Thrombopoietin, Recombinant, Rat, aa22-326 (MGDF, MK-CSF, THPO, Tpo)

Thrombopoietin (Tpo), is a key regulator of megakaryocytopoiesis and thrombopoiesis. It is principally produced in the liver and is bound and internalized by the receptor Tpo R/c-mpl. Defects in the Tpo-Tpo R signaling pathway are associated with a variety of platelet disorders (1-3). Mature rat Tpo shares 68% and 81% aa sequence homology with human and mouse Tpo, respectively (4). It is an 80-85kD protein that consists of an N-terminal domain with homology to Erythropoietin (Epo) and a C-terminal domain that contains multiple N­linked and O­linked glycosylation sites. Tpo promotes the differentiation, proliferation, and maturation of megakaryocytes (MK) and their progenitors (5-7). Several other cytokines can also promote these functions but only in cooperation with Tpo (8, 9). Notably, IL-3 independently induces MK development, although its effects are restricted to early in the MK lineage (8, 9). Tpo additionally promotes platelet production, aggregation, ECM adhesion, and activation (10-13). These actions, in combination with direct effects on cardiomyocytes, can aid in the recovery of heart function following myocardial infarction (14). Tpo is cleaved by platelet-derived thrombin following Arg191 within the C-terminal domain and subsequently at other sites upon extended digestion (15). The C-terminal domain is not required for binding to Tpo R or inducing MK growth and differentiation (6). Aside from its hematopoietic effects, Tpo is expressed in the brain where it promotes the apoptosis of hypoxia-sensitized neurons and inhibits neuronal differentiation by blocking NGF-induced signaling (16, 17). Source: Recombinant protein corresponding to aa22-326, Ser22-Ser326, from rat Thrombopoietin, NS0-derived. Molecular Weight: ~50-66kD, Endotoxin: <0.10EU/1ug (LAL method), Biological Activity: Measured in a cell proliferation assay using MO7e human megakaryocytic leukemic cells. Avanzi, G. et al. (1988) Br. J. Haematol. 69:359. The ED50 for this effect is 0.05-0.3ng/ml. Storage and Stability: Lyophilized powder may be stored at -20°C. Stable for 12 months at -20°C. Reconstitute with sterile ddH2O or PBS. Aliquot to avoid repeated freezing and thawing. Store at -20°C. Reconstituted product is stable for 12 months at -20°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.