Mapping of the function of DM14 domains. A. Western blot of recombinant PDE4D5 protein (fragment IX) probed with anti-phospho PDE4D or anti-PDE4D in the presence and absence of PKA or CC2D1A (I). B schematic diagram of PDE4D phosphorylation at (S126) by PKA in the presence and absence of CC2D1A. C. In vitro PDE4D activity assay of recombinant PDE4D5 (IX) after pre-incubation with BSA, PKI (specific PKA inhibitor) or CC2D1A (fragments I, II, III, IV, V, VI, VII) in the presence and absence of PKA. BSA was used as a control to validate the specificity of the responses of the different CC2D1A constructs on the inhibition of PDE4D5 activity in the presence of PKA.