155 Protein Prenylation is Essential for Cardiomyocyte Proliferation

Abstract

In early neonatal life, the mammalian heart undergoes maturation to facilitate a rapid postnatal increase in function to enhance the cardiovascular system for postnatal life and growth. Coinciding with maturation is diminished cardiomyocyte (CM) proliferative capacity meaning a lack of regeneration following injury or disease resulting in depleted cardiac function. Recently, it has been identified that the mevalonate pathway is crucial for CM proliferation and is shutdown during maturation. This vital anabolic pathway is responsible for metabolic intermediates, farnesyl (FPP) and geranylgeranyl pyrophosphate (GGPP), utilized in protein prenylation, and biomolecules including coenzyme Q10 and cholesterol. However, it is currently unclear which component(s) are responsible for driving CM proliferation. To determine the mechanism, human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) were exposed to inhibitory small molecules and metabolites of the mevalonate pathway with CM proliferation assessed through immunocytochemistry. These data indicated that prenylation components are essential for CM proliferation with only mevalonate, FPP and GGPP capable of rescuing CM proliferation after inhibition of the pathway. To further illustrate the importance of prenylation in CM proliferation, gene knockdown of the beta subunits of both FPP and GGPP transferases was performed using siRNA transfection which also exhibited significant decreases in CM proliferation. To determine which prenylated proteins are present in CMs, and potentially involved in proliferation, a bioinformatics approach was undertaken and identified 107 CM-regulated differentially expressed prenylated proteins. If we can identify the mechanism of how the mevalonate pathway regulates CM proliferation, this may provide therapeutic targets capable of regenerating lost CMs.