'Clamping' actin in polymerized form in electropermeabilized neutrophils inhibits oxidase activation

Electro-permeabilized neutrophils take-up small membrane-impermeant molecules into their cytoplasm, yet retain the ability to activate their oxidase and to transiently polymerize actin in response to f-met-leu-phe (fmlp). Using this system phalloidin was introduced into the cytosol in order to determine whether polymerization of actin affects oxidase activation. Cytosolic phalloidin prevented the depolymerization of actin following stimulation with fmlp, which was consequently “clamped” in the polymerized form during oxidase activation. Under these conditions oxidase activation was inhibited, the extent of inhibition being related to the level of polymerization at which the actin was “clamped”. It was concluded that the actin polymerization which accompanies stimulation with fmlp interacts with other intracellular signals to limit oxidase activation