title: Evidence of a role for SHP-1 in platelet activation by the collagen receptor glycoprotein VI.
abstract: The Src homology (SH)2 domain-containing protein-tyrosine phosphatase SHP-1 is tyrosine phosphorylated in platelets in response to the glycoprotein VI (GPVI)-selective agonist collagen-related peptide (CRP), collagen, and thrombin. Two major unidentified tyrosine-phosphorylated bands of 28 and 32 kDa and a minor band of 130 kDa coprecipitate with SHP-1 in response to all three agonists. Additionally, tyrosine-phosphorylated proteins of 50-55 and 70 kDa specifically associate with SHP-1 following stimulation by CRP and collagen. The tyrosine kinases Lyn, which exists as a 53 and 56-kDa doublet, and Syk were identified as major components of these bands, respectively. Kinase assays on SHP-1 immunoprecipitates performed in the presence of the Src family kinase inhibitor PP1 confirmed the presence of a Src kinase in CRP- but not thrombin-stimulated cells. Lyn, Syk, and SLP-76, along with tyrosine-phosphorylated 28-, 32-, and 130-kDa proteins, bound selectively to a glutathione S-transferase protein encoding the SH2 domains of SHP-1, suggesting that this is the major site of interaction. Platelets isolated from motheaten viable mice (mev/mev) revealed the presence of a heavily tyrosine-phosphorylated 26-kDa protein that was not found in wild-type platelets. CRP-stimulated mev/mev platelets manifested hypophosphorylation of Syk and Lyn and reduced P-selectin expression relative to controls. These observations provide evidence of a functional role for SHP-1 in platelet activation by GPVI.
authors.affiliation: Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom.
authors.forename: J M
authors.initials: JM
authors.lastname: Pasquet
authors.forename: L
authors.initials: L
authors.lastname: Quek
authors.forename: S
authors.initials: S
authors.lastname: Pasquet
authors.forename: A
authors.initials: A
authors.lastname: Poole
authors.forename: J R
authors.initials: JR
authors.lastname: Matthews
authors.forename: C
authors.initials: C
authors.lastname: Lowell
authors.forename: S P
authors.initials: SP
authors.lastname: Watson
mesh_terms: D002118:Calcium / Q000502:physiology; D003094:Collagen / Q000494:pharmacology; D006801:Humans; D016023:Integrins / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D010766:Phosphorylation; D015539:Platelet Activation; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D038981:Receptors, Collagen; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains; D019061:src-Family Kinases / Q000502:physiology
chemical_list: D016023:Integrins; D047908:Intracellular Signaling Peptides and Proteins; D038981:Receptors, Collagen; D014443:Tyrosine; D003094:Collagen; D019061:src-Family Kinases; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D002118:Calcium