Signal transduction by the peptide which mimics the activity of thrombopoietin.

Thrombopoietin (TPO) plays a central role in megakaryopoiesis and platelet production. It is a ligand for c-mpl, which is a member of the hematopoietic receptor superfamily. We have recently identified several human c-mpl binding peptides which are distinct from TPO, from phage random peptide libraries. PK1M is one of these peptides and is an agonist of c-mpl which is TPO receptor. We show here that PK1M induces the tyrosine phosphorylation of the Janus kinase 2 (JAK2) and the activation of the signal transducer and activation of transcription 5 (STAT5) in TPO-dependent cells like TPO.