Neutrophil control of formylmethionyl-leucyl-phenylalanine induced mobilization of secretory vesicles and NADPH-oxidase activation: effect of an association of the ligand-receptor complex to the cytoskeleton.

The stimulus formylmethionyl-leucyl-phenylalanine (FMLP) interacts with neutrophils and generates signal(s) in the cells that induces mobilization of the secretory vesicles as well as activation of the superoxide anion/hydrogen peroxide generating NADPH-oxidase. Binding, at 15 degrees C, of FMLP to its neutrophil surface receptor is followed by an association of the ligand-receptor complex to the cell cytoskeleton, and this association occurs concomitant with a desensitization of the cells with respect to activation of the NADPH-oxidase. Other stimuli can still activate the oxidase (in fact even induce a primed response), indicating that the observed phenomenon is stimulus specific and could not be accounted for by an effect on the oxidase itself, but rather that the association of the ligand-receptor complex to the cytoskeleton eliminates the capacity of the complex to generate the signal(s) that activates the NADPH-oxidase. The cytoskeleton associated ligand-receptor complex generates, however, the signal(s) responsible for mobilization of the secretory vesicles, to the plasma membrane, and this mobilization occurs without any increase in the intracellular concentration of free Ca2+.