Glycoprotein Ic-IIa functions as an activation-independent fibronectin receptor on human platelets.
Soluble fibronectin binds specifically to glycoprotein (GP) IIb-IIIa on thrombin-activated platelets, and this binding is not observed with platelets of patients with Glanzmann's thrombasthenia (GT) which lack GPIIb-IIIa. Here we report that GT platelets retain the ability to interact with fibronectin-coated surfaces. Adhesion to fibronectin does not require platelet activation and is inhibited by soluble fibronectin, antibodies specific for fibronectin, peptides containing the sequence Arg-Gly-Asp and polyclonal antibodies specific for band 3 of the chicken embryo fibroblast fibronectin receptor (anti-band 3). Using anti-band 3, we have purified a second fibronectin receptor from human platelets, a heterodimer composed of glycoproteins previously designated GPIc and GPIIa. The GPIc-IIa complex is found on both GT and normal platelets and appears to be identical to the GP138 kD-GP160 kD complex recently immunopurified by Giancotti et al. (1986. Exp. Cell Res. 163:47-62) and by Sonnenberg et al. (1987. J. Biol. Chem. 268:10376-10383). In this report, we provide the first evidence that GPIc-IIa actually mediates adhesion of platelets to fibronectin-coated surfaces. GPIc-IIa thus represents a second functional fibronectin receptor, distinct from GPIIb-IIIa, that is largely responsible for the adhesion of nonactivated platelets to fibronectin-coated surfaces.
Piotrowicz
R S
RS
Blood Center of Southeastern Wisconsin, Milwaukee 53233.
Orchekowski
R P
RP
Nugent
D J
DJ
Yamada
K Y
KY
Kunicki
T J
TJ
D001791:Blood Platelet Disorders / Q000097:blood*; D001792:Blood Platelets / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D007118:Immunoassay; D010973:Platelet Adhesiveness; D010980:Platelet Membrane Glycoproteins / Q000502:physiology*; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic / Q000502:physiology*; D013915:Thrombasthenia / Q000097:blood*
D005353:Fibronectins; D010980:Platelet Membrane Glycoproteins; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic