Inhibition of tyrosine phosphorylation by wortmannin in human neutrophils. Dissociation from its inhibitory effects on phospholipase D.
BACKGROUND
Recent studies have indicated that the regulation of the activation of human neutrophils depends on tyrosine phosphorylation and on phospholipase D. Furthermore, a tentative causal relationship between these two signalling pathways has been indirectly implied derived through the use of inhibitors of tyrosine kinases. The fungal metabolite, wortmannin is at present the only compound known to inhibit the receptor-mediated activation of phospholipase D in human neutrophils. Its mechanism of action is presently unknown.


METHODS
The ability of peripheral blood neutrophils to respond to various agonists with an increase in activity of phospholipase D and an enhancement of tyrosine phosphorylation in the absence or presence of wortmannin was monitored.


RESULTS
Wortmannin was found to inhibit the stimulation of tyrosine phosphorylation by fMet-Leu-Phe, and by the inflammatory microcrystals monosodium urate and calcium pyrophosphate dihydrate. This effect of wortmannin was not secondary to inhibition of phospholipase D as U73122, a previously described phospholipase C inhibitor, was also found to inhibit phospholipase D without affecting tyrosine phosphorylation.


CONCLUSIONS
The results make it likely that one of the earliest sites of action of wortmannin in human neutrophils is at the level of tyrosine phosphorylation which then exerts a modulatory influence on the activation of phospholipase D.
Naccache
P H
PH
Centre de Recherche en Inflammation, Immunologie et Rhumatologie, Centre de Recherche du CHUL, Ste-Foy, Québec, Canaca.
Caon
A C
AC
Gilbert
C
C
Gaudry
M
M
Roberge
C J
CJ
Poubelle
P E
PE
Bourgoin
S
S
D000730:Androstadienes / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004963:Estrenes / Q000494:pharmacology; D006801:Humans; D009504:Neutrophils / Q000378:metabolism*; D010739:Phospholipase D / Q000037:antagonists & inhibitors*; D010766:Phosphorylation / Q000187:drug effects; D011760:Pyrrolidinones / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D014443:Tyrosine / Q000037:antagonists & inhibitors*; D000077191:Wortmannin
D000730:Androstadienes; D004963:Estrenes; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D014443:Tyrosine; D010738:Type C Phospholipases; D010739:Phospholipase D; D002118:Calcium; D000077191:Wortmannin