Carrier protein for platelet (but not plasma) factor V/Va. Plays a role in the storage and stabilization of factor V in platelets. Upon release following platelet activation, may limit platelet and plasma factor Va-dependent thrombin generation. Ligand for integrin alpha-IIb/beta-3 and integrin alpha-V/beta-3 on activated platelets, and may function as an extracellular matrix or adhesive protein.
Subcellular locations: Secreted
Synthesized by endothelial cells and megakaryocytes. Stored in platelet alpha granules and endothelial cell Weibel-Palade bodies, following activation of these cells, it is released and attached to megakaryocytes, platelets, endothelium and subendothelium of blood vessels. Not found in plasma. Found in vascular tissues such as placenta, lung, and liver.