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BW755C or staurosporine inhibits collagen‐stimulated phosphoinositide phosphorylation in platelets
Author(s) -
Thomas Lisa M.,
Holub Bruce J.
Publication year - 1991
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02535615
Subject(s) - staurosporine , phosphorylation , platelet , chemistry , microbiology and biotechnology , clinical chemistry , biophysics , biochemistry , protein kinase c , medicine , biology
Stimulation of platelets by collagen results in increased formation of the polyphosphoinositides, phosphatidylinositol phosphate (PtdIns P ) and phosphatidylinositol bisphosphate (PtdIns P 2 ) through stimulation of phosphoinositide kinase activities. We investigated a possible regulatory role of endogenous thromboxane formation and protein kinase C (PKC) activation in the induction of phosphoinositide phosphorylation following collagen stimulation, as well as following stimulation by the thromboxane mimetic, U‐46619. Human platelets were prelabeled with [ 3 H]inositol and stimulated with collagen (2 μg/mL) or U‐46619 (1 μM), in the absence or presence of either the cyclo‐oxygenase/lipoxygenase inhibitor, BW755C, or staurosporine, a putative inhibitor or PKC. Collagen stimulation resulted in a time‐dependent increase in [ 3 Hinositol‐labeled PtdIns P and PtdIns P 2 which was completely inhibited in the presence of BW755C. Addition of U‐46619 to BW755C‐treated, collagen‐stimulated platelets restored the increased polyphosphoinositide formation. Stimulation of platelets with U‐46619 alone also resulted in increased formation of [ 3 H]PtdIns P and [ 3 H]PtdIns P 2 , but this was not affected by the presence of BW755C. These results suggest that the collagen‐induced activation of phosphoinositide kinases was dependent upon thromboxane formation, but that U‐46619‐induced phosphoinositide formation was rather independent of further thromboxane production. Pretreatment of platelets with staurosporine, prior to agonist addition, completely blocked the collagen‐stimulated rise in radiolabeled PtdIns P and the U‐46619‐induced PtdIns P and PtdIns P 2 generations, suggesting that protein kinase, possibly PKC, may play a role in the activation of phosphoinositide kinases by these agonists.