Stimulation of PDE3A2 and PDE3A1 activity in response to PKC and PKA activation. (A) HEK293 cells were transfected with FLAG-tagged PDE3A2, with and without alanine substitution at S428, and treated with 10 ng/mL PMA for 15 min or with 1 mM dBcAMP for 1 h. (B) HEK293 cells were transfected with FLAG-tagged PDE3A1, with and without alanine substitutions at S312 and S428, and then treated with 1 µM isoproterenol for 90 s, with 10 ng/mL PMA for 15 min, or with 1 mM dBcAMP for 1 h. PDE3 activity was assayed as described. PDE3A constructs were immunoprecipitated with anti-FLAG antibody, and phosphorylation was analyzed by immunoblotting with anti-FLAG and phosphospecific antibodies as indicated.