Figure 5. Increased levels of PKA dependent phosphorylation of phospholamban in PDE3A^−/− hearts.

Western blots of WT and PDE3^−/− heart lysates (40 μg), illustrating the effect of PDE3A ablation on phosphorylation of PLN at PKA-dependent site Serine 16 (S¹⁶). A) PDE3A ablation increased phosphorylation of PLN (pPLN), with respect to total PLN at residue serine 16. Calreticulin was used as indicator of equal loading conditions. B) Bar graph summarizing p Ser¹⁶PLN/PLNtotal ratios in WT and PDE3A ^−/− hearts; ~2 fold increase in PDE3^−/− lysates,*p< 0.01 versus WT (n=3 independent experiments, each with duplicate samples from 3 WT and 3 PDE3^−/− heart lysates). In some experiments as a result of the protein samples heating, PLN run on a SDS-PAGE gel in its monomeric (5kDa) and pentameric forms (25kDa). Total PLN was used for the analyses.