title: A critical role of lipid rafts in the organization of a key FcgammaRIIa-mediated signaling pathway in human platelets.
abstract: The involvement of platelet FcgammaRIIa in heparin-associated thrombocytopenia (HIT) is now well established. However, the precise sequence of molecular events initiated by FcgammaRIIa cross-linking in platelets remains partly characterized. We investigated here the role of lipid rafts in the spatio-temporal organization of the FcgammaRIIa-dependent signaling events. Upon cross-linking, FcgammaRIIa relocated in rafts where the kinase Lyn and the adapter LAT were among the major phosphotyrosyl proteins. Upon stimulation by HIT sera, the second messenger phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P(3)) accumulated in rafts in a P(2)Y(12) adenosine diphosphate (ADP) receptor-dependent manner. PtdIns(3,4,5)P(3) was then essential to specifically recruit phospholipase Cgamma2 (PLCgamma2) to these membrane microdomains. Controlled disruption of rafts by methyl beta-cyclodextrin reversibly abolished PtdIns(3,4,5)P(3) production, PLC activation and platelet responses induced by FcgammaRIIa cross-linking without affecting the tyrosine phosphorylation events. This work demonstrates that platelet rafts are essential for the integration of a key signaling complex leading to the rapid production of PtdIns(3,4,5)P(3) and in turn PLCgamma2 activation during HIT.
authors.affiliation: INSERM U563, Centre de Physiopathologie de Toulouse Purpan, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bodin
authors.forename: Cécile
authors.initials: C
authors.lastname: Viala
authors.forename: Ashraf
authors.initials: A
authors.lastname: Ragab
authors.forename: Bernard
authors.initials: B
authors.lastname: Payrastre
mesh_terms: D015703:Antigens, CD / Q000502:physiology*; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D002784:Cholesterol / Q000502:physiology; D003094:Collagen / Q000502:physiology; D003505:Cyclodextrins / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D021962:Membrane Microdomains / Q000187:drug effects / Q000502:physiology*; D008565:Membrane Proteins; D018129:Phosphatidylinositol Phosphates / Q000096:biosynthesis; D051966:Phospholipase C gamma; D010766:Phosphorylation / Q000187:drug effects; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017452:Receptors, IgG / Q000502:physiology*; D018048:Receptors, Purinergic P2 / Q000502:physiology; D058925:Receptors, Purinergic P2Y12; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D010738:Type C Phospholipases / Q000502:physiology; D047392:beta-Cyclodextrins; D019061:src-Family Kinases / Q000502:physiology
chemical_list: D015703:Antigens, CD; D003505:Cyclodextrins; C080568:Fc gamma receptor IIA; D008565:Membrane Proteins; C548576:P2RY12 protein, human; D018129:Phosphatidylinositol Phosphates; D017452:Receptors, IgG; D018048:Receptors, Purinergic P2; D058925:Receptors, Purinergic P2Y12; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; C060974:phosphatidylinositol 3,4,5-triphosphate; D003094:Collagen; D002784:Cholesterol; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma