|Name||Thrombospondin - 1|
|Type Assay||Immuno Assay|
|Synonym||TSP-1, thrombospondins, THBS1|
Thrombospondin 1 is released from platelets in response to thrombin stimulation and is a transient component of the extracellular matrix of developing and repairing tissues. Thrombospondin is a high-molecular weight, heparin-binding glycoprotein constituent of human platelets. Functions for TSP-1 have been found in multiple biological processes including angiogenesis, apoptosis, activation of TGF-beta and immune regulation. As such, TSP-1 is designated a multifunctional protein. Ranging from 30-50 µg per 10^9 platelets, thrombospondin is one of the most abundant proteins in the platelet granule. Thrombospondin was initially termed "thrombin-sensitive protein" based upon its release by thrombin-activated platelets. Structurally, thrombospondin is a 450,000 Da glycoprotein consisting of three, identical, disulfide-linked polypeptide chains. The binding of thrombospondin to the surface of both resting and thrombin-activated platelets has been reported. A thrombospondin-specific membrane receptor has also been partially characterized. Functionally, platelet-derived thrombospondin may play a role in platelet adherence and aggregation.
Thrombospondin is not an exclusive product of platelets and megakaryoctes. The synthesis of thrombospondin by endothelial cells, fibroblasts, monocytes and macrophages, and osteoblasts has been reported. Thrombospondin is also an integral component of the basement membrane in a number of different tissues. Thrombospondin interacts with a variety of extracellular macromolecules including heparin, collagen, fibrinogen and fibronectin, plasminogen, plasminogen activator, and osteonectin. Through the collective efforts of a number of different investigators employing both peptide chemistry and cDNA analytical techniques, distinct heparin, Ca2+-ion, platelet, and protein binding domains within thrombospondin have been identified. Based upon its specific interactions with both cells and extracellular matrix components, thrombospondin has been hypothesized to be a member of a class of extracellular proteins which may modulate cell-matrix interactions.