期刊
CYTOKINE
卷 12, 期 7, 页码 835-844出版社
W B SAUNDERS CO
DOI: 10.1006/cyto.1999.0654
关键词
CD34 cells; c-mpl; megakaryocyte; platelet; thrombopoietin
资金
- NHLBI NIH HHS [HL54838, HL61222] Funding Source: Medline
- NIDDK NIH HHS [DK02448] Funding Source: Medline
The thrombopoietin receptor, c-mpl, is a crucial element not only in thrombopoietin (TPO)-initiated signaling pathways but also in the regulation of the circulating amount of TPO, We have identified a new c-mpl isoform, called c-mpl-del, that lacks 72 bp (24 amino acids) in the extracellular region of c-mpl and arises as a consequence of alternative RNA splicing between exons 8 and 9, c-mpl-del is expressed along with c-mpl-wt in blood mononuclear cells, CD34(+) cells, megakaryocytes, and platelets prepared from either normal donors or ET patients, although its relative expression appears to increase with megakaryocyte differentiation. The c-mpl-del-transfected cells expressed greater amounts of c-mpl-del RNA and protein than the comparable c-mpl-wt-transfected cells, however flow cytometry analysis could not detect any c-mpl receptor on the surface of the c-mpl-del-transfected cells. Further evidence for the absence of surface c-mpl-del was that in contrast to cells transfected with c-mpl-wt, those transfected with c-mpl-del did not grow in response to TPO, failed to undergo tyrosine phosphorylation of TPO-specific signal molecules, and did not bind I-125-rHuTPO. Taken together, these results demonstrate that c-mpl-del, a naturally occurring variant of c-mpl, fails to be incorporated into the cell membrane but might serve as a mechanism to decrease the overall expression of functional c-mpl late in megakaryocyte differentiation. (C) 2000 Academic Press.
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