αIIbβ3

Integrin αIIbβ3 is a transmembrane glycoprotein highly expressed on platelets, mediating bidirectional signal transduction essential for hemostasis and thrombosis^[1][2]. Upon agonist stimulation, inside-out signaling converts αIIbβ3 from a low- to high-affinity state, allowing fibrinogen and other ligand binding, which subsequently triggers outside-in signaling for platelet spreading, aggregation, clot retraction, and thrombus consolidation^[1][2]. Mechanistically, αIIbβ3 outside-in signaling involves Src family kinases, PI3K/Akt, and Rap1b pathways, coordinating platelet activation and thromboxane production^[3][4]. Phosphatases, including PP1cα and PP2B-Aβ, modulate integrin-mediated signaling, where PP1cα amplifies agonist-induced signals but attenuates adhesion-mediated functions, and PP2B-Aβ suppresses outside-in αIIbβ3 activation^[5][6][7]. Compared with related integrins, αIIbβ3 possesses a unique extracellular safeguard that maintains an inactive state under physiological shear, preventing premature activation by hydrodynamic forces. Kindlins act as co-activators, supporting talin-dependent ligand binding without promoting initial talin recruitment, emphasizing isoform-specific regulatory mechanisms^[8]. Pharmacological and natural inhibitors, such as PPARγ agonists, glabridin, and disintegrins from hematophagous species, effectively modulate αIIbβ3 outside-in signaling, platelet aggregation, and thrombus formation, offering tools for experimental studies and therapeutic exploration^{[9][10][11][12]}. In disease models, αIIbβ3 mediates thrombus formation in venous thrombosis and contributes to platelet hyperactivation in Alzheimer’s disease via ROS and NADPH oxidase signaling^[13][14].

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