FIGURE 3.
Inhibition of PP2, PP4, or PP5 expression does not alter sst2A receptor dephosphorylation. HEK293 cells stably expressing the rat sst2A receptor were transfected with PP2 siRNAs (A), PP4 or PP5 siRNAs (B), or a nonsilencing RNA (CTL) for 72 h and then exposed to 1 μm SS-14 for 5 min. 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. The levels of phosphorylated sst2A receptors (upper panels) and total sst2A receptors (lower panels) were then determined by Western blot analysis. siRNA knockdown was confirmed using pan-PP2, PP4, and PP5 antibodies. Western blots shown are representative of four independent experiments for each condition. The positions of molecular mass markers are indicated on the left (in kDa).