Abstract P2035: Palmitoylation Of Rac1 Is Required For Cardiomyocyte Hypertrophy And Oxidative Stress

Abstract

Cardiac hypertrophy, the enlargement of cardiomyocytes in response to an increased workload, is a precursor to maladaptive cardiac remodeling and heart failure. Palmitoylation is a post-translational lipid modification which controls the subcellular localization, trafficking, and activity of proteins but has not been extensively studied in the setting of cardiac disease. Previous work from our group shows that transgenic mice with cardiomyocyte-specific overexpression of zDHHC3, a S-acyltransferase which catalyzes palmitoylation, develop severe cardiac hypertrophy which progresses to lethal dilated cardiomyopathy. Palmitoylated levels, as well as total expression, of the small GTPase Rac1 were significantly elevated in the hearts of these transgenic mice compared to control mice suggesting that palmitoylation of Rac1 at Cys-178 may drive this phenotype. Rac1 is required for the development of cardiac hypertrophy and relatedly plays an important role in mediating myocardial oxidative stress as a regulatory subunit of the NADPH oxidase 2 (Nox2) complex. Interestingly, transgenic mice overexpressing zDHHC3 in cardiomyocytes also display increased myocardial oxidative stress. Because of the known importance of Rac1 in regulating cardiac remodeling, we sought to define the role of palmitoylation in controlling Rac1 signaling in cardiomyocytes. To do this, we overexpressed a constitutively active Rac1 mutant, Rac1-G12V, or a constitutively active, palmitoylation-deficient Rac1 mutant, Rac1-G12V/C178S, in neonatal rat cardiac myocytes (NRCMs). Our data suggest that inhibition of Rac1 palmitoylation at Cys-178 protects NRCMs from hypertrophy and oxidative stress induced by hyperactive Rac1 signaling. Furthermore, we found that overexpression of palmitoylation-deficient Rac1 protects against oxidative stress induced by angiotensin II in NRCMs. Future work will interrogate if inhibition of Rac1 palmitoylation at Cys-178 in cardiomyocytes protects against the development of cardiac hypertrophy and myocardial oxidative stress in vivo .