Demethoxyviridin and wortmannin block phospholipase C and D activation in the human neutrophil.
1991
1
The fungal metabolite, wortmannin, has recently been shown to inhibit fMet-Leu-Phe-stimulated superoxide production and phospholipase D (PLD) activation in the human neutrophil.
2
We have found that a close structural analogue of wortmannin, demethoxyviridin, has a similar inhibitory profile but in addition blocks phosphatidylinositol 4,5-bisphosphate-specific phospholipase C and hence inositol 1,4,5-trisphosphate (IP3) formation.
3
Inhibition of fMet-Leu-Phe-stimulated PLD by demethoxyviridin was characteristically non-competitive (IC50 = 31 ± 10 nm).
4
Inhibition of fMet-Leu-Phe-stimulated IP3 formation required concentrations almost 10 times higher (IC50 = 250 ± 130 nm).
5
Surprisingly, demethoxyviridin only inhibited fMet-Leu-Phe-induced intracellular calcium mobilization at concentrations 100 times greater than those needed to block IP3 formation.
6
Demethoxyviridin also inhibited PLD activation induced by sodium fluoride or phorbol myristate acetate (PMA) but the concentrations required were 100 times those needed to block fMet-Leu-Phe-stimulated PLD.
7
These observations support the contention that PLD plays an important role in signal transduction in the human neutrophil and indicate that wortmannin and demethoxyviridin inhibit PLD activation at a common step in the signalling pathway.
8
Furthermore, these results suggest that demethoxyviridin may block the interaction between the chemotactic peptide receptor and a GTP-binding protein that is intimately involved in PLD activation.
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