Differential expression of granulocyte-macrophage colony-stimulating factor and IL-3 receptor subunits on human CD34+ cells and leukemic cell lines.
Cytokines transduce their signals through specific receptors. Receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-3, and IL-5 share the common signal transducing subunit (beta c), whereas the alpha subunits function as specific ligand binding components. In this study we prepared specific mouse monoclonal antibodies against human GM-CSF receptor-alpha subunit (hGMR alpha) by immunizing mice with Ba/F3 cells transfected with hGMR alpha complementary DNA. Using these anti-hGMR alpha antibodies in combination with antibodies against IL-3 receptor-alpha (IL-3R alpha), beta c subunits, and c-kit, we examined expression patterns and modulation of these receptor subunits on several human hematopoietic cells, including CD34+ cells and leukemic cell lines. GMR alpha and IL-3R alpha were expressed on GM-CSF- and IL-3-responsive cell lines, such as TF-1 and UT-7, whereas the expression levels were much lower on UT-7E, a GM-CSF- and IL-3-unresponsive subline of UT-7. The GMR alpha subunit was expressed only on mature granulocytes and monocytes, and IL-3R alpha was expressed on monocytes but not on mature granulocytes, and none of these subunits were expressed on lymphocytes. For CD34+ cells, GMR alpha was expressed more abundantly on CD34+ CD33high cells than on CD34+ CD33low cells, whereas IL-3R alpha was expressed more abundantly on CD34+ CD33low cells than on CD34+ CD33high and CD34+ CD33neg cells. Slight but significant expression of the beta c subunit was detected on CD34+ cells. Expression of not only GMR alpha and IL-3R alpha subunits but also c-kit was specifically downregulated by 48-hour incubation with their respective ligands. Receptor transmodulation between GM-CSF, IL-3, and stem cell factor (or kit ligand) was not detected on CD34+ cells in 48-hour cultures. We also detected upregulation of these alpha subunits by IL-1 alpha and interferon-gamma on leukemic cell lines. Our study showed expression levels for each receptor subunit--including GMR, IL-3R, and c-kit on human bone marrow and peripheral blood cells and leukemic cell lines--and revealed differential regulation of the expression of the receptor subunits.
Department of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Japan.
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D016475:3T3 Cells / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000276:immunology; D000918:Antibody Specificity; D018952:Antigens, CD34 / Q000032:analysis*; D001853:Bone Marrow / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology; D015536:Down-Regulation; D006801:Humans; D007947:Leukemia, Megakaryoblastic, Acute / Q000378:metabolism*; D046911:Macromolecular Substances; D051379:Mice; D008807:Mice, Inbred BALB C; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis / Q000096:biosynthesis / Q000097:blood; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000032:analysis / Q000096:biosynthesis* / Q000378:metabolism; D016185:Receptors, Interleukin-3 / Q000032:analysis / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D000911:Antibodies, Monoclonal; D018952:Antigens, CD34; D016207:Cytokines; D046911:Macromolecular Substances; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D016185:Receptors, Interleukin-3; D019009:Proto-Oncogene Proteins c-kit