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. 2010 Feb;24(2):436–446. doi: 10.1210/me.2009-0315

Fig. 6.

Fig. 6.

Partial agonistic properties of SOM230. A, HEK293 cells stably expressing sst2A were transfected with empty vector (MOCK) or GRK2 for 2 d. Cells were either not exposed or exposed to 1 μm SS-14, 1 μm octreotide, 10 μm SOM230, or 1 μm L-779,976 for 5 min. The levels of phosphorylated sst2A receptors and total sst2A receptors were determined by Western blot analysis (upper panel). A, HEK293 cells stably expressing sst2A were transfected with empty vector (MOCK) or GRK2 for 2 d. Cells were either not exposed or exposed to 1 μm SS-14, 1 μm octreotide, 10 μm SOM230, or 1 μm L-779,976 for 20 min. Receptor sequestration, quantified as the percent loss of cell-surface receptors in agonist-treated cells, was measured by ELISA (lower panel). B, HEK293 cells stably expressing sst2A were either not exposed or exposed to 1 μm octreotide, 10 μm SOM230, or 10 μm BIM-23627 for 5 min, and then treated with 1 μm SS-14 for an additional 5 min in the presence of octreotide, SOM230, or BIM-23627. The levels of phosphorylated sst2A receptors and total sst2A receptors were determined by Western blot analysis (upper panel). B, HEK293 cells stably expressing sst2A were either not exposed or exposed to 1 μm octreotide, 10 μm SOM230, or 10 μm BIM-23627 for 5 min and then treated with 1 μm SS-14 an additional 20 min in the presence of octreotide, SOM230, or BIM-23627. Receptor sequestration, quantified as the percent loss of cell-surface receptors in agonist-treated cells, was measured by ELISA (lower panel). The Western blots shown are representative for two independent experiments each. ELISA data are presented as the mean ± sem from four independent experiments performed in quadruplicate. The results were analyzed by two-way ANOVA followed by the Bonferroni posttest (*, P < 0.05, significant increase compared with untreated cells; #, P < 0.05, significant decrease compared with SS-14-stimulated cells). Note that overexpression of GRK2 facilitated phosphorylation and internalization of the SOM-activated sst2A receptor, and that SS-14-induced phosphorylation and internalization was effectively inhibited by SOM230.