Bcakground

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 TpoR/c-Mpl. Defects in the Tpo–TpoR signaling pathway are associated with a variety of platelet disorders (1–3).

The 353 amino acid (aa) human Tpo precursor is cleaved to yield the 332 aa mature protein. Mature human Tpo shares approximately 70% aa sequence homology with mouse and rat Tpo. It is an 80–85 kDa protein that consists of an N-terminal domain with homology to erythropoietin (Epo) and a C-terminal domain that contains multiple N-linked and O-linked glycosylation sites (4, 5).

Tissue-specific alternative splicing of human Tpo generates multiple isoforms with internal deletions, insertions, and/or C-terminal substitutions (6). Tpo promotes the differentiation, proliferation, and maturation of MK and their progenitors (4, 5, 7). Several other cytokines can promote these functions as well, but only in cooperation with Tpo (8, 9). Notably, IL-3 independently induces MK development, although its effects are restricted to early stages in the MK lineage (8, 9).

Tpo additionally promotes platelet production, aggregation, extracellular matrix (ECM) adhesion, and activation (10, 13). It is cleaved by platelet-derived thrombin following Arg191 within the C-terminal domain and subsequently at other sites upon extended digestion (14). Full-length Tpo and shorter forms circulate in the plasma (4, 5). The C-terminal domain is not required for binding to TpoR or inducing MK growth and differentiation (5).

Reference

1. Deutsch, V.R. and A. Tomer (2006) Br. J. Haematol. 134:453.

2. Kaushansky, K. (2005) J. Clin. Invest. 115:3339.

3. Li, J. et al. (1999) Br. J. Haematol. 106:345.

4. Bartley, T.D. et al. (1994) Cell 77:1117.

5. de Sauvage, F.J. et al. (1994) Nature 369:533.

6. Marcucci, R. and M. Romano (2008) Biochim. Biophys. Acta 1782:427.

7. Kaushansky, K. et al. (1994) Nature 369:568.

8. Kaushansky, K. et al. (1995) Proc. Natl. Acad. Sci. 92:3234.

9. Broudy, V.C. et al. (1995), Blood 85:1719.

10. Lok, S.I. et al. (1994) Nature 369:565.

11. Chen, J. et al. (1995) Blood 86:4054.

12. Oda, A. et al. (1996) Blood 87:4664.

13. Van Os, E. et al. (2003) Br. J. Haematol. 121:482.

14. Kato, T. et al. (1997) Proc. Natl. Acad. Sci. 94:4669.

Specifications

Synonyms	Megakaryocyte colony-stimulating factor ; MGDFC-mpl ligand; MKCSF; THPO; Thrombopoietin; Tpo
Accession #	P40225
Source	Human embryonic kidney cell, HEK293-derived human Thrombopoietin/Tpo protein
Source	Ser22-Gly353
Predicted Moleucular weight	52.9 kDa

Components and Storage

Formulation	Solution protein
	Dissolved in sterile PBS buffer.
	This solution can be diluted into other aqueous buffers. Centrifuge the vial prior to opening.
Storage and Stability	Avoid repeated freeze-thaw cycles.
	It is recommended that the protein be aliquoted for optimal storage.
	12 months from date of receipt, -20 to -70 °C as supplied.
Shipping	Shipping with dry ice.

Quality

Purity	> 95%, determined by SDS-PAGE.
Endotoxin Level	<0.010 EU per 1 ug of the protein by the LAL method.
Activity	Measured in a cell proliferation assay using MO7e human megakaryocytic leukemic cells.
Activity	The EC50 for this effect is 0.3-2 ng/mL.

SDS-PAGE

Gel filtration

Bioactivity

Documents

Human TPO