KCND3 and hydrops fetalis: We found that in the Ad-Kv4.3 transfected HF LV, CaMKII autophosphorylation was significantly reduced with a much larger reduction in the compartmentalized CaMKII activity in the SR region which was manifested by a much greater inhibition of the PLB phosphorylation at Thr17, a CaMKII-dependent phosphorylation site (Figure 2).