Granulocyte-macrophage colony-stimulating factor (GM-CSF) reduces the density of stem cell factor receptors (c-kit oncogene product) on a GM-CSF-dependent human myeloid cell line.
By employing a monoclonal antibody against the stem cell factor receptor (SCF-R), c-kit oncogene product, we analysed in flow cytometric technique the density of SCF-R on GM/SO cells which were incubated under various culture conditions. These experiments revealed that there is an inverse correlation between the SCF-R density on the cells and the doses of granulocyte-macrophage colony-stimulating factor (GM-CSF) in culture medium; the lower the dose, the higher the density of SCF-R on the cells. More detailed analyses showed that, in contrast to SCF which rapidly downregulates its own receptor, GM-CSF does not alter the measurable level of SCF-R in an exposition period of 60 minutes, which suggests that the internalization or shedding of the receptor is not the mechanism of action. Since the most striking difference regarding density of SCF-R between GM-CSF-treated and untreated cells was observed on day 2, the modulation of c-kit oncogene protein by GM-CSF likely occur prior to expression of protein onto the cell surface. In order to exclude the possibility that altered cell viability due to insufficient GM-CSF content in culture medium might be responsible for the increased SCF-R densities on GM-CSF-dependent cells, we subsequently generated a GM-CSF-independent subclone which still responded to GM-CSF as well as the dependent did. The experiments carried out with this subclone confirmed the results presented above. Thus our data suggest that GM-CSF is directly involved in the regulation of SCF receptor density on GM/SO cells.
Oez
S
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5. Medizinische Klinik, Klinikum der Stadt Nurnberg, Germany.
Hofmann-Wackersreuther
G
G
Birkmann
J
J
Smetak
M
M
Welte
K
K
Gallmeier
W M
WM
D000911:Antibodies, Monoclonal / Q000276:immunology; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D015536:Down-Regulation / Q000187:drug effects; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D016298:Hematopoietic Cell Growth Factors / Q000378:metabolism*; D006412:Hematopoietic Stem Cells / Q000187:drug effects*; D006801:Humans; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000276:immunology; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis* / Q000276:immunology; D016184:Receptors, Colony-Stimulating Factor / Q000096:biosynthesis* / Q000276:immunology; D011994:Recombinant Proteins / Q000494:pharmacology; D019089:Stem Cell Factor
D000911:Antibodies, Monoclonal; D016298:Hematopoietic Cell Growth Factors; D011518:Proto-Oncogene Proteins; D016184:Receptors, Colony-Stimulating Factor; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases