Abstract

A very rapid cellular event that follows chemotactic stimulation of leucocyte and cellular slime mould amoebae is a massive polymerization of G to F actin and its association with the cytoskeleton. In the cellular slime moulds this event occurs within 3–5 sec of cell surface binding of chemoattractants. It is correlated with rapid pseudopodium extension and may be a cell orientation mechanism. Curiously, before an amoebae moves away in the direction of its new pseudopodium it rounds up or “cringes” for 10–20 sec, an event correlated with a massive actin depolymerization. Transduction of the chemotactic signal involves Ca2+ release from internal stores by inositol trisphosphate.