The localization of pNHE3 and of NaKA in EF-directed- versus random cellular movement. The colocalization of pNHE3 with ß-actin (A) and of NaKA with vinculin (B) on the leading edge of a cell in both cathode (Calvaria)- and anode (SaOS-2)-directed cells. First and third row: randomly migrating control cells. Second and fourth row: polarized cells that persist in a direction under an applied EF. White arrows with "+" and "-" poles indicate the migration direction under an applied EF. Yellow arrows indicate the magnified view and correspond to the entire row. Bar: 50 μm.