| Primary Identifier | IPR003978 | Type | Family |
| Short Name | Thrombopoietin |
| description | Megakaryocytes are large cells found in the bone marrow that, uponmaturation, fragment into platelets. The term thrombopoietin (TPO) wascoined in 1958 to describe a possible humoral entity that stimulatesmegakaryocyte development into platelets. The discovery of a novelhaemopoietic cytokine receptor encoded by the proto-oncogene c-mpl raisedspeculation that this was the receptor for thrombopoietin, and prompted asearch for the endogenous ligand []. The ligand was cloned and in vivo-administration of the recombinant protein to mice produced a 4-fold increasein circulating platelets. These results suggested that the c-mpl ligand wasin fact thrombopoietin [].More recent studies have shown that TPO is expressed in hepatocytes, therenal proximal tubules, muscle cells and stromal cells in haemopoieticorgans []. TPO is a 332-residue protein with a 2-domain structure. Thedomain at the N terminus is 153 amino acids long, shares similarity witherythropoietin and can itself stimulate megakaryopoiesis in vitro. A four-α-helical structure is predicted, which is typical of many haemopoieticregulators. The C-terminal domain is 179 amino acids long, is highly variable across species and is not required for the binding of c-mpl []. |
