Glycoprotein IIb-IIIa and RGD(S) are not important for fibronectin-
dependent platelet adhesion under flow conditions
PF Nievelstein and JJ Sixma
Department of Hematology, University Hospital Utrecht, The Netherlands.
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.
Volume 72,
Issue 1,
pp. 82-88,
07/01/1988
Copyright © 1988 by The American Society of Hematology
