A human erythroleukemia cell line synthesizes a functionally active glycoprotein IIb-IIIa complex capable of binding fibrinogen.
The human erythroleukemia (HEL) cell line is known to express a number of platelet-megakaryocyte markers, including glycoproteins IIb and IIIa. Using [35S]methionine as well as monoclonal and polyclonal antibodies to glycoprotein IIb and IIIa, we have demonstrated synthesis of these two glycoproteins by this cell line. When Triton X-100-solubilized membranes were subjected to cross immunoelectrophoresis in 1% agarose, using a mixture of polyclonal antibodies to glycoproteins IIb and IIIa, a single peak was seen in the presence of Ca2+, whereas two distinct peaks were seen in the presence of 5 mM EDTA. When these crossed immunoelectrophoresis were overlaid with 125I-labelled fibrinogen, binding of fibrinogen to the glycoprotein IIb and IIIa complex peak was observed. When either the electrophoresis or the subsequent overlay was done in the presence of 5 mM EDTA, no 125I-fibrinogen binding was observed. These studies demonstrate that HEL cells contain glycoproteins IIb and IIIa capable of forming a Ca2+-dependent complex and capable of binding fibrinogen in a Ca2+-dependent reaction. Nevertheless, glycoprotein IIb- and IIIa-specific fibrinogen binding, of the type observed in platelets, could not be demonstrated in 'resting' or 'stimulated' intact HEL cells. The mechanism giving rise to this difference is currently unknown.
Thiagarajan
P
P
Shapiro
S S
SS
Sweterlitsch
L
L
McCord
S
S
D000906:Antibodies; D000911:Antibodies, Monoclonal; D001792:Blood Platelets / Q000378:metabolism; D002460:Cell Line; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D007123:Immunoelectrophoresis, Two-Dimensional; D007700:Kinetics; D004915:Leukemia, Erythroblastic, Acute; D010980:Platelet Membrane Glycoproteins / Q000096:biosynthesis* / Q000378:metabolism; D011485:Protein Binding
D000906:Antibodies; D000911:Antibodies, Monoclonal; D010980:Platelet Membrane Glycoproteins; D005340:Fibrinogen