Structure and function of the glycoprotein Ib-IX-V complex.

Following injury to a blood vessel, platelets rapidly adhere to the site of exposed subendothelial matrix in the vessel wall, become activated, and secrete granule contents that will recruit and activate other platelets, which then aggregate at the site and seal the defect in the vessel wall. The clot that forms prevents further blood loss. This process can become deranged in diseased blood vessels, such as coronary arteries narrowed by atherosclerosis. Platelets will also adhere to these vessels when matrix components are exposed by plaque rupture, with potentially disastrous results. The platelet glycoprotein Ib-IX-V complex plays crucial roles in both of these processes by mediating platelet adhesion to sites of blood vessel injury and by participating in the thrombin induced aggregation of platelets. This adhesion receptor complex is unique in that it is the only one of its kind. In this review, we discuss recent developments in elucidating the structure, topography, and functions of this important receptor complex.