Figure 4.

Expression of PKG-Iα downregulates PDE3A activity and increases cAMP levels in vitro. PKG-Iα was transiently expressed in PKG-Iα–deficient HEK293T cells; as a negative control, the cells were transfected with an empty vector. A, immunoprecipitation analysis identified an association of PDE3A with PKG-Iα. PKG-Iα–expressing cells also exhibit a significant decrease in PDE3 activity (B) and a significant increase in cAMP levels (C). Data represent mean ± SEM, n = 3. ∗p < 0.05 versus empty vector. D, comparative analysis of human and mouse PDE3A amino acid sequences using NetPhos 3.1 revealed conserved PKG-specific phosphorylation sites (shown in red). HEK293T, human embryonic kidney 293T cells; PDE3A, phosphodiesterase 3A; PKG-Iα, protein kinase G-Iα.