Fig. 3. Mutually exclusive distribution of myosin II and cortactin. (A-F) Myosin arrangement in serum stimulated (A-C) and PDBu-stimulated (D-F) cells. Clustering of cortactin interferes with myosin assembly, and progression of podosome formation causes the long-term displacement of myosin filaments (arrows in D'-F'). Scale bar: 20 µm. (G) Selected frames from a video sequence (corresponding to the supplemental movie) of a live A7r5 cell double transfected with DsRed SM22 (to highlight podosome formation sites) and GFP regulatory myosin light chain (rMLC). The clustering of cortactin causes the transient dispersion of myosin (arrows indicate a selected event) which persist for several minutes. Upon disintegration of the cortactin cluster myosin re-assembles within a few minutes. Scale bar: 10 µm.