ROCK is required for S19-MRLC phosphorylation in the cell center, but not in the cell periphery. Top, epifluorescence images of HaCat cells fixed after pretreatment for 1–2 h with 10 μM Y-27632 and 0, 5, and 20 min of 5 nM EGF stimulation. Cells were processed for localization of F-actin, MHC, and pS19-MRLC. Bottom, enlarged views of the regions denoted by the white squares. Bars, 10 μm.