Fig. 2. Cytochalasin D prevents augmentation of I_CFTR by the cytosolic domain of syntaxin 1A. Whole-cell currents were obtained from 16HBE4o- cells as in Fig. 1. A summary of current density at 110 mV is given for cells under control conditions and cells stimulated with the cAMP cocktail added to the bath solution as indicated under the respective bars. Cells were treated with 0.5 µg/ml of cytochalasin D for 30 minutes prior to whole-cell voltage clamp in the presence and absence of soluble syntaxin 1AC (20 µg/ml) added to the pipette solution. There was no significant difference between ICFTR in the presence and absence of the cytoskeleton-disrupting reagent. ICFTR in the presence of the cytosolic domain of syntaxin 1A was not significantly different from that observed under control conditions.