S-Palmitoylation-Dependent Regulation of Cardiomyocyte Rac1 Signaling Activity and Cardiac Hypertrophy

S-palmitoylation is a reversible lipid modification that regulates trafficking, localization, activity, and/or stability of protein substrates by serving as a fatty acid anchor to cell membranes. However, S-palmitoylation-dependent control of signal transduction in cardiomyocytes and its effects on cardiac physiology are not well understood. We performed an in vivo gain-of-function screen of zinc finger Asp-His-His-Cys (zDHHC) family S-acyl transferases that catalyze S-palmitoylation and identified the Golgi-localized enzyme zDHHC3 as a critical regulator of cardiac maladaptation. The closely-related enzyme, zDHHC7, also induced severe cardiomyopathy but this effect was not observed with overexpression of plasma membrane enzyme zDHHC5, endoplasmic reticulum enzyme zDHHC6, or Golgi enzyme zDHHC13. To identify effectors that may underlie zDHHC3-induced cardiomyopathy we performed quantitative site-specific S-acyl proteomics in zDHHC3-overexpressing cells that revealed the small GTPase Rac1 as a novel substrate. We generated cardiomyocyte-specific transgenic mice overexpressing zDHHC3, which develop severe cardiac disease. Cardiomyopathy and congestive heart failure in zDHHC3 transgenic mice are preceded by enhanced S-palmitoylation of Rac1 and induction of additional Rho family small GTPases including RhoA, Cdc42, and the Rho family-specific chaperone RhoGDI. In contrast, transgenic mice overexpressing an enzymatically-dead mutant of zDHHC3 do not exhibit this profound induction of RhoGTPase signaling or develop cardiac disease. Rac1 S-palmitoylation, plasma membrane localization, activity, and downstream hypertrophic signaling were substantially increased in zDHHC3 overexpressing hearts. Taken together, these data suggest inhibition of zDHHC3/7 S-acyl transferase activity at the cardiomyocyte Golgi or disruption of Rac1 S-palmitoylation as novel therapeutic strategies to treat cardiac disease or other diseases associated with enhanced RhoGTPase signaling.