Fig. 4. Inducible overexpression of EGFP-rab11S25N inhibits the rate of recycling of ß₂ARs following a brief exposure to agonist. (A) EGFP-rab11S25N and (B) EGFP-rab11WT. Following treatment with ponasterone () or vehicle () for 72 hours, cells were treated with 5 µM ISO for 20 minutes, washed four times, and incubated in DME-H at 37°C for varying times up to 60 minutes to allow receptor recycling. Surface receptors were determined by incubation with 6 nM [³H]CGP12177 at 0°C and bound radioligand was quantified by scintillation spectroscopy. Each point represents the mean±s.e.m. of three independent experiments. The fraction of receptors that have recycled was plotted as a function of tim e following the removal of agonist and the curves fitted as previously described (Morrison et al., 1996). The zero point represents the 65-70% of receptors that internalized during agonist treatment and was not different in the two groups.