Figure 8.
Pheromone induces asymmetric receptor phosphorylation in cells unable to polarize the receptor. (A) G1-synchronized YDB111 cells, which express a reporter that specifically binds to the unphosphorylated form of the receptor (Sst2-GFP) and a form of the receptor that cannot be internalized (Ste27XR-mCherry), were treated with 1.2 μM pheromone (top) or with 1.2 μM pheromone and 200 μM LatA (bottom). Images were acquired every 15 min. Arrows indicate the polarized localization of Sst2-GFP. (B) Quantification of Sst2-GFP polarization. The Sst2-GFP polarity indices were obtained as described in the legend to Figure 2. The bar graphs represent the mean polarity index ± SD at each time point (n = 15). *p < 0.001 and **p < 0.0002 for the comparisons of treated to untreated cells at each time point. (C) Effect of LatA on F-actin in YDB111 cells. Representative cells treated with pheromone and LatA at 0 time as described in A are shown. F-actin structures were not detectable at the 5- and 75-min time points.