Thrombopoeitin (IPR003978)

Short name: Thrombopoeitin

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 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.