Involvement of Phosphatidylinositol 4,5-Bisphosphate in Phosphatidylserine Exposure in Platelets: Use of a Permeant Phosphoinositide-Binding Peptide

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• 作者：Robert Bucki ; Paul A. Janmey ; Rolands Vegners ; Franç ; oise Giraud ; and Jean-Claude Sulpice
• 刊名：Biochemistry
• 出版年：2001
• 出版时间：December 25, 2001
• 年：2001
• 卷：40
• 期：51
• 页码：15752 - 15761
• 全文大小：179K
• 年卷期：v.40,no.51(December 25, 2001)
• ISSN：1520-4995

文摘

During platelet activation, phosphatidylserine (PS) exposure on the extracellular face of theplasma membrane is associated with increased procoagulant activity. PS externalization is generallyattributed to an increase in intracellular Ca²⁺. Various phospholipid transporters, such as specific scramblasesor proteins from the family of multidrug resistance proteins, and cofactors such as phosphatidylinositol4,5-bisphosphate (PIP₂) have been proposed to participate in this process. In this study, we used amembrane-permeant polycationic peptide (RhB-QRLFQVKGRR), derived from the PIP₂-binding site ofgelsolin (GS 160-169) and linked to rhodamine B, to investigate the role of PIP₂ in PS externalizationin whole platelets. The peptide penetrated rapidly into the platelets, specifically bound to PIP₂, and inducedPS exposure to a similar extent as thrombin or collagen, but independently of changes in intracellularCa²⁺ or phosphoinositide 3-kinase activity. A pretreatment of platelets with quercetin, an inhibitor ofphosphoinositide metabolism, drastically decreased PS exposure induced by agonists or peptide. In largeunilamellar vesicles (LUVs), the presence of PIP₂ was strictly required for the induction of scrambling ofNBD-labeled phospholipids (PC and PS) by the peptide. In inside-out vesicles from erythrocytes (IOVs),the peptide also induced redistribution of PC and PS. Our data suggest that, in intact platelets, PIP₂ actsas a target of polycationic effectors, including Ca²⁺, to promote PS exposure. The use of a membrane-permeant and fluorescent peptide which binds to PIP₂ is a promising tool to investigate the role of PIP₂in various cellular processes.