Which platelet surface antigen acts as the receptor for fibrinogen?

Which platelet surface antigen acts as the receptor for fibrinogen?

• A. GPIb/V/IX
• B. GPIIb/IIIa
• C. GPIa/IIa
• D. GPIc/IIa

Answer: (B)

Fibrinogen acts as a bridge between activated platelets by binding to the receptor GPIIb/IIIa, the major integrin αIIbβ3 on the platelet surface. When platelets are activated, inside-out signaling converts GPIIb/IIIa to a high-affinity state, enabling fibrinogen to bind and crosslink adjacent platelets. This crosslinking is what drives platelet aggregation and the formation of the hemostatic plug. Other receptors have different roles—GPIb/IX/V binds von Willebrand factor to help platelets adhere to damaged endothelium, while GPIa/IIa binds collagen. The option GPIc/IIa is not the primary fibrinogen receptor.

Fibrinogen acts as a bridge between activated platelets by binding to the receptor GPIIb/IIIa, the major integrin αIIbβ3 on the platelet surface. When platelets are activated, inside-out signaling converts GPIIb/IIIa to a high-affinity state, enabling fibrinogen to bind and crosslink adjacent platelets. This crosslinking is what drives platelet aggregation and the formation of the hemostatic plug. Other receptors have different roles—GPIb/IX/V binds von Willebrand factor to help platelets adhere to damaged endothelium, while GPIa/IIa binds collagen. The option GPIc/IIa is not the primary fibrinogen receptor.