FIGURE 1.
Calyculin A but not okadaic acid prevents sst2A receptor dephosphorylation. HEK293 cells stably expressing rat sst2A were treated with calyculin A (A) or okadaic acid (B) for 10 min at the indicated concentrations and then exposed to 1 μm SS-14 for 5 min in the presence of calyculin A or okadaic acid. Cells were washed three times with ice-cold PBS and then were directly lysed or incubated for 15 or 30 min in culture medium (washout) at 37 °C in the presence of calyculin A or okadaic acid. The levels of phosphorylated sst2A receptors (upper panels) and total sst2A receptors (lower panels) were then determined by Western blot analysis. Note that calyculin A inhibited sst2A receptor dephosphorylation in a dose-dependent manner. Western blots shown are representative of three independent experiments for each condition. The positions of molecular mass markers are indicated on the left (kDa).