title: Platelet interaction with CNBr peptides from type II collagen via integrin alpha2beta1.
abstract: Adhesion of blood platelets to fibrillar collagens plays a crucial role in haemostasis. Collagen type II is a homotrimeric member of the fibrillar collagen family, whose ability to interact with platelets has been poorly investigated. In this work, we analysed platelet adhesion to the whole collagen type II molecule, as well as to its CNBr peptides. We found that collagen type II is as efficient as collagen type I in supporting platelet adhesion. Platelet binding sites on collagen type II were identified in two different CNBr-derived peptides, CB8 and CB11. The ability of these peptides to support platelet adhesion required the triple helical conformation. Interaction of platelets with CB8 and CB11 peptides was totally dependent on the presence of Mg(2+) ions, and was completely inhibited by the anti-integrin alpha(2)beta(1) antibody P1E6. Upon adhesion to CB8 and CB11, a significant increase in intracellular protein tyrosine phosphorylation was observed. The pattern of tyrosine phosphorylated proteins in CB8- and CB11-adherent platelets was very similar to that observed in platelets adherent to the whole collagen molecule. By immunoprecipitation experiments, we identified two substrates that were tyrosine phosphorylated in adherent platelets as the tyrosine kinase Syk and the PLCgamma2 isozyme. By contrast, platelet adhesion to CB8 and CB11 did not promote tyrosine phosphorylation of FcR gamma-chain. Finally, we found that collagen type II, but not the CNBr-derived peptides, was able to induce cell aggregation associated to protein tyrosine phosphorylation when added to a platelet suspension. These results identify the CNBr peptides from collagen type II CB8 and CB11 as ligands for platelet integrin alpha(2)beta(1), and recognise their ability to support platelet adhesion and activation.
authors.affiliation: Department of Biochemistry, University of Pavia, Via Bassi 21, 27100, Pavia, Italy.
authors.forename: Gianni F
authors.initials: GF
authors.lastname: Guidetti
authors.forename: Fabio
authors.initials: F
authors.lastname: Greco
authors.forename: Alessandra
authors.initials: A
authors.lastname: Bertoni
authors.forename: Camilla
authors.initials: C
authors.lastname: Giudici
authors.forename: Manuela
authors.initials: M
authors.lastname: Viola
authors.forename: Ruggero
authors.initials: R
authors.lastname: Tenni
authors.forename: Enrica M
authors.initials: EM
authors.lastname: Tira
authors.forename: Cesare
authors.initials: C
authors.lastname: Balduini
authors.forename: Mauro
authors.initials: M
authors.lastname: Torti
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D002448:Cell Adhesion; D003094:Collagen / Q000378:metabolism; D024043:Collagen Type II / Q000378:metabolism*; D003488:Cyanogen Bromide / Q000737:chemistry; D006801:Humans; D038982:Integrin alpha2beta1 / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D015539:Platelet Activation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism
chemical_list: D003094:Collagen; D024043:Collagen Type II; D003488:Cyanogen Bromide; D038982:Integrin alpha2beta1; D008274:Magnesium; D010446:Peptide Fragments; D010455:Peptides; D011505:Protein-Tyrosine Kinases; C121769:COL2A1 protein, Bos taurus