Cell surface topography controls phagocytosis and cell spreading: The membrane reservoir in neutrophils

Neutrophils exhibit rapid cell spreading and phagocytosis, both requiring a large apparent increase in the cell surface area. The wrinkled surface topography of these cells may provide the membrane reservoir for this. Here, the effects of manipulation of the neutrophil cell surface topography on phagocytosis and cell spreading were established. Chemical expansion of the plasma membrane or osmotic swelling had no effects. However, osmotic shrinking of neutrophils inhibited both cell spreading and phagocytosis. Triggering a Ca²⁺ signal in osmotically shrunk cells (by IP₃ uncaging) evoked tubular blebs instead of full cell spreading. Phagocytosis was halted at the phagocytic cup stage by osmotic shrinking induced after the phagocytic Ca²⁺ signalling. Restoration of isotonicity was able to restore complete phagocytosis. These data thus provide evidence that the wrinkled neutrophil surface topography provides the membrane reservoir to increase the available cell surface area for phagocytosis and spreading by neutrophils.