Platelet adhesion to collagen in individuals lacking glycoprotein IV.
The Naka isoantigen is expressed on glycoprotein (GP) IV (CD36), a platelet membrane GP that has been identified as having a role in platelet interactions with collagen and thrombospondin and in binding Plasmodium falciparum-infected erythrocytes to endothelial cells and melanoma cells. We have studied normal platelets and Naka- platelets from two Japanese donors that have 1% of GPIV by concentration-dependent antibody binding and flow cytometry. We studied the adherence of normal and Naka- platelets to types I, III, and IV collagen in static and to type I collagen in flowing systems at high shear force. We have also studied aggregation of normal and Naka- platelets to type I collagen. Naka- platelets showed normal or increased aggregation to type I collagen and normal adhesion to types I, III, and IV collagen in the presence of Mg++ or EDTA. Platelet aggregation and adhesion were inhibited by the anti-alpha 2 beta 1 antibody 176D7 to the same extent in Naka- as in normal platelets. We also studied endogenous thrombospondin surface expression and found that thrombin-stimulated Naka- platelets expressed the same amount of thrombospondin as did normal platelets. From our studies with Naka- platelets, we cannot identify a definitive role for GPIV in platelet aggregation, in adhesion to types I, III, and IV collagen, or in endogenous thrombospondin binding to platelets.
McKeown
L
L
Hematology Service, National Institutes of Health, Bethesda, MD 20892.
Vail
M
M
Williams
S
S
Kramer
W
W
Hansmann
K
K
Gralnick
H
H
D015703:Antigens, CD / Q000502:physiology*; D001792:Blood Platelets / Q000276:immunology; D018955:CD36 Antigens; D003094:Collagen / Q000502:physiology*; D006801:Humans; D007519:Isoantigens / Q000032:analysis; D008562:Membrane Glycoproteins / Q000032:analysis; D010973:Platelet Adhesiveness; D010980:Platelet Membrane Glycoproteins / Q000172:deficiency / Q000502:physiology*; D019699:Thrombospondins
D015703:Antigens, CD; D018955:CD36 Antigens; D007519:Isoantigens; D008562:Membrane Glycoproteins; D010980:Platelet Membrane Glycoproteins; D019699:Thrombospondins; D003094:Collagen