Fig. 4. Recovery of PKA activity by PDE2 overexpression in RAS2^val19 (RAS^v) cells. (A) Iodine–iodide staining of wild-type and RAS2^val19 cells carrying either the empty vector (top panels) or overexpressing PDE2 (lower panels). (B) Heat shock sensitivity (shift from 30°C to 52°C) of wild-type and RAS2^val19 cells carrying either the empty vector (wt, open squares; RAS2^val19, open circles) or overexpressing PDE2 (wt, filled squares; RAS2^val19, filled circles). (C) Catalase activity in wild-type and RAS2^val19 cells carrying the empty vector (–) and overexpressing PDE2 (+). The catalase activity of Ras2::LEU2 mutant cells carrying the vector is included for comparison.