Platelet signaling–A primer

Objective To review the receptors and signal transduction pathways involved in platelet plug formation and to highlight links between platelets, leukocytes, endothelium, and the coagulation system. Data Sources Original studies, review articles, and book chapters in the human and veterinary medical fields. Data Synthesis Platelets express numerous surface receptors. Critical among these are glycoprotein VI , the glycoprotein Ib ‐ IX ‐ V complex, integrin α IIb β 3 , and the G ‐protein‐coupled receptors for thrombin, ADP , and thromboxane. Activation of these receptors leads to various important functional events, in particular activation of the principal adhesion receptor α IIb β 3 . Integrin activation allows binding of ligands such as fibrinogen, mediating platelet‐platelet interaction in the process of aggregation. Signals activated by these receptors also couple to 3 other important functional events, secretion of granule contents, change in cell shape through cytoskeletal rearrangement, and procoagulant membrane expression. These processes generate a stable thrombus to limit blood loss and promote restoration of endothelial integrity. Conclusions Improvements in our understanding of how platelets operate through their signaling networks are critical for diagnosis of unusual primary hemostatic disorders and for rational antithrombotic drug design.