[Study on conformational changes of GP IIb/IIIa complex during platelet activation].
OBJECTIVE
To determine whether a conformational change in GPIIb/IIIa occurs during platelet activation.


METHODS
Epitopes on GPIIb/IIIa complex were labeled with McAbs to GPIIb (SZ-22) and GPIIIa (SZ-21) conjugated to either a donor fluorescein (FITC-labeled) or an acceptor (TR-labeled) chromophore. The FRET between platelet-bound FITC and TR was measured and calculated by flow cytometry during platelet activation induced by some agonists.


RESULTS
In unstimulated platelets, a small but consistent change of FRET (5.5%) was detected, regardless of which antibody served as FRET donor. Platelet activation resulted in an obvious increase in FRET, suggesting a significant change in the separation or orientation of the epitopes within GPIIb/IIIa. This kind of changes could also occur on removing the extracellular calcium, and was independent of receptor occupancy.


CONCLUSIONS
The increase in FRET can reflect the rearrangement of the chromophore-labeled McAbs bound to GPIIb/IIIa during platelet activation, and this kind of structural rearrangement subunits of GPIIb/IIIa complex subunits can induce fibrinogen receptor expression.
Peng
L
L
Institute of Hematology, CAMS and PUMC, Tianjin 300020.
Li
J
J
Wu
H
H
D005434:Flow Cytometry; D006801:Humans; D015539:Platelet Activation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000737:chemistry*; D011487:Protein Conformation
D019039:Platelet Glycoprotein GPIIb-IIIa Complex