Figure 6. Agonist-induced phosphorylation and dephosphorylation of the human sst₃ receptor.

Left panel, HEK293 cells stably expressing the sst₃ receptor were either not exposed or exposed to the indicated concentrations of SS-14 for 10 minutes at room temperature. Second panel, cells were exposed to 1μM SS-14 at room temperature for the indicated time periods. Third panel, cells were exposed to 1μM SS-14 for 10 minutes, washed, and incubated in the absence of agonist for 0, 2, 5, 10, 15, 30, 60, or 90 minutes. Fourth panel left, Cells were incubated with the sst₃ antagonist NVP-ACQ090 for 10 minutes before SS-14 exposure at 37°C. Fourth panel right, Cells were exposed to either 1μM SS-14, 0.1μM PMA, or 10μM forskolin for 10 minutes at room temperature. Cells were lysed and immunoblotted with the phosphosite-specific antibodies. Blots were stripped and reprobed with the phosphorylation-independent anti-HA antibody to confirm equal loading of the gel (anti-HA). Representative results from 3 independent experiments are shown. The positions of molecular mass markers are indicated on the left (in kDa).