Studies of signal transduction in the respiratory burst-associated stimulation of fMet-Leu-Phe-induced tubulin tyrosinolation and phorbol 12-myristate 13-acetate-induced posttranslational incorporation of tyrosine into multiple proteins in activated neutrophils and HL-60 cells.

A specific stimulation of tubulin tyrosinolation in human neutrophils (PMNs) is induced by the synthetic peptide chemoattractant N-formylmethionylleucylphenylalanine (fMet-Leu-Phe), and this stimulation is closely associated with activation of the NADPH oxidase-mediated respiratory burst (Nath, J., and Gallin, J. I. (1983) J. Clin. Invest. 71, 1273-1281). In contrast, along with tubulin tyrosinolation, a distinctly different respiratory burst-associated random posttranslational incorporation of tyrosine into multiple PMN proteins is observed in PMNs stimulated with the phorbol ester phorbol 12-myristate 13-acetate (PMA) or sn-1,2-dioctanoylglycerol (DAG). In studies exploring the mechanism(s) of signal transduction for these distinct neutrophil responses, we found that the fMet-Leu-Phe-induced stimulation of tubulin tyrosinolation in PMNs and in differentiated HL-60 cells is completely blocked by pertussis toxin, while the PMA-induced random incorporation of tyrosine is not inhibited. We also found that expression of the fMet-Leu-Phe-mediated stimulation of tubulin tyrosinolation in HL-60 cells is correlated with increases in the specific activity of protein kinase C and with the acquisition of respiratory burst activity which occur during induced myeloid maturation of these cells. Furthermore, both the fMet-Leu-Phe-induced stimulation of tubulin tyrosinolation and the PMA or DAG-induced random posttranslational incorporation of tyrosine into multiple proteins in activated neutrophils, were found to be reversibly inhibited (greater than 70%) by the protein kinase inhibitors 1-(5-isoquinolinesulfonyl)piperazine (C-I) and 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), in parallel with inhibition of superoxide (O2-) generation. In related studies, we also found that fMet-Leu-Phe-stimulated O2- production is comparably inhibited by C-I and H-7, but in a highly temperature-dependent manner. Inhibition was observed only when C-I or H-7 is added to PMNs at physiologic temperature, i.e. 37 degrees C. Interestingly, inhibition of the PMA-induced O2- generation by C-I or H-7 was not found to be similarly temperature-dependent. Considered together, these findings argue against the suggestion that there is a protein kinase C-independent pathway for activation of the respiratory burst in neutrophils stimulated with N-formyl peptides.