Expression of platelet alpha-granule proteins in a human megakaryocytic leukemia cell line (CMK 11-5)
Hamamoto, K.; Ohga, S.; Nagano, T.; Kishimoto, Y.; Yasunaga, K.; Sato, T.
International Journal of Hematology 58(1-2): 105-112
1993
ISSN/ISBN: 0925-5710 PMID: 7693024 Document Number: 416711
We investigated the expression of three platelet alpha-granule proteins, thrombospondin (TSP), von Willebrand factor (vWF), and fibrinogen (Fbg), in a human megakaryocytic cell line (CMK 11-5) by immunocytochemical staining, using the alkaline phosphatase anti-alkaline phosphatase (APAAP) complex method and immunoelectron microscopy of ultrathin-frozen sections. CMK 11-5, established from a Down's syndrome patient with acute megakaryoblastic leukemia, has characteristics closely resembling those of normal megakaryocytes. Under basal conditions, TSP expression was observed in the alphagranules, whereas the other two proteins were not detected. When the cells were cultured with 12-o-tetradecanoylphorbol-13-acetate (TPA), the expression of TSP was enhanced and vWF was also detected, but not Fbg. Cells cultured in the presence of plasma for 24 h took up Fbg and stored it in their alphagranules. These findings suggest that TSP and vWF are synthesized by CMK 11-5 cells, with the former being produced more rapidly than the latter, whereas Fbg is endocytosed from the plasma.