypertrophy, glycogen storage, and cell proliferation when presence or absence of metoprolol or protein kinase A (PKA) inhibition H89, and then analyzed the changes in AKT-mTOR signal transduction activity. Results: Overexpression of PRKAG2 R302Q in primary cardiomyocytes increased the activity of AMPK, induced cellular hypertrophy and glycogen storage, and promoted the phosphorylation levels of AKT-mTOR signaling pathway. Application of either β1-adrenergic receptor (β1-AR) blocker metoprolol or PKA inhibitor H89 to the cardiomyocytes rescued the hypertrophic cardiomyopathy (HCM)-like phenotypes induced by PRKAG2 R302Q, including suppression of both AKT-mTOR phosphorylation and AMPK activity. Conclusions: The current study not only determined the mechanism regulating HCM induced by PRKAG2 R302Q mutant, but also demonstrated a therapeutic strategy using β1-AR blocker to treat the patients with PRKAG2 cardiac syndrome.