The effect of putative protein kinase C inhibitors, K252a and staurosporine, on the human neutrophil respiratory burst activated by both receptor stimulation and post‐receptor mechanisms

Abstract

Two compounds, reported to be potent inhibitors of protein kinase C (PKC), K252a and staurosporine, have been examined in order to gain further information as to the possible role played by PKC in the signal transduction sequence of the neutrophil respiratory burst as determined by superoxide (O−2) production. A number of stimuli were used in the study, some acting at receptors i.e. fMet‐Leu‐Phe (fMLP), opsonized zymosan and heat‐aggregated IgG (HAGG), one acting on a G‐protein, fluoride, and two direct PKC activators, dioctanoylglycerol (diC8) and phorbol myristate acetate (PMA). K252a and staurosporine inhibited the respiratory burst with all the stimuli but the order of agonist sensitivity was very different with the two inhibitors. For K252a‐induced inhibition of O−2 release, the order of potency was fluoride > fMLP, HAGG > opsonized zymosan > PMA, DiC8. For staurosporine‐induced inhibition of O−2 release, the order of potency changed to fluoride > DiC8, PMA > HAGG, fMLP > opsonized zymosan. The significance of this unexpected difference in relative rank order of potency is discussed with reference to the reported mechanism of action of the two inhibitors and the events involved in the oxidative burst. Staurosporine at low concentrations increased the fMLP‐stimulated O−2 response by 100%, the maximum effect occurring at 35 nm. To the extent that the compounds used are specific inhibitors of PKC, these findings support a role for the enzyme PKC in stimulus‐activation coupling in O−2 generation with all the stimuli used in this study.

Activation of the Leukocyte NADPH Oxidase Subunit p47phox by Protein Kinase C. A Phosphorylation-Dependent Change in the Conformation of the C-Terminal End of p47phox

“…In intact phagocytes and B lymphocytes, however, the phosphoryla-tion of p47 phox appears to be the key event in the activation of the leukocyte NADPH oxidase. Phosphopeptide maps of p47 phox from neutrophils and EBV-transformed B lymphocytes activated by phorbol myristate acetate suggest that this phosphorylation is accomplished by protein kinase C (El Benna et al, 1994a, 1996, a finding consistent with earlier studies using inhibitors of protein kinase C and phosphatases (Heyworth et al, 1995;Arai et al, 1993;Twomey et al, 1990;Ding & Badwey, 1992;Steinbeck et al, 1991;Garcia et al, 1992;Djerdjouri et al, 1995;Suzuki et al, 1995). We show here that the phosphorylation of p47 phox by protein kinase C caused a change in the conformation of the protein in the vicinity of C378, which lies only 13 residues in from the C-terminus of the molecule.…”

Staurosporine stimulates phospholipase D activation in human polymorphonuclear leukocytes

“…The significance of PA elevation in staurosporine-treated cells is not known, but staurosporine has various activating and priming properties. In PMNs, staurosporine induces exocytosis [33] and actin polymerization [34] and, under certain conditions, potentiates the respiratory burst mediated by chemoattractants [20,35]. In other cells, staurosporine promotes changes in morphology and differentiation similar to those induced by phorbol esters [36].…”

Cross Talk between Neuroregulatory Molecule and Monocyte: Nerve Growth Factor Activates the Inflammasome

“…The TrkA inhibitors (K252a: 15.07±1.81 pg/ml, p<0.001 and PLX7486: 14.52±2.09 pg/ml, p<0.001) effectively blocked the NGF mediated increase of IL-1β ( Fig 1A ). Apart from inhibiting phosphorylation of TrkA, K252a, a fungal alkaloid, also inhibits protein kinase C [ 46 ]. Thus, to confirm the inhibitory effect of specific NGF/TrkA interaction, a novel TrkA inhibitor, PLX7486, was used.…”