Figure 3.

Treatment with the calcium ionophore A23187 and the PKC activator PMA rescues the secretion defect exhibited by antigen-stimulated cells expressing dominant-negative Cdc42 and Rac. RBL-2H3 cells were infected with vaccinia virus containing empty vector, the different forms of Cdc42 and Rac, or uninfected, for 6 h at 37°C. Cells were then stimulated with either 20 nM PMA for 5 min followed by 1 μM A23187 for 1 h or 100 ng/ml DNP/BSA for 1 h. Degranulation is given as the percent of total cellular β-hexosaminidase released, as measured by treatment of RBL-2H3 cells in parallel with 0.5% Triton X-100. Error bars represent the standard deviation of four independent experiments.