Fig. 2. Agonist-induced endocytosis of LPA₁ is inhibited in ß-arrestin 1/2 double knockout mouse embryo fibroblasts. (A) Wild-type MEFs were transiently transfected with plasmids encoding either FLAG-tagged LPA₁ or HA-tagged ß₂AR and then incubated in the presence or absence of agonist (10 µM LPA or 20 µM isoproterenol, respectively) for 30 minutes prior to indirect immunofluorescence localization of the receptor proteins either in the presence or absence of detergent permeabilization. (B) ß-arrestin 1/2 double knockout MEFs were transiently transfected with plasmids encoding either FLAG-tagged LPA₁ or HA-tagged ß₂ARs and incubated in the presence or absence of agonist, as above, prior to indirect immunofluorescence localization of the receptor proteins. Bar, 10 µm.