title: Platelet aggregation induced by the C-terminal peptide of thrombospondin-1 requires the docking protein LAT but is largely independent of alphaIIb/beta3.
abstract: Thrombospondin-1 (TSP1) is abundantly secreted during platelet activation and plays a role in irreversible platelet aggregation. A peptide derived from the C-terminal domain of TSP1, RFYVVMWK (RFY) can activate human platelets at least in part via its binding to integrin-associated protein. Although integrin-associated protein is known to physically interact with alphaIIb/beta3, we found that this major platelet integrin had only a partial implication in RFY-mediated platelet aggregation. Accordingly, RFY induced a significant Glanzmann type I thrombasthenic platelet aggregation. The alphaIIb/beta3-dependent part of platelet aggregation induced by RFY was mainly due to secreted ADP and thromboxane A2. In the absence of alphaIIb/beta3 and fibrinogen, RFY stimulated a rapid tyrosine phosphorylation of a set of proteins, including Syk, linker for activation of T cells (LAT) and phospholipase Cgamma2. This signaling pathway was critical for RFY-mediated platelet activation as revealed by the use of pharmacological inhibitors as well as LAT-deficient mouse platelets. Phosphoinositide 3-kinase activation was also required for RFY-mediated platelet aggregation. Our results unravel a new alphaIIb/beta3 and fibrinogen-independent mechanism for platelet aggregation in response to the active peptide from the C-terminal domain of TSP1.
authors.affiliation: INSERM, Unité 563, Centre de Physiopathologie Toulouse Purpan, Department of Oncogenesis and Cell Signaling in Hematopoetic Cells, Hôpital Purpan, Toulouse, France.
authors.forename: C
authors.initials: C
authors.lastname: Trumel
authors.forename: M
authors.initials: M
authors.lastname: Plantavid
authors.forename: S
authors.initials: S
authors.lastname: Lévy-Tolédano
authors.forename: A
authors.initials: A
authors.lastname: Ragab
authors.forename: J P
authors.initials: JP
authors.lastname: Caen
authors.forename: E
authors.initials: E
authors.lastname: Aguado
authors.forename: B
authors.initials: B
authors.lastname: Malissen
authors.forename: B
authors.initials: B
authors.lastname: Payrastre
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D004792:Enzyme Precursors / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051966:Phospholipase C gamma; D010750:Phosphoproteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects* / Q000502:physiology*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism; D000072377:Syk Kinase; D013915:Thrombasthenia / Q000097:blood; D019700:Thrombospondin 1 / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; C110810:LAT protein, human; C491734:Lat protein, mouse; D008565:Membrane Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D019700:Thrombospondin 1; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; D010738:Type C Phospholipases; D051966:Phospholipase C gamma