Identification of the fibrinogen receptor on human platelets by photoaffinity labeling

Fibrinogen binding to receptors on stimulated platelets is a prerequisite for platelet aggregation. In order to identify the platelet fibrinogen receptor, we modified fibrinogen with the photoreactive, heterobifunctional cross-linking reagent methyl 4-azidobenzoimidate (MABI). MABI-fibrinogen was fu...

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Bibliographic Details
Published in:The Journal of biological chemistry 1982-07, Vol.257 (14), p.8049-8054
Main Authors: Bennett, J S, Vilaire, G, Cines, D B
Format: Article
Language:English
Subjects:
Affinity Labels - pharmacology
Azides
Blood Platelets - metabolism
Cell Membrane - metabolism
Fibrinogen - metabolism
Humans
Imidoesters - pharmacology
Immune Sera
Molecular Weight
Platelet Membrane Glycoproteins
Receptors, Cell Surface - drug effects
Receptors, Cell Surface - isolation & purification
Receptors, Cell Surface - metabolism
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Summary:Fibrinogen binding to receptors on stimulated platelets is a prerequisite for platelet aggregation. In order to identify the platelet fibrinogen receptor, we modified fibrinogen with the photoreactive, heterobifunctional cross-linking reagent methyl 4-azidobenzoimidate (MABI). MABI-fibrinogen was fully clottable and able to support platelet aggregation. To photoaffinity label the fibrinogen receptor, gel-filtered human platelets were incubated at 37 degrees C in the dark with 200 micrograms/ml of MABI-fibrinogen, 10 microM ADP, and 0.5 mM calcium. Irradiation of these platelets with ultraviolet light resulted in the incorporation of MABI-fibrinogen into the platelet surface. Incorporation could be prevented by excess native fibrinogen suggesting that MABI-fibrinogen had interacted with the fibrinogen receptor before photolysis. Examination of the irradiated platelets by sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the photoactivated MABI-fibrinogen had been incorporated into a 105,000 molecular weight membrane polypeptide that also contained the PlA1 antigen. Thus, this polypeptide has the characteristics of the membrane glycoprotein IIIa. Previous studies have shown that thrombasthenic platelets lack this glycoprotein and fail to bind fibrinogen after stimulation by ADP. Consequently, our data suggest that glycoprotein IIIa constitutes at least one component of the platelet fibrinogen receptor.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(18)34295-9