Lipid Products of Phosphoinositide 3-Kinase and Phosphatidylinositol 4′,5′-Bisphosphate Are Both Required for ADP-dependent Platelet Spreading

• Published in: The Journal of biological chemistry Vol. 273; no. 28; p. 17817
• Main Authors: Jean-Michel Heraud, Claire Racaud-Sultan, Daisy Gironcel, Corinne Albigès-Rizo, Thierry Giacomini, Séverine Roques, Véronique Martel, Monique Breton-Douillon, Bertrand Perret, Hugues Chap
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 10.07.1998
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.28.17817

We have shown previously that ADP released upon platelet adhesion mediated by α IIb β 3 integrin triggers accumulation of phosphatidylinositol 3′,4′-bisphosphate (PtdIns-3,4-P 2 ) (Gironcel, D., Racaud-Sultan, C., Payrastre, B., Haricot, M., Borchert, G., Kieffer, N., Breton, M., and Chap, H. (1996) FEBS Lett. 389, 253–256). ADP has also been involved in platelet spreading. Therefore, in order to study a possible role of phosphoinositide 3-kinase in platelet morphological changes following adhesion, human platelets were pretreated with specific phosphoinositide 3-kinase inhibitors LY294002 and wortmannin. Under conditions where PtdIns-3,4-P 2 synthesis was totally inhibited (25 μ m LY294002 or 100 n m wortmannin), platelets adhered to the fibrinogen matrix, extended pseudopodia, but did not spread. Moreover, addition of ADP to the medium did not reverse the inhibitory effects of phosphoinositide 3-kinase inhibitors on platelet spreading. Although synthetic dipalmitoyl PtdIns-3,4-P 2 and dipalmitoyl phosphatidylinositol 3′,4′,5′-trisphosphate restored only partially platelet spreading, phosphatidylinositol 4′,5′-bisphosphate (PtdIns-4,5-P 2 ) was able to trigger full spreading of wortmannin-treated adherent platelets. Following 32 P labeling of intact platelets, the recovery of [ 32 P]PtdIns-4,5-P 2 in anti-talin immunoprecipitates from adherent platelets was found to be decreased upon treatment by wortmannin. These results suggest that the lipid products of phosphoinositide 3-kinase are required but not sufficient for ADP-induced spreading of adherent platelets and that PtdIns-4,5-P 2 could be a downstream messenger of this signaling pathway.