Thrombopoeitin (IPR003978)

Short name: Thrombopoeitin

Overlapping homologous superfamilies


Family relationships


Megakaryocytes are large cells found in the bone marrow that, upon maturation, fragment into platelets. The term thrombopoietin (TPO) was coined in 1958 to describe a possible humoral entity that stimulates megakaryocyte development into platelets. The discovery of a novel haemopoietic cytokine receptor encoded by the proto-oncogene c-mpl raised speculation that this was the receptor for thrombopoietin, and prompted a search for the endogenous ligand [PMID: 10377897]. The ligand was cloned and in vivo- administration of the recombinant protein to mice produced a 4-fold increase in circulating platelets. These results suggested that the c-mpl ligand was in fact thrombopoietin [PMID: 8202158].

More recent studies have shown that TPO is expressed in hepatocytes, the renal proximal tubules, muscle cells and stromal cells in haemopoietic organs [PMID: 10582337]. TPO is a 332-residue protein with a 2-domain structure. The domain at the N terminus is 153 amino acids long, shares similarity with erythropoietin and can itself stimulate megakaryopoiesis in vitro. A four- alpha-helical structure is predicted, which is typical of many haemopoietic regulators. The C-terminal domain is 179 amino acids long, is highly variable across species and is not required for the binding of c-mpl [PMID: 9417073].

GO terms

Biological Process

GO:0008283 cell population proliferation

Molecular Function

GO:0005125 cytokine activity

Cellular Component

GO:0005576 extracellular region

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.