title: Glycoprotein IIb-IIIa and RGD(S) are not important for fibronectin-dependent platelet adhesion under flow conditions.
abstract: Previous studies have indicated that activated blood platelets interact with fibronectin through binding of fibronectin to the glycoprotein IIb-IIIa complex (GPIIb-IIIa). The cell attachment site of fibronectin with its crucial arg-gly-asp(-ser) [RGD(S)]sequence is involved in these bindings. We studied the importance of these interactions for the fibronectin dependence of platelet adhesion under flow conditions. An RGDS-containing hexapeptide (GRGDSP) was compared with a nonreactive control peptide (GRGESP). The GRGDSP-peptide inhibited thrombin-induced aggregation and adhesion under static conditions at 0.1 mmol/L. This concentration had no effect on platelet adhesion to nonfibrillar collagen type I in flow. GRGDSP at 1 mmol/L had a significant inhibitory effect at 1,500 s-1, but not at the lower shear rates of 800 and 300 s-1 where platelet adhesion is also fibronectin dependent. On the matrix of cultured human umbilical vein endothelial cells, 1 mmol/L GRGDSP had no effect on platelet adhesion. The relation between GPIIb-IIIa and fibronectin dependence was investigated with platelets of a patient with Glanzmann's thrombasthenia and monoclonal antibodies to GPIIb-IIIa using endothelial cell matrix (ECM) as a surface. Platelets of normal controls or a patient with Glanzmann's thrombasthenia showed a similar inhibition of adhesion in the presence of fibronectin-free plasma after the ECMs had been preincubated with antifibronectin F(ab')2 fragments. Incubation of platelets with anti-GPIIb-IIIa showed inhibition of platelet adhesion at high shear rates. Dependence on fibronectin for platelet adhesion was still observed even though separate experiments had shown that these anti-GPIIb-IIIa antibodies could block binding of radiolabeled fibronectin to thrombin-activated platelets. These data suggest the existence of another binding system for the interaction of platelets with fibronectin that may only appear when fibronectin is present on a surface.
authors.affiliation: Department of Hematology, University Hospital Utrecht, The Netherlands.
authors.forename: P F
authors.initials: PF
authors.lastname: Nievelstein
authors.forename: J J
authors.initials: JJ
authors.lastname: Sixma
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000502:physiology; D001667:Binding, Competitive; D001783:Blood Flow Velocity; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology; D005353:Fibronectins / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology*; D010973:Platelet Adhesiveness / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D010980:Platelet Membrane Glycoproteins / Q000276:immunology / Q000502:physiology*; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors; D013915:Thrombasthenia / Q000097:blood; D013917:Thrombin
chemical_list: D000911:Antibodies, Monoclonal; D005353:Fibronectins; D009842:Oligopeptides; D010975:Platelet Aggregation Inhibitors; D010980:Platelet Membrane Glycoproteins; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic; C049554:glycyl-arginyl-glycyl-aspartyl-serine; D013917:Thrombin