Fig. 7.

Rate of agonist-induced internalization of a phosphorylation negative sst2A receptor mutant. CHO cells stably expressing the phosphorylation negative sst2A receptor, Phos−/sst2A, were incubated for the times shown at 37 C with 100 nm SS14 (●), 1 μm KE108 (▴), or 1 μm SOM230 (■). Cell surface receptors were then measured by ELISA as described in Materials and Methods and expressed as a percent of untreated control cells. Shown is the mean ± sem of cell surface receptors determined in replicate samples in a single experiment, representative of two to five independent experiments. Where not visible, error bars fell within the symbols. Nonlinear regression curve fitting to a one-phase exponential decay was performed using GraphPad Prism. The half-times for receptor internalization from multiple independent experiments was 32.9 ± 3.6 min with SS14 (n = 5) and greater than 10 h with KE108 and SOM230.