PDE4 activity associated with AKAP3. COS cells, untransfected or transfected with AKAP3 and Pde4a, were immunoprecipitated with IgG, anti-AKAP3, and anti-AKAP3 blocked with antigenic protein, then assayed for PDE activity in the presence or absence of Rolipram. PDE activity is presented as mean ± SEM of three independent experiments. Data was analyzed by ANOVA followed by Tukey multiple comparison. A significant (P < 0.05) difference in PDE activity is denoted by an asterisk compared to all other treatments.