Actin switches in phagocytosis.

Exposure of phagocytes to non-spherical particles has provided evidence for multiple actions of the actin system in force generation. For the uptake of long cylindrical particles, a "motile actin clamp" mechanism is proposed. When a phagocyte is engaged with an hour-glass-shaped particle, it exerts contractile activity alternatively at the far end of the particle or at its concave region. Phagocytes can switch within seconds between these different strategies of taking up a particle. This response switching is based on reprogramming the pattern of actin polymerization and depolymerization. The choice between different strategies of interaction with a particle increases the probability of engulfing the entire particle or at least a portion of it. Finally, a switch to actin disassembly enables a phagocyte to release a particle that turns out to be too big to be enclosed.