Fig. 1.

PDE4B controls subsarcolemmal but not cytosolic cAMP. (A) YFP fluorescence in neonatal cardiac myocytes expressing either Epac2-CYTO (top) or Epac2-PM (bottom). (B–D) Wild-type and PDE4BKO myocytes expressing Epac2-CYTO (B) or Epac2-PM (C,D) were treated for the indicated times with Iso (10 nM) alone, or Iso (10 nM) and Rol (10 µM) followed by IBMX (100 µM) and Fsk (50 µM). The average ratio R/R₀ (R = CFP/FRET) is reported and the number of cells analyzed (n) includes data from at least four experiments. Data were analyzed using a two-way ANOVA. Error bars correspond to the s.e.m. Rol, rolipram; Fsk, forskolin.