Actin stability on endosomal membrane is controlled by PI(3,5)P₂. MDA-MB-231 cells stably expressing mGFP-F-tractin were treated with DMSO or YM201636 for 2 h, and then imaged live after treatment with 10 µM latrunculin A (LatA). (A) Representative images at 0 and 50 s after LatA treatment. Bar, 5 µm. (B) The change in endosomal actin fluorescence over time after LatA treatment was normalized to initial endosomal actin fluorescence. n = 10–15 cells from 3 independent experiments for each condition.