title: Platelet interactions with fibronectin: divalent cation-independent platelet adhesion to the gelatin-binding domain of fibronectin.
abstract: Divalent cation-dependent platelet adhesion to fibronectin (FN) is mediated by the integrin receptors alpha 5 beta 1 (GP Ic-IIa) and alpha IIb beta 3 (GP IIb-IIIa), which recognize the RGD (Arg-Gly-Asp) sequence in the cell-binding domain. However, FN can also support divalent cation-independent platelet adhesion. To determine which domain of FN mediates divalent cation-independent adhesion, proteolysis with thermolysin and affinity chromatography were used to isolate the cell-binding, gelatin-binding, and heparin-binding domains of FN. Unactivated and thrombin-activated platelets adhered to intact FN and the 45-Kd gelatin-binding domain in the presence of either Ca2+ or EDTA. Platelet spreading was mediated only by the 105-Kd cell-binding domain and required divalent cations. The heparin-binding domains did not support platelet adhesion. Reduction of intrachain disulfide bonds or removal of carbohydrate side chains on the gelatin-binding domain did not alter the ability to support platelet adhesion. Divalent cation-independent adhesion to the 45-Kd gelatin-binding domain was not inhibited by RGDS (Arg-Gly-Asp-Ser) synthetic peptides or monoclonal antibodies (MoAbs) directed against known platelet receptors. We conclude that platelets can adhere but not spread on the gelatin-binding domain of FN by a novel divalent cation-independent mechanism.
authors: Department of Medicine, Washington University School of Medicine, St Louis, MO 63110.
authors: K J
authors: KJ
authors: Winters
authors: J J
authors: JJ
authors: Walsh
authors: B G
authors: BG
authors: Rubin
authors: S A
authors: SA
authors: Santoro
mesh_terms: D000595:Amino Acid Sequence; D002118:Calcium / Q000097:blood*; D002352:Carrier Proteins / Q000097:blood*; D002413:Cations, Divalent / Q000097:blood; D002450:Cell Communication; D004492:Edetic Acid / Q000494:pharmacology; D005353:Fibronectins / Q000097:blood*; D005780:Gelatin / Q000097:blood*; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000097:blood; D010973:Platelet Adhesiveness / Q000187:drug effects; D011485:Protein Binding
chemical_list: D002352:Carrier Proteins; D002413:Cations, Divalent; D005353:Fibronectins; D010446:Peptide Fragments; C033135:gelatin binding protein; D005780:Gelatin; D004492:Edetic Acid; D002118:Calcium