FIG 3 .

Plasma membrane proteins (Ste2 and Mup1) are not endocytosed without Arp2/3. (A) Internalization of the Ste2 pheromone receptor was assayed after 40-min incubation in the presence of α-factor pheromone. This results in dominant vacuolar accumulation of Ste2-GFP in WT cells with some signals visible as vesicles trafficking en route to the vacuole. In arp2 cells, no strong vacuolar signal or moving vesicles were observed during time-lapse movies (not shown). (B) Mup1 internalization was stimulated by the addition of methionine. Mup1-GFP signal disappeared in WT cells at the plasma membrane, but it was still visible in arp2 cells (right). When Mup1 was coupled to the pH-sensitive GFP variant, pHluorin, the Mup1-pHluorin signal almost completely disappeared in WT cells upon addition of methionine, while Mup1-pHluorin was still observed in arp2 cells that carried a CaRho1 overexpression, treated with sorbitol, and incubated overnight (left). Bar, 10 µm.