The study shows that diacylglycerols (DAGs) as physiological activators of protein kinase C induce characteristic shape changes in human neutrophil granulocytes. In contrast to chemotactic peptides, which can induce front-tail polarity characterized by a contracted tail and an expanding front, DAGs elicit the formation of non-polar cells with surface projections. These cells exhibit a distinct type of motility characterized by vigorous and continuous shape changes without front-tail polarity and without the unidirectional movement and cytoplasmic streaming seen in polarized cells. In neutrophils exposed to DAGs, F-actin is shifted to the cell periphery and mainly into the surface projections of activated cells. DAGs induce the formation of large intracellular vacuoles in neutrophils producing surface projections, and these vacuoles persist after the cells have reacquired a spherical shape. Combined stimulation of human neutrophils with DAG and fNLPNTL results in a suppression of peptide-induced polarity and the formation of non-polar motile cells resembling those stimulated with DAG alone. These results suggest that the diacylglycerol-protein kinase C pathway may be instrumental in transducing or modulating signals to both the locomotor apparatus and the exocytotic and/or pinocytic system of the cell. Neutrophil stimulation with DAGs thus represents a useful model with which to study further the hypothesis that distinct types of neutrophil shapes and movements are preferentially associated with distinct functions and to characterize signalling pathways.
A polyclonal, monospecific rabbit antibody to human erythrocyte spectrins cross-reacted with two sets of proteins (a doublet of 180/200K and a triplet of 67–66-65K; K = 10(3) Mr) in the parasitic protozoon Trypanosoma brucei brucei. Except for the 66K protein, the cross-reacting proteins are localized in the flagellum, on the basis of evidence from cell fractionation and immunofluorescence microscopy. Immunogold labelling and electron micrographs further revealed that the spectrin-like proteins are confined to the paraflagellar rod structure. The spectrin-like proteins with apparent molecular weights of 180 and 200 share homology with spectrin band 1, since V8-protease from Staphylococcus aureus generated similarly sized, antigenic peptides from these proteins. The results indicate homology between the cross-reacting proteins and human red cell spectrin.