Effect of okadaic acid on relocation of actin, myosin, PP1, and PP2A after antigen stimulation. Adherent monolayers of RBL-2H3 cells that had been incubated overnight with DNP-specific IgE were incubated in a buffer containing 1 μM OA for 45 min and activated with antigen (100 ng/ml DNP-BSA) for 2.5 min (a, c, e, and g). A separate set of cells was left for 45 min in buffer alone as a control and activated with antigen (100 ng/ml DNP-BSA) for 2.5 min (b, d, f, and h). All cells were fixed and proteins were detected as detailed in MATERIALS AND METHODS. Actin (a and b) was detected using an anti-actin mAb and FITC-labeled secondary antibody; myosin (c and d), PP1c (e and f), and PP2Ac (g and h) were detected using specific polyclonal antibodies and FITC-labeled secondary antibodies. The images focus on the basal surface of the cells and are representative of those seen in at least three separate experiments. Bar, 5 μm.