Calpains are involved in phosphatidylinositol 3',4'-bisphosphate synthesis dependent on the alpha IIb beta 3 integrin engagement in thrombin-stimulated platelets
- PMID: 9074630
- DOI: 10.1016/s0014-5793(97)00079-3
Calpains are involved in phosphatidylinositol 3',4'-bisphosphate synthesis dependent on the alpha IIb beta 3 integrin engagement in thrombin-stimulated platelets
Abstract
In thrombin-stimulated platelets alpha IIb beta 3 integrin engagement triggers both phosphatidylinositol 3',4'-bisphosphate synthesis and calpain activation. We checked the possible involvement of calpains in phosphatidylinositol 3-kinase signalling pathway using a cell permeant specific inhibitor of calpains, calpeptin. In conditions where thrombin-induced platelet aggregation and secretion were not impaired, we found a dose-dependent inhibition of phosphatidylinositol 3,4-bisphosphate synthesis by calpeptin from 50 micrograms/ml. Moreover, pretreatment of platelets by both calpeptin and the peptide RGDS, an inhibitor of fibrinogen binding to activated alpha IIb beta 3 integrin, did not induce additive effects on phosphatidylinositol 3,4-bisphosphate inhibition. Finally, the p85 regulatory subunit of phosphatidylinositol 3-kinase was still translocated to the cytoskeleton in calpeptin-treated platelets. These data indicate that calpains are involved in the regulation of alpha IIb beta 3 integrin-dependent phosphatidylinositol 3-kinase signalling pathway.
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