FIGURE 2:

Myosin IIA and IIB are distinctly localized to the lamella and myosin activity is required for macropinocytosis. (A, B) HT1080 cells were fixed and labeled with antibodies to myosin IIA (A) or myosin IIB (B) and rhodamine-phalloidin to label actin. (C, D) HT1080 cells were incubated with antibodies against CD98 for 30 min prior to removal of surface antibody, fixed, and labeled with antibodies to myosin IIA (C) or IIB (D). For A–D, boxed regions are enlarged and shown below. (E, F) HT1080 cells were pretreated with either 50 μM blebbistatin or DMSO vehicle for 30 min prior to the addition of dextran (dextran-594 in E, dextran-647 in F) and further incubation for 20 min. Bar graph (F) shows the geometric mean dextran fluorescence measured by flow cytometry, reported as a fraction of DMSO control, from at least three experiments (100,000 cells were counted per experiment). Error bars represent ± SD. An unpaired t test with Welch’s correction was used for comparison of conditions. ****p < 0.0001. Images corresponding to typical dextran fluorescence under each condition are shown, cells are outlined with white dotted lines. Bars, 5 μm.