MAPK3 and cardiac hypertrophy: Western blotting analyses of signaling molecules downstream of Rac1 revealed a substantial increase in the expression of the Rac1 effector, p21-activated kinase 1 (PAK1) (62, 63), in Zdhhc3-overexpressing hearts (Fig. 3, G and H) as well as increased phosphorylation of extracellular signal–regulated kinases 1 and 2 (ERK1/2) (Fig. 3G), which are activated by PAK1 (64, 65, 66) and function as transducers of cardiac hypertrophy (67, 68, 69).