FRAP analysis of ERK2-EGFP in the absence and presence of Us2. (A) Images of live PK15 cells cotransfected with pCIneo and ERK2-EGFP (i), Us2 and ERK2-EGFP (ii), or Us2GAAX and ERK2-EGFP expression plasmids (iii) immediately before, immediately after, or 28.8 s (i), 40 s (ii), and 40.1 s (iii) after the area outlined in the red box were photobleached using an Olympus FV1000 laser-scanning confocal microscope. The boxed blue area is proximal to the photobleached region, and the boxed orange area is distal to the photobleached region. The fluorescence signal is ERK2-EGFP. Scale bars are 10 μm. (B) Quantitation of fluorescence intensity of the photobleached area, as well as control proximal and distal areas, over time. Shown are data for PK15 cells cotransfected with pCIneo and ERK2-EGFP (i), cells cotransfected with Us2 and ERK2-EGFP expression plasmids (ii), and cells cotransfected with Us2GAAX and ERK2-EGFP expression plasmids (iii).