protein_function: Released during platelet aggregation. Neutralizes theanticoagulant effect of heparin because it binds more strongly toheparin than to the chondroitin-4-sulfate chains of the carriermolecule. Chemotactic for neutrophils and monocytes. Inhibitsendothelial cell proliferation (By similarity)..
Platelet factor 4(PF4) is a small cytokine belonging to the CXC chemokine family that is also known as chemokine(C-X-C motif) ligand 4(CXCL4). The PF4 gene was localized on map to 4q12-q13. Chemokines play fundamental roles in the development, homeostasis, and function of the immune system, and they have effects on cells of the central nervous system as well as on endothelial cells involved in angiogenesis or angiostasis. Platelet factor-4 is a 70-amino acid protein that is released from the alpha-granules of activated platelets and binds with high affinity to heparin. Its major physiologic role appears to be neutralization of heparin-like molecules on the endothelial surface of blood vessels, thereby inhibiting local antithrombin III activity and promoting coagulation. As a strong chemoattractant for neutrophils and fibroblasts, PF4 probably has a role in inflammation and wound repair.