V-1–null cells exhibit reduced F-actin content. (A) F-actin content (as a fraction of WT) in WT cells, V-1–null cells, V-1–null cells expressing FLAG-V-1, and V-1–null cells expressing FLAG-FBM V-1 determined by measuring total cellular fluorescence in cells stained with FITC-labeled phalloidin. Mean and SD values are as follows: WT, 1.00 ± 0.28; V-1–null, 0.73 ± 0.23; V-1–null + V-1, 0.92 ± 0.32; V-1–null + FBM V-1, 0.75 ± 0.21. (B) F-actin content (as a fraction of WT) in WT cells and V-1–null cells determined by measuring the signal for FITC-labeled phalloidin in Triton X-100–insoluble cytoskeletons. Mean and SD values are: WT, 1.00 ± 0.09; V-1–null, 0.73 ± 0.11. (C) Total cellular F-actin content of WT cells (green) and V-1–null cells (red) determined by flow cytometry of cells stained with FITC-labeled phalloidin. Each sample represents ∼30,000 cells (the black peak shows the background fluorescence). Mean and median values in arbitrary fluorescence units (A.U.) are as follows: WT, 6,996 and 6,301; V-1–null, 3,621 and 3,491. **P < 0.01.