Thrombospondin

Thrombospondins are an evolutionary conserved, calcium-binding family (Adams JC et al. 2011) of multifunctional glycoproteins, of which 5 members (thrombospondin 1-5) are currently known.

TSP1 was first isolated from platelets stimulated with thrombin, hence the name 'thrombin-sensitive protein'. Thrombospondins are released from the alpha-granules of the thrombocytes, among others. They consist of 3 identical subunits connected by stable disulfide bridges.

TSP1 binds to several receptors, including CD36, CD47 and various integrins. It also binds to fibrinogen, fibronectin, heparin, to the histine-rich glycoprotein, as well as to plasmin and plasminogen (see Stenina-Adognravi O 2013).

TSP2 significantly influences the composition of the extracellular matrix, as well as the fibrillogenesis without being an integral part of collagen fibrils of the extracellular matrix.

Thrombospondins regulate the binding of plasmin to the extracellular matrix as well as to endothelial cells, platelets and macrophages. TSP1 influences angiogenesis and wound healing. A deficiency of TSP2 leads to increased angiogenesis (Calabro NE et al. 2014). Thrombospondins belong to the physiological inhibitors of fibrinolysis and are regulatively involved in cardiovascular homeostasis through their functional diversity.

1. Adams JC et al (2011) The thrombospondins. Cold Spring Harb Perspect Biol 3:a009712.
2. Calabro NE et al (2014) Thrombospondin-2 and extracellular matrix assembly. Biochim Biophys Acta 1840:2396-2402 Stenina-Adognravi O (2013) Thrombospondins: old players, new games. Curr Opin Lipidol 24:401-409.
3. Stenina-Adognravi O (2014) Invoking the power of thrombospondins: regulation ofthrombospondins expression. Matrix Biol 37:69-82.