Endothelial cells synthesize a heterodimeric adhesion molecule. the vitronectin receptor (VnR). which is similar to the platelet glycoprotein (GP)llb/IlIa complex. The subunits of the endothelial VnR (VnRa and GPIIIa) have been studied for their ability to express alloantigens associated with platelet GPIIb and lIla. We previously showed that endothehal GPIIIa can express the platelet alloantig...

Glanzmann thrombasthenia is an autosomal recessive bleeding disorder characterized by a decrease or absence of functional platelet glycoprotein (GP) IIb-IIIa (alpha IIb beta 3) integrin receptors. Although thrombasthenia is a rare disorder, its occurrence is increased in some regions of the world where intracommunity marriage and consanguinity are commonplace, resulting in increased expression ...

A new mutation is described in the X-linked gene GATA1, resulting in macrothrombocytopenia and mild dyserythropoietic features but no marked anemia in a 4-generation family. The molecular basis for the observed phenotype is a substitution of glycine for aspartate in the strictly conserved codon 218 (D218G) of the amino-terminal zinc finger loop of the transcription factor GATA1. Zinc finger int...

Plasmin exposure modulates platelet aggregation responses, but a direct effect of plasmin on the platelet fibrinogen receptor, glycoprotein IIb/IIIa (GPIIb/IIIa), has never been conclusively shown in a plasma milieu. To examine this issue, we incubated platelets in platelet-rich plasma with plasmin and measured the effect of this treatment on platelet aggregation, fibrinogen binding, and the st...

Localization of epitopes for platelet-associated (PA) anti-GPIIb-IIIa (alpha(IIb)beta(3)) autoantibodies in chronic immune thrombocytopenic purpura remains elusive. Previous studies suggest that PA antibodies recognize the tertiary structure of intact glycoprotein (GP) IIb-IIIa. To localize their epitopes using antigen-capture enzyme-linked immunosorbent assay (ELISA), the reactivity of 34 PA a...

Platelets from a patient with a suspected case of posttransfusion purpura were subjected to alloantigen phenotyping and found to express the PlA1, but not the PlA2, allelic form of human platelet membrane glycoprotein (GP) IIIa on the platelet surface. However, genotyping showed unambiguously that the patient carried the genes for both of these GPIIa alleles. Based on these results, we postulat...

Platelet plasma membrane glycoproteins IIb (GPIIb) and IIIa (GPIIIa) form a Ca(2+)-dependent heterodimer. GPIIb/IIIa, which serves as the receptor for fibrinogen and other adhesive proteins at the surface of activated platelets. Using equilibrium dialysis measurements, it was established that both GPIIb and GPIIIa in solution have low-affinity Ca(2-)-binding sites (Kd0.2-0.3 mM), five in GPIIb ...