title: The tyrosine phosphatase 1B regulates linker for activation of T-cell phosphorylation and platelet aggregation upon FcgammaRIIa cross-linking.
abstract: Human platelets express the receptor for immunoglobulin G, FcgammaRIIa, that triggers cell aggregation upon interaction with immune complexes. Here, we report that the rapid tyrosine phosphorylation of the Linker for Activation of T-cell (LAT) in human platelets stimulated by FcgammaRIIa cross-linking was followed by its complete dephosphorylation in an alphaIIb/beta3 integrin-dependent manner. Concomitant to LAT dephosphorylation, the protein tyrosine phosphatase 1B (PTP1B) was activated through a mechanism involving its proteolysis by calpains downstream of integrins. Both PTP1B and LAT were associated with the actin cytoskeleton complex formed during platelet aggregation. Moreover, phospho-LAT appeared as a good substrate of activated PTP1B in vitro and these two proteins interacted upon platelet activation by FcgammaRIIa cross-linking. The permeant substrate-trapping PTP1B (TAT-PTP1B D181A) partly inhibited LAT dephosphorylation in human platelets, strongly suggesting that this tyrosine phosphatase was involved in this regulatory pathway. Using a pharmacological inhibitor, we provide evidence that PTP1B activation and LAT dephosphorylation processes were required for irreversible platelet aggregation. Altogether, our results demonstrate that PTP1B plays an important role in the integrin-mediated dephosphorylation of LAT in human platelets and is involved in the control of irreversible aggregation upon FcgammaRIIa stimulation.
authors.affiliation: INSERM U563, Centre de Physiopathologie de Toulouse-Purpan, Institut Fédératif de Recherche 30, Universite Paul Sabatier, Hôpital Purpan, 31059 Toulouse Cedex, France.
authors.forename: Ashraf
authors.initials: A
authors.lastname: Ragab
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bodin
authors.forename: Cécile
authors.initials: C
authors.lastname: Viala
authors.forename: Hugues
authors.initials: H
authors.lastname: Chap
authors.forename: Bernard
authors.initials: B
authors.lastname: Payrastre
authors.forename: Jeannie
authors.initials: J
authors.lastname: Ragab-Thomas
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry* / Q000378:metabolism; D001792:Blood Platelets / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D003599:Cytoskeleton / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D010974:Platelet Aggregation; D011485:Protein Binding; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D017452:Receptors, IgG / Q000737:chemistry* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism*; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D003432:Cross-Linking Reagents; D018076:DNA, Complementary; C080568:Fc gamma receptor IIA; D016023:Integrins; D010455:Peptides; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D005982:Glutathione Transferase; C516607:PTPN1 protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases