The organizing principle of the platelet glycoprotein Ib–IX–V complex

SummaryThe glycoprotein (GP)Ib–IX–V complex is the platelet receptor for von Willebrand factor and many other molecules that are critically involved in hemostasis and thrombosis. The lack of functional GPIb–IX–V complexes on the platelet surface is the cause of Bernard–Soulier syndrome, a rare hereditary bleeding disorder that is also associated with macrothrombocytopenia. GPIb–IX–V contains GPIbα, GPIbβ, GPIX and GPV subunits, all of which are type I transmembrane proteins containing leucine-rich repeat domains. Although all of the subunits were identified decades ago, not until recently did the mechanism of complex assembly begin to emerge from a systematic characterization of inter-subunit interactions. This review summarizes the forces driving the assembly of GPIb–IX–V, discusses their implications for the pathogenesis of Bernard–Soulier syndrome, and identifies questions that remain about the structure and organization of GPIb–IX–V. The glycoprotein (GP)Ib–IX–V complex is the platelet receptor for von Willebrand factor and many other molecules that are critically involved in hemostasis and thrombosis. The lack of functional GPIb–IX–V complexes on the platelet surface is the cause of Bernard–Soulier syndrome, a rare hereditary bleeding disorder that is also associated with macrothrombocytopenia. GPIb–IX–V contains GPIbα, GPIbβ, GPIX and GPV subunits, all of which are type I transmembrane proteins containing leucine-rich repeat domains. Although all of the subunits were identified decades ago, not until recently did the mechanism of complex assembly begin to emerge from a systematic characterization of inter-subunit interactions. This review summarizes the forces driving the assembly of GPIb–IX–V, discusses their implications for the pathogenesis of Bernard–Soulier syndrome, and identifies questions that remain about the structure and organization of GPIb–IX–V.