Ser1935 controls the architecture of the leading edge and the exclusion of NMII-B from this region. (A) CHO.K1 cells transfected with the indicated GFP-MHCII-B constructs (green in overlay) were plated on fibronectin, allowed to attach for 2 h, treated with IGF-1 for 15 min, fixed, and stained for F-actin (magenta in overlay). Representative examples are shown. (B) CHO.K1 cells transfected with the indicated GFP–MHCII-B constructs (green in overlay) were treated as in A and stained for F-actin (blue in overlay) and endogenous NMII-A (IIA; red in overlay). endo, endogenous. (C) Snapshots of confocal time-lapse videos of wild-type GFP–MHCII-B (top) or the 1935D mutant (bottom). The edge of the cell was obtained from corresponding phase-contrast images. Arrowhead in the wild-type image indicates a protrusion devoid of small puncta corresponding to wild-type NMII-B; arrows in the NMII-B 1935D image indicate small puncta corresponding to the mutant appearing within the protrusion. Bars: (A and C) 10 µm; (B) 5 µm. Images extracted from Videos 6 and 7.