Integrin alpha-IIb
Integrin alpha-IIb (CD41), the ITGA2B gene product also called platelet glycoprotein IIb, is the megakaryocyte- and platelet-specific alpha subunit that heterodimerizes exclusively with beta-3 to form the fibrinogen receptor GP IIb/IIIa. The precursor is cleaved into disulfide-linked heavy and light chains, and the extracellular region presents a beta-propeller with an I-domain-like segment plus a thigh domain. Upon inside-out activation by talin and kindlin-3, the receptor switches to a high-affinity state that binds fibrinogen and von Willebrand factor, crosslinking platelets into aggregates as the final common pathway of thrombus formation. Loss-of-function mutations in ITGA2B cause Glanzmann thrombasthenia, while receptor antagonists such as abciximab inhibit arterial thrombosis.
