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Fc receptor-mediated platelet activation is dependent on phosphatidylinositol 3-kinase activation and involves

A Saci1, S Pain, F Rendu

  • 1INSERM U428, Faculté de Pharmacie, Université Paris-V, 75270 Paris, France.

The Journal of Biological Chemistry
|January 16, 1999
PubMed

Insights

Platelet activation via FcgammaRIIa involves adaptor protein Cbl and PI 3-kinase. Cbl recruits PI 3-kinase, crucial for FcgammaRIIa-mediated platelet aggregation and serotonin release.

Area of Science:

  • Immunology
  • Cell Biology
  • Hematology

Background:

  • Platelet activation by Fc gamma-chain receptors (FcgammaRIIa) initiates intracellular signaling via tyrosine phosphorylation.
  • The adaptor protein p120(cbl) (Cbl) is tyrosine-phosphorylated upon antibody-induced platelet activation.

Purpose of the Study:

  • To investigate the role of Cbl in FcgammaRIIa-mediated platelet signaling.
  • To elucidate the interaction between Cbl and phosphatidylinositol 3-kinase (PI 3-K) in this pathway.

Main Methods:

  • Studied tyrosine phosphorylation of Cbl in activated platelets.
  • Investigated the association of Cbl with the p85 subunit of PI 3-K.
  • Utilized in vitro experiments to define the interaction domains between Cbl and p85/PI 3-K.
  • Assessed the effect of PI 3-K inhibition (wortmannin) on FcgammaRIIa-induced platelet responses.

Main Results:

  • Cbl tyrosine phosphorylation and its association with p85/PI 3-K were dependent on Fc receptor engagement.
  • The Src homology 3 domain of p85/PI 3-K and the proline-rich region of Cbl mediated their association.
  • PI 3-K inhibition blocked FcgammaRIIa-induced platelet aggregation and serotonin release, with partial inhibition of thrombin-induced responses.

Conclusions:

  • Cbl acts as an adaptor protein in FcgammaRIIa signaling, recruiting PI 3-K.
  • PI 3-K plays a critical role in initiating platelet responses downstream of FcgammaRIIa engagement.
  • Cbl may enhance PI 3-K activity, contributing to platelet signal transduction.

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