Inhibition of chemotactic peptide-induced development of cell polarity and locomotion by the protein kinase C inhibitor CGP 41 251 in human neutrophils correlates with inhibition of protein phosphorylation.

Several protein kinase inhibitors of the staurosporine type displaying different enzyme specificity were used to study the role of protein kinase C (PKC) in motile neutrophil functions. Effects on protein phosphorylation, F-actin localization, morphology, and locomotion were determined. Only staurosporine, but not another inhibitor more specific for PKC (CGP 41 251) or inhibitors of cyclic nucleotide-dependent kinases (KT 5720, KT 5822), induced formation of F-actin-enriched surface protrusions at nanomolar concentrations in initially spherical neutrophils. The inhibitor with the highest specificity for PKC, CGP 41 251, had no effect on morphology and F-actin localization of resting cells up to 1 microM. However, this inhibitor suppressed front-tail polarity and locomotion in chemotactic peptide-stimulated cells. The cells became nonpolar with surface projections instead. Inhibition of front-tail polarity induced by CGP 41 251 strongly correlated with inhibition of in situ phosphorylation of a 67-kDa protein (IC50 = 0.2 microM), whereas induction of polarity by chemotactic peptide was associated with increased phosphorylation of this protein. Kinase inhibitors inactive on PKC (KT 5720, KT 5822) did not affect development of front-tail polarity. We conclude that a kinase involved in the phosphorylation of a 67-kDa protein, very likely a PKC isoform, may be important for the development of cell polarity and locomotion. In contrast, chemotactic peptide-induced formation of actin-containing protrusions may not be mediated by this enzyme.