The Role of Transmembrane Glycoproteins, Integrins and Serpentines in Platelet Adhesion and Activation

Abstract

Platelets are unique cells of human body: they lack nucleus, are rather small in size (1–2 μm) and involved in several physiological functions, including hemostasis, immunity and angiogenesis. Platelets play a key role in the initiation of thrombosis upon injury of the blood vessels of the arterial bed, in which blood flows with high shear rates are observed. According to the generally accepted concepts, the reaction of platelets to endothelial injury at local shear rates of more than 1000 s^–1 is the primary binding of the GPIb-IX-V receptor complex glycoproteins with von Willebrand factor, a large multimeric blood protein which can specifically bind to collagen fibers. For further performance of their functions, and first of all, for stable attachment to the injured surface, platelet has to be activated. There are more than ten types of receptors on the platelet membrane, which trigger several cascades of intracellular signaling that leads to the restructuring of the cytoskeleton, granule secretion and activation of integrins, which provide the ability of platelets to strong adhesion and aggregation. This review is focused on the biophysical aspects of the interaction of transmembrane glycoproteins and integrins with extracellular ligands, as well as modern ideas about the mechanisms of platelet activation that is necessary to stabilize their primary adhesion and aggregation.