FIG. 4.

Direct phosphorylation of PDE3B at Ser²⁷³ by Akt in vitro. PDE3B-WT, PDE3B-S273A, PDE3B-S274A, and PDE3B-S296A were immunoprecipitated (IP) with antibodies to HA from CHO-IR cells stably expressing the corresponding protein and were then either subjected to immunoblot analysis with antibodies to HA (A) or incubated for 5 min at 30°C with or without 1 μg of activated Akt prepared as described in Materials and Methods (B). The immunoprecipitates from panel B were then subjected to SDS-PAGE, and ³²P incorporation into PDE3B proteins was visualized by autoradiography. Data are representative of three independent experiments.