Platelet Signaling in Primary Haemostasis and Arterial Thrombus Formation: Part 2

Platelet signal transduction is the focus of this review. While 'classic' platelet signaling through G protein-coupled receptors in response to fluid-phase agonists has been extensively studied, signaling mechanisms linking platelet adhesion receptors such as GPIb-IX-V, GPVI and α2β1 to the activation of αIIbβ3 are less well established. Moreover, 'non-haemostatic' pathways can also activate platelets in various settings, including platelet-immune or platelet-tumour cell interactions, platelet responses to neutrophil extracellular traps, or stimulation by microbial pathogens. Genetically determined integrin variants can modulate platelet function and increase thrombogenicity. A typical example is the Pro33 (HPA-1b) variant of αIIbβ3. Recent advances in the genotype-phenotype relation of this prothrombotic variant and its impact on outside-in signaling will be reviewed.